Abstract:
This study was aimed at determining the effects of fat content and homogenization pressure on the apparent viscosity of coconut milk. The percentage of fat content in coconut milk samples was varied from 15 to 30 percent and the samples were homogenized at 4/4 MPa, 7/4 MPa, and 11/4 MPa. The results were compared with those of non-homogenized coconut milk. Experimental stress-shear rate relationships, obtained at 25 0C, were described by using the power law model. All coconut milk samples exhibited mildly shear-thinning behavior. The magnitudes of the n values were between 0.85-0.98. It was also found that solid-non-fat (SNF) did not affect the apparent viscosity of samples. Reduction of the fat content resulted in a significant (P ? 0.05) decrease in the apparent viscosity and the K value but a significant increase in the n value. Homogenization did not affect the n value but it significantly increased the apparent viscosity and the K value of the samples. An increase in the homogenization pressure decreased the fat globule size from 2.2 ?m to 0.92-1.62 ?m. Among all samples, coconut milk homogenized at 11/4 MPa gave the highest K value and the smallest fat globule size. An empirical correlation of apparent viscosity versus homogenization pressure and fat content, at a shear rate of 300 s-1, was established to be: 0.0812H)0.0678C0.0011exp(napp+= Where napp = Apparent viscosity (Pa.s) C = Concentration expressed as fat content (%) H = First-stage homogenization pressure (MPa)