Effects of Storage on Some Physico-Chemical Characteristics of UHT Milk Stored at Different Temperature

Abstract

Raw milk for UHT processing at commercial dairy plant was collected from well managed dairy farms. The milk was processed by direct system and heated at 143-145ºC for 3-5 S , then aseptically packed. Three different batches of UHT milk were used in this study. Samples of UHT milk were analysed after processing and during storage at 4, 22 and 37ºC ± 2°C for 6 months. The changes in pH, acidity as lactic acid, total solids, viscosity, fat content, electrical conductivity, specific gravity nonprotein nitrogen, non-casein nitrogen total and soluble calcium, magnesium, citrate, and phosphorus during storage were studed. The samples were analysed at 0,30,60,90,120,150 and 180 days for the physico-chemical proportes of milk. Values indicate an increase in acidity,viscocity,NCN,NPN, soluble calcium magnesium citrate and phosphate.The results showed after statistically analysis that there is a significant affect of storage period and storage temperature on pH, titratable acidity, nonprotein-nitrogen, non-casein nitrogen, viscosity, soluble and colloidal calcium and phosphate, soluble magnesium and citrate. There are a significant decrease in pH, electrical conductivity, by increasing storage period, with increasing in acidity ratio, non-protein-non-casein nitrogen and viscosity.