Development of a novel milk processing to produce yogurt with improved quality

Abstract

In this study, a thermal treatment (T, 85 °C) assisted by short-wave ultraviolet C light (UV-C, 1060 mJ/cm 2 ) under vacuum conditions (400 mmHg) (TV-UVC) is proposed for milk processing, intended to improve some yogurt quality aspects during refrigerated storage (4 °C). In addition, thermal treatment (T) and UV-C light assisted by T without using vacuum (T-UVC) were evaluated for comparison purposes. The TV-UVC treatment was the most effective one, eliminating coliforms and effectively reducing mesophilic counts (4 log-reductions). The effect of the proposed TV-UVC treatment on physicochemical properties, texture, and sensory characteristics of yogurt was studied during storage. TV-UVC yogurt showed 60% less syneresis and highest white index, while exhibiting similar mechanical properties compared to T yogurt during 21-day refrigerated storage. Non-significant changes among all treatments were determined on all evaluated physicochemical parameters during storage (soluble solids, pH, and titratable acidity). Cluster analysis revealed that a group of consumers was very interested in the product; however, some improvements in vanilla and sour taste should be introduced in order to increase overall acceptability. These results suggest that UV-C light assisted by heat and vacuum would represent a promissory alternative for milk processing aimed at yogurt manufacturing.