Retaining Bioactive Proteins and Extending Shelf Life of Skim Milk by Microfiltration Combined with Ultraviolet-C Treatment

Abstract The objective of this study was to evaluate the effectiveness of microfiltration (MF) of skim milk, alone or combined with ultraviolet-C (UVC) treatment, in extending the shelf life and retaining the native bioactive milk serum proteins, compared with high-temperature short-time (HTST) pasteurization. The vegetative bacterial load was reduced by ~3.5 log when applying M alone, by ~5 log when combining MF with UVC, while it was reduced by only ~2 log when applying HTST pasteurization. MF with UVC resulted in near complete elimination of vegetative bacteria, including coliforms. The refrigerated shelf life of skim milk was extended with increasing UVC dosage, as least for 40 days after MF combined with a UVC dosage at 39.3 mJ/cm2. An increasing UVC dosage would further reduce the bacterial load without obvious damage of bioactive milk serum proteins, such as lactoferrin, immunoglobulins, and lactoperoxidase. An LC-MS/MS based proteomics study also showed that HTST reduced the abundance of several native low-abundant milk serum proteins significantly, while MF, alone or in combination with UVC, did not change the proteome, even with higher UVC dosages. The results of this study can be used to facilitate the development of non-thermal treatments, and combinations therefore, for improving milk quality.