Influence of annealing on gel properties of mung bean starch

Mung bean starch gels (8% solids) were prepared after annealing at 45-60 de grees C for 1-24 hr, and the relationship between the physical properties o f gels and the swelling power (SP) and solubility of starch was investigate d. The SP and solubility decreased with increasing annealing temperature an d time, mostly in the first 6 hr. The solubles were mainly composed of amyl ose. Gel hardness at a 5 mm depth of annealed starch was larger than that o f native starch, and gel hardness increased as SP decreased (r = -0.94). Up on continued compression, the yield force of gel showed a different functio n. Above SP of approximate to 12.5, the yield force of annealed starch gels decreased, but at <12.5 the yield force increased with increasing SP. Both granular rigidity and extent of packing appeared to determine the yield fo rce. Although annealing increased the gel hardness, alpha-amylase digestibi lity of gel was not affected. Pasting analysis in the Rapid Visco Analyser (RVA) revealed that annealing increased pasting temperature. A pasting peak was found only in 45 and 50 degrees C annealed starches. Overall paste vis cosities of the starches annealed at >55 degrees C were lower than that of the control starch. Final viscosities in RVA were correlated with the yield force of gel (r = 0.99).