Assessment of Microbial Safety of Dehydrated Orange Pomace Powder

Orange pomace (OP) is a by-product of juicing process, including peels, seeds, and pulps, which are abundant in phenolic compounds and dietary fiber that could be utilized as valued-added ingredients for functional food applications. To make it for commercial use in food product development, a thorough assessment of its microbial safety is required. The objective of this study is to assess the microbial safety of the OP powder produced by a series of lab processing including pretreatment, drying, grinding and sieving steps, ultimately transforming the raw material to a shelf-stable powder ingredient. The TPC (total plate count), mold and yeast count, coliforms, E. coli, Salmonella and Staphylococcus aureus were tested for the samples of starting material and the finished powder. The preliminary results showed variations of TPC and mold yeast counts batch by batch. Specifically, pre-shredding might cause cross-contamination if the cleaning and sanitizing of lab-utensils were not standardized. However, drying (160℉ for at least 6 hours) played a crucial role in killing most coliforms and Staphylococcus aureus. SMAC, BioChrome and CompactDry plates confirmed no Salmonella and E. coli present in dried OP powder. Both TPC and mold and yeast count of OP dried powder varied from 2 to 4 log CFU/g respectively, which meets the acceptable level of industrial criteria. Clearly, it is essential to establish standardized cleaning and sanitizing practices before and after drying process, esp. on the grinding and sieving operations. The ongoing research will verify the results after implementing the standardized cleaning and sanitizing methods.