Effects of Starch Molecular Structure and Physicochemical Properties on Eating Quality of Indica Rice with Similar Apparent Amylose and Protein Contents.

It is important to clarify the effects of starch fine structure and protein components on the eating quality of indica rice. In this study, seven indica rice varieties with similar apparent amylose content (AAC) and protein content (PC) but different sensory taste values were selected and compared systematically. It was found that except for AAC and PC, these varieties showed significant differences in starch molecular structure and protein components. Compared with rice varieties with a low sensory taste value, varieties with a higher sensory taste value showed significantly lower amylose and higher amylopectin short chains (degree of polymerization 6-12) content; the protein component showed that the varieties with good taste value had higher albumin and lower globulin and glutelin content (p < 0.05). Rice varieties with lower AC, globulin, and glutelin content, as well as a higher content of albumin and amylopectin short chains, resulted in a higher swelling factor, peak viscosity, breakdown value, and ratio of hardness to stickiness, in which condition cooked rice showed a higher sensory taste value. Moreover, this study indicated that rice varieties with a higher content of albumin and amylopectin short chains were conducive to the good appearance of cooked rice. This study lays the foundation for the taste evaluation of good-tasting indica rice.

The Effects of Genotype × Environment on Physicochemical and Sensory Properties and Differences of Volatile Organic Compounds of Three Rice Types (Oryza sativa L.).

Understanding the effects of genotype, environment and their interactions on rice quality is of great importance for rice breeding and cultivation. In this study, six rice varieties with two indica, two japonica and two indica-japonica types of rice were selected and planted at ten locations in Zhejiang Province to investigate the genotype (G) × environment (E) on physicochemical and sensory properties and the differences of volatile organic compounds (VOCs) among the three types of rice. Analysis of variances showed that apparent amylose content (AC), total protein content (PC), alkali spreading value (ASV), RVA profiles, and appearance (ACR), palatability (PCR), and sensory evaluation value (SEV) of cooked rice and texture of cooled cooked rice (TCCR) were mainly affected by genotypic variation, whereas the smell of cooked rice (SCR) was mainly affected by environment (p < 0.05). The G × E effect was significant for most parameters. The weather in the middle and late periods of filling had important effects on the formation of rice quality, especially on setback (SB) and pasting temperature (PT) (p < 0.01). They were negatively correlated with the texture of cooked rice (TCR) and SEV (p < 0.05). Peak viscosity (PV) and breakdown (BD) were positively related to the sensory evaluation parameters (p < 0.01) and could be used to predict cooked rice quality. A total of 59 VOCs were detected, and indica, japonica and indica-japonica had 9, 6 and 19 characteristic compounds, respectively. The principal component analysis showed that the physicochemical and sensory properties and VOCs of indica-japonica rice were more stable than those of indica and japonica rice at ten locations in Zhejiang Province. It is helpful for rice breeders to understand how the environment affects the physicochemical, sensory properties and VOCs of the three rice types, and it is also important for food enterprises to provide rice products with stable quality.

Effect of storage time on chemical compositions, physiological and cooking quality characteristics of different rice types.

BACKGROUND: Storage affects rice quality significantly. The aim of this study was to investigate the changes in the chemical composition and in the physiological and cooking quality characteristics of three rice types after 1 year storage at 25 °C. RESULTS: Two japonica, two indica, and two indica-japonica hybrid rice varieties were selected. After storage, the total starch content decreased. The amylose content of japonica, indica, and indica-japonica hybrid rice increased by 9.63%-11.65%, 2.99%-4.67%, and 8.07%-8.97%, respectively, and the fat content decreased by 60.00%-65.00%, 37.21%-46.51%, and 41.67%-42.42%, respectively. The abscisic acid (ABA) and raffinose content decreased after 1 year's storage; the former decreased gradually during the storage and the latter increased by 19.35%-45.45%, 7.02%-10.77%, and 16.13%-28.13%, respectively, after 4 months' storage and then decreased to the lowest level after 1 year's storage. The activity of antioxidant enzymes deceased, which resulted in the increases in fatty acid value and malondialdehyde (MDA). The changes in chemical composition after 1 year storage led to the deterioration of rice cooking quality, which was reflected in the decrease in viscosity and increases in gelatinization temperature and cooked rice hardness. CONCLUSION: After 1 year's storage, the rice chemical composition changed and physiological and cooking quality characteristics decreased. Compared with japonica and indica-japonica hybrid rice, indica rice was more stable during 1 year storage. This may be due to the higher content of ABA and raffinose in fresh rice. Our findings will provide information for the identification and breeding of storable rice cultivars. © 2022 Society of Chemical Industry.

Effects of storage on the starch fine structure and physicochemical properties of different rice variety types.

The genotype of rice variety is important factor that affect grain quality during storage. In this study, japonica, indica, and indica-japonica hybrid rice were selected to reveal the changes in amylase activities, starch fine structure, and physicochemical properties after one year of storage. Amylase activities decreased after storage and starch molecules were degraded, which, respectively, decreased and increased the content of the amylopectin long chains (DP 37+) and amylose. Changes in the starch fine structure resulted in lower swelling factors and a higher gelatinization temperature. Compared with japonica and indica-japonica hybrid rice, indica rice had a more stable starch fine structure and physicochemical properties after storage. The information obtained from this study provides a better understanding of the changes that occur in starch at the molecular level during storage and will provide insight into the breeding of storable rice varieties.

Development of Certified Reference Materials for the Determination of Apparent Amylose Content in Rice.

Apparent amylose content (AAC) is one of the most important parameters in rice quality evaluation. In this study, four rice reference materials used to test rice AAC were developed. The AAC of rice reference materials were measured by a spectrophotometric method with a defatting procedure, calibrated from potato amylose and waxy rice amylopectin at the absorption wavelengths of 620 and 720 nm. Homogeneity test (n = 20) was judged by F-test based on the mean squares of among and within bottles, and short- and long-term stability monitoring was performed by T-test to check if there was significant degradation at the delivery temperature of under 40 °C (14 days) and at 0-4 °C storage condition (18 months), respectively. After joint evaluation by ten laboratories, Dixion and Cochran statistical analyses were presented. The expanded uncertainties were calculated based on the uncertainty of homogeneity, short- and long-term stability, and inter-laboratory validation containing factor k = 2. It found that the four reference materials were homogenous and stable, and had the AAC (g/100 g, k = 2) of 2.96 ± 1.01, 10.68 ± 0.66, 17.18 ± 1.04, and 16.09 ± 1.29, respectively, at 620 nm, and 1.46 ± 0.49, 10.44 ± 0.56, 16.82 ± 0.75, and 24.33 ± 0.52, respectively, at 720 nm. It was indicated that 720 nm was more suitable for the determination of rice AAC with lower uncertainties. The determinations of the AAC of 11 rice varieties were carried out by two methods, the method without defatting and with calibration from the four rice reference materials and the method with a defatting procedure and calibrating from potato amylose and waxy rice amylopectin. It confirmed that the undefatted rice reference materials could achieve satisfactory results to test the rice samples with the AAC ranging from 1 to 25 g/100 g. It would greatly reduce the time cost and improve testing efficiency and applicability, and provide technical support for the high-quality development of the rice industry.

Melatonin alleviates copper stress to promote rice seed germination and seedling growth via crosstalk among various defensive response pathways.

Copper (Cu) contamination dramatically affects crop growth and thus threatens crop production; while applications of melatonin (MT) serve as an effective way to tolerate Cu stress for plant development, the underlying mechanism remains largely unknown in rice. Here, we found that Cu toxicity remarkably decreased germination rates and seedling growth compared to the untreated control (CK), while seed priming with a solution of 100 µM MT significantly alleviated the adverse effects on Cu-stressed seeds. In addition, the MT treatment decreased the accumulation of Cu in seedlings at 7 days after imbibition (DAI), possibly through enhanced Cu sequestration, and improved reserve mobilization through the promoted activity of α-amylase and protease in seeds under Cu stress. Interestingly, gibberellin (GA) synthesis was restored to or even exceeded the CK levels in the MT presoaking treatment, while the abscisic acid (ABA) content decreased compared to those of the Cu-stressed seeds, suggesting crosstalk between MT and other phytohormones, e.g., GA and ABA. More importantly, MT pretreatment also significantly promoted the growth of postgermination seedlings. This was largely ascribed to the MT-ameliorated antioxidant system, which consequently reduced the accumulation of Cu stress-induced oxidative products, e.g., hydrogen peroxide (H2O2), malondialdehyde (MDA), and superoxide (O2·_). Collectively, these results demonstrate that seed priming with MT could greatly mitigate the adverse effects of Cu stress on seed germination and subsequent postgermination growth through crosstalk among various defensive response pathways. This study provides vital guidance for applications of MT in agronomic production.

Phenolic acids and phytosterols in rice grains and wheat flours consumed in five regions of China.

Phenolic acids and phytosterols, the main functional compounds in cereals, could promote wellbeing and reduce the risks of diet-related diseases. This study aimed to demonstrate phenolic acid and phytosterol profiles in rice grains and wheat flours, and estimate their intakes in five geographical regions and among different age groups. Phenolic acids and phytosterols mainly existed in bound form, and the whole rice grain had high amount of 161.39 to 368.74 µg/g and 37.50 to 93.31 mg/ 100 g, respectively. In total, nine phenolic acids and six phytosterols were detected with ferulic and p-coumaric acid, and ß-sitosterol the most abundant. The dietary intakes of phenolic acids and phytosterols were calculated combined with the dietary foods intake data of Chinese people. The intakes of total phenolic acids and phytosterols from rice grains and wheat flours varied across different regions with Beijing the highest among the five regions. At the age of 2 to 70 years, the average intakes of phenolic acids and phytosterols from rice and wheat flours were 7.74 to 17.52 and 58.02 to 135.61 mg/sp/day, respectively. If 3-ounce of polished rice was replaced by black rice grain, the predicted intakes of total phenolic acids and phytosterols from rice grains and wheat flours would increase by at least 196% and 68%, respectively, especially for free phenolic acids and phytosterols. PRACTICAL APPLICATION: This study would help the consumers know how much phenolic acids and phytosterols they would get from 3 ounces of black rice in a reasonable intake of staple food but shift away other kinds of foods. It could also provide inspirations for food industries to explore the functional cereal foods that are rich in phenolic acids and phytosterols for different regions and different age groups.

Irrigation with secondary municipal-treated wastewater: Potential effects, accumulation of typical antibiotics and grain quality responses in rice (Oryza sativa L.).

Using secondary treated wastewater to irrigate paddies presents an exposure pathway for antibiotics to enter the terrestrial food chain. To date, there has been no information on the biochemical reactions and antibiotic uptake in rice plants irrigated with secondary treated wastewater. The present study investigated antibiotic uptake and concentration-response trends in rice tissues and evaluated the effects of typical antibiotics (tetracycline, roxithromycin, ofloxacin, and sulfamethoxazole) on rice growth, grain yield and quality, and rice physiobiochemical characters via irrigation using treated wastewater augmented with varying concentrations (0-500 µg/L) in paddies. The results showed that the antibiotic accumulation in rice plants irrigated with treated wastewater was limited, and the studied antibiotics were not detected in rice grains (edible parts). The ability of rice to withstand certain antibiotics and grow in a healthy manner is attributed to the capacity to maintain reasonably normal photosynthesis activity and to elevate antioxidative defenses. The highest antibiotic concentration (500 µg/L) did not reduce the processing quality of the rice grain, but it enhanced the cooking and eating quality. From the obtained results, it can be concluded that secondary treated wastewater for paddy irrigation is an alternative water resource securing protection from the environment and rice grain quality.

Phenolic acid profiles of common food and estimated natural intake with different structures and forms in five regions of China.

Phenolic acids have been reported to have many biological activities, but daily intake information is scarce. In this study, the phenolic acid contents of 116 commonly consumed food in five regions of China (Beijing, Hangzhou, Wuhan, Chongqing and Guangzhou) were analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS) and dietary intakes estimated. Tea had the highest total phenolic acids (TPA) content in all regions investigated. Phenolic acids were in esterified and bound forms, and hydroxycinnamic acids accounted for more than half of TPA content, except in tea and legumes. Average TPA intake was 193.50 mg/ day at the national level but ranged from 157.09 to 263.01 mg/ day among the regions. Rice, tea, and fruits were the main contributors to dietary intakes of TPA. Also, TPA intake in the period 2009-2013 increased 31.65 mg/ day compared with 2002, largely due to increased intakes of fruits, vegetables, and legumes.

Phytosterol Profiles of Common Foods and Estimated Natural Intake of Different Structures and Forms in China.

Phytosterols are well-known for their cholesterol-lowering effects, and the structures and forms of phytosterols affect their bioactivity. We aimed to illustrate the phytosterol profiles in common foods and estimate their natural intake in five geographical regions and among different age groups in China. In total, 12 phytosterols in free and esterified forms of 119 foods from five regions across China were examined using gas chromatography-mass spectrometry. Then, the dietary intake of phytosterols was calculated combined with the dietary foods intake data of Chinese people. The total phytosterol content was highest in vegetable oils (150.4-1230.9 mg/100 g), followed by legumes (129.6-275.6 mg/100 g), nuts (18.9-255.2 mg/100 g), and cereals (11.9-93.8 mg/100 g). Vegetables and fruits contained lower contents of total phytosterols. Phytosterols were mainly esterified in most common foods except in nuts. The predominant phytosterols were ß-sitosterol, campesterol, and stigmasterol, all of which belonged to plant sterols and 4-desmethylsterols. Total phytosterol intake varied across different regions, ranging between 257.7 and 473.7 mg/standard-person (sp)/day, with the highest intake in Beijing, followed by Hangzhou, Wuhan, Chongqing, and Guangzhou. However, phytosterol proportion was similar across regions, with ß-sitosterol accounting for 46.5-50.3% of the natural intake. Phytosterol intake was mainly constituted by plant sterols and 4-desmethylsterols in esterified form (61.9-74.6%). At the age of 2-70 years, phytosterol intake ranged from 154.3 mg/day to 348.0 mg/day in the national scale.

Effects of different extrusion temperatures on extrusion behavior, phenolic acids, antioxidant activity, anthocyanins and phytosterols of black rice.

Different extrusion temperatures (90, 100, 110, and 120 °C) were used to investigate changes in the expansion ratios, die pressures, phytochemical contents and antioxidant activities of extrusion products of black rice. The results showed that the die pressure significantly decreased with the increasing extrusion temperature, and the expansion ratio reached a peak value at 100 °C. The soluble-free and total phenolic acid contents gradually increased, whereas portions of soluble-free and soluble-conjugated phenolic acids transformed into insoluble-bound phenolic acids. The soluble-free (52.45) and insoluble-bound (73.59 mg GAE/100 g DF) total phenolic contents (TPC) reached peak values at 110 °C. The soluble-conjugated TPC values remained similar. Antioxidant activity occurred at higher levels in the range from 100 °C to 120 °C. The anthocyanin content decreased after extrusion possibly because some anthocyanin remained in the residue after extraction and could not be completely extracted. The content of free sterols increased from 90 °C to 110 °C and decreased at 120 °C. However, the content of bound sterols showed an opposite trend and reached a minimum value at 110 °C.

Bound phenolic compounds and antioxidant properties of whole grain and bran of white, red and black rice.

Total phenolic content (TPC), individual phenolic acid and antioxidant capacity of whole grain and bran fraction 18 rices with different bran color were investigated. The levels of TPC in bound fractions were significantly higher than those in the free fractions either in the whole grains or brans. The main bound phenolic acids in white rice samples were ferulic acid, p-coumaric acid, and isoferulic acid, and in pigmented rice samples were ferulic acid, p-coumaric acid, and vanillic acid. The protocatechuic acid and 2,5-dihydroxybenzoic acid were not detected in white samples. The content of gallic acid, protocatechuic acid, 2,5-dihydroxybenzoic acid, ferulic acid, sinapic acid had significantly positive correlations with TPC and antioxidant capacity. This study found much wider diversity in the phenolics and antioxidant capacity in the whole grain and brans of rice, and will provide new opportunities to further improvement of rice with enhanced levels of the phytochemicals.

Phenolic acids, anthocyanins, proanthocyanidins, antioxidant activity, minerals and their correlations in non-pigmented, red, and black rice.

Soluble-free, soluble-conjugated, insoluble-bound phenolics and antioxidant activity, flavonoid (TFC), proanthocyanidins (TPAC), anthocyanins and minerals of fifteen whole rice grains with different colors were investigated. Soluble-free protocatechuic and vanillic acids were only quantified in black rice, which had the most quantities. Non-pigmented rice had no detectable conjugated protocatechuic and 2,5-dihydroxybenzoic acids both of which were found in black and red rice, respectively. The main bound phenolic acids were ferulic and p-coumaric, as well as 2,5-dihydroxybenzoic in red rice and protocatechuic and vanillic acids in black rice. Soluble-conjugated phenolics, TFC, and anthocyanins were negatively correlated with L∗, b∗, C and H° values. TPAC was positively correlated with a∗ (P<0.01). Protocatechuic, vanillic, syringic and ferulic acids were associated with TPC and antioxidant activity in the soluble-conjugated fraction while protocatechuic and ferulic acid were correlated with those in the insoluble-bound fraction. Principal component analysis divided samples into non-pigmented, red and black rice groups.

Determination of soluble sugar profile in rice.

Soluble sugars in rice are the main components affecting sweetness taste of rice. In this paper, an accurate, precise and rapid method for simultaneous determination of multi soluble sugars in rice by using ion chromatography equipped with pulsed amperometric detector was presented. Pretreatment and parameters of ion chromatography and pulsed amperometric detector were optimized. Regression coefficients (R) of 0.9998, 1.0000, 0.9979, 0.9998 and 0.9998 were obtained for glucose, fructose, sucrose, raffinose and maltose, respectively. The recovery ranges of five sugars were 92.9-112.0% for milled rice matrix. Repeatability and reproducibility of the method were 0.8-9.7% and 1.9-7.6%, respectively. Method LODs of 3.1-34.6µgg-1 were obtained for soluble sugars in milled rice matrix.

Effect of parboiling on phytochemical content, antioxidant activity and physicochemical properties of germinated red rice.

In order to improve functional properties and palatability of germinated red rice, this study investigated differences in phytochemicals and physicochemical properties of germinated red rice at 2, 5, 10, 15min of parboiling. Total free phenolic content and antioxidant activity of germinated red rice parboiled for 5 and 15min was higher than that of germinated red rice. Free p-coumaric acid increased from 0.20 to 0.67mg/100g with parboiling time increasing from 5 to 15min. Bound vanillic (0.17-0.27mg/100g) and p-coumaric acid (6.56-8.59mg/100g) had higher levels at 0, 2, or 5min. During 15min of parboiling, color difference (ΔE) increased from 0.58 to 9.09, heat enthalpy (ΔH) decreased from 4.69 to 1.94J/g, and internal structure of rice was destroyed. Overall, parboiling time of less than 5min was suitable to improve the quality of germinated red rice.

Mapping of Quantitative Trait Loci for Contents of Macro- and Microelements in Milled Rice (Oryza sativa L.).

Macro- and microelement contents are important traits for nutritional quality in rice. In this study, quantitative trait loci (QTLs) for the contents of seven mineral elements in milled rice were detected using recombinant inbred lines (RILs) of the indica rice cross Zhenshan 97/Milyang 46, followed by the validation and fine mapping of a QTL region on the short arm of chromosome 6. A total of 20 QTLs distributed on chromosomes 1, 3, 5, 6, 10, and 11 were detected in the RIL population. Co-localizations of QTLs for multiple traits were observed, of which the qP3/qMg3/qZn3 region was shown to have the largest effects for the contents of phosphorus, magnesium, and zinc, and the qK6.1/qCa6/qZn6/qMn6/qCu6 region was found to be responsible for five of the seven traits. Using near isogenic lines having sequential segregating region, the target QTL on chromosome 6 was delimitated to a 29.9 kb region flanked by RM19410 and Si2944. This QTL showed major effects for all seven traits, with the enhancing alleles derived from the male parent Milyang 46.

Polyphenols in whole rice grain: genetic diversity and health benefits.

Polyphenols, such as phenolic acid, anthocyanin and proanthocyanidins, have both nutraceutical properties and functional significance for human health. Identification of polyphenolic compounds and investigation of their genetic basis among diverse rice genotypes provides the basis for the improvement of the nutraceutical properties of whole rice grain. This review focuses on current information on the identification, genetic diversity, formation and distribution patterns of the phenolic acid, anthocyanin, and proanthocyanidins in whole rice grain. The genetic analysis of polyphenol content and antioxidant capacity allows the identification of several candidate genes or quantitative trait loci (QTL) responsible for polyphenol variation, which may be useful in improvement of these phytochemicals by breeding. Future challenges such as how to mitigate the effects of climate change while improving nutraceutical properties in whole grain, and how to use new technology to develop new rice high in nutraceutical properties are also presented.

Phenolic compounds and antioxidant properties of breeding lines between the white and black rice.

Advanced breeding lines made from the cross between the black and white rice as parents were collected to evaluate phenolic levels and antioxidant properties. No free phenolic acid was found in the soluble fraction, while p-coumaric acid, ferulic acid, isoferulic acid and vanillic acid were identified in insoluble bound fractions. Of noteworthy, is isoferulic acid which has rarely been reported to occur in cereal grains. Phenolic dehydrodimers were only observed in the insoluble bound fractions, which mainly consisted of 8-5'-coupled diferulic acids and 5-5'-coupled diferulic acids. Cyanidin 3-glucoside, peonidin 3-glucoside and cyanidin occurred in black and some light-purple rice samples. The breeding line YF53 has the highest total phenolic content (23.3mg ferulic acid equiv./g), total anthocyanin content (2.07 mg cyanidin-3-glu equiv./g), and antioxidant activities. The results indicate that it is possible to develop advanced breeding lines for improvement of the phenolic profiles and antioxidant capacity with high yield.

Analysis of genotype × environment interactions for polyphenols and antioxidant capacity of rice by association mapping.

Uncovering the genetic basis of polyphenol content and antioxidant activity traits in rice accessions is important to improve the nutritional quality of whole grain rice and to ameliorate the increasing nutrition problem of the rice-eating population. In this study, 20 diverse rice accessions were planted in Hainan province, China, for 2 years to investigate the effects of genotype, environment, and their interactions on total phenolic (TPC), flavonoid (TFC), proanthocyanidins content (TPAC), ABTS, and DPPH radical scavenging activity by association mapping. Analyses of variance (ANOVA) showed that TPC, TFC, TPAC, ABTS, and DPPH were mainly affected by genetic variance, accounting for >94% of the total variance. The interaction between genotype × environment (G × E) was also highly significant (P < 0.001). Red-pericarp rice accumulates proanthocyanidins, which had significantly higher TPC, TFC, ABTS, and DPPH than white-pericarp rice. The correlation coefficient among these parameters were highly significant (r > 0.96; P < 0.001). Twenty-three putative unique loci were identified by association mapping. Five loci were close to previously identified genes or quantitative trait loci (QTLs). Among them, qPAC7-3 identified for TPAC in 2011 was near to the brown pericarp and seed coat (Rc) gene, and the locus at the qPC4/qFC4/qPAC4/qACA4/qACD4 cluster on chromosome 4 detected in two environments was near to a transcriptional activator A (Ra) gene. Some loci were identified in only one environment, indicating that these QTLs were sensitive to environment. This study provides a primary SNP-resource for further identification of genes responsible for polyhenol contents and antioxidant activity in rice whole grains.

Phenolic acids, anthocyanins, and antioxidant capacity in rice (Oryza sativa L.) grains at four stages of development after flowering.

This study investigated differences in total phenolic content (TPC), antioxidant capacity, and phenolic acids in free, conjugated and bound fractions of white (unpolished), red and black rice at 1-, 2-, and 3-weeks of grain development after flowering and at maturity. Unlike the TPC (mg/100g) of white rice (14.6-33.4) and red rice (66.8-422.2) which was significantly higher at 1-week than at later stages, the TPC of black rice (56.5-82.0) was highest at maturity. The antioxidant capacity measured by DPPH radical scavenging and ORAC methods generally followed a similar trend as TPC. Only black rice had detectable anthocyanins (26.5-174.7mg/100g). Cyanidin-3-glucoside (C3G) and peonidin-3-glucoside (P3G) were the main anthocyanins in black rice showing significantly higher levels at 2- and 3-weeks than at 1-week development and at maturity. At all stages, the phenolic acids existed mainly in the bound form as detected by HPLC and confirmed by LC-MS/MS. Black rice (20.1-31.7mg/100g) had higher total bound phenolic acids than white rice and red rice (7.0-11.8mg/100g). Protocatechuic acid was detected in red rice and black rice with relatively high levels at 1-week development (1.41mg/100g) and at maturity (4.48mg/100g), respectively. Vanillic acid (2.4-5.4mg/100g) was detected only in black rice where it peaked at maturity. p-Coumaric acid (<3.5mg/100g) did not differ significantly at most stages with somewhat high levels at 1-week for red and black rice. Ferulic acid (4.0-17.9mg/100g), the most abundant bound phenolic acid, had an inconsistent trend with higher levels being observed in black rice where it peaked at maturity. Isoferulic acid levels (0.8-1.6mg/100g) were generally low with slightly elevated values being observed at maturity. Overall black rice had higher total bound phenolic acids than white and red rice while white rice at all stages of development after flowering.