This work investigated the impact of high intensity ultrasound (HIUS) pretreatment on the functional properties and structural characteristics of micellar casein concentrate (MCC). Microfiltered casein protein retentates were treated with HIUS for 0.5, 1, 2, and 5 min prior to spray drying. The results showed that conductivity, solubility, emulsifying, gelling increased significantly as the ultrasonic time prolonged, but the change of pH value were insignificant. In addition, the structural characteristics of MCC for all samples were studied. There was an increase in surface hydrophobicity (Ho) and a reduction in particle size compared with the control (without HIUS pretreatment). The secondary structure of HIUS pretreated MCC samples changed significantly with an increase in β-sheets and random coils and a reduction in α-helix and β-turn. It can be speculated that HIUS pretreatment facilitate the change of functional properties of MCC and these changes would promote its application in food industry.

The gut microbiota plays important roles in chronic inflammation and colon cancer. Lactobacillus is a gut-resident probiotic with benefits to host health. We recently identified Lactobacillus plantarum strain YYC-3 with strong inhibition against two colon cancer cell lines (HT-29 and Caco2). However, the inhibitory effect of YYC-3 against colon cancer in vivo has not been verified. Thus, in the present study, we explored the probiotic function of strain YYC-3 and its cell-free supernatant (YYCS) respectively in the APCMin/+ mouse model of colon cancer during tumour development and growth, and the underlying anti-cancer mechanism. Treatment of both strain YYC-3 and the YYCS prevented the occurrence of colon tumours and mucosal damage in APCMin/+ mice fed a high-fat diet, although YYC-3 had a stronger anti-cancer effect. The mechanism involved modulation of the immune system and downregulated expression of the inflammatory cytokines interleukin (IL)-6, IL-17 F, and IL-22, along with reduced infiltration of inflammatory cells. Moreover, YYC-3 suppressed activation of the NF-κB and Wnt signalling pathways, and restored the altered gut microbiota composition to closely match that of wild-type mice. These results lay a theoretical foundation for application of YYC-3 in colon cancer prevention.