Modification in physical properties of rice gel by microbial transglutaminase

BACKGROUND: Microbial transglutaminase (MTGase) may catalyse the cross‐linking between a peptide‐bound glutaminyl residue and an ε‐amino group of lysine residue in protein. MTGase has been used to modify many food proteins for improving the physical properties of products. However, its effect on the physical properties of rice products has not been investigated before. The present study aimed to investigate the effect of MTGase, as an additive in rice flour, on the rheological, textural and thermal properties of rice gel. RESULTS: Both the elastic and the viscous moduli of rice gel were increased as a result of the addition of MTGase to rice flour. The addition of MTGase at 0.01–0.3 U mg^?1 increased textural parameters (hardness and gumminess) and rheological properties. Differential scanning calorimetry also showed that MTGase treatment decreased the enthalpy change in gelation. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) confirmed that rice proteins were polymerised through the MTGase reaction. CONCLUSION: The present study proved that the cross‐linking of protein molecules in rice flour by the action of MTGase may improve the physical properties of rice gel. The addition of MTGase in rice flour in an adequate amount is essential for achieving appropriate physical properties of the product. Copyright © 2008 Society of Chemical Industry