Variation in Oat Groats Due to Variety, Storage and Heat Treatment. I: Phenolic Compounds

Low molecular weight phenolic compounds present in heat processed oats (Avena sativaL) were analysed. The oat grains were of three varieties (Kapp, Mustang and Svea), stored at different relative humidities (30, 55 or 80%) and periods (3·5 or 15·5 months) and processed with or without hulls. Eleven UV-absorbing compounds detected by High Performance Liquid Chromatography were subjected to univariate and multivariate statistical analysis. The selected compounds included caffeic acid,p-coumaric acid, ferulic acid, vanillic acid,p-hydroxybenzaldehyde, vanillin, coniferyl alcohol, three avenanthramides and one unidentified substance. The levels of vanillic acid, vanillin and, especially,p-coumaric acid,p-hydroxybenzaldehyde and coniferyl alcohol increased significantly in samples processed with hulls, but not in samples processed without hulls. Ferulic acid increased in both processes, while caffeic acid and the avenanthramides were found to decrease during processing. Storage of unprocessed samples for 1 year generally increased the levels of phenolic acids and aldehydes. For the phenolic acids (except ferulic acid), this increase was most pronounced after storage at high relative humidity (80%). The avenanthramides were present at their highest levels in Mustang, caffeic acid in Svea and Mustang, the unidentified compound in Svea, while all the other compounds studied were present predominantly in the variety Kapp.     

Prediction of Sensorial Properties (Color and Taste) of Amala,a Paste From Yam Chips Flour of West Africa,Through Flour Biochemical Properties

Color and taste are permanent features of amala, a traditional thick paste obtained from yam chips flour. To assess these attributes, 23 yam chips presenting various quality attributes were processed. The sensory attributes of their derived amala were determined and some biochemical characteristics of yam flours measured. A panel defined five main taste attributes for amala: sweetness, bitterness, acidity, fermented, and roasted tastes. Amala color was measured instrumentally and sensory scores were highly correlated with flour biochemical analyses; amala sweetness was positively correlated with glucose and fructose content of the flour, whereas amala acidity and fermented taste were linked to organic acids and lactic acid contents of flour, respectively. In addition, darkness, bitterness, and roasted tastes of amala could be tightly predicted by multiple regression analysis from phenolic compound and glucose–fructose contents. Phenolic content of yam flour plays thus a key role on sensorial quality of amala. However, polyphenol oxidase and peroxidase activities were almost null in yam flours and their specific role on yam flour phenolic content needs to be clarified.     

Quantities of phenolic compounds and their impacts on the perceived flavour attributes of rye grain

The use of whole grain rye products, beneficial to one's health, could be substantially extended if the typical intensively bitter flavour of rye could be modified without losing the characteristic rye-like flavour. The aim of the study was to evaluate the contribution of non-volatile phenolic compounds on the perceived flavour. Rye grain was milled into five milling fractions. The levels of phenolic compounds, i.e. the phenolic acids, alkylresorcinols and lignans, of the fractions were analysed and related statistically to sensory flavour profiles by partial least-squares (PLS) regression. The non-bound (free) phenolic acids are suggested to be most flavour-active. Cereal and intense flavour and aftertaste were related to vanillic and veratric acids, alkylresorcinol C_23:0, and other lignans except for pinoresinol. The perceived bitterness of the bran fractions was suggested to result from pinoresinol and syringic acid. Sinapic and ferulic acids, alkylresorcinols, except for alkylresorcinol C_23:0, and syringaresinol seemed to cause the germ-like flavour. Phenolic acids, alkylresorcinols and lignans distributed with a similar pattern in the rye grain as the flavour attributes: the phenolic compounds were clearly located in the outer bran fractions being intense in flavour, but not in the mild-tasting inner layers of the grain.     

小麦寡核苷酸探针套用于燕麦染色体鉴定

基于寡核苷酸探针套的荧光原位杂交(FISH)技术简单高效,通过FISH信号分析,可以对不同物种染色体组成进行分析。本研究利用AFA-3、AFA-4、pAs1-1、pAs1-3、pAs1-4、pAs1-6、pSc119.2-1和(GAA)₁₀等8个探针组成的小麦寡核苷酸探针套,对不同倍性的燕麦品种进行荧光原位杂交。结果表明,小麦的寡核苷酸探针套在燕麦大部分染色体上可以产生清晰的杂交信号,能够区分燕麦大部分染色体,说明燕麦与小麦存在一定程度相似的重复序列,可为燕麦染色体的精准鉴定和分型提供了新的思路。     

Effect of heat treatment on the flavor of oat flakes

In order to assess the effect of heat treatment procedure on the flavor and volatile compounds of oats, raw oats, kiln and dried oats, dehulled oats and oat flakes were analysed. A sensory profile method was used to monitor changes in flavor. It changed from hay-like for raw oats into nutty, bread-like for oat flakes. Headspace solid phase microextraction (SPME) and solvent assisted flavor evaporation (SAFE) techniques were applied for isolation of aroma compounds. The most abundant compound in headspace was hexanal – its concentration varied from 176 to 1671 μg/kg depending on the processing stage. The key aroma compounds of oat flakes identified using gas chromatography – olfactometry and aroma extract dilution analysis (AEDA) were 2-methyl-3-furanthiol with roast/cooked oatmeal flavor together with methional, dimethyl trisulfide, 1-octen-3-ol, 2-methyl-3,5-diethylpyrazine.     

Chemical composition and nutritive value of husked and naked oats grain

11 samples of oats from the 2005 crop of the field experiment carried out in RSD Lipnik were examined. Naked grain oats were represented by a standard Polar cultivar and 5 strains (STH 6102, STH 6856, STH 7146, STH 7256, STH 1692), whereas husked grains were represented by a standard Bohun cultivar and 4 strains (STH 684, STH 688, STH 729, STH 840). The examined naked grain oats differ considerably from husked grain oats in their chemical composition. A statistically significantly higher content of protein (P ≤ 0.05), a higher level of fat (P ≤ 0.01) and a lower value of crude fibre (P ≤ 0.01) were observed in the grains of naked oats compared with the husked grains. The protein of oats is characterised by a favourable amino acid composition of high quality protein which can be confirmed by the EAAI values. The first amino acid limiting the nutritive value of protein was lysine in nearly all oat samples. The characteristic feature of the Polar cultivar was isoleucine deficit. The positive nutritive values for oat grains, in particular those for naked oat grains, make it possible to use them as food for humans and feed for monogastric animals.     

燕麦PRR基因家族鉴定与表达分析

春、夏播燕麦是长日照作物，光周期不敏感燕麦的创制使其在短日照条件下能正常生长发育。PRR基因是光周期途径中重要的昼夜节律调节基因。前期转录组研究表明PRR基因可能与燕麦光周期不敏感性有关。本研究从转录组和全基因组水平对燕麦PRR基因家族进行鉴定、生物信息学分析和表达研究。结果表明，在燕麦转录组和基因组水平分别鉴定到6个和2个PRR基因，均包含REC和CCT结构域；进化分析表明燕麦PRR基因与小麦、大麦、黑麦草和山羊草的亲缘关系较近；燕麦PRR基因启动子区域包含与光响应、生长发育和胁迫相关的顺式作用元件；qRT-PCR分析表明燕麦PRR基因的表达具有节律特征，全生育期过程中AsPRR1和AsPRR2在穗和叶的表达量均呈现由低到高、下降后再升高的双峰趋势，且AsPRR2基因的表达量高于AsPRR1。以上结果说明，AsPRR基因在燕麦光周期途径中发挥负调控作用，其下调表达促进了光周期不敏感性燕麦gp012在短日照条件下开花。本研究为揭示AsPRR基因在燕麦光周期不敏感机制中的作用奠定 了基础。     

Enhancing three phenolic fractions of oats (Avena sativa L.) and their antioxidant activities by solid-state fermentation with Monascus anka and Bacillus subtilis

This work aims to improve phenolic fractions of oats and their antioxidant activities by solid-state fermentation (SSF) combining Monascus anka with Bacillus subtilis. Results revealed that the fermentation system significantly (p < 0.05) increased the total phenolic content (TPC), which was 23-fold over that in unfermented oats. The hydrolytic enzyme activities of α-amylase, β-glucosidase, and cellulase were significantly (r > 0.75, p < 0.05) correlated to the TPC, indicated an important role in the release of phenolic in oats. The proportion of free phenolic fraction in oats was increased from 39.76% to 61.62%, while that of bound phenolic fraction decreased from 42.17% to 22.78%. Moreover, the phenolic compositions of free, conjugated and bound phenolic fractions varied with fermentation. It implied that the phenolic compounds in different forms could be converted and transformed in the SSF system. Meanwhile, the DPPH· and ABTS^·+ scavenging activities of the free and conjugated phenolic fractions in oats became stronger after fermentation. It indicated that the changes of antioxidant activities of phenolic fractions might be closely related to the structural modification by microbial enzymes in the SSF system. Consequently, this study provides a prospect fermentation process for improving the phenolic release and antioxidant activities in oats.     

Development of standard fingerprints of naked oats using chromatography combined with principal component analysis and cluster analysis

Oat samples of different varieties were collected from various habitats for the determination of avenacoside, β-glucan and fatty contents. The variation coefficients of the three components were 12.13%, 20.79% and 22.46%, respectively. Thus, those three indicators cannot represent the information of all samples, and are not suitable for evaluating the quality of oat raw materials and products. Fatty acid profiles were analyzed using gas chromatography combined with principal component analysis (PCA) and cluster analysis. Fourteen leather oat varieties were distinguished through a PCA scores scatterplot. Forty-six naked oat varieties were selected by cluster analysis and eleven characteristic peaks in these naked oats were identified. Finally, accurate fatty acid standard fingerprints of naked oats were constructed. The results of methodological indicated high precision, reproducibility and stability, in line with fingerprint testing requirements. This study fills the knowledge gap for naked oat fingerprint information, expands the grain fatty acid database, and lays the foundations of a grain nutritional liposome identification technology system.     

Molecular characterisation of 36 oat varieties and in vitro assessment of their suitability for coeliacs’ diet

Coeliac disease (CD) is a chronic intolerance to gluten, contained mainly in wheat, rye and barley. The only therapy at present is the lifelong exclusion of gluten from the diet.Whether oats can be considered safe for CD patients has long been debated, and oats have been included among gluten-free ingredients only recently (EU Regulation 41/2009), provided the gluten content does not exceed 20 ppm.The aim of this study was to evaluate the suitability of 36 different oat cultivars for CD patients using biochemical and immunochemical approaches. The cross-reactivity between avenins and gliadins was evaluated by both SDS-PAGE/Immunoblotting and ELISA.The protein pattern of each oat cultivar showed both qualitative and quantitative differences that correlated with different binding affinity for specific anti-gliadin antibodies in immunoblotting. In most oat samples, the content of cross-reactive proteins measured by ELISA was below 20 ppm, but in a few varieties was above 80 ppm.Although the taxonomic and biochemical characteristics of oats allow to conclude that their use could be safe for CD patients, it is essential to select those cultivars having the lowest level of gluten-like proteins.     

Detection of the lunasin peptide in oats (Avena sativa L)

We report the first discovery of lunasin in oats (Avena sativa L). Lunasin is a novel cancer preventive, anti-inflammatory and cholesterol-reducing peptide originally isolated from soy and later found in cereals (barley, rye, wheat, triticale). Lunasin was detected in oats using LC–MS/MS analysis. The chromatograms and mass spectra of lunasin isolated from five oat genotypes were compared with those of the synthetic lunasin peptide. We measured the lunasin content in harvests of two years and found that all tested oat genotypes contained the lunasin peptide. However, we observed genotype-related fluctuations in the lunasin content. Notably, the middle early oat variety ‘Ivory’ contained the highest and the most stable lunasin level at 0.197 ± 0.01 mg per g of grain in year 2010 and 0.195 ± 0.009 mg per g of grain in 2011. We also characterized the selected oat genotypes by measuring the contents of protein, β-glucans, fat, starch and moisture in the grains. However, we did not find correlation between lunasin and protein, and β-glucan content. Lunasin isolated from oat showed similar to the synthetic lunasin antioxidant effects. The detection of lunasin complements a list of bioactive compounds present in oats and strengthens recommendations to use oat products.     

CO2-defatted oats: Solubility,emulsification and foaming properties

Functional properties of conventional oat materials are relatively poor with respect to foam and emulsion formation and stabilization. This is largely due to the poor solubility of oat proteins and the presence of lipids in aqueous extracts of oats. In the experimental part of this study, extracts were prepared from different type oat flours (oat endosperm flour, oat fine flour, CO₂-defatted whole oat flour and CO₂-defatted oat flour) with a buffered aqueous extraction procedure at acidic (pH 4.5 and 6.5) and basic (pH 8.5 and 10.5) regions. The solubility of proteins was the highest at pH 10.5 and NaCl concentration of 2%. Among the extracts, CO₂-oat flour showed improved foaming and emulsifying properties at basic pH values. The presence of 0.1% NaCl resulted in the lowest foam volumes, but the emulsion activity and stability values being the highest. Sucrose addition resulted in increased foam and emulsion stability of suspensions. Heat treatment at 80 °C impaired foam properties, whereas the stability of emulsions increased with the increase in temperature from 20 °C to 80 °C. CO₂-extracted oats can be useful raw materials in beverages and other aqueous applications where protein functionality plays an important role.     

燕麦生产及品种选育技术研究进展

目前,燕麦生产发展潜力巨大,但育种技术较为落后,现代的新型育种方式应用不够成熟。因此,高度重视种质资源的创新和专用型新品种的选育已成为中国今后燕麦育种工作中的重中之重。本文从国内外燕麦生产、贸易情况及发展潜力方面进行研究总结,并对中国燕麦品种选育技术及育种发展方向的相关进展进行综述,以期为中国燕麦产业的发展及新品种的培育提供参考。     

The cocoyam,Xanthosoma sagittifollium,as a potential raw material source for beer brewing

A widely cultivated cocoyam variety,Xanthosoma sagittifollium, was assessed for its suitability for lager beer production, using maltedSorghum vulgare (white variety) for saccharification of the substrate. The three-mash decoction method was used. Results showed that the cocoyam was superior to barley and sorghum as a substrate because of its potentially higher carbohydrate content (71–78%) compared to barley (65%) and sorghum (70–73%). The percentage wort extract was 13.3–14.5° plato compared to 7–12 for barley and 13° for the tuber crop, cassava. The kiln driedXanthosoma sagittifollium gave a dark bager beer with good aroma (68%) and very good flavour (73%) when compared with a commercial lager beer (Monarch) as standard (100%). The alcohol content (4.16% w/v) and the specific gravity (1013) were within the range (4.0–6.4%) and (1011–1019), respectively, specified by the Standard Organization of Nigeria. Although the bitterness value 40 EBU, was higher than the typical range 16–30 EBU, the taste panel indicated this was acceptable. The pH was 4.68 compared with the standard 4.36, while the acidity (as % lactic acid) was 0.36 compared to 0.24 for some commercial products.     

Understanding the role of oat β-glucan in oat-based dough systems

B-glucan is one of the components that differentiate oats from other cereals and that contribute to the health-related value of oats. However, so far oats cannot easily be applied in bread-like products without loss of product quality. Here we have studied how the content and viscosity of oat β-glucan affect the technological properties of oat dough in both a gluten-free and a gluten-containing system. In both systems, increasing the β-glucan concentration resulted in an increase of dough stiffness and in a reduction of dough extensibility. β-glucan negatively impacted the elastic properties that additional wheat gluten conferred to oat dough. This effect was smaller for medium-viscosity β-glucan than for high-viscosity β-glucan. Interestingly, dough made from low β-glucan flour (<2%) had increased gas retention capacity. Overall, the impact of β-glucan on the properties of oat dough systems was governed by concentration and viscosity, with or without additional wheat gluten. Our findings indicate that β-glucan is a key component that determines the rheology of oat-based dough systems and, with that, the technological functionality of oat in dough systems.     

Effects of genotype and environment on avenanthramides and antioxidant activity of oats grown in northwestern China

To investigate the effects of genotype and growing environment on avenanthramides and antioxidant activity of oats, the total phenolic content (TPC), avenanthramide compositions, and antioxidant activity were determined for whole oat from 39 cultivars grown in four locations in northwestern China (Inner Mongolia, Qinghai, Shanxi and Gansu). The results demonstrated that environment (E), genotype (G) and the interaction of these factors (E × G) significantly affected TPC, concentration of avenanthramide 2c (2c, ranged from 6.24 to 136.20 mg kg⁻¹), avenanthramide 2p (2p, 6.07–112.25 mg kg⁻¹), avenanthramide 2f (2f, 7.26–222.77 mg kg⁻¹) and antioxidant activity of oats. The effect of E was considerably greater than that of G or E × G. Based on G plus G × E interaction biplots (GGE biplots) analysis, the four locations in northwestern China can be divided into either two or three regions. Qinghai was determined to be distinct from the other locations. Cultivar Bayou 9 and oats grown in Gansu exhibited the highest TPCs, concentrations of 2c, 2p, 2f and antioxidant activity. The results suggest that oats containing more avenanthramides and exhibiting high levels of antioxidant activity could be obtained by selecting an appropriate genotype and growth location.     

Lipid removal enhances separation of oat grain cell wall material from starch and protein

Effects of lipid removal on the fine milling and air classification processing of oats were studied. Lipid removal by supercritical carbon dioxide (SC-CO₂) extraction enabled concentration of the main components of oats - starch, protein, lipids and cell walls - into specific fractions. Using defatted oats as raw material, the highest β-glucan concentration of the cell wall-enriched fraction was 33.9% as compared to 17.1% without lipid removal. This was probably due to more efficient milling yielding smaller particles, and release of starchy material from cellular structures during milling of defatted oats, resulting in better classification. The removal of lipids also enabled separation of an oat protein concentrate with a protein concentration of 73.0% and a mass yield of 5.0%. A trial with 2310 kg of oat groats showed that the process based on defatting and dry fractionation was also industrially applicable.