Impact of two Williopsis yeast strains on the volatile composition of mango wine

Lachancea thermotolerans, a Yeast Symbiont of Yellowjackets, Enhances Attraction of Three Yellowjacket Species (Hymenoptera: Vespidae) to Fruit Powder

Previously, we showed that the symbiotic yeast Lachancea thermotolerans (Filippov) (Saccharomycetales: Saccharomycetaceae) is attractive to its Vespula (Hymenoptera: Vespidae) yellowjacket hosts when grown on media supplemented with grape juice. We hypothesized that "Concerto", a commercial strain of this yeast, could be combined with fruit powder to form a shelf-stable bait for trapping yellowjackets. Using molecular techniques, we first confirmed that Concerto yeast is indeed the species L. thermotolerans. We then tested whether: 1) Concerto yeast produces volatiles similar to those produced by L. thermotolerans isolated from yellowjackets, 2) Concerto yeast enhances attraction of yellowjackets to fruit powder, 3) a Concerto yeast/fruit powder bait interacts synergistically with a yellowjacket semiochemical lure, and 4) a synthetic analog blend of Concerto-produced volatiles attracts yellowjackets. Using gas chromatography-mass spectrometry, we demonstrated that the chemical composition of Concerto-produced volatiles closely resembles that produced by a yellowjacket-isolated strain of L. thermotolerans. In field experiments, addition of Concerto to fruit powder doubled its attractiveness to yellowjackets. Addition of the Concerto/fruit powder bait to a heptyl butyrate-based wasp lure revealed a weak additive effect. A three-component synthetic analog blend of volatiles identified from the Concerto/fruit powder bait attracted Vespula pensylvanica (Saussure), but no other yellowjacket species. Our results suggest that commercial L. thermotolerans in combination with fruit powder could be used as a yellowjacket bait, and that addition of yeast-produced volatiles to a commercial wasp lure may improve its attractiveness to V. pensylvanica. Further research should determine why the synthetic volatile blend failed to attract Vespula species other than V. pensylvanica.

Assessment of volatile and non-volatile compounds in durian wines fermented with four commercial non-Saccharomyces yeasts

BACKGROUND

Chemical compositions of durian wines fermented with Metschnikowia pulcherrima Flavia, Torulaspora delbrueckii Biodiva, Pichia kluyveri FrootZen and Kluyveromyces thermotolerans Concerto were investigated.

RESULTS

Sucrose was not utilized by M. pulcherrima and P. kluyveri, resulting in little formation of ethanol (0.3-0.5%, v/v), while about 7% ethanol was produced by the other two yeasts. Volatiles such as esters and sulfur-containing compounds were synthesized or catabolized and distinctive differences existed among yeasts. Larger amounts of higher alcohols and ethyl esters were detected in wines fermented by T. delbrueckii and K. thermotolerans, whereas M. pulcherrima and P. kluyveri produced more acetate esters such as ethyl acetate (1034.43 and 131.05 mg L(-1) respectively) and isoamyl acetate (0.56 and 27.68 mg L(-1) respectively). Most endogenous sulfur volatiles such as disulfides declined to trace levels, but new ones such as thioesters were formed. Sulfur volatiles in wines fermented by T. delbrueckii accounted for 0.20% relative peak area (RPA), followed by K. thermotolerans (0.23% RPA), P. kluyveri (1.43% RPA) and M. pulcherrima (4.16% RPA).

CONCLUSION

The findings showed that a more complex flavor could result from fermentation with different non-Saccharomyces yeasts and the typical durian odor would still remain.

Comparison of aroma-active volatiles and their sensory characteristics of mangosteen wines prepared by Saccharomyces cerevisiae with GC-olfactometry and principal component analysis

Mangosteen fruit is fermented with five different strains (i.e. GRE (Y1), Lalvin RC212 (Y2), Lalvin D254 (Y3), CGMCC2.23 (Y4) and CGMCC2.4 (Y5)) of the yeast Saccharomyces cerevisiae to make mangosteen wines. A total of 36 volatile compounds of the mangosteen wines were identified by gas chromatography-mass spectrometry and gas chromatography-pulsed flame photometric detection. A total of 35 odour-active compounds were identified by gas chromatography-olfactometry analysis and by the detection frequency (DF) method. The compounds with high DF values included ethyl octanoate, ethyl hexanoate and 3-methyl-2-butene-1-thiol. Principal component analysis was used to characterise the differences of the flavour profiles of those mangosteen wines. The result demonstrated that the samples could be divided into three groups that were associated closely with aroma-active compounds.

Yeast ratio is a critical factor for sequential fermentation of papaya wine by Williopsis saturnus and Saccharomyces cerevisiae

The growth kinetics and fermentation performance of Williopsis saturnus and Saccharomyces cerevisiae at ratios of 10:1, 1:1 and 1:10 (W.:S.) were studied in papaya juice with initial 7-day fermentation by W. saturnus, followed by S. cerevisiae. The growth kinetics of W. saturnus were similar at all ratios, but its maximum cell count decreased as the proportion of S. cerevisiae was increased. Conversely, there was an early death of S. cerevisiae at the ratio of 10:1. Williopsis saturnus was the dominant yeast at 10:1 ratio that produced papaya wine with elevated concentrations of acetate esters. On the other hand, 1:1 and 1:10 ratios allowed the coexistence of both yeasts which enabled the flavour-enhancing potential of W. saturnus as well as the ethyl ester and alcohol-producing abilities of S. cerevisiae. In particular, 1:1 and 1:10 ratios resulted in production of more ethyl esters, alcohols and 2-phenylethyl acetate. However, the persistence of both yeasts at 1:1 and 1:10 ratios led to formation of high levels of acetic acid. The findings suggest that yeast ratio is a critical factor for sequential fermentation of papaya wine by W. saturnus and S. cerevisiae as a strategy to modulate papaya wine flavour.

Fermentation of three varieties of mango juices with a mixture of Saccharomyces cerevisiae and Williopsis saturnus var. mrakii

This study was carried out to ascertain the behavior and fermentation performance of mixed yeasts in mango juices of three varieties. Saccharomyces cerevisiae MERIT.ferm and Williopsis saturnus var. mrakii NCYC500 at a ratio of 1:1000 were simultaneously inoculated into juices of three mango (Mangifera indica L.) varieties (R2E2, Harum Manis and Nam Doc Mai). Both yeasts grew well in all juices and there was no early growth arrest of either yeast, but there was late death of W. saturnus var. mrakii NCYC500 in the Nam Doc Mai juice. Fructose, glucose and sucrose were consumed to trace levels in all juices. Changes in citric, tartaric, malic, acetic and succinic acids varied with mango varieties. While the changes of major volatiles were similar in all varieties, there were significant varietal differences in the volatile composition of the resultant mango wines. The volatiles, especially most of the terpenes, of the juices decreased drastically and new volatiles such as β-citronellol were formed. R2E2 wine had more fruity, sweet and creamy notes, and retained more of its original character due to a higher retention of ketones/lactones. Harum Manis wine had the lowest aroma intensity with more green and terpenic notes associated with higher levels of residual terpenes than the other two varieties. Nam Doc Mai wine possessed the highest aroma intensity with winey, yeasty, fruity and floral notes attributed to higher amounts of alcohols, acetate esters and ethyl esters. These findings may help develop different styles of mango wine.