Avaliação da viabilidade de estirpes probióticas em preparados de fruta para aplicação em produtos láteos

Abstract

The fast perception regarding the beneficial effects that probiotic microorganisms have to promote consumer’s health has led to an increased demand of potential vehicles for their incorporation. Diary matrices are normally associated with consumption of probiotics and the addition of fruit matrices is a viable alternative to the maintenance of its viability. Fruit is rich in nutrients, dietetic fibers and sugars, despite the presence of antimicrobial compounds which constitute their main disadvantage. In this context, it is extremely important to formulate a universal fruit matrix capable of enabling the stability of probiotic cultures during processing and storage. The aims of this study were the stability evaluation of two commercial stains - Lactobacillus paracasei subsp. paracasei L. casei 431® e Bifidobacterium animalis ssp. lactis BB-12® (lyophilized and frozen state) – when incorporated in distinct fruit preparations, in terms of viability evolution, pH and ºBrix, and the evaluation of the fruit matrices effect in the strains stability when subjected to simulated conditions of passage through the gastrointestinal tract (GIT). The strains were cultivated, centrifuged and inoculated in each fruit preparation, previously pasteurized, at 1% (w/w). After homogenization, the matrix was stored under refrigeration at 5 ± 2˚C, during 28 days. During this period, the numbers of viable cells were monitored at 0, 3, 5, 7, 14, 21 and 28 days by plating dilutions on appropriate MRS agar, as well as the pH and ºBrix of fruit preparations. The fruits which better contributed to the stability of both strains were strawberry and apricot and also B. animalis BB-12® was the strain that showed greater viability in its frozen form. Gastrointestinal assays were performed by simulating the stomach (pH between 1.5 and 2.0) and intestinal (pH between 6.0 and 6.2), conditions adding hydrochloric acid 1M and sodium hydroxide 0.25M with bile salts at 0.3% (w/v), respectively, incubating at 37˚C within 60 and 120 minutes intervals. Between each interval samples were taken for enumeration purposes. It was found that the strains under study are capable of exerting their beneficial functions in the host, since they can withstand exposure to GIT conditions. Finally, it was analyzed the behavior of strain B. animalis BB-12® in yoghurts inoculated with 3 fruit preparations. For a period of 2 month, the fruit matrix inoculated was monthly incorporated in the yogurt. After the yogurt homogenization, the matrix was stored under refrigeration at 5 ± 2˚C over a period of 28 days. Then, the number of viable cells was monitored at 0, 7, 14 and 28 days, with pH and ºBrix registration. The apricot matrix proved to be the most suitable for maintaining the viability of the probiotic strain upon its incorporation into the yogurt.

Date of Award	2013
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Domingos P. F. Almeida (Supervisor) & Ana Maria Gomes (Co-Supervisor)