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Background The Kei apple is a tree found on the African continent. Limited information exists on the effect of alcoholic and acetous fermentation on the phytochemicals of Kei apple. The fruit has increased concentrations of l-malic, ascorbic, and phenolic acids among other compounds. Juice was co-inoculated with Schizosaccharomyces pombe (Sp) and Saccharomyces cerevisiae (Sc) to induce alcoholic fermentation (AF). Acetous fermentation followed AF, using an acetic acid bacteria (AAB) consortium. Results Saccharomyces cerevisiae + Sp wines and vinegars had the highest pH. Total acidity, soluble solids and l-malic acid decreased during AF and acetous fermentation, and was highest in Sc wines and vinegars. Volatile acidity (VA) concentration was highest in Sp vinegars but was not significantly different from Sc and Sc + Sp vinegars. Gallic acid was highest in Sp wines and vinegars, whereas syringic acid was highest in Sc wines and vinegars. The Sc + Sp wines were highest in caffeic, p-coumaric, and protocatechuic acids. Schizosaccharomyces pombe vinegars were highest in caffeic and p-coumaric acids. Highest concentrations of ferulic and sinapic acids were found in Sp and Sc wines, respectively. Chlorogenic acid was most abundant phenolic acid in both wines and vinegars. Conclusion Saccharomyces cerevisiae + Sp and Sc fermentation had a positive effect on most phenolic acids; Sc + AAB had an increased effect on syringic and chlorogenic acids, whereas Sp + AAB resulted in an increase in gallic, caffeic, and p-coumaric acids. The AAB selected had minimal performance with respect to VA production in comparison to commercial vinegars. Acetic acid bacteria selection for acetous fermentation should therefore be reconsidered and the decrease of certain phenolic acids during acetous fermentation needs to be investigated. © 2021 Society of Chemical Industry.

Syrah must was co-inoculated with mixed cultures of Saccharomyces + O. oeni/Lb. plantarum and Saccharomyces + non-Saccharomyces + O. oeni/Lb. plantarum to evaluate the effect on phenolics and sensory attributes. Reference wines were produced by S. cerevisiae. Malvidin-3-O-glucoside, flavan-3-ols, flavonols and phenolic acids were quantified using a RP-HPLC technique. Physicochemical characteristics and sensory attributes were measured. Total acidity and alcohol in mixed co-inoculations were different from reference wines. The concentration of l-malic acid was 7-times less in mixed co-inoculations. Mixed co-inoculations had ca. 1.3-times more malvidin-3-O-glucoside and phenolic acids than reference wines. Flavan-3-ols and flavonols were not different between mixed co-inoculations and reference wines. Acidity and astringency were least in mixed co-inoculations. Mouthfeel and bitterness least in S. cerevisiae wines. Tasters preferred mixed co-inoculated wines. Mixed co-inoculation is a strategy to contemplate for Syrah vinification but the modalities of inoculation need further investigation. Success depends on a suitable combination of yeast/bacteria and consideration of strain variation. Keywords: Co-inoculation, Hanseniaspora uvarum, Lactobacillus plantarum, Metschnikowia pulcherrima, Oenococcus oeni, Phenolics, Saccharomyces cerevisiae, Syrah

Grapes and wine contain phenolics divided into non-flavonoid and flavonoid classes. Yeast modulates the phenolics of wine by adsorption onto yeast cell walls. This may be advantageous for colour and quality. The effect of Torulaspora delbrueckii (654M2/1) and Saccharomyces cerevisiae (VIN13) on phenolics and sensory attributes of Cabernet Franc wines (2012/2013) were evaluated. Spectrophotometric analysis was used to determine the phenolic content. Sensory analysis was conducted by expert tasters to evaluate the wines. ANOVA showed that polyphenols and anthocyanins were higher in M2/1 + VIN13 wines (2012/2013) than 654 + VIN13 wines. Colour, fruitiness, mouthfeel, sweetness, astringency and quality were different between treatments. 654 + VIN13 wines (2012) were higher in polyphenols, acidity, astringency and mouthfeel than M2/1 + VIN13 wines. M2/1 + VIN13 (2012/2013) had increased colour and quality than 654 + VIN13 wines. Two treatments were identified for Cabernet Franc wines; M2/1 + VIN13 and 654 + VIN13, which resulted in wines with increased colour and wines with increased mouthfeel and astringency, respectively.

The non-Saccharomyces yeast Torulaspora delbrueckii contributes positively to the sensory properties of wines by affecting aroma and flavour due to changes in alcohols, esters, fatty acids and lactone levels. One of the less-studied aspects of T. delbrueckii is its effect on phenolic compounds relating to sensory attributes. An HPLC-DAD technique was used for the quantification of phenolic compounds in Chenin blanc wines made with S. cerevisiae and two T. delbrueckii yeasts over three vintages. Chemical and sensory data were subjected to ANOVA and PCA. VIN13, M2/1 and VIN13+M2/1 had a positive effect on the phenolic compound concentrations of Chenin blanc wines. Mouthfeel was highest in VIN13+654 wines and astringency highest in VIN13 wines. An association was evident between flavanols, astringency and mouthfeel for the VIN13, M2/1 and VIN13+M2/1 wines. Chenin blanc wines made with M2/1 and VIN13+M2/1 may result in increased phenolic compound concentrations and astringency, whereas 654 and VIN13+654 may result in wines with increased mouthfeel properties.

Wine consumers predominantly use visual, sensory and textual descriptors as quality/preference indicators to describe olfactory sensations. In this study, different wines were analysed to generate relevant chemical and sensory characterisation data and attributes. Sequential inoculation of Syrah grape must was performed with a combination of Saccharomyces yeast, non-Saccharomyces yeasts and lactic acid bacteria for the possible improvement of Syrah wine quality. Selected anthocyanins, flavan-3-ols, flavonols and phenolic acids were quantified in Syrah wines using the reversed-phase high-performance liquid chromatography photodiode array detection (RP-HPLC-DAD) technique. Sensory (descriptive evaluation) and physicochemical/oenological parameters (Winescan® and OenoFoss™) results were compared to phenolic compound concentrations. Phenolic compound concentrations increased in Syrah wines made with a combination of a Saccharomyces reference yeast, non-Saccharomyces yeasts and lactic acid bacteria. Syrah wines made with a combination of Metschnikowia pulcherrima + Saccharomyces cerevisiae + Oenococcus oeni, and M. pulcherrima + S. cerevisiae + Lactobacillus plantarum, had higher flavonol concentrations compared to wines made without lactic acid bacteria. Syrah wines made with a combination of Saccharomyces cerevisiae (Sc) + Oenococcus oeni (LAB1) were highest in phenolic acid concentrations. Syrah wines made with a combination of M. pulcherrima + S. cerevisiae + L. plantarum had higher total anthocyanins than wines made without lactic acid bacteria. Syrah wine sensory attributes, viz. mouthfeel and astringency, correlated with a combination of lactic acid bacteria and yeast treatments. Syrah wines made with a combination of yeast and lactic acid bacteria (LAB) scored highest in overall quality. Indications are that the S. cerevisiae reference yeast retained more phenolic compounds during fermentation when compared to wines made with a combination of non-Saccharomyces yeasts and LAB. The improved red colour of Syrah wines may be achieved by sequential inoculation with non-Saccharomyces yeast and LAB. This could be beneficial where winemakers use grape cultivars with low anthocyanin levels in the grape skin to produce wines of improved quality.

Pinotage and Cabernet franc grape must were inoculated with Saccharomyces cerevisiae and Torulaspora delbrueckii yeasts. Differences in colour were observed between Pinotage (S. cerevisiae) and Pinotage (T. delbrueckii) wines, whereas differences in berry and herbaceous character were observed between Cabernet franc (S. cerevisiae) and Cabernet franc (T. delbrueckii) wines. Mouthfeel properties between treatments for both wines were not significantly different. Overall quality was slightly higher in wines inoculated with T. delbrueckii compared to wines inoculated with S. cerevisiae. Anthocyanins and flavanols measured in Pinotage wines made with T. delbrueckii were higher compared to Pinotage must inoculated with S. cerevisiae. Cabernet franc wines made with S. cerevisiae were higher in anthocyanin glycoside and flavanol concentrations compared to Cabernet franc wines made with T. delbrueckii. Insignificant differences in acetylated and coumarylated anthocyanins were evident between Cabernet franc (S. cerevisiae) and Cabernet franc (T. delbrueckii) wines. Principal component analysis showed that epigallocatechin gallate, epicatechin gallate, procyanidin B2, peonidin 3-O-glucoside, delphinidin 3-(6-acetyl) glucoside, petunidin 3-(6-acetyl) glucoside, malvidin 3-(6-acetyl) glucoside and malvidin 3-O-glucoside concentrations were highest in Pinotage wines inoculated with T. delbrueckii. Cabernet franc wines inoculated with S. cerevisiae yeasts were highest in malvidin 3-(6-p-coumaroyl) glucoside, petunidin 3-(6-p-coumaroyl) glucoside, petunidin 3-O-glucoside, epicatechin gallate and epigallocatechin gallate concentrations. Total anthocyanins were highest in Pinotage (S. cerevisiae) wines and Cabernet franc (T. delbrueckii) wines. Flavanols were highest in Pinotage (T. delbrueckii) and Cabernet franc (S. cerevisiae) wines. It is evident from the results that yeast species has an impact on the flavonoid concentrations within a grape variety.

A simple isocratic high-performance liquid chromatographic (HPLC) method for the quantitative analysis of monofluoroacetic acid (MFA), the toxic substance of Dichapetalum cymosum, in plant material, rumen contents (gastric contents), and liver samples is described. A suitable HPLC column that gives optimum sensitivity, accuracy, precision, and separation of MFA is identified. A C-610 organic acid analysis column at ambient temperature with 0.02M H3PO4 as an eluent and ultraviolet detection at 210 nm is utilized to quantitate MFA. Using this method, the average percentage recovery in plant material, bovine liver, and rumen samples is 94.8%, and a detection limit of 12 microg/L is achievable.