EFFECT OF DIFFERENT HEATING TEMPERATURES ON THE RHEOLOGICAL PROPERTIES OF LACTIC GEL MADE FROM BUFFALO MILK

Abstract

Heat treatment and acidification are the fundamental processing technologies for the development of fermented dairy products with desired attributes. Before lactic acid gel formation, milk is heated to destroy the microorganisms, to increase shelf life, to improve texture and ultimately to improve the quality of final products. The main aim of this study was to evaluate the rheological properties particularly texture of buffalo milk lactic acid gel made from different heat treatments i.e. 80^oC, 85^oC, 90^oC and 95^oC. The products formed by the respective treatments was further subjected to physicochemical (pH and acidity), compositional (protein fractions (total protein, non-protein nitrogen, non-casein nitrogen), fat, ash, total solids, moisture, lactose and minerals), rheological (synersis, viscosity and texture profile analysis), microbiological (total viable count and coliform count) and sensory analysis during storage of 14 days at refrigeration condition with an interval of 7 days. The rheological and organoleptic properties of lactic gel samples were influenced by different heating temperatures and storage time. There was significant difference in rheological parameters between the samples and the storage time. Lactic gel prepared at 90^oC showed highest sensory scores and has better texture at the end of storage period. The viable count increased during storage and the coliform count remained negative throughout the storage period; however a significant difference in compositional parameter were observed between the samples and storage time. Changes in titratable acidity and pH showed significant difference during storage. Results indicated that different heating temperatures significantly affected the overall quality of lactic gel during storage.