A New Strategy for Specific Qualities of Waxy Rice Breeding by Analyzing Physicochemical Properties Between Five Waxy Mutants and Corresponding Their Wild Types

Waxy rice is an essential mutant type of rice, which quality is controlled by amylopectin fine structure and apparent amylose content (AAC). The influence of amylopectin structure and AAC on quality and the waxy rice can be obtained by editing the Waxy (Wx) gene have been elucidated. However, the quality of waxy rice cannot be predicted before breeding, especially how to determine the quality of waxy (wx) mutants by wild types (WT) quality remains unclear. Herein, the quality of waxy rice has been successfully predicted through analyzing the association in physicochemical properties before and after Wx gene knockout. We demonstrated that the higher amylose WT would obtain higher amylose wx mutants, and wx mutants were endowed gelatinization temperature, amylopectin chain ratio and agronomic traits similar to WT. These data indicate that the quality of wild varieties played a decisive role in waxy rice breeding. Overall, we provide a new strategy for the specific quality breeding of waxy rice, which can get waxy rice of prescribed quality and contribute to expanding the particular type of waxy rice germplasm resources.

Pasting Properties of Various Waxy Rice Flours: Effect of α-Amylase Activity, Protein, and Amylopectin

Waxy rice is one of the most popular traditional crops served as a staple food in China. In this study, the effect of different factors including α-amylase activity, protein, and amylopectin structure on the pasting properties of four waxy rice varieties were investigated. Rice flours treated with AgNO3 solution, DL-dithiothreitol (DTT) or protease, suggested that both α-amylase activity and protein significantly decrease the pasting viscosity of waxy rice flours. Chain length distribution of amylopectin as measured by high performance ion exchange chromatography (HPAEC-PAD) showed that starch with higher ratio of short chain leading to a higher pasting viscosity. X-Ray diffractograms showed that the crystal type of all the four varieties of rice starches were characteristic A-type. Relative crystallinity of each rice starch was further calculated, and a higher crystallization resulted in a higher viscosity. Our study would provide a fundamental knowledge of the relationship between different factors and waxy starch pasting properties, as well as be a reference for controlling the quality of waxy rice starch-based food.

Effects of Pectin on the Physicochemical Properties and Freeze-Thaw Stability of Waxy Rice Starch

In this study, the effects of the addition of pectin (PEC) on the physicochemical properties and freeze-thaw stability of waxy rice starch (WRS) were investigated. As PEC content increased, the pasting viscosity and pasting temperature of WRS significantly increased (p < 0.05), whereas its breakdown value and setback value decreased. Differential scanning calorimetry showed that the addition of PEC increased the gelatinization temperature of WRS, but decreased its gelatinization enthalpy. Rheological measurements indicated that the addition of PEC did not change the shear-thinning behavior of WRS–PEC blends, and the storage modulus and loss modulus were positively correlated with PEC content. Moreover, the textural parameter of WRS decreased with the increase in PEC content. Furthermore, the addition of PEC decreased the transmittance of starch paste, but enhanced the freeze-thaw stability of WRS to some extent. These results may contribute to the development of WRS-based food products.

Effects of Spray-Drying Inlet Temperature on the Production of High-Quality Native Rice Starch

Rice starch is a common functional ingredient used in various food applications. The drying regime to obtain dry starch powder is an important processing step, which affects the functional properties of the starch. The application of extreme thermal treatment during the conventional drying process tends to elicit irreversible changes to the rice starch, resulting in the loss of desired functionalities. In a previous study, we reported the development of a novel low temperature spray-drying based process which efficiently dries waxy rice starch, while preserving its physicochemical properties and functionalities. This study, a follow-up to the previous report, evaluated the effect of different spray-drying inlet temperatures on the production yield, physicochemical properties, and functionalities of waxy rice starch. Increasing the inlet temperature from 40 °C to 100 °C resulted in an increase in the process yield from 74.83% to 88.66%, respectively. All spray dried waxy rice starches possessed a low moisture content of less than 15%, and a consistent particle size (median ~6.00 μm). Regardless of the inlet temperatures, the physicochemical functionalities, including the pasting characteristics and flowability, were similar to that of the native waxy rice starch. The molecular and A-type crystalline structure of the waxy rice starches were also conserved. An inlet temperature of 60 °C represented the optimum temperature for the spray-drying process, with a good yield (84.55 ± 1.77%) and a low moisture content (10.74 ± 1.08%), while retaining its native physicochemical functionalities and maximizing energy efficacy.

Applications of waxy corn flour based on physicochemical and processing properties: comparison with waxy rice flour and waxy corn starch

The proximate composition, molecular weight distribution and main processing properties of waxy corn flour (WCF) were investigated. Furthermore, waxy corn starch (WCS) and waxy rice flour (WRF) were also determined to discuss the applications of WCF. WCS contained more low-molecular-weight fraction (<5 × 105 g/mol) and had higher polydispesity than waxy rice starch (WRS). The water hydration capacity of WCF was the lowest, whereas it had the highest swelling power at 70 and 80 °C. WCF had the highest pasting temperature of 74.85 °C, whereas that of WRF was 68.40 °C and WCS was 73.25 °C. WRF exhibited the lowest melting enthalpy change with a value of 2.54 ± 0.11 (J/g). The retrogradation resistance of WCF was better than that of WRF and WCS. The degree of retrogradation (DR) of WCF was 9.58 ± 0.59% at 14 d, corresponding to WCS of 25.08 ± 0.44% and WRF of 15.68 ± 0.71%. WRF had the lowest glass transition temperature of −27.4 versus −26.2 °C for WCF and −26.0 °C for WCS. It was found that WCF could be used to directly prepare quick-frozen viscous foods. It could also be used as a stabilizer to improve the quality of staple foods.

Physical Properties of Different Cultivar Local Glutinous rice (susu and siding) and Commercial Thai Cultivar

Glutinous rice (Oryza Sativa var. glutinosa) is known as waxy rice or sticky rice and it has an opaque and small size grain cultivar distinct from common white rice. In outlining the equipment for processing, storage, sorting, sizing and other post-harvest equipment the particular of their physical properties is important. Two different cultivar of local glutinous rice susu and siding were evaluated in this study. For susu cultivar, the average of length, width, and thickness were 6.63mm, 1.88mm, and 1.50mm respectively. The corresponding values were 6.24mm, 1.98mm, and 1.48mm for siding cultivar. For susu cultivar, the average of aspect ratio, sphericity, volume, surface area, bulk density, true density, porosity, 1000 weight kernel, and angle of repose were 0.28, 0.40%, 9.81mm3, 19.02mm2, 800.54 kg/m3, 1500.36 kg/m3, 46.65%, 18.88g, and 39.45°. Thecorresponding values were 0.32, 0.42%, 10.25mm3, 19.45mm2, 772.73 kg/m3, 1229.51 kg/m3, 37.15%, 17.04g and 40.08° for siding cultivar. Thus, the objective of this study is to compare the physical properties of two different local cultivars aid in designing the rice processing equipment.