Influência de uma cultura startertermofílica sobre a viabilidade de Lactobacillus acidophiluse as características de queijo minas frescal probiótico / Influence of a thermophilic starterculture over the viability of Lactobacillus acidophilusand textural, sensorial, and related properties of probiotic Minas fresh cheese

Cínthia Hoch Batista de Souza

Functional foods are foods that claim to promote human health over and above the provision of basic nutrition. Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, improving his intestinal microbial balance. Lactobacillus acidophilus strains have been shown to be able to survive at favorable concentrations for a probiotic food in a variety of cheeses, including fresh cheeses. The objective of this study was to verify the viability of Lactobacillus acidophilus La-5 added solely or in co-culture with a Streptococcus thermophilus starter culture during production of minas fresh cheese. Three different trials of minas fresh cheese were prepared (in triplicates): T1 (produced with no addition of cultures), T2 (supplemented with L. acidophilus) and T3 (supplemented with L. acidophilus + S. thermophilus). T2 and T3 were also produced with reduced fat milk in order to verify the influence of reduced fat on viability of L. acidophilus added to minas fresh cheese (T2L and T3L). The physicochemical (moisture, pH and titratable acidity) and microbiological (counts of L. acidophilus, S. thermophilus, coliforms, E. coli and Staphylococcus spp.) properties were monitored during 21 days of refrigerated storage at 5±1ºC. The instrumental texture profile (TA-XT2 Texture Analyser) was also determined. In addition, the proteolytic index after the 1st and the 21st day of storage was determined. Counts of L. acidophilus and S. thermophilus were also monitored in cheeses T2L and T3L. Sensory evaluation was performed for cheeses T1, T2 and T3, after 7 and 14 days of storage at 5±1°C, employing the acceptability test, with a 9-point hedonic scale, by 30 untrained panelists. All cheeses supplemented with L. acidophilus presented populations above 6 log cfu/g, during the whole storage period, except for T3, which presented counts of 5.74 log cfu/g, but only in the 1st day of storage. Cheeses T2L and T3L, presented initials counts above 6 log cfu/g, which increased after the 7th day of storage, remaining above 7 log cfu/g up to the last day of storage. Cheeses produced only through direct acidification of milk (T1) presented increase in counts of Staphylococcus spp. during storage, whereas the presence of lactic acid cultures inhibited the growth of these contaminants in cheeses T2 e T3. All cheeses presented an increase in the proteolytic index between the first and the last day of storage. However, the major increase was detected for T3 (95.4%) due to the presence of S. thermophilus. With respect to sensory evaluation, no significant differences were detected among cheeses after 7 days of storage (p>0.05). After 14 days, cheeses T2 and T3 presented higher acceptance and differed significantly from cheeses T1. A decrease in acceptability was observed for cheeses T1 between 7 and 14 days of storage (p<0.05), whereas probiotic cheeses T2 and T3 revealed to be stable in the same period (p>0.05). The supplementation of minas fresh cheese with Lactobacillus acidophilus La-5, either solely or in co-culture with a thermophilic starter culture (S. thermophilus), resulted in a product with great potential as a functional food, with populations above the minimum required for a probiotic product (particularly when produced with reduced fat milk), improving sensory performance of the product during storage, as well as microbiological and textural properties.

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