Effect of Gamma-irradiation on the Physicochemical, Functional, and Antioxidant Properties of Unpigmented Brown Whole Rice Flour

Whole grain brown rice, being a rich source of fiber and other bioactive compounds like polyphenols is effective in reducing the risk of chronic diseases including cardiovascular diseases, hypercholesterolemia and Type II diabetes. The study was aimed to evaluate the effect of gamma irradiation on the physicochemical, functional and antioxidant properties of whole grain brown rice flour. The brown rice flour was conditioned to two different moisture contents of 10% and 12% and treated with gamma irradiation doses of 0 kGy (native or control), 2.5 kGy and 5 kGy. Moisture, protein, fat, ash and carbohydrate content of native flour was found as 10 g/100 g, 6.54 g/100 g, 1.54 g/100 g, 1.0 g/100 g, and 81.48 g/100 g, respectively. The hunter color ‘L’, ‘a’, and ‘b’ values of the native brown rice flour sample were found as 81.95, −0.97 and 17.36, respectively and were non-significantly ( p ≥ 0.05) affected by gamma irradiation. Apparent amylose content was observed to decrease significantly ( p ≤ 0.05) from 29.97 to 20.30 g/100 g with the increase in gamma irradiation dose and moisture content. The pasting properties such as peak viscosity, trough viscosity and final viscosity of all the flour samples decreased significantly ( p ≤ 0.05) with the increase in irradiation dose. The functional properties such as water and oil absorption and emulsion capacities were increased while emulsion stability and foaming stability decreased upon irradiation. Irradiation led to an overall increase in the antioxidant activity of rice flours. In general, FTIR spectra revealed a decrease in the absorption intensities of the functional groups. Therefore, it can be concluded that gamma irradiation can be used as a tool to modify the physicochemical properties of rice flours as well as to improve their antioxidant properties.

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.

Texture and Digestion Properties of Cooked Rice and Rice Noodles

Rice varieties high in amylose content have low glycemic and insulin responses. Rice noodles are processed by extrusion from high amylose content rice, which may also have low glycemic and insulin responses. In this study, cooked rice and rice noodles processed from two high amylose content cultivars, Guangluai4 (GL4) and Zhenguiai (ZGA), were chosen for in vitro starch digestion evaluation. Apparent amylose content of cultivars (i.e., GL4-28.4% and ZGA-26.8%) and pasting properties except final viscosity were significantly different between the cultivars. In vitro starch digestion results showed that the glucose production rate in rice noodles was significantly slower than that in cooked rice by 65.7% and 42.0% in GL4 and ZGA, respectively. The main reason for low glucose production in rice noodles was active digestion duration longer in rice noodles than in cooked rice, which reflects the slow release of glucose during starch digestion. The texture of rice noodles in the GL4 and ZGA cultivars is 3 and 2.3 times harder than that of cooked rice, respectively. Thus digestive enzymes can hardly enter the interior of rice noodles for amylolysis. As a result, the digestion time of rice noodles is longer, and the release of glucose during digestion is slower than that of cooked rice. The slower release of glucose during rice noodle digestion may be beneficial for prolonging satiety and reducing food intake. Consequently, eating rice noodles may help in improving or preventing diabetes and obesity over time.

Development of Caryopsis and Starch Physicochemical Properties in Different Grain Positions of Wheat Spikelets

Background: Spikelets at different spike positions and the caryopsis at different grain positions grow and develop differently. The caryopsis development and physicochemical properties of starch at different grain positions (the first, second, and third grain positions: G1, G2, and G3) of wheat spikelets were investigated in this study. Results: During the development process, the thickness of both dorsal and abdomen pericarp 8 days after anthesis (DAA) followed the sequence G2 < G1 < G3. However, at 14 DAA the thickness followed the dorsal sequence of G1 < G2 < G3 and the abdomen sequence of G2 < G1 < G3. At 20 and 30 DAA, no difference existed in the pericarp thickness of each grain. The accumulation quantities before 20 DAA varied with starch and protein of endosperm cell in the order G1 > G2 > G3. In mature caryopsis, the caryopsis size and weight indicate that G1 = G2 > G3. The starch content followed the order G1 > G2 > G3, while the essential amino acid, the total amino acid, and the protein content followed the order G2 > G1 > G3. The apparent amylose content followed the sequence G3 > G2 > G1, and A-type starch content followed G3 > G1 > G2. The amorphous ratio followed the order G2 > G1 > G3, whereas the double-helix ratio and the relative crystallinity exhibited the opposite trend. The order of the final degree of hydrolysis through AAG, PPA, and HCL was G2 > G1 > G3. Conclusions: The different material contents were possibly due to the short development time of caryopsis, and the difference in starch physicochemical properties between G2 and the other grain positions might be related to the components and structural characteristics of starch.

Grain Quality and Starch Physicochemical Properties of Chalky Rice Mutant

Rice mutants with altered starch components and properties are important genetic resources for grain quality and starch structure analysis. Accordingly, in the present study, two mutants of the transcription factor OsbZIP09 were generated (osbzip09a and osbzip09b), and the rice grain quality and physicochemical starch properties of the mutant and wild-type lines were compared. The OsbZIP09 mutants exhibit a chalky grain owing to loosely packed, small, spherical starch granules in the ventral region of the endosperm. Furthermore, grain-quality profile analysis showed that OsbZIP09 deficiency leads to increased apparent amylose content but decreased gel consistency. Structural analysis of the mutant starches revealed that the mutant rice lines contain more amylopectin short chains and fewer intermediate chains, leading to lower crystallinity and lower gelatinization properties than those of the wild-type rice. Moreover, the OsbZIP09 mutants rice presented a significantly higher pasting curve and corresponding parameters than the wild-type rice. The results from this work strongly indicate that the transcription factor OsbZIP09 plays an important role in rice grain quality and starch fine structure modification, and extend our understanding of starch biosynthesis in rice endosperm.

Comparative Study of Physicochemical Properties and Starch Granule Structure in Seven Ginkgo Kernel Flours

Ginkgo biloba L. is an important economic tree species in China, and its kernels have been used as a popular food in Asian countries. Herein, the morphology, basic chemical components, starch granule structures, and physicochemical properties of kernel flours from seven ginkgo cultivars were investigated, and their relationships were analyzed. The kernels were oval or spherical in shape, with variable sizes. The starch granules exhibited both regular and irregular Maltese cross patterns. Amylose was mainly distributed in amorphous growth rings. A spatial variation in the 865/942 cm−1 ratio was observed within individual starch granules. Variations in total starch content, apparent amylose content (AAC), crude protein content (CPC), total amino acid content (TAAC), starch fine structure, and thermal and pasting properties were observed among the seven kernel flours. Pearson correlation coefficients and principle component analyses showed that the thermal properties were affected by kernel CPC, TAAC, AAC, and starch fine structure, while the pasting properties were affected by AAC and starch fine structure. Furthermore, experiments showed that the seed protein structure and α-amylase activity affected the pasting properties of ginkgo kernel flours.

Variability in waxy (Wx) allele, in-vitro starch digestibility, glycemic response and textural behaviour of popular Northern Himalayan rice varieties

Eight commonly cultivated and consumed rice varieties of Northern Himalayan regions and a popular high amylose rice variety were characterized at Wx locus and evaluated for resistant starch (RS), in-vitro starch digestibility, predicted glycemic index (pGI), glycemic load (GL) and textural parameters. Cytosine and thymine repeats (CT)n at waxy locus (Wx) showed high association with apparent amylose content (AAC). Both pGI and GL varied substantially within the selected varieties. The pGI was relatively lower in high and intermediate amylose Indica varieties compared to low amylose Japonica ones. However, Koshikari despite being a low amylose variety showed relatively lower pGI and GL, due to its higher RS, dietary fiber, protein and fat content. It was thus presumed that in addition to AAC, RS and other grain components also affect the glycemic response. Inherent resistance to enzymatic hydrolysis was also found to be higher in firm textured and less sticky rice varieties. The genotypes—Lalat, Basmati-1509 and Koshikari, in view of their low to moderate pGI and relatively higher RS content, can be explored in future breeding programmes to develop rice varieties whose consumption will help to prevent hyper/hypo glycemic responses in Northern Himalayan regions, where daily staple diet is rice.

Characterisation and utilisation of nano-reduced starch from underutilised cereals for delivery of folic acid through human GI tract

Ball milling offers green approach for size reduction of starch granules to nano scale size. In this research work, the starch from two underutilised cereal varieties viz. foxtail starch (FS) and sorghum starch (SS) were milled to achieve the desired nanometric range with mean particle diameter of 467.98 and 271.12 nm for nano foxtail (FSN) and nano sorghum starch (SSN), which were highly stable as revealed by zeta potential analysis. Functional attributes like solubility, swelling index, apparent amylose content, emulsifying and pasting properties were evaluated. Scanning electron microscopy (SEM) clearly revealed damaged starch granules produed by the process of milling. X-ray diffraction (XRD) displayed decrease in crystallinity upon milling to 16.08% (SSN) and 18.56% (FSN) and disappearance of some peaks. Attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) also revealed reduced crystallinity as confirmed by the decreased absorbance ratio of 1047/1022 cm−1 in nano starch particles. Rheological analysis displayed shear thinning behaviour of nano starch samples as evaluated using Herschel-bulkely model and Power law. The nano starch samples exhibited comparatively low thermal gelatinisation temperatures as compared to native counter particles. Moreover, the nano-encapsulated starch samples offered more resistance to in-vitro digestion and showed control release of folic acid at target sites.