Proteolytic yeasts isolated from raw, ripe tomatoes and metabiotic association of Geotrichum candidum with Salmonella

Wendy N. Wade, Rita Vasdinnyei, T. Deák, Larry R. Beuchat

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Metabiotic associations between food-borne fungi and bacteria capable of causing human diseases are a public health concern. A survey of decayed and damaged, uncooked, ripe tomatoes was done to determine the presence and prevalence of yeasts capable of increasing the pH pulp tissue, thus creating a more favorable environment for survival and growth of enteric pathogens. Sixty-two of the 371 (16.7%) fungi isolated from 215 decayed or damaged tomatoes; 12 of the 62 (19.4%) yeasts showed proteolytic activity on gelatin agar (GA) and/or standard methods caseinate (SMC) agar. The pH of tomato pericarp (pulp) tissue from which 9 of the 12 yeasts were isolated ranged from 4.3 to 7.5 (mean=5.3) compared to 4.2-5.1 (mean=4.8) for sound pulp tissue in the same tomatoes. The 12 proteolytic yeasts consisted of four strains of Cryptococcus albidus, two strains each of Debaryomyces hansenii and Trichosporon pullulans, and one strain each of Cryptococcus humicolus, Cryptococcus laurentii, Geotrichum candidum, and Sporidiobolus pararoseus. Survival and growth characteristics of a five-serotype mixture of Salmonella co-inoculated with G. candidum into sound (not chill injured) and chill-injured tomatoes were studied. Storage of sound tomatoes at 15°C for 10 days resulted in an increase in population of 7.6 log10 cfu of Salmonella/g of a 2-g sample of co-infected pulp tissue. Increases were less in tissue inoculated with Salmonella only, Salmonella on day 0 followed by G. candidum on day 3, or G. candidum on day 0 followed by Salmonella on day 3. Trends were similar in sound inoculated tomatoes stored at 25°C. Growth of Salmonella was enhanced in chill-injured tomatoes compared to sound tomatoes; a population of 10 log10 cfu/g of chill-injured pulp tissue was reached within 10 days at 25°C. Results clearly show that growth of a proteolytic, alkalinizing yeast such as G. candidum in raw tomatoes enhances conditions for growth of Salmonella. The removal of tomatoes infected with proteolytic yeasts and other fungi from lots intended for minimally processed tomato products is an essential step in reducing the risk of human diseases caused by pathogenic bacteria favored by increased pH of decayed pulp tissue.

Original languageEnglish
Pages (from-to)101-111
Number of pages11
JournalInternational Journal of Food Microbiology
Volume86
Issue number1-2
DOIs
Publication statusPublished - Sep 1 2003

Fingerprint

Geotrichum
Geotrichum candidum
Lycopersicon esculentum
Salmonella
Yeasts
tomatoes
yeasts
pulp
Chills
Cryptococcus
Growth
Fungi
human diseases
fungi
Trichosporon pullulans
Agar
Sporidiobolus
agar
Cryptococcus albidus
Cryptococcus laurentii

Keywords

  • Geotrichum candidum
  • Proteolytic yeasts
  • Salmonella

ASJC Scopus subject areas

  • Food Science
  • Microbiology

Cite this

Proteolytic yeasts isolated from raw, ripe tomatoes and metabiotic association of Geotrichum candidum with Salmonella. / Wade, Wendy N.; Vasdinnyei, Rita; Deák, T.; Beuchat, Larry R.

In: International Journal of Food Microbiology, Vol. 86, No. 1-2, 01.09.2003, p. 101-111.

Research output: Contribution to journalArticle

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