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Applied and Environmental Microbiology Jan 2016Microbial starter cultures have extensively been used to enhance the consistency and efficiency of industrial fermentations. Despite the advantages of such controlled...
Microbial starter cultures have extensively been used to enhance the consistency and efficiency of industrial fermentations. Despite the advantages of such controlled fermentations, the fermentation involved in the production of chocolate is still a spontaneous process that relies on the natural microbiota at cocoa farms. However, recent studies indicate that certain thermotolerant Saccharomyces cerevisiae cultures can be used as starter cultures for cocoa pulp fermentation. In this study, we investigate the potential of specifically developed starter cultures to modulate chocolate aroma. Specifically, we developed several new S. cerevisiae hybrids that combine thermotolerance and efficient cocoa pulp fermentation with a high production of volatile flavor-active esters. In addition, we investigated the potential of two strains of two non-Saccharomyces species that produce very large amounts of fruity esters (Pichia kluyveri and Cyberlindnera fabianii) to modulate chocolate aroma. Gas chromatography-mass spectrometry (GC-MS) analysis of the cocoa liquor revealed an increased concentration of various flavor-active esters and a decrease in spoilage-related off-flavors in batches inoculated with S. cerevisiae starter cultures and, to a lesser extent, in batches inoculated with P. kluyveri and Cyb. fabianii. Additionally, GC-MS analysis of chocolate samples revealed that while most short-chain esters evaporated during conching, longer and more-fat-soluble ethyl and acetate esters, such as ethyl octanoate, phenylethyl acetate, ethyl phenylacetate, ethyl decanoate, and ethyl dodecanoate, remained almost unaffected. Sensory analysis by an expert panel confirmed significant differences in the aromas of chocolates produced with different starter cultures. Together, these results show that the selection of different yeast cultures opens novel avenues for modulating chocolate flavor.
Topics: Acetates; Cacao; Esters; Fermentation; Flavoring Agents; Hot Temperature; Humans; Saccharomyces cerevisiae; Taste
PubMed: 26590272
DOI: 10.1128/AEM.02556-15 -
Journal of Applied Microbiology Sep 2015To determine the starter culture and multifunctional potentials of yeast strains from some cereal-based Nigerian traditional fermented food products.
AIMS
To determine the starter culture and multifunctional potentials of yeast strains from some cereal-based Nigerian traditional fermented food products.
METHODS AND RESULTS
Yeast isolates were screened for enzyme production and identified by sequencing the D1/D2 region of 26S rDNA. Pichia kluyveri LKC17, Issatchenkia orientalis OSL11, Pichia kudriavzevii OG32, Pichia kudriavzevii ROM11 and Candida tropicalis BOM21 exhibited the highest protease, lipase and phytase activity. They were selected and further evaluated for gastrointestinal survival and adherence ability. Although strain-specific, they retained viability at 37°C and showed survival at pH 2·0., I. orientalis OSL11 showed the highest survival at 2% bile salts concentration and P. kudriavzevii ROM11 showed the least survival. The yeast strains showed strong autoaggregation ability (81·24-91·85%) and hydrophobicity to n-hexadecane (33·61-42·30%). The highest co-aggregation ability was detected for P. kudriavzevii OG32 and Escherichia coli (71·57%). All the yeast strains removed cholesterol in the range of 49·03-74·05% over 48 h and scavenged for free radicals in methanol reaction system.
CONCLUSIONS
In this study, we isolated new yeast strains with multifunctional potentials that can be used as functional starter cultures to produce cereal-based probiotic products.
SIGNIFICANCE AND IMPACT OF THE STUDY
The development of probiotic yeast strains as starter culture to improve the quality attributes and confer functional value on cereal-based traditional fermented foods is beneficial.
Topics: Cholesterol; Edible Grain; Fermentation; Food Microbiology; Molecular Sequence Data; Nigeria; Probiotics; Yeasts
PubMed: 26095794
DOI: 10.1111/jam.12875 -
BioMed Research International 2013We studied the dynamic behavior of wild yeasts during spontaneous wine fermentation at a winery in the Valais region of Switzerland. Wild yeasts in the winery...
We studied the dynamic behavior of wild yeasts during spontaneous wine fermentation at a winery in the Valais region of Switzerland. Wild yeasts in the winery environment were characterized using a PCR-RFLP method. Up to 11 different yeast species were isolated from the vineyard air, whereas only seven were recovered from the grapes surface. We initially investigated a cultureindependent method in pilot-scale steel fermentation tanks and found a greater diversity of yeasts in the musts from two red grape varieties compared to three white grape varieties. We found that the yeasts Metschnikowia pulcherrima, Rhodotorula mucilaginosa, Pichia kluyveri, P. membranifaciens and Saccharomyces cerevisiae remained active at the end of the fermentation. We also studied the dynamic behavior of yeasts in Qvevris for the first time using a novel, highlysensitive quantitative real-time PCR method. We found that non-Saccharomyces yeasts were present during the entire fermentation process, with R. mucilaginosa and P. anomala the most prominent species. We studied the relationship between the predominance of different species and the output of the fermentation process. We identified so-called spoilage yeasts in all the fermentations, but high levels of acetic acid accumulated only in those fermentations with an extended lag phase.
Topics: Bioreactors; Fermentation; Polymerase Chain Reaction; Polymorphism, Restriction Fragment Length; Real-Time Polymerase Chain Reaction; Stainless Steel; Vitis; Wine; Yeasts
PubMed: 23738327
DOI: 10.1155/2013/540465 -
Journal of Food Protection Oct 2006The potential use of the commercial biocontrol products Serenade (Bacillus subtilis QST-713) and Trichodex (Trichoderma harzianum Rifai strain T39) to inhibit the...
The potential use of the commercial biocontrol products Serenade (Bacillus subtilis QST-713) and Trichodex (Trichoderma harzianum Rifai strain T39) to inhibit the postharvest pathogenic molds Penicillium crustosum and Mucor circinelloides was investigated. Both products exhibited antagonistic activity in vitro against the pathogens, reducing their growth at different levels. In addition, epiphytic yeasts isolated from peaches were identified as Candida maltosa, Pichia fermentans, and Pichia kluyveri by PCR-restriction fragment length polymorphism of internal transcribed spacer regions and screened for antagonistic activity against the same molds. The efficacy of biocontrol in vitro was dependent on the concentration of the yeast cells. Optimal yeast concentrations were above 10(7) CFU ml(-1). However, C. maltosa and P. fermentans were more effective than P. kluyveri in inhibiting molds. The exclusion of antifungal metabolite production and direct competition for nutrients or space with the pathogens was proposed as the mechanism of biocontrol. Application of biocontrol agents directly on artificially wounded peach fruits significantly reduced the incidence of mold rot during storage at 20 degrees C.
Topics: Antibiosis; Bacillus subtilis; Colony Count, Microbial; DNA, Fungal; Food Preservation; Fungi; Humans; Mucor; Penicillium; Pest Control, Biological; Prunus; Species Specificity; Time Factors; Trichoderma; Yeasts
PubMed: 17066929
DOI: 10.4315/0362-028x-69.10.2465 -
Applied and Environmental Microbiology Dec 1995The succession of yeasts colonizing the fallen ripe amapa fruit, from Parahancornia amapa, was examined. The occupation of the substrate depended on both the competitive...
The succession of yeasts colonizing the fallen ripe amapa fruit, from Parahancornia amapa, was examined. The occupation of the substrate depended on both the competitive interactions of yeast species, such as the production of killer toxins, and the selective dispersion by the drosophilid guild of the amapa fruit. The yeast community associated with this Amazon fruit differed from those isolated from other fruits in the same forest. The physiological profile of these yeasts was mostly restricted to the assimilation of a few simple carbon sources, mainly L-sorbose, D-glycerol, DL-lactate, cellobiose, and salicin. Common fruit-associated yeasts of the genera Kloeckera and Hanseniaspora, Candida guilliermondii, and Candida krusei colonized fruits during the first three days after the fruit fell. These yeasts were dispersed and served as food for the invader Drosophila malerkotliana. The resident flies of the Drosophila willistoni group fed selectively on patches of yeasts colonizing fruits 3 to 10 days after the fruit fell. The killer toxin-producing yeasts Pichia kluyveri var. kluyveri and Candida fructus were probably involved in the exclusion of some species during the intermediate stages of fruit deterioration. An increase in pH, inhibiting toxin activity and the depletion of simple sugars, may have promoted an increase in yeast diversity in the later stages of decomposition. The yeast succession provided a patchy environment for the drosophilids sharing this ephemeral substrate.
Topics: Animals; Drosophila; Food Microbiology; Fruit; Fungi
PubMed: 8534092
DOI: 10.1128/aem.61.12.4251-4257.1995 -
Applied and Environmental Microbiology Mar 1992Representative strains (n = 61) of the yeast Pichia kluyveri from across the United States were studied for their ability to kill 71 other strains (representing 25...
Representative strains (n = 61) of the yeast Pichia kluyveri from across the United States were studied for their ability to kill 71 other strains (representing 25 species) of yeast. This survey showed killing activity in 69% of the P. kluyveri strains tested. More extensive analysis of killer activity of 197 P. kluyveri strains against strains of five tester species showed comparable activity (67% of strains tested). This activity was shown to be equally variable within localities, within regions, and across the continent. The genetic basis of the variability was ascertained by tetrad analysis and is most likely due to alleles segregating at three epistatic loci. Evidence for the idea that killer toxins have a role in excluding other yeasts from particular habitats is discussed.
Topics: Crosses, Genetic; Genetics, Population; Genotype; Models, Genetic; Mycotoxins; Phenotype; Pichia; United States
PubMed: 1575502
DOI: 10.1128/aem.58.3.990-997.1992 -
Antimicrobial Agents and Chemotherapy Oct 1980Loss of viability of toxin-treated cells of Saccharomyces cerevisiae SCF 1717 could be prevented in the period before they altered physiologically if cells were...
Loss of viability of toxin-treated cells of Saccharomyces cerevisiae SCF 1717 could be prevented in the period before they altered physiologically if cells were incubated in media with a suitable concentration of potassium (0.08 to 0.13 M) and hydrogen ions (pH 6.2 to 6.7). Incorporation of higher amounts of potassium chloride in the media had a pronounced negative effect on cell survival, particularly when the pH of the medium was lowered. Replacement of KCl by NaCl in the plate media was even more deleterious to toxin-treated cells and, in contrast with potassium, low concentrations of sodium ions could not sustain recovery of cells. Complete recovery of a toxin-treated cell suspension required an incubation of 3 h in a suitable medium. The recovery process was blocked by cycloheximide.
Topics: Antifungal Agents; Ascomycota; Culture Media; Dose-Response Relationship, Drug; Hydrogen-Ion Concentration; Mycotoxins; Pichia; Potassium; Saccharomyces cerevisiae; Sodium
PubMed: 7004340
DOI: 10.1128/AAC.18.4.519