Fermentation of grape must by sequential association of yeasts: Accumulation of pyruvic and α-ketoglutaric acid

Fermentations of grape (cv. Malvar) musts from two consecutive vintages were carried out using the autochthonous microflora, a sequential association of yeasts and conventional fermentations with addition of sulfur dioxide to the must. The pyruvic and α-ketoglutaric acid content over the course of fermentation was measured and showed that for both vintages tested the maximum accumulation of the ketoacid pyruvic acid took place several days earlier in fermentations using a sequential association of yeasts than in conventional fermentations. The accumulation of pyruvic acid was higher in the must made from grapes with a higher degree of ripening and the lowest level of added SO₂. In the fermentations using either a sequential association of yeasts or the autochthonous microflora with no added SO₂, accumulation of α-ketoglutaric acid was higher in the must with the higher nitrogen content when the species making the greatest percentage contributions at the start of fermentation presented high levels of proteolytic activity.     

Study of the oenological characteristicsand enzymatic activities of wine yeasts

Seventy-four wine strains of theSaccharomycesgenus were tested to study their oenological characteristics and enzymatic activities. These strains were isolated from spontaneous microbiota taken from cellars in the Valdepeñas region (Spain) and identified by contour homogeneous electric field (CHEF) technique. When Cluster Analysis was applied to oenological properties, only SH₂production, tolerance to 12⁰of ethanol and synthesis of killer toxin contributed to the distribution of the strains in the different statistical groups. All the strains possessed esterase activity and some also showed protease and pectinase activities. None of them hadβ-D-glucosidase activity.     

Decomposition of L-malic acid by wine yeasts

46 yeasts from 5 genera were examined for ability to decompose L -malic acid in grape juice. Saccharomyces yeasts decomposed between 3 and 45%, the amount decomposed being somewhat greater in highly acid juice. Schizosaccharomyces malidevorans brought about complete decomposition with stoicheiometric yield of ethanol. Pichia and Candida growing as oxidative films also brought about some decomposition. Mixed cultures of Saccharomyces and Schizosuccharomyces were examined quantitatively. The difference between yeast and bacterial decomposition of L-malic acid is discussed, as well as the possible selection of yeast cultures for controlled deacidification in wine-making.     

Glycosylation of human α1-antitrypsin in Saccharomyces cerevisiae and methylotrophic yeasts

Human α₁-antitrypsin (α₁-AT) is a major serine protease inhibitor in plasma, secreted as a glycoprotein with a complex type of carbohydrate at three asparagine residues. To study glycosylation of heterologous proteins in yeast, we investigated the glycosylation pattern of the human α₁-AT secreted in the baker's yeast Saccharomyces cerevisiae and in the methylotrophic yeasts, Hansenula polymorpha and Pichia pastoris. The partial digestion of the recombinant α₁-AT with endoglycosidase H and the expression in the mnn9 deletion mutant of S. cerevisiae showed that the recombinant α₁-AT secreted in S. cerevisiae was heterogeneous, consisting of molecules containing core carbohydrates on either two or all three asparagine residues. Besides the core carbohydrates, variable numbers of mannose outer chains were also added to some of the secreted α₁-AT. The human α₁-AT secreted in both methylotrophic yeasts was also heterogeneous and hypermannosylated as observed in S. cerevisiae, although the overall length of mannose outer chains of α₁-AT in the methylotrophic yeasts appeared to be relatively shorter than those of α₁-AT in S. cerevisiae. The α₁-AT secreted from both methylotrophic yeasts retained its biological activity as an elastase inhibitor comparable to that of α₁-AT from S. cerevisiae, suggesting that the different glycosylation profile does not affect the in vitro activity of the protein. © 1998 John Wiley & Sons, Ltd.     

Effect of γ‐aminobutyric acid supplementation on the composition of Chinese rice wine

This study investigated the effect of γ‐aminobutyric acid (GABA) supplementation on the composition of Chinese rice wine. GABA was added at 188.5 and 377 mg/L at the beginning of primary fermentation or post‐fermentation. Addition of GABA during primary fermentation had no impact on alcohol and total acid formation or the utilisation of sugar. However, total free amino acids, total essential amino acids and GABA in rice wine supplemented with GABA were significantly lower than the control rice wine without supplementation. Alcohol formation, total acid, sugar content and total essential amino acids were similar compared with the control. However, the GABA post‐supplementation was significantly higher, suggesting that GABA supplementation post‐fermentation process could enhance the GABA content in rice wine. © 2018 The Institute of Brewing & Distilling     

The detection of α‐dicarbonyl compounds in wine by formation of quinoxaline derivatives

A method to determine the most abundant α‐dicarbonyl compounds in wine was developed by reaction with 2,3‐diaminobenzene. Products such as quinoxaline derivatives were detected by high‐performance liquid chromatography (HPLC) or by gas chromatography with a mass‐selective detector (GC–MS) or a thermoionic detector (GC–NPD). HPLC and detection with a spectrophotometer (313 nm) were used for routine quantitative analysis of wines. The method is sensitive, linear and has good repeatability. Diacetyl, pentane‐2,3‐dione, glyoxal and methylglyoxal were quantified in a single run; these compounds are always encountered in wines, but levels vary with different types of wine and also during fermentation and maturation processes. A new dicarbonyl compound, phenylglyoxal, was found in wine. The evolution of dicarbonyl compounds during fermentation is reported in this paper. © 2000 Society of Chemical Industry     

Mango wine aroma enhancement by pulp contact and β‐glucosidase

This study determined the influence of pulp maceration and β‐glucosidase on mango wine physico‐chemical properties and volatile profiles. The distinction in pH, sugars and organic acids among different treatments was not statistically significant. All wine samples reached around 8% (v/v) ethanol from about 16% (w/v) of sugars. The wine with pulp contact contained about ten times higher α‐terpinolene and up to three times higher acetate esters than the wine without pulp contact, but mitigated the production of medium‐chain fatty acids and relative ethyl esters by up to six times. β‐glucosidase enhanced terpenols by up to ten times and acetate esters by up to three times. Furthermore, enzyme treatment mitigated, by up to five times, the formation of medium‐chain fatty acids and ethyl esters to moderate levels. Sensory evaluation showed pulp contact, and β‐glucosidase not only improved the intensity and complexity of wine aroma but balanced odour attributes.     

Inhibition of wheat α-amylase by bran phytic acid

A proportion of the wheat samples tested for α-amylase activity by the Hagberg penetrometer method during the 1961 New Zealand harvest gave higher results on flours than on wheatmeals milled from the same wheats. This effect is due to the lower level of calcium available as enzyme cofactor in the meals, caused by combination with phytic acid. Because of this effect and because the internal distribution of α-amylase in wheat grains is variable, testing for sprout damage in milling wheat is best carried out on flours rather than wheatmeals.     

HPLC determination of γ‐aminobutyric acid in Chinese rice wine using pre‐column derivatization

γ‐Aminobutyric acid (GABA) is a major functional ingredient in Chinese rice wine. A new HPLC method for determining GABA using pre‐column derivatization with dansyl chloride was developed. The HPLC operating conditions were as follows: a Hypersil ODS2 C₁₈ column; mobile phase, methanol and water (1:1); gradient elution; absorption at 254 nm; flow rate, 1 mL/min; pH 9; and column temperature, 30 °C. Under optimal HPLC conditions, the linear equation was y = 3.5 × 10^?7x ? 0.014. The precision (relative standard deviation, RSD) was 0.54%, the stability (RSD) was 0.21%, the recovery ratio was 97.4% and reproducibility (RSD) was 1.57%. This new method appears to be sensitive, accurate, convenient, steady and relatively fast. The results suggest that the new method is also more reliable. Copyright © 2015 The Institute of Brewing & Distilling     

Evaluating potential applications of indigenous yeasts and their β‐glucosidases

The potential applications of wild yeast strains with β‐glucosidase activity were investigated by assaying their enzymatic production under simulated oenological conditions, coupled with the exploration of the potential applications of the β‐glucosidases by studying the enzymatic activity and stability under similar oenological conditions. The assay of enzymatic locations revealed that the β‐glucosidase activities from these wild strains occurred in the extracellular fraction, and in whole and permeabilized cells. The effects of different oenological factors on β‐glucosidase production indicated that the F6 Trichosporon asahii strain had higher β‐glucosidase production than the other strains under low pH conditions. However, the F35 Hanseniaspora uvarum strain and the F30 Saccharomyces cerevisiae strain showed higher β‐glucosidase production under high‐sugar conditions. Furthermore, the influence of oenological factors on the activity and stability of the β‐glucosidases revealed that the enzyme from the F6 T. asahii strain had a stronger low‐pH‐value resistance than the other yeast β‐glucosidases. These results suggest that the F35 H. uvarum, F30 S. cerevisiae and the F6 T. asahii β‐glucosidases may have some potentially applicable values in the fermentation industry. Copyright © 2015 The Institute of Brewing & Distilling     

Inhibitory activities of kaempferol,galangin, carnosic acid and polydatin against glycation and α‐amylase and α‐glucosidase enzymes

The activities of four natural phenolics, kaempferol, galangin, carnosic acid and polydatin in scavenging free radicals, inhibiting advanced glycation end‐product (AGE) formation, α‐amylase and α‐glucosidase and trapping methylglyoxal (MGO), were evaluated in this study. Carnosic acid and galangin had the highest activity in scavenging free radicals. Kaempferol and galangin had the greatest activity in preventing bovine serum albumin (BSA) against glycation and reducing glycated proteins. Polydatin had the greatest performance in trapping MGO to reduce glycation reaction. However, there was no significant difference for kaempferol, galangin and carnosic acid in inhibiting AGE formation by BSA‐MGO reaction. Kaempferol, galangin and carnosic acid were the competitive inhibitors for α‐amylase, while kaempferol and carnosic acid were noncompetitive inhibitors for α‐glucosidase. However, polydatin showed as a mixed noncompetitive inhibitor for both α‐amylase and α‐glucosidase. The results indicated that the four natural phenolics have potential in inhibiting AGE production and the digestive enzymatic activity with different mechanisms.     

Comparative study of enzymatic hydrolysis of α/β- and γ-gliadins

Enzymatic hydrolysis of proteins and fractionation of hydrolysates is a route of diversifying their functional properties. Chymotryptic hydrolysis of different sulphur-rich gliadins (α/β- and γ-types), major wheat storage proteins, was studied. The peptides formed in the course of digestion were characterised by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate (SDS-PAGE) and reversed-phase high performance liquid chromatography (RP-HPLC). With reference to previous work, a general scheme of degradation was assessed for γ-gliadins. Limited hydrolysis released two types of polypeptides, comprising respectively the repetitive and the non-repetitive moieties of the protein. In spite of strong sequence homologies between the two groups of sulphur-rich gliadins, it was not possible to prepare similar peptide fractions from α/β-gliadins. They were more resistant to hydrolysis and the region where the two domains merge appeared inaccessible to chymotrypsin. Restricted accessibility of cleavage sites was attributed to the less expanded conformation of α/β-type than γ-type gliadins. A first step of scaling-up was performed. This offers opportunities to prepare functional peptides from wheat storage proteins.     

Sweet taste and solution properties of α,α-trehalose

α,α-Trehalose, a naturally occurring non-reducing disaccharide (α, D-glucopyranosyl 1–1 α-D-glucopyranoside) is investigated by solution parameters and sensorial effects. Interactions between α, α-trehalose and water give rise to hydration effects which are measurable by intrinsic viscosity [n], apparent specific volume V°₂, and NMR relaxation times. Water-solute interactions are prime determinants of taste qualities. An interpretation of sweetness intensity and persistence of α,α-trehalose is therefore offered, based on its solution properties and its effect on water structure. From the results, it appears that α,α-trehalose undergoes a better packing among water molecules than other sugars. α,α-Trehalose is found to be less sweet but more persistent than sucrose, fructose, glucose or maltose.     

Molecular characterization and oenological properties of wine yeasts isolated during spontaneous fermentation of six varieties of grape must

Fermentation by naturally occurring yeasts may produce wines of complex oenological properties that are unique to a specific region. The present work analyses the population dynamics of the yeasts during spontaneous fermentation of six varieties of grape must from the “Valle del Andarax” area (Spain). In this study we identified members of the genera Candida, Hanseniaspora, Issatchenkia, Metschnikowia, Pichia and Saccharomyces by PCR-RFLP of the ITS region. The capability of these yeasts to ferment grape must of the Macabeo variety was studied, and the volatile profile of the wine from each microvinification has been determined. Of all the yeasts isolated Candida stellata and Saccharomyces cerevisiae were able to consume virtually all the initial glucose, producing ethanol contents typical of table wines. The best profile of higher alcohols was given by Saccharomyces cerevisiae followed by Hanseniaspora uvarum, Issatchenkia orientalis and Candida stellata. Metschnikowia pulcherrima and Pichia fermentans showed the highest production of ethyl caprilate and 2-phenyl ethanol, compounds associated with pleasant aromas.     

Formation of higher alcohols by wine yeasts,and relationship to taste thresholds

The amounts of n-propanol, iso-butanol and iso-amyl plus active amyl alcohol produced during fermentation of grape juice were found to vary considerably according to the yeast used. The yeasts studied included 11 wine yeasts and one brewery yeast, all belonging to the genus Saccharomyces, and 4 yeasts belonging to genera which sometimes cause wine spoilage. Experiments were carried out in the laboratory and confirmed on pilot-plant scale. The average production of n-propanol in juices from 4 grape varieties varied from 13 to 106 ppm depending on the wine yeast used. The corresponding variations in the production of iso-butanol and isoamyl plus active amyl alcohol were 9 to 37 ppm and 115 to 262 ppm respectively,. Juices from different varieties' of grapes (Vitis vinifera) differed somewhat in the amounts of higher alcohols formed, irrespective of the yeast strain used. An increase in temperature of fermentation from 15° to 25° with four yeasts produced an average of 24% more iso-amyl plus active alcohol and 39% more iso-butanol, and 17% less n-propanol. A yeast/temperature interaction occurred. An increase in pH from 3.0 to 4.2 with four yeasts produced 28% more iso-amyl plus active amyl alcohol, 85% more iso-butanol, and 11% more n-propanol. A yeast /pH interaction occurred. Spoilage yeasts examined also formed higher alcohols and the amounts were not related to sugar consumed during the fermentation. Taste thresholds of the higher alcohols, with the exception of active amyl alcohol, were measured in dry white wine with 7 tasters. Iso-amyl alcohol thresholds ranged from 100 to 900 ppm (mean 300 ppm) and iso-butanol and n-propanol both exceeded 500 ppm. The average threshold of iso-amyl alcohol in distilled water was 4 ppm. For certain tasters strains of yeast can produce sufficient differences in iso-amyl alcohol to be detectable organoleptically, but differences in iso-butanol and n-propanol are not large enough to be detectable.     

2种葡萄酒酵母发酵黑莓酒的降酸效果研究

研究采用反相高效液相色谱法测定两种酵母发酵的黑莓酒中主要有机酸的种类及含量,为筛选出适合黑莓酒同步发酵降酸的酵母提供依据.对61A和71A酵母发酵的黑莓酒进行RP-HPLC分析,结果表明,2种酵母发酵的黑莓酒中主要有机酸都是苹果酸,其次是酒石酸、醋酸和乳酸.与61A酵母相比,用71A酵母发酵的黑莓酒中苹果酸、酒石酸、醋酸、乳酸、草酸和琥珀酸分别下降了3.08mg/mL、0.6 mg/mL、0.64 mg/mL,、0.69mg/mL、0.3 mg/mL和0.88mg/mL,柠檬酸含量上升为0.42mg/mL,总酸降低了5.77 mg/mL,说明71A酵母在酒精发酵的同时具有较好的降酸效果,足酿造黑莓酒的良好菌株.     

Determination of γ‐aminobutyric acid in Chinese rice wines and its evolution during fermentation

γ‐Aminobutyric acid (GABA) is a functional amino acid that is widely present in Chinese rice wine. In this study, high‐performance liquid chromatography coupled with ultraviolet detection (HPLC‐UV) was established for the determination of γ‐aminobutyric acid in 22 Chinese rice wines collected from the Shaoxing region of China. Furthermore, the evolution of GABA was studied in Chinese rice wine during primary and post‐fermentation process. Results showed that the HPLC method was reliable with good linearity, accuracy, precision and stability. Additionally, the GABA content varied significantly in the 22 Chinese rice wines, and the content was much higher in wine samples with long aging periods. Regarding the evolution of GABA in Chinese rice wine during the brewing process, the level slowly increased during primary fermentation. A decrease in GABA was observed in the wine at the early stage of the post‐fermentation process. However, a marked increase on the GABA content occurred in wine at the late stage of post‐fermentation. The findings from this study are that HPLC can be successfully applied to determine GABA in Shaoxing brewed rice wines, and further provide useful information on quality control of such wines. Copyright © 2017 The Institute of Brewing & Distilling     

α 1,4 — α 1,6 Glucopolysaccharides Contained in Developing Maize Kernels

Corn grains with different filling times were fractionated in order to obtain their α 1,4 — α 1,6 glucopolysaccharide composition and structure. Sugary, waxy, flint and several hybrids were the varieties analyzed. There is an increase in the total content of polysaccharides, as the grain is completed. But, no differences in composition and structure were detected between the first sample analyzed (15th day after pollination) and the last one, which corresponds to the complete grain filling period. The methodology developed by us, allowed us to observe that the introduction of su character on the hybrids (F x S and S x F) has influence on the final polysaccharide structure. Also, in the F x W hybridα 1,4 — α 1,6 glucans, their structural characteristics were different from those of F or W pure.