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 changes 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 more ATC and antioxidant capacity in non-glutinous than in glutinous genotypes. Wet cooking （WC） and soaking before wet cooking （S-WC） led to lose almost all the ATC and antioxidant capacity with only slight variation between genotypes. In the glutinous genotype Pieisu, which had the highest raw rice ATC, ATC remained the highest when cooked by the WC method. By contrast, almost no ATC remained after WC and S-WC in the low ATC genotypes such as Kum Doi Saket. Overall, the loss of ATC was greater in non-glutinous than in glutinous genotypes for both WC and S-WC methods, but the reverse occurred for antioxidant capacity. WC 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.

Improve Anthocyanin and Zinc Concentration in Purple Rice by Nitrogen and Zinc Fertilizer Application

Zinc(Zn)is an essential micronutrient for plant growth and development,and anthocyanin is a secondary metabolite compound generally produced under stress conditions;both have benefits to human health.Rice is a staple food crop for most of the world’s population,and purple rice is well known as a natural source of Zn and anthocyanins,but their stability depends upon many factors.This review focuses on the opportunity to increase Zn and anthocyanin compounds in purple rice grains via Zn and nitrogen(N)management during cultivation.Variation in grain Zn concentration and anthocyanin compounds is found among purple rice varieties,thus presenting a challenge for breeding programs aiming at high grain Zn and anthocyanin contents.Genetic engineering has successfully achieved a high-efficiency vector system comprising two regulatory genes and six structural anthocyanin-related genes driven by endosperm-specific promoters to engineer purple endosperm rice that can provide new high-anthocyanin varieties.Grain Zn and anthocyanin concentrations in rice can also be affected by environmental factors during cultivation,e.g.,light,temperature,soil salinity and nutrient(fertilizer)management.Applying N and Zn fertilizer is found to influence the physiological mechanisms of Zn absorption,uptake,transport and remobilization to promote grain Zn accumulation in rice,while N application can improve anthocyanin synthesis by promoting its biosynthesis pathway via the use of phenylalanine as a precursor.In summary,there is an opportunity to improve both grain Zn and anthocyanin in purple rice by appropriate management of Zn and N fertilizers during cultivation for specific varieties.

The impact of simulated gastrointestinal digestion on the bioaccessibility and antioxidant activity of purple rice phenolic compounds

Polyphenol-rich purple rice has been shown to exhibit a wide range of health properties including antioxidant activity.This study aimed to determine the impact that gastrointestinal digestion of purple rice had on its phenolic bioaccessibility and antioxidant activity.Our results demonstrated a significant difference(p<0.01)in bioaccessible phenolic content level and antioxidant activity between simulated gastric and intestinal digestion.However,mass spectrometry and ultra-high-performance liquid chromatography(UHPLC)coupled with online ABTS•+scavenging activity demonstrated a significant loss in the number of polyphenols that were bioaccessible after digestion.Interestingly,substantial free radical scavenging activity was retained after digestion due to the bioaccessibility of bioactive compounds such as tryptophan and protocatechuic acid.Hence,purple rice may be considered as a source of bioaccessible phenolic and antioxidant compounds.

Effect of nitrogen fertilizer on the uptake and utilization of potassium by various rice varieties in purple soil

Nitrogen and potassium are important nutrientelements for rice.Besides supplied by the or- ganic manure,potassium nutrition of ricecomes dominantly from purple soils in Sichuanbasin.Potassium exists abundantly in mineralforms in the purple soils.Availability of soilpotassium for crop depends on the potassiumforms,the uptake ability of crops,and fertiliz-er practices.A pot culture experiment wasconducted to study the kinetics of potassiumuptake in the purple soil(total N 22.64g·kg,total K 24.36g·kg,available N 102.6mg·kg,available K 140.6mg·kg,acidsoluble K 936.0mg·kg,and pH 6.8).Ma-terials used were three Fhybrid rices,Eryou