Influence of Annealing on Gel Properties of Mung Bean Starch

Abstract

Cereal Chem. 77(5):567-571Mung bean starch gels (8% solids) were prepared after annealing at 45-60°C for 1-24 hr, and the relationship between the physical properties of gels and the swelling power (SP) and solubility of starch was investigated. The SP and solubility decreased with increasing annealing temperature and time, mostly in the first 6 hr. The solubles were mainly composed of amylose. Gel hardness at a 5 mm depth of annealed starch was larger than that of native starch, and gel hardness increased as SP decreased (r = -0.94). Upon continued compression, the yield force of gel showed a different function. Above SP of ≈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 force. Although annealing increased the gel hardness, α-amylase digestibility 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°C annealed starches. Overall paste viscosities of the starches annealed at >55°C were lower than that of the control starch. Final viscosities in RVA were correlated with the yield force of gel (r = 0.99).Starch granules heated in excess water undergo an order-disorder phase transition called gelatinization (Hoover 1995). This phase transition is associated with the diffusion of water into the granule, hydration and swelling of the starch granules, loss of crystallinity, and amylose leaching. As a consequence, swollen granules become embedded in a continuous matrix of entangled amylose molecules. On cooling, the complex composite sets as a viscoelastic gel when starch concentration is >6%. This change is called retrogradation. In this stage, amylose gel network develops relatively fast and remains unchanged during storage. Meanwhile gelation of amylopectin within the swollen granules is slow and progresses slowly during storage, resulting in increasing gel hardness (Biliaderis and Zawistowski 1990, Morris 1990, Biliaderis 1992. Hoover (1995) reviewed the factors affecting starch retrogradation such as starch concentration, temperature, sugar, lipids, salts, and chemical and physical modification.Annealing is a process in which starch granules are heated in excess amounts of water at a temperature slightly below gelatinization temperature for a relatively long time. Tester et al (1998) reported that annealing was restricted unless the moisture content exceeded 60% by weight of the mixture. Annealing decreases swelling power and solubility of starch (susceptibility to amylase (Wang et al 1997), and changes pasting curves (Jacobs et al 1995, Stute 1992.Mung bean starch, along with acorn and buckwheat starches, is widely used to make a gel food called mook in Korea. Mook is prepared by cooking at 8-10% solids followed by cooling the paste in a rectangular or circular plate with a depth of ≈10 cm. Since mook is served with chopsticks, it requires a certain g...

Influence of heat–moisture treatment and annealing on functional properties of sorghum starch

“…The increase in gel hardness may be attributed to the decrease in fraction of gel volume on ordering rearrangement of starch molecules caused by annealing (Chung, Moon, & Chun, 2000). Hormdok and Noomhorm (2007) also reported an increase in gel hardness upon ANN and HMT treatment but with different treatment conditions from that of present study were used.…”

Effects of tempering (annealing), acid hydrolysis, low-citric acid substitution on chemical and physicochemical properties of starches of four yam (Dioscorea spp.) cultivars

“…Native white yam starch had the highest FV (9231cP) compared to native starches of the other cultivars. Tempering significantly increased FV of the native starches, and this could be attributed to the amount of leached-out amylose that remained unchanged during pasting, leading to formation of a continuous gel matrix (Chung et al 2000). However, acid hydrolysis and citric acid substitution significantly reduced FV, probably due to the considerable loss of amylose during pasting.…”

Acid hydrolysis of native and annealed starches and branch-structure of their Naegeli dextrins

“…1,2 The pasting properties 3,4 and the susceptibility to enzymatic hydrolysis 5 of annealed starch are also affected. Although annealing does not change the wide-range X-ray pattern, 2,6 a slightly sharpened pattern and a decreased background have been observed for annealed starches by small-angle X-ray scattering.…”