The role of lactic acid bacteria in brandy production

Du Plessis, Heinrich Wilbur,1975- (2002-12)

Thesis (MSc)--University of Stellenbosch, 2002.

Thesis

ENGLISH ABSTRACT: The presence and growth of lactic acid bacteria (LAB) in wine and their influence on wine quality has received much attention in recent years. Lactic acid bacteria are responsible for conducting malolactic fermentation (MLF) in wine. The benefits associated with malolactic fermentation in terms of deacidification of wine and the contribution to wine flavour and complexity have also recently been the topic of research. It is impossible to describe malolactic fermentation as distinctly desirable or undesirable in terms of its influence on the final quality of wine. The benefits and disadvantages are dependent upon viticultural region, grape variety, wine composition, winemaking techniques and the style and objectives of the winemaker. Brandy production is a multi-stage process in which base wine production, distillation technique and wood maturation all have a large influence on the final chemical profile and organoleptic quality of the brandy. The volatile composition of the base wine, which basically undergoes a concentration process during the subsequent double distillation phase, is critical in determining the aroma and flavour quality of the final brandy product. Thus, the brandy is only as good as the base wine it is distilled from. The aims of this study were to determine the effect of lactic acid bacteria and spontaneous malolactic fermentation on the quality of brandy base wine and the resulting distillate, and to determine which LAB species had been responsible for the occurrence of spontaneous MLF. This study showed that LAB are present at high numbers and are able to conduct spontaneous MLF of brandy base wines. It was shown that the incidence of spontaneous MLF varied from year to year. In 1998, 50% of the commercially produced base wines had undergone partial MLF prior to distillation. In 1999 and 2000 respectively, 34% and 45% of the commercial base wines had undergone partial MLF prior to distillation. The occurrence of spontaneous MLF had an influence on the chemical composition and the sensory quality of the base wine and distillate. There was an increase in the concentrations of ethyl lactate, acetic acid and diethyl succinate in samples that had undergone MLF. There was also a decrease in the concentrations of esters, such as iso-amyl acetate, ethyl acetate, ethyl caproate, hexyl acetate and 2-phenethyl acetate in these same samples. Sensory evaluation of the base wines and distillates demonstrated that samples that had undergone MLF differed significantly from samples that had not undergone MLF. It was also shown that distillates that had not undergone MLF had a slightly better aroma profile than those that had. Sweet aromas, like chocolate and caramel, as well as negative aromas, like chemical or solvent, were more prominent in brandy distillates that had undergone MLF. Herbaceous and fruity aromas were more intense in distillates not having undergone MLF. Fifty-four strains, all Gram-positive and catalase negative, were isolated at different stages of brandy production. Seven strains were isolated from the grape juice, 15 strains were isolated from the base wine, 20 strains were isolated during MLF and 12 strains were isolated from the base wine after MLF had been completed. Based on C02 production from glucose and gluconate, 17 strains were classified as facultatively heterofermentative and 37 strains as obligately heterofermentative. Fifteen of the 37 obligately heterofermentative strains were rod-shaped and were regarded as lactobacilli. The remaining 22 strains were oval or cocci-bacilli shaped. The isolates were identified to species level by using numerical analysis of the total soluble cell protein patterns, 16S rRNAsequencing and polymerase chain reaction (PCR) with species-specific primers. The facultative heterofermentative lactobacilli were identified as Lactobacillus paracasei and Lactobacillus p/antarum. The fifteen obligately heterofermentative lactobacilli were identified as members of the species Lactobacillus brevis, Lactobacillus verrniforme, Lactobacillus buchneri and Lactobacillus hi/gardii. The 22 obligate heterofermentative isolates, with a coccoid morphology, could be grouped into two clusters and were identified as Oenococcus oeni. O. oeni was the species responsible for the occurrence of spontaneous MLF in most of the commercial base wines. Lb. brevis, Lb. hi/gardii and Lb. paracasei were also isolated from commercial base wines that had undergone spontaneous MLF. In nine out of 14 experimental base wine samples that had undergone spontaneous MLF, O. oeni was again the predominant species. Lb. brevis, Lb. hi/gardii and Lb. paracasei were identified in the remaining experimental base wine samples. This is the first report of the presence of Lb. perecese! and Lb. vermiforme in brandy base wine. It was shown that the occurrence of spontaneous MLF had a negative effect on the quality of brandy base wine, but that was shown to be due to the different species and strains performing MLF. In the non-preferred distillate samples, Lactobacillus spp. had performed MLF or had developed after or during MLF.

AFRIKAANSE OPSOMMING: Die teenwoordigheid en die vermoë van melksuurbakterieë (MSB) om in wyn te groei, is 'n onderwerp wat al heelwat nagevors is. Melksuurbakterieë is verantwoordelik vir die uitvoering van appelmelksuurgisting (AMG) in wyn. Die voordele verbonde aan appelmelksuurgisting, ten opsigte van die verlaging van die totale suurinhoud en die bydrae tot die verbeterde geur en kompleksiteit van die wyn, is ook al goed bestudeer. Wat die invloed op die finale wynkwaliteit betref, is dit byna onmoontlik om AMG as uitsluitlik gewens óf ongewens te beskou. Die voordele en nadele van AMG is afhanklik van verskeie faktore, nl. wingerdkundige streek, druifkultivar, wynsamestelling, wynmaakpraktyke, asook die styl en doelwitte van die wynmaker. Die produksie van brandewyn is 'n multistapproses waarin die bereidingsmetode van die basiswyn, die distillasietegniek en houtveroudering 'n groot invloed op die finale kwaliteit en chemiese samestelling van die brandewyn het. Die vlugtige verbindings van die basiswyn, wat tydens die dubbele distillasieproses gekonsentreer word, is van wesenlike belang in die bepaling van die aroma en geur van die finale brandewynproduk. Brandewyn is dus inderdaad net so goed soos die basiswyn waarvan dit gestook is. Die doelwitte van hierdie studie was om te bepaal wat die invloed van MSB en die voorkoms van spontane AMG op die kwaliteit van die basiswyn en die distillaat is, asook om die MSB wat vir die voorkoms van spontane AMG verantwoordelik was, te identifiseer. Hierdie studie het bewys dat MSB in hoë getalle teenwoordig was en dat dit in staat is om die spontane AMG van basiswyne uit te voer. Daar is bewys dat die voorkoms van spontaneAMG moontlik van jaar tot jaar kan verskil. In 1998 het 50%, in 1999 het 34% en in 2000 45% van die kommersieel-geproduseerde basiswyn gedeeltelike AMG spontaan voor distillasie ondergaan. Daar is ook gevind dat spontane AMG 'n invloed op die chemiese samestelling en sensoriese kwaliteit van die basiswyn en die distillaat gehad het. Daar was 'n toename in die konsentrasies van etiellaktaat, asynsuur en diëtielsuksinaat in monsters wat spontane AMG ondergaan het. In dieselfde monsters was daar ook 'n afname in die konsentrasies van iso-amielasetaat, etielasetaat, etielkaproaat, heksielasetaat en 2-fenielasetaat. Sensoriese evaluering van die basiswyne en distillate het getoon dat daar betekenisvolle verskille was tussen die monsters wat AMG ondergaan het en dié wat nie AMG ondergaan het nie. Daar is bewys dat die distillate wat nie AMG ondergaan het nie, 'n beter aromaprofiel gehad het as dié wat AMG ondergaan het. Soet geure, soos sjokolade en karamel, en negatiewe geure, soos "chemies" en "oplosmiddel", was prominent in distillate wat AMG ondergaan het. Kruidagtige en vrugtige geure was meer intensief in distillate wat nie AMG ondergaan het nie. Vier-en-vyftig bakteriese rasse, almal Gram-positief en katalase-negatief, is gedurende die verskillende stadia van brandewynproduksie geïsoleer. Sewe rasse is uit druiwesap, 15 rasse gedurende die alkoholiese fermentasie, 20 rasse gedurende AMG en 12 rasse na voltooiing van AMG geïsoleer. Op die basis van koolstofdioksied (C02)-produksie vanaf glukose en glukonaat is 17 rasse as fakultatief heterofermentatief en 37 rasse as obligaat heterofermentatief geklassifiseer. Vyftien van die 37 obligaat-heterofermentatiewe rasse was staafvormig en is as lactobacilli geïdentifiseer. Die oorblywende 22 het ovaal of kokkus-bacillusvormige selmorfologie getoon. Identifikasie tot op spesievlak is gedoen deur van numeriese analise van die totale oplosbare selproteïenprofiele, 16S-rRNAvolgordebepalings en spesie-spesifieke inleiers vir die polimerasekettingreaksie (PKR) gebruik te maak. Die fakultatief-heterofermentatiewe rasse is as Lactobacillus paracasei en Lactobacillus p/antarum geklassifiseer. Die 15 obligaat heterofermentatiewe stafies is as Lactobacillus brevis, Lactobacillus buchneri, Lactobacillus hi/gardii en Lactobacillus vermiforme geïdentifiseer. Die 22 ovaal, obligaat heterofermentatiewe isolate kon in twee groepe ingedeel word en is as Oenococcus oeni geïdentifiseer. Daar is bevind dat O. oeni-isolate vir die voorkoms van spontane AMG in die meeste van die kommersiêle basiswyne verantwoordelik was. Lb. brevis, Lb. hi/gardii en Lb. paracasei is ook uit kommersiêle basiswyne wat spontane AMG ondergaan het, geïsoleer. In nege uit 14 van die eksperimentele basiswyne wat spontane AMG ondergaan het, was O. oeni die dominante spesie. In die oorblywende eksperimentele wyne is Lb. brevis, Lb. hi/gardii en Lb. paracasei aangetref. Hierdie is die eerste vermelding van die teenwoordigheid van Lb. paracasei and Lb. vermiforrne in brandewynbasiswyn. Daar is gevind dat die voorkoms van spontane AMG "n negatiewe invloed op brandewynkwaliteit het, maar dit is as gevolg van die verskeidenheid van MSB-spesies en rasse wat voorkom. In die distillate wat deur die proepaneel afgekeur is, het Lactobacillus spesies die AMG deurgevoer, of het dit tydens of na AMG ontwikkel.

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