Yung-Ho Chang

Effect of granular characteristics on pasting properties of starch blends.

Pasting and morphology properties of starch blends composed of waxy (waxy rice and waxy corn) and non-waxy (normal corn, tapioca and potato) starches at various ratios were investigated for elucidating effect of granular characteristics on pasting of blends. Pasting profiles of blends were between those of the component starches alone, while the changes varied with starch source. Results reveal obvious water competition during pasting for blends composed of waxy starch and highly swelling non-waxy (tapioca or potato) starch. On the contrary, starch blends composed of waxy starch and non-waxy (normal corn) starch with restricted swelling showed less water competition during pasting, and the pasting attributes could be estimated from those of the component starches following the mixing ratio. Results indicate that the pasting properties of starch blends composed of waxy and non-waxy starches depend on not only the mixing ratio, but also the granular characteristics of component starch.

Molecular Structure and Physicochemical Properties of Acid-Methanol-Treated Chickpea Starch

The molecular structure and physicochemical properties of acid-alcohol-treated (0.36% HCl in methanol at 25°C up to 216 h) chickpea starch were investigated. The recovery for modified chickpea starch ranged from 82 to 91%. A significant decrease in the swelling power, pasting viscosity, and gel strength was observed upon treatment with acid-methanol; however, the granule morphology remained unchanged. Structural studies revealed preferential degradation of amylose and long-chain amylopectin during treatment and the same was attributed to cause alterations in the functional properties. Molecular studies further revealed that the lower content ratio of short-chains to long-chains of amylopectin in chickpea starch resulted in the faster degradation rate upon acid-methanol treatment. An exponential model was also developed from the average molecular weight data to illustrate the degradation kinetics of acid-methanol-treated chickpea starch.

Genotype diversity in structure of amylopectin of waxy rice and its influence on gelatinization properties

A set of 13 waxy rice genotypes prepared by chemically-induced mutation of non-waxy rice variety TNG67 and 7 waxy rice varieties widely planted in Taiwan were screened for various structural and gelatinization properties of starches. Wide variation on physicochemical properties and molecular structure of amylopectin for the 20 waxy rice starches were obtained and relationship between gelatinization properties and molecular structure of starch were discussed. More attributes on swelling and gelatinization thermal properties, comparing to pasting attributes, showed significant correlation with molecular structure parameters. The swelling and gelatinization thermal properties of waxy rice starch did not show significant correlation with molecular size of amylopectin, while significant correlations were found between the swelling or gelatinization thermal properties and chain length of amylopectin. Results suggest that the swelling and pasting of waxy starch is essentially dominated by granule architecture and is dependent on the interactions among amylopectin chains.

Instrumental Textural and Rheological Properties of Raw, Dried, and Cooked Noodles with Transglutaminase

Textural and rheological properties of raw, dried, and cooked noodles with microbial transglutaminase were evaluated by an instrumental texture analyser. Generally, the strength of the noodles significantly increased with microbial transglutaminase concentration from 0 to 1.0%. The cutting force of raw noodle is a good indicator to predict the strength of dried and cooked noodle products. Mechanical stress relaxation data of cooked noodles were fitted well by both Maxwell and Peleg-Normand models. The fitted parameters, λ1 and k2, were more sensitive to the changes in viscoelastic properties than k1 and %SR. Significant correlations were found between textural characteristics and stress relaxation parameters. Results of this study suggest that dried or cooked noodle with good quality can be produced by incubating with 0.5–1.0% microbial transglutaminase for 30 min at 30u2009°C.

Indigestible pyrodextrins prepared from corn starch in the presence of glacial acetic acid

This study was conducted to evaluate the feasibility of using acetic acid (0-2.5%) as the catalyst in the production of pyrodextrins from corn starch at 140-180u202f°C, and to elucidate the effects of catalyst concentration and pyrolytic temperature on the characteristics of indigestible pyrodextrins. In the absence of acetic acid, noticeable changes to the loss of birefringence, increased solubility, plateau of molecular weight reduction, decreased reducing sugar content and digestibility were observed at 180u202f°C. By using catalyst, the alterations in the aforementioned characteristics of pyrodextrins were intensified. Moreover, by using 0.5-1.0% catalyst, the substantial alterations in birefringence, solubility and molecular weight were observed concurrently for pyrodextrins formed at 170u202f°C. Further increasing the concentration of acetic acid to 1.0-2.5% decreased the intervening temperature to 160u202f°C. The findings suggest that indigestible pyrodextrins with desired characteristics could be tailored via using various combinations of catalyst concentration and pyrolytic temperature.