The Quality of The UHT Skim Milk as Affected by Addition of Rennet Skim Milk

Background and Objectives: Consumption of whole dairy products has declined due to the awareness of possible harmful effects of fat on consumers’ health. The purpose of the present paper was to investigate the possibility of substituting the Ultra-high temperature processing (UHT) whole milk with partially hydrolyzed κ-casein to manufacture a UHT skim milk. Materials and Methods: UHT skim milk samples were prepared using 0.2, 0.4, 0.6 and 0.8 % (w/w) of rennet followed by storage at 60°C for 15 minutes to inactivate the enzyme. The Chemical, physical and sensory characteristics of control and treated samples were evaluated. Statistical analysis was performed by SPSS. Results: The results showed that a higher concentration of rennet increased and decreased b* (blue–yellow) and a* (green–red), respectively (p<0.05). The regression profiles of viscosity plotted against heat stability of samples show a polynomial relationship (R2= 0.96). The zeta value of treatment samples was significantly lower than the absolute value of CUSM (Control UHT skim milk with 0.3% fat). There is a correlation between the appearance viscosity and average particle size (R2= 0.92). The skim milk consisting of 0.6% of rennet skim milk did not have any significant regarding aroma, taste and texture from those of the control UHT whole milk (p<0.05). Conclusions: The result showed that, RSM4 (Renneted UHT skim milk with 0.3% fat and 0.8 % (w/w) rennet) has similar characteristics to whole milk and it is also clear in viscosity and sensory evaluation among other samples. It has been noted that non-dairy components were not used in RSM4 and the new production can be a very functional and safe fat mimetic by merely changing the structure of casein micelles.