Effects of cooking on anthocyanin concentration and bioactive antioxidant capacity in glutinous and non-glutinous purple rice

Purple rice is a source of bioactive antioxidants for rice consumers. Loss of the major antioxidant compounds after a range of cooking processes was evaluated by measuring the change in anthocyanin concentration (ATC) and antioxidant capacity (DPPH activity) of four non-glutinous and four glutinous genotypes. However, soaking in water prior to cooking generally decreased ATC and DPPH activity more in non-glutinous than in glutinous genotypes. Wet cooking (WC) and soaking before wet cooking (S-WC) led to almost all the ATC and DPPH activity being lost with only slight variation between genotypes. In the glutinous genotype PES, which had the highest raw rice ATC, the highest ATC remained when cooked by the WC method. By contrast, almost no ATC remained after WC and S-WC in the low ATC genotypes such as KDK. Overall, the loss of ATC on cooking was greater in non-glutinous than glutinous genotypes for both WC and S-WC, but the reverse occurred for DPPH activity. Wet cooking using electric rice cooker retained higher ATC than the pressure cooking. Thus, for genotypes with high ATC and antioxidant capacity, the selection of cooking method is critical for retaining and stabilizing rice quality

Simultaneous Quantification of Anthocyanins and Phenolic Acids in Pigmented Rice (Oryza sativa) using UPLC-PDA/ESI-Q-TOF

Anthocyanins and phenolic acids are the major antioxidants in purple rice. The method conditions were specified and not coved for both anthocyanins and phenolic acids. The objective of this study was to adopt the UPLC coupled with ESI-MS method for determination of the major anthocyanins and phenolic acids under the same condition in purple, red and white rice varieties. A UPLC-PDA/ESI-Q-TOF method was optimized with a high linearity for all analyzed compounds with regression coefficients greater than 0.99. Repeatability was good with the relative standard deviation values generally less than 5.5%. The limit of detection and quantification ranged from 1.9-36.6 and 5.0-123.1 mu g kg(-1), respectively. Spike recoveries were between 81-116%. Mass spectroscopy was used to confirm identity in the positive ion mode for all analyzed compounds Cyanidin-3-glucoside and ferulic acid were the most abundant anthocyanins and phenolic acids, respectively. Bound ferulic acid was higher in purple rice than in red and white rice flours. This developed procedure can be used to facilitate the rapid screening of rice seed banks for anthocyanins and phenolic acids of interest for rice pre-breeding

Anthocyanin and phenolic acid profiles in purple, red and non-pigmented rice during germination

There is a growing interest in using germinated rice in health products based on their antioxidant properties but studies exploring differences in pigmented and non-pigmented rice types are limited. Therefore, anthocyanin and phenolic acid contents and composition were quantified using UPLC over 6 days of germination in three pigmented (two purple and one red) and one non-pigmented rice genotypes. Most of the anthocyanin content in purple rice, mainly cyanidin-3-glucoside and peonidin-3-glucoside, was lost during the imbibition and radicle emergence phase of germination. By contrast, there were only small changes in free and bound phenolic acid fractions over the 6 days of germination in all genotypes. Vanillic and ferulic acids comprised the main components of the free and bound pools, respectively. Vanillic acid contents, but not ferulic acid, were considerably greater in purple rice than in red and non-pigmented rice. Germination rapidly decreased the anthocyanin content in purple rice, but only had a minor effect on the free and bound phenolic acids in purple, red and non-pigmented rice. The increasing content of bound p-coumaric, ferulic and vanillic acids in germinated purple rice may provide an opportunity to develop rice products as functional foods

Applying nitrogen fertilizer increased anthocyanin in vegetative shoots but not in grain of purple rice genotypes

BACKGROUND Anthocyanin is a major antioxidant compound in purple rice, with properties that can protect against oxidative damage in some human diseases. This study was undertaken to determine if nitrogen (N) fertilizer can enhance anthocyanin and antioxidant levels in four purple Thai rice genotypes. RESULTS The anthocyanin concentration and antioxidant capacity were increased in the shoots of N120 plants compared with plants without N. The leaves had higher anthocyanin concentration and antioxidant capacity than the stem+leaf sheath. Maximum shoot anthocyanin concentrations occurred at tillering and then declined by 87–94% at maturity. Antioxidant capacity was high at tillering and panicle initiation and declined by 26% in leaves and by 98% in the stem+leaf sheath at maturity. Unlike in the vegetative shoot, grain anthocyanin was not affected by the addition of N fertilizer. The response of grain antioxidant capacity to N fertilizer was affected by genotype, increasing in KPY by 45% but decreasing in K19959 by 30% in N120 plants. CONCLUSION Applying N fertilizer could be a promising way to improve the antioxidative properties in vegetative parts for use in rice‐grass juice, cosmetics and other products, especially the young leaves, which contained high values of anthocyanin as well as antioxidant capacity. However, further field studies should be undertaken to optimize N utilization for anthocyanin and antioxidant capacity in purple rice genotypes

Responses of grain yield and nutrient content to combined zinc and nitrogen fertilizer in upland and wetland rice varieties grown in waterlogged and well-drained condition

This study explored the response in grain yield and quality of upland and wetland rice varieties to a combination of zinc (Zn) and nitrogen (N) fertilizers under two water management regimes. A factorial arrangement based on a randomized complete block design composed of three factors was carried out with three independent replications. Upland and wetland rice varieties were grown with three fertilizer treatments; the optimum N rate (86 kg N ha−1) without Zn application, the optimum N rate with Zn (50 kg ZnSO4 ha−1), and the high N rate (172 kg N ha−1) with Zn under waterlogged and well-drained conditions. Grain yield was 27% lower in the well-drained than in the waterlogged condition in wetland rice, while there was no effect in upland rice. Application of optimum N with Zn application produced the highest grain yield in upland rice, while yield was the highest in wetland rice in high N with Zn application. Upland rice grown in the well-drained condition with the optimum and high N with Zn treatments enhanced Zn concentration by 45% and 29% higher than the treatment without Zn, respectively, while it had no difference among three treatments in the waterlogged condition. Wetland rice variety grown under the well-drained condition in optimum and high N rate with Zn treatments were equally effective in improving grain Zn concentration at the average of 88% compared to the control. While rice grown under the waterlogged condition in the high N with Zn treatment had improved 92% the concentration. The optimum N rate with Zn application increased grain yield in upland rice, while the higher N input is required for wetland rice. Grain Zn concentrations of upland and wetland rice varieties were enhanced by applying Zn fertilizer; however, the increased level was depended on N application rate in the individual water condition

Stability of Anthocyanin content and antioxidant capacity among local Thai purple rice genotypes in different storage conditions

This study determined whether storage conditions over six months affected grain anthocyanin content and antioxidant capacity of four purple rice genotypes with different initial anthocyanin content. Two forms of grain, paddy and brown rice were stored at three temperatures -25 °C, room temperature (25-30 °C) and 60 °C with three replications. In the two high-anthocyanin genotypes, the anthocyanin continued to decrease until the last month of storage, while the low-anthocyanin genotypes were not affected by storage time. Storage at 60 °C decreased the average anthocyanin content by 42%, compared to the 30% loss for grain stored at either -25 °C or room temperature. Brown rice retained more of its anthocyanin than paddy rice in the high anthocyanin genotypes. Antioxidant capacity substantially declined during storage in all genotypes and the capacity was higher in brown than paddy rice. There was a significant correlation between anthocyanin content and antioxidant capacity in the two high-anthocyanin genotypes, but not in the low-anthocyanin genotypes, indicating the possibility of different anti-oxidative key compounds between the low- and high-anthocyanin genotypes. These results suggest that the anthocyanin content and antioxidant capacity in purple rice genotypes would be most stable when stored at low temperature as brown rice

Boron requirement for vegetative growth of Sacha inchi (Plukentia volubilis L.)

Sachi inchi is a useful traditional plant in South America that has recently gained notoriety as a nutritional food crop and hence is being cultivated outside its native range. In Thailand, the crop is being grown on soils where boron (B) may be limiting to growth. To determine the response of early vegetative growth of sacha inchi to B supply, to identify B deficiency symptoms, and to define leaf B concentrations for optimum growth. The two experiments were conducted in sand-culture pot arranged in a randomized complete block design with three independent replications. Plants were grown in the preliminary experiment consisted of complete nutrient solution and complete nutrient solution without B. The main experiment was continued by growing plants in the five series of B rate (0, 2.5, 5.0, 7.5 and 10.0 µM B). Plant growth parameters were recorded and B concentration in different plant parts were analyzed. B deficiency strongly inhibited root and shoot development causing stunting and organ malformation. In a sand-culture experiment, maximum growth was obtained with 7.5 µM B and 10 µM B reduced growth. Leaf B concentration of 27–29 mg kg−1 was associated with 90% of maximum vegetative yield. Symptoms of B deficiency and the foliar B concentrations are useful for extension workers and producers looking to improve the productivity of sacha inchi on nutrient poor soils