Oat Kernel Research Articles

Occurrence of Alternaria secondary metabolites in milling oats and its de-hulled fractions from harvest years 2017 to 2021

In this study, secondary metabolites produced by Alternaria were investigated for their presence in milling oats. For this purpose, pre-cleaned milling oat samples (n = 193), intended for human consumption, out of harvest years 2017 to 2021 originating from different northern European countries were analysed by LC-MS/MS. Alternariol and alternariol methyl ether were positively identified in 38% of the samples with mean values of 2.1 µg/kg and 1.2 µg/kg, respectively. The highest concentrations of 50.5 µg/kg alternariol and 24.2 µg/kg of alternariol methyl ether were detected in a Latvian sample. Tenuazonic acid was found in 45% of all samples, with a mean concentration of 28.9 µg/kg and a maximum concentration of 1430 µg/kg, also in a Latvian sample. Tentoxin was detected in 49% of all samples with a mean value of 1.7 µg/kg. The Alternaria metabolite most frequently detected in 96% of all samples was infectopyrone with a mean concentration of 593 µg/kg and a maximum value reaching up to 3990 µg/kg in a German sample. In addition, eight oat samples were selected to investigate to what extent the Alternaria metabolites are distributed between the oat hulls and the oat kernels. After de-hulling, approximately 23% of Alternaria metabolites were found in the remaining oat kernels. According to the results, alternariol, infectopyrone and altersetin were present in the kernels with the lowest proportion of 10%–20% on average, respectively. The values for tentoxin showed that about 60% of tentoxin was contained in the hulls, while almost 40% remained in the oat kernel. This suggests that potential health risks posed by Alternaria secondary metabolites and metabolites of other fungal genera in milling oats can be reduced by de-hulling.

Multi-Bioactivity of Protein Digests and Peptides from Oat (Avena sativa L.) Kernels in the Prevention of the Cardiometabolic Syndrome.

The aim of this study was to characterize the digests and peptides derived from oat kernel proteins in terms of their major enzyme inhibitory activities related to the prevention of cardiometabolic syndrome. It also entailed the characteristics of antioxidant bioactivity of the analyzed material. The study was carried out using coupled in silico and in vitro methods. The additional goal was to investigate whether identified peptides can pervade Caco-2 cells. Based on the results of bioinformatic analysis, it was found that the selected oat proteins may be a potential source of 107 peptides with DPP-IV and/or ACE inhibitory and/or antioxidant activity. The duodenal digest of oat kernels revealed multiple activities. It inhibited the activities of the following enzymes: DPP-IV (IC50 = 0.51 vs. 10.82 mg/mL of the intact protein), α-glucosidase (IC50 = 1.55 vs. 25.20 mg/mL), and ACE (IC50 = 0.82 vs. 34.52 mg/mL). The DPPH• scavenging activity was 35.7% vs. 7.93% that of the intact protein. After in silico digestion of oat proteins, 24 peptides were selected for identification using LC-Q-TOF-MS/MS. Among them, 13 sequences were successfully identified. One of them, i.e., VW peptide, exhibited triple activities, i.e., DPP-IV and ACE inhibitory and DPPH• scavenging activity. The multifunctional peptides: PW, TF, VF, and VW, were identified in the basolateral samples after transport experiments. Both in silico and in vitro analyses demonstrated that oat kernel proteins were the abundant sources of bioactive digests and peptides to be used in a diet for patients suffering from cardiometabolic syndrome.

Potential Health Risk Associated with Mycotoxins in Oat Grains Consumed in Spain.

Spain is a relevant producer of oats (Avena sativa), but to date there has been no study on the occurrence/co-occurrence of mycotoxins in oats marketed in Spain. The present study is addressed to overcome this lack of knowledge. One hundred oat kernel samples were acquired across different Spanish geographic regions during the years 2015–2019 and analyzed for mycotoxin content using an ultra-high performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC–ESI–MS/MS) method and matrix-matched calibration. The focus was on the regulated mycotoxins although other relevant mycotoxins were considered. The percentage of incidence (levels ≥ limit of detection), mean and range (ng/g) of mycotoxins were as follows: zearalenone (66%, mean 39.1, range 28.1–153), HT-2 toxin (47%, mean 37.1, range 4.98–439), deoxynivalenol, (34%, mean 81.4, range 19.1–736), fumonisin B1 (29%, mean 157.5, range 63.2–217.4), and T-2 toxin, (24%, mean 49.9, range 12.3–321). Fumonisin B2, 3-acetyldeoxynivalenol, aflatoxins B1, B2, and G2, and ochratoxin A were also detected at low levels, but aflatoxin G1 was not. The maximum limits established by the European Commission for unprocessed oats were not exceeded, except for zearalenone (in one sample), and the sum of aflatoxins (in two samples). Mycotoxin co-occurrence at quantifiable levels in the same sample (two to five combinations) was found in 31% of samples. The most common mixtures were those of HT-2 + T-2 toxins alone or together with deoxynivalenol and/or zearalenone.

Impact of glyphosate applied preharvest on oat kernel quality

AbstractBackground and objectivesPreharvest glyphosate is applied to oats for weed control and as a desiccant. The effect of glyphosate applied at various stages of oat physiological maturity on oat end product quality has not been reported previously. In this study, the effects of glyphosate application at two separate stages of physiological maturity on oat groat quality and rolled oats quality were determined.FindingsOat was grown at two locations. Glyphosate was applied at the soft dough, physiological maturity stages, or not applied. Effect of preharvest glyphosate application at the oat soft dough stage on groat hardness, groat percentage (0.7%–3.7% decrease by cultivar), and percent plump groats (0.3%–6.1% decrease by cultivar), when compared to untreated oats, was noticeable. However, glyphosate applied at physiological maturity (manufacturer's recommendation) did not detrimentally affect groat starch (average 60.3%) or end product quality.ConclusionsTherefore, from an end‐user perspective, applying glyphosate preharvest at oat physiological maturity does not impact oat quality.Significance and noveltyGlyphosate when applied preharvest to oats can control weed and facilitate harvest, a boon to farmers. Final oat quality, a decisive factor for commercial processor use, was not detrimentally affected when glyphosate was applied at oat physiological maturity.

A Systematic Review and Meta-Analysis of Randomized Controlled Trials on the Effects of Oats and Oat Processing on Postprandial Blood Glucose and Insulin Responses

Oats are a whole grain cereal with potentially favorable effects on the postprandial glycemic response; however, the effects of oat processing on these glycemic benefits are not well understood. The study objective was to determine the effects of differently processed oats on the postprandial blood glucose and insulin responses relative to refined grains. Eleven electronic databases were systematically searched to identify studies published up to and including May 2019. Randomized controlled trials comparing the postprandial blood glucose and insulin responses to oats compared with any refined grain were included, so long as the available carbohydrate content of the test meals was similar. Pooled effect sizes were computed using the difference in incremental area under the curves for blood glucose and insulin following the consumption of oats compared with the refined grain control. Ten publications were included, with intact oat kernels studied in 3 comparisons, thick oat flakes (>0.6 mm) in 7 comparisons, and thin/quick/instant oat flakes (≤0.6 mm) in 6 comparisons. Compared with the consumption of the refined grain control, the consumption of intact oat kernels was associated with significant reductions in postprandial blood glucose (-45.5 mmol x min/L; 95% CI: -80.1, -10.9 mmol x min/L; P=0.010) and insulin (-4.5 nmol x min/L; 95% CI: -7.1, -1.8 nmol x min/L; P=0.001) responses; the consumption of thick oat flakes was associated with significant reductions in postprandial blood glucose (-30.6 mmol x min/L; 95% CI: -40.4, -20.9 mmol x min/L; P<0.001) and insulin (-3.9 nmol x min/L; 95% CI: -5.3, -2.5 nmol x min/L; P<0.001) responses; but, the consumption of thin/quick/instant oat flakes was not associated with any effects on the postprandial blood glucose and insulin responses. A disruption in the structural integrity of the oat kernel is likely associated with a loss in the glycemic benefits of oats.

Study on Mechanical Properties for Shearing Breakage of Oat Kernel

Abstract Breaking force, deformation, breaking energy, strength, hardness and rigidity of oat kernel under different loading rates (0.02, 0.04, 0.06, 0.08 and 0.10 mm/s) and loading position (ventral and dorsal sides) were determined within a moisture content range of 15.7 %–27.5 % (w.b.) by using a texture analyzer (TA) to investigate mechanical properties for shearing breakage of oat kernel. Complete randomized design was experimented to construct the force–distance curve. In this study, these mechanical properties of oat kernel were expressed as a function of moisture content and loading rate respectively. The result showed that breaking force, energy, strength, hardness and rigidity decreased linearly with the increasing moisture content and increased firstly and decreased then with the increasing loading rate. Deformation had an increasing trend with the increase in moisture content and loading rate. The highest values of breaking force, breaking energy, strength, hardness and rigidity were obtained at 0.08 mm/s loading rate. Moreover the dorsal side of oat kernel had a better shearing capacity compared with ventral side, which reflected in that breaking force, strength and hardness were great significantly at 95 % confident level when dorsal side was loaded.

Effect of primary processing on the distribution of free and modifiedFusarium mycotoxins in naturally contaminated oats

Oat (Avena sativa L.) ranks seventh in the world cereal production and is considered to be an important source for many valuable components of nutritional and biological importance, i.e. proteins, fats, carbohydrates, fibre, minerals and vitamins. Because of these properties the amount of oat used for human consumption has increased progressively during the last years. Unfortunately, the quality of this grain crop is often compromised by mycotoxin contamination, which is relatively ubiquitous despite efforts to control the problem. Therefore, it is important to investigate the distribution pattern of mycotoxins and their conjugated derivatives in contaminated oat grains. For this purpose we have developed a state-of-the-art multi-mycotoxin high-resolution mass spectrometry method and analysed oat samples for their content of the most important mycotoxins commonly occurring in Norwegian cereal grain. Quantitative mapping of selectedFusarium free and modified mycotoxins was performed in fractions collected during processing trials consisting of dehulling and sequential pearling. Both the derivative free mycotoxins and their metabolites were mainly present in the hulls compared to the oat kernel, thus dehulling resulted in a significant reduction of the total mycotoxin load, followed by some further reduction by pearling. Furthermore, free and modified mycotoxins were unevenly distributed in relation to each other throughout the grain fractions, showing a shift towards glucosidated forms, such as deoxynivalenol-3-glucoside and HT-2-3-glucoside in the oat kernel, which highlights potential food safety concerns associated within planta modified mycotoxins.

Processing of oats and the impact of processing operations on nutrition and health benefits.

Oats are a uniquely nutritious food as they contain an excellent lipid profile and high amounts of soluble fibre. However, an oat kernel is largely non-digestible and thus must be utilised in milled form to reap its nutritional benefits. Milling is made up of numerous steps, the most important being dehulling to expose the digestible groat, heat processing to inactivate enzymes that cause rancidity, and cutting, rolling or grinding to convert the groat into a product that can be used directly in oatmeal or can be used as a food ingredient in products such as bread, ready-to-eat breakfast cereals and snack bars. Oats can also be processed into oat bran and fibre to obtain high-fibre-containing fractions that can be used in a variety of food products.

Detailed Composition Analyses of Diverse Oat Genotype Kernels Grown in Different Environments in North Dakota

ABSTRACTNutritional composition of oat kernels from 18 genotypes grown in six environments in North Dakota, U.S.A., was analyzed by chemical means. Of the macronutrients, mean starch concentration was 56.5%, protein was 18.1%, oil was 7.9%, neutral detergent fiber (insoluble fiber) was 6.0%, β‐glucan (soluble fiber) was 5.2%, ash was 1.9%, and soluble carbohydrate was 0.6%. These add up to 96.2%, which appears to account for most of the mass of the oat kernel. Protein amino acid analysis indicated 4.5% lysine and 1.8% methionine. Free amino acid analysis indicated 1,129 μg of asparagine per gram of flour. The 18:1 and 18:2 fatty acids were the most abundant in oat lipids. Mean micronutrient concentrations in oat kernels included potassium (3,419 ppm), magnesium (1,416 ppm), calcium (441 ppm), iron (52 ppm), zinc (26 ppm), and selenium (0.38 ppm). Analysis of variance indicated significant genotypic and environmental variation, as well as significant genotype × environmental interaction for most of the nutritional components. In general, protein was higher in drier, hotter environments, whereas oil, β‐glucan, and starch were higher in wetter, cooler environments. The results provide a unique database of a collection of compositional components for specific oat genotypes in diverse environments.

Microstructure and nutrient composition of hairless canary seed and its potential as a blending flour for food use

Canary seed is a true cereal with unique composition. The current study employed light and fluorescence microscopy to visualise starch, protein, phenolics and phytate in hairless canary seed (CDC Maria), a cultivar developed potentially for food use. Macronutrients, minerals and vitamins were evaluated in the developed cultivar and compared with a commercial hairy canary seed, cv. Keet. A control common wheat, cv. Katepwa, was grown adjacent to the canary seed varieties. The compositions of the two canary seed varieties were found to be similar with an average of 55.8 g/100 g of starch, 23.7% g/100 g of protein, 7.9% of crude fat, 7.3 g/100 g of total dietary fibre, 1.8 g/100 g of soluble sugar and 2.3 g/100 g of total ash in the whole grain. Regardless of the milling fraction (whole grain flour, white flour or bran), canary seed had more protein and crude fat and less starch, total dietary fibre and soluble sugar than had wheat. It also had higher concentrations of several minerals and vitamins than did wheat. The structure of the canary seed grain exhibited compound starch granules and protein bodies embedded in a protein matrix similar to that of the oat kernel. Baking tests showed that bread made with 100% hairless canary seed flour was significantly lower in loaf volume and crust and crumb colour than was wheat bread. However, bread with loaf volume, specific volume and crust colour comparable to those of the bread control was achieved by using up to 25% of hairless canary seed or 15% of roasted canary seed flour, thus demonstrating its potential for food applications.

Effects of high-temperature heat treatment of oat kernel on viscosity properties of oat flour.

Effects of high-temperature heat treatment of oat kernel on viscosity properties of oat flour.

Relationship between kernel size and shape and lipase activity of naked oat before and after pearling treatment

AbstractBACKGROUND: In China, some oat‐processing companies use pearling treatment to remove part of kernel lipase activity before further deactivation such as infrared roasting. Kernel size and shape are important physical properties of oat kernels. However, there are no reports concerning the change of oat kernel size and shape and lipase activity during pearling treatment.RESULTS: In this research, we tested lipase activity in the kernels of four different oat varieties and we studied the relationship between kernel size and shape and lipase activity. The effect of pearling treatment on oat lipase activity was also examined. A TM‐05C Satake mill was employed to pearl oat samples, with different pearling times ranging from 0 to 45 s at 5 s intervals. The oat lipase activity, lipid content and kernel shape and size after the pearling treatment were tested. Results showed that not only oat variety but also kernel size and shape had marked effects on lipase activity. Pearling treatment could significantly reduce lipase activity. During pearling treatment, small changes in kernel size and shape could cause a dramatic decline in lipase activity.CONCLUSIONS: Pearling treatment could be an effective pretreatment for further deactivation treatment of oats. Copyright © 2009 Society of Chemical Industry

Theoretical and Empirical Relationships Between Oat Test Weight and Groat Proportion

ABSTRACTTest weight and groat proportion are two very important quality characteristics of oat grain. In this study, we pose the hypothesis that these two characteristics are related through characteristics of grain density. Test weight is defined as the product of kernel density and packing proportion. Groat proportion, in theory, is the ratio of the groat mass to the kernel mass. We present two theoretical constructions expressing test weight in terms of groat proportion, packing proportion and kernel density components. To test these, we have applied measurements of test weight, groat proportion, kernel density components, and packing proportion of 18 oat cultivars grown at six environments. Whereas the groat proportion alone accounted for only 34% of the variation in test weight, our theoretical constructions that included groat proportion could account for ≤82% of variation in test weight. Also, we present previously undescribed variation in oat kernel density components across genotypes and environments. Although the kernel density alone could account for most of the variation in test weight across genotypes, packing proportion appeared to be more important in describing variation in test weight of a genotype across different environments. We observed significant variation in both groat and hull density which, together with groat proportion, described most of the variation in kernel density.

Trichome numbers in naked-oat cultivars

SUMMARYThe oat kernel, caryopsis or groat, is generally covered with fine silky hairs termed trichomes. The trichomes of naked oat are partly lost during threshing and handling of grains when the lemma and palea are removed and the surface of the grain is exposed. Trichomes can cause itchiness and more serious reactions in those handling the grains. Trichomes also accumulate and form fine dust and can block up machinery. Trichomes are clearly problematic and growers of naked oat are eager to have oat cultivars with reduced numbers of trichomes. Experiments compared the differences in trichome numbers of naked-oat cultivars and threshing settings. The cultivars differed considerably in pubescence. Cultivars Lisbeth and NK 00117 had most trichomes and cv. Bullion the fewest. Completely bare or polished grains were not observed. Pubescence was not associated with grain weight or test weight. However, grains from the lowermost spikelets of the panicle had fewer trichomes than those from the uppermost spikelets. For cv. Bullion, some threshing settings, including increased cylinder speed, slightly increased grain polishing such that grains had some areas completely free of trichomes. Reduction of the concave clearance in the combine harvester had a similar effect. However, threshing settings did not affect the trichomes of cv. Lisbeth. Adjusting threshing machinery settings was generally not an efficient means of solving the problems associated with naked-oat trichomes, but cultivar differences existed and further efforts in breeding to reduce trichome numbers are required.

Enzymatic digestion and in vitro fermentation of oat fractions by human lactobacillus strains

Oats have received considerable interest for their high content of soluble and insoluble fibre and for their high fermentability with probiotic lactic acid bacteria. However, these fibres are not uniformly distributed within the oat kernel. Oat fractions were obtained by debranning technology and the pearlings generated were hydrolysed in vitro using gastric and pancreatic enzymes of human origin. The indigestible part was separated using dialysis and the soluble and insoluble fibre was obtained by precipitation with ethanol. The suspensions were later fermented by lactic acid bacteria of human origin to evaluate the prebiotic potential of the oat fractions and flours in vitro. Of the three probiotic strains tested, Lactobacillus plantarum showed in all media a higher maximum growth. The 1–3% pearling oat sample has higher fermentation ability and the indigestible components of this fraction showed the highest growth of lactobacilli.

Size Distributions of Different Orders of Kernels within the Oat Spikelet

Oat kernel size uniformity is of interest to the oat milling industry because kernel size is important in the dehulling process. Previous studies indicated that oat kernel size distributions are bimodal. In this study oat spikelets were dissected into primary, secondary, and tertiary kernels and kernel size distributions were determined for each of these kernel orders by digital image analysis. Spikelets with two kernels are the most abundant, and their primary and secondary kernels have distinctly different size distributions. These two kernel spikelets appear to be responsible for the bimodal distribution observed among oat kernels. Primary kernels from single kernel spikelets and primary, secondary, and tertiary kernels from triple kernel spikelets all had different mean sizes and distributions. These kernels appeared to contribute to deviations from bimodal distributions. Thus, data presented provide direct definitive evidence that the non‐Gaussian distributions observed for oat kernel sizes are derived from the combination of subpopulations from each of the different orders of kernels from within the spikelet. Sieving analysis of kernel types indicated that for the samples analyzed here, secondary kernels from two kernel spikelets and tertiary kernels from three kernel spikelets appear to contribute equally to undersized kernels under 2 mm in width. Thus, from a kernel size prospective, no advantage can be attributed to the elimination of three kernel spikelets by selective breeding.

Kernel Size Variation in Naked Oat

ABSTRACTKernel size in naked oat (Avena sativa L.) is of interest because of the importance of groat size in determining flake size in “old fashioned” style oat flakes. Here we compared naked oat kernel size distributions with those of hulled oat (Avena sativa L.). Most hulled oat spikelets have two kernels, where the primary kernel is distinctly larger than the secondary kernel. Although naked oat panicle architecture was similar to that of hulled oat, naked oat had a distinctive multiflorous spikelet architecture that contained from one to six kernels. Because single and double‐kernel spikelets were most abundant in naked oat, the mean kernel number per spikelet did not differ between hulled oat and most naked genotypes. Like hulled oat, naked oat kernel size decreased with increasing kernel order. All hulled oat and most naked genotypes had size distributions departing from normality, but some naked genotypes had normal kernel size distributions. Variances of naked oat kernel size were much smaller than those of hulled genotypes, indicating a greater degree of kernel sizes uniformity in naked genotypes. However, the increased variation in the hulled oat kernel size appeared to be due to the presence of the hull and hulled oat groats had about the same size variation as did naked oat groats.

Effects of relative time of emergence and density of wild oat (Avena fatua L.) on oat quality

Selective control of wild oat with herbicides is not possible in oat (Avena sativa L.) crops and, consequently, the high quality that is imperative to market success is continually jeopardized. Field experiments were conducted to determine the effects of relative time of emergence and density of wild oat on oat kernel size and weight. Thousand-kernel weight and percentage plump kernels were generally reduced, and percentage thin kernels were generally increased with increasing wild oat densities and earlier wild oat emergence. However, reductions were generally small and occurred only at the highest wild oat densities, which are not commonly observed in commercial fields. These findings suggest that oat growers should not control wild oat based on perceived reductions in oat physical grain quality. Key words: Competition, emergence, physical grain quality, test weight, 1000-kernel weight

A bimodal model for oat kernel size distributions

Oat kernel size distributions are important to the oat milling industry because size separation of kernels is routine in oat milling. Dehuller rotor speeds are set in order to deliver the optimal mechanical stress to different kernel size streams for dehulling. In this study, size distributions were evaluated by digital image analysis in 10 cultivars grown in eight environments. Observed distributions were compared with quality characteristics and with panicle characteristics and spikelet type frequencies. Size distributions within samples, as evaluated from individual kernel image areas, tended to depart from normal distributions and graphical depictions of data frequently resembled bimodal populations. A statistical test to compare a bimodal distribution with a normal distribution indicated that a bimodal model was more effective at describing the distributions. Panicle analysis indicated that two-kernel spikelets were the most abundant spikelet type found. Because two-kernel spikelets consist of one larger kernel and one smaller kernel, it is likely that the root of the bimodal distribution can be attributed to these spikelets. Although some departures from the mixture of two normal distributions can be attributed to the occurrence of one- and three-kernel spikelets, many of these departures must be attributed to other sources of variation in oat kernel size. Key words: Oats, panicle, kernel size, spikelets

Evaluation of Oat Kernel Size Uniformity

Oat (Avena sativa L.) kernel size uniformity is important to the oat milling industry because oat‐processing mills separate oats according to size to optimize dehulling efficiency. In this study, we compared two different approaches for analyzing oat kernel size uniformity, namely the sequential sieving of oat samples with a gradient of slotted sieve sizes and digital image analysis. Image analysis of size fractions provided evidence that sieving separated oat kernels according to their depth, whereas, digital image analysis measured kernel length and width, and derived a measure of the area of the oat kernel image. Samples identified by sieving with superior uniformity were those with greater proportions of large kernels. Histograms of oat kernel sizes derived from digital image analysis suggested oat kernel sizes were (within a genotype and location) composed of bimodal populations. A new statistical analysis allowed for the derivation of means and variances of each of these subpopulations, the numerical balance between the two subpopulations, and the extent of bimodality. Oat samples with lower levels of bimodality tended to be of higher test weight and groat percentage and thus, of better milling quality. Both methods appear satisfactory for evaluating oat kernel size uniformity, although the sequential sieving method is likely to be more useful to breeding programs because of its relative technical ease and simplicity.