Modulation of BBI bioactivity by Maillard reaction during juice processing

Abstract

Some protease inhibitors are effective at preventing or suppressing carcinogens. Bowman Birk inhibitor (BBI) appears to be a cancer preventive agent1. A correlation between antiprotease activity and anticarcinogenesis has been suggested. BBIC (BBI concentrate) achieved the investigational new drug status from the US Food and Drug Administration2 from 1992 and it was proposed as a potential functional food ingredient in 20083. However, to the best of our knowledge this soy component has not been applied as bioactive compound in the formulation of health promoting foods and its stability to processing when is incorporated into the food matrix has not been probed. The present study aimed to evaluate how feasible is the formulation of a BBI supplemented orange juice thermally processed. Juices are adequate vehicles for supplementation but they are also very rich in reactive components. Since the inhibition domains of the BBI proteins are formed by basic amino acids its activity may be modulated by key chemical reactions taking place during food processing and storage such as Maillard reaction. The study involved orange juice samples and simplified model systems to control the influence of pH and food composition on the BBI antiprotease activity. Model systems with the natural acid pH and concentration of those foods components able to react via Maillard reaction during food processing (carbohydrates and ascorbic acid) were prepared. Thermal processing was performed under pasteurization (60ºC, 10 min) and sterilization (121ºC, 20 min) conditions. Pasteurized samples were kept at 4ºC for two months mimicking commercial storage. BBI structural changes due to processing and storage were analyzed by SDS-PAGE and MALDI-TOF-MS while the protein bioactivity was assessed as described by Clemente et al4. According to our findings both sterilization and storage in refrigeration for 2 months affected the antitrypsin bioactivity of BBI in supplemented orange juice and model systems but not the antichymotrypsin activity. Mass analysis confirmed the formation of early Maillard reaction products involving the lysine residue of the trypsin inhibitory domain during sterilization. Data derived from this investigation is of high relevance and helpful for the formulation of BBI-supplemented juice containing therapeutic doses of the bioactive protein and for the selection of other food matrices for supplementation with this potentially anticarcinogenic food component.