Effect of non-Saccharomyces yeasts and lactic acid bacteria interactions on wine flavour.

Du Plessis, Heinrich Wilbur (2018-03)

Thesis (PhD)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Wine aroma and flavour are important indicators of quality and are primarily determined by the secondary metabolites of the grape, by the yeast that conducts the primary fermentation and also the lactic acid bacteria (LAB) that performs malolactic fermentation (MLF). This is a complex environment and each microorganism affects the other during the wine production process. Therefore, the overall aim of this study was to investigate the interactions between Saccharomyces, non-Saccharomyces yeasts and LAB, and the effect these interactions had on MLF and wine flavour. Contour-clamped homogeneous electric field gel electrophoreses (CHEF) and matrix-assisted laser desorption ionization using time-of flight mass spectrometry (MALDI-TOF MS) were useful tools for identifying and typing of Hanseniaspora uvarum, Lachancea thermotolerans, Candida zemplinina (synonym: Starmerella bacillaris) and Torulaspora delbrueckii strains. Hanseniaspora uvarum strains had β-glucosidase activity and Metschnikowia pulcherrima strains had β-glucosidase and protease activity. Only Schizosaccharomyces pombe and C. zemplinina strains showed mentionable malic acid degradation. Candida stellata, C. zemplinina, H. uvarum, M. pulcherrima and Sc. pombe strains were slow to medium fermenters, whereas L. thermotolerans and T. delbrueckii strains were found to be medium to strong fermenters, comparable to S. cerevisiae. The effect of non-Saccharomyces yeast species on MLF varied and inhibition was found to be strain dependent. In a Shiraz winemaking trial where seven non-Saccharomyces strains were evaluated in combination with S. cerevisiae and three MLF strategies, the C. zemplinina and the one L. thermotolerans isolate slightly inhibited LAB growth in wines where yeast and LAB were inoculated simultaneously. However, the same effect was not observed during sequential inoculation of LAB. Mixed culture fermentations using non-Saccharomyces yeasts contained lower alcohol levels, and were more conducive to MLF than wines produced with S. cerevisiae only. Yeast treatment and MLF strategy resulted in wines with significantly different flavour and sensory profiles. Yeast selection and MLF strategy had a significant effect on berry aroma, but MLF strategy also had a significant effect on acid balance and astringency of wines. In a follow up trial, H. uvarum was used in combination with two S. cerevisiae strains, two LAB (Lactobacillus plantarum and Oenococcus oeni) species and three MLF strategies. One of the S. cerevisiae strains had an inhibitory effect on LAB growth, while H. uvarum in combination with this S. cerevisiae strain had a stimulatory effect on MLF. Simultaneous MLF completed faster than sequential MLF and wines differed with regard to their chemical and sensory characteristics. Isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl-3-hydroxybutanoate, ethyl phenylacetate, 2-phenyl acetate, isobutanol, 3-methyl-1-pentanol, hexanoic acid and octanoic acid were important compounds in discriminating between the different wines. Yeast treatment had a significant effect on fresh vegetative and spicy aroma, as well as body and astringency of the wines. The LAB strain and MLF strategy had a significant effect on berry, fruity, sweet associated and spicy aroma, as well as acidity and body of the wines. Mid-infrared (MIR) spectroscopy was used to differentiate between wines produced with the selected Saccharomyces and non-Saccharomyces yeast combinations, LAB species and MLF strategies. This study provides valuable information about the interactions between non-Saccharomyces, Saccharomyces yeast, LAB and MLF strategies, and how important pairing of strains are to ensure successful AF and MLF. Furthermore, the results also showed how these interactions can be applied to diversify wine flavour.

AFRIKAANSE OPSOMMING: Wynaroma en geur is belangrike aanwysers van kwaliteit en word hoofsaaklik bepaal deur die sekondêre metaboliete van die druif, deur die gis wat die alkoholiese gisting uitvoer en ook deur die melksuurbakterieë (MSB) wat appelmelksuurgisting (AMG) uitvoer. Die omgewing tydens wynproduksie is kompleks en elke mikroörganisme beïnvloed die ander. Die oorhoofse doel was om die interaksies tussen Saccharomyces, nie-Saccharomyces giste en MSB te ondersoek en om te bepaal watter effek hierdie interaksies op AMG en wynaroma het. Kontoer toegeslane homogene elektriese veld gel elektroforese (KHEV) en matriks geassosieerde laser desorpsie ionisasie met tyd van vlug massa spektrometrie (MALDI-TVV MS) was nuttige tegnieke om Hanseniaspora uvarum, Lachancea thermotolerans, Candida zemplinina (sinoniem: Starmerella bacillaris) en Torulaspora delbrueckii rasse te identifiseer en te karakteriseer. Hanseniaspora uvarum rasse het β-glukosidase aktiwiteit getoon en Metschnikowia pulcherrima rasse het β-glukosidase en protease aktiwiteit gehad. Slegs Schizosaccharomyces pombe en C. zemplinina rasse het noemenswaardige appelsuur afbraak getoon. Candida stellata, C. zemplinina, H. uvarum, M. pulcherrima and Sc. pombe rasse was stadig tot middelmatige fermenteerders, maar L. thermotolerans and T. delbrueckii rasse was middelmatige tot sterk fermenteerders en vergelykbaar met S. cerevisiae. Die effek wat nie-Saccharomyces gisspesies op die verloop van AMG gehad het, het gevarieer en inhibisie was ras afhanklik. Vir die Shiraz wynmaak proef waar sewe nie-Saccharomyces rasse in kombinasie met ‘n S. cerevisiae en drie AMG strategieë geëvalueer is, het die C. zemplinina en die een L. thermotolerans isolaat MSB groei effens geïnhibeer, toe die gis en MSB gelyktydig bygevoeg was. Dieselfde effek was nie by wyne wat opvolgende AMG ondergaan het, waargeneem nie. Gemengde fermentasies deur van nie-Saccharomyces giste gebruik te maak, het laer alkoholvlakke getoon en was meer bevorderlik vir AMG as wyne waar net S. cerevisiae gebruik is. Gisbehandeling en AMG strategie het wyne geproduseer wat betekenisvol verskil het in hul geur en sensoriese profiele. Gisseleksie en AMG strategie het ‘n betekenisvolle effek op bessie aroma gehad, maar AMG strategie het ook ‘n betekenisvolle effek op suurbalans en vrankheid van wyne gehad. In ‘n opvolgende proef, was H. uvarum gebruik in kombinasie met twee S. cerevisiae rasse, twee MSB spesies (Lactobacillus plantarum en Oenococcus oeni) en drie AMG strategieë. Een van die S. cerevisiae rasse het ‘n inhiberende effek op MSB groei gehad, terwyl hierdie S. cerevisiae ras in kombinasie met H. uvarum ‘n stimulerende effek op AMG getoon het. Appelmelksuurgisting was vinniger voltooi in wyne wat gelyktydige AMG ondergaan het as wyne wat opvolgende AMG ondergaan het en die wyne het ook verskil ten opsigte van chemiese en sensoriese eienskappe. Isoamielasetaat, etielheksanoaat, etieloktanoaat, etiel-3-hydroksibutanoaat, etielfenielasetaat, 2-fenielasetaat, isobutanol, 3-metiel-1-pentanol, heksanoeësuur en oktanoeësuur was belangrike verbindings wat gebruik is om tussen die wyne te onderskei. Gisbehandeling het ‘n betekenisvolle effek op vars vegetatiewe en spesery aromas gehad, sowel as mondgevoel en vrankheid van die wyne. Die MSB ras en AMG strategie het ‘n betekenisvolle effek op bessie, vrugtig, soet geassosieerde en spesery aromas, sowel as suurbalans en mondgevoel van wyne gehad. Mid-infrarooi spektroskopie was gebruik om tussen wyne wat met die geselekteerde Saccharomyces en nie-Saccharomyces giskombinasies, MSB spesie en AMG strategieë geproduseer is, te onderskei. Hierdie studie verskaf waardevolle inligting oor die interaksies tussen nie-Saccharomyces, Saccharomyces giste, MSB en AMG strategieë, en hoe belangrik die regte kombinasies is vir suksesvolle alkoholiese gisting en AMG. Verder het resultate ook gewys hoe bogenoemde interaksies toegepas kan word om wyngeur te diversifiseer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103673
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