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Reggianito Argentino cheese is traditionally manufactured with whey starter cultures that provide typical and intense flavor but can cause poor quality standardization. In this study, the influence of natural and selected starters on Reggianito Argentino cheese proteolysis was investigated. Cheeses were manufactured with three strains of Lactobacillus helveticus (SF133, SF138 and SF209) cultured individually in sterile whey and used as single or mixed starters. Control cheeses were made with natural whey starter culture. Cheeses were analyzed to determine gross composition, as well as total thermophilic lactic flora. Proteolysis was assessed by N fractions, electrophoresis and liquid chromatography. Gross composition of the cheeses did not significantly differ, while viable starter cell counts were lower for cheeses made with strain SF209 alone or combined with other strains. Soluble N at pH 4.6 was the same for cheeses made with natural or selected starters, but soluble N in 12% trichloroacetic acid and 2.5% phosphotungstic acid was significantly higher in cheeses made with starters containing strain SF209. Nitrogen fractions results indicated that natural whey starter cultures could be replaced by several starters composed of the selected strains without significant changes to proteolysis patterns. Starter cultures prepared only with SF209 or with the three selected L. helveticus strains produced cheese products with significantly more proteolysis than control cheeses. Chromatographic profiles analyzed by principal components showed that three main peaks on chromatograms, presumptively identified as Tyr, Phe, and Trp, explained most of variability. Principal component scores indicated that cheese samples were grouped by ripening time, which was confirmed by linear discriminant analysis. On the contrary, samples did not cluster by Lactobacillus strain or type of starter.

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International audienceThe composition of the dairy matrix used in yogurt manufacture could influence the metabolic activity of yogurt starter and the compounds produced during fermentation. In this way, the lactose hydrolysis with a β-galactosidase enzyme and the supplementation with dairy powders to obtain different types of delactosed yogurts for lactose-intolerant people modifies the milk base composition. In this work, we studied the influence of the addition of different doses of β-galactosidase and levels of dairy powders on organic acids profile during the manufacture and storage of two varieties of yogurt (natural and sweetened). Lactose, glucose, galactose, titratable acidity, fermentation time, and microbiological counts were also evaluated. The mean proportions of lactose/glucose/galactose in relation to the total sugars were 18:36:46 in hydrolyzed yogurts, while they were 81:4:15 in unhydrolyzed ones. In supplemented yogurts, the content of lactose, citric, orotic, and hippuric acids were significantly increased. The starter population was similar in all yogurts, but some changes in their activity were evidenced due to both factors studied. The fermentation time was slightly increased, and the lactic acid content and the titratable acidity were significantly increased due to fortification while they were decreased by enzyme addition. These results are probably due to the increase in the buffer properties of the milk base by the dairy powder addition and due to an inhibition of the starter activity caused by changes in the carbohydrate profile. The results demonstrated that the changes in the matrix composition of the yogurt affected the organic acids profile, above all the lactic acid content