Effect of wheat pearling on flour phytase activity, phytic acid, iron, and zinc content

This study examined the effect of wheat pearling on distribution of phytase, phytic acid, iron, and zinc in wheat fractions derived from pearling and roller milling. Grains of four wheat varieties were first pearled by a rice polisher at four levels, i.e. non-pearling (unpearled), 5% pearling (∼5% of the original sample weight was pearled), 10% pearling, and 15% pearling, to produce pearling fines (PF) and pearled grains. The unpearled and pearled grains were then milled through a Bühler MLU-202 laboratory mill, producing eight milling fractions. Results showed that pearling had a positive effect on flour yield, which may be attributed to the reduced yield of coarse bran and the improved yield of first and second reduction fractions. PF had high levels of all the four components, indicating that they could be a valuable source of iron and zinc. In addition, the differences between flours from the pearled and unpearled wheat were slight in terms of these four components.     

Chemical composition and microstructure of milled barley fractions

Wholegrain barley and peeled and pearled barley were roller milled in a Bühler mill, each producing three fractions: endosperm, middlings and bran. These fractions were compared and contrasted with one another and also with milled wheat fractions. Barley endosperm had the highest total starch content in both wholegrain and peeled and pearled barley. Amylose-to-amylopectin ratios (Am:Ap) were higher in barley flours than in wheat flours (P < 0.001). Peeled and pearled barley grain had lower soluble and insoluble fibre contents in all fractions, with wholegrain barley bran in particular having significantly more fibre than that of peeled and pearled barley bran (P < 0.001). The protein contents of the fractions of both barley types did not differ significantly. The endosperm had the lowest protein content, with the bran and middling fractions having double the protein content of the endosperm fraction. The total amino acid concentrations of the fractions followed a similar pattern, the total amino acid concentrations being lower in the endosperm fractions than in the bran and in the middlings fractions. These findings suggest that both types of barley fractions differed essentially from those of wheat. Pearling has a greater effect on the middlings and bran fractions than on the endosperm. The majority of these differences may not be significant enough to impact on the baking qualities of breads made using these fractions.     

Dry Fractionation Methods to Produce Barley Meals Varying in Protein, Beta-Glucan, and Starch Contents

ABSTRACT:  Barley contains several valuable nutrients including beta-glucan (BG), protein, and starch. Each has additional value when concentrated. Dehulled and hulless barleys were sequentially pearled for 1 to 6 cycles, each with 8% removal. The 6 pearled kernels and the initial kernel were subjected to impact or abrasive milling, followed by sieving with a series of U.S. standard sieves. Results of pearling fines show that protein was most concentrated in the outer area, and decreased all the way toward the core area (near 100% surface removal). Starch showed an opposite trend. BG followed the starch trend, but reached a peak at about 60% surface removal. Upon milling and sieving of kernel samples, genotype and particle size had significant effects on nutrient contents in sieved fractions. The pearling cycle had significant effects on protein and starch contents but little effect on BG content, while the milling method had significant effects on protein and BG contents but little on starch content. Abrasive milling produced sieved fractions with much higher variation in protein content than impact milling, but the opposite effect was observed for shifting BG content. Mass frequency influenced more on recovery rates of nutrients than their concentrations in individual fractions. When the recovery rate was also taken into consideration, pearling alone was found to be the most effective way to enrich protein in barley kernels. However, a combination of pearling with the method of milling and sieving was needed for maximally shifting BG and starch contents.
PRACTICAL APPLICATIONS: Although dry fractionation is the method of choice for separating barley into fractions with varying levels of protein, BG, and/or starch, selection of a specific single or combined method is needed for achieving maximum shifts of a particular nutrient. Such information is significant to those who use dry fractionation methods to enrich protein, BG, and/or starch.     

Localization of phenolic acids and antioxidant activity in sorghum kernels

White and red of sorghum grains were sequentially pearled into 11 pearling fines and the corresponding 11 pearled kernels to study the localization of phenolic acids within sorghum grains. All fractions were analyzed for phenolic acids content by HPLC and antioxidant capacity by FRAP assays. Four phenolic acids identified in all fractions were caffeic, p-coumaric, ferulic, and sinapic acids. Data showed that the distribution of phenolic acids and antioxidant capacity in two sorghum genotypes was heterogeneous. Around 60% of the phenolic acids and the antioxidant capacity were recovered in the initial three pearling fine fractions that constituted about 20% surface removal. The concentrations of the phenolic acids decreased significantly with sequential pearling. Significant correlation between total phenolic acids and antioxidant capacity was observed with all fractions except for the first pearling fines from the red sorghum.     

大米淀粉物化特性与糊化曲线的相关性研究

以不同品种的大米淀粉为原料，采用快速黏度分析仪（RVA）研究不同品种大米淀粉的糊化曲线的差异，碘兰值和酶解力等物化特性对糊化特性的影响。结果表明，不同品种大米淀粉的碘兰值、酶解力存在差异，以籼米淀粉的碘兰值最大，其次是粳米淀粉和糯米淀粉。粳米淀粉和糯米淀粉酶解力相对较大。糊化温度、最终黏度、最低黏度、回升值与碘兰值均呈不同程度的正相关。峰值黏度、最低黏度、最终黏度、回升值、糊化温度与酶解力呈不同程度的负相关。采用碘兰值、酶解力的指数模型描述大米淀粉的糊化特性可达到很高的拟合精度。     

稻谷储存过程中品质变化研究

通过对3个籼稻和3个粳稻在两种不同温度条件下储存的品质变化研究,探索稻谷储存品质产生的内在原因.结果表明:不同类型的稻谷在储存过程中的品质变化不同,与籼稻相比,粳稻部分指标对高温更加敏感;高温储藏比低温储藏导致稻谷品质劣变的速率大;稻谷糊化特性发生明显的变化,主要表现为峰值黏度,最低黏度,最终黏度和回生值都增大,而衰减值下降;利用物性仪对大米蒸煮后的质构特性测定表明,蒸煮米饭黏度减小、硬度增大、黏/硬减小;蒸煮品尝值与最低黏度、最终黏度极显著负相关,初步认为其可以作为初始判定稻谷陈化指标,但是对稻谷劣变程度的量化还需要进一步深入研究;利用SEM研究稻谷籽粒断面结构,显示:新鲜稻谷的胚乳细胞呈现非裸露状态,比较平滑,复粒淀粉被较厚的造体膜掩盖着,高温储藏下,稻谷横断面越来越粗糙,配入细胞内的淀粉粒裸露清晰可见,复粒淀粉的淀粉粒表面膜翘起并爆开.     

Milling behavior of hulled barley and its thermal and pasting properties

Eight commonly grown Indian hulled barley cultivars were studied for their dehusking, pearling, physico-chemical, β-glucan, pasting and thermal behavior. Milling of the hulled barley at 14% moisture significantly lowered the dehusking and pearling time as compared to milling at 10% moisture content. The extraction rate ranged from 55.05% to 62.35% and significantly (p < 0.05) differed among the cultivars. Particle size distribution of flours was significantly different among the cultivars with flour from RD-2552 and RD-2035 cultivars having the most even particle size distribution. The colour difference (ΔE) was not significantly different among cultivars. The extractable β-glucan content varied from 1.93% to 3.81% among the cultivars and was highest in PL-172. The final pasting viscosity was significantly different among cultivars while the pasting temperature did not vary significantly. The enthalpy (ΔH) of gelatinization of barley flour varied from 4.45 to 7.08 J/g and gelatinization temperature (T_p) varied from 64.23 to 66.26 °C.     

Tocol Composition and Supercritical Carbon Dioxide Extraction of Lipids from Barley Pearling Flour

Samples of whole grain and 35% pearling flour of 20 different barley varieties grown in Alberta were analyzed for their lipid contents. Total lipid contents of whole grains were within 1.9% to 3.0% (w/w), whereas those of the 35% pearling flour were 4.3% to 7.9%. Lipids of 35% pearling flour fraction of Tercel barley were extracted using supercritical carbon dioxide (SC‐CO₂) at different pressures (24, 45, and 58 MPa) and temperatures (40 and 60 °C) for 3 h. Lipid recoveries of 73% to 97% were achieved using SC‐CO₂ extraction under different operational conditions. Tocol contents and compositions of whole grain, 35% pearling flour, and SC‐CO₂ extracts were analyzed using HPLC. Tocol content of the whole grain was 53.8 to 124.9 μg/g and that of the pearling flour was 195 to 363 μg/g of flour. The hulless barley varieties were higher in tocols, with waxy, double waxy and Tercel varieties having the highest levels (P < 0.05). The ratios of total tocotrienols to total tocopherols varied within 1.6 to 3.9 range. Tocol concentrations of SC‐CO₂ extract fractions varied from 1171 to 4391 μg/g extract depending on the operational conditions. Barley oil is a good natural source of different tocol isomers rich in tocotrienols.     

糯性普通小麦的籽粒成分和淀粉品质研究

对5个组合的13个糯麦F6（或F5）株系及其亲本的籽粒成分，直链淀粉含量和膨胀势进行测定，以及分析了它们的淀粉糊化过程和糊化参数，比较它们之间的差异。结果表明：糯性小麦籽粒的蛋白质含量，湿面筋含量均高于相应的亲本，而淀粉含量则低于相应的亲本，糯性小麦株系的直链淀粉含量远远低于其亲本；糯麦淀粉的膨胀能力和吸水力大于其亲本；糯麦株系的RVA高峰粘度，低谷粘度，最后粘度，反弹值和峰值时间显著低于其亲本。糯麦株系面粉间的RVA粘度参数值大同小异，讨论了糯性小麦的应用前景。     

Pasting properties of starch and protein in selected cereals and quality of their food products

In an attempt to improve intake of dietary fibre and antioxidants and quality of whole grain products, whole grain meals from barley, millet, rye and sorghum were evaluated individually and in blends with wheat flour in terms of starch pasting properties and protein heat damage, during cycles of heating and cooling in RVA tests. The whole grain meals were blended with either hard or soft wheat flour and processed into bread, cake, cookie or snack products. The products were then evaluated with regard to physical properties and acceptability. Significant differences were observed between cereals in starch peak, breakdown and setback viscosities as well as in protein peak viscosity. The results showed that RVA could be used to help formulate cereal blends with certain pasting properties. Substitution of wheat flour, with 15% of barley, rye, millet or sorghum whole grain, did not have significant detrimental effects on physical properties or acceptability of pita bread. Additionally, replacement of wheat flour with up to 30% of barley, rye, millet or sorghum whole grain meal had no significant effects on quality of cakes or cookies. A multigrain snack-like food was also developed as a healthy product and was highly acceptable in a sensory test. The developed product would help enhance consumption of whole grain foods, resulting in improved intake of fibre and health-enhancing components.     

Comparison of Rice Flour Pasting Properties using Brabender Viscoamylograph and Rapid Visco Analyser for Evaluating Cooked Rice Texture

Pasting properties of ten Thai rice varieties, with amylose contents in the range of 16 to 33% and stored at 10, 30 and 40 °C for six months were compared using the Brabender Viscoamylograph (VAG) and the Rapid Visco Analyser (RVA) for evaluating the texture of cooked rice. Linear correlations between pasting temperature and viscosity parameters based on RVA showed a different pattern than those based on VAG with high negative correlation coefficients between the peak and breakdown viscosities. Both RVA and VAG indicated peak viscosity to be positively correlated with breakdown viscosity, and negatively with the setback viscosity. Setback and consistency viscosities correlated with each other in both instruments but indicating a negative correlation with breakdown viscosity in VAG only. Pasting temperature determined by VAG and RVA did not show good correlations for rice sample stored at different temperatures neither for individual nor for combined data. Only peak, breakdown and setback viscosities showed significant correlations in the overall data (r > 0.496). The VAG measurements performed better than the RVA in the development of predictive models for evaluating the hardness and adhesiveness of cooked rice based on instrumental texture profile analysis. The springiness and cohesiveness of cooked rice could not be estimated from the pasting properties of rice flour determined by both VAG and RVA. Results showed that both VAG and RVA could be used for evaluating the texture of cooked rice despite the differences in the measurements of the pasting properties of milled rice flours.     

Enrichment of Antioxidant Capacity and Vitamin E in Pita Made from Barley

This study aimed to enhance total antioxidant and vitamin E content of pita bread, by replacing 50% of the standard baker's flour with flours milled from covered (WI2585 and Harrington) or hulless (Finniss) barley genotypes, previously shown to have high antioxidant and vitamin E levels at harvest. Pita breads were made from either 100% baker's flour (control) or 50% malt flour, whole‐grain flour, or flour from barley grains pearled at 10%, 15%, and 20% grain weight. Antioxidant capacity and vitamin E content of flours and pitas were determined by their ability to scavenge 2,2‐diphenyl‐1‐picrylhydrazyl radicals and high performance liquid chromatography, respectively. The physical and sensory properties of the pitas were also assessed. All pitas made from either whole grain or pearled barley flour had a higher antioxidant capacity and most also had higher vitamin E content than standard pita. The antioxidant and vitamin E levels were reduced in pearled compared to whole grains, however the extent of that reduction varied among genotypes. The greatest antioxidant and vitamin E levels were found in pita made from malt flour or Finniss whole grain flour. Furthermore, sensory analysis suggested these pitas were acceptable to consumers and retained similar physical and sensory properties to those in the control pita.     

不同粒径小米粉对面团流变特性及馒头质构特性的影响

为研究小米粉添加对面团流变特性和馒头制品质构特性的影响,分别选取不同粒径的粳性和糯性小米粉,利用损伤淀粉测定仪、快速黏度分析仪等对不同小米粉的损伤淀粉含量和糊化特性进行分析,通过流变仪测定小米面团的流变学特性,结合扫描电镜观察小米面团微观结构变化,并利用质构仪测定小米馒头的质构特性。结果表明：随着小米粉粒径的减小,多数品种小米粉（除冀谷39和汇华金米）损伤淀粉的碘吸收率增加;受直支比的影响,相同目数下,粳性小米粉的峰值黏度、谷值黏度、最终黏度和回生值较糯性小米粉大。流变学研究表明,除汇华金米和冀谷39,储能模量与损耗模量随角频率增加总体上升。扫描电镜观察发现小米粉的添加使面团结构更加松散。小米粉的添加会对馒头质构性质中硬度、咀嚼性和弹性等有一定程度的负面影响。主成分分析表明馒头咀嚼性、损伤淀粉、峰值黏度、谷值黏度、最终黏度、崩解值和回生值可作为区分粳糯品种和馒头品质特征的指标。     

RVA study of mixtures of wheat flour and potato starches with different phosphorus contents

A rapid visco analysis (RVA) system was used to study the pasting properties of mixtures of wheat flour and potato starches with high phosphorus (HPS), medium phosphorus (MPS) and low phosphorus (LPS) contents, different granule sizes and different amylose contents. The peak viscosities, trough and breakdown, final viscosities, setback viscosities and peak times of control potato starches were found to be higher than those of wheat flour. The peak viscosities were increased significantly with increase of potato starches in the mixtures. Thus, the peak times decreased with increase of potato starch in the mixtures. The breakdown viscosities increased significantly with increase of potato starches in the mixtures and the values were found to be higher in HPS-wheat, followed by MPS-wheat and LPS-wheat mixtures. The final viscosities of HPS-wheat mixtures were highest, followed by MPS-wheat and LPS-wheat mixtures. The setback viscosities of LPS-wheat were significantly higher than those of MPS-wheat and HPS-wheat mixtures at 30 to 50% potato.     

Pasting properties of Angelica dahurica starches in the presence of NaCl,Na2CO3, NaOH,glucose, fructose and sucrose

The pasting viscosities of starches from Angelica dahurica (three cultivars named Chuan Baizhi, Yu Baizhi and Qi Baizhi in Chinese, respectively), in the presence of NaCl, Na₂CO₃, NaOH, glucose, fructose and sucrose were determined with a rapid visco analyser. The pasting peak, trough or final viscosities and the pasting temperatures (Pt) of Baizhi starches increased with NaCl concentration increased from 0 to 3.0%. The peak viscosities of Baizhi starches increased at 0.2% Na₂CO₃ concentration and then decreased with Na₂CO₃ concentration up to 0.8%. The trough and final viscosities and the Pt decreased with Na₂CO₃ concentration up to 0.8%. The peak viscosities increased in 0.1%, but decreased in 0.2% NaOH concentration. The trough and final viscosities and the Pt decreased in the presence of NaOH. With the concentration of sugar (glucose, fructose and sucrose) increased from 0 to 20%, the pasting peak, trough and final viscosities of these starches increased significantly. For the same Baizhi starch, the elevation of peak viscosity was the most significant when fructose was added, and the elevation of final viscosity was the greatest when sucrose was added.     

不同筋力小麦品种的搅拌值及其它淀粉糊化特性指标_注

以 5个小麦品种为材料 ,利用快速粘度分析仪 (RVA)研究了不同筋力品种间搅拌值的差异及搅拌值与其它淀粉糊化特性指标的关系。结果表明 ,不同品种间搅拌值有一定差异 ,酶浓度对搅拌值有显著影响。搅拌值与面团筋力无一致性 ,与糊化温度、糊化时间相关不显著 ,但是与高峰粘度、低谷粘度、粘度破损值、最终粘度以及回冷值等 5项淀粉糊化指标显著正相关。同时求出了这 5项淀粉糊化指标依搅拌值变化的回归方程。     

蛀蚀害虫侵害后小麦粗淀粉含量及其糊化特性变化

为探讨蛀食性害虫玉米象、米象侵害后小麦粗淀粉含量和全麦粉糊化特性的变化,选用河南产储藏3年的商品小麦为材料,按不同虫种分组,设定不同的虫口密度和侵害时间,检测害虫感染后小麦粗淀粉含量和全麦粉的糊化特性。结果表明:玉米象和米象不同程度感染后小麦粗淀粉含量总体呈下降趋势;无论是同一虫口密度随着蛀蚀时间的延长,还是同一蛀蚀时间下随虫口密度增加,其感染后的全麦粉峰值黏度、最低黏度、最终黏度、衰减值和回生值均呈下降趋势;糊化温度呈上升趋势,峰值时间基本无变化;粗淀粉含量与峰值黏度、最低黏度、最终黏度、衰减值和回生值均存在极显著正相关,与糊化温度呈极显著负相关,与峰值时间无相关性。     

Changes in kernel properties,in situ gelatinization,and physicochemical properties of waxy rice with inhibition of starch branching enzyme during cooking

The kernel properties, gelatinisation and physicochemical properties of rice were investigated in a waxy rice Guang-ling-xiang-nuo (GLXN) and its transgenic line GLXN-RNAi with inhibition of starch branching enzyme I/IIb. The volume swelling, water content and leached material of cooked kernels increased with increasing cooking time, but they were lower in GLXN-RNAi than in GLXN. The kernels of GLXN-RNAi were more difficultly gelatinised and disrupted than those of GLXN during cooking. The starch in the exterior of GLXN-RNAi endosperm was not completely gelatinised. The C_A-type starch of GLXN-RNAi was more resistant to cooking than A-type starch of GLXN. The cooked kernels of GLXN-RNAi had lower rapidly digestible starch and greater slowly digestible starch than those of GLXN. Brown rice flour had higher peak, hot, final and setback viscosities and lower breakdown viscosity in GLXN than GLXN-RNAi. These results indicated that GLXN-RNAi kernels exhibited great potential in applications as health foods.     

Textural and pasting properties of potatoes (Solanum tuberosum L.) as affected by storage temperature

Fresh tubers from five potato (Solanum tuberosum L.) cultivars were stored at different temperatures (4, 8, 12, 16 and 20 °C) and 80–90% relative humidity for 18 weeks after harvest to examine the effect of storage temperature on their textural and pasting properties. Texture profile analysis was performed on raw and cooked potatoes using an Instron universal testing machine to measure textural parameters such as fracturability, hardness, cohesiveness, adhesiveness and springiness. Both raw and cooked potato tubers showed a considerable reduction in all textural parameters upon storage, irrespective of the storage temperature employed. Raw potatoes showed a decrease in fracturability and hardness with increasing storage temperature, whereas their cooked counterparts showed the opposite trend. The extent of change in the textural properties of both raw and cooked potatoes also varied among the different cultivars. Fresh and stored tubers from all cultivars were freeze‐dried, ground into flours and analysed for amylose content and pasting properties. The amylose content of flours prepared from potatoes stored at 4 and 8 °C was observed to be considerably lower than that of flours prepared from potatoes stored at 16 and 20 °C. Pasting characteristics such as peak viscosity, setback and final viscosity increased with increasing storage temperature, while the reverse was observed for pasting temperature, when studied using a rapid visco analyser. Breakdown in viscosity of the flour pastes from all cultivars was considerably reduced during storage, irrespective of the storage temperature employed. Copyright © 2006 Society of Chemical Industry     

面粉糊化特性与鲜湿及煮后面条质构特性关系

为了研究小麦面粉糊化特性对于面条加工品质和食用品质的影响，选用了黄淮冬麦区（陕西省、河南省）的25个主栽小麦品种及2个专用面粉（新疆拉争子粉、日本乌东专用粉）为材料，研究了面粉糊化特性与鲜面条加工特性（面条长度、面条厚度、鲜面条最大拉伸阻力、拉伸长度和拉伸能量）、面条煮后品质（TPA测试、表面韧性、剪切韧性和压缩特性）的关系。研究结果认为对于鲜面条加工而言，低谷粘度、最终粘度、回生值、破损值、峰值时间和峰值温度贡献较大；对于煮后面条质构而言，最终粘度、回生值、破损值、峰值时间和峰值温度更为重要。总之，小麦品种的最终粘度、回生值、破损值对于面条加工和食用品质影响很大。