Enzymatic hydrolysis of wheat gluten employing cysteine proteases from noni fruits (Morinda citrifolia L.)

Abstract

Previous reports have shown that noni (Morinda citrifolia L.) puree extract (NPE) is a promising source of cysteine peptidases with potential applications in the food industry. This study expanded the applications of cysteine peptidases from noni fruit by analyzing their potential for wheat gluten hydrolysis and assessing their in vitro toxicity as a new food ingredient. NPE cysteine proteases hydrolyze both gliadins and glutenins, reaching a degree of hydrolysis of 24.40% and 31.78%, respectively. In addition, they reduced gliadin content by 96.80% after 4 h of incubation, as displayed by the R5 ELISA test kit for detecting gliadin based on the monoclonal antibody R5. The chromatographic fractionation of NPE cysteine proteases on a cation exchange column (Source 30S) resulted in an unretained peak (P1) and a retained peak (P2), which showed proteolytic activity with different electrophoretic and zymographic profiles. P1 and P2 had similar (p < 0.05) degrees of hydrolysis for gliadins (approximately 9%). P1 performed better (10.68%) than P2 (8.55%) for glutenins. NPE cysteine proteases did not exhibit genotoxicity or cytotoxicity against mouse fibroblasts (L929 cell line). These findings suggest that NPE cysteine proteases have potential for use as novel ingredients to produce gluten-free foods.