酪蛋白和工艺对再制稀奶油稳定性的影响

Effect of Caseins and Processing Conditions on Stability of Recombined Dairy Cream

本研究主要通过测定再制稀奶油的粒径、界面蛋白含量、黏度、微流变性质分析胶束酪蛋白浓缩粉(micelle casein concentrate,MCC)、酪蛋白酸钙(calcium caseinate,CaC)粉及工艺(灭菌、二次均质)对再制稀奶油稳定性的影响。结果表明:蛋白添加量为1.0%(质量分数,后同)和2.0%时,MCC再制稀奶油的失稳系数分别为0.396±0.011、0.032±0.001,说明稳定性随蛋白添加量的增加而提高,而CaC再制稀奶油稳定性的变化规律与之相反。灭菌后,MCC再制稀奶油脂肪球粒径D3,2、界面蛋白含量及黏度显著增加(P<0.05),均方根位移(mean square displacement,MSD)明显降低,CaC再制稀奶油与MCC再制稀奶油的变化明显不同,除界面蛋白含量由3.9~5.5 mg/m^2增至5.2~7.0 mg/m^2外,粒径D3,2、黏度及MSD(2.0%CaC再制稀奶油除外)无明显变化。二次均质后,MCC再制稀奶油脂肪球粒径D3,2、界面蛋白含量及黏度显著下降(P<0.05),MSD明显增加,而CaC再制稀奶油样品中除1.0%CaC再制稀奶油粒径D3,2由(2.80±0.10)μm下降至(2.06±0.11)μm外,其他理化性质变化不明显。虽然MCC乳化能力较CaC低,但其在添加量2.0%时制备的稀奶油稳定性最好。工艺会导致再制稀奶油(尤其是MCC再制稀奶油)理化性质间平衡的改变,再制稀奶油的稳定性也随之改变。

The present study was carried out to evaluate the effects of micelle casein concentrate(MCC),calcium caseinate(CaC)and processing conditions(sterilization and two homogenization cycles)on the stability of recombined dairy cream as assessed by measurement of particle size,interfacial protein concentration,viscosity and microrheological properties.The results showed that the instability indexes of MCC cream with MCC concentration of 1.0%and 2.0%(m/m)were 0.396±0.011 and 0.032±0.001,respectively,suggesting a better stability at higher MCC concentration.However,an opposite trend was observed for CaC cream.An significant increase was observed in the D3,2(P<0.05),adsorbed protein amount and viscosity of MCC cream after being subjected to sterilization,and the mean square displacement(MSD)value decreased significantly.However,no apparent change was observed in the D3,2,viscosity or MSD of CaC cream(except for the MSD of 2.0%Ca C cream),while the adsorbed protein amount increased from 3.9–5.5 to 5.2–7.0 mg/m^2.After the second homogenization,the D3,2,adsorbed protein amount and viscosity of MCC cream decreased significantly(P<0.05),whereas an increasing trend was observed in MSD values.The D3,2 of 1.0%Ca C cream decreased from(2.80±0.10)to(2.06±0.11)μm,whereas no significant change occurred in other physicochemical parameters.The 2.0%MCC cream exhibited the best stability among all the recombined cream despite the fact that MCC showed poorer emulsifying capacity in comparison with CaC.Furthermore,the balance among the physicochemical characteristics of recombined dairy cream and consequently its stability changed to some extent after sterilization and secondary homogenization(in particular for MCC cream).