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Evaluation of the distribution and accumulation of species of Alicyclobacillus in the fruit concentrate processing environmentSteyn, Catharina Elizabeth 03 1900 (has links)
Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Alicyclobacillus species are thermo-acidophilic bacteria that produce highly resistant
endospores able to survive the processing temperatures of fruit concentrate
manufacturing, including evaporation and conventional pasteurisation (86 ° - 96 °C for
± 2 min). Alicyclobacillus endospores retain their viability in juice concentrates which,
under favourable conditions, could germinate and multiply to numbers high enough to
cause spoilage and product deterioration through the production of chemical taint
compounds. This thesis reports on the distribution of Alicyclobacillus in the fruit
concentrate processing environment and the effect of current manufacturing practices
on the accumulation of Alicyclobacillus in fruit concentrates. These practices include
the recirculation (recycling) of flume water as a means of water conservation, as well as
continuous process running times when facilities operate at full capacity. This thesis
also reports on the effect of fruit variety and skin type on the occurrence of
Alicyclobacillus in fruit concentrates.
Alicyclobacillus was monitored at nine processing stages of fruit concentrate
manufacturing during the functioning of either a recirculating or a one-pass
(not recirculated) flume water system. Significantly higher Alicyclobacillus levels were
recovered in fruit mash, single strength juice, concentrate and the final pasteurised
product (± 30 °Brix) during the functioning of a re circulating flume system, compared to
when a one-pass flume system was functional (P < 0.05). Irrespective of the flume
system, high Alicyclobacillus levels were recovered from the concentrate and
condensate water (a by-product of juice concentration) from the evaporator, which
makes this a point of concern during concentrate manufacturing. Manufacturing
practices such as the recirculation of flume water and the recovery of condensate water
for fruit washing purposes pose a potential risk of Alicyclobacillus contamination and
accumulation in fruit concentrates and the processing environment.
The effect of continuous process running times on Alicyclobacillus was monitored
in a facility that was operating at full capacity. Sampling occurred every 12 h at four
processing stages, during a processing tempo of 1.8 - 2.0 t h-1 for 108 h. Vegetative
cells increased significantly (P < 0.05) in single strength juice and condensate water
after 84 h of processing, with 3.15 and 3.85 log10 cfu mL-1 recovered, respectively.
Similar accumulation patterns of vegetative cells were observed in concentrate and the
final pasteurised product. Endospores in single strength juice, concentrate and the final
product were also the highest after 84 h of processing with 1.32, 1.59 and
1.64 log10 cfu mL-1, respectively. When fruit concentrate manufacturing facilities
process at full capacity, a restriction in the continuous process running time to under
84 h in between CIP procedures, along with good manufacturing practices, can
minimise Alicyclobacillus accumulation in fruit concentrates.
The effect of fruit skin type, specifically hairy-skinned stone fruits (peach and
apricot) and smooth-skinned pome fruits (apple and pear) on the occurrence of
Alicyclobacillus in concentrates were examined. Apple concentrate samples had the
highest occurrence (average %) of vegetative Alicyclobacillus cells (50%), followed by
apricot (40%), peach (15%) and pear (10%) concentrates. The occurrence of
Alicyclobacillus endospores in fruit concentrate samples were also the highest in apple
(50%), followed by pear (25%), apricot (20%), and peach (10%) concentrates. The
occurrence of Alicyclobacillus vegetative cells and endospores did not differ significantly
(P > 0.05) between concentrates from hairy-skin and smooth-skin fruit varieties. Thus it
was concluded that fruit washing steps prior to processing was more critical for the
control of Alicyclobacillus than the type of fruit skin being processed. / AFRIKAANSE OPSOMMING: Alicyclobacillus spesies is termo-asidofiliese bakterieë wat hoogs bestande endospore
produseer met die vermoë om prosesseringstemperature, insluitend verdamping en
konvensionele pasteurisasie temperature (86 ° - 96 °C vir ± 2 min), tydens die
vervaardiging van vrugtekonsentraat te oorleef. Alicyclobacillus endospore behou hul
lewensvatbaarheid in vrugtekonsentrate en kan in gunstige toestande ontkiem en
vermeerder tot getalle wat wansmake in produkte kan veroorsaak weens die produksie
van chemiese verbindings. Hierdie tesis doen verslag oor die verspreiding van
Alicyclobacillus in die vrugtekosentraat prosesseringsomgewing en oor die effek van
huidige produksie praktyke op die akkumulasie van Alicyclobacillus in
vrugtekonsentrate. Die praktyke sluit in, die hersirkulering van leigeut (transport) water
as ‘n wyse van waterbesparing, asook aaneenlopende prosesseringstye wanneer
vrugtekosentraat fabrieke teen ‘n volle kapasiteit prosesseer. Daar word ook verslag
gedoen oor die effek van verskillende vrug variëteite en vel tipes op die voorkoms van
Alicyclobacillus in vrugtekonsentrate.
Alicyclobacillus was gemonitor by nege verskillende stadiums van ‘n
vrugtekosentraat prosesseringsfabriek tydens die funksionering van óf 'n
hersirkulerende óf ‘n deurlopende (nie-hersirkulerende) leigeut waterstelsel.
Alicyclobacillus vlakke was beduidend hoër in gemaalde vrugte, enkelsterkte sap,
konsentraat en die finale gepasteuriseerde produk (± 30 °Brix), gedurende die
funksionering van 'n hersirkulerende leigeutstelsel, in vergelyking met die funksionering
van ‘n deurlopende leigeutstelsel (P < 0.05 ). Ongeag van die leigeutstelsel, is hoë
vlakke Alicyclobacillus gevind in konsentraat en kondensaat water ('n by-produk van die
sap konsentrasie porses) vanuit die verdamper, en maak dit dus ‘n punt van belang
tydens die vervaardiging van vrugtekonsentraat. Daar is gevind dat
vervaardigingspraktyke soos die hersirkulasie van leigeut water en die herwinnig van
kondensaat water moontlike risiko’s inhou vir die besoedeling en akkumulasie van
Alicyclobacillus in vrugtekosentrate en die prosesseringsomgewing.
Die effek van aaneenlopende prosesseringstye op Alicyclobacillus was
gemonitor in 'n vrugtekosentraat prosesseringsfabriek wat teen volle kapasiteit
prosesseer. Steekproefneming het elke 12 h by vier prosesseringsstadiums geskied,
tydens 'n prosesseringstempo van 1.8 - 2.0 t h-1 vir 108 h. Vegetatiewe selle het
beduidend toegeneem (P < 0.05) in die enkelsterkte sap en kondensaat water na 84 uur
van prosessering, met 3.15 en 3.85 log10 kve mL-1, onderskeidelik verhaal. Soortgelyke akkumulasiepatrone vir vegetatiewe selle was waargeneem in konsentraat en die finale
gepasteuriseerde produk. Endospore in enkelsterkte sap, konsentaat en die finale
produk was ook die hoogste na 84 uur van prosessering, met 1.32, 1.59 en
1.64 log10 kve mL-1, onderskeidelik. Wanneer vrugtekonsentraat fabrieke teen volle
kapasiteit prosesseseer, kan 'n beperking in aaneenlopende prosesseringstye tot onder
84 h tussen CIP prosedures, gepaard met goeie vervaardigingspraktyke, die
akkumulasie van Alicyclobacillus in vrugte konsentate verminder.
Die effek van verskillende vrug variëteite se vel tipes, spesifiek harige-vel
steenvrugte (perske en appelkoos) en gladde-vel kernvrugte (appel en peer) op die
voorkoms van Alicyclobacillus in vrugtekonsentrate was ondersoek. Appel konsentaat
monsters het die hoogste voorkoms van vegetatiewe Alicyclobacillus selle gehad
(gemiddelde %), met (50%), gevolg deur appelkoos (40%), perske (15%) en peer (10%)
konsentraat. Die voorkoms van Alicyclobacillus endospore in vrugte konsentraat
monsters was weer die hoogste in appel (50%), gevolg deur peer (25%), appelkoos
(20%), en perske (10%) konsentraat. Die voorkoms van Alicyclobacillus vegetatiewe
selle en endospore het nie betekenisvol tussen konsentrate van harige-vel en gladdevel
vrug variëteite verskil nie (P > 0.05). Die gevolgtrekking was dat vrugte wasstappe,
voor die prosessering van vrugtekonsentraat, van meer belang is vir die beheer van
Alicyclobacillus as die vel tipe van die vrug variëteit wat geprosesseer word.
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Identification of precursors present in fruit juice that lead to the production of guaiacol by Alicyclobacillus AcidoterrestrisVan der Merwe, Enette 03 1900 (has links)
Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Alicyclobacilli are endospore-forming, thermophilic, acidophilic bacteria (TAB) that survive the pasteurisation process and spoil acidic fruit juices through the production of the taint compound guaiacol. Guaiacol causes an undesirable odour with an unpleasant smoky, medicinal or phenolic-like taste. This thesis reports on the precursors, vanillin and vanillic acid metabolised to guaiacol by Alicyclobacillus spp. in fruit juice, the pathway of guaiacol production and the spoilage potential of contaminated fruit juices supplemented with these precursors.
A high performance liquid chromatography method with UV-diode array detection (HPLC-DAD) was developed for the simultaneous detection and quantification of guaiacol and its precursors. Alicyclobacillus acidoterrestris FB2 was incubated at 45 °C for 7 d in Bacillus acidoterrestris (BAT) broth supplemented with ferulic acid, vanillin or vanillic acid. The cell concentrations were determined every 24 h and the concentration of the precursors and the production of guaiacol was determined using HPLC-DAD. The guaiacol production was also determined using the peroxidase enzyme colourimetric assay (PECA). Alicyclobacillus acidoterrestris produced guaiacol from vanillin and vanillic acid, confirming both vanillin and vanillic acid as precursors for guaiacol production by A. acidoterrestris FB2. Furthermore, a metabolic pathway directly from vanillin to guaiacol was identified in this study. However, guaiacol was not produced by A. acidoterrestris FB2 in the samples supplemented with ferulic acid and it is, therefore, not considered a direct precursor for guaiacol production by A. acidoterrestris.
The spoilage potential of apple juice supplemented with either 10 mg L-1 or 100 mg L-1 vanillin or vanillic acid by A. acidoterrestris FB2 (106 cfu mL-1) was also evaluated. The production of guaiacol increased with the increase in vanillin or vanillic acid concentrations (in BAT broth and apple juice) indicating that the concentration of vanillin and vanillic acid present in fruit juice will influence the spoilage potential of the juice. Guaiacol concentrations in apple juice well above the best estimated threshold value of guaiacol for taste (0.24 – 2.00 μg L-1) and odour (0.50 - 2.32 μg L-1) was produced by A. acidoterrestris FB2 in the apple juice supplemented with 10 mg L-1 vanillin or vanillic acid. This indicates that fruit juice with a vanillin or vanillic acid concentration as low as 10 mg L-1 has the potential to spoil if the juice is contaminated with A. acidoterrestris.
The concentrations of vanillin and vanillic acid in different fruit juices can be used to indicate if a specific fruit juice is susceptible to guaiacol spoilage by Alicyclobacillus spp. In the development of juice products and different blends of fruit juices, special care must be taken not to concentrate the amount of vanillin and vanillic acid present in the fruit juices. / AFRIKAANSE OPSOMMING: Alicyclobacilli is endospoor-vormende, termofiliese, asidofiliese bacterie (TAB) wat die pasteurisasie proses oorleef en suur vrugtesappe bederf met die produksie van ‘n taint komponent guaiakol. Guaiakol veroorsaak ‘n ongewensde reuk en onaangename rookagtige, medisinale of fenoliese smaak. Hierdie tesis doen verslag oor die voorloper komponente, vanillien en vanilliensuur in vrugtesappe wat gemetaboliseer word na guaiakol deur Alicyclobacillus spesies, die padweg van guaiakol produksie en die bederfbaarheid van gekontamineerde vrugtesap aangevul met hierdie voorloper komponente.
‘n Hoëprestasie vloeistof chromatografie metode met UV-deteksie (skanderend) (HPVC) is ontwikkel vir die gesamentlike deteksie en kwantifisering van guaiakol en die voorloper komponente. Alicyclobacillus acidoterrestris FB2 is geïnkubeer by 45 °C vir 7 d in Bacillus acidoterrestris (BAT) medium aangevul met feruliensuur, vanillien of vanilliensuur. Die sel konsentrasies is elke 24 h bepaal en die aangevulde komponente en die geproduseerde guaiakol is bepaal deur van HPVC gebruik te maak. Die guaiakol konsentrasies is ook bepaal deur van die peroksidase ensiem kolorimetriese bepaling (PEKB) gebruik te maak. Alicyclobacillus acidoterrestris het guaiakol geproduseer vanaf vanillien en vanilliensuur, dus is beide vanillien en vanilliensuur bevestig as voorlopers van guaiakol produksie deur A. acidoterrestris FB2. A padweg direk van vanillien na guaiakol is in hierdie studie geïdentifiseer. Guaiakol is nie geproduseer deur A. acidoterrestris FB2 in the monsters wat met feruliensuur aangevul is nie en feruliensuur is dus nie ‘n direkte voorloper van guaiakol produksie deur A. acidoterrestris.
Die bederf potensiaal van appelsap aangevul met 10 mg L-1 of 100 mg L-1 vanillien of vanilliensuur deur A. acidoterrestris (106 kve mL-1) is ook geëvalueer. Die produksie van guaiakol het toegeneem met die toename in vanillien of vanilliensuur konsentrasies (in beide BAT en appelsap) wat aandui dat die konsentrasie vanillien en vanilliensuur teenwoordig in vrugtesap die bederfbaarheid van die sap sal beïvloed. Guaiakol konsentrasies in appelsap hoog bo die drumpel waardes van guaiacol vir smaak (0.24 – 2.00 μg L-1) en reuk (0.50 - 2.32 μg L-1) is geproduseer deur A. acidoterrestris FB2 in die appelsap monsters aangevul met 10 mg L-1 vanillien of vanilliensuur. Hierdie verskynsel dui aan dat vrugtesap met ‘n vanillien of vanilliensuur konsentrasies van so laag as 10 mg L-1 die potensiaal het om te bederf indien die sap gekontamineer is met A. acidoterrestris.
Die konsentrasies van vanillien en vanilliensuur in verskillende vrugtesappe kan gebruik word om aan te dui of ‘n spesifieke vrugtesap ‘n hoë risiko het vir guaiakol bederf deur Alicyclobacillus spesies. Tydens die ontwikkeling van vrugtesap produkte en verskillende mengsels van vrugtesappe moet seker gemaak word dat die hoeveelhede vanillien en vanilliensuur in die sappe nie gekonsentreer word nie.
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Evaluation of malted barley with different degrees of fermentability using the Rapid Visco Analyser (RVA)Visser, Magdalena Johanna 03 1900 (has links)
Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The relationship between malt fermentability and rheological variables, measured by means
of the Rapid Visco Analyser (RVA) and application of multivariate data analysis, was
investigated.
The RVA Kilned Malt method was optimised to achieve maximum rheological
discrimination between malt samples, differing in fermentability. Five concentrations and two
particle sizes were used to investigate each malt sample. Data were analysed by two
different data analysis techniques, namely principal component analysis (PCA) and analysis
of variance (ANOVA). Rheological variables for peak-height, -width, -area and time
occurrence, were able to discriminate between high (Metcalfe, Flagship), intermediate (SSG
585, PUMA) and low malt fermentability (SSG 506, SSG 564). Variation in particle size
showed insignificant (P>0.05) fermentability discrimination. The malt to water ratio of 1:1.5
provided the best discrimination in fermentability. PCA applied to the entire dataset was the
superior data analysis technique.
Partial least squares (PLS) regression and Soft Independent Modeling of Class Analogy
(SIMCA) were applied to predict malt fermentability. Recorded RVA data was regressed with
both apparent attenuation limit (AAL) and free amino nitrogen (FAN), independently.
Developed PLS calibration models were validated by test set and segmented crossvalidation
for AAL and FAN, respectively. The SIMCA classification model developed was
based on different malt fermentability classes, each PCA validated independently by test set
validation. A strong correlation between RVA analysis and AAL was obtained (r=0.92), while
FAN delivered a weak correlation (r=0.59). Regarding the SIMCA model; the proportion of
test set samples correctly classified in terms of malt fermentability was 83%. South African
malt blends were predicted to have low malt fermentability. Simulated blends were predicted
to have high fermentability when using a minimum of 80% Metcalfe blended with SSG 506.
Blends containing higher percentages of the low malt fermentability cultivar (SSG 506) were
predicted to have an overall intermediate fermentability.
Different experimental conditions were investigated during RVA analysis (i.e. instrument
model; time/temperature profile, enzyme activity and heating/cooling rate). Rheological
measurement using different RVA models gave similar PCA results, indicating adequate
sensitivity of the older instrument for discrimination purposes. Matching the time/temperature
profile used in the commercial brewery mashing process was rejected due to increased
analysis time and rheological noise while reducing fermentability discrimination. Inactivating
malt enzymes prior to RVA analysis provided useful sample information, such as the large
starch granule’s mean diameter, extract and starch content, by measuring peak height and
iv
time to peak. The amount of starch damage inflicted on a malt sample increased after
repeated centrifugal milling, but was unaffected by the sieve size used.
Multivariate data analysis is a suitable statistical technique applied to rheological data
and provided more relevant information than traditional univariate techniques. The RVA can
be considered an ideal instrument within a grain laboratory as it allowed the investigation of
different operating conditions. It is beneficial to use an inexpensive, routine method of
analysis to measure various interacting factors. RVA rheological measurement demonstrated
to be a decisive monitor of malt fermentability and is highly recommended to be incorporated
within the barley breeding, malting and brewing industries. / AFRIKAANSE OPSOMMING: Die verwantskap tussen mout fermenteerbaarheid en reologie-veranderlikes, gemeet met
die “Rapid Visco Analyser” (RVA) en toepassing van meerveranderlike data analise is
ondersoek.
Die RVA “Kilned Malt” metode is geoptimeer om maksimum reologiese diskriminasie,
tussen gars kultivars van verskillende fermenteerbaarheid, te lewer. Vyf konsentrasies en
twee partikel groottes is gebruik in die ondersoek vir elke mout monster. Data is deur beide
hoof komponent analise (HKA) en variansie-analise (ANOVA) ondersoek om die verskillende
data analise metodes met mekaar te vergelyk. Reologiese veranderlikes vir piek-hoogte, -
wydte, -area en -vormingstyd, kon diskrimineer tussen hoë (Metcalfe, Flagship), intermediêre
(SSG 585, PUMA) en lae (SSG 506, SSG 564) mout fermenteerbaarheid. Variasie in partikel
grootte kon nie beduidende diskriminasie in fermenteerbaarheid aantoon nie. Die mout-totwater
konsentrasie van 1:1.5 het die beste diskriminasie in fermenteerbaarheid gelewer. Die
toepassing van HKA op die hele datastel was die beter analitiese tegniek.
Parsiële kleinste kwadrate (PKK) regressie en Sagte Onafhanklike Modellering van Klas
Analogie (SIMCA) is toegepas om mout fermenteerbaarheid te voorspel. Regressie tussen
RVA data en skynbare attenuasie limiet (AAL), sowel as vrye amino stikstof (FAN) inhoud, is
afsonderlik uitgevoer. Die geldigheid van regressie modelle is deur middel van toets stel en
gesegmenteerde kruis-validasie vir AAL en FAN onderskeidelik uitgevoer. SIMCA
klassifikasie modelle is gebaseer op verskillende mout fermenteerbaarheids-klasse, waarvan
elke HKA klas individueel geldig is. RVA analise het ‘n sterk korrelasie met AAL (r=0.92),
maar ‘n swak korrelasie met FAN (r=0.59) getoon. Die SIMCA model het 83% van toets stel
monsters as korrek geklassifiseer in terme van mout fermenteerbaarheid. Suid Afrikaanse
mout mengsels is voorspel as swak fermenteerbaar. Nagebootste mengsels is voorspel as
hoogs fermenteerbaar wanneer minimum 80% Metcalfe met SSG 506 vermeng word. Sodra
‘n hoër persentasie van die swakker fermenteerbaarheids-kultivar (SSG 506) bygevoeg is,
word intermediêre fermenteerbaarheid voorspel.
Tydens RVA analise is verskillende eksperimentele toestande ondersoek (byvoorbeeld
instrument model; tyd/temperatuur profiel; ensiem aktiwiteit en verhittings/verkoelings
tempo). Die gebruik van verskillende RVA modelle het soortgelyke HKA resultate gelewer.
Dus bevat die ouer instrument aanvaarbare sensitiwiteit vir diskriminasie doeleindes.
Nabootsing van die tyd/temperatuur profiel in die kommersiële brouproses is verwerp,
aangesien analise tyd en reologiese geraas toegeneem het, terwyl fermenteerbaarheidsdiskriminasie
verminder het. Inaktivering van mout ensieme voor RVA analise lewer nuttige
monster inligting; deur veranderlikes soos piek-hoogte en piek-tyd te meet, kan die groot
stysel korrel se gemiddelde deursnit, ekstrakwaarde en stysel inhoud verkry word. Herhaalde
sentrifugale maling van ‘n mout monster lei tot beskadiging van stysel, maar dit word nie
deur sif grootte beïnvloed nie.
Die toepassing van meerveranderlike data analise op reologiese data is waardevol en
lewer meer relevante inligting in vergelyking met tradisionele eenveranderlike data analise.
Die RVA is ‘n ideale instrument vir gebruik in ‘n graan laboratorium aangesien dit
verskillende operatiewe kondisies kan ondersoek. Die gebruik van ‘n enkele, goedkoop,
roetine analitiese metode is voordelig en het die potensiaal om ‘n magdom interaktiewe
faktore te meet. RVA reologiese meting demonstreer die vermoë as ‘n deurslaggewende
tegniek vir die bepaling van mout fermenteerbaarheid, gevolglik word toepassing sterk
aanbeveel binne die gars teëlings-, vermoutings- en brouers-industrieë.
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Characterisation of zein from South African maize of varying endosperm textureO'Kennedy, Kim 03 1900 (has links)
Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Maize is an important crop for both human and animal consumption. Maize kernel texture
(kernel hardness) is an important quality trait for many sectors in the South African maize
industry, where a harder texture is desired. Both total protein content and the main storage
proteins, zein, have been associated with kernel texture. The zein profiles of South African
white maize hybrids, from a breeding program, grown at three localities together with their
respective inbred parent lines were evaluated to determine the difference in zein expression.
For only the hybrids, total protein content, zein content and degree of hardness (kernel texture)
was determined to establish possible relationships.
Zein consists of four main classes, α-, β-, γ-, and δ-zein, which can further be divided into
sub-classes. Zein was characterised using matrix-assisted laser desorption ionisation time-offlight
mass spectrometry (MALDI-TOF MS) after optimisation of the zein extraction and matrix
preparation procedures. Two matrices [2-(4-hydroxyphenylazo)benzoic acid (HABA) and α-
cyano-4-hydroxy-cinammic acid (CHCA)] and three pH levels (<1.5, 1.7 and 2.9) for matrix
solutions were investigated. Two solvent concentrations (50% and 70% acetonitrile (ACN) were
also investigated. Parallel to this investigation, a zein extraction procedure was optimised. Zein
was extracted from non-defatted (NDF) and defatted (DF) maize meal at ambient temperature
and 60°C and meal with different particle size distributions. Particle size of maize meal did not
influence the quality of spectra. Regardless of matrix conditions used, zein extracted at 60°C
from NDF meal produced spectra with a low signal-to-noise (S/N) ratio. When only HABA was
included (pH<1.5), not all γ-zein sub-classes were observed. This was also true for zein
extracted at ambient temperature from NDF and DF meal. Good S/N ratios for all zein classes
were obtained when zein was extracted from NDF meal at ambient temperature using a matrix
solution containing both matrices in 70% ACN at pH 2.9. MALDI-TOF MS provided accurate
detection and good profile resolution for zein characterisation. Spectral profiles of hybrids were
a combination of their respective inbred parent lines.
Zein proteins were quantified using reverse-phase high performance liquid chromatography
(RP-HPLC). Total protein content was determined and kernel texture assessed using a particle
size (PSI) method. Significant (P<0.01) differences were observed for total protein content and
degree of hardness between certain hybrids as well as average values for localities.
Correlations and principal component analysis indicated that hybrids with a higher protein and
total zein content had a harder kernel texture. The β- and γ-zein contents also correlated
positively with kernel hardness. However, when expressed as percentage of total zein the
opposite was observed. Collectively the α-zeins and most individual α-zeins correlated positively
with hardness. Scanning electron microscopy micrographs showed differences between the floury
endosperm of harder and softer maize kernels; illustrating starch types (amylose and
amylopectin) should also be analysed in future hardness studies.
The correlations obtained were not strong (r<0.6) and the variation explained by first two
principal components was low. Other maize constituents, more hardness measurements should
be considered in future studies to improve this. / AFRIKAANSE OPSOMMING: Mielies is a belangrike gewas vir beide mens- en dierlike inname. Mieliepittekstuur (pithardheid)
is ‘n belangrike kwaliteitseienskap vir baie sektore in die Suid Afrikaanse mielieindustrie, waar ‘n
harder tekstuur verlang word. Beide totale proteïeninhoud en die hoof opbergingsproteïen, zein,
is al geassosieer met pittekstuur. Die zein profiele van Suid- Afrikaanse witmielie basters, van ‘n
teel program, wat by drie lokaliteite verbou is sowel as hul onderskeie ingeteelde ouerlyne is geevalueer
om verskille in zein uitdrukking te bepaal. Die totale proteïeninhoud, zeininhoud en
graad van hardheid is bepaal om verhoudings vas te stel.
Zein bestaan uit vier hoof klasse, α-, β-, γ-, en δ-zein, wat verder onderverdeel word in subklasse.
Zein is gekarakteriseer met matriks-ondersteunende laser desorpsie ionisasie tyd-vanvlug
massa spektrometrie (MBLDI-TVV MS) na die zein ekstraksie en matriks
voorbereidingprosedures geoptimaliseer is. Twee matrikse [2-(4-hydroksiephenylazo)benzoë
suur (HABA) en α-cyano-4-hydroksie-kaneelsuur (CHCA)] en drie pH vlakke (<1.5, 1.7 and 2.9)
vir matriksoplossings was ondersoek. Twee oplossingkonsentrasies [50% and 70% asetonitriel
(ACN)] is ook ondersoek. Zein ekstraksie kondisies is ook geoptimiseer. Zein is geëkstraheer
van nie-ontvette (NOV) en ontvette (OV) mieliemeel by omgewings temperatuur en 60°C. Die
partikelgrootte van die mieliemeel het nie die kwaliteit van spektra beïnvloed nie. Ongeag watter
matrikskondisies gebruik is het zein wat van NGV meel by 60°C ge-ekstraheer is, spektra met ‘n
lae sein-tot-geraas (S/G) verhouding geproduseer. As die HABA alleenlik gebruik (by pH<1.5)
is, is nie alle γ-zein klasse waargeneem nie. Dit was ook waar vir zein wat by omgewings
temperatuur van NGV en OV mieliemeel ge-ekstraheer is. Goeie S/G verhoudings is
waargeneem met zein, ge-ekstraheer van NGV mieliemeel by omringende temperatuur, met die
bebruik van beide matrikse in 70% ACN by pH 2.9. (MBLDI-TVV MS) het akkurate en goeie
resolusie van profiele vir zein karateriseering verksaf. Spektrale profiele van basters was ’n
kombinasie van hul onderskeie ouer lyne.
Zeinproteïene is met omgekeerde-fase hoë prestasie vloeistofchromatografie
gekwantifiseer. Totale proteïeninhoud is bepaal en die hardheidsgraad was bepaal met ‘n
partikelgroote indeks (PGI) metode. Beduidende verskille tussen proteïeninhoud en
hardheidsgraad is waargeneem tussen sekere basters sowel as gemiddelde waardes by die
verskeie lokalieteite. Korrelasies en hoofkomponent analise het aangedui dat basters met ‘n
hoër proteïeninhoud en totale zein ‘n harder tekstuur gehad het. Die β- en γ-zeininhoud het ook
positief gekorreleer met hardheid. Alhoewel, wanneer die proteïene as persentasie van totale
zein uitgedruk is, is die teenoorgestelde waargeneem. Gesamentelik het α-zein asook die
meeste indivduele α-zeins positief gekorreleer met hardheid.
Skandeer elektron mikroskopie mikrograwe het verskille tussen die meelerige endosperm
van harder en sagter pitte aangedui; meer proteïenliggame was aanwesig in die harder pitte en die stysel was digter gepak. Dus moet stysel tipes ook in ag geneem word in toekomstige
hardheidsstudies.
Korrelasies wat verkry is, was nie hoog (r<0.6) nie en die variasie verduidelik deur die
eerste twee hoofkomponente was laag. Ander miielie samestellende dele as ook meer
hardheidsmetings moet in toekomstige studies in ag geneem word om dit te verbeter.
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Utilisation of pork rind and soya protein in the production of polonyMapanda, Chrispin 03 1900 (has links)
Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The purpose of this study was to determine whether acceptable polony can be manufactured with varying
quantities of chicken mechanically recovered meat (MRM), soya flour and pork rind to a fixed protein content
of 10%, irrespective of fat content and without the addition of more fat to obtain a total meat equivalent
(TME) of 75%. The effect of replacing MRM with soya and rind on the chemical, physical and sensory
characteristics of polony was measured. The cost of producing each treatment by using the varying
ingredients was also calculated.
Three levels of soya flour (0, 4 and 8%) were combined with three levels of pork rind (0, 8 and 16%)
to formulate the nine treatments of polony (R0S0, R0S4, R0S8, R8S0, R8S4, R8S8, R16S0, R16S4 and
R16S8, where R and S represents rind and soya, respectively). The cost of making the nine treatments
varied from R4.54/kg to R2.91/kg, where the most expensive treatment was the one in which no replacement
of MRM was done (R0S0) and the least expensive treatment was R16S8, where most MRM was substituted
with rind (16%) and soya (8%). The chemical results showed that the protein content of the nine treatments
varied between 9.7 and 10.5%. Fat and ash decreased while moisture and total collagen increased as more
MRM was being replaced with increasing levels of soya, rind or combinations of them.
The physical results indicated that L* and b* increased while a* decreased, resulting in treatment
samples which were lighter, more yellow and less red in colour. Hardness and gumminess increased in
samples singly replaced with 8% rind, 4% soya or their combination (R0S0, R0S4, R8S0 and R8S4), while
they decreased in the rest of the treatments. Cohesiveness increased in all treatments with increasing levels
of soya and rind except for the sample containing 16% rind and 8% soya (R16S8). The pH of treatments
containing 0% soya increased with rind increase whereas those with 4% soya did not change. The lowest pH
was for the sample with 16% rind and 8% soya (R16S8). Sliceability was used to determine the ease of
cutting intact slices at slice thicknesses of 2 and 3 mm. The sliceability of polony treatments which exhibited
good slicing characteristic ranged between 80 and 100% at both 2 mm and 3 mm slice thicknesses.
Sliceability was poorest for the treatment with high levels of rind and soya (R16S8) at both 3 mm (40%) and
2 mm (0%). The water holding capacity (WHC) of all treatments improved, except for the treatments to which
no rind and soya was added (R0S0) and the treatment in which MRM was replaced with 8% soya (R0S8).
Sensory analyses results signified that pink colour, colour intensity, salty taste, flavours (garlic,
polony and spicy) and firmness decreased while soya flavour, pasty and fatty mouthfeel increased with
increasing levels of rind, soya or their combination. Coarse texture decreased as rind increased while it
increased with an increase in soya levels. Only five treatments were employed for consumer analyses. The
most preferred treatment was that with 0% rind and 0% soya (R0S0), while the sample with 0% rind and 8%
soya (R0S8) was the least preferred. It can be concluded that the production of polony through the
replacement of MRM with rind and soya flour is possible, but consumer preference results show that
consumers like polony products which have low levels of soya (≤4%) and moderate levels of rind (≤8%).
However, the negative effects of rind and soya in polony with high levels of soya and rind can be rectified by
adding appropriate additives, as provided for by manufactured meat regulations. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om vas te stel of wisselende hoeveelhede meganies herwonne hoendervleis,
sojameel en swoerd gebruik kan word om aanvaarbare polonie te vervaardig met ʼn vaste proteïeninhoud
van 10%, ongeag die vetinhoud, en sonder die byvoeging van meer vet om ʼn algehele vleisekwivalent van
75% te kry. Hiervoor is die uitwerking op die chemiese, fisiese en sintuiglike kenmerke van polonie gemeet
wanneer meganies herwonne vleis (“mechanically recovered meat”, oftewel “MRM”) met soja en swoerd
vervang word. Voorts is die produksiekoste van elke formule op grond van verskillende bestanddele
bereken.
Drie vlakke sojameel (0%, 4% en 8%) is met drie vlakke swoerd (0%, 8% en 16%) gekombineer om
die nege polonieformules (R0S0, R0S4, R0S8, R8S0, R8S4, R8S8, R16S0, R16S4 en R16S8) te skep, waar
R die swoerd (“rind”) en S die sojameel verteenwoordig. Die vervaardigingskoste van die nege formules
wissel van R4,54/kg tot R2,91/kg: Die duurste formule was dié sonder enige MRM-vervanging (R0S0), en die
goedkoopste waar die meeste MRM met swoerd en soja vervang is (R16S8). Die chemiese resultate toon
dat die proteïninhoud vir die nege formules tussen 9,7% en 10,5% wissel. Vet en as het afgeneem en vog en
algehele kollageen het toegeneem namate al hoe meer MRM met toenemende vlakke soja, swoerd of ʼn
kombinasie daarvan vervang is.
Fisiese resultate toon dat L* en b* met MRM-vervanging toegeneem het, terwyl a* afgeneem het,
met ligter, geler en minder rooi monsters tot gevolg. Hardheid en taaiheid het toegeneem by monsters waar
MRM stuksgewys met 8% swoerd, 4% soja of ʼn kombinasie daarvan vervang is (R0S0, R0S4, R8S0 en
R8S4), terwyl dit by die res van die formules afgeneem het. Saamklewing het by alle formules met hoër
vlakke soja en swoerd toegeneem, buiten by die monster met 16% swoerd en 8% soja (R16S8). Die pH van
formules met 0% soja het toegeneem namate die swoerd vermeerder is, terwyl dié met 4% soja onveranderd
gebly het. Die laagste pH is aangeteken by die monster met 16% swoerd en 8% soja (R16S8). Snybaarheid
is bepaal aan die hand van die gemak waarmee skywe van onderskeidelik 2 mm en 3 mm dik gesny kon
word. Goeie snybaarheid, met ander woorde tussen 80% en 100%, is aangeteken vir polonie wat in sowel 2
mm as 3 mm diktes gesny kon word. Snybaarheid was die swakste vir die formule met hoë vlakke swoerd en
soja (R16S8), vir sowel die 3 mm (40%) as die 2 mm diktes (0%). Die waterhouvermoë het by alle formules
verbeter, buiten by die formule waarby geen swoerd of soja gevoeg is nie (R0S0) en die formule waar MRM
met 8% soja vervang is (R0S8).
Die resultate van die sintuiglike ontledings dui daarop dat die pienk kleur, kleurdiepte, sout smaak,
geure (knoffel, polonie en speserye) en fermheid afgeneem het, en die sojageur, deegagtige tekstuur sowel
as die tekstuur op die tong toegeneem het namate meer swoerd, soja of ʼn kombinasie daarvan bygevoeg is.
Grofheid van tekstuur het afgeneem namate die swoerd verminder is, terwyl dit weer toegeneem het met ʼn
toename in soja. Slegs vyf formules is vir verbruikersontledings gebruik. Die gewildste formule was dié met
0% swoerd en 0% soja (R0S0), terwyl die monster met 0% swoerd en 8% soja (R0S8) die minste byval
gevind het. Daar kan dus afgelei word dat polonieproduksie deur die vervanging van MRM met swoerd en
sojameel moontlik is, hoewel die proetoetsresultate toon dat verbruikers polonieprodukte met lae sojavlakke
(≤4%) en matige swoerdvlakke (≤8%) verkies. Tog kan die negatiewe uitwerking van groot hoeveelhede
swoerd en soja in polonie reggestel word deur toepaslike bymiddels, waarvoor die regulasies oor verwerkte
vleis voorsiening maak, by te voeg.
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Chemical, sensory and consumer profiling of a selection of South African Chenin blanc wines produced from bush vinesHanekom, Evette 12 1900 (has links)
Thesis (MScFoodSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Twenty five commercial Chenin blanc wines produced solely from bush vine vineyards and including three vintages, three styles and five production areas, were sourced for this study. Descriptive sensory analysis (DSA) and chemical analyses including GC-FID (gas chromatography fitted with a flame ionisation detector) and FTMIR (Fourier transform mid-infrared) spectroscopy were employed to establish the sensory and chemical characteristics, whereas consumer tests were conducted to determine consumer perception and liking of bush vine Chenin blanc wines. DSA (a profiling technique) was also compared to the sorting task (a classification technique) with a description assignment to evaluate the sorting task’s ability to profile wines.
According to the results of DSA, the wines separated into two groups. One group associated with sensory attributes which can be considered indicative of the Fresh and Fruity Chenin blanc style. The other group associated with sensory attributes which can be considered indicative of the Rich and Ripe style of Chenin blanc. No separation between the wooded and unwooded Rich and Ripe styles was apparent.
According to the results of the chemical analyses, the wines also separated into two groups. This separation seemed to be caused by vintage and the chemical changes associated with ageing as the wines from the youngest vintage (2010) was strongly associated with high levels of esters and malic acid. The older wines were situated farthest away from these attributes indicating low concentrations. When comparing the results from the sorting task and DSA, it could be seen that similar wine style groupings formed, indicating that DSA can also be regarded as an effective tool when categorising wines. The differences in the positioning of some of the wines and attributes on the DSA multivariate plots and the sorting task plots could be attributed to the difference in panels used. The sorting task was conducted using an expert panel with persons illustrating significant technical knowledge of Chenin blanc wines. Experience, exposure and technical knowledge tend to establish a common language amongst wine experts which could have caused the expert panel to perceive some wines differently when comparing the results of the latter panel to that of the trained panel. DSA was found to remain the most effective method for establishing a comprehensive sensory profile.
Consumer analyses showed that regular white wine drinkers prefer the unwooded styles (Fresh and Fruity and Rich and Ripe unwooded) of Chenin blanc more than the wooded style. It was also found that consumers with a higher level of objective wine knowledge tend to associate the terms ‘bush vine’ and ‘old bush vine’ with the Rich and Ripe style of Chenin blanc, whereas consumers with a lower level of objective wine knowledge associated ‘old bush vine’ with the Fresh and Fruity style. Since all the wines used in the consumer analysis were produced from old bush vines, it is evident that consumer education on the impact of bush vine training system and vine age on wine quality is needed. Better understanding of these principles could lead to elevated product appraisals and consumer satisfaction. / AFRIKAANSE OPSOMMING: Vyf en twintig kommersiële Chenin blanc wyne, uitsluitlik van bosstok wingerde geproduseer, is bekom vir hierdie studie. Die wyne het drie style, drie oesjare en vyf produksiestreke ingesluit. Beskrywende sensoriese analise (BSA) en chemiese analises, wat GC-FID (gas chromatografie gekoppel met vlam-ioniserende deteksie) en FTMIR (Fourier-transformering mid-infrarooi) spektroskopie insluit, is uitgevoer om onderskeidelik die sensoriese en chemiese eienskappe van die wyne te bepaal. Verbruikerstoetse is ook uitgevoer om verbruikerspersepsie en -voorkeure vir bosstok Chenin blanc wyne te bepaal. BSA (‘n profilerings tegniek) was ook vergelyk met ‘n sorterings taak (‘n klassifikasie tegniek) met ‘n beskrywings opdrag, primêr om die sorterings taak se vermoë om wyne te profileer te ondersoek.
Volgens die resultate van BSA, het die wyne in twee groepe verdeel. Een groep het met die sensoriese eienskappe wat op ‘n Vars-en-Vrugtige-styl dui, geassosieër. Die ander groep het met sensoriese eienskappe geassosieër wat met die Volrond-styl verband hou. Geen verdeling tussen die gehoute en ongehoute wyne binne die Volrond-styl was sigbaar nie.
Volgens die resultate van die chemiese analises, het die wyne ook in twee groepe verdeel. Die verdeling blyk asof dit veroorsaak is deur oesjaar en die chemiese veranderinge wat met wynveroudering gepaard gaan. Wyne van die jongste oesjaar (2010) het ‘n sterk verband met hoë vlakke van esters en appelsuur getoon. Die ouer wyne was verder weg van hierdie eienskappe geleë, wat op laer ester en appelsuur konsentrasies dui. Wanneer die meerveranderlike resultate van die sorterings taak (met en sonder die aanduiding van sensoriese eienskappe) en dit van BSA vergelyk word, kon soortgelyke groeperings gesien word. Dit is ‘n aanduiding dat BSA ook wyne effektief kan kategoriseer. Die verskil in posisionering van sommige wyne tussen die BSA en sorterings taak resultate, kan toegeskryf word aan die verskillende panele wat gebruik is om die tegnieke uit te voer. ‘n Deskundige paneel (wynkenners) is gebruik om die sortingstaak uit te voer. Ervaring, blootstelling en tegniese kennis is geneig om te lei tot die vestiging van ‘n gemeenskaplike taal onder wynkenners. Hierdie gemeenskaplike taal kan as rede aangevoer word vir die uiteenlopende analise van sommige wyne wanneer die resultate van die deskundige paneel met dié van die opgeleide paneel (in BSA gebruik) vergelyk word. Dit is gevind dat BSA, wanneer ‘n omvattende sensoriese profiel bepaal moet word, die mees effektiefste metode bly.
Verbruikerstoetse het getoon dat gereelde witwyn-verbruikers die ongehoute Chenin blanc style (Vars-en-Vrugtig en ongehoute Volrond) bo die gehoute styl verkies. Dit is ook bepaal dat verbruikers met ‘n hoër vlak van objektiewe wynkennis neig om die terme ‘bosstok’ en ‘ou bosstok’ met die Volrond-styl van Chenin blanc te assosieer, terwyl verbruikers met ‘n laer vlak van objektiewe wynkennis die term ‘ou bosstok’ met die Vars-en-Vrugtige Chenin blanc styl assosieër. Aangesien al die wyne wat in die verbruikerstoetse ingesluit is van ou bosstok wingerde geproduseer is, is dit duidelik dat verbruikeropvoeding insake die effek van die gebruik van bosstokke en ou wingerdstokke op wynkwaliteit noodsaaklik is. ‘n Beter begrip van hierdie beginsels sal lei tot verhoogde produkwaardasie, asook ‘n toename in verbruikertevredenheid.
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Postharvest losses and changes in quality of vegetables from retail to consumer : a case study of tomato, cabbage and carrotMunhuewyi, Karen 12 1900 (has links)
Thesis (MScFoodSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Postharvest losses of three different vegetables (tomato - a fruit, cabbage - a leaf and carrot - a root vegetable) were investigated directly after retail purchasing and during consumer simulated storage. To conduct this study, three retail outlets (2 supermarkets and an outdoor market) were selected in Stellenbosch, South Africa. Retail prices of each vegetable were recorded from each respective Outlet. Surrounding environmental conditions (air temperature and relative humidity) at retail and during simulated consumer storage were also monitored. Vegetable postharvest losses were determined by quantifying the incidence of physical loss and changes in physico-chemical properties (colour, firmness, weight loss, ascorbic acid, total pigments, total soluble solids, titratable acid and proximate composition) over time. The percentage losses observed were then used to estimate the associated economic and environmental resource impacts of postharvest vegetable losses at the national level.
Vegetable losses immediately at retail purchase were 14.56%, 21.21% and 17.93% for tomato, cabbage and carrot, respectively. The estimated combined volume lost for all three vegetables at national level was approximately 26 460 t valued at R33.70 million. Overall economic loss was highest for tomatoes and least for carrots. The magnitude of the losses observed differed for all the outlets. Vegetable losses were mostly high for the produce from the outdoor market compared to the supermarkets during storage. Throughout the whole trial, mechanical damage accounted for at least 50 to 70% of the losses while the remainder was due to decay and insect damage. Post retail storage temperature; ambient (22–25ºC) vs. cold store (0ºC and 10–12 ºC) had a significant (P<0.05) effect on the vegetable losses. This was for both quantitative and qualitative attributes. Losses for tomato and cabbage were 18.52% and 16.67% after 3 days while carrot losses were 11.83% at 7 days after having been kept in the recommended respective cold storage temperatures. Ambient storage losses were also lowest for carrots at 22.53% after 7 days, while tomato and cabbage losses stood at 24.27% and 34.34% after 3 days of storage, respectively. Vegetable firmness generally decreased while weight loss increased with storage time. Colour development increased favourably at ambient temperature for the tomato whereas for cabbage and carrot better colour retention was observed in the cold storage. Chemical changes for all three vegetables were also most pronounced at ambient temperature with significant (P<0.05) losses observed for ascorbic acid. Changes were also noted for total pigments, soluble solids and acidity, however there was no common significant trend for all three vegetables.
Estimates of carbon dioxide emissions reveal that postharvest vegetable losses contribute to unwarranted emissions of at least 1.37 – 13.77 million tonnes of carbon dioxide equivalents (CO2eq.) at the national level. The losses are also accompanied by wastage of approximately 3.74 – 4.35 million m3 of fresh water as well as 14.79 – 111.63 million MJ of fossil energy. The vegetable with highest production volumes and retail price was the tomato and accordingly, its postharvest losses had the severest environmental and resource impacts. / AFRIKAANSE OPSOMMING: Die ná-oes-verliese van drie verskillende groentes (tamatie – 'n vrug, kool – 'n blaar, en wortel – 'n wortelgroente) is direk ná kleinhandelaankope en tydens gesimuleerde verbruikersberging ondersoek. Ten einde hierdie studie uit te voer, is drie kleinhandelsafsetpunte (twee supermarkte en 'n opelugmark) in Stellenbosch, Suid-Afrika gekies. Die kleinhandelpryse van elke groente van die drie onderskeie afsetpunte is opgeteken. Omliggende omgewingstoestande (lugtemperatuur en relatiewe humiditeit) tydens verkope en gesimuleerde verbruikersberging is ook gemonitor. Die ná-oes-verliese van die groentes is bepaal deur die voorkoms van fisiese verlies en veranderings in fisio-chemiese eienskappe (kleur, fermheid, gewigsverlies, askorbiensuur, totale pigmente, totale oplosbare suikers, titreerbare suur en algemene samestelling) met verloop van tyd te versyfer. Die waargenome persentasie verliese is gebruik om die geassosieerde ekonomiese en omgewingshulpbron-impak van ná-oes-groenteverliese op nasionale vlak te beraam.
Groenteverliese met kleinhandelaankope was onderskeidelik 14.56%, 21.21% en 17.93% vir tamaties, kool en wortels. Die beraamde saamgestelde volume verlies vir al drie groentes op nasionale vlak was ongeveer 26 460 t, met 'n waarde van R33.70 miljoen. Die algehele ekonomiese verlies was die hoogste vir tamaties en die laagste vir wortels. Die omvang van die waargenome verliese het vir al die afsetpunte verskil. Groenteverliese tydens berging was hoofsaaklik hoog vir die produkte van die opelugmark in vergelyking met dié van die supermark. Tydens die algehele proefneming was meganiese skade verantwoordelik vir ten minste 50 tot 70% van die verliese, terwyl die res aan verrotting en insekskade toegeskryf kan word. Bergingstemperatuur ná kleinhandelaankope: omgewingstemperatuur (22 – 25 ºC) vs. koue berging (0 ºC en 10–12 ºC) het 'n beduidende (P < 0.05) uitwerking op groenteverlies gehad. Dit geld vir sowel kwantitatiewe as kwalitatiewe attribute. Verliese vir tamaties en kool was onderskeidelik 18.52% en 16.67% ná drie dae, terwyl dit vir wortels 11.83% teen sewe dae was nadat dit teen die aanbevole onderskeie koue bergingstemperature geberg is. Bergingsverliese in omgewingstemperatuur was ook die laagste vir wortels teen 22.53% ná sewe dae, terwyl die verlies van tamaties en kool onderskeidelik 24.27% en 34.34% was ná drie dae se berging. Die fermheid van die groente het oor die algemeen met die duur van berging verminder, terwyl gewigsverlies toegeneem het. Kleurontwikkeling het gunstig teen omgewingstemperatuur toegeneem vir die tamaties, terwyl die kleur van kool en wortels beter in die koue berging behou is. Chemiese veranderinge vir al drie groente was die sterkste teen omgewingstemperatuur, met beduidende (P < 0.05) verliese van askorbiensuur wat waargeneem is. Veranderinge is ook gemerk rakende totale pigmente, oplosbare vaste stowwe en suurgehalte. Daar was egter geen algemene beduidende neiging vir al drie groentes nie.
Beramings van koolstofvrystellings toon dat ná-oes-groenteverlies tot ongeoorloofde vrystelling van ten minste 1.37 tot 13.77 miljoen ton koolstofekwivalente (CO2eq.) op nasionale vlak bydra. Die verliese gaan ook gepaard met verbruik van ongeveer 3.74 tot 4.35 miljoen m3 vars water asook 14.79 tot 111.63 miljoen MJ fossielbrandstof. Die groente met die hoogste produksievolume en kleinhandelprys was die tamaties, en gevolglik het tamaties se ná-oes-verliese die ernstigste impak op die omgewing en op hulpbronne.
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Postharvest losses and changes in physico-chemical properties of fruit (peaches, pears and oranges) at retail and during post-purchase storageMatare, Tsaurayi Edwin 12 1900 (has links)
Thesis (MScFoodSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Postharvest fruit loss is a major challenge in addressing food security, sustainable management of resources and profitability of agribusiness. The incidence of postharvest loss and changes in physico-chemical properties of three types of fruit (peaches, pears and oranges) were evaluated at retail and during post-purchase storage. The amount of physical loss at the three retail outlets studied ranged from 3.61% to 18.09% among the fruit types, with the highest incidence occurring in peaches. The estimated annual national physical loss at retail was 418 tons for pears, 1000 tons for oranges, and 7 240 tons for peaches. Based on the WHO recommended 146 kg per capita per year consumption of fruit, the total loss of the three types of fruit was sufficient to meet the dietary fruit requirements of 50 000 people per annum. Similarly, based on the recommended daily allowance of 50 mg of ascorbic acid, these losses could meet the annual vitamin C needs of 82 000 people. The estimated monetary value of the losses at retail ranged from R2.2 million to R96.87 million per annum depending on fruit type and retail outlet. The land wasted to produce lost fruits was 1965 ha while energy wasted was 32.77 x 106 MJ. Greenhouse gas emission of the losses was 2870 tons CO2eq and total water footprint 68 0000 m3. Losses were mainly due to the presence of severe physical damage, rots and physiological disorders. There were significant variations in physico-chemical properties of fruit of the same type from different retail outlet. Although ambient temperature storage improved fruit colour and some chemical constituents responsible for palatability, it was associated with high physical and nutritional (vitamin C) losses. Results from this study show that appropriate harvesting maturity, packaging and maximum care in fruit handling is essential in reducing postharvest losses. Efficient cold chain management and fruit inspection for rots and damages could help to reduce subsequent spoilage at retail and during post-purchase storage. Given that the incidence of postharvest fruit loss observed at retail is the result of cumulative effects along the supply chain, further studies are warranted to map fruit history and magnitude of losses along the value chain. / AFRIKAANSE OPSOMMING: Naoesvrugteverlies is ‟n groot uitdaging in die strewe na voedselsekerheid, volhoubare hulpbronbestuur en winsgewende landbousake. Die voorkoms van naoesverlies sowel as fisiko-chemiese naoesveranderinge by drie vrugtesoorte (perskes, pere en lemoene) is gevolglik by kleinhandelsafsetpunte én gedurende berging ná aankoop beoordeel. Die graad van fisiese verlies by die drie betrokke kleinhandelspunte het gewissel van 3,61% tot 18,09% tussen die vrugtesoorte, met die hoogste verlies by perskes. Die geraamde jaarlikse nasionale fisiese verlies by die kleinhandelspunte was 418 ton pere, 1 000 ton lemoene en 7 240 ton perskes. Op grond van die Wêreldgesondheidsorganisasie se aanbevole jaarlikse vrugte-inname van 146 kg per persoon, was die totale verlies van die drie vrugtesoorte genoeg om aan die vrugtedieetvereistes van 50 000 mense per jaar te voldoen. Op grond van die aanbevole daaglikse inname van 50 mg askorbiensuur, kan hierdie verlies eweneens in die jaarlikse vitamien C-behoeftes van 82 000 mense voorsien. Die geraamde geldwaarde van die verlies by die kleinhandelspunte strek van R2,2 miljoen tot R96,87 miljoen per jaar, na gelang van die vrugtesoort en bepaalde kleinhandelspunt. Die vermorste grond om die verlore vrugte te produseer, was 1 965 ha, terwyl energievermorsing op 32,77 x 106 MJ te staan gekom het. Kweekhuisgasvrystellings met betrekking tot die verlies was 2 870 ton CO2e, en die totale watervoetspoor 68 0000 m3. Vrugteverlies kon hoofsaaklik aan ernstige fisiese skade, verrotting en fisiologiese afwykings toegeskryf word. Daar was beduidende variasies in die fisiko-chemiese eienskappe van dieselfde vrugtesoort by verskillende kleinhandelaars. Hoewel berging by omgewingstemperatuur vrugtekleur en bepaalde chemiese komponente vir smaaklikheid verbeter, word dit ook met groot fisiese en voedingstof- (vitamien C-) verliese verbind. Die resultate van hierdie studie toon dat toepaslike oesrypheid, die regte verpakking en maksimum sorg in vrugtehantering noodsaaklik is om naoesverlies te verminder. Doeltreffende koelkettingbestuur en vrugte-inspeksie vir verrotting en skade kan latere bederf by kleinhandelsafsetpunte sowel as gedurende berging ná aankoop help beperk. Aangesien die naoesvrugteverlies wat by die kleinhandelspunte waargeneem is uit kumulatiewe faktore in die verskaffingsketting spruit, is verdere studies nodig om vrugtegeskiedenis na te spoor en die omvang van die verlies in die algehele waardeketting te bepaal.
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Phenolic composition and in vitro antioxidant capacity of South African plums (Prunus salicina Lindl.)Venter, Alet 03 1900 (has links)
Thesis (MSc Food Sc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Phenolic compounds of the types present in plums have been found to exhibit health-promoting properties associated with their antioxidant capacity. Fruits with red peel and/or flesh are thus sought-after for their high antioxidant levels. In the current study South African plum (Prunus salicina Lindl.) cultivars and selections, harvested during two consecutive fruit seasons, were compared in terms of general fruit attributes (colour, firmness, °Brix, pH, titratable acidity), phenolic composition and antioxidant capacity. The effect of season and a commercial cold storage and ripening regime was also investigated.
A reversed-phase high-performance liquid chromatography-diode-array-fluorescence detection (HPLC-DAD-FLD) method suitable for use with mass spectrometry (MS) detection, was optimised for separation and identification of phenolic compounds from four phenolic groups (phenolic acids, anthocyanins, flavan-3-ols and flavonols) in six South African plum cultivars and five selections. Parameters that were optimised include the mobile phases, analysis temperature and gradient program. Good stability, linearity and inter- and intra-day precision were obtained. Identification of compounds was based on comparison of retention times, UV-Vis spectra and mass fragments with available authentic phenolic standards and/or literature data. The optimised method allowed identification or tentative identification of twenty-four phenolic compounds, including cyanidin-3-O-glycosides, quercetin glycosides, monomeric, dimeric and trimeric flavan-3-ols, and hydroxycinnamic acids. An on-line ABTS•+ (2,2ʹ-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid)) antioxidant assay, performed for qualitative evaluation of the antioxidant response of individual phenolic compounds, indicated the flavan-3-ols as major antioxidants in plums.
Eighteen phenolic compounds were quantified, including anthocyanins and flavonol glycosides, flavan-3-ols (monomers and dimers) and hydroxycinnamic acids. Phenolic composition differed greatly between cultivars and selections. Cyanidin-3-O-glucoside was the predominant anthocyanin in plums with red peel and/or flesh, followed by cyanidin-3-O-rutinoside. Cyanidin-3-O-galactoside was present only in the cultivar Laetitia (red peel, yellow flesh). The ripe fruit of Ruby Red and PR04-19, both with red peel and flesh, had the highest anthocyanin content for the first and second harvest season, respectively. Neochlorogenic acid and quercetin-3-O-glucoside were the major phenolic acid and flavonol, respectively. Chlorogenic acid, 3-O-p-coumaroylquinic acid and several quercetin-glycosides and -diglycosides were also present in some cultivars and selections. Procyanidin B1 was the flavan-3-ol present in the highest concentration in the majority of cultivars and selections and its content correlated with the (+)-catechin content, while the same was observed for procyanidin B2 and (-)-epicatechin.
The effect of cold storage and ripening on fruit attributes differed greatly between cultivars and selections. The increase and decrease in pH and titratable acidity, respectively, were as expected for ripe fruit as opposed to unripe fruit. Ripe fruit had higher a*-values and lower L*-values. The cold storage and ripening regime had no significant effect on total polyphenol and total flavan-3-ol content of the cultivars and selections, but the anthocyanin content increased in some cases.
In terms of in vitro antioxidant capacity, the selections PR04-32 and PR04-35, both with red peel and flesh, had the highest antioxidant capacity, irrespective of assay. Sapphire (red peel, yellow flesh), with the lowest total polyphenol content, also had the lowest antioxidant capacity in the ORAC and FRAP assays. Both the total polyphenol and flavan-3-ol contents correlated significantly to antioxidant capacity, irrespective of assay. / AFRIKAANSE OPSOMMING: Fenoliese verbindings, soos teenwoordig in pruime, is bekend vir hul gesondheidsbevorderende eienskappe wat geassosieer word met antioksidant kapasiteit. Vrugte met ‘n rooi skil en/of vleis is veral gesog as gevolg van hul hoë antioksidant aktiwiteit. Met hierdie studie is Suid-Afrikaanse pruim (Prunus salicina Lindl.) kultivars en seleksies, geoes tydens twee opeenvolgende seisoene, vergelyk in terme van algemene vrug einskappe (kleur, fermheid, °Brix, pH en titreerbare suurheid), fenoliese samestelling en antioksidant kapasiteit. Die effek van ‘n kommersiële koelopberging en rypwording prosedure is ook ondersoek.
‘n Omgekeerde-fase hoë-druk vloeistof chromatografie (HPLC) metode met diode-opstelling en fluoressensie deteksie, maar wat ook geskik is vir massa spektrometrie (MS), is geoptimiseer om fenoliese verbindings te skei en te identifiseer in Suid-Afrikaanse pruime. Verbindings van vier fenoliese groepe (fenoliese sure, antosianiene, flavan-3-ole en flavonole) wat in ses kultivars en vyf seleksies voorgekom het, is ondersoek. Die vloeistof fases, skeidingstemperatuur en gradiënt van die metode is geoptimiseer. Goeie resultate vir stabiliteit, lineariteit en inter- en intra-dag akkuraatheid is verkry. Verbindings is geïdentifiseer deur vergelyking van retensie tye, UV-Vis spektra en massa fragmente met dié van egte fenoliese standaarde en/of met literatuur data. Vier-en-twintig fenoliese verbindings is geïdentifiseer of voorlopig geïdentifiseer, insluitende sianidien- en kwersetien glikosiede, flavan-3-ol monomere, dimere en trimere, en hidroksikaneelsure. ‘n Aanlyn ABTS•+ (2,2 ʹ-azino-di-(3-etielbensotialosien-sulfoon suur) radikaal katioon blussingstoets is gebruik om die antioksidant reaksie van individuele polifenole op ‘n kwalitatiewe wyse te evalueer en flavan-3-ole is as hoof antioksidante in pruime aangetoon. Kwantifisering van agtien verbindings, insluitende antosianiene, flavonol glikosiede, flavan-3-ole (monomere en dimere) en hidroksikaneelsure, was moontlik met hierdie geoptimiseerde metode. Die fenoliese samestelling het aansienlik verskil tussen kultivars en seleksies. Sianidien-3-O-glukosied was die hoof antosianien in pruime met ‘n rooi skil en/of vleis, gevolg deur sianidien-3-O-rutinosied. Sianidien-3-O-galaktosied het slegs in Laetitia (rooi skil en geel vleis) voorgekom. Ryp vrugte van Ruby Red en PR04-19, beide met rooi skil en vleis, het onderskeidelik die hoogste antosianieninhoud gehad met die eerste en tweede seisoen se oeste. Neochlorogeniese suur en kwersetien-3-O-glukosied was die hoof fenoliese suur en flavon-3-ol, onderskeidelik. Chlorogeniese suur, 3-O-p-kumarienkwiniensuur en verskeie kwersetien glikosiede en diglikosiede was teenwoordig in sekere kultivars/seleksies. Die flavan-3-ol, prosianidien B1, was teenwoordig in die hoogste konsentrasie in die meerderheid kultivars/seleksies. Die prosianidien B1 inhoud het met die (+)-katekien inhoud gekorreleer, terwyl dieselfde gevind is vir prosianidien B2 en (-)-epikatekien.
Die effek van koelopberging en rypwording op die algemene vrug einskappe het tussen kultivars en seleksies verskil. Die pH en titreerbare suurheid het onderskeidelik toegeneem en afgeneem, soos verwag is vir ryp vrugte teenoor onryp vrugte. Ryp vrugte het hoër a*-waardes en laer L*-waardes getoon. Koelopberging en rypwording het geen beduidende effek op die totale polifenol- en totale flavan-3-ol inhoud gehad nie, maar die antosianieninhoud het vir sommige kultivars en seleksies toegeneem.
In terme van in vitro antioksidant kapasiteit het die seleksies PR04-32 en PR04-35, beide met rooi skil en vleis, die hoogste antioksidant kapasiteit getoon, ongeag die antioksidant toets wat gebruik is. Sapphire (rooi skil en geel vleis) het die laagste totale polifenolinhoud gehad, asook die laagste antioksidant kapasiteit soos bepaal deur die ORAC en FRAP toetse. Beide die totale polifenol- en flavan-3-ol inhoud het beduidend met die antioksidant kapasiteit korreleer, ongeag van die toets wat gebruik is.
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Cyclopia maculata : source of flavanone glycosides as precursors for taste modulating aglyconesDu Preez, Brigitte Von Pressentin 04 1900 (has links)
Thesis (MScFoodSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The flavanone aglycones, hesperetin and eriodictyol, have been identified as potential taste modulators
with reported sweetness-enhancing and bitterness-masking properties, respectively. Reduction of the
sugar content of food products has become important in view of the global obesity epidemic. Taste
modulators have shown potential to enhance the sweet taste of reduced-sugar foods without
unfavourably affecting their flavour profile. On the other hand, bitterness-masking taste modulators are
useful to mask the bitter taste of functional phytochemical ingredients. In the current study, Cyclopia
maculata (honeybush) was investigated as potential source of hesperetin- and eriodictyol-enriched
extracts. Hesperetin and eriodictyol were present mainly below the quantification limit in C. maculata
plant material, including unfermented leaf and stem material, unfermented and fermented tea, as well as
the fermented by-product (< 40 mesh and > 12 mesh). Conversely, their rutinoside and modulatinginactive
derivatives, hesperidin and eriocitrin were present at substantially higher concentrations in the
plant material. The stems and by-product were shown to be good sources of hesperidin, but not
eriocitrin. The qualitative and quantitative phenolic profile of the by-product was similar to that of the
stems. The tea processing by-product was therefore selected to optimise extraction of flavanone
glycosides for subsequent de-glycosylation of the flavanone glycosides to aglycones.
The by-product was subjected to ultrasound-assisted extraction to investigate its potential as
renewable source of the flavanone glycosides. Response surface methodology (RSM) was employed to
optimise and study the individual and interactive effects of the process variables, namely ethanol
concentration (% v/v), time (min), temperature (°C), and solvent:solid ratio (mL/g), on flavanone
glycoside extraction. The hesperidin yield and content (of extract), as well as extract yield, increased with
an increase in extraction time, temperature and solvent:solid ratio. Practical process restrictions limited
global optimisation and only an optimum of 52.8% (v/v) ethanol for extract and hesperidin yield could be
reached. Temperature was the parameter with the most significant effect (p < 0.05) on extraction
efficiency among those studied. Practical process parameter values that were feasible for industrial
application (52.8% (v/v) ethanol, 20 mL/g solvent:solid ratio, 60°C and 30 min) were selected for the
preparation of a flavanone glycoside-enriched extract from the tea processing by-product. The flavanone glycoside-enriched extract was subjected to acid-catalysed hydrolysis to deglycosylate
hesperidin and eriocitrin to hesperetin and eriodictyol, respectively. RSM was employed to
optimise the acid hydrolysis process and to study the effect of the hydrolysis parameters (temperature
(°C) and time (min)) on hydrolysis efficiency. At the maximum temperature (92.1°C) and corresponding
optimum time (98.4 min) ca 80% conversion of hesperidin to hesperetin was achieved. Substantially more
eriodictyol formed during acid hydrolysis than eriocitrin present in the initial extract owing to the deglycosylation
of unidentified glycosides with the same aglycone. Unidentified breakdown products
imparting a red colour to the acid-hydrolysed extract were also observed. The total phenolic content of the acid-hydrolysed extract was significantly higher (p < 0.05) than that of the unhydrolysed extract,
indicating the formation of unidentified compounds with the ability to reduce the Folin-Ciocalteau
reagent, although no significant difference (p ≥ 0.05) between the antioxidant activities of these extracts,
as assessed with the DPPH radical scavenging and ORAC assays, was observed. The potential of enzymatic
bioconversion as an alternative to acid-catalysed hydrolysis was investigated using commercial
hesperidinase. Bioconversion resulted only in de-rhamnosylation with ca 100% conversion of hesperidin
to hesperetin-7-O-glucoside in an aqueous C. maculata extract at pH 4.0 and 40°C. / AFRIKAANSE OPSOMMING: Die flavanoon aglikone, hesperetien and eriodiktiol, is geïdentifiseer as potensiële smaakmoduleerders
met berigte soetheid-versterkende en bitter-maskerende eienskappe, onderskeidelik. Vermindering van
die suikerinhoud van voedselprodukte het belangrik geword in die lig van die wêreldwye vetsugepidemie.
Smaakmoduleerders het die potensiaal getoon om die soet smaak van voedsel met verlaagde
suikerinhoud te versterk sonder om hul geurprofiel ongunstig te beïnvloed. Andersyds is bittermaskerende
smaakmoduleerders nuttig om die bitter smaak van funksionele fitochemiese bestanddele te
maskeer. In die huidige studie is Cyclopia maculata (heuningbos) ondersoek as ‘n potensiële bron van
hesperetien- and eriodiktiol-verrykte ekstrakte. Hesperetien and eriodiktiol was hoofsaaklik teenwoordig
onder die kwantifiseringsperk in C. maculata plantmateriaal, insluitend ongefermenteerde blaar- en
stokmateriaal, ongefermenteerde en gefermenteerde tee, asook die gefermenteerde byproduk (< 40
maas en > 12 maas). Hierteenoor was hul rutinosiedes en modulerend-onaktiewe derivate, hesperidien
and eriositrien, teenwoordig in aansienlik hoër konsentrasies in die plantmateriaal. Die stokmateriaal en
byproduk is getoon om goeie bronne van hesperidien, maar nie eriositrien nie, te wees. Die kwalitatiewe
en kwantitatiewe fenoliese profiel van die byproduk was soortgelyk aan dié van die stokke. Die teeprosesseringsbyproduk
is dus geselekteer om die ekstraksie van flavanoonglikosiede, voorafgaande hul
de-glikosilering na aglikone, te optimeer.
Die byproduk is aan ekstraksie met behulp van ultrasoniese klank onderwerp om die potensiaal
daarvan as hernubare bron van flavanoonglikosiede te ondersoek. Respons-oppervlak Metodologie
(ROM) is gebruik om die individuele en wisselwerking effekte van die proses veranderlikes, naamlik
etanolkonsentrasie (% v/v), tyd (min), temperatuur (°C), en oplosmiddel:vastestof verhouding (mL/g), op
flavanoonglikosied ekstraksie te optimiseer en te bestudeer. Die hesperidienopbrengs en -inhoud (van
ekstrak), sowel as die ekstrakopbrengs, het toegeneem met ‘n toename in die ekstraksietyd, -
temperatuur en oplosmiddel:vastestof verhouding. Praktiese prosesbeperkings het die globale
optimisering beperk en slegs ‘n optimum van 52.8% (v/v) etanol vir ekstrak- en hesperidienopbrengs kon
bereik word. Temperatuur was die parameter met die mees beduidende effek (p < 0.05) op ekstraksie
doeltreffendheid van dié wat bestudeer is. Praktiese prosesparameterwaardes wat haalbaar is vir
industriële toepassing (52.8% (v/v) etanol, 20 mL/g oplosmiddel:vastestof verhouding, 60°C en 30 min) is
geselekteer vir die voorbereiding van 'n flavanoonglikosied-verrykte ekstrak uit die teeprosesseringsbyproduk. Die flavanoonglikosied-verrykte ekstrak is aan suur-gekataliseerde hidrolise onderwerp om
hesperidien en eriositrien na hesperetien en eriodiktiol, onderskeidelik, te de-glikosileer. ROM is gebruik
om die suurhidrolise proses te optimeer en die effek van die hidrolise parameters (temperatuur (°C) en
tyd (min)) op hidrolise doeltreffendheid te bestudeer. Ongeveer 80% omskakeling van hesperidien na
hesperetien is behaal teen die maksimum temperatuur (92.1 °C) en ooreenstemmende optimum tyd (98.4 min). Aansienlik meer eriodiktiol is tydens suurhidrolise gevorm as eriositrien wat in die
oorspronklike ekstrak teenwoordig was, as gevolg van de-glikosilering van ongeïdentifiseerde glikosiede
met dieselfde aglikoon. Ongeïdentifiseerde afbreekprodukte, wat 'n rooi kleur aan die suurgehidroliseerde
ekstrak gegee het, is ook waargeneem. Die totale fenoliese inhoud van die suurgehidroliseerde
ekstrak was beduidend hoër (p < 0.05) as dié van die ongehidroliseerde ekstrak, wat die
vorming van onbekende verbindings met die vermoeë om die Folin-Ciocalteau reagens te reduseer
aandui, hoewel daar geen beduidende verskil (p ≥ 0.05) tussen die antioksidant-aktiwiteite van hierdie
ekstrakte, soos bepaal met die DPPH radikaal blussings- en ORAC toetse, waargeneem is nie. Die
potensiaal van ensiematiese bio-omskakeling as 'n alternatief vir suur-gekataliseerde hidrolise is
ondersoek met behulp van kommersiële hesperidinase. Bio-omskakeling het slegs tot de-ramnosilering
gelei met ca 100% omskakeling van hesperidien na hesperetien-7-O-glukosied in 'n C. maculata
waterekstrak by pH 4.0 en 40°C.
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