Freeze-dried rabri powder: Product development and quality evaluation

The formulation for rabri powder based on milk was standardized using response surface methodology. The milk was concentrated in a steam kettle till moisture content decreased up to 66%. Freeze-drying was carried out at 60 degrees C and 0.1 mm of Hg pressure to achieve a final moisture content of 2.4%. Increased functional properties were achieved with the addition of almond and pistachio nuts. The product provides 494 kcal of energy/100 g. Quality evaluation with respect to chemical, microbiological and sensory characteristics were carried out during storage of the product at ambient temperature (28 +/- 5 degrees C). Total fatty acid profile of the product, initially and during storage was evaluated by gas chromatography and a significant decrease (p<0.05) was observed in the percentage of linoleic and linolenic acids during storage. Saturated fatty acids varied marginally. Even though the values of thiobarbituric acid reactive substance and free fatty acids increased during storage, the product was sensorily acceptable up to 6 months storage at 28 +/- 5 degrees C. Microbiologically the product did not show any increase in the standard plate count as well as yeast and mold counts. The pathogens Escherichia coli, Salmonella and Staphylococcus aureus were absent throughout the storage period indicating the microbial safety of the product.