High-amylose and Tongil type Korean rice varieties: physical properties, cooking behaviour and starch digestibility

Retrogradation behaviors of damaged wheat starch with different water contents

The retrogradation behaviors of five damaged wheat starches (DS) after milling 0, 30, 60, 90, and 120 min with different water contents (33, 50, 60 %) were evaluated. Milling treatment increased DS content and developed an agglomeration of small particles. After 7 days of storage, the recrystallinity and long-range ordered structure of starch pastes were increased with the contents of DS and water. This process led to a lower setback viscosity and poor leaching of amylose. LF-NMR indicated a conversion from tightly bound water and free water to weakly bound water. During storage, DS12 with 60 % water content had the highest retrogradation tendency where the retrogradation enthalpy increased by 1.5 J/g and 2.2 J/g compared with DS0 with 60 % and DS12 with 33 % water content. DS with higher water content promoted the water mobility and made the starch molecular chains migrated conveniently. These changes facilitated the recrystallinity process during retrogradation period.

Retrogradation-induced physicochemical changes in pre-cooked rice noodles stored at different temperatures: a viewpoint from water dynamics and structure

BACKGROUND

There has been significant interest in pre-cooked noodles that have a long shelf life and are convenient to cook. However, the thermal processes during preparation, and their high moisture content, can lead to significant quality deterioration during storage. Nevertheless, a comprehensive evaluation of these quality losses has not yet been conducted.

RESULTS

The effects of different storage temperatures (25, 4, and -20 °C) on the retrogradation-related physicochemical changes in pre-cooked rice noodles were elucidated mainly from the water dynamics and structural viewpoints. Thermal analysis demonstrated that amylopectin recrystallization took place in the noodles stored at refrigerated temperature, followed by room temperature. The refrigerated storage accelerated the starch retrogradation that caused the water molecules to become entrapped within the crystalline structure by lowering the water hydration properties and weighted T2 relaxation times of the pre-cooked noodles. These water mobility patterns were correlated with the textural changes in the noodles (greater hardness and Rmax /extensibility). Furthermore, the higher structural density and thickness derived from starch retrogradation were observed in the tomographic and microscopic images of the refrigerated noodles. The principal component analysis demonstrated that various physicochemical changes of the pre-cooked noodles during storage showed high correlations with the degree of starch retrogradation (r > 0.83).

CONCLUSION

The physicochemical features of the precooked noodles stored under refrigerated conditions were involved in the molecular dynamics of water, showing a notable water mobility reduction derived from the starch retrogradation, which contributed to their thermal, tomographical, and textural changes. © 2023 Society of Chemical Industry.

Pasta from Red Lentils (Lens culinaris): The Effect of Pasta-Making Process on Starch and Protein Features, and Cooking Behavior

The effect of pasta-making processes on starch and protein features, as well as cooking behavior, and nutritional properties (i.e., resistant starch and starch in vitro digestibility) were assessed. Pasta from raw red lentils (R) was prepared by conventional extrusion (C_R) and extrusion-cooking (EC_R), whereas heat-treated red lentils (HT) were processed into pasta by conventional extrusion (C_HT). A "high protein" and "high fiber" pasta was prepared. Using HT was effective in increasing the luminosity (that was about 88, 91, and 96 for EC_R, C_R, and C_HT, respectively), and decreasing the presence of defects on the pasta surface (heterogeneity was 5%, 36%, and 45% for C_HT, EC_R, and C_R, respectively). Heat treatment on grains or flour significantly increased starch susceptibility to α-amylase (6.6, 7.4, and 8.6% for C_R, C_HT, and EC_R, respectively) and decreased the final viscosity (from 335 BU in C_R to 287 and 291 BU in EC_R and C_HT), resulting in a significant increase in starch digestibility (slowly digestible starch was about 41, 27, and 26% in C_R, C_HT, and EC_R, respectively). As regards proteins, the main effect on their structure was observed in C_HT, where the cooking behavior was much improved and cooking losses were lowest (5.7%). On the other hand, protein and starch organization in EC_R might have accounted for pasta resistance in overcooking.