Food Structure


Khoa, a partially dehydrated milk product indigenous to India, was prepared from buffalo milk by boiling it vigorously in an open pan and reducing its volume to approximately 25% within 30 min. The hot semi-solid product (Khoa pat) was held at 20•c for 3 h (fresh, cooled Khoa) or 48 h (swred Khoa); the products were either worked with a pestle in a mortar for 5 min or were left without working.

Structural features of Khoa were studied by light microscopy and electron microscopy. Freshly prepared coo led Khoa had a granular structure consisting of protein granules several hundred micrometers in diameter. The granules consisted of intact and partly fused casein micelles and nonmicellar protein . The fresh product was only slightly sandy in the mouth. Large aggregates of lactose crystals developed in the intergranular spaces in unworked Khoa during swrage and sandiness in the stored product was markedly increased. Working reduced the dimensions of the protein granules and the intergranular void spaces and produced large amounts of fat globule membrane fragments. Individual lactose crystals in worked Khoa stored at 20°C for 48 h were more uniformly distributed than in unworked Khoa. Storage did not increase sandiness in the worked product; sensory analysis rated this product to be markedly smoother than unworked stored Khoa.

Instrumental measurements showed that working significantly decreased hardness and springiness and increased adhesiveness and, to a smaller extent, cohesiveness.

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