Tentative Avenanthramide‐Modifying Enzyme in Oats

A decrease of the concentration of the synthetic avenanthramide N‐(4′‐hydroxy‐(E)‐cinnamoyl)‐5‐hydroxyanthranilic acid in a buffered slurry of milled oat groats (Avena sativa L.) was temperature and pH‐dependent, with a maximum rate at 30°C and pH 9. The reaction was inhibited in the presence of 2‐mercaptoethanol, acetic acid and at high temperature; suggestive of enzymatically catalyzed nature. Among eight different synthetic avenanthramides tested, the tentative enzyme had highest affinity for avenanthramides comprising caffeic and p‐coumaric acids and lowest for those comprising sinapic and ferulic acids. The activity was found in samples from several oat cultivars and was equally pronounced in both bran and endosperm flour of oats. Steeping of oat grains did not influence the reaction.     

Effects of commercial processing on levels of antioxidants in oats (Avena sativa L.)

The effects of various commercial hydrothermal processes (steaming, autoclaving, and drum drying) on levels of selected oat antioxidants were investigated. Steaming and flaking of dehulled oat groats resulted in moderate losses of tocotrienols, caffeic acid, and the avenanthramide Bp (N-(4'-hydroxy)-(E)-cinnamoyl-5-hydroxy-anthranilic acid), while ferulic acid and vanillin increased. The tocopherols and the avenanthramides Bc (N-(3',4'-dihydroxy-(E)-cinnamoyl-5-hydroxy-anthranilic acid) and Bf (N-(4'-hydroxy-3'-methoxy)-(E)-cinnamoyl-5-hydroxy-anthranilic acid) were not affected by steaming. Autoclaving of grains (including the hulls) caused increased levels of all tocopherols and tocotrienols analyzed except beta-tocotrienol, which was not affected. Vanillin and ferulic and p-coumaric acids also increased, whereas the avenanthramides decreased, and caffeic acid was almost completely eliminated. Drum drying of steamed rolled oats resulted in an almost complete loss of tocopherols and tocotrienols, as well as a large decrease in total cinnamic acids and avenanthramides. The same process applied to wholemeal made from groats from autoclaved grains resulted in less pronounced losses, especially for the avenanthramides which were not significantly affected.     

Contents of Antioxidant Compounds in Turkish Oats: Simple Phenolics and Avenanthramide Concentrations

Antioxidant products such as simple phenolic compounds and avenanthramides in oat (Avena sativa L.) may have health‐promoting effects on humans. Therefore, it is very important to determine simple phenolics and avenanthramide concentrations of different genotypes of oats from different regions of the world. The aim of this research was to determine the concentrations of simple phenolics and avenanthramides of Turkish oat genotypes. According to the results, Turkish oat genotypes were significantly different for three major avenanthramides (Bc, Bp, and Bf) and the simple phenolic, ferulic acid (FA), while not significantly different for p‐coumaric acid (PCA). Ferulic acid concentrations of Turkish oat genotypes were higher than a standard U.S. cultivar, Belle. However, the major avenanthramide concentrations of Turkish oat genotypes were significantly lower than Belle.     

Avenanthramides in oats (Avena sativa L.) and structure-antioxidant activity relationships

Eight avenanthramides, amides of anthranilic acid (1) and 5-hydroxyanthranilic acid (2), respectively, and the four cinnamic acids p-coumaric (p), caffeic (c), ferulic (f), and sinapic (s) acid, were synthesized for identification in oat extracts and for structure-antioxidant activity studies. Three compounds (2p, 2c, and 2f) were found in oat extracts. As assessed by the reactivity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH), all avenanthramides except 1p showed activity. Initially, the antioxidant activity of the avenanthramides decreased in a similar order as for the corresponding cinnamic acids, that is: sinapic > caffeic > ferulic > p-coumaric acid. The avenanthramides derived from 2 were usually slightly more active than those derived from 1. All avenanthramides inhibited azo-initiated peroxidation of linoleic acid. 1c and 1s were initially the most effective compounds. The relative order of antioxidant activities was slightly different for the DPPH and the linoleic acid assays run in methanol and chlorobenzene, respectively.     

Humus quantity and quality of an entic Haplustoll under different soil‐crop management systems

Abstract

The effects of different management systems on the level and composition of humified organic matter in an entic Haplustoll from the semiarid Pampean region were studied. The systems were: TPc, wheat‐mixed pasture; TV, wheat (Triticum aestivum), oat (Avena sativa), corn (Zea mays) and triticale grasses; TP, wheat‐cattle grazing; and V, virgin, non cultivated. Humic acids were extracted, fractionated, and analyzed for their organic carbon (OC) content, elemental composition, and E4:E6 spectral ratios. The infrared (IR), electron spin resonance (ESR). and ¹³C‐NMR spectra were registered on these humic acids. The TP rotation showed the lowest humic acid‐carbon to fulvic acid‐carbon (HA‐C:FA‐C) ratio. The lower O:C ratio of humic acids from the cropped soils indicates a higher level of oxidation than that of the virgin one. The comparison of the different methodologies allowed us to conclude that crop rotations and conservation tillage were adequate to mantain the level and composition of the soil organic matter and humus which affected the soil fertility and level of productivity     

Levels of Avenanthramides and Activity of Hydroxycinnamoyl‐CoA:Hydroxyanthranilate N‐Hydroxycinnamoyl Transferase (HHT) in Steeped or Germinated Oat Samples

Concentrations of avenanthramides and activity of the biosynthetic enzyme hydroxycinnamoyl‐Co A:hydroxyanthranilate N‐hydroxycinnamoyl transferase (HHT) were analyzed in dry or, steeped nonmilled or milled, non‐heat‐treated (raw) or heat‐treated oat samples (Avena sativa L.). Increased avenanthramide concentrations were found when intact raw groats were steeped. The increase was time‐ and temperaturedependent and maximal after 10 hr of steeping at 20°C. Continuous germination in air, after steeping, only contributed to a further increase in avenanthramides when steeping times were shorter than 10 hr. Concentrations of avenanthramides and HHT activity were positively correlated during steeping of intact groats at 8 and 20°C. The increase in avenanthramides was suggested to be due to de novo synthesis and a whole grain structure seemed to be required as no increase was found when groats were milled before steeping. Avenanthramide levels also increased when heat‐treated samples, lacking HHT activity, were steeped. This increase may be due to release of bound forms, possibly formed during the preceding heat treatment.     

Contents of phenolic acids, alkyl- and alkenylresorcinols, and avenanthramides in commercial grain products

The contents of free and total phenolic acids and alk(en)ylresorcinols were analyzed in commercial products of eight grains: oat (Avena sativa), wheat (Triticum spp.), rye (Secale cerale), barley (Hordeum vulgare), buckwheat (Fagopyrum esculentum), millet (Panicum miliaceum), rice (Oryza sativa), and corn (Zea mays). Avenanthramides were determined in three oat products. Free phenolic acids, alk(en)ylresorcinols, and avenanthramides were extracted with methanolic acetic acid, 100% methanol, and 80% methanol, respectively, and quantified by HPLC. The contents of total phenolic acids were quantified by HPLC analysis after alkaline and acid hydrolyses. The highest contents of total phenolic acids were in brans of wheat (4527 mg/kg) and rye (4190 mg/kg) and in whole-grain flours of these grains (1342 and 1366 mg/kg, respectively). In other products, the contents varied from 111 mg/kg (white wheat bread) to 765 mg/kg (whole-grain rye bread). Common phenolic acids found in the grain products were ferulic acid (most abundant), ferulic acid dehydrodimers, sinapic acid, and p-coumaric acid. The grain products were found to contain either none or only low amounts of free phenolic acids. The content of avenanthramides in oat flakes (26-27 mg/kg) was about double that found in oat bran (13 mg/kg). The highest contents of alk(en)ylresorcinols were observed in brans of rye (4108 mg/kg) and wheat (3225 mg/kg). In addition, whole-grain rye products (rye bread, rye flour, and whole-wheat flour) contained considerable levels of alk(en)ylresorcinols (524, 927, and 759 mg/kg, respectively).     

Nutrient solution nitrogen form and barley yellow dwarf virus disease tolerance in oat and wheat

Abstract

The form of nutrient solution nitrogen (either NH₄‐N or NO₃‐N or mixtures of the two) provided to plants influences the severity of many crop diseases. This greenhouse study was conducted to determine how growth, grain yield, and yield components of oat (Avena sativa L.) and wheat (Triticum aestivum L.) plants given nutrient solutions containing different ratios of NO₃‐N to NH₄‐N would react to barley yellow dwarf virus (BYDV) infection. Fifteen‐day‐old seedlings (2nd leaf stage) were either infected with BYDV (PAV strain) or left uninfected. Nutrient solution treatments (started 19 d after germination) provided three ratios of NO₃‐N to NH₄‐N (100% NO₃, 50:50 NH₄:NO₃, or 100% NH₄) for a 30‐d period, after which plant height and tillers plant^?1 were measured. Oat and wheat plants given NH₄ had fewer tillers than plants given the other nutrient solution treatments. BYDV‐infected oat and wheat plants were shorter than uninfected plants. All pots then received NO₃ nutrient solution until plant maturity, after which days to anthesis, primary tiller height, grain yield and yield components were measured. In the NH₄ nutrient solution treatments, BYDV infection significantly reduced individual kernel weight in oat and primary tiller height in wheat. These same measures were not significantly affected by BYDV infection in the NO₃ or NH₄NO₃ nutrient solution treatments. There were no other significant nutrient solution by BYDV infection interactions for any other dependent variable measured. Nutrient solution treatments had no significant effect on grain yield, but BYDV infection reduced grain yield by 45% in oat and 46% in wheat. In conclusion, nutrient solution N form interacted with BYDV infection to alter disease tolerance in oat (kernel weight) and wheat (primary tiller height), but these alterations had no effect in ameliorating grain yield loss caused by BYDV disease.     

Factors related to iron uptake by dicotyledonous and monocotyledonous plants III. Competition between root and external factors for Fe

In comparison studies (11, 12), monocotyledonous corn (Zea mays L.) and oats (Avena byzantina C. Koch) did not respond to Fe stress as effectively nor to the same degree as the dicotyledonous soybeans (Glycine max (L.) Merr.) or tomatoes (Lycopersicon esculentum Mill.). Both the Fe‐inefficient and Fe‐efficient corn and oats developed Fe chlorosis; the Fe‐efficient dicotyledonous plants were green. In the present study, the method of inducing Fe stress was changed to make it less severe. Instead of using only NO₃‐N and no Fe to induce Fe stress (11, 12), both NH₄‐N and NO₃‐N were used along with varied concentrations of Fe. Iron stress was induced with BPDS (4,7‐diphenyl‐l, 10‐phenan‐throline disulfonic acid) and phosphate; both competed with the plant for Fe. Phosphate also inhibits reduction of Fe³⁺ to Fe²⁺ (12). This method of inducing Fe stress in the plants was less severe than using only NO₃‐N and no Fe in the nutrient solutions and we were able to measure a difference in Fe‐stress response for all four plant species (Fe‐inefficient and Fe‐efficient). At the lower Fe treatments, the roots of Fe‐efficient plants usually reduced more Fe³⁺ to Fe²⁺ than did the roots of Fe‐inefficient plants. The ‘inefficient’ ys₁ corn and TAM 0–312 oat roots did not compete with BPDS or phosphate for Fe as effectively as did the ‘efficient’ WF9 corn and Coker 227 oat roots. The same type mechanism for solubilization, absorption, and transport of Fe seems to function in both monocotyledenous and dicotyledenous plants but it is more effective and more readily detected in the dicot than in the monocot plants. The reactions involved in reduction of Fe³⁺ to Fe²⁺ seemed to be confined inside or at the root surface for the inefficient genotypes; the efficient genotypes alter the ambient medium to a greater degree.     

Nitrogen effects on yield,beta‐glucan content,and other quality factors of oat and waxy hulless barley

Abstract

Oat (Avena sativa L.) and waxy hulless barley (Hordeum vulgare L.) are important sources of water soluble plant fiber (ß‐glucan) needed in human diets to lower serum cholesterol. Recent studies have shown grain ß‐glucan content is influenced by soil type and environment, however, nitrogen (N) response data for oat and waxy hulless barley are lacking. In this study, we evaluated N effects on grain ß‐glucan content and yield; grain yield, protein content, and test weight; and total dry matter production and N utilization of oat and waxy hulless barley. Rates of applied N were 0, 34, 67, and 101 kg N/ha at three field environments in central Montana during 1989 and 1990. Nitrogen increased all variables except test weight and ß‐glucan content. Waxy hulless barley grain yields fluctuated from 0.82 to 4.11 Mg/ha, ß‐glucan content from 62 to 76 g/kg, and ß‐glucan yields from 51 to 354 kg/ha. Oat yields ranged from 0.85 to 3.83 Mg/ha, ß‐glucan content from 37 to 51 g/kg, and ß‐glucan yields from 35 to 178 kg/ha. Oat ß‐glucan content was positively related to grain protein content, and waxy hulless barley ß‐glucan content was positively related to test weight. ß‐glucan content appeared more related to environmental factors other than N.     

Antioxidant Activity and Phenolic Contents of Oat Groats and Hulls

Research was initiated to measure antioxidant activity of extracts from oat (Avena sativa L.) groats and hulls and the concentrations of phenolic substances that may contribute to antioxidant activity. Antioxidant activity of ethanolic extracts of four cultivars was evaluated by an in vitro assay that measures the inhibition of coupled autoxidation of linoleic acid and β-carotene. Total phenolic content was determined using Folin and Ciocalteau's phenol reagent and was expressed as gallic acid equivalents. Phenolic compounds were separated by reversed-phase HPLC and detected at 290 nm. Peaks were identified by comparing retention times and spectra with known standards and verified with internal standards. Groats had significantly higher antioxidant activity than hulls. For two cultivars, total phenolic content was similar in groats and hulls, whereas one cultivar had higher and another lower total phenolic content in groats than hulls. Ten phenolic compounds were separated and identified in extracts, and one flavan-3-ol and three avenanthramides were tentatively identified. The concentrations of many of these compounds differed among cultivars and between fractions. In general, caffeic acid and the avenanthramides were predominantly found in groats, whereas many of the other phenolics were present in greater concentrations in hulls.     

Differential tolerances of oat cultivars to aluminum in nutrient solutions and in acid soils of Poland

Aluminum tolerant oat cultivars are needed for use on acid soil sites where neutralization of soil acidity by liming is not economically feasible. Oat germplasm in Poland has not been examined for range of Al tolerance. Eleven Polish oat cultivars were screened for Al tolerance in nutrient solutions containing 0, 5 and 15 mg L^‐1 Al. Three of these cultivars showing high to moderate tolerance to Al in nutrient solutions were also grown in greenhouse pots of soil and in field plots of soil over a pH range of 3.8 to 5.5 as determined in 1 N KC1.

The eleven oat cultivars differed significantly in tolerance to Al in nutrient solutions. Based on relative root yield (15 mg L^‐1 Al/no A1%), the cultivars ‘Solidor’ and ‘Diadem’ were most tolerant and ‘Pegaz’ and ‘B‐20’ were least tolerant. For these three cultivars, the order of tolerance to acid soil agreed with the order of tolerance to Al in nutrient solution ‐ namely, Solidor > Diadem > Leanda. Hence, for these cultivars, the nutrient solution methods used appear adequate for selecting plants that are more tolerant to Al in strongly acid soils. Additional study is needed to assess the value of this method for screening a broad range of germplasm.

Superior tolerance of the Solidor cultivar to acid soil was associated with significantly higher concentrations of N in the grain. Hence, results suggest that selecting for acid soil or Al tolerance may increase N efficiency in oats.     

Chemical studies on soil humic acids

Abstract

Relationships between elementary compositions and types of humic acids or the "degrees of humification were studied statistically using 39 humic acids prepared from various types of soils. Mean values of C%. H%. N%, 0%, H/C, N/C, and O/C of the different types of humic acids (A. B. Rp(l), Rp(2). and Po) were compared. The elementary compositions of various types of humic acids were proven by variance analyses to be significantly distinct. Linear regression analyses of C%, H%, N%. 0%, H/C, N/C, or O/C on RF or AlogK values were also carried out on 35 humic acids excluding the P_+~+++ type humic acids. The linear associations were found to be significant between C%-RF (5% level), H%-RF, H%-?logK, H/C-RF and HIC-?logK (0.1% level), N/C-RF(O.1% level). N%-RF(l% level), N%-?logK N/C-?logK(5% level), and ?logK (1% level), while no significant relationship was found with regard to C%;-?logK, 0%-?logK (both 5% level) and O/C-RF and O/C-?logK (l0% level). Carbon and oxygen contents of humic acids may be apt to reflect the different conditions of soils. The deeper the visible light absorption of humic acids and so the higher the degrees of humification, the lower the hydrogen contents of humic acids were. Though nitrogen content showed a trend similar to the trend of hydrogen content against RF values as a whole. the nitrogen content of less humified humic acids (Rp type) varied from very low to very high values. suggesting the enrichment of nitrogen into humic acid molecules in the early stage of humification. In the H/C versus O/C diagram, humic acids occupied an area reserved for the oxydation products of lignins. The area was fairly wide and “J”-shaped, that is, in the early to the middle stage of humification humic acids were arranged in the direction of dehydrogenation or demethanation, and in the later stage they were arranged in the direction of dehydration.     

Timing and level of nitrogen supply affect nitrogen distribution and recovery in two contrasting oat genotypes

Human diets containing oat (Avena sativa L.) grain offer health benefits resulting in an emerging interest in oat improvement. Information on nitrogen (N) uptake, distribution, and use efficiency (NUE) in oat is limited. A greenhouse study using a ¹⁵N‐labeling technique was conducted to determine the responses of two contrasting oat genotypes to timing and level of N deficiency. Hulled oat cv. Prescott and hulless cv. AC Gehl were grown in soil‐mix pot culture with five N treatments applied through modified Hoagland solutions. Differences in ¹⁵N accumulation, ¹⁵N distribution, plant N originating from the labeled source, and NUE between the contrasting cultivars, were examined for each N strategy. Level of N deficiency and timing of N supply of ¹⁵NH₄¹⁵NO₃ greatly affected ¹⁵N distribution, the origins of plant N, and the amount of ¹⁵N recovered in the plant. When N was supplied from seedling emergence to maturity (T₁), AC Gehl accumulated 61% more ¹⁵N in the shoots, but 46% less ¹⁵N in the grain than Prescott (0.43 vs. 0.80 mg plant^–1), indicating that AC Gehl was less effective in producing grain yield than Prescott as AC Gehl produced greater total dry matter (DM). Withholding N supply until flag‐leaf stage (FL) increased ¹⁵N in the grain of both cultivars by 29.6%, resulting in the highest NUE. In most cases, there were larger portions of plant N derived from the labeled source for AC Gehl than for Prescott. Our results suggest that greater NUE in the newly released AC Gehl was associated with N accumulation in the vegetative tissues. It is concluded that genotype improvement of hulless oat should be focused on enhancing N‐translocation efficiency.     

Compound specific plant amino acid δ15N values differ with functional plant strategies in temperate grassland

The distribution and natural abundance isotopic (δ¹⁵N) content of whole tissue and individual amino acids in plants in a temperate grassland were determined using ion chromatography (IC), continuous flow‐isotope ratio mass spectrometry (CF‐IRMS), and gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS). The results showed that the selected plants (Lolium perenne, Juncus effusus, and Brachythecium rutabulum) differed in their amino acid content and distribution from the parent grassland soil. Bulk and individual amino acid δ¹⁵N isotope signatures were different between the plants, which concurred with their functional strategy in relation to the relative acquisition of available N sources. The individual amino acid δ¹⁵N values of histidine and phenylalanine could be used to differentiate between the three plant species.     

Effect of peduncle‐perfused nitrogen,sucrose, and growth regulators on barley and wheat amino acid composition

Abstract

Nitrogen (N) or growth regulator application to small grain cereals near anthesis has been demonstrated to alter grain fill and grain yield, the protein yield and nutritional quality may also be modified by these management factors. The objective of this study was to determine whether delivery of N, growth regulator, or sucrose solutions into greenhouse‐grown barley (Hordeurn vulgare L. cv. Leger) or wheat (Triticum aestivum L. cv. Katepwa), plants through peduncle perfusion altered the amino acid composition of the grain. The following treatments were tested: N (25 and 50 mM), chlormequat (30 μM), ethephon (15 μM), N + chlormequat, N + ethephon, detillering + N, sucrose (250 mM), distilled water check, and non‐perfused check. Perfusion lasted 30 d beginning 5 to 8 d after spike emergence. Addition of N via peduncle perfusion increased protein concentrations and concentrations of all amino acids in both barley and wheat when expressed in terms of grain dry matter. Protein yield and lysine content were also increased. However, the increase in essential amino acids such as lysine, methionine, threonine, isoleucine, arginine, and leucine was relatively small, and the proportions of these amino acids in the grain protein were actually reduced. The sucrose treatment only affected wheat, increasing lysine concentration and decreasing the total protein concentration. Growth regulators used in this study did not alter protein yield or amino acid composition in either crop.     

Critical evaluation of three indirect assays for quantifying phytosiderophores released by the roots of Poaceae

Indirect assays are commonly used to measure phytosiderophore (PS) concentrations in the root exudates of grasses. The Cu‐mobilizing, Cu‐CAS and Fe‐binding assays are three commonly used assays but there have been few published attempts to validate or calibrate them rigorously. Thus, we undertook to compare, validate and, where appropriate, to improve and/or optimize each assay. Ethylenediamine‐N,N′‐diacetic acid (EDDA) and N‐2‐hydroxyethylethylenediamine‐N,N′,N′‐triacetic acid (HEDTA) bracket deoxymugineic acid for binding strength with both Fe and Cu and were thus used as model ligands. For the Cu‐mobilizing assay, reasonable regressions (as R²) were obtained between measured and known ligand concentrations for all resin combinations tested. However, the relationship was non‐stoichiometric; less than 5% of the ligand present was recovered as a Cu‐complex. Testing of the Cu‐CAS assay yielded good 1:1 stoichiometric relationships (slopes of 0.97 and 1.08 for EDDA and HEDTA, respectively) with little scatter (R²= 0.97). However, the limits of quantification were approximately 30 μm , which is greater than concentrations generally found in root‐exudate collections. Thus, the Cu‐CAS assay is best suited to situations where large concentrations of PSs are expected. Results from the original Fe‐binding assay indicated a lack of linearity and considerable scatter (R²= 0.57 for EDDA; R²= 0.28 for HEDTA). Thus, as published, use of the original Fe‐binding assay is not recommended. The effects of filter paper, FeCl₃ reagent concentration and increase in the reduction time were tested and a revised Fe‐binding assay developed with both good stoichiometry and great precision (R²≥ 0.99). We suggest the use of the revised Fe‐binding assay in most situations where PS concentration would be expected to be < 30 μm .     

Fiber‐optic spectrophotometry of cowpea nodules treated with nitrate or ammonium

Abstract

Cowpea nodules (Vigna unguiculata [L.] Walp. cv. CB5) were pierced with two opposing optical fibers (280 μm diameter), and absorbance spectra of 0.1 mm of nodule tissue were recorded from 415 to 600 nm using a modified spectrophotometer with a nodule sampling stage.

The nodule spectra exhibited two absorbance bands, a major band in the near‐UV (415–450 nm) and a lesser one in the green‐yellow region (510–585 nm); the latter exhibited a prominent peak at 550 nm. Nodule spectra were consistent with the superposition of the spectra of ferroleghemoglobin (Lb²⁺), oxyleghemoglobin (Lb²⁺‐ O₂), and cytochrome c (550 nm). The detection of leghemoglobin in vivo was confirmed by demonstrating the reversibility of binding of CO to Lb, and by comparing the spectra of live nodules with those obtained from anaerobic leghemoglobin preparations.

The effects on the nodule spectra of two successive applications (36 and 39 days after planting) of 5 and 10 mM NO₃ ^‐ or NH₄ ⁺ to the nutrient solution bathing the nodulated roots were determined. The spectra of NO₃ ^‐‐ and NH₄ ⁺‐treated nodules were indistinguishable; in each case the height of both the near‐UV and green‐yellow absorbance bands decreased with treatment. Treatment with N caused a significant reduction in the area of the green‐yellow absorbance band.

The spectra of green leghemoglobin pigments were obtained from senescent nodules; these exhibited a reduction in the height of the near‐UV absorbance band and a flattening of the green‐yellow band similar to that of nodules treated with N, but the broadening of the near‐UV band was greater in green nodules.     

Phytochemical and fiber components in oat varieties in the HEALTHGRAIN Diversity Screen

The levels and compositions of a range of phytochemicals (sterols, tocols, avenanthramides, folates, phenolic acids) and dietary fiber components were determined in five oat cultivars (four husked and one naked) grown on a single site in 2005. The total levels of tocols, phenolic acids, and avenanthramides varied by over 2-fold between cultivars, but less variation occurred in total sterols and total folates. Limited variation was also observed in the dietary fiber content and composition of the four husked lines. These results indicate that it may be possible to selectively breed for lines with high contents of dietary fiber and specific groups of phytochemicals.     

Prediction of β‐Glucan Concentration Based on Viscosity Evaluations of Raw Oat Flours from High β‐Glucan and Traditional Oat Lines

Rheological properties of raw oat flour slurries were determined in experimental high β‐glucan (≤7.8%) and traditional oat lines (4–5% β‐glucan) grown in two consecutive years. Three different media were used to disperse oat flours: deionized water, silver nitrate solution (to inactivate endogenous enzymes), and alkali solution (to solubilize both water‐soluble and water‐insoluble β‐glucans). Significant correlations (P < 0.05) between viscosity of slurries and β‐glucan concentration obtained in either deionized water (r = 0.833), silver nitrate (r = 0.940), or alkali (r = 0.896) solutions showed that β‐glucans were the main contributor to oat extract viscosity. The highest correlation was obtained in silver nitrate solution, suggesting that inactivating endogenous enzymes is important to obtain high correlations. Predictive models of oat β‐glucan concentration based on the viscosity profile were developed using partial least squares (PLS) regression. Prediction of β‐glucan concentration based on viscosity was most effective in the silver nitrate solution (r = 0.949, correlation coefficient of predicted vs. analyzed β‐glucans) and least effective in the alkali solution (r = 0.870). These findings demonstrate that the β‐glucan in oat could be predicted by measuring the viscosity of raw flours in silver nitrate solution, and this method could be used as a screening tool for selective breeding.