Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: This study shows Fourier transform near infrared (FT-NIR) spectroscopy's application
on wine, fruit and dried fruit for quantitative determinations or as a discriminative
method for classification purposes.
During wine production optimum yeast growth, resulting in healthy alcohol
fermentation rates, is monitored by the amount of free amino nitrogen (FAN) present
in the must. The status of malolactic fermentation (MLF) in Chardonnay wines is
monitored by determining the degree of conversion of malic to lactic acid. Ethyl
carbamate (EC), a suspected carcinogen, is mainly formed during ageing of wine and
is restricted by legislation in some countries. It is therefore necessary to determine
the EC content in wine.
Fourier transform near infrared spectroscopy can be used on wine as a rapid
method to measure the °Brix (residual sugars) content of must and to discriminate
between different must samples in terms of their FAN values. It can also be used as
a rapid method to discriminate between Chardonnay wine samples in terms of the
MLF status and between table wine samples in terms of the EC content. Calibrations
were derived and it was found that a very strong correlation existed in the sample set
for the FT-NIR spectroscopic predictions for °Brix (r = 0.99, SEP = 0.31%), but poorer
correlations for the FAN (r = 0.405, SEP = 275%), malic acid (r = 0.64, SEP = 1.02%),
lactic acid (r = 0.61, SEP = 1.35%) and EC predictions (r = 0.47, SEP = 3.6%). When
soft independent modelling by class analogy (SIMCA) was applied as a discriminative
method, the must and wine samples were classified in terms of their FAN and EC
values and MLF status, respectively, obtaining results with recognition rates
exceeding 80%.
The canning of peaches has become a significant industry in South Africa,
producing approximately 4.1 million cartons per year. Fourier transform near infrared
spectroscopy was applied as an alternative non-destructive method for the
quantitative determination of the total soluble solid (TSS) content of whole fresh
peaches. The TSS content of fresh clingstone peaches is an indication of the internal
quality, maturity and perceived sweetness of the fruit for the peach canning industry. By determining the TSS, fresh peaches can be graded and the farmers compensated
accordingly. Results obtained by building QUANT+™calibrations for the TSS content
(r = 0.96, SEP = 0.55%) showed acceptable accuracy and can replace the present
destructive methods.
Peak periods during the harvesting season necessitate storage of peaches for
up to three weeks before canning. Approximately 5 - 10% of the peaches stored,
disintegrate during canning due to loose skin, large stone cavities, soft flesh and rot.
The storage potential of fresh clingstone peaches can be successfully predicted with
FT-NIR and SIMCA models, using subjective internal quality evaluations. Results with
recognition rates exceeding 80% were obtained in most cases and this method
proved useful as a non-destructive method of quality assessment. By applying this
method, losses caused when storing peaches with poor storage quality will be
reduced.
The golden sultana industry plays an important role in the dried fruit exporting
market of South Africa. Due to the large numbers of consignments that must be
checked upon arrival, and the need for rapid decision making during processing, it is
essential to replace the present time-consuming analytical methods. Fourier
transform near infrared spectroscopy was used as a rapid, analytical technique to
determine whether the S0₂ and moisture contents of sultanas are within
specifications upon arrival at the factory and during processing. High positive
correlation was found between the measured values and those predicted by FT-NIR
spectroscopy for S0₂ (r = 0.99, SEP = 24.09%) and moisture (r = 0.99, SEP =
0.051 %) contents. / AFRIKAANSE OPSOMMING: Hierdie studie dui op Fourier transformasie naby-infrarooi (FT-NIR) spektroskopie se
toepassing op wyn, vrugte en droëvrugte vir die uitvoer van kwantitatiewe bepalings
of vir klassifikasie doeleindes om as 'n diskriminasie metode te dien.
Gedurende wynproduksie word die optimum groei van giste wat lei tot 'n
gesonde alkohol fermentasie gemonitor deur die hoeveelheid vry-aminostikstof (VAS)
wat in die mos teenwoordig is te bepaal. Die status van appelmelksuurgisting (AMG)
in Chardonnay wyne word gemonitor deur die mate van omskakeling van appelsuur
na melksuur te bepaal. Etielkarbamaat (EK), 'n vermoede karsinogeen wat
hoofsaaklik in verouderde wyne voorkom, word in sekere lande deur wetgewing
beperk en dus die bepaling van die EK inhoud van wyne noodsaak.
Fourier transformasie naby-infrarooi spektroskopie kan op mos toegepas word
as 'n vinnige metode vir die bepaling van °Brix (residuele suiker) en om tussen die
monsters te onderskei in terme van hulle VAS inhoud. FT-NIR kan ook gebuik word
as 'n vinnige metode om tussen Chardonnay monsters te onderskei op grond van die
status van AMG en tussen tafelwyn monsters op grond van die EK inhoud.
Kalibrasies is ontwikkel en daar is gevind dat baie sterk korrelasies bestaan in die
monsterstel vir die FT-NIR spektroskopiese voorspelling van °Brix (r = 0.99, SEP =
0.31%), maar swakker korrelasies vir die VAS (r = 0.405, SEP = 275%), appelsuur (r
= 0.64, SEP = 1.02%), melksuur (r = 0.61, SEP = 1.35%) en EK voorspellings (r =
0.47, SEP = 3.6%). Met die toepassing van soft independent modelling by class
analogy (SIMCA) as diskriminasie metode, is die mos- en wynmonsters geklassifiseer
op grond van hul VAS en EK waardes en die status van AMG, en
herkenningswaardes van bo 80% is onderskeidelik behaal.
Die inmaak van perskes het 'n beduidende industrie in Suid-Afrika geword en
produseer jaarliks ongeveer 4.1 miljoen kartonne. Fourier transformasie nabyinfrarooi
spektroskopie is toegepas as alternatiewe, nie-beskadigende metode om
kwantitatiewe bepalings van die totale oplosbare vastestowwe (TOV) inhoud van heel
vars perskes, te doen. Vir die perske inmaak-industrie is die TOV inhoud van vars
taaipitperskes 'n aanduiding van interne kwaliteit, rypheid en die soetheid van die vrugte. Vars perskes kan gradeer word deur die TOS te bepaal en sodoende kan
boere oreenkomstige vergoeding ontvang. Resultate' wat verkry is deur QUANT+™
kalibrasies vir TOS inhoud te ontwikkel (r = 0.96, SEP = 0.55%), dui op aanvaarbare
akkuraatheid en kan die huidige metodes vervang.
Tydens oestyd kom piektye voor wanneer dit soms nodig is om perskes vir tot
drie weke op te berg voordat dit ingemaak kan word. Ongeveer 5 tot 15% van hierdie
opgebergte perskes disintegreer tydens inmaak omdat opberging lei tot defekte in die
perskes soos skille wat loskom, groot pitholtes, sagte vleis en vrot. Die
opbergingspotentiaal van vars taaipitperskes kan suksesvol voorspel word deur FTNIR
en SIMCA modelle te bou en subjektiewe interne kwaliteitsevaluerings daarop
toe te pas. Herkenningsresultate wat 80% in die meeste gevalle oorskry, is behaal
wat hierdie metode as 'n suksesvolle nie-beskadigende kwaliteitbepalingsmetode
bewys. Hierdie metode sal verliese kan beperk wat voorkom as gevolg van
opberging van perskes met swak opbergingskwaliteit.
Die goue sultana industrie speel 'n belangrike rol in die droë vrugte
uitvoermark van Suid-Afrika. As gevolg van die hoeveelheid monsters wat gelyktydig
getoets moet word en besluite wat vinnig geneem moet word tydens prosessering, is
dit belangrik om die huidige tydrowende analitiese metodes te vervang. Fourier
transformasie naby-infrarooi spektroskopie is gebruik as 'n vinnige, analitiese tegniek
om tydens ontvangs by die fabriek en gedurende prosessering te bepaal of die S0₂-
en voginhoud van goue sultanas binne die spesifikasies val. Goeie positiewe
korrelasie is gevind tussen die bepaalde en voorspelde FT-NIR spektroskopiese
waardes vir SO₂- (r = 0.99, SEP = 24.09%) en voginhoud (r = 0.99, SEP = 0.051 %).
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51940 |
| Date | 12 1900 |
| Creators | Van Zyl, Anina |
| Contributors | Manley, M., Joubert, E., Wolf, E. E. H., Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science . |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 115 p. : ill. |
| Rights | Stellenbosch University |
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