Quality Characteristics of Mango Soy Fortified Yoghurt Powder During Drying and Storage

摘要

Mango Soy Fortified Yoghurt (MSFY) samples were prepared in the laboratory using optimized blend formulation including type of stabilizer and its addition level. These samples were subjected to drying process in a recirculatory convective air dryer under varying hot air temperatures (45, 50, 55℃), air velocity (1.5, 2.0, 2.5 m/s) and product thickness (3, 4, 5 mm). Effects of the drying process parameters on quality characteristics viz. yoghurt bacteria count, acetaldehyde retention, colour change and dispersibility of the MSFY samples were studied. Drying process variables were optimized for maximum retention of quality attributes in the MSFY powder using Response Surface Methodology (RSM). The optimum conditions for recirculatory convective drying of MSFY were 45°C hot air temperature, 2.5 m/s air velocity and 3 mm product thickness. The MSFY samples dried under these conditions had maximally survived S. thermophilus (1.73 x 10~8 cfu/g) and L bulgaricus (1.27 x 10~8 cfu/g), maximum retention of acetaldehyde (43.7%), better dispersibility (55.9%) and minimum colour change (1.35). Mango soy fortified yoghurt (MSFY) powder was packaged in pouches of high density polypropylene (HDPP) and pouches of aluminium laminated polyethylene (ALP) pouches. The storage stability of MSFY powder in terms of quality parameters, free fatty acid (FFA), thiobarbituric acid (TBA), hydroxymethyl furfural (HMF), starter counts and colour change were studied in both packaging materials. The magnitude of quality change of MSFY powder measured during storage suggests that ALP was better than HDPP.