Adsorption removal of ochratoxin A from milk by Tibetan kefir grains and its mechanism

Abstract

Tibetan kefir grains (TKG) are microbial symbiotic starters used in various fermented foods. Recent studies have focused on removing toxin contaminants from food using TKG. This work aims to investigate the ability of TKG to remove ochratoxin A (OTA) from milk, the adsorption mechanism of TKG, and the detoxification behavior after exposure to a simulated gastrointestinal tract. The results revealed that TKG and TK removed 90.7% and 92% of OTA, respectively, while the removal capacity of isolates was low and strain-dependent (3.7%–40.7%). The limited OTA removal of freeze-dried TKG (19.6%), TKG kefiran (3.1%), and TKG protein (9.3%) indicated that the matrix network structure was critical in TKG adsorption. The effects of pH, temperature, inoculation percentage, and initial concentration on OTA removal using TKG were investigated. OTA adsorption was consistent with the Freundlich model and the pseudo-second-order kinetic model. In simulated gastric and intestinal fluids, the removal of OTA by TKG reached a maximum at 4 h with 76.1% and 75.6%, respectively. Moreover, only 33.9% of OTA was released from the TKG-OTA complex after a series of washing treatments. These findings support TKG to effectively adsorb OTA contamination in milk while fermenting and can reduce gastrointestinal absorption.