Optimization of Processing Conditions to Improve the Rehydration and Sensory Properties of Freeze-Dried Cooked Rice

Abstract

This study investigated the effects of baking powder (BP) concentration, cooking temperature (CT) and freezing temperature on the rehydration ratio of freezedried cooked rice (FDCR). Rehydration ratios increased with higher BP concentration in soaking solutions, with 0.3% being considered the optimal concentration. Greater rehydration ratios were recorded at a CT of 120C than 100C. Rapid freezing (-70C) produced small intracellular ice crystals, whereas slow freezing (-20C) produced large ice crystals, causing a higher ratio of initial water absorption. The combine-treated FDCR, which was soaked in 0.3% BP, cooked at 120C and frozen at -20C, had a larger porous and spacious structure, as well as the highest degree of rehydration. Significantly higher stickiness/hardness ratios and sensory acceptability were obtained for the combined treatment compared to the conventional treatment (cooked at 100C and frozen at -70C). These results indicate that these preparation conditions could improve the sensory properties of FDCR at consumption. PRACTICAL APPLICATIONSWith the changing socioeconomic pattern of life, convenient foods are becoming popular because they save time and labor. The result of this research could be applied to manufacture ready-to-cook rice-based dried foods of improved sensory quality and quick preparation time.

Effect of Soaking Conditions and Fuzzy Analytical Method for Producing the Quick-Cooking Black Jasmine Rice

“…At room temperature being used as the soaking temperature, the increased baking powder concentration increased the rehydration capacity, however, the baking powder concentration of 0.3 and 0.5% was not different. This was in accordance with Song et al [ 3 ] who stated that the higher concentration of baking powder used, the higher the rehydration ratio of rice. This can be explained by the gas production of baking powder causing the space in the final QBJR structure after the drying process, which improves the rehydration capacity of the samples.…”

“…The physical properties and also microstructure of cooked rice has been improved by using baking powder [ 3 ] and also by adjusting the soaking temperature and soaking time [ 5 ]. The Quick Black Jasmine Rice were differently pretreated with baking powder solutions of 0.1, 0.3, or 0.5% at room temperature, 50, and 60 °C for 10, 20, and 30 min.…”

“…The dried rice quality has been affected by the processing condition which caused the physical properties of the product such as rehydration and microstructure to change, and also caused the bioactive compound concentrations to vary. Song et al [ 3 ] stated that the microstructure of cooked rice during drying affected the rehydration properties, which were improved and resulted in a high quality of the final product. Therefore, the processing of QBJR, namely baking powder concentration, soaking temperature, and soaking time, on rehydration capacity, microstructure, and also the texture of final product were studied.…”

“…Oikonomopoulou, Krokida, and Karathanos [ 2 ] reported that the cooking methods affect rice’s structural properties including its porosity, bulk density, and the true density of the final sample in which the vacuum employed during freeze-drying increased the bulk density but decreased the porosity of the grain. Song et al [ 3 ] studied the effects of baking powder concentration, cooking temperature, and freezing temperature on the quality of freeze-dried cooked rice. They found that the higher baking powder concentrations increase the rehydration ratios of the final sample.…”

Impact of Low-Temperature Storage on the Microstructure, Digestibility, and Absorption Capacity of Cooked Rice

“…Differing from the refrigerated cooked rice, most frozen cooked rice samples developed porous structures due to the formation of ice crystals during storage and exhibited a marked dependence on the storage temperature: the higher the temperature, the larger the pore size. Likewise, Song et al revealed that the pore sizes of freeze-dried cooked rice stored at −70 °C were smaller than those of the samples stored at −20 °C and −10 °C [ 40 ]. The difference in the porous structures may depend on the size distribution of ice crystals, and the latter is also closely related to the freezing rate [ 41 , 42 ].…”