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.     

Concentrations of functional lipids in abraded fractions of hulless barley and effect of storage

Hulless barley kernels were sequentially abraded to achieve 4%, 8%, 16%, 24%, 32%, and 40% removal. Abraded fines, kernels, and ground kernels were stored at 35 degrees C and 75% relative humidity for 3 wk. Stored samples were extracted and the levels of oil, free phytosterols, tocopherols (Ts), and tocotrienols (T3s) were analyzed and compared with freshly abraded fractions. The results revealed that oil, sterols, and Ts were concentrated in the outer layers, particularly in the germ layer. In whole kernels, homologues of both Ts and T3s showed the same ranking order in concentrations as alpha > gamma > beta > delta. The homologue composition of Ts remained the same but that of T3s changed across the kernel. The %T3 in total tocols increased in fractions with increasing endosperm tissue. Storage caused no change in oil and Ts but significant changes in sterols and T3s. The changes were differential among T3 isomers, with alpha-T3 decreasing and delta-T3 increasing. The degradation of alpha-T3 was accelerated in fractions with more endosperm tissue. Grinding kernel samples before storage accelerated sterol degradation but had a limited effect on changes of T3s. A 2nd experiment using a different hulless barley line and ambient storage for 6 mo confirmed all the findings except that the changing trend for sterols was inconsistent. These results provide practical information to those who wish to produce a barley fraction enriched with a particular functional lipid and maintain stability of their products.     

The Effects of Damaged Kernel Caused by Combine Harvester Settings on Milled Rice Free Fatty Acid Levels

Milled rice surface oil and free fatty acid (FFA) contents determine rice acceptability to the brewing industry. Both could subsequently contribute to beer off‐flavors and thus compromise milled rice brewing quality. Controlling milled rice FFA by harvesting practices could be important in maintaining brewing quality as some rough rice is damaged by hull removal and/or bran disruption during harvesting. To determine the effect of harvester speed on kernel damage, the long‐grain rice variety Cocodrie was harvested at 3 different combine harvester settings and the percent of damaged kernel (w/w) was measured. Combine harvester cylinder speed had a significant effect on rough rice kernel damage. The percentages of damaged kernels for 550, 850, and 1000 rpm cylinder speeds were 1.2%, 4.0%, and 9.0%, respectively. The FFA level of milled rice with varying amount of damaged kernels was investigated over 6 mo of storage. The faster harvester cylinder speeds resulted with time in significantly greater FFA levels in “as‐harvested” rice. The FFA content of 1000 rpm as‐harvested rice almost reached the 0.1% (w/w) level. The greater the amount of damaged kernel, the greater was the milled rice FFA level, and it was significantly greater than milled rice with no damaged kernels during accelerated storage. The as‐harvested rice with 1000 rpm had the highest FFA level, followed by 850 and 500 rpm.     

Effects of seeding rate, nitrogen rate and cultivar on barley malt quality

BACKGROUND: Crop management tools have been shown to affect barley kernel size and grain protein content, but the direct effect on malt quality is not well understood. The present study investigated the effect of seeding rate, nitrogen fertilisation and cultivar on malt quality. RESULTS: Higher seeding rates produced barley with less grain protein and smaller, more uniformly sized kernels. The small, uniformly sized kernels modified more completely, leading to malt with higher extract and lower wort β‐glucan than malt from low‐seeding‐rate barley. Increasing rates of nitrogen fertilisation caused grain protein levels to increase, which limited endosperm modification and reduced malt extract levels. AC Metcalfe showed better modification and higher malt extract than CDC Copeland, but CDC Copeland had better protein modification at higher fertilisation rates, which resulted in less reduction of malt extract as nitrogen rate increased. CONCLUSION: Higher seeding rates reduced kernel size and grain protein levels without compromising malt extract owing to better endosperm modification of the more uniformly sized kernels. Negative effects of higher nitrogen rates on malt quality can be reduced through development of cultivars with improved ability to modify protein during malting. © 2012 Her Majesty the Queen in Right of Canada     

Evaluation of the effect of moisture content on cereal grains by digital image analysis

Physical appearance and kernel morphology significantly affect the grade of a harvested crop in addition to other factors such as test weight, percentage of foreign matter and constituent components. Moisture content of grain can potentially affect the physical appearance and kernel morphology. The objective of this study was to evaluate the effect of moisture content on the classification capability of colour, morphology and textural features of imaged grains. Colour images of individual kernels and bulk samples of three grain types, namely Canada Western Amber Durum (CWAD) wheat, Canada Western Red Spring (CWRS) wheat and barley were acquired using a machine vision system. The grain kernels were conditioned to 12%, 14%, 16%, 18% and 20% moisture contents before imaging. Previously developed algorithms were used to extract 123 colour, 56 textural features from bulk sample images and 123 colour, 56 textural, 51 morphological features from individual kernel images. The extracted features were analysed for the effect of moisture content. Statistical classifiers and a back propagation neural network model were used for classifying the grain bulk at different moisture contents. The colour and textural features of bulk grain images were affected by the moisture content more than that of the single kernel images.     

优质籼米地下仓储藏过程中品质变化

为探索成品粮绿色、安全的储藏方法,在南方高温高湿地区,利用地下仓储藏黄花粘和籼优998两种优质籼米,定期检测水分、碎米总量、小碎米率、垩白粒率、黄粒米、直链淀粉、品尝评分值、色泽气味、不完善率、害虫虫口密度等指标。实验结果显示,实验期间,大米水分呈小幅下降;2种大米不生虫时间长达13个月;小碎米率、色泽气味等指标无显著性变化;碎米总量、黄粒米、不完善粒含量小幅增加,直链淀粉含量逐渐增加,但均未导致大米质量等级下降;垩白粒率显著增加,品尝评分值显著下降,且均造成大米质量定等下降。根据国家标准《大米》的规定,籼优998于储藏3个月后,质量定等由二级降为三级,储藏6个月后,已不属于优质籼米,黄花粘于实验结束后仍为优质籼米三级。说明地下仓具有良好的保湿、保鲜和害虫抑制效果,优质籼米耐储性能与储藏条件和品种均相关。     

Development of a Single Kernel NIR Barley Protein Calibration and Assessment of Variation in Protein on Grain Quality

In this paper, we describe results from a preliminary experiment on the development of a near infrared reflectance (NIR) calibration for single kernel (SK) % protein content in barley. The SKNIR calibration was developed using kernels from breeding lines and commercial barley varieties with a range in protein content of 7.3% to 16.6% “as is”. The calibration model produced an R² = 0.903, while the validation set had a R² = 0.837 with a standard error of cross validation and a standard error of prediction of 0.8% for both the calibration and validation sets respectively. The calibration was then used to estimate the variation in % protein of 4,000 single kernels from a commercial variety (Gairdner at 9.3% protein) by segregating kernels into six sub‐groups (<7.8%, 7.9–8.3%, 8.4–9.0%, 9.1–9.7%, 9.8–10.4%, >10.5% “as is”). These sub‐groups then had additional grain quality tests carried out including grain size, thousand kernel weight and NIR estimates of % protein, starch, hardness and barley hot water extract (HWE). The results showed an increase in grain size, and a decrease in HWE from the low to high % protein sub‐groups. While only a single variety was used in the SKNIR protein segregation study, the results suggested SKNIR could be used to screen for the variation in grain quality traits based on variation in protein content.     

Detection of internally infested popcorn using electrically conductive roller mills

To detect popcorn kernels infested by the internal feeding stored-product insect pest Sitophilus zeamais, maize weevil, a laboratory roller mill was modified so that the electrical conductivity of the grain is measured while the kernels are milled between the rolls. When a kernel with a S. zeamais larvae inside is milled, the moisture from the crushed insect abruptly changes the conductivity of the test circuit. The objective of this study was to determine the potential of the modified conductance mill to detect popcorn infested with different developmental stages. Two laboratory milling units were tested that had differing sharpness, which affected the feed-rate through the rolls. One mill averaged 135 s to feed 1 kg of popcorn while the second mill with sharper teeth averaged 100 s to feed 1 kg of popcorn. Four popcorn varieties were evaluated, with their average kernel weight ranging from 12.5 g to 18.5 g per 100 kernels. Known numbers of infested popcorn kernels were added to 1 kg samples of popcorn. The slower feeding mill detected 81% of the pupae, 91% of the medium larvae, and 47% of the small larvae. The faster feeding mill detected 75% of the pupae, 80% of the medium larvae, and 43% of the small larvae. Our results indicate that the conductance mill is a good method for quickly evaluating popcorn samples for kernels infested with late stage larvae and pupae.     

Micromechanical properties of almond kernels with various moisture content levels

Almond fruits are subjected to various mechanical stresses throughout production, from harvest to processing, storage and packaging. Kernel properties play an important role in reducing mechanical damage such as scratches and penetration of shell pieces. Knowledge of kernel properties under various conditions of the fruit can assist in optimising post-harvest and processing lines to minimise kernel damage and thus maximise final kernel quality. Kernel moisture content is one of the main attributes affecting the kernel’s response to mechanical processing. Increasing the kernel moisture content to an optimum level through wetting fruit prior to processing can lead to a reduced percentage of damaged kernel. Water added to the structure of kernels acted as a plasticiser and helped the kernels to absorb the mechanical load instead of fracturing and breaking into pieces. In this study, tests were conducted on almond kernels with different moisture content levels from 5.52 to 14.09g/100g wet basis. Kernels from a Nonpareil variety were tested in dried and wetted conditions. Test results showed that kernels with higher moisture content were able to undergo a larger deformation at a given force value in comparison with dry kernels. Average deformation for dry samples was from 0.12 mm, which increased to an average of 0.25 mm in wetted samples. The effect of skin on the mechanical properties of the kernels (with and without skin) was studied using a mechanical tester. The test results showed a peak force value in samples tested with skin in comparison with the kernels tested without skin.     

Mechanical strength and rheological behaviour of barley kernels

Basic mechanical and rheological properties (stress relaxation behaviour) of single barley kernels under uni-axial compression were studied. The mechanical properties studied were the modulus of elasticity, yield and ultimate compressive strength, and the modulus of toughness as influenced by the moisture content. The stress relaxation experiments also included the effect of deformation rates and strain levels.
Results indicated that with an increase in moisture content, the strength of the barley kernels decreased while the energy required to cause rupture in the kernel increased initially and then decreased. The stress relaxation behaviour of barley kernels was described by a threeterm Maxwell model with a Maximum Relative Difference (MRD) ≤5%, when compared with one- and two-term Maxwell models. The elastic component (E¹) and relaxation time constant (τ¹) of the first term of the three-term Maxwell model decreased linearly with increase in moisture content. Of the different variables studied, moisture content had a significant influence on both of these parameters.     

Estimating mycotoxin contents of Fusarium-damaged winter wheat kernels

Winter wheat (Triticum aestivum L., cultivars Ritmo and Dekan) grain was sampled in Northern Germany between 2001 and 2006. Kernels damaged by fungi of the genus Fusarium were separated from sound grain by visual assessment. Samples containing 0%, 20%, 40%, 60%, 80% and 100% of Fusarium-damaged kernels were compiled and analyzed for the Fusarium type B trichothecenes deoxynivalenol (DON, 2001-2006), nivalenol (NIV, 2006), 3-acetyl-deoxynivalenol (3AcDON, 2006) and 15-acetyl-deoxynivalenol (15AcDON, 2006). The relationship between mycotoxin contents and the percentage of Fusarium-damaged kernels was calculated for each lot of grain. Apart from one exception, relationships between the percentage of Fusarium-damaged kernels and NIV, 3AcDON or 15AcDON were non-significant. In contrast, close relationships between the percentage of Fusarium-damaged kernels and the DON content were observed (r(2)=0.93-0.99). The y-axis intercepts were not significantly different from zero, but the DON content of the damaged kernels varied by a factor of 11.59 between years and by a factor of 1.87 between cultivars. Fusarium-damaged kernels contained between 0.21 and 2.39 microg DON kernel(-1). The overall average DON content of a Fusarium-damaged wheat kernel was 1.29 +/- 0.11 microg. The DON content of diseased kernels was affected by environment and wheat genotype but not by genotype x environment interaction. On average, Fusarium-damaged kernels contained 9.7-fold more DON than 15AcDON, 19.5-fold more DON than NIV, and 26.9-fold more DON than 3AcDON. 3AcDON and 15AcDON contents per wheat kernel were not significantly different between cultivars. On average, 4.27% of Fusarium-damaged kernels were sufficient to reach the 1.25 mg DON kg(-1) grain limit for unprocessed cereals in the EU. Given the low percentages of Fusarium-damaged kernels that are equivalent to current legal DON limits, grading accuracies >96% would be needed when using automatic grading systems for separating sound from damaged kernels.     

Pattern of Nitrogen Distribution in Barley Grains Grown in the Field

Single grain analysis showed that barley grains synthesized different levels of total nitrogen during development in a commercial field of barley. The difference in total nitrogen content of the individual barley grains was influenced by the topography of the field in which the barley was grown. Barley samples obtained from the higher ground and the peripheries of the field had incorporated lower levels of total nitrogen in the grain. In contrast, barley grains harvested from valley areas in the middle of the field incorporated a higher level of total nitrogen.     

Mycotoxins in cereal grain. Part 13. Deoxynivalenol and 3-acetyl-deoxynivalenol in wheat kernels and chaff with head fusariosis symptoms

In the period of harvest at 1987 field samples of wheat heads with fusariosis symptoms were collected in 18 provinces of Poland. Subsamples of heads infected with Fusarium culmorum (W.G.Sm) Sacc. and Fusarium graminearum Schwabe were analyzed for Fusarium metabolites. In fractions of kernels with visible Fusarium-damage deoxynivalenol (DON) was present in average amount of 18.7 mg/kg (range 9.6-25.3 mg/kg) and 3-acetyl DON 1.9 mg/kg. Fractions of kernels without symptoms of visible Fusarium-damage contained only DON at average 2 mg/kg (range 0.8-3.6 mg/kg). A method of approximate calculation of DON content in a given lot of grain is proposed which may be realized during samples grading.     

Effect of pre-harvest flooding of paddy on the milling and cooking quality of rice

The physico-chemical, milling, pasting and cooking characteristics of six cultivars of paddy, viz PR-106, PR-109, PR-103, Java, PR-108 and Basmati-370, as affected by flooding were investigated. A significant reduction in 1000-kernel weight and bulk density of paddy rice in damaged samples was observed. The kernels in flood-affected samples became soft and developed fissures which contributed to low head rice recoveries. The milled rice from them had lower kernel weight and protein content but showed higher amylose and ash content. The diastatic activity of these samples was higher. Amylographic characteristics showed no effect on the gelatinisation time and temperature in most of the samples. Peak viscosity and setback were affected in all samples, and the effect was variable among different varieties. The flood-affected samples showed lower cooking time and higher gruel solids loss, and were rated poorer organoleptically.     

Influence of harvest date and geographical location on kernel symptoms, fungal infestation and embryo viability of malting barley

This study focused on the influence of harvest timing and geographical location on spring malting barley (potential malting variety) in terms of fungal infestation and seedling viability in symptomatic and asymptomatic kernels. The study was conducted over two consecutive crop years (2003-2004) at four locations in Slovakia. The following categories of the barley kernels were used for the assessment: kernels with black point symptoms (BPK), kernels with black cover on their surface (BCK), pink-colored kernels (PCK) and asymptomatic kernels (AK). The occurrence of various fungi was detected in all kernel categories ranging from 60 to 100%. The most frequent fungal contaminants were members of the genus Alternaria, recovered from BPK in the range of 52.6-69.85%, BCK (62.36-73.28%) and AK (55.35-69.58%). The prevalence of Alternaria spp. was recorded for each harvest time. Other dematiaceous fungi, Epicoccum nigrum and Cochliobolus sativus were found with medium frequency in the same three categories. However, C. sativus was recovered with a higher frequency in BPK (2.6-25.3%). In PCK, the most commonly recovered fungi were species of Fusarium with F. avenaceum (59.2-93.2%) as the most prevalent. The infestation of kernels by fungi from other genera showed only low frequency within all the kernel categories investigated. There was no significant influence of the year and location on the proportion of the symptomatic kernel categories. Kernel germination was inhibited to a greater degree in the wetter and colder year. The strongest inhibition of germination ranging from 2.35 to 22.45% was recorded in PCK in all locations and both years. Germination declined from PCK to BCK (43.2-90.32%), and BPK (45.6-91.61%), while it was highest in AK at all harvest times (63-93.6%). This study found that the black covering symptoms (BCK) caused greater damage to viability of the kernels than black point symptoms (BPK). The delayed harvest time resulted not only in increasing numbers of discolored kernels and undesirable symptomatic kernel fractions but also in lower germination of the kernels tested.     

Natural occurrence of scirpentriol in cereals infected by Fusarium species.

Wheat, barley and oat grain samples naturally contaminated with Fusarium spp. were analysed for the presence of scirpentriol (STO). This toxin was detected in 1, 37 and 8% of 248 wheat, 32 barley and 99 oat grain samples, respectively, and the maximum concentration was 83 microg x kg(-1). Samples of wheat and oat grain with visible scab symptoms were also analysed, and STO (mean level 255 microg x kg(-1)) was detected only in oat samples infected with F. sporotrichioides and F. poae as the dominant species. We analysed 15 barley samples that were subdivided based on seed size into fractions of <2.5 and > 2.5 mm in diameter. The smaller kernels contained an average 94% of the STO in the samples (in kernel fraction > 2.5 mm 28 microg x kg(-1), <2.5 mm 297 microg x kg(-1)). In oats, STO levels were highest in the chaff, lower in the stalk's apical internode and lowest in the grain.     

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.     

The impact of barley nitrogen fertilization rate on barley brewing using a commercial enzyme (Ondea Pro)

Two Australian (Buloke and Commander) and two Canadian (CDC Meredith and Bentley) barley varieties were grown under four levels of nitrogen fertilization (0, 20, 40 and 80 kg ha^?1). Barley samples were assessed by barley brewing with the Ondea Pro enzyme cocktail for mashing analysis and were compared with typical malt brewing quality specifications. The study observed that increased nitrogen fertilization resulted in increased barley kernel nitrogen content which significantly impacted a range of wort quality parameters including increased soluble nitrogen, free amino nitrogen and barley beta‐amylase level, but also reduced extract, barley Kolbach index, β‐glucan and colour. Increased grain nitrogen had relatively little effect on apparent attenuation limit, lautering and barley limit dextrinase level. Knowledge of the effects of interactions between barley of different qualities (e.g. nitrogen content) and the Ondea Pro enzymes on wort quality will result in enhanced barley to directly and efficiently brew good quality beer, to better satisfy the quality expectations of brewers. Copyright © 2018 The Institute of Brewing & Distilling     

Chemical and physical characteristics of different barley samples

Eight different barleys, including covered and naked samples containing low, normal and high amylose starches as well as a sample with low starch and high β‐glucan content and a malting barley, were examined both from a chemical and physical perspective. In the chemical characterisation of the samples, analyses of nutrients were performed, while in the physical characterisation, weight of individual kernels, sieving fractions, bulk density, terminal velocity by pneumatic classification and parameters from a Single Kernel Characterization System (SKCS) were analysed. Results were evaluated by principal component analysis (PCA). The major trend found was that hull content and endosperm composition varied independently of each other. Constituents found mainly in the hull were positively correlated with each other, but negatively with bulk density and the 95% quantile of terminal velocity. There was a positive correlation between average value and standard deviation of grain mass, fat and starchy endosperm components such as extractable dietary fibre residues and β‐glucan. The latter variables were negatively correlated to β‐glucan extractability. © 1999 Society of Chemical Industry     

A comparison of methods for the extraction and separation of hordein fractions from 29 barley varieties

Methods have been developed for extracting and comparing the hordein fractions of barley seed as a means of identifying different varieties. A rapid method involving a single extraction with 55% (v/v) propan-2-ol+2% (v/v) 2-mercaptoethanol at 60°C removed slightly less nitrogen from milled grain than a more detailed procedure in which three sequential extractions were made with the same solvent. The hordein fractions extracted by these two procedures were alkylated and their component poly-peptides separated by four one-dimensional and two two-dimensional systems. The results showed that the hordein extracted by both techniques had the same polypeptide composition and thus the rapid method was satisfactory for use in comparing varieties. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and isoelectric focusing were used to compare the polypeptide composition of the hordein fractions from 29 varieties. Using the former system a total of 11 different patterns were recognised while further small differences between several varieties were revealed by isoelectric focusing or two-dimensional analysis. If the polypeptide patterns obtained by these techniques are considered in conjunction with other grain characters it should be possible to identify almost all of the 29 varieties.