Yeast isolation from deteriorated juice. Sensibility to phenolic compounds

CLAUDIA V.VALLEJO; MARÍA J. RODRIGUEZ VAQUERO; GRACIELA ROLLÁN; ANA M. STRASSER DE SAAD

Rosario

Congreso; IX Congreso de Microbiología General; 2013

Sociedad Argentina de Microbiología

 Yeasts are part of the microbial population of fruit; some studies suggest that these yeasts could be involved in the decomposition process of juice. Phenolic compounds contribute to the sensory quality of vegetables and fruits, as well as their transformation products; numerous studies have demonstrated the beneficial properties of these compounds for consumer health, including antioxidant and antimicrobial. The aim of this study was the isolation of yeast present in deteriorated juice and the effect of pure phenolic compounds and total polyphenols of strawberry and blueberry on their growth parameters. Fruit juice was prepared and stored at room temperature until the first signs of deterioration, at this time, samples of deteriorated juices were plating in YMPG medium + chloramphenicol  (1,000 mg/l) and incubated at 28°C for 24-48 hours. The characteristics of colonies were observed, picked colonies were inoculated in YPMG broth and incubated at 28°C for 48 h. Morphology of yeast was observed in an optical microscope. Strawberries var. camarosa and blueberries var. bluecrisp cultivated in the northwestern Argentina were selected to prepare fruit juices, juice fraction was clarified with activated carbon. Modified the parameters of spoilage yeast growth by phenolic compounds: It will evaluate the effect of pure CF commercial origin (caffeic acid and quercetin) and total CF juices JF (Camarosa) and JA (Blue Crisp) using corresponding clarified juices as controls on the growth parameters of the yeast isolates. The CF will be added to the culture medium YMPG and determine the parameters of growth over the medium control without CF. Results and Discussion: From microscopic and macroscopic examination demonstrated two yeasts groups: group A (1, 4, 5, 7, 8, 11, 14 and 16) with colonies clear, transparent, opaque with regular edges and group B (2, 3, 6, 9, 12, 13, 15, 17 and 18) with bright colonies creamy and rounded. A total of 18 isolates approximately 33% of spoilage yeasts in strawberry juice (4, 7, 10, 12, 13 and 18) were affected by juices from berries (strawberry and blueberry Camarosa Blue Crisp) and commercial phenolic compounds (quercetin and caffeic acid). Yeasts 7 and 10 were affected by phenolic juice (strawberry and blueberry) and quercetin and caffeic acid. More than 83% of the strains were inhibited by caffeic acid while quercetin only affected to 50% of the isolates. Camarosa strawberry juice was more effective to modify the growth of yeasts Arandoño juice Blue Crisp (83 and 70% respectively). Conclusion: These results constitute an important contribution to biotechnology, considering the future application of the phenolic compounds in strawberries and cranberry juice as natural inhibitors of food spoilage microorganisms.