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Effect of exogenous fibrolytic enzymes on fibre and protein digestion in ruminant animalsUseni, Bilungi Alain 03 1900 (has links)
Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Forages are the main feed components in ruminant production systems for the reason that they are often the major
source of energy available to the animal. However, only 10 to 35% of energy intake is available as net energy because
the digestion of plant cell walls is not complete. This can significantly affect livestock performance and profits in
production systems that use forages as a major source of nutrients of the diet. As a result of low and variable nutritive
values of forage feedstuffs, attempts to improve ruminal fibre degradability have been an ongoing research topic. The use
of exogenous fibrolytic enzymes (EFE) has been proposed as means to improve forage digestibility. Positive results with
regard to rumen forage digestibility and other animal production traits have consequently been obtained due to increased
rumen microbial activity following EFE addition in ruminant diets.
Two EFE (Abo 374 and EFE 2) and one commercial yeast preparation were firstly identified and selected for their
potential to improve the cumulative gas production (GP) at 24 hours of a range of feed substrates using the in vitro GP
system as a screening step to identify the superior EFE products. The different feed substrates were lucerne hay, wheat
straw, wheat straw treated with urea and a commercial concentrate diet. An in vitro experiment was undertaken on these
four different substrates in order to evaluate the two EFE and the yeast preparation. This was to identify the most
promising EFE capable of producing a significant effect on feed digestibility using organic matter digestibility (in vitro true
digestibility) and fermentation characteristics (in vitro GP system). Results from the in vitro evaluation showed that EFE
significantly enhanced in vitro DM degradability and GP profiles (P < 0.05). Abo 374 enzyme showed potential to increase
in vitro microbial protein synthesis (MPS) of GP residues of the concentrate diet. In addition, no correlation was found
between the in vitro MPS and the 48 hours cumulative GP of all the tested substrates (P < 0.05; R2 < 0.30). Treatments
were found to increase in vitro MPS, feed degradability and the cumulative GP of different quality forages and the
concentrate diet, with Abo 374 being the best treatment (P < 0.05). However in vitro responses of EFE were variable
depending on the energy concentration and chemical composition of different substrates. Variation in MPS was mostly
due to the low recovery of purine derivates with the purine laboratory analysis.
On the basis of these results, Abo 374 was selected and consequently further tested in another in vitro and in situ trial
using a mixed substrate of lucerne hay and wheat straw. Abo 374 significantly improved the cumulative GP, in vitro DM
and NDF disappearance of the mixed substrate (P < 0.05). In addition, no correlation was found between the in vitro MPS
and the cumulative GP at 48 hours (P = 0.68; R2 < 0.25). The in situ disappearance of feed nutrients (DM, NDF and CP)
with Abo 374 was similar to the control. The lack of significance of disappearance was probably due to the small number
of sheep used in the study and the relatively high coefficient of variation associated with measuring ruminal digestion. Abo 374 significantly increased the in situ MPS (P = 0.0088) of the mixed substrate of lucerne hay and wheat straw. Evidence
of the increased MPS and both in vitro and in situ disappearance of DM and NDF resulted from the Abo 374 activity
during either the pre-treatment or the digestion process. The addition of Abo 374 to the mixed substrate of lucerne hay
and wheat straw appeared to have been beneficial for microbial colonization of feed particles as a result of the increased
rumen activity. It could be speculated that the primary microbial colonization was thus initiated, leading to the release of
digestion products that attract in return additional bacteria to the site of digestion. This EFE may be efficient to produce
some beneficial depolymerisations of the surface structure of the plant material and the hydrolytic capacity of the rumen
to improve microbial attachment and the feed digestibility thereafter. Therefore, the mechanism of action by which Abo
374 improved the feed digestion can be attributed to the increased microbial attachment, stimulation of the rumen
microbial population and synergistic effects with hydrolases of ruminal micro-organisms. With regard to these findings, the
addition of EFE in ruminant systems can improve the ruminal digestion of DM, NDF and CP to subsequently enhance the
supply of the metabolizable protein to the small intestine.
Key words: crude protein (CP), exogenous fibrolytic enzymes (EFE), dry matter (DM), gas production (GP), neutral
detergent fibre (NDF), microbial protein synthesis (MPS). / AFRIKAANSE OPSOMMING: Ruvoere is die hoof-voerkomponent in herkouer produksiesisteme aangesien dit dikwels die vernaamstebron van energie
aan herkouer is. Slegs 10 tot 35% van die energie-inname is beskikbaar as netto-enrgie, omdat die vertering van
selwande onvolledig is. Dit kan die prestasie en profyt in produksiesisteme drasties beïnvloed waar ruvoere as ’n
hoofbron van nutriënte in die dieet gebruik word. Aangesien die nutriëntwaarde van ruvoere laag is en baie varieer, is
navorsing vir verbeterde ruminale veselvertering steeds ’n voorgesette onderwerp. Dit is voorgestel dat eksogeniese
fibrolitese ensieme (EFE) gebruik kan word vir verbeterde ruvoervertering. Positiewe resultate in ruminale ruvoerverterig
en ander diereproduksie-eienskappe, is verkry as gevolg van toenemende rumen mikrobiese aktiwiteit na EFE aanvulling
in herkouerdiëte.
Twee EFE’s (Abo 374 en EFE 2) en `n gisproduk is geïdentifiseer en geselekteer vir hul potensiaal om die kumulatiewe
gasproduksie (GP) na 24 uur met ’n reeks voersubstrate te verbeter met die gebruik van die in vitro GP sisteem as
seleksiemetode om die superieure EFE produkte te identifiseer. Die verskillende ruvoersubstrate was lusernhooi,
koringstrooi, ureumbehandelde koringstrooi en ’n kommersiële konsentraatdieet. ’n In vitro eksperiment was onderneem
om die vier verskillende substrate te gebruik om die twee EFE’s en gisproduk te evalueer. Hierdeur sou die belowendste
EFE’s identifiseer kon word wat ’n betekenisvolle effek op ruvoervertering het. Die vertering van ruvoer sal bepaal word
deur organiese materiaal vertering (in vitro ware vertering), asook fermentasie-eienskappe (in vitro GP sisteem).
Resultate van die in vitro evaluering het getoon dat EFE’s in vitro DM degradering en GP profiele verbeter. Dit blyk dat
die Abo 374 ensiem ’n potensiële toemame in in vitro mikrobiese proteïensintese (MPS), soos bepaal deur die GP
oorblyfsels van konsentraat diëte, tot gevolg gehad het. Daar was geen korrelasie tussen die in vitro GP en MPS van al
die proefsubstrate nie. Dit blyk dat die behandelings ’n toename in in vitro GP, MPS en ruvoerdegradeerbaarheid van lae
kwaliteit ruvoer- en konsentraatdiëte gehad het, waar Abo 374 die beste behandeling was. Die in vitro reaksies van die
EFE’s was egter wisselend, afhangende van die energiekonsentrasie en die chemiese samestelling van die verskillende
substrate. Variasie van MPS was meestal as gevolg van die lae herwinning van purienderivate tydens die purienanalise.
Op grond van dié resultate, is Abo 374 geselekteer om verdere toetse in ander in vitro en in situ proewe te doen. Die
substraat wat gebruik is, was ’n 1:1 mengsel van lusernhooi en koringstrooi. Abo 374 het die kumulatiewe RP, in vitro DM
en NBV verdwyning van die gemengde substraat verbeter. Boonop is geen korrelasie tussen die MPS en in vitro GP
gevind nie. In situ verdwyning van DM, NBV en RP was hoër vir Abo 374, maar nie betekenisvol nie. Die gebrek aan
betekenisvolle verdwynings mag die gevolg wees van die klein hoeveelheid skape wat in die proef gebruik is, asook die
relatiewe hoë koëffisient van variasie wat gepaard gaan met die bepaling van ruminale vertering. Abo 374 het die in situ MPS betekenisvol verhoog. Verhoogde MPS en in vitro en in situ verdwyning van DM en NBV is waargeneemwaarskynlik
as gevolg van die aktiwiteit van Abo 374 gedurende die voorafbehandeling óf die verterings proses. Die byvoeging van
Abo 374 tot die gemengde substraat van lusernhooi en koringstrooi blyk om voordelig te wees vir mikrobiese kolonisering
van voerpartikels as gevolg van ’n toename in rumenaktiwiteit. Die primêre mikrobiese kolonisering het waaarskynlik gelei
tot die vrystelling van verteringsprodukte wat addisionele bakterieë na die plek van vertering lok. Die EFE mag geskik
wees vir voordelige depolimerisasie op die oppervlakstruktuur van die plantmateriaal, asook verbeterde hidrolitiese
kapasiteit van die rumen om sodoende mikrobiese aanhegting, asook ruvoervertering te verbeter. Dus, Abo 374 se
meganisme van aksie wat verbeterde ruvoervertering tot gevolg het, kan toegeskryf word aan `n verhoogde mikrobiese
aanhegting, stimulering van die rumen mikrobiese populasie en die sinergistiese effek met hidrolases van rumen
mikroörganismes. Ten opsigte van die bevindings, kan die byvoeging van EFE in herkouersisteme ruminale vertering van
DM, NBV en RP verbeter, wat dan daaropvolgend die dunderm met meer metaboliseerbare proteïn sal voorsien.
Sleutelwoorde: eksogene fibrolitiese ensieme (EFE), droëmaterial (DM), ruproteïen (RP), neutraal bestande vesel (NBV),
mikrobiese proteïensintese (MPS), gasproduksie (GP).
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The effect of transport on live weight loss, meat quality and blood haematology in slaughter ostrichesWolmarans, Wilhelm J. 03 1900 (has links)
Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The production and export of ostrich meat from southern Africa, to especially the European Union, are
increasing rapidly due to the healthy nature of ostrich meat. The European Union has very high standards
when importing food products, and it is inevitable that more emphasis is being placed on the production of
high quality ostrich meat. Another aspect also of concern to consumers, is the welfare of animals prior to
slaughter, and this forces producers to look at ways to decrease stress of animals during the ante-mortem
period. Research regarding the effect of stress during the ante-mortem period, and as a result, on meat
quality, haematology and weight loss in ostriches, is lacking and thus the purpose of this study was to
investigate the effect of various transport distances, travel conditions and different birds on these factors.
Ante-mortem stress was measured using serum corticosterone levels (ng/ml), heterophil: lymphocyte (H:L)
ratio, white blood cell (WBC) count, aspartate aminotransferase (AST) and creatine kinase (CK), as well as
the rate and extent of pH decline in the M. gastrocnemius. Special emphasis was also placed on the meat
quality parameters drip loss, cooking loss, colour and Warner-Bratzler shear force (kg/1.27 cm diameter).
Live weight losses, as well as carcass weight and weight of bruises cut off from each bird were also recorded
during various stages of the trials.
The effect of transport distance on the meat quality of ostriches was investigated. Ultimate pHu
measurements were taken at 24 hours post-mortem. The muscles of the ostriches from the control group
(i.e. birds that were not transported prior to slaughter) had a lower mean pHu (5.77 ± 0.053) than birds that
travelled 60 (5.93 ± 0.053) and 600 km (6.11 ± 0.053), respectively. Differences in meat drip loss percentage
were also observed between the three treatments. The birds in the control group (0.40 ± 0.07 %) had the
lowest meat drip loss percentage compared to the birds that travelled 60 km (treatment C) (1.36 ± 0.07 %)
and 600 km (treatment B) (0.97 ± 0.07 %), respectively, to a commcerical ostrich abattoir. Ostriches that
were transported for 600 km (8.13 ± 1.16 %) had a greater percentage live weight loss during the antemortem period than birds that travelled a distance of 60 km (2.4 ± 2.185 %) to the abattoir, although both
groups were deprived of feed for the same period. When the haematology of the groups that travelled
different distances was compared at various time intervals in the ante-mortem period, both groups of birds
experienced significant increases in WBC, s-AST and s-CK. An increased H:L ratio from pre-transport to
post-transport was only evident in the birds that travelled 600 km (treatment B). However, the birds that
travelled 60 km were the only group of birds that had significant elevated serum corticosterone levels during
the ante-mortem period. The increase in the various blood parameters indicates severe physical stress,
which negatively affected meat quality.
Another trial also investigated the effect of various farming systems and transport on meat quality and
bruising of ostrich carcasses. Ostriches were raised in three different farming systems, i.e. feedlot -, semiintensive - and free range conditions. Other factors that could maybe impact on stress susceptibility, such as
road conditions, floorspace and floor type were also investigated. A significant difference in meat pHu was
found between ostriches that were raised in a feedlot (5.95 ± 0.018) and semi-intensive (6.04 ± 0.033) environment. The feedlot birds also had the greatest percentage of carcass weight removed due to bruising.
The free range birds were the birds that had the lowest floor density per birds and also had the least amount
of bruising on their carcasses. Incidently the other two groups (feedlot and semi intensive) were the birds
that travelled on the same type of road (mountain pass) in a truck with rubber flooring whilst the free range
birds travelled on a straight road in trucks with metal grid floors.The results indicate that the type of farming
system didn’t have a significant influence on meat quality of ostriches, but that factors such as road
conditions, flooring and bird density did play a significant role in the incidence of bruises and injuries
obtained during transport. / AFRIKAANSE OPSOMMING: Die produksie en uitvoer van volstruisvleis vanuit suidelike Afrika, na veral die Europese Unie, is gedurig aan
die toeneem as gevolg van die gesonde aard van volstruisvleis. Die Europese Unie het baie hoë standaarde
wanneer dit kom by die invoer van voedselprodukte en dit is onvermydelik dat meer klem op die produksie
van hoë gehalte volstruisvleis gelê word. ʼn Ander aspek wat ook kommer wek by verbruikers is die welstand
van diere voor slagting en hierdie aspek noodsaak produsente om te kyk na maniere om stres te beperk
tydens die periode voor slagting. Navorsing rakende die effek van stres tydens die ante-mortem periode,
asook vleiskwaliteit, hematologie en gewigsverlies in volstruise as gevolg van vervoer, ontbreek. Die doel
van die studie was dus om die invloed van verskillende vervoerafstande, vervoersomstandighede en tipe
produksiesisteme op volstruise se stresrespons te ondersoek. Die omvang van ante-mortem stres is bepaal
deur die serum-kortikosteroon vlakke (ng/ml), heterofiel: limfosiet (H:L) ratio, witbloedsel (WBS) telling,
aspartaat aminotransferase AST en creatien kinase CK, asook die tempo en vlak van pH-daling in die M.
gastrocnemius, te meet. Spesiale klem is gelê op die vleisgehalte parameters kookverlies, drupverlies, kleur
en Warner-Bratzler-skeurwaardes (kg/1.27 cm deursnee). Gewigsverlies is aangeteken op verskillende
stadiums tydens die proewe. Karkasgewigte en die hoeveelheid gewig afgesny van elke volstruiskarkas
a.g.v. kneusings is ook bepaal.
Die eerste studie het die invloed van vervoerafstand op vleiskwaliteit van slagvolstruise ondersoek. Vleis
kwaliteit parameters soos pH, drip verlies, kook verlies, taaiheid en kleur is ondersoek. Die pHu metings is op
24 uur post-mortem geneem. Slagvolstruise in die kontrole groep (d.i. -volstruise wat nie voor slagting
vervoer is nie) het ’n laer vleis pHu (5.77 ± 0.05) gehad as voëls wat onderskeidelik 60 km (5.93 ± 0.05) en
600 km (6.11 ± 0.05) ver vervoer is. Verskille in persentasie dripverlies is gesien tussen die vleis van die
voëls wat nie vervoer is nie (0.40 ± 0.07 %) en die voëls wat 60 km (1.36 ± 0.07 %) en 600 km ver (0.97 ±
0.07 %) onderskeidelik vervoer is. Volstruise wat vir 600 km (8.13 ± 1.16 %) vervoer is, het ‘n groter
persentasie lewende gewig tydens die ante-mortem periode as voëls wat 60 km (2.4 ± 2.19 %) ver vervoer is
na die abattoir, verloor, al was beide groepe weerhou van voer vir dieselfde tydperk. Beide groepe wat
vervoer is (60 en 600 km) het merkbare toenames in witbloedsel (WBS) tellings, s-AST’s en s-CK’s getoon
tydens die ante-mortem periode. Daar is slegs ʼn toename in H:L ratio (ʼn indikator van stres) van voor
vervoer tot na vervoer gesien in die voëls wat 600 km vervoer is. Daarteenoor was die voëls wat slegs 60 km
vervoer is die enigste voëls wat ʼn toename in korticosteroon vlakke getoon het gedurende die ante-mortem
periode. Die toenames is heel moontlik ‘n aanduiding van erge fisiese stres wat ‘n negatiewe effek op
vleiskwaliteit het.
Die tweede studie het die effek van verskillende produksiesisteme en die stress respons van die verskillende
groepe slagvolstuise op vervoer ondersoek. Vleis kwaliteit parameters soos pH, drip verlies, kook verlies en
taaiheid is ondersoek. Die hoeveelheid kneusings per volstruis is ook gemeet. Daar was ‘n beduidende
verskil (P = 0.009) tussen die pHu van die voerkraal (5.95 ± 0.018) en semi- intensiewe (6.04 ± 0.033) volstruise. Die voerkraal volstruise se vleis het die grootste drip- en kookverliese gehad in vergelyking met
die ander twee groepe (semi-intensiewe en ekstensiewe) terwyl die ekstensiewe volstruise die taaiste vleis
gehad het. Die voerkraalvoëls het ook die grootste persentasie karkasgewig verloor a.g.v. kneusings wat
afgesny is. Die ekstensiewe voëls het die laagste vloer digtheid per volstruis gehad asook die minste
kneusings. Die ander twee groepe (voerkraal en semi intensief) was die groepe wat op dieselfde pad vervoer
is (bergpas) in vragmotors wat rubber vloere gehad het terwyl die ekstensiewe voêls op ‘n reguit pad vervoer
is in ‘n vragmotor met ‘n metaal oppervlakte. Die resultate van die studie is ‘n aanduiding dat die tipe
plaassisteem nie ‘n groot impak op die hoeveelheid akute stres ervaar deur die voëls tydens vervoer gehad
het of gevolglik op die vleiskwaliteit van die volstruise nie, maar dat faktore soos pad toestand, tipe vloer en
voëldigtheid wel ‘n wesenlike rol speel in die voorkoms van kneusings en beserings opgedoen tydens
vervoer.
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Synthesis and characterisation of sesquioxidic precipitates formed by the reaction of acid mine drainage with fly ash leachateBurgers, C. L. (Colleen Lucie) 04 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Coal mining in South Africa is estimated to produce 200 Ml of acid mine drainage
(AMD) per day in the Pretoria-Witwatersrand-Vereeniging (PWV) area alone, while
electricity production resulted in approximately 27 Mt of ash in 2001. A large number
of collieries in South Africa are tied to power stations where these two waste streams,
acid mine drainage and fly ash, have the capacity to neutralize each other and provide
an opportunity for co-disposal.
The aim of this study was to investigate the reactions that occur during the co-disposal
of fly ash leachate (FAL) and AMD and to examine the precipitates that result from
the neutralisation reactions. Potentiometric titration was employed to investigate the
neutralisation of Al-Fe salt solutions, simulating acid mine drainage (AMD), with
alkaline solutions of Ca or Na hydroxide as well as fresh alkaline leachate from fly
ash (FAL). The effectiveness of fly ash in removing metals and other salts from acid
mine water was examined by analysing the neutralised water and modelling the
results thermodynamically. Precipitates, prepared from large scale synthetic AMD
and FAL co-disposal at various pH levels and Fe:Al ratios, were characterised
according to composition, mineralogy and surface properties.
The experimental neutralisation of synthetic acid mine drainage was achieved through
titrating the components of SAMD (Fe and Al salt solutions) and solutions of various
Fe:Al mole ratios with different bases in air and N2, and comparing the SAMD-FAL
system with these simple acids and bases. The FAL used in all experiments was
produced from fresh fly ash collected at Arnot power station. The SAMD was
prepared as a solution with a pH of 2.5 and containing 12.7 mmol/L Al, 10.9 mmol/L
Fe and 40.8 mmol/L SO4. The characterisation of reaction solids was achieved by
collecting the precipitates formed from the co-disposal of FAL and SAMD with Fe:Al
ratios of 7.3, 0.8 and 2.5.
From the titration experiments it was found that upscale potentiometric titrations of
SAMD show buffer zones at pH values of 3.5, 4, 6 and 10 corresponding to Fe(III)precipitation, Al precipitation, Fe(II) hydrolysis and oxidation, and Al redissolution,
respectively, while downscale potentiometric titrations with SAMD show buffer
zones at pH values 12 – 11, 9 and 4.5, which correspond to Fe oxidation and
precipitation, Al precipitation and Al re-dissolution, respectively. A high
concentration of Al in the simulated AMD inhibited the crystallinity of the
precipitates and resulted in a large quantity of SO4 being removed from solution,
which suggests that an aluminium sulphate phase is precipitating, but it is not
crystalline and cannot be identified by XRD. Titrations performed up-scale by adding
FAL to AMD showed near-complete metal and substantial SO4 removal from
solution.
The characterisation of reaction solids by x-ray diffraction, infrared spectroscopy,
thermal gravimetric and differential thermal analysis revealed that the precipitates
consist of poorly crystalline, highly Al-substituted goethite and ferrihydrite with large
amounts of SO4 included in the structure. Poorly crystalline bayerite appears at a high
pH and high Al concentration, and calcite is present in precipitates made by adding
SAMD to FAL. High surface charges of between 330 cmolc/kg positive and 550
cmolc/kg negative charge and potentially large specific surface areas between 7 and
236 m2/g suggest a strong potential for the precipitates to function as low-grade
adsorbents in wastewater treatment. The similarity of these ochre precipitates to soil
minerals implies that land disposal of the neutralised solids is also viable. / AFRIKAANSE OPSOMMING: Steenkool mynbou in SA produseer na benaming 200 ML suur mynwater per dag in
die PWV area alleenlik, terwyl opwekking van elektrisiteit naastenby 27 Mt vliegas
geproduseer het in 2001. ’n Groot aantal steenkoolmyne in SA word verbind met
kragsentrales, waar hierdie twee strome afval, suur mynwater en vliegas, die
kapasiteit het om mekaar te neutraliseer en die weg te baan vir gesamentlike
wegdoening.
Die doel van hierdie studie was om die reaksies wat plaasvind gedurende
gesamentlike wegdoening van vliegas loog (VAL) en suur mynwater (SMW) te
ondersoek, asook die neerslae wat mag vorm as gevolg van neutralisasie reaksies.
Potensiometriese titrasies was gebruik om die neutralisering tussen Al:Fe-sout
oplossings te ondersoek as nabootsing van SMW met gebruikmaking van alkaliese
oplossings van Ca of Na hidroksied asook vars loog van VA. Die effektiwiteit van
VA om metale en soute uit SMW te verwyder was getoets deur outleding van die
geneutraliseerde water en modellering van die termodinamika. Neerslae berei uit
groot-skaal sintetiese SMW en VAL en met gelyktydige storting by verskeie pH
vlakke en Fe:Al verhoudings, was gekarakteriseer volgens samestelling, mineralogie
en oppervlak eienskappe.
Die eksperimentele neutralisering van sintetiese suur mynwater (SSMW) was gedoen
deur titrering van die SSMW komponente en oplossings van verskeie Fe:Al molêre
verhoudings met verskillende basisse in lug en N2, en vergelyking van SSMW-VAL
sisteem met hierdie eenvoudige sure en basisse. Die VAL gebruik in alle
eksperimente was geproduseer van vliegas verkry van die Arnot kragsentrale. Die
SSMW was berei as ’n oplossing met ’n pH van 2.5 en bevat 12.7 mmol/L Al, 10.9
mmol/L Fe en 40.8 mmol/L SO4. Die karakterisering van vastestowwe uit die reaksie
was gedoen deur die bemonstering van neerslae gevorm as gevolg van die gelyktydige
wegdoening van VAL en SSMW met Al:Fe verhoudings van 7.3, 0.8 en 2.5.Die was waargeneem in die titrasie eksperimente dat hoër-skaal potensiometriese
titrasie van SSMW buffersones, by pH waardes 3.5, 4, 6 en 10, ooreenstem met
Fe(III) presipitasie, Al presipitasie, Fe(II) hidrolise en oksidasie, en Al her oplossing,
terwyl laer skaal potensiometriese titrasie met SSMW buffer sones by pH waardes 12
- 11, 9 en 4.5 ooreenstem met Fe(III) presipitasie en oksidasie, Al presipitasie en
heroplossing respektiewelik. ’n Hoë konsentrasie Al in die sintetiese SMW het
kristalliniteit van die neerslae geïnhibeer en veroorsaak dat ’n hoeveelheid SO4 uit
oplossing verwyder is, wat suggereer dat die AlSO4 fase neerslaan maar nie kristallyn
is en gevolglik nie opgetel word met x-straal diffraksie nie. Titrasies gedoen by hoërskaal
deur byvoeging van VAL tot SSMW, het feitlik volledige metaal en SO4
verwydering uit oplossing getoon.
Die karakterisering deur x-straal diffraksie, infrarooispektroskopie, termies
gravimetries en differentiële termiese analise, het getoon dat die presipitate bestaan uit
swak kristallyne, hoë Al-gesubstitueerde goethiet en ferrihidriet met groot
hoeveelhede SO4 vasgevang in die struktuur. Swak kristallyne bayeriet verskyn by
hoë pH en hoë Al-konsentrasies en kalsiet is teenwoordig in neerslae gevorm deur
byvoeging van SSMW tot VAL. Hoë oppervlakladings van tussen 330 cmolc/kg
positief en 550 cmolc/kg negatiewe lading en ook potensieel groot spesifieke
oppervlak van tussen 7 en 236 m2/g, dui op ’n sterk potensiaal vir neerslae om as
laegraadse adsorbeermiddels in afvalwaterbehandeling gebruik te word. Die
ooreenstemming in hierdie geelbruin neerslae met grond minerale, impliseer dat die
land storting van geneutraliseerde vastestowwe ook lewensvatbaar is.
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Morphology, mineralogy and surface chemistry of manganiferous oxisols near Graskop, Mpumalanga Province, South AfricaDowding, Catherine Elaine 12 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: In the humid Graskop region of Mpumalanga Province, South Africa, there is an
anomalous body of highly weathered black, manganiferous oxisols derived from dolomite.
With Mn contents as high as 17%, potential large-scale Mn release is an environmental
concern under current, acid generating, forestry practices. This study aims at establishing
the factors which may affect the stability of the manganiferous oxisols of Graskop and in
the process, investigating some of the morphological, mineralogical and chemical
properties of these unique soils.
Typically, the soils show a reddish, nodule-rich horizon, containing 3-4% Mn, grading
through a red and black mottled zone into a black (5YR 2.5/1) apedal subsoil with >7%
Mn. The Mn gradient down the profile as well as the abundant nodule content of the upper
subsoil horizons implies that Mn mobilization and redistribution are active pedogenic
processes. The exceptional Mn content of these soils is complemented with Fe and Al
concentrations of up to 10 and 8%, respectively, and anomalously high trace element levels
in particular Ni and Zn (as high as 541 and 237 mg kg-1, respectively) which are at the
upper limit of cited world natural maxima for soils. The Mn mineral lithiophorite
[(Al,Li)MnO2(OH)2], dominates the mineralogy of the soils with accessory amounts of
birnessite, gibbsite, goethite, hematite, maghemite, kaolinite, aluminous chlorite and mica -
a mineral suite reflecting that of well weathered soils.
With the pH of the soil being at or close to the point of zero charge (4.5-5.5) the soils show
isoelectric equilibrium. The very low buffer capacity results in metal dissolution
commencing with the first increment of titrated acidity. Manganese dissolution is relatively
minor considering the large potential for release and is highly overshadowed by Al release.
The apparent resilience of the Mn phase to added acidity may relate to the overwhelming
poise of the soils which maintains robust, oxic conditions despite the usual instability of
Mn oxides at low pH.
Manganese release and soil redox properties are substantially affected by drying especially
in the organic rich topsoils. Using various redox analyses, evidence is shown for
involvement of Mn(III)-organic complexes in the drying reactions. Using this and
information gained in a real time, attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopic study, a mechanism is suggested which may account for the
observed Mn release and the loss of Cr oxidising capacity commonly observed in dried
soils. The information provided by the ATR-FTIR study showed the decrease in surface
pH of a clay film, from 5 to below 2, as well as the shift in coordination nature of sorbed
oxalate from a more outer-sphere association to a more inner-sphere association
concomitant with the removal of free water from the clay surface. This spectroscopic
evidence for these chemical changes which accompany surface drying not only provides
further insight into the reactions involving Mn oxides in soils but also highlights the
suitability of ATR-FTIR for real time, in situ investigation into the chemistry of the drying
water interface.
From these results it is concluded that Mn release from the manganiferous oxisols, under
acid generation of the kind known to occur in pine plantations, is less that anticipated. On
the other hand, desiccation of the topsoil results in substantial Mn release with a suggested
mechanism which involves a Mn(III) intermediate. / AFRIKAANSE OPSOMMING: ‘n Onreelmatige grondliggaam van hoogs verweerde, swart, mangaanhoudende oxisols
wat uit dolomiet ontwikkel het, word in die humiede Graskop streek van die Mpumalanga
Provinsie van Suid-Afrika aangetref. Die hoë Mn-inhoud (tot 17%) van hierdie oxisols is
van groot omgewings-belang weens die potensiële grootskaalse Mn-vrystelling onder
huidige, suur-genererende bosbou praktyke. Hierdie studie beoog om die faktore wat die
stabiliteit van die mangaanhoudende oxisols van Graskop affekteer, vas te stel. Tesame
hiermee word die morfologiese, mineralogiese en chemiese eienskappe van hierdie
unieke gronde ondersoek.
Kenmerkend van hierdie gronde is ‘n rooi, nodule-ryke horison met 3-4% Mn aan die
oppervlakte. Bogenoemde horison verander met toename in diepte in ‘n rooi en swart
gevlekte sone wat weer in ‘n swart (5YR 2.5/1) apedale ondergrond met >7% Mn
oorgaan. Die Mn gradiënt in die profiel sowel as die hoë nodule-inhoud van die boonste
grondhorison dui daarop dat Mn-mobilisasie en -herverspreiding huidige aktiewe
pedogenetiese prosesse in die profiele is. Fe en Al, met konsentrasies van 10% en 8%
onderskeidelik, word saam met die onreelmatig hoë Mn inhoud aangetref. Baie hoë
vlakke van Ni en Zn (so hoog as 541 en 237 mg.kg-1 onderskeidelik) wat hoër is as
aangehaalde wêreld natuurlike maksimum waardes, word ook aangetref. Die mineralogie
van die gronde word deur die Mn mineraal litioforiet [(Al,Li)MnO2(OH)2] gedomineer.
Bykomstige hoeveelhede van birnessiet, gibbsiet, goethiet, hematiet, maghemiet,
kaoliniet, aluminiumryke chloried en mika word ook aangetref. Hierdie minerale
samestelling is kenmerkend van hoogs verweerde gronde.
Met die pH van die grond in die omgewing van die punt van geen lading (4.5 – 5.5),
word ‘n iso-elektriese ekwilibrium by die gronde aangetref. Die baie lae bufferkapasiteit
het metaal-oplossing aangehelp wat met die eerste inkrement van titreerbare suurheid ‘n
aanvang geneem het. Mangaan-oplossing is baie klein indien die groot potensiaal vir
vrystelling asook die groot mate van Al-vrystelling in ag geneem word. Die skynbare
teenwerking van die Mn fase tot toegevoegde suurheid, mag toegeskryf word aan diesterk ewewig van die gronde om sterk, oksiese kondisies, ten spyte van die normale
onstabiliteit van Mn oksiedes by lae pH, te onderhou.
Mangaan vrystelling en grond redoks eienskappe word beduidend deur uitdroging
beïnvloed en veral in die organies-ryke bogronde. Deur van verskeie redoks analises
gebruik te maak is daar bewyse van die betrokkenheid van Mn(III)-organiese komplekse
in die uitdroging-reaksies gevind. Dit. en data ingesamel in ‘n “real time, attenuated total
reflectance Fourier transform infrared (ATR-FTIR)” spektroskopiese studie, is gebruik
om ‘n meganisme voor te stel wat die waargenome Mn vrystelling en die verlies aan Cr
oksidasie kapasiteit (algemeen waargeneem in droë gronde) te kan verklaar. Die data
verkry met die ATR-FTIR studie het ‘n afname in oppervlak pH van 5 na 2 van ‘n klei
film asook die verskuiwing in koördinasie toestand van die gesorbeerde oksalaat van ‘n
meer buite-sfeer assosiasie tot ‘n meer binne-sfeer assosiasie, gepaardgaande met die
verwydering van vry water van die klei oppervlaktes, uitgewys. Die spektroskopiese
bewyse vir die chemiese veranderinge wat die oppervlak uitdroging vergesel, gee nie net
meer insig in die reaksies rakende Mn oksiedes in gronde nie maar onderstreep ook die
toepasbaarheid van die ATR-FTIR vir intydse (“real time”), in situ ondersoeke na die
chemie van die uitdrogende water kontakvlak.
Vanuit hierdie resultate kan afgelei word dat Mn vrystelling vanuit mangaanhoudende
oxisols onder suur genererende denne plantasies laer is as wat verwag is. Aan die ander
kant sal uitdroging van die bogrond tot aansienlike Mn vrystelling, met ‘n verwagte
meganisme wat Mn (III) as intermediêre toestand insluit, lei.
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Soil health and quality concept in agricultural extension and soil science : an assessment of topsoil conditions in a long term vineyard soil management trail in Robertson, South AfricaMathys, Ilse Lois 03 1900 (has links)
Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT:
The natural resource condition or health has been accepted as a valuable indicator of
sustainable land use. The assessment of soil health (quality) has become a valuable tool in
determining the sustainability of land management systems. This work aims to evaluate the
sustainability of soil management practices in agricultural extension for vineyards in
Robertson, South Africa based, on the current approach of the concept of soil health and
soil quality, as well as to briefly explore the present reservations regarding the definition of
the concept. The soil management treatments include a mechanical weed control, chemical
weed control, annual addition of straw mulch, annual cover crop and perennial cover crop.
The objective of study is to (i) identify suitable soil health (quality) indicators for vineyards in
the study area; (ii) analyze the soil health (quality) indicators for different soil management
treatments; (iii) evaluate the effect of various soil management treatments on the overall
soil functionality, by comparing measured indicators to the soil property threshold values,
for optimal vine growth; iv) establish a more consistent understanding and use of the terms
health and quality, as understood and used in the general science community, with
particular reference to the public health system. The soil physical, chemical and biological
properties which were selected as indicators of soil health (quality) based on specific criteria
similar to previous work done on the concept. The properties selected include soil texture,
gravimetric water content, bulk density, soil aeration, water aggregate stability, soil pH, EC,
available N,P,K , soil organic matter content, soil microbial biomass, potential mineralizable
nitrogen and soil respiration. The study makes use of methods of analysis previously used
for soil health and soil quality assessments, as well as soil analytical methods as accepted by
experienced soil scientist within the study area. The soil was sampled on three separate
events to depths of 0-200 mm for initial characterization of soil and 0-50 mm to compare
soil health (quality) Between tracks and In tracks of treatment plots. The values obtained for
each property were compared with the optimum for vineyards and ranked accordingly. The
treatment that resulted in the most desirable soil health (quality) was the straw mulch and
perennial cover crop treatments. / AFRIKAANSE OPSOMMING:
Die toestand of gesondheid van natuurlike hulpbronne is aanvaar as `n waardevolle
aanduiding van volhoubare grondgebruik. Die assessering van grond gesondheid (kwaliteit)
is 'n waardevolle hulpmiddel in die bepaling van die volhoubaarheid van grond bestuur
stelsels. Hierdie werkstuk poog om die volhoubaarheid van grond bestuurs praktyke te
evalueer vir wingerde in Robertson, Suid-Afrika wat baseer is op die huidige benadering van
grond gesondheid en kwaliteit. Die tesis dek ook die huidige onsekerhede oor die konsep en
definisies van terme wat gebruik word in die konsep. Die grond bestuur praktyke sluit in 'n
meganiese onkruidbeheer, chemiese onkruidbeheer, jaarlikse toevoeging van `n strooi
deklaag, jaarlikse en meerjarige dekgewas dekgewasse. Die doel van die studie was om (i)
die geskikte grond gesondheid (kwaliteit) indikators vir wingerde in die studie area te
identifiseer, (ii) die grond gesondheid (kwaliteit) indikators vir verskillende bogrond bestuur
praktyke te identifiseer; (iii) die effek van verskillende grond bestuur praktyke op die
algehele grond funksies te evalueer, deur dit te vergelyk met die gemete indikators vir
drempelwaardes vir optimale wingerd groei; iv) 'n meer konsekwente begrip en gebruik van
die terme “gesondheid” en “kwaliteit” vas te stel, soos dit verstaan en gebruik word in die
algemene wetenskaplike gemeenskap, met spesifieke verwysing na die openbare
gesondheidsisteem. Die grond fisiese, chemiese en biologiese eienskappe wat as indikators
van grond gesondheid (kwaliteit) geselekteer was, word gebaseer op spesifieke kriteria
soortgelyk aan dié wat in vorige werk op die konsep gedoen was. Die eienskappe wat
geselekteer is sluit in grondtekstuur, gravimetriese waterinhoud, bulk digtheid, grond
deurlugting, totalle water stabiliteit, grond pH, electriese geleiding, toeganklike N, P, K,
grond organiese materiaal inhoud, grond mikrobiese massa, potensiële mineraliseerbare
stikstof en grond respirasie. Die studie maak gebruik van analitiese metodes wat voorheen
gebruik was vir grond gesondheid en kwaliteit, sowel as die grond analitiese metodes soos
gebruik deur ervare grondkundiges binne die studie gebied. Die grondmonsters was geneem
op drie afsonderlike geleenthede oor dieptes van 0-200 mm vir die aanvanklike
karakterisering van grond en 0-50 mm, om grond gesondheid (kwaliteit) Tussen
trekkerspore en In trekkerspore van die persele te vergelyk. Die waardes verkry vir elke
eienskap was vergelyk met die optimum vir wingerde en verdeel volgens kwaliteit. Die
behandeling wat die mees optimale grond gesondheid (kwaliteit) getoon het, was die strooi
deklaag en meerjarige dekgewas behandelings.
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Rain events based hillslope hydrological processes at the Langgewens Experimental Farm, Western Cape, South AfricaWasserfall, Michiel Nicolaas 03 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Hillslope hydrology represents a complex system with several interacting processes influencing the movement of water through the landscape. The Western Cape area of South Africa is expected to be impacted on by a change in climate and the importance of water management that will increase in the future. Climate, especially precipitation, is the driving factor behind the hydrological system and there are currently no predictions as to what the impact will be on the hydrological conditions. The main objective of the study is to understand the hydrological responses along a hillslope and secondly to determine the effect of climate change on the hydrology by using hydrological models.
The studied system is situated on the Langgewens Experimental Farm, north of Malmesbury in the Swartland region of the Western Cape. Six sites in a range of vegetation, land use and expected soil types along a toposequence were investigated. All sites are rain fed areas with natural vegetation, seasonal or long-term shrubs. Through monitoring different components of the hydrological cycle, including rainfall, overland flow, infiltration, soil water content, base flow and water table depth at the different sites, the movement of water through the landscape can be defined. Hillslope hydrological processes at different positions on the hillslope were investigated. The baseline data obtained during this process was used in hydrological modelling for the different positions on the hillslope to determine the accuracy of model predictions. Expected future climatic conditions were emulated in this model to determine the possible effect of a change in climate on the hydrological system.
The research confirmed the complex interaction between different processes within the hydrological system. At each point along the toposequence different components of the hydrological cycle contributed on a different scale to the hydrological system. Soil properties were the most significant factor influencing water movement through the landscape, directly impacting infiltration, overland flow, lateral water flow and deep percolation. This resulted in water table fluctuations through the seasons as the contribution of different components towards the hydrological cycle changed. By comparing soil water content measurements through the season with modelled water content levels, accurate hydrological models were created for different measuring points in the landscape. By using forecasted climate data of two different weather generators, accurate estimations of expected soil water content were possible. This indicated that droughts will occur on a regular basis in the future. This research made it possible to understand water movement through the landscape at hillslope level and contributed towards future water management plans by estimating future soil water content levels based on current predictions. / AFRIKAANSE OPSOMMING: Heuwelhang hidrologie omskryf die proses van water beweging deur die landskap en dit word deur verskeie prosesse beinvloed. Onder huidige toestande word verwag dat die Weskaap provinsie van Suid-Afrika warmer en droëer sal word in die toekoms as gevolg van klimaatsverandering. Dit sal die noodsaaklikheid van effektiewe waterbestuur verhoog in die toekoms. Klimaat, en in besonder reënval, is die dryfkrag agter die hidrologiese sisteem en huidiglik is daar geen aanduiding van wat die effek van klimaatsverandering op die hidrologiese sisteem gaan wees nie. Die eerste doel van die studie is om die heuwelhang se hidrologiese sisteem te ontleed en tweedens om die impak van klimaatsverandering op die hidrologiese sisteem te bepaal deur gebruik te maak van hidrologiese modelle.
Die studie area is geleë op die Langgewens Proefplaas, noord van Malmesbury in die Swartland distrik van die Weskaap. Ses verskillende posisies is op die heuwelhang geselekteer op grond van posisie in die landskap, plantegroei, landgebruik en verwagte grondvorms. Al die studiepunte ontvang slegs water deur reën en die landgebruik wissel ten opsigte van natuurlike plantegroei, en eenjarige- of meerjarige gewasse wat gevestig is. Deur verskillende komponente van die hidrologiese sisteem te monitor, insluitend reënval, oppervlak afloop, infiltrasie, grond water inhoud, laterale water vloei en die diepte van die watertafel, kan die beweging van water deur die landskap gedefinieër word. Die data wat versamel is gedurende die proses word gebruik om die akkuraatheid van die hidrologiese modelle se resultate te bepaal. Tesame met vooruitgeskatte klimaatdata kan die modelle gebruik word om die impak van klimaatsverandering op grondwater toestande vas te stel.
Die navorsing toon die komplekse interaksie tussen verskillende prosesse in die hidrologiese sisteem. By elke punt in die landskap dra verskillende komponente op verskillende skale by tot die hidrologiese sisteem. Grondeienskappe het die meeste invloed op die verskillende komponente van die hidrologiese sisteem en beïnvloed die infiltrasie, oppervlak afloop, laterale water vloei en diep dreinering. Soos die verskillende komponente se bydrae tot die hidrologiese sisteem verander, vind daar fluktuasies in die diepte van die water tafel plaas. Deur die vergelyking van gemete grondwaterinhoud teen hidrologiese model voorspelde grondwaterinhoude, is akkurate hidrologiese modelle opgestel vir verskillende punte in die landskap. Deur gebruik te maak van twee moontlike verwagte klimaat toestande, is gevind dat droogtes op ‘n roetine basis in die toekoms sal voorkom. Die navorsing maak dit moontlik om die beweging van water deur die landskap te verstaan en dra by tot die opstelling van toekomstige waterbestuur planne. Dit word moontlik gemaak deur die vooruitskatting van grondwater inhoude gebasseer op verwagte klimaatsveranderinge en huidige grondwater toestande. / Water Research Commission
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A study of the interaction between vine vigour, crop level and harvest dates and their effects on grape and wine characteristicsQuixley, Pieter C 03 1900 (has links)
Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / A common phenomenon in most South African vineyards, especially in the Western
Cape region, is that of within vineyard variation. This variation phenomenon is caused
by an array of controllable and non-controllable factors that interact with each other to
affect vine vigour. Controllable factors can be managed by the grape grower, while the
non-controllable factors have to be managed in the planning process in order not to
negatively affect productivity or product quality.
The main goal of any grape grower is to optimise vine performance in an attempt to
achieve the best possible yield while at the same time allowing vines to optimally ripen
grapes towards optimal wine quality. A grape grower has to use every possible means
and technique available to him in order to manage his vineyards in such a manner as to
achieve this goal. In the past, it was difficult to visualize the extent and distribution of
vigour variation in vineyards, but with modern technological improvements in the field of
remote sensing, grape growers are able to identify and specify different vigour levels
within a vineyard.
When remote sensing is applied in a vineyard, the grape grower can identify certain
areas that may need more specific attention than others. Consequently, managerial
decisions based on detailed information can be made in an attempt to improve the
general condition and performance of a vine. Not only can the acquired information be
used to plan managerial actions throughout the season, but it can also be used to plan
and devise harvest strategies. Some areas in a vineyard may be at a certain point in the
ripening process and need to be harvested, while grapes from other areas still need to
develop the wanted flavours. One managerial action applied at véraison by some grape
growers, is that of crop thinning. Different vigour areas can now be subjected to various
crop thinning actions in an attempt to determine the best crop load for a vigour level.
With this in mind, two studies were launched to firstly investigate the interaction
between vine vigour and harvest dates; and secondly to investigate the interaction
between vine vigour and crop load and how their combined interaction might influence a
vine’s characteristics, grape composition and wine quality. Vigour variation was firstly
identified through multispectral aerial imagery, and then visually verified by visits to the
experimental vineyards. The multispectral aerial image was then “orthorectified” in order
to produce a classified multispectral image. The image was classified through different
colour codes that were assigned to the different vigour levels to clearly distinguish
between them. A series of vegetative and reproductive measurements were conducted
to try and establish if any correlations could be obtained of the interaction between vine
vigour, different harvest dates and crop loads. In order to verify differences in vine
vigour, underlying causes were also determined through soil analyses of which
chemical analysis, bulk density, porosity, as well as root penetration and distribution
were determined. Vegetative measurements that were conducted for both studies
indicated good correlations between the different vigour levels and the image
classifications. The results also identified the effect that topping (mechanical or manual) had on the main and lateral leaf areas. Reproductive measurements throughout the
season, in the form of berry sampling, showed changes in berry composition and
accentuated the effects of the different treatments, which could also be confirmed
through sensorial analysis of the wines. The results also emphasized the need to not
only make use of one of two chemical parameters to identify grape ripeness, but to
incorporate a number of parameters, such as sugar, pH and acid levels. From the
varying grape chemical characteristics, a wine style can be identified that might carry
the approval of the winemaker for the production of a specific type of wine. Soil studies
of both vineyards also gave important evidence for the causes of vigour variation.
The data collected will hopefully provide grape growers with information that will
enable them to make educated decisions concerning grape production and how vigour,
in conjunction with different harvest dates and crop loads, will enable them to produce
fruit of good quality and, so doing, improve their financial position.
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Grapevine (Shiraz/Richter 99) water relations during berry ripeningEllis, Warren 03 1900 (has links)
Thesis (MscAgric (Viticulture and Oenology))--Stellenbosch University, 2008. / The effect of various irrigation strategies on grapevine water relations during the
berry ripening period was investigated in a Shiraz/Richter 99 vineyard. Comparisons
between different irrigation strategies (full/seasonal, véraison+post véraison, post
véraison and no irrigation) were made.
During the day, the seasonally irrigated vines experienced less water stress than the
deficit treatments. Non-irrigated vines seemed to maintain higher diurnal leaf water
potentials. Lower leaf water potentials indicated lower water contents in the
vegetative and reproductive tissue. Full irrigation seemed to stimulate primary shoot
length. Longer water deficit induced earlier and more complete shoot maturation
(reserve accumulation). Re-distribution of leaf area on the shoot may occur when
vines are subjected to water deficit. Extended water deficit seemed to induce earlier and restricted water loss from vegetative tissue. The water relations were reflected in the berry size. Irrigation during ripening seemed to induce a continuation of berry water loss. Transpiration losses were apparently much higher in fully irrigated vines
whereas stomatal control efficiently maintained water relations in non-irrigated vines. Water deficit seemed to have enhanced the soluble solid accumulation. Irrigation
treatments did not seem to affect the titratable acid and pH. The post véraison
irrigation in particular seemed to favour a wide window for harvesting. Irrigation at
post véraison and especially véraison+post veraison seemed to have a greater effect
on the synthesis and extraction of phenolics, anthocyanins and tannins in the berry skins. Different irrigation strategies may affect grapes in such a way that different wine styles are obtained.
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Screening and characterisation of wine related enzymes produced by wine associated lactic acid bacteriaMtshali, Phillip Senzo 03 1900 (has links)
Thesis (Msc (Viticulture and Oenology))--University of Stellenbosch, 2007. / Among the factors contributing to wine complexity and quality, wine aroma is one of the
most important factors. Wine aroma is the outcome of interaction among different
compounds produced from the grapes, during fermentation as well as during the ageing
process. Apart from its origin from grapes, fungi and yeasts, wine aroma can also be
derived from the metabolic activity of wine lactic acid bacteria (LAB). These
microorganisms are usually associated with malolactic fermentation (MLF) which normally
occurs after alcoholic fermentation. MLF is beneficial to wine due to its contribution to
deacidification, microbiological stabilisation and wine aroma formation, with the latter being
the most important area of interest in our study. The production of volatile aromatic
components in wine can, in part, be achieved through the hydrolytic action of enzymes
produced by LAB associated with wine. These enzymes include β-glucosidase, protease,
esterase, lipase and glucanase. Most of the work done on bacterial enzymes has been on
LAB from food sources other than wine, in which these enzymes contribute to the flavour
development of some cheeses, yoghurt and other fermented foods. The activity of these
enzymes during wine fermentation has mostly been concerned with β-glucosidase from
Oenococcus oeni. Only in recent years has there been a renewed interest in evaluating
the activity of β-glucosidase in other genera of wine LAB.
The overriding goal of this study was to screen and characterise wine-related enzymes
produced by LAB associated with wine. All the LAB isolates tested in this study were
obtained from IWBT culture collection and were previously isolated from five different
wineries situated in the Western Cape region, South Africa. We first screened isolates
using classical methods. The isolates were grown on agar medium supplemented with
appropriate substrate analogues in order to evaluate the activity of enzymes (i.e. β-
glucosidase, glucanase, lipase and esterase). The colonies exhibiting enzymatic activity ...
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Evaluating the effect of different winemaking techniques on ethanol productionBiyela, Busisiwe Nokukhanya E. 12 1900 (has links)
Thesis (MscAgric (Viticulture and Oenology))--Stellenbosch University, 2008. / Over the years, different techniques have been used to legally reduce the ethanol content of
wines. Several physical processes are available for producing wines with less alcohol. Despite
their efficacy, these treatments have a capital and operational cost influence. They can also
affect the concentration of other wine components. On the other hand, vast amount of research
has been conducted through genetic modification of wine yeast strains in order to reduce the
ethanol yield of Saccharomyces cerevisiae by diverting sugar metabolism towards various byproducts.
However, genetically modified yeasts are not currently accepted in most wine
industries worldwide, including South Africa. Therefore, other approaches need to be
envisaged.
Commercial enzymes are commonly added during winemaking. Most enzymes essential for
vinification naturally occur in grapes, but are inefficient under pH and sulphur levels associated
with winemaking. Enzymes of fungal origin are resistant to such conditions. The most widely
used commercial enzymes include pectinases, hemicellulases, glucanases and glycosidases.
With the exception of glucanases, produced by Trichoderma harzianium, all the other enzymes
are produced by Aspergillus niger.
In this study, the possibility of using Gluzyme Mono® 10.000 BG (Gluzyme) (Novozymes,
South Africa) to reduce the glucose content of synthetic grape must and grape must before
fermentation in order to produce wine with a reduced alcohol content was investigated.
Gluzyme is a glucose oxidase preparation from Aspergillus oryzae, currently being used in the
baking industry. Glucose oxidase catalyses the oxidation of glucose to gluconic acid and
hydrogen peroxide in the presence of molecular oxygen.
Gluzyme was initially used in synthetic grape must where different enzyme concentrations
and factors influencing its activity were investigated for its use in winemaking. The results
showed that up to 0.5% v/v less alcohol were obtained using an enzyme concentration of 20 kU
compared to the control. This reduction in alcohol was increased to 1 and 1.3% v/v alcohol at
pH 3.5 and pH 5.5 respectively in aerated synthetic grape must using 30 kU enzyme.
Secondly, Gluzyme trials were carried out using Pinotage grape must. Gluzyme treated
wines after fermentation contained 0.68% v/v less alcohol than the control samples at 30 kU
enzyme. Colour and volatile flavour compounds of treated wine did not differ significantly from
the untreated samples. Lower free anthocyanin and total phenol concentrations in treated than
control samples were observed, possibly due to the hydrogen peroxide oxidation which could
have led to polymerisation.
The present study has clearly demonstrated that Gluzyme may be used in winemaking to
produce reduced-alcohol wine without affecting its colour and aroma compounds. The enzyme
in its current form is however, not ideal for winemaking; other forms such as liquid or powder
form should be considered if the enzyme is to be used under winemaking conditions.
Future work should focus on evaluating the potential new form of the enzyme and studying
the effects of Gluzyme in various grape must in semi-industrial scale. A tasting panel should
also evaluate its impact on the organoleptic properties and the overall quality of the resulting wines.
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