Evaluation of physical properties during storage of set and stirred yogurts made from ultra-high pressure homogenization-treated milk

The effects of ultra-high pressure homogenization (UHPH) on cow's milk were investigated and its Suitability for yogurt manufacturing was compared with the conventional process Currently applied in the yogurt industry. Yogurts were prepared from UHPH-treated milks at 200 and 300 MPa at 40 degrees C, and yogurts prepared from heat-treated milk at 90 degrees C for 90s, homogenized at 15 MPa and enriched with 3% of skim milk powder were used as control samples. This Study included determination of titrable acidity, water-holding capacity (WHC), and textural and rheological evaluation of gels in both set-type and stirred yogurts. In order to follow the evolution of yogurts during storage at refrigeration temperature (4-6 degrees C), all analyses were carried out weekly (L 7 K 21 and 28 days). Results showed that yogurts from UHPH-treated milk presented higher WHC and firmness values compared with the conventional yogurts. However, the disruption of the network from UHPH-treated milk into stirred gels resulted in yogurts with higher consistency, less syneresis but coarser structure than the conventional ones. (C) 2008 Elsevier Ltd. All rights reserved.