Composition of Functional Lipids in Hulled and Hulless Barley in Fractions Obtained by Scarification and in Barley Oil

Two cultivars of hulled barley (Thoroughbred and Nomini) and two cultivars of hulless barley (Doyce and Merlin) were scarified to abrade the outer layers of hull and pericarp. The resulting scarification fines fractions were evaluated as potential sources of functional lipids (phyto‐sterols, tocopherols, and tocotrienols). The levels of total phytosterols and total tocotrienols in the barley scarification fine fractions were probably not high enough to justify their use as functional foods. However, the levels of total phytosterols and total tocotrienols in the oils extracted from both whole kernels and scarified fines were both sufficiently high to make it reasonable to consider their potential use as new functional oils. Indeed, the levels of total tocotrienols in barley oils (2,911–6,126 mg/kg of oil) are several‐fold higher than those reported in two other oils that are being marketed as high in tocotrienols: palm oil (530 mg/kg) and rice bran oil (770 mg/kg). The levels of total phytosterols in barley oils range from 1.20 to 9.60 g/100 g of oil.     

Relationships Between the Microstructure,Physical Features,and Chemical Composition of Different Maize Accessions from Latin America

Chemical composition (moisture, total lipids, protein, and apparent amylose) and some physical features (1,000 kernel weight, hardness, and anatomical composition) were determined in 71 accessions representing races of maize from Latin America. Their microstructural characteristics (size and compaction of endosperm cell bodies, pericarp thickness, horny‐floury endosperm ratio, and morphology and size of starch granules) were also evaluated using environmental scanning electron microscopy (ESEM). Compaction was the most important microstructural feature of the maize kernels, representing kernel hardness. Highly compact kernels tended to be hard, with high protein, pericarp, and hard‐endosperm content and high pericarp thickness, but with low moisture, amylose content, and kernel weight and size. The opposite was observed in the least compact kernels. Highly compact kernels tended to have small, polygonal starch granules (<10 μm), while the least compact kernels contained large, spherical granules (>10 μm). These results suggest that microstructure is responsible for the physical features of maize kernels and that microstructure is related to chemical composition.     

Removal and Isolation of Germ‐Rich Fractions from Hull‐less Barley Using a Fitzpatrick Comminuting Mill and Sieves

A process was developed to produce a germ‐enriched fraction from hull‐less barley using a Fitzpatrick comminuting mill (FitzMilling) followed by sieving. Hulled and hull‐less barleys contain 1.5–2.5% oil and, like wheat kernels, which contain wheat germ oil, much of the oil in barley kernels is in the germ fraction. A process that combined FitzMilling and sieving produced a germ‐enriched fraction with an oil content of ≈15% and a yield of ≈1.1%. For comparison, this is higher than the levels of oil in most samples of commercial wheat germ. Experimental conditions were also described to produce a germ‐enriched fraction with a higher yield (2.16%), but it would have lower oil content (10.24%). Germination and compositional analysis studies suggested that FitzMilling hull‐less barley for 2 min or longer reduced germination rates to 1% or less, which was interpreted to mean that almost the entire viable germ was removed. In contrast, FitzMilling conventional hulled barley for 4 min had no effect on germination, and milling for 6 and 8 min resulted in germination rates of 36 and 12%, respectively. The oil extracted from germ‐enriched fractions was rich in free phytosterols (≈1%), phytosterol esters (3–7%), and free fatty acids (2–10%). These germ‐enriched fractions and the extracted oil they contain may have value as nutraceuticals or premium edible oils.     

Structure and Physicochemical Properties of Starches from Sieve Fractions of Oat Flour Compared with Whole and Pin-Milled Flour

One oat cultivar grown in Idaho (three field sites) was pin-milled and separated by sieving to investigate whether starch from oat bran differs from the remainder of kernel. Ground oat particles were classified into three sieve fractions: 300–850 μm, 150–300 μm and <150 μm). β-Glucan content in sieve fractions was analyzed and starch was extracted from kernels without milling and from kernels of each sieve fraction. β-Glucan contents of 300–850, 150–300, and <150 μm sieve fractions were 4.2, 2.3, and 0.8%, respectively. Therefore, starch in bran (300–850 μm sieve fraction) and endosperm (<150 μm sieve fraction) were separated. Starch isolated from entire kernels had significantly higher apparent and absolute amylose content than starch from the 300–850 μm sieve fraction. Starch from different sieve fractions was not significantly different in the apparent amylose, absolute amylose, amylopectin molecular weight, gyration radii, starch gelatinization, and amylose-lipid complex thermal transition temperatures. Starch from the 150–300 μm sieve fraction had significantly lower peak, final, and setback viscosity compared with the starch isolated from the 300–850 μm and <150 μm sieve fractions. Starch removed from the oat bran fraction during β-glucan enrichment may have different applications compared with starch obtained from other kernel compartments. Because pin-milling decreased apparent amylose content and shortened amylopectin branch chains, its potential to alter starch structure should be considered.     

Hydrolysis and Fermentation of Pericarp and Endosperm Fibers Recovered from Enzymatic Corn Dry‐Grind Process

A modified dry‐grind corn process has been developed that allows recovery of both pericarp and endosperm fibers as coproducts at the front end of the process before fermentation. The modified process is called enzymatic milling (E‐Mill) dry‐grind process. In a conventional dry‐grind corn process, only the starch component of the corn kernel is converted into ethanol. Additional ethanol can be produced from corn if the fiber component can also be converted into ethanol. In this study, pericarp and endosperm fibers recovered in the E‐Mill dry‐grind process were evaluated as a potential ethanol feedstock. Both fractions were tested for fermentability and potential ethanol yield. Total ethanol yield recovered from corn by fermenting starch, pericarp, and endosperm fibers was also determined. Results show that endosperm fiber produced 20.5% more ethanol than pericarp fiber on a g/100 g of fiber basis. Total ethanol yield obtained by fermenting starch and both fiber fractions was 0.370 L/kg compared with ethanol yield of 0.334 L/kg obtained by fermenting starch alone.     

Variation in Kernel Hardness and Associated Traits in U.S. Barley Breeding Lines

Kernel hardness is an important trait influencing postharvest handling, processing, and food product quality in cereal grains. Though well‐characterized in wheat, the basis of kernel hardness is still not completely understood in barley. Kernels of 959 barley breeding lines were evaluated for hardness using the Single Kernel Characterization System (SKCS). Barley lines exhibited a broad range of hardness index (HI) values at 30.1–91.9. Distribution of kernel diameter and weight were 1.7–2.9 mm and 24.9–53.7 mg, respectively. The proportion of hull was 10.2–20.7%. From the 959 breeding lines, 10 hulled spring barley lines differing in HI values (30.1–91.2) were selected to study the associations of HI with proportion of hull, kernel weight, diameter, vitreousness, protein, β‐glucan, and amylose content. Vitreousness, evaluated visually using a light box, showed a clear distinction between hard and soft kernels. Hard kernels appeared translucent, while soft kernels appeared opaque when illuminated from below on the light box. Kernel brightness (L*), determined as an indicator of kernel vitreousness, showed a significant negative correlation (r = –0.83, P < 0.01) with HI. Protein, β‐glucan, amylose content, proportion of hull, kernel weight, and diameter did not show any significant association with HI.     

Effect of Corn Milling Practices on Aleurone Layer Cells and Their Unique Phytosterols

Coarse and fine fiber fractions obtained from the corn wet‐milling processes, with and without steeping chemicals (SO₂ and lactic acid), were evaluated microscopically for structure and analytically for recovery of phytosterol compounds from the fiber oil. Microscopic results showed that wet milling, with and without chemicals during steeping, changed the line of fracture between pericarp and endosperm and therefore affected the recovery of the aleurone layer in coarse (pericarp) and fine (endosperm cellular structure) fiber. Analytical results showed that most of the phytosterols and mainly phytostanols in corn fiber are contributed by the aleurone layer. Hand‐dissection studies were performed to separate the two layers that comprise the wet‐milled coarse fiber, the aleurone, and pericarp layer. Analyses revealed that the aleurone contained 8× more phytosterols than the pericarp.     

Genotypic Variation in Color and Discoloration Potential of Barley‐Based Food Products

Barley has a variety of potential food uses. However, the dark gray color of the final products negatively affects consumer acceptability. We determined the discoloration potential of barley from different classes and genotypes, and evaluated the relationship of barley composition, total polyphenol content, and polyphenol oxidase (PPO) activity with discoloration potential of barley. Barley grains were abraded, milled into flour, and analyzed for composition, total polyphenol content, and PPO activity. Total polyphenol content of abraded barley, expressed as gallic acid %, was lowest in hulled proanthocyanidin‐free barley (0.02–0.04%), followed by hulled proanthocyanidin‐containing barley (0.11–0.18%), and hull‐less barley (0.19–0.26%). PPO activity of abraded kernels ranged from 62.1 units/g in hulled proanthocyanidin‐containing Baronesse to 116.5 units/g in hulled proanthocyanidin‐free CA803803. Dough sheet brightness (L* value) was the best indicator of discoloration potential of barley. Large variation in L* value of dough sheets was observed among different classes and among genotypes within classes. Brightness of dough sheets measured at 24 hr were significantly higher in hulled (65.3–78.1) than in hull‐less (59.0–63.9) barley, and within hulled barley, higher in proanthocyanidin‐free (72.2–78.1) than in proanthocyanidin‐containing (65.3–69.6) barley. Total polyphenol content significantly correlated with the discoloration potential of barley. Protein content and ash content also had a significant negative correlation with discoloration of dough sheets. The results indicated that polyphenol compounds may play a major role in discoloration potential of barley‐based products.     

Effects of Selected Barley Cultivars and Their Pearling Fractions on Inhibition of Human LDL Oxidation In Vitro Using a Modified Conjugated Dienes Method

Oxidation of LDL cholesterol is an important factor in the development of atherosclerosis and heart disease. In this study, selected Canadian and Egyptian barley cultivars and their pearling fractions were evaluated for antioxidant capacity to inhibit human LDL oxidation in vitro. Measurement of conjugated dienes (CD) at 234 nm was optimized to determine the degree of LDL oxidation. Dilution of oxidized LDL with iso‐propanol gave a distinct diene conjugation peak. Significant differences in total phenols content (TPC) were found between the cultivars tested, with the hulless barley having greater TPC and inhibition capacity compared with hulled barleys. The outer layers fraction contained the highest TPC, lowest CD formation, and longest lag time, whereas the inner, or endosperm fraction, had the lowest inhibition effects. The middle pearling and hull fractions possessed intermediate inhibition effects. The inhibitory effect of barley extracts was dependent on phenols concentration following a linear or quadratic pattern. The results suggest that barley whole meals, outer layers, middle pearling, or hull fraction would be a potential LDL antioxidant.     

Influence of Kernel Size and Shriveling on Soft Wheat Milling and Baking Quality

Small kernels of soft wheat are sometimes considered to be harder than larger kernels and to have inferior milling and baking characteristics. This study distinguished between kernel size and kernel shriveling. Nine cultivars were separated into large, medium, and small kernels that had no shriveling. Eleven cultivars were separated into sound, moderate, and severely shriveled kernels. Shriveling greatly decreased the amount of flour produced during milling. It adversely affected all other milling quality characteristics (ash content, endosperm separation index, and friability). Shriveled kernels produced flour that had inferior soft wheat baking qualities (smaller cookie diameter and higher alkaline water retention capacity). In contrast, test weight and milling qualities were independent of kernel size. Small, nonshriveled kernels had slightly better baking quality (larger cookie diameter) than larger nonshriveled kernels. Small kernels were softer than large kernels (measured by break flour yield, particle size index, and flour particle size). Small nonshriveled kernels did not have diminished total flour yield potential or other reduced flour milling characteristics. Those observations suggest a possibility of separating small sound kernels from small shriveled kernels to improve flour yield and the need to improve dockage testing estimation techniques to distinguish between small shriveled and small nonshriveled kernels.     

Laboratory Measurement of Yield and Composition of Dry‐Milled Corn Fractions Using a Shortened,Single‐Stage Tempering Procedure

The objective was to describe a laboratory‐scale dry‐milling procedure that used single‐stage tempering and determine the effect of hybrid on yields and fraction compositions in milled corn. Samples of 11 commercially available hybrids were processed through a laboratory dry‐milling procedure that used 1 kg samples of corn to produce milling fractions of large grits, small grits, fines, germ, and pericarp. Compositions of milling fractions (protein, neutral detergent fiber, ash, and crude fat) were determined. The procedure used a single‐stage tempering step that increased corn moisture from 15 to 23.5% wb during an 18‐min tempering period. Germ were separated from endosperm particles using a roller mill followed by screening over a sieve with 1.68‐mm openings. Coefficients of variability were small, indicating acceptable repeatability. Overall yield means were 39.2, 25.3, 13.8, 78.2, 14.3, and 6.8 g/100 g (db) for large grits, small grits, fines, total endosperm, germ, and pericarp, respectively. There were effects due to hybrid (P < 0.05) on fraction yields and compositions of milling fractions. Correlations (r) among endosperm fractions (large grits, small grits, and fines) ranged from 0.54 to |–0.92|. Correlations among endosperm fractions and germ and pericarp were <0.68. The developed dry‐milling method estimated milling yields among hybrids with low standard deviations relative to the means and should be a useful tool for research and industry in measuring dry‐milling characteristics.     

Distribution of β‐Glucan in the Grain of Hull‐less Barley

Nine hull‐less barley (HB) containing waxy (0–7% amylose), normal (≈25% amylose), or high amylose (≈42% amylose) starch with normal or fractured granule make‐up and 4–9% (1→3)(1→4)‐β‐d ‐glucans (β‐glucan) were pearled to remove 70% of the original grain weight in 10% intervals. The pearled fractions were analyzed for β‐glucan distribution within HB grain. Protein content of the pearled fractions indicated that the three outermost fractions contained pericarp and testa, aleurone, and subaleurone tissues, respectively. For all HB, β‐glucan and acid‐extract viscosity were very low in the outermost 20% of the kernel. For low β‐glucan HB, β‐glucan content was the greatest in the subaleurone region and declined slightly toward inner layers. For high β‐glucan HB, however, more than 80% of grain β‐glucan was distributed more evenly throughout the endosperm. Acid extract viscosity was significantly (P < 0.01) correlated with total (r = 0.75) and soluble (r = 0.87) β‐glucan content throughout the kernel of all HB. Growing conditions, location and year, had significant effects on the concentration of protein, starch and β‐glucan. However, protein, starch, and β‐glucan distribution patterns were not affected by growing conditions. The difference in β‐glucan distribution between low and high β‐glucan HB may explain the difference in milling performance of HB with low or high β‐glucan.     

Distribution of total aflatoxins in milled fractions of hulled rice

Two varieties of hulled rice artificially contaminated with aflatoxins at five different levels were processed by dehulling and polishing methods. Contamination levels ranged from 356 to 818 microg/kg and from 244 to 645 microg/kg in medium and long grain rice, respectively. After physical processing, four different milled fractions were obtained (hull, bran, polished broken grains, and polished whole kernels). The fractions were analyzed for total aflatoxins (B1, B2, G1, and G2) by enzyme-linked immunosorbent assay (ELISA). Aflatoxins were removed in fractions intended for human consumption (polished broken grains and polished whole kernels) at rates up to 97%. They were found throughout all fractions, but higher contamination levels were detected in hull and bran fractions than in unprocessed kernels and polished fractions. Regardless of the rice variety, the aflatoxin distribution pattern depended on the initial contamination level and type of milled fraction but not on the duration of polishing.     

Tocopherols and Tocotrienols in Barley Oil Prepared from Germ and Other Fractions from Scarification and Sieving of Hulless Barley

Two cultivars of hulless barley (Doyce and Merlin) were scarified to abrade the outer layers of the kernels (germ, pericarp, and aleurone). The resulting scarification fines fractions were then separated into four particle-size subfractions using sieves. Each of the size subfractions was then extracted with hexane to produce a barley oil, and the levels of free phytosterols, tocopherols, and tocotrienols in the various barley oils were compared. For both cultivars, the fraction with the largest particle size (0.717–1.410 mm) had the highest oil yields (11–12%). Visual examination of this fraction indicated that it consisted almost entirely of small fragments (≈1 mm) of the germ portion of the kernel. The levels of tocopherols were highest in the largest particle-size fraction and their proportion decreased in the fractions with decreasing particle size. In contrast, the levels of tocotrienols were very low in the largest particle-size fraction and increased in the fractions with decreasing particle sizes. Intact germ was also prepared by hand-dissection, extracted, and analyzed. The results indicate that the ≈1 mm germ fragments obtained by scarification-sieving consisted almost entirely of germ fragments, but these fragments represented only 17.5 and 23.7% of the total mass of the germ, from Merlin and Doyce, respectively. These results also suggest that it may be possible to control the concentrations of tocopherols and tocotrienols in barley oil by controlling the particle size of the feedstock used to extract the oil. Germ fragments isolated by such processes could potentially be used as functional food ingredients or extracted to yield oils enriched in health-promoting phytosterols, tocopherols, or tocotrienols.     

Effect of Kernel Size,Location, and Type of Damage on Popping Characteristics of Popcorn

Popping characteristics, specifically expansion volume and popping time, were studied for damaged popcorn. A single variety of commercial undamaged yellow popcorn was separated into four size fractions (D < 4.36, 4.36 < D < 5.16, 5.16 < D < 5.95, and D > 5.95 mm) by screening with round-hole sieves. Kernels were damaged using a razor knife by either slicing a 2-mm diameter piece of the endosperm or the germ or by cutting through the pericarp and seed coat into the endosperm or the germ ≈2 mm. A total of five combinations of location and damage were studied (tip cap removed, side cut, side sliced, germ cut, and germ sliced) for each kernel size. A control sample with no damage was also analyzed for each size fraction. All of the damaged kernels (regardless of type of damage) popped, but they had expansion volumes 9.1–47.5% smaller than those of undamaged kernels. The expansion volume of damaged kernels increased by 52.5–85.7%, depending on the damage, when the size of the kernel increased from <4.36 mm to >5.95 mm. Removing the tip cap and slicing through the germ caused less loss of expansion volume than did other types of damage. Damaged popcorn kernels had faster popping times (12.2–24.0 sec) than did undamaged kernels (30.9–34.6 sec). Popping times increased with increasing kernel size for all types of damage.     

Quality Characteristics of Long-Grain Rice Milled in Two Commercial Systems

Long-grain rice variety Kaybonnet was milled to three degree of milling (DOM) levels in two commercial milling systems (a single-break, friction milling system and a multibreak, abrasion and friction milling system) and separated into five thickness fractions. For both milling systems, the surface lipid content (SLC) and protein content of the milled rice varied significantly across kernel thickness fractions. SLC was influenced by DOM level more than by thickness, while the protein content was influenced by thickness more than by DOM level. Particularly at the low DOM levels, the thinnest kernel fraction (<1.49 mm) had higher SLC than the other kernel fractions. Protein content decreased with increasing kernel thickness to 1.69 mm, after which it remained constant. In both milling systems, thinner kernels were milled at a greater bran removal rate as indicated by SLC differences between the low and high DOM levels. For rice milled to a given DOM level, the multibreak system produced fewer brokens than did the single-break system.     

Comparative Studies on Composition and Distribution of Phenolic Acids in Cereal Grain Botanical Fractions

The phenolic acid composition and concentration of four manually separated fractions (pericarp, aleurone layer, germ, and endosperm fractions) as well as whole grains of yellow corn, wheat, barley, and oats were analyzed by HPLC‐MS/MS following microwave‐assisted alkaline aqueous extraction. Phenolic acid compositions in whole grains and their fractions were similar, with minor differences among the grain fractions. Significant differences (P < 0.05), however, were observed in phenolic acid concentrations among cereal types, within cereal varieties, and among grain fractions, with yellow corn exhibiting the highest values. The concentrations of p‐coumaric and syringic acid in the pericarp were 10‐ to 15‐fold and 6‐ to 10‐fold higher, respectively, in yellow corn than in wheat, barley, and oats. In the aleurone layer, sinapic and vanillic acids in yellow corn were about 8‐ and 30‐fold more than in wheat. The germ fraction of wheat had 1.8 times more syringic acid than yellow corn germ. Grain fractions, excluding endosperm, had enhanced levels of phenolic acids compared with whole grain. Sinapic acid was more concentrated in the pericarp and germ of wheat, whereas isoferulic acid was concentrated in the germ of purple barley. Syringic and vanillic acids were concentrated in the pericarp and sinapic acid in the aleurone layer of yellow corn. These findings are important in understanding the composition and distribution of phenolic acids, and they act as a guide in identification of grain fractions for use as food ingredients. In addition, yellow corn fractions (aleurone and pericarp) may be potential alternative phenolic‐rich functional food ingredients in grain‐based food products.     

Distribution and Structural Variation of Nonstarch Polysaccharides in Milling Fractions of Hull‐less Barley with Variable Amylose Content

Three hull‐less barley genotypes containing starches with variable amylose content (23.8% normal, 4.3% waxy, 41.8% high‐amylose barley) were pearled to 10% and then roller‐milled to produce pearling by‐products (PBP), flour, and fiber‐rich fractions (FRF). PBP were enriched in arabinoxylans, protein, and ash and contained small amounts of starch and β‐glucans. FRF were considerably enriched in β‐glucans and arabinoxylans. The solubility of β‐glucans was higher in PBP than in FRF. The solubility of arabinoxylans was higher in FRF than in PBP. Small amounts of arabinogalactans detected in barley were concentrated in the outer portion of the barley kernel. The content and solubility of nonstarch polysaccharides (NSP) in various milling fractions was also dependent on the type of barley. To obtain more detailed information about the content and molecular structure of NSP, each milling fraction was sequentially extracted with water, alkaline [Ba(OH)₂], again with water, and finally with NaOH. These extractions resulted in four sub‐fractions: WE, Ba(OH)₂, Ba(OH)₂/H₂O, and NaOH. β‐Glucans and arabinoxylans exhibited structural heterogeneity derived from differences in their location within the kernel as well as from the genetic origin of barley. The WE arabinoxylans from FRF and flour had a substantially lower degree of branching than those from PBP. The WE arabinoxylans from FRF of high‐amylose and normal barley contained more unsubstituted Xylp residues but fewer doubly‐substituted and singly‐substituted Xylp at O‐2 than their counterparts from PBP. The WE arabinoxylans from FRF of waxy barley had a relatively high content of doubly‐substituted, but very few singly‐substituted Xylp residues. In all three barley genotypes, the ratio of tri‐ to tetrasaccharides in β‐glucans from PBP was higher than from flour and FRF. Substantial differences in the molecular weight of NSP in different milling fractions were also observed.     

Distribution of Peroxidases in Durum Wheat (Triticum durum)

A biochemical study of the main durum wheat milling fractions (bran, embryo, and semolina) showed that peroxidases (POD) were present in multiple forms in the kernel and appeared to be tissue specific: one form for the embryo, one for the endosperm, one for the subaleuronic layer, and one for the outer layers. Large varietal differences were found regarding both the composition and the POD activity. POD activity, detected by diaminobenzidine, was found mainly in the cell wall of the subaleurone layer and inside some specific, differentiated cells of the embryo. Immuno‐localization with antibodies of durum wheat POD showed the presence of POD in several layers of the pericarp (epidermis) and the seed coat (testa), in the embryo, and also in the endosperm. In this latter tissue, the staining intensity decreased gradually from the outer layers toward the center of the kernel. The localization of POD in durum wheat kernel suggests specific functions for different forms.