Research On Character Of Actinomucor Elegans And Its Application In Novel Mould Cheese

This study was designed in order to develop new type cheese,post matured by moulds isolated from Chinese traditional food——preserved beancurd,sufu.According to the investigation on proteinase-producting activity,growth character and spores production ability,the optimal mould was chosen as among and the sample obtained was studied for the physical and chemical indexes,compared with the triditional soft mould cheese.Through single factor experiment,the mould of Actinomucor elegans was accepted as the optimal strain for the novel cheese production,where similar processing parameters were detected to the triditional moulds stains of Penicillium camembert.Further on,the optimal fermenting condition was fixed at 28℃,3 days,bran:water was 1:1.3.The concentration range of(NH4)₂SO₄ graduation precipitation was 40%-80%.Results indicated that the enzyme was stable under 55℃and could be inhibited when NaCl more than 6%,which was activated by Ca²⁺,Mg²⁺ and Fe²⁺ and inhibited by Ag⁺ and Cu²⁺. Hydrolysis experiment indicated that this proteinase had good hydrolysis ability,which was most active at pH 7.0-8.0 and the temperature period of 35-55℃.To obtain optimal conditions for mucor growth and spores production ability,orthogonal experiments were conducted and the results showed as sucrose 3%,NaNO₃ 3%,ZnSO₄ 0.07%,where the sporulation reached 3.41×10⁸cfu/mL.Investigation on mucor on cheese physical and chemical indexes showed that during ripening water content declined from 59%to 50%and the pH of surface and inner increased all along and reached pH7.0 in the end,while the content of lactic acid decreased from 1.2%to 0.4%and pH4.6 SN and 12%TCA SN increased from 10.1%and 2.5%to 45.2%and 27.1%respectively.During ripening,the total free fatty acid content reached 6.54%,among which 37.8%were unsaturated fatty acid.Further studied indicated that TPA hardness decreased from 450g to 150g during ripening and the microstructure had a significant change in 30 days of post maturation,when the structure of protein was disappear and the cheese texture turned smooth and uniform.MIR inspection proved consistency between spectrum and physical and chemical indexes.Composition of the cheese sample was analyzed with moisture 51.0%,protein 22.0%, fat 21.6%and salt content 2.1%,accordant to CODEX-STAN C-33 standards of soft cheese. HS-SPME-GC-MS was utilized to analyze the volatiles compounds in mucor cheese,where the main compounds were esters 28.65%,alkanes 22.88%,acids 19.69%,ketones 17.74%, alcohols 6.40%and others 4.64%;sensory evaluation showed that after 30 days ripening, the novel cheese post matured with Actinomucor elegans had acceptable quality,compared with the traditional.