To investigate the hypothesis,Cheddar cheese were made with or without starter adjuncts that had different autolysis rate of lactic acid bacteria.Cheddar cheeses were sampled to analysis the populations of lactic acid bacteria,the changes of cheese pH value,the proteolysis by determining pH4.6 soluble nitrogen,12%TCA soluble nitrogen and performing SDS-PAGE electrophoresis at different ripening time.The results showed that 12%TCA soluble nitrogen increased with ripening time,and which were significant different between different rows after one month(P0.05).The 12%TCA soluble nitrogen in the cheddar cheese with starter adjuncts that had high autolysis rate was 8.00%,which was higher compare to the control cheese that without starter adjuncts.As the SDS-PAGE electrophoresis showed,the protein was proteolysis at a certain degree with slight difference;the autolysis of lactic acid bacteria accelerated the rate of proteolysis.
【Objective】 The antifungal activities of lactic acid bacteria (LAB) isolated from Chinese traditional fermentedproducts were detected. The selected strain was used as adjunct culture in yogurt to control the fungal pollution. 【Method】 Theproduction of phenyllactic acid (PLA) was detected with HPLC and the correlation between PLA and the antifungal activities wasstudied. Then the antifungal properties ofLactobacillus casei AST18 culture supernatants were detected. Lactobacillus casei AST18was used as adjunct culture in the yogurt production process. Four different inoculums of AST18, 2%, 4%, 6%, 8% and a controlgroup which used the commercial starter only were added in yogurt. After fermentation, sensory evaluation, physical and chemicalindicators, the fungal growth conditions were investigated. 【Result】 According to the comparison of the production of PLA and theantifungal activities, no relationship was observed between the production of PLA and the inhibition zones. The culture supematantof Lactobacillus casei AST18 was sensitive towards pH and heat treatment but it was not affected after treatment of trypsin andpepsin. The inoculums of 2% in yogurt could inhibit the growth ofPenicillium sp. and extend the shelf life. And it had no significanteffect on the flavor and sensory quality. 【Conclusion】 Lactobacillus casei AST18 can inhibit the growth of filamentous fungi conspicuously. It can be used as an adjunct culture in yogurt to prevent the fungal growth and extend the shelf life.
Used fresh cream as raw materials,investigated how the different homogenization pressure affected the diameter of fat globule,rheological properties and whipping properties,analyzed the correlation between the evaluation indicators.The results indicated that the optimized homogenization pressure is 3~5 MPa;the size of fat globules decrease and the whipping time increase with the increasing of homogenous pressure within the range of 1 to 9 MPa;on α=0.01 levels,diameter of fat globule and whipping time are significantly correlated,diameter of fat globule and overrun are significantly correlated;on α=0.05 levels,whipping time and overrun are significantly correlated.
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