Effect of freeze-dried kefir culture on proteolysis in feta-type and whey-cheeses

The effect of freeze-dried kefir culture on the proteolysis of feta-type and whey-cheese was investigated. All nitrogen fractions increased during ripening. Although no significant differences were observed in total nitrogen (TN), the levels of water-soluble nitrogen (WSN), pH 4.4-soluble nitrogen (SN), 12% trichloroacetic acid-soluble nitrogen (TCA-SN) and phosphotungstic acid-soluble nitrogen (PTA-SN) were significantly higher in cheeses produced by freeze-dried kefir culture during the later stages of ripening. Content of total free amino acids (FAA) was significantly affected by freeze-dried kefir starter culture and it was continuously increased in kefir-cheese while, in rennet-cheese it was increased up to 30 days of ripening and then slightly decreased. On the other hand, FAA content continuously decreased in kefir-whey-cheese whereas it increased in whey-cheese. The cheese samples produced by freeze-dried kefir as starter Culture were characterised as high-quality products during the preliminary sensory evaluation and they were accepted by the panel, Overall, the use of freeze-dried kefir suggested acceleration of cheese ripening and resulted in improved sensory characteristics. (C) 2009 Elsevier Ltd. All rights reserved.