Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2015
Publication Date: 6/28/2016
Citation: Ukuku, D.O., Onwulata, C.I., Mukhopadhyay, S., Thomas-Gahring, A.E., Chau, L.I., Tunick, M.H. 2016. Changes in microbial populations of WPC34 and WPC80 whey protein during long term storage. Journal of Food Processing and Preservation. doi: 10/1111/jfpp.12743.
Interpretive Summary: Whey protein (WPC34 and WPC80) has been used as a food ingredient and as a base for making food product. The need to alleviate world hunger in arid and semi-arid regions demands that we investigate the behavior of spoilage bacteria in these products, especially during long term storage. Two types of bags were used to store WPC34 and WPC80 under normal and adverse storage conditions for 2 years. The overall microbial populations in WPC34 and WPC80 did not change during storage at normal conditions. There was a slight variation on bacterial populations in samples stored at higher temperature and humidity than those under normal storage. Storage bags did not affect bacterial survival however; certain bags were discarded due to formation of off odor. The results of this study suggest that storage temperature at 25 up to 30 deg C at ambient relative humidity is the best storage condition for the WPC34 and WPC80.
Technical Abstract: The use of whey protein (WPC34 and WPC80) as a food ingredient and as a base for making biodegradable products is increasing. The need to alleviate world hunger in arid and semi-arid regions demands that we investigate the behavior of native bacteria in these products, especially during long term storage. Therefore, the aim of this study was to investigate the behavior of aerobic mesophilic bacteria and spoilage organisms in WPC34 and WPC80 stored at ambient relative humidity and temperature, including those stored at 30 and 35 degrees C with relative humidity (RH) of 70 and 90%. WPC34 and WPC80 were placed inside bags marked as standard (Std.) and high performance (HP). The bags were stored at the conditions listed above for 24 months. Before storage, the initial colony forming unit (CFU/g) of aerobic mesophilic bacteria, yeast and mold, coliform, lipolytic bacteria and lactobacillus were estimated on tryptic soy agar, dichloran rose bengal chlortetracycline (DRBC), violet red bile agar (VRBA), spirit agar + lipase reagent and all purpose tween 80 (APT) agar, respectively. During storage for 24 months, samples were withdrawn every 3 months to investigate the behavior of the organisms listed above. WPC80 had higher initial microbial populations than WPC34. Surviving populations for all bacteria in WPC34 and WPC80 stored in std and HP bags at ambient humidity and temperature did not change significantly (p>0.05) for 24 months. Significant changes in bacterial populations were noted in samples stored at 30 and 35 degrees C and 70 and 90 RH, and in some samples, spoilage organisms were below detection. The results of this study suggest that storage conditions at ambient humidity and temperature is best followed by storage at 25 degrees C and 70 RH.