Exploring the Impact of Varying Fat Content on Milk Properties During Ohmic Heating: A PCA Study of Viscosity Changes Alongside pH Fluctuations

Abstract

Background: Some of the factors that contribute to the quality of milk include fat content, pH, viscosity and other rheological aspects. This research extensively investigated the effects of ohmic heating (OH) on milk viscosity, along with other rheological attributes and pH. Methods: Milk samples with varied fat constituents were subjected to OH at a constant voltage of 140V until they reached a temperature of 90°C. The pH of raw milk and heated milk was determined using an auto-pH meter, whereas the viscosity of the same was measured using a Brookfield viscometer that includes a wide range of characteristics, such as viscosity, temperature, shear stress and torque at various spindle rotation speeds. The current investigation used Principal Component Analysis (PCA) as a key statistical approach. Result: The pH values exhibited little fluctuations during OH across several milk kinds, indicating mild acidification throughout the process, but the observed alterations did not reach statistical significance (p greater than 0.05), suggesting that OH does not significantly affect milk pH. Viscosity measurements showed that the application of OH resulted in a decrease in the average viscosity of milk, suggesting changes in its ability to withstand shear forces. The correlation study revealed robust positive associations between viscosity and fat content (PC2 - 26.77%), as well as between rotational speed, shear rate and torque (PC1 - 53.72%) and a negative correlation with temperature, offering valuable insights into the dynamic properties of milk when subjected to thermal heat treatment.