Physical And Biochemical Changes During Ripening Of Double-protein Cheese Made From Cows And Soya Milk Blends Using Selection Starters

Cheeses are rich nutritional dairy products, which were development slowly in China for taste and other reasons. Flavor of cheese is an important indicator to the quality of cheese. Raw materials, starters, processing and maturation conditions are all influence the flavor of cheese. It was researched that adding soy protein and experimental starters influence physical and chemical, rheological, microstructural and flavor changes. It was provided the theoretical basis to the production, quality assessment and development of double-protein cheeses.This study includes the following eight aspects:First, Selected and blended of starters used in double protein cheeses:Acidity, pH, extracellular polysaccharides, viscosity, free amino nitrogen, diacetyl and others were tested of six strains of lactic acid bacteria. XZ3303 and QH27-1 were growth well in soy milk and milk, and were selected as starters used in production of double protein cheeses. And optimization starter enrichment medium and freeze-drying protective agents:Skimmed milk hydrolyzed with alkaline protease 15%+glucose 2%+VC 1% can promote the growth of the two joint lactis, is the best growth medium. Skimmed milk 15%+glucose 5%+glycerol 3% +MSG 1%+VC 1% can protect L. Lactis subsp. Cremoris QH27-1 and L. Lactis subsp. Lactis XZ3303 in the freeze-drying process, and maintain a high number of viable cells to achieve good protection.Second, Optimization conditions of double protein cheese curd, the better conditions of double protein cheese curd were obtained by analyzed texture and status of double protein curd. The conditions were adding 5.98% soymilk, CaCl2 concentration was 0.44‰, rennet concentration was 7.0×10-4g·mL-1.Third, Compositions changing of double protein milk cheeses and milk cheeses during ripening were compared. The amount of lactic acid bacteria is increased firstly and then reduced gradually, through the tests in ripening time of double protein cheeses. Milk cheese made with experimental starters (NSE) and double protein cheese added soy milk made with experimental starters (ASE) have higher ripening degree. The amount of WSN,12%TCA-SN, 5%PTA-SN were increased with cheese ripening. Experimental starters have strong degradation to soy protein and casein whicn was analysis with electrophoretic. Lipases of microbe play an important role to produce short chain and long chain fatty acids in ripening time. Lipases can hydrolysis soy milk which made the species and the amount of unsaturated free fatty acids were increased in the cheeses added soy milk.Fourth, GC-MS was used on analysis flavor compounds in cheeses matured 2 months and 6 months. The species and the amount of flavor substances were increase of double protein cheeses and control cheeses in ripening time. Some kinds of alcohols, aldehydes, acids and esters have large contributions to flavor in cheese were obtained by principal component analysis (PCA). With the maturation time, double protein cheese with experimental starters received the highest scores in flavor and organizations of the sensory evaluation results.Fifth, It is no adversely effect on texture, flavor and sensory characteristics as added soy milk. L. lactis subsp. Cremoris QH27-1 and L. lactis subsp. Lactis XZ3303 can also improve the quality of double protein cheddar cheese. Double protein cheeses produced with experimental starters can improve texture characteristics and sensory quality, and are more suitable to Chinese tastes than others. It is feasibility to be widely used. Added soy milk was significantly influence the microstructure of cheeses, which made the cheeses softness, rough of surface and inner surface. The cheeses were producted with experimental starters have clesrly improved compared to the cheeses producted with commercial starters.Sixth, By amino acid composition analysis, total amino acid of double protein cheeses was significantly higher than control cheeses. From the analysis result of 16 kinds of amino acids, every kinds of amino acid in double-protein cheeses are higher than the control. The amino acids of soy protein are supplementary with milk protein, so made the double protein cheeses have more nutrition.With the antimicrobial activity trial of peptide in cheeses, four cheeses can not inhibit Staphylococcus aureus, and only double protein cheese producted with experimental starters inhibit E. coli. The substances of four cheeses all have antioxidant capacity, by the tests of the total antioxidant capacity, DPPH radical scavenging ability and hydroxyl radical scavenging ability.This article studied systematicly on cheese production process, and changes of composition, protein and fat hydrolysis, microstructure, nutrition, texture and flavor characteristics on double protein cheese using selecting starters or commercial starters, compare with pure milk cheese. It can be drawn double protein cheese making of selecting starters which is rich flavor and taste for the Chinese people had nutritious, antioxidant activity and antibacterial activity against E. coli. It was feasibility to promoting development of double protein provides.