Darwish, M., El-Awady, A., Abd-ElSalam, R., Mostafa, M. (2023). The Influence of High Heat Treatment at Alkaline pH on the Physicochemical Characteristics and Isomerization of Lactose to Lactulose in Skim Milk. Journal of Food and Dairy Sciences, 14(9), 207-214. doi: 10.21608/jfds.2023.227934.1125
M. S. Darwish; Asmaa A. El-Awady; Rana Abd-ElSalam; M. S. Mostafa. "The Influence of High Heat Treatment at Alkaline pH on the Physicochemical Characteristics and Isomerization of Lactose to Lactulose in Skim Milk". Journal of Food and Dairy Sciences, 14, 9, 2023, 207-214. doi: 10.21608/jfds.2023.227934.1125
Darwish, M., El-Awady, A., Abd-ElSalam, R., Mostafa, M. (2023). 'The Influence of High Heat Treatment at Alkaline pH on the Physicochemical Characteristics and Isomerization of Lactose to Lactulose in Skim Milk', Journal of Food and Dairy Sciences, 14(9), pp. 207-214. doi: 10.21608/jfds.2023.227934.1125
Darwish, M., El-Awady, A., Abd-ElSalam, R., Mostafa, M. The Influence of High Heat Treatment at Alkaline pH on the Physicochemical Characteristics and Isomerization of Lactose to Lactulose in Skim Milk. Journal of Food and Dairy Sciences, 2023; 14(9): 207-214. doi: 10.21608/jfds.2023.227934.1125
The Influence of High Heat Treatment at Alkaline pH on the Physicochemical Characteristics and Isomerization of Lactose to Lactulose in Skim Milk
Dairy Department, Faculty of Agriculture, Mansoura University, Mansoura 35516, Egypt.
Abstract
The pH of the skim milk was modified, first increased from 6.5 to 7.5, then subjected to high heat treatment at 95°C for 2 min or left unheated for 1 hour. Subsequently, the pH was adjusted back to 6.5, and the samples were analyzed. The concentration of lactulose in skim milk showed a significant increase due to High heat treatment (HHT) (p < 0.05), and this effect was more pronounced when the pH was raised from 6.5 to 7.5 before HHT. Raising the pH of both high heat-treated (HHT) and unheated (UH) skim milk from 6.5 to 7.5 before heating or holding led to an extended heat coagulation time (HCT) at pH 7.2 and resulted a 58.7% increase in the dissociation of κ-casein in HHT milk compared to the total κ-casein content. The adjustment of pH had no significant (p < 0.05) influence on the chemical composition of the high heat-treated skim milk and ethanol stability in the pH range of 6.2-7.2). Besides heating the sample at 95°C for 2 min resulted in a significant decrease in casein micelle size (CMS). These findings offer a foundation for focusing on the negative impact of alkalinization before high heat treatment on casein dissociation, CMS, thermal and alcohol stabilities. Additionally, it is regarded as a promising approach with the potential to enhance the lactulose content in milk.
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