Yeasts in dairy products

Fleet, Graham H.

doi:10.1111/j.1365-2672.1990.tb02566.x

Cited by 337 publications

(226 citation statements)

References 76 publications

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“…D. hansenii was also the most abundant species, found in 11 out of 18 samples yet was not found in June whereas S. cerevisiae was only found in June in yoghurts from three manufacturers. D. hansenii was the most frequently isolated yeast in yoghurt samples from Australia and the United Kingdom (9,25,26).…”

Section: Yeast Speciesmentioning

confidence: 99%

“…Usually fruit flavour and colour is added into yoghurt after fermentation. Contamination by yeasts is generally related to the fruits added and/or poor hygienic practices during packaging operation (9). The association of lactose-fermenting yeasts with dairy products is well established (28).…”

Section: Introductionmentioning

confidence: 99%

“…All other micro-organisms present should be considered contaminants. Although bacteria can be spoilage organisms, yeasts and filamentous fungi are often involved in the deterioration of yoghurts (8,9). They are responsible for offflavours, loss of texture quality due to gas production, and package swelling and shrinkage (12).…”

Section: Introductionmentioning

confidence: 99%

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Isolation and identification of yeasts and filamentous fungi from yoghurts in Brazil

Moreira

Schwan

Carvalho

et al. 2001

Braz. J. Microbiol.

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Seventy-two cartons of yoghurt were sampled three times at monthly intervals from four different local manufacturers. Total counts were close to 6 x 10 7 cells g -1 of yoghurt. Yeast counts varied from 1 to 2,700 g -1 . There was no evidence of systematic contamination at source but this longitudinal study revealed that ad hoc contamination and improper storage led to the higher yeast counts. Contamination was generally higher in the hotter months but was lower overall than reported from other countries. A total of 577 yeast isolates were identified belonging to ten species. The most abundant yeasts were, in order, Debaryomyces hansenii, Saccharomyces cerevisiae, Mrakia frigida, Hansenula spp., Candida parapsilosis, Debaryomyces castellii and Candida maltosa. The psychrophilic yeast Mrakia frigida is reported for the first time in yoghurts. Low level contamination with Monilia and Penicillium species was found in a few samples. Growth tests suggested that ability to ferment sucrose, growth at 5ºC and in the presence of 300 µg g -1 sorbate preservative, were the three most significant physiological properties to account for these yeasts in yoghurts. The data also suggest that warmer weather and inadequate refrigeration are the principal causes of higher levels of contamination, increased diversity and change in microbial flora.

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Section: Yeast Speciesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Isolation and identification of yeasts and filamentous fungi from yoghurts in Brazil

Moreira

Schwan

Carvalho

et al. 2001

Braz. J. Microbiol.

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“…In addition, the second predominating groups of microorganisms were yeasts (ranging from 5.52 to 8.25 log cfu·mL −1 , averaging 7.35 log cfu·mL −1 ). Yeasts were commonly encountered in naturally fermented milks [3,5,7,16], and originate from the environment and utensils, especially the fermentation vessel. According to Fleet and Mian [6], yeast level of 10 5-6 cfu·mL −1 in dairy products was associated with spoilage.…”

Section: Microbiotamentioning

confidence: 99%

A survey on composition and microbiota of fresh and fermented yak milk at different Tibetan altitudes

Luo

et al. 2009

Dairy Sci. Technol.

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-Yak milk is a type of milk that people are less familiar with due to its remote geographical location, the particular geographical environment and climatic conditions in Tibet, which may have significant effects on composition, microbiota and fermentation outcome. To investigate the chemical composition and microbiota of fresh and fermented yak milk, and to isolate and characterize the predominant microorganisms in the fermented milk, yak milk (24 fresh and 30 fermented milk samples) was collected from four areas of different altitudes in Tibet, and their microbiological profile and chemical composition were investigated. Yak milk had a higher fat, crude protein, lactose and dry matter content than cow milk. The fermented yak milk showed a great diversity in fat and dry matter levels due to the different ways of processing in different localities, and lower pH and higher lactic acid content compared with commercial cow milk yogurt. Fermented yak milk had a better sanitary quality than fresh yak milk. Three species of lactobacilli (Lactobacillus fermentum, Lactobacillus helveticus and Lactobacillus curvatus) and five species of yeast (Saccharomyces cerevisiae, Candida kefyr, Candida lambica, Candida famata and Candida holmii) were identified phenotypically and encountered as predominant fermentation microbiota. The predominant lactic species in fermented milk was L. fermentum. yak milk / composition / microbiota / fermented milk

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“…Yeasts of this genus are widely distributed and can be found in natural habitats such as soil, water, plant exudates, insects and fruits and also as contaminants in a variety of foods and beverages and high-sugar-containing products (Heard & Fleet, 1987; Noronha-da-Costa et al, 1996). Some species of this genus have beneficial effects in food; for example, they contribute to the early stages of wine fermentation and in the processing of different types of cheeses (Lenoir, 1984;Heard & Fleet, 1988, 1990Lambrechts & Pretorius, 2000;Fernandez et al, 2000). Strains of Pichia membranifaciens are common contaminants in food-related environments and occur with high frequency in fermenting olive brines (Marquina et al, 1992(Marquina et al, , 1997.…”

Section: Introductionmentioning

confidence: 99%

PMKT2, a new killer toxin from Pichia membranifaciens, and its promising biotechnological properties for control of the spoilage yeast Brettanomyces bruxellensis

et al. 2009

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Pichia membranifaciens CYC 1086 secretes a killer toxin (PMKT2) that is inhibitory to a variety of spoilage yeasts and fungi of agronomical interest. The killer toxin in the culture supernatant was concentrated by ultrafiltration and purified to homogeneity by two successive steps, including native electrophoresis and HPLC gel filtration. Biochemical characterization of the toxin showed it to be a protein with an apparent molecular mass of 30 kDa and an isoelectric point of 3.7. At pH 4.5, optimal killer activity was observed at temperatures up to 20 6C. Above approximately this pH, activity decreased sharply and was barely noticeable at pH 6. The toxin concentrations present in the supernatant during optimal production conditions exerted a fungicidal effect on a variety of fungal and yeast strains. The results obtained suggest that PMKT2 has different physico-chemical properties from PMKT as well as different potential uses in the biocontrol of spoilage yeasts. PMKT2 was able to inhibit Brettanomyces bruxellensis while Saccharomyces cerevisiae was fully resistant, indicating that PMKT2 could be used in wine fermentations to avoid the development of the spoilage yeast without deleterious effects on the fermentative strain. In small-scale fermentations, PMKT2, as well as P. membranifaciens CYC 1086, was able to inhibit B. bruxellensis, verifying the biocontrol activity of PMKT2 in simulated winemaking conditions. INTRODUCTIONWorldwide, microbial growth destroys large amounts of various products, causing yield losses in the agronomical and biotechnological industries. Traditionally, biocides have been used to deal with these problems but different disadvantages such as establishment of resistant strains and suppression of natural competitors have made alternatives such as biological control necessary (Beever et al., 1989;Raposo et al., 2000). Biological control strategies include natural plant-and animal-derived compounds, as well as antagonistic micro-organisms (Ciani & Fatichenti, 2001).During recent decades, microbiological control of spoilage micro-organisms has evolved as a possibility. Many yeast strains and other micro-organisms inhibiting plant pathogens have been reported, especially within the fruit-and vegetable-producing sector, and several new products have reached the commercial market (Janisiewicz & Korsten, 2002). The suggested modes of action of biocontrol yeasts are not likely to constitute any hazard for the consumer (Janisiewicz et al., 2001;Masih & Paul, 2002;Comitini et al., 2004;Santos & Marquina, 2004a).The food and beverage industries were among the first to explore the application of killer-toxin-producing yeasts to kill spoilage micro-organisms (Lowes et al., 2000). Yeast strains often achieve competitive advantage by producing killer toxins, which kill off competing sensitive cells belonging to either the same or a different species (Young, 1987;Ciani & Fatichenti, 2001). The most thoroughly studied examples are the Saccharomyces cerevisiae toxins K1, K2 and K28; producers of these toxi...

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Yeasts in dairy products

Cited by 337 publications

References 76 publications

Isolation and identification of yeasts and filamentous fungi from yoghurts in Brazil

Isolation and identification of yeasts and filamentous fungi from yoghurts in Brazil

A survey on composition and microbiota of fresh and fermented yak milk at different Tibetan altitudes

PMKT2, a new killer toxin from Pichia membranifaciens, and its promising biotechnological properties for control of the spoilage yeast Brettanomyces bruxellensis

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