HYNES Erica Rut
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Aminotransferase profile of Lactobacillus paracasei I90 led flavor formation in model cheeses
GUILLERMO PERALTA; VERÓNICA WOLF; CARINA BERGAMINI; MARÍA CRISTINA PEROTTI; ERICA HYNES
Simposio; 6th IDF Cheese Ripening & Technology Symposium; 2012
International Dairy Federation
The addition of adjunct cultures of selected non starter lactic acid bacteria to cheese with minimal adventitious NSLAB populations is one of the strategies that cheese industry can successfully apply to improve cheese ripening control and quality consistency. Some of these cultures which possess key enzymatic activities may also improve or diversify flavour notes by amino acids catabolism. We tested a strain of Lactobacillus paracasei which showed main aminotransferase (AT) activity towards aspartic acid, followed by AT specificity towards branched chain amino acids and Trp, and little but detectable AT specificity towards Met, Phe and Tyr, in two different cheese models representative of soft cheeses and hard cooked cheeses. In the first trial, mini soft cheeses were made with a starter culture of Streptococcus thermophilus and with or without the adjunct culture Lactobacillus paracasei I90. In the second model, a sterile extract of hard cooked cheese was obtained from Reggianito cheese made with a Lactobacillus helveticus single-strain starter, and inoculated or not with Lactobacillus paracasei I90. Miniature soft cheeses were ripened by 60 days at 10 ºC and sterile extract was incubated at 34 ºC 14 days. Microbiological counts were recorded and volatile compounds were analyzed by SPME GC both by FID and MS detection. Both models containing Lactobacillus paracasei I90 showed increased content of flavour compounds derived from Asp and Leu, while other flavour molecules varied from one cheese model to another. Results suggest that when the adjunct was added, AT profile led the formation of flavour compounds similarly in both cheese models, in spite of the differences in primary starter, composition and basic initial proteolysis.