Chemical composition, density, pH and protein profile of goat milk and goat cheese whey elaborated with 3 different fat contents

Abstract

Majorera goat milk with three different fat content (5%, 1.5% and 0.4% fat) were obtained using a skimmer and goat cheese were prepared by traditional method from Canary Islands (Spain) with these 3 types of milk. Milk and cheese whey samples were analyzed for: pH, gross chemical composition and density; percentage of proteins was determinate with electrophoresis in SDS-PAGE gel. It was observed that milk pH decreased as fat content was lower. However cheese whey pH decreased slightly as milk fat content was lower but no statistically significant differences between the three types of whey were observed. The remaining fat percentage in cheese whey was significantly minor as milk fat content was reduced (remaining 10, 4 and 0% cheese whey fat content from full-, reduced- and low-fat milk, respectively). The protein in milk decreased slightly as fat is removed by centrifugation. Protein content in whey was 3 times lower than in milk but no significant differences were found between the three types of cheese whey. Lactose in milk ranged from 4.5 to 5%, increasing significantly as fat content decreased. However the whey obtained from the three cheese making process showed similar lactose content. Lactoferrin, serum albumin, beta-lactoglobulin and alpha-lactalbumin passed without changes of concentration from the milk to the whey and no significant differences were found in these proteins. Moreover, no significant differences were found in the percentage of these proteins between the 3 different types of milk used, so the protein profile of cheese whey have not been modified by the centrifugation. After skimming beta-casein showed a statistically significant increase although is was shown a slightly increase in the alphas2-casein concentration. A difference of whey proteins, alphas2-casein, beta-casein and kappa-casein were not detected in cheese whey. The 2% of alphas1-casein was detected in all types of cheese whey of total milk protein, thus, part of this protein was lost with the cheese whey. In conclusion: as it was expected, all whey proteins were detected on whey after cheese making. There was also evidenced a small proportion of alphas1-casein independent of the treatment of the milk. Cheese producers must take account of the important losses they are having in cheese whey. Whey chemical composition, specially in the full-fat milk cheeses, had relative high total solids so it can be used to produce ricotta or other milk product. The optimum milk fat content should be established in order to minimize fat losses in the cheese whey however it Ls also possible to reuse the cheese whey when cheese are elaborated with high fat milk.