Properties of pyrodextrinization corn starch and their inhibitory effect on the retrogradation of fresh rice noodles.

This study was aimed to investigate the properties of pyrodextrins under different preparation conditions and the effects of pyrodextrins on the retrogradation of fresh rice noodles. Pyrodextrins were made by heating corn starch with and without lactic acid at 180 °C ranging from 1 to 6 h. The molecular weights of pyrodextrins gradually decreased, whereas the branching degree increased and the chain length shrank with the prolongation of heating time. The changes of acid-heat-treated pyrodextrins were more pronounced than those of dry-heat-treated pyrodextrins under the same treatment time. The acid-heat-treated pyrodextrins displayed higher water solubility and lower viscosity, suggesting that they could no longer gel. These results suggest that starch retrogradation could be limited by pyrodextrins, especially acid-heat-treated pyrodextrins. Then, the pyrodextrins were added to fresh rice noodles and the eating and cooking qualities were examined during storage. After 35 days of storage, the pyrodextrin with acid heating at 180 °C for 4 h showed the most effective inhibition on starch retrogradation and was suitable for fresh rice noodles as an anti-retrogradation agent. The study might supply new perspectives on restraining starch retrogradation and promoting the fresh rice noodle industry.

Effects of different extrusion temperatures on the physicochemical properties, edible quality and digestive attributes of multigrain reconstituted rice.

Multigrain reconstituted rice, as a nutritious and convenient staple, holds considerable promise for the food industry. Furthermore, highland barley, corn, and other coarse cereals are distinguished by their low glycemic index (GI), rendering them effective in mitigating postprandial blood glucose levels, thereby underscoring their beneficial physiological impact. This study investigated the impact of extrusion temperature on the physicochemical properties, edible quality, and digestibility of multigrain reconstituted rice. The morphology revealed that starch particles that are not fully gelatinized in multigrain reconstituted rice are observed at an extrusion temperature range of 60 °C-90 °C. As the extrusion temperature increased, the degree of gelatinization (DG) increased, while the contents of water, protein, total starch, and amylopectin decreased substantially. Concurrently, the relative crystallinity, orderliness of starch, and heat absorption enthalpy (ΔH) decreased significantly, and water absorption (WAI) and water solubility (WSI) increased markedly. Regarding edible quality, sensory evaluation displayed an initial increase followed by a decrease. In terms of digestibility, the estimated glycemic index (eGI) increased from 61.10 to 70.81, and the GI increased from 60.41 to 75.33. In addition, the DG was significantly correlated with both eGI (r = 0.886**) and GI (r = 0.947**). The results indicated that the ideal extrusion temperature for multigrain reconstituted rice was 90 °C. The findings underscored the pivotal role of optimal extrusion temperatures in the production of multigrain reconstituted rice, which features low GI and high nutritional quality.

Understanding the Relationship between the Molecular Structure and Physicochemical Properties of Soft Rice Starch.

The relationship between the molecular structure and physicochemical properties of soft rice starch (SRS) has been investigated in this research. The amylose content of SRS ranged from 10.76% to 11.85%, classified as the very low amylose type. Compared to waxy and japonica rice starch, the largest amount of small starch granules and the highest viscosity were shown in the SRS. The results of X-ray diffraction and Fourier transform infrared proved that the SRS depicted a typical A-type pattern with a low short-range ordered structure. Additionally, SRS had a great deal of A and B1 chains. Molecular weights and density of starch from soft rice were lower than those from waxy rice but higher than those from japonica rice. Furthermore, SRS possessed a higher amount of resistant starch. Correlation analysis indicated that the amylose content and the chain-length distributions of amylopectin play a major role in influencing the molecular structure and physicochemical properties of rice starch. In conclusion, the low amylose content, highest viscosity, and other excellent properties of soft rice starch make it have bright application prospects in instant rice and rice cakes.

Understanding the deterioration of fresh brown rice noodles from the macro and micro perspectives.

The microbial compositions, quality characteristics, and structural changes in fresh brown rice noodles (FBRN) during storage were investigated. Total plate count and mold and yeast counts increased while the pH decreased during storage. Metagenomic sequencing revealed that the microbial composition of FBRN changed throughout storage. A comprehensive investigation of the variation in lipid content demonstrated that hydrolytic rancidity was responsible for lipid deterioration. LF-NMR showed an increase in the proportion of bound water and a decrease in the proportion of free water in FBRN. Moreover, significant changes in edible qualities were observed. The cooking loss increased three-fold and noodles hardness reduced by approximately 23%. Further, the high initial aldehyde content of FBRN diminished almost completely, while that of alcohols and esters increased, leading to significant flavor deterioration. The correlation and factor analysis suggested that the TPC and MY counts could be used as key indicators of FBRN deterioration.