The changes in goat milk during heating and storage after milking

In this study, the changes in goat milk were investigated during heating at different temperatures and storage in different packaging materials. For this purpose, samples from a farm producing goat milk in Bolu were divided into two groups, the first group was pasteurized at 65 °C for 30 minutes (LP) and the second group at 95 °C for 5 minutes (HP). Each group of pasteurized milk samples was again divided into two group and filled into different packaging containers (transparent glass and amber glass). The trial was conducted in two replicates. Samples were taken from raw milk and heat treated milks and on 0th, 5th and 10th days of storage period (+4 °C). Viscosity, sedimentation and color changes and also pH, acidity, dry matter, fat, protein, alkaline phosphatase, total hydroxymethylfurfural (HMF), nonenzymatic browning compounds (EOEB) and vitamins A, E, B1, B2 and B12 were observed in milk samples. In the samples taken after the heat treatment applied to the raw goat milk, the heat treatment caused the increase of the dry matter ratio in the goat milk samples (P<0.05); but it did not cause any significant change in fat, acidity and viscosity values (P>0.05). The pH and sedimentation values of the milk samples increased significantly (P<0.05) in the samples heated with HP, while the L* value of the color values increased as the heating value increased. The effect of heat treatment on vitamin values was not significant (P>0.05). In heat treated milk samples, HMF and EOEB values increased as the heating temperature increased (P<0.05). The milk samples heated by LP and HP methods were packed in different packaging materials and the changes that occurred during storage were also observed. There was no significant difference in the dry matter, fat and protein values of goat milk samples throughout storage (P>0.05). The acidity values of the samples increased during storage. Values of pH were not significant (P>0.05) among the samples heated with LP and HP and stored in different packages. The HMF and EOEB values of the LP and HP milk samples were different (P<0.05), while the packaging difference and the storage effect were not significant (P>0.05). The effects of pasteurization on investigated vitamins with LP and HP, storing in different packaging materials and storage at different times were negligible (P>0.05). Sedimentation values were found to be high in milk heated by HP method and on the 10th day of storage. L* values of the color parameters of the samples were found to be significant (P<0.05) between LP and HP milk. Also, L* and a* values were affected by storage (P<0.05).