3.4. Microbiological quality
The microbial counts in fresh mango milk powder were SPC 16.0×103, YMC 6.0×101 and spore count 12.0×101 per gram of product. The microbial counts largely depend upon the quality of raw materials used in the product preparation and the methods of processing. The type of package and temperature of storage showed significant influence on the growth and survival of microorganisms in mango milk powder (Table 3 and Fig. 3). While yeast and mold
counts decreased rapidly during storage, spores exhibited a great resistance. The death rate of bacteria was slower at 5 °C than at 30 °C. Low water activity in the product coupled with antibacterial nature of some of the chemical compounds released in various degradation
reactions may have caused rapid destruction of microbial cells during storage [31]. As the rate of chemical reactions is slow at lower temperatures of storage, the decline in microbial number was found to be slow. A decrease in microbial counts from initial numbers of
4.1×103 to 2.2×103 was also reported [32] in SMP after storage for 6 months at 30 °C.
The spore counts in MMP showed insignificant decrease during storage at 30 °C and 5 °C. Spores survive even in most adverse conditions [33]. An insignificant reduction in spore count from an initial number of 4.5×102 to 4.0×102 in high heat SMP after storage for 6 months at 30 °C is observed by Muir et al. [32].
The YMC also showed a declining trend during the entire storage period, becoming almost negligible at the end of storage study both at 30 °C and 5 °C. Yeast and mold grow at aw above 0.6. Lower aw should be one reason for the accelerated death of yeast and mold
during storage. These results are consistent with those reported by Ranganadham [21].