MICROSTRUCTURE AND MACRO-STRUCTURE OF COW, BUFFALO AND MIXED MILK RASOGOLLA - A COMPARATIVE SCANNING ELECTRON AND LIGHT-MICROSCOPE STUDY

Scanning electron and light-microscopic studies were carried out to provide information on the micro- and macro-structural differences between cow, buffalo and mixed milk rasogolla (a local Indian milk product obtained via acid coagulation followed by cooking in sugar syrup). Scanning electron microscopy of cow milk rasogolla revealed a loose, porous protein matrix with coalesced casein micelles forming a thread-like structure, while buffalo milk rasogolla had agglomerated casein micelles which were large and compact, and formed a scale- or layer-type structure. Casein micelles in mixed milk rasogolla formed a combination of thread- and scale-type structures. Fat globules collapsed and the membrane shrank noticeably in all the 3 samples. Larger fat globules were most affected, while little or no effect was observed in small fat globules. Light microscopic investigation showed that cow milk rasogolla had smooth, small oval-shaped pores, whereas buffalo milk rasogolla had rough-edged, irregularly-shaped large pores. Mixed milk rasogolla had a heterogenous structure. The Instron and sensory textural examination agreed well with the compositon and structural characteristics of rasogolla.