Physical characteristics during storage of soy yogurt made from ultra-high pressure homogenized soymilk

The effects of ultra-high pressure homogenization (UHPH) on soymilk for producing soy yogurts and their evolution during cold storage for 28 days (analysis were performed on days 1, 7, 14, 21 and 28) were investigated. Soy yogurts were prepared from UHPH-treated soymilk preheated at 50 degrees C at 200 and 300 MPa. Moreover a combined treatment at 300 MPa with a retention time of 15 s (at the temperature reached after the high pressure valve) was investigated. Soymilk treated at 95 degrees C for 15 min (HT) was used as control. This study included the evaluation of viscoelasticity by dynamic oscillation, puncture test, microstructure by laser confocal microscopy, water holding capacity (WHC) determination and colour evaluation. Results showed that soy yogurts from UHPH-treated soymilk presented higher values of mechanical parameters related to firmness and G*, and better WHC. In addition, soy yogurts maintained these positive characteristics during cold storage. However, in UHPH soy yogurts colour parameters showed some differences compared to control which may indicate changes in chemical compositions in addition to the colloidal characteristics of these products. (C) 2008 Elsevier Ltd. All rights reserved.