Abstract

A study was carried out to investigate the effect of spray dryer variables namely atomizer type and inlet air temperature and additive type on the various quality attributes of probiotic apple juice powder. The results revealed that increasing inlet air temperature from 150°C to 170°C reduced the moisture content, bulk density, water activity, survival of Lactobacillus acidophilus and increased the solubility of the spray dried probiotic apple juice powder. The moisture content, bulk density and water activity of the spray dried probiotic apple juice powder ranged between 1.93 and 4.92 per cent (w.b), 0.416 and 0.693 g/cm3 and 0.236 and 0.391 respectively. Among the atomizers and additive materials studied, rotary wheel atomizer and maltodextrin showed reduced level of moisture content, bulk density and water activity compared to gum arabic and twin fluid pressure nozzle atomizer. It was evident from the results that, gum arabic added probiotic apple juice, spray dried using rotary wheel atomizer recorded the highest solubility value. The maximum survival (L.acidophilus) of 31.43 per cent was achieved for the powder obtained using twin fluid pressure nozzle atomizer, 150°C inlet air temperature and maltodextrin as additive material. Compared to gum arabic and rotary wheel atomizer, maltodextrin and twin fluid pressure nozzle atomizer showed good survival of L.acidophilus. Based on the above results, maltodextrin, rotary wheel atomizer and 160°C inlet air temperature were optimized for spray drying of probiotic apple juice.

Keywords: Apple juice, spray drying, Lactobacillus acidophilus