The Screening On Semi-hard Cheese Adjunct Culture And Study On The Influence To Cheese Flavour

Adjunct cultures can improve development of cheese sensory quality and accelerate cheese ripening. 12 strains of lactobacillus were isolated from traditional fermented foods for their good growth performance in cheese ripening conditions.Two strains which labeled as"SP-3"and"SP-4"were screened for its global peptidase activities and high lysis capacities. Strain SP-3 was finally determined to be selected for further study for its better contribution to cheese model flavour devolepement.It was classified as lactobacillus plantarum by API identification system.Cheese model which was made aseptically using fresh cheese curd was used to rapidly evaluated effect of strain SP-3 on cheese ripening. WSN, 12%TCASN and free amino acids contents etc. as the proteolysis index were regarded as ripening index. The value of WSN and the electrophoretic profile for casein degradation in cheese model indicated SP-3 had no influence on casein primary proteolysis. Reverse phase HPLC of water-soluble extracts of the slurries indicated differences in peptide profiles between slurries with nonstarter compared with the control. And the significant difference of 12%TCASN also approve this result. Total free amino acids and individual amino acids concentrations also suggest varied proteolytic capabilities between nonstarter strains in control and other cheeses. Slurries containing lactobacillus plantarum SP-3 released more amino acids (leucine, isoleucine, valine) than did control slurry .Volatile flavour compound produced in ripend cheese slurries model was studied bu GC-MS. And the difference of flavour compounds between slurries containing lactobacillus plantarum SP-3 and the control slurries was detected. In contrast to the control slurries, slurries containing lactobacillus plantarum SP-3 had high concentration of 2-butanone, 2-methyl -1-propanol, 3-methyl-1-butanol, 3-hydroxy-2-butanone which contribute nutty and creamy flavour.Semi-hard cheeses were manufactured in open vats to study the influence of adjunct culture of lactobacillus plantarum SP-3 on proteolysis and the development of sensory charateristics during ripening. Lactobacilli in the experimental cheeses reached maxima (3.4﹡108 cfu/g) at ~3 mo and then decreased to 106 to 107 cfu/g at 6 mo. Numbers of lactobacilli in the control cheeses were lower than in the experimental cheeses until 6 mo of ripening.Assessment of primary proteolysis during ripening showed essentially no differences between the control and experimental cheeses. However, the experimental cheeses had consistently higher levels of total free amino acids than did their corresponding controls throughout ripening. Sensory analysis of the cheeses (at 3 and 6 mo) showed significant differences between the control and experimental cheeses with respect to some importantsensory attributes. Principal component analysis of the sensory data clearly differentiated between flavor of control and experimental cheeses.