Transglutaminase Effects on the Rheological Characteristics of Peanut Flour Dispersions

Introduction: Peanuts (Arachis hypogaea L.) are a stable food commodity around the world. In the last few decades, peanut flour has been used as a food ingredient. Previously, microbial transglutaminase (TGase), an enzyme that catalyzes protein cross-linking via acyl-transfer reactions (1) was shown to modify functional properties of food systems including viscosity, solubility, and water holding capacity. Objective: Characterization of rheological properties of roasted peanut flour-12% fat (PF) dispersions containing amidated pectin (AP) crosslinked with TGase. Methods: Dispersions (20% w/w) were heated from 40° to 90oC at 1°C/min and subsequently cooled to 40oC while continuously monitoring rheological changes. Small strain rheological measurements were conducted under a stress of 1.5 Pa, frequency = 0.1 Hz, a value identified to be within the linear viscoelastic region. PF fractions (+/-) TGase and (AP) were analyzed with SDS-PAGE electrophoresis and the O-Phthaldialdehye assay (OPA). Results: Figure 1 indicates TGase treated PF dispersions had increased gelling temperature (~78°C) after 7 hrs incubation compared to untreated samples (~68°C). Others have noted increased gelling temperature for whey and soy upon treatment with TGase (2, 3). Figure 2 showed PF (+) AP treated with TGase under incubation (24 hrs) resulted in formation of a high molecular weight polymers on the SDS-PAGE gel. OPA assay (Figure 3) showed ~10% coupling of PF after treatment with TGase PF dispersions prepared with AP after incubation for 6 hrs. AP was added to the dispersions to increase gel strength and water holding capacity.