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Phenolic content and antioxidant activity of pearled wheat and roller-milled fractions

ABSTRACT Wheat contains phenolic compounds concentrated mainly in bran tissues. This study examined the distribution of phenolics and antioxidant activities in wheat fractions derived from pearling and roller milling. Debranning (pearling) of wheat before milling is becoming increasingly accepted by the milling industry as a means of improving wheat rollermilling performance, making it of interest to determine the concentration of ferulic acid at various degrees of pearling. Eight cultivar samples were used, including five genotypes representing four commercial Canadian wheat classes with different intrinsic qualities. Wheat was pearled incrementally to obtain five fractions, each representing an amount of product equivalent to 5% of initial sample weight. Wheat was also roller milled without debranning. Total phenolic content of fractions was determined using the modified Folin-Ciocalteau method for all pearling fractions, and for bran, shorts, bran flour, and first middlings flour from roller milling. A...

Measurement of anthocyanins and other phytochemicals in purple wheat

The major anthocyanin composition of normal purple wheat and heat stressed purple wheat were measured using HPLC, LC-MS/MS and the pH differential method. The lignan secoisolariciresinol diglucoside (SDG) and melatonin content were also measured. Total anthocyanin profile of normal purple wheat (491.3mg/kg) was significantly (P<0.05) lower than that of the heat stressed purple wheat (522.7mg/kg). Thirteen major anthocyanins were isolated and cyanidin 3-glucoside was the predominant anthocyanin in purple wheat. Using the pH differential method, the total anthocyanin content of normal (500.6mg/kg) and heat stressed (526.0mg/kg) purple wheat were similar to those observed using HPLC. The SDG content of normal and heat stressed purple wheat were 770 and 520μg/kg, while melatonin content was 4 and 2μg/kg, respectively. The presence of SDG and melatonin in addition to anthocyanins may contribute to the health benefits associated with consumption of coloured cereal grains.

Starch properties as affected by sorghum grain chemistry

To determine the relationship between sorghum grain polyphenol content, grain structure, and starch properties, starch was isolated from 10 sorghum varieties using an alkali steep and wet-milling procedure. SV2, a tannin-free variety with white pericarp, gave a white starch. Varieties having red or white pericarp and higher polyphenol levels gave pink starches. Hunter colour values (L, a, b) of starches were not correlated with grain polyphenol content. Grain appearance in terms of pericarp colour, or presence or absence of pigmented testa, did not relate to the intense pink colouration of sorghum starches. Starch amylose content was significantly negatively correlated (r  = −0.88, p < 0.001) to grain floury endosperm texture. Sorghum starches had higher peak viscosity (PV) in pasting than commercial maize starch. The time taken to reach peak viscosity from the initial viscosity rise was less for sorghum starches than maize starch. However, sorghum starches had a higher rate of shear thinning (Rst) than maize starch. There was a significant positive correlation between grain polyphenol content and starch PV (r  = 0.75, p < 0.05). Starch gel hardness was negatively correlated to pasting properties of Rst and paste breakdown (r  = −0.78 and −0.77 respectively) at p < 0.01. Peak gelatinisation temperature (Tp) occurred over a narrow range from 66 to 69 °C. Tp was negatively correlated to the floury endosperm portion of the grain (r  = −0.77) at p < 0.01. It is concluded that sorghum grain polyphenol content and grain characteristics influence its starch properties. © 2000 Society of Chemical Industry

Phenolic compounds and kernel characteristics of Zimbabwean sorghums

Sixteen sorghum varieties widely cultivated in Zimbabwe were examined for levels of phenolic compounds and kernel characteristics, to help identify those with desirable properties and develop suitable processing methods. Assays for polyphenols included the chlorox test, the vanillin- HCl, the ferric ammonium citrate and the butanol-HCl methods. Free phenolic acids were analysed using reverse-phase high performance liquid chromatography. Varieties DC-75, Mutode and Chirmaugute had the highest levels of condensed tannins. The polyphenols in Chibonda were mostly unextractable in methanol. No significant levels of polyphenols were found in 13 varieties. Phenolic acid content was related to pericarp colour. Endosperm texture and pericarp thickness were evaluated using video image analysis. Katandanzara and SV1 had relatively corneous endosperms ( 0.060 mm). Endosperm texture was not correlated with phenolic compounds. A positive correlation, however, was observed between pericarp thickness and polyphenol content (r> 0.64). Zimbabwean sorghums lack ideal agronomic and processing physico-chemical characteristics defined in terms of high polyphenols, plus hard endosperm and thin pericarp. Research is required to develop effective methods to process the available polyphenol-rich sorghums. # 1999 Society of Chemical Industry

Comparison of antioxidant capacity and phenolic compounds of berries, chokecherry and seabuckthorn

Antioxidant capacity and phenolic compounds (phenolic acids and anthocyanins) of four berry fruits (strawberry, Saskatoon berry, raspberry and wild blueberry), chokecherry and seabuckthorn were compared in the present study. Total phenolic content and total anthocyanin content ranged from 22.83 to 131.88 g/kg and 3.51 to 13.13 g/kg, respectively. 2,2-Diphenyl-1-picryhydrazyl free radical scavenging activity ranged from 29.97 to 78.86%. Chokecherry had the highest antioxidant capacity when compared with berry fruits and seabuckthorn. The highest caffeic acid, gallic acid and trans-cinnamic acid levels were found in chokecherry (6455 mg/kg), raspberry (1129 mg/kg) and strawberry (566 mg/kg), respectively. Caffeic acid was also the major phenolic acid in Saskatoon berry (2088 mg/kg) and wild blueberry (1473 mg/kg). The findings that chokecherry has very high antioxidant capacity and caffeic acid levels, are useful for developing novel value-added antioxidant products and also provide evidence essential for breeding novel cultivars of fruit plants with strong natural antioxidants.

Antioxidant properties of diverse cereal grains: A review on in vitro and in vivo studies

Cereal grains and products have gained popularity in contributing to healthy eating behavior because of their antioxidant properties associated with protection against chronic diseases. In this review, notable studies on the in vitro and in vivo antioxidant activity of commonly consumed cereal grains are summarized. Cereals contain phytochemicals or certain minor components with antioxidant properties. The antioxidant potential of cereals depends on their bioaccessibility, absorption in the gastrointestinal and their bioavailability utilization in vivo. The in vitro gastrointestinal digestion and fermentation of cereals increased their antioxidant potentials which are significantly correlated with their total phenolic contents. Most studies performed in vivo have been concerned with the antioxidant properties of colored rice, wheat bran and rye products. There are inadequate in vitro and in vivo studies on antioxidative potentials of fermented versus unfermented cereals. Therefore, further studies are necessary to maximize possible health benefits of cereal antioxidative phytochemicals.

Comparison of Antioxidant Activities of Different Colored Wheat Grains and Analysis of Phenolic Compounds

Extracts from six wheat varieties (three purple, one yellow, two red, and one white) were evaluated and compared for their antioxidant capacities against oxygen radical and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. Phenolic composition in the extracts was examined by high-performance liquid chromatography and mass spectrometry. The results showed that Charcoal purple wheat had remarkable antioxidant activity (up to 6899 μmol/100 g) followed by Red Fife wheat and yellow Luteus wheat. White AC Vista wheat, due to its lowest phenolic content, exhibited the weakest antioxidant property. The major phenolic composition identified in wheat grains consisted of phenolic acids, flavones, flavonols, and anthocyanins. The former three components were detected in all of the wheat varieties, whereas anthocyanins were identified only in purple wheat. Therefore, anthocyanins could be the major compounds distinguishing purple wheats from other colored wheats with high antioxidant activity.

Antioxidant Activity of Commercial Wild Rice and Identification of Flavonoid Compounds in Active Fractions

The health benefits of whole grain consumption have been attributed to their content of complex carbohydrates, vitamins, minerals, and other phytochemical constituents. Wild rice is a whole grain finding applications in gourmet foods due to its nutritional value and unique taste. However, little is known about its antioxidant properties and phytochemical components. The objectives of this study were to evaluate the antioxidant properties of wild rice. Eleven commercial wild rice samples (raw, mixed, and processed) were extracted with acetone and fractionated using a Sephadex LH-20 column. 2,2-Diphenyl-1-picrylhydrazyl radical (DPPH(*)) scavenging activity, oxygen radical absorbance capacity (ORAC), and total phenolic content were evaluated to determine the antioxidant properties of wild rice. The antioxidant activity of wild rice was found to be 30 times greater than that of the control white rice. Significant differences (p < 0.05) in antioxidant activities were found among raw, mixed, and processed samples. For raw samples, DPPH(*) radical scavenging activities and ORAC values ranged from 611 to 917 micromol of Trolox equivalent (TE)/100 g and from 4069 to 6064 micromol of TE/100 g, respectively. For mixed and processed wild rice, DPPH(*) radical scavenging activities were 373 and 441 micromol of TE/100 g, respectively. The corresponding ORAC values were 2284 and 2557 micromol of TE/100 g. Total phenolic content (TPC) of raw wild rice varied from 2472 to 4072 mg of ferulic acid equivalent (FAE)/kg, higher than that of the mixed sample (1460 mg of FAE/kg) and processed sample (2076 mg of FAE/kg). TPC was highly correlated with total antioxidant activity of wild rice (r = 0.92). Tandem mass spectrometric techniques revealed the antioxidants identified in wild rice to be flavonoid glycosides (diglucosyl apigenin, glucosyl-arabinosyl apigenin, and diarabinosyl apigenin) in factions 2 and 3 and flavan-3-ols (catechin, epicatechin, and oligomeric procyanidin) in fractions 4 and 5.

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.

Phenolic Content, Composition, Antioxidant Activity, and Their Changes during Domestic Cooking of Potatoes

Potatoes in the diet contribute significantly to antioxidant daily intake worldwide. The influence of different domestic cooking conditions, boiling, microwaving, and baking, on total phenolics (TP), antioxidant capacity, phenolic composition, and tryptophan content was studied using eight commercial potato varieties. The antioxidant capacity was detected by the methods of oxygen radical absorbance capacity assay (ORAC) and the 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH(*)) assay. The phenolic composition and tryptophan content were determined using high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD), whereas phenolics and tryptophan were identified by means of HPLC-mass spectrometry, HPLC-DAD, and authentic standards. Antioxidant capacity was influenced by potato variety and cooking conditions; however, cooked potatoes retained 68-97% ORAC value depending on cooking procedure and variety. Chlorogenic acid and its isomers dominated the phenolic composition of each variety involved in this study. ORAC and TP were highly and positively correlated (r = 0.9119). Norkotah ranked highest in chlorogenic acid content and antioxidant value. Principal component analysis showed different cooking processes did not influence the trend of the antioxidant profile of the eight potato varieties, but specific compounds exert influence on the antioxidant capacity. The results imply that the potato varieties rich in antioxidant components could be good antioxidant sources as activities are not greatly affected by different cooking conditions.