Whey protein isolate modified with sodium tripolyphosphate gel: A novel pH-sensitive system for controlled release of Lactobacillus plantarum

Abstract

It is of great significance that lactic acid bacteria reach the intestinal tract successfully with the assistance of protective carriers. In this paper, novel pH-sensitive hydrogels based on whey protein isolate (WPI) grafted sodium tripolyphosphate (STP) due to their non toxicity and biodegradability, were synthesized and utilized as new carrier for specific pH-sensitive controlled Lactobacillus plantarum (L. plantarum) release. Evidences of STP grafting were extracted from FTIR, while the morphological structure of modified protein hydrogel was investigated by scanning electron microscopy. Factors affecting on the pH responsiveness and gel hardness were studied. The protection of L. plantarum in simulated gastric juice was evaluated as a function of STP addition and protein concentration. The swelling behavior of the modified WPI gel showed sensitivity to environmental pH as the amount of STP added was 9%, which shrunk in acidic system and stretched in alkaline environment. The modified WPI (9% STP, 5% protein) gel had the strongest protective effect on L. plantarum, and the survival rate of the strain increased by 6.41 log after being soaked in acidic environment (pH 2.0) for 30 min compared with control. Accordingly, grafting of STP has controlled release profile behavior. The preliminary results clearly suggested that the WPI-STP hydrogel may be a potential candidate for intestinal specific release of active substances.