Winter annual small grain forage potential. II. Quantification of nutritive characteristics of four small grain species at six growth stages

Abstract

Four small grain species, barley, oat, rye, and wheat were harvested at six growth stages to investigate their nutritive quality as a possible replacement for corn silage. Crude protein (CP), in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin contents were measured on fresh and ensiled samples. The IVDMD, an estimate of forage ruminant digestibility, of all species generally decreased from the vegetative (765–854 g kg^‐1) through the milk stage (505–662 g kg^‐1) and then remained unchanged or increased slightly through hard dough with the exception of oats which often decreased during later stages of growth. The IVDMD of rye was usually lower than the other species from the milk to hard dough stage. The IVDMD of barley was generally higher than the other species at the soft and hard dough stages. The NDF, ADF, and lignin fractions usually increased from the vegetative to milk stages and remained unchanged or increased slightly through the hard dough stage. The ADF and lignin are negatively associated with forage digestibility while NDF values are negatively related to dry matter intake. The ADF of rye was generally higher than the other species at the milk and soft dough stages. Rye and barley contained more lignin than the other species from the heading through hard dough stage. Crude protein content generally decreased from the vegetative through milk stages and then leveled off or decreased slightly through the hard dough stage. Crude protein of oats was lower than other species at the vegetative stage, while rye generally contained more crude protein than the other species at the vegetative and boot stages. These data in combination with forage yield data reported in an associated paper suggest that small grains can offer a nutritious source of animal feed for farmers in the southeastern United States. Rye tended to stand out among the species at the early stages of growth (vegetative to boot) as a highly digestible green chop or grazing crop that is also high in protein. Barley and wheat stand out as excellent high yielding, nutritious silage choices at the soft dough stage.     

Phenolic compounds of barley grain and their implication in food product discoloration

Barley grains contain significant amounts of phenolic compounds that may play a major role in the discoloration of food products. Phenolic acid and proanthocyanidin (PA) composition of 11 barley genotypes were determined, using high-performance liquid chromatography and liquid chromatography-mass spectrometry, and their significance on food discoloration was evaluated. Abraded grains contained 146-410 microg/g of phenolic acids (caffeic, p-coumaric, and ferulic) in hulled barley and 182-282 microg/g in hulless barley. Hulled PA-containing and PA-free genotypes had comparable phenolic acid contents. Catechin and six major barley PAs, including dimeric prodelphinidin B3 and procyandin B3, and four trimers were quantified. PAs were quantified as catechin equivalents (CE). The catechin content was higher in hulless (48-71 microg/g) than in hulled (32-37 microg/g) genotypes. The total PA content of abraded barley grains ranged from 169 to 395microg CE/g in PA-containing hulled and hulless genotypes. Major PAs were prodelphinidin B3 (39-109 microg CE/g) and procyanidin B3 (40-99 microg CE/g). The contents of trimeric PAs including procyanidin C2 ranged from 53 to 151 g CE/g. Discoloration of barley flour dough correlated with the catechin content of abraded grains (r = -0.932, P < 0.001), but not with the content of individual phenolic acids and PAs. Discoloration of barley flour dough was, however, intensified when total PA extracts and catechin or dimeric PA fractions were added into PA-free barley flour. The brightness of dough also decreased when the total PA extract or trimeric PA fraction was added into heat-treated PA-free barley flour. Despite its low concentration, catechin appears to exert the largest influence on the discoloration of barley flour dough among phenolic compounds.     

Nitrogen fertilization and maturity influence the phenolic concentration of wheat grain (Triticum aestivum)

This work investigated the influence of N fertilization and grain maturity on total phenolic concentration (TPC) of wheat caryopses. A pot experiment was conducted, using soft spring wheat (Triticum aestivum cv. Thasos) which was treated with four different amounts of nitrogen (0.25–2.00 g N pot^?1) and harvested at three different development stages (medium milk stage, late milk stage, and dough maturity). Phenolic compounds were extracted and analyzed as total phenolic concentration in three discrete fractions: free soluble, conjugated soluble and insoluble bound forms. TPC of free phenolic compounds rose with increasing N supply while TPC of conjugated soluble phenolics decreased at the same time. Insoluble phenolics were less affected by N treatment. Total phenolic concentration also changed with the development stage of caryopses and reached a peak at the late milk stage.     

Structural Modifications of Gluten Proteins in Strong and Weak Wheat Dough During Mixing

The network‐forming attributes of gluten have been investigated for decades, but no study has comprehensively addressed the differences in gluten network evolution between strong and weak wheat types (hard and soft wheat). This study monitored changes in SDS protein extractability, SDS‐accessible thiols, protein surface hydrophobicity, molecular weight distribution, and secondary structural features of proteins during mixing to bring out the molecular determinants of protein network formation in hard and soft wheat dough. Soft wheat flour and dough exhibited greater protein extractability and more accessible thiols than hard wheat flour and dough. The addition of the thiol‐blocking agent N‐ethylmaleimide (NEM) resulted in similar results for protein extractability and accessible thiols in hard and soft wheat samples. Soft wheat dough had greater protein surface hydrophobicity than hard wheat and exhibited a larger decrease in surface hydrophobicity in the presence of NEM. Formation of high‐molecular‐weight (HMW) protein in soft wheat dough was primarily because of formation of disulfides among low‐molecular‐weight (LMW) proteins, as indicated by the absence of changes in protein distribution when NEM was present, whereas in hard wheat dough the LMW fraction formed disulfide interaction with the HMW fraction. Fourier transform infrared spectroscopy indicated formation of β‐sheets in dough from either wheat type at peak mixing torque. Formation of β‐sheets in soft wheat dough appears to be driven by hydrophobic interactions, whereas disulfide linkages stabilize secondary structure elements in hard wheat dough.     

Dough Properties and Bread Quality of Wheat–Barley Composite Flour as Affected by β‐Glucanase

Barley is rich in nutritionally positive compounds, but the quality of bread made of wheat–barley composite flours is impaired when a high percentage of barley is used in the mixture. A number of enzymes have been reported to be useful additives in breadmaking. However, the effect of β‐glucanase on breadmaking has scarcely been investigated. In this paper, the influence of different levels (0.02, 0.04, 0.06, and 0.08%, based on composite flour) of β‐glucanase (100,000 U/g) on the properties of dough and bread from 70% wheat, 30% barley composite flour were studied. Although dough development time, dough stability, and protein weakening value decreased after β‐glucanase addition, dough properties such as softness and elasticity as well as bread microstructure were improved compared with the control dough. β‐Glucanase also significantly improved the volume, texture, and shelf life of wheat–barley composite breads. The use of an optimal enzyme concentration (0.04%) increased specific volume (57.5%) and springiness (21%), and it reduced crumb firmness (74%) and staling rate. Bread with added β‐glucanase had a better taste, softness, and overall acceptability of sensory characteristics compared with the control bread. Moreover, the quality of wheat–barley composite bread after addition of 0.04% β‐glucanase was nearly equal to the quality of pure wheat bread. These results indicate that dough rheological characteristics and bread quality of wheat–barley composite flour can be improved by adding a distinct level of β‐glucanase.     

Quantitative and Qualitative Role of Added Gluten on White Salted Noodles

A commercial gluten and glutens isolated from four soft and four hard wheat flours were incorporated into a hard and a soft white flour by replacement to directly determine the quantitative and qualitative role of gluten proteins in making noodles. Gluten incorporation (6%) decreased water absorption of noodle dough by 3%, shortened the length of the dough sheet by 15 and 18%, and increased the thickness of the dough sheet by 18 and 20% in soft and hard wheat flour, respectively. Noodles imbibed less water and imbibed water more slowly during cooking with gluten incorporation, which resulted in a 3‐min increase in cooking time for both soft and hard wheat noodles. Despite the extended cooking time of 3 min, noodles incorporated with 6% gluten exhibited decreases in cooking loss by 15% in soft wheat. In hard wheat flour, cooking loss of noodles was lowest with 2% incorporation of gluten. Tensile strength of fresh and cooked noodles, as well as hardness of cooked noodles, increased linearly with increase in gluten incorporation, regardless of cooking time and storage time after cooking. While hardness of cooked noodles either increased or showed no changes during storage for 4 hr, tensile strength of noodles decreased. There were large variations in hardness and tensile strength of cooked noodles incorporated with glutens isolated from eight different flours. Noodles incorporated with soft wheat glutens exhibited greater hardness and tensile strength than noodles with hard wheat glutens. Tensile strength of cooked noodles incorporated with eight different glutens negatively correlated with SDS sedimentation volume of wheat flours from which the glutens were isolated.     

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.     

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.     

MINERAL ELEMENT DISTRIBUTION AND ACCUMULATION PATTERNS WITHIN TWO BARLEY CULTIVARS

Growth stage effects on distribution of mineral nutrients or beneficial elements phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), chloride (Cl), iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), molybdenum (Mo), sodium (Na), silicon (Si) and nickel (Ni), and the elements bromine (Br), rubidium (Rb), strontium (Sr), barium (Ba), lanthanum (La), cerium (Ce), and uranium (U) in two barley (Hordeum vulgare L.) cultivars and how the distribution of these elements changed were determined during the 2006–2007 growing season in a field experiment. Barley plants were sampled from the field at shooting, heading, soft dough, hard dough and harvest stages, and mineral nutrients and other elements concentrations of spike, flag leaf, old leaf, and stem samples were determined by polarized energy dispersive X-ray fluorescence (PEDXRF). Distribution patterns varied considerably from element to element. At the end of the season much of the Ca, Mg, S, Si, Fe, Mn, Cu, Ni, Sr, Ba, La, Ce, and U were located in the spikes. However, much of the P, K, Zn, Cl, Na, Br, and Rb remained in the old leaves or stem.     

Flour Characteristics Related to Optimum Water Absorption of Noodle Dough for Making White Salted Noodles

Physicochemical properties of 34 wheat flours with various classes and different protein contents were related to optimum water absorption of noodle dough. Club and soft wheat flours generally exhibited higher water absorption (34–37%) of noodle dough than hard wheat flours (31–35%). Optimum water absorption of noodle dough in three hard wheat flours with five different protein contents was 33–37%. Optimum water absorption was negatively correlated with flour protein content and SDS sedimentation volume. Physical properties of flour, damaged starch content, NIRS hardness and water retention capacity, influenced optimum water absorption of noodle dough from club, soft and hard wheat flours. A prediction equation developed using protein content, water retention capacity and SDS sedimentation volume of flour provides a reliable estimation of the optimum absorption of noodle dough for making noodles.     

Comparison of Waxy vs. Nonwaxy Wheats in Fuel Ethanol Fermentation

Fermentation performance of eight waxy, seven nonwaxy soft, and 15 nonwaxy hard wheat cultivars was compared in a laboratory dry‐grind procedure. With nitrogen supplements in the mash, the range of ethanol yields was 368–447 L/ton. Nonwaxy soft wheat had an average ethanol yield of 433 L/ton, higher than nonwaxy hard and waxy wheat. Conversion efficiencies were 91.3–96.2%. Despite having higher levels of free sugars in grain, waxy wheat had higher conversion efficiency than nonwaxy wheat. Although there was huge variation in the protein content between nonwaxy hard and soft wheat, no difference in conversion efficiency was observed. Waxy cultivars had extremely low peak viscosity during liquefaction. Novel mashing properties of waxy cultivars were related to unique pasting properties of starch granules. With nitrogen supplementation, waxy wheat had a faster fermentation rate than nonwaxy wheat. Fermentation rates for waxy cultivars without nitrogen supplementation and nonwaxy cultivars with nitrogen supplementation were comparable. Ethanol yield was highly related to both total starch and protein content, but total starch was a better predictor of ethanol yield. There were strong negative relationships between total starch content of grain and both yield and protein content of distillers dried grains with solubles (DDGS).     

Responses of physiological parameters,grain yield,and grain quality to foliar application of potassium nitrate in two contrasting winter wheat cultivars under salinity stress

An experiment was conducted to test whether foliar application of KNO₃ on wheat in the heading stage could reduce salinity‐induced injuries, produce high grain yield, and improve grain quality. Salt‐resistant DK961 and salt‐sensitive JN17 wheat cultivars under 0 or 100 mM–NaCl conditions were foliarly watered with distilled water or a 10 mM–KNO₃ solution. The four treatments included: T₁ (CK₁), 0 mM NaCl + distilled water; T₂, 0 mM NaCl + 10 mM KNO₃; T₃ (CK₂), 100 mM NaCl + distilled water; T₄, 100 mM NaCl + 10 mM KNO₃. The results indicate that there were no differences (p > 0.05) in plant growth, grain yield, and grain quality between T₂ and T₁ in both cultivars, but these response variables were significantly lower in T₃ than in T₁. K⁺ : Na⁺ ratio, chlorophyll content, photosynthetic capacity, grain yield, flour yield, water absorbance, ash content, dough‐development time and dough‐stability time were significantly higher in T₄ than in T₃, while protein concentration, wet‐gluten concentration, and antioxidant enzyme activities were lower. Although foliar application of KNO₃ on JN17 enhanced plant growth, grain yield, and grain quality, these parameters were still lower in T₄ than in T₁. Our findings suggest that cultivating the salt‐resistant wheat cultivar combined with foliar application of KNO₃ at heading stage may alleviate salinity injuries and produce higher grain yield and better grain quality under saline conditions.     

Response to molybdenum and limestone on wheat and barley grown on podzol soils

Abstract

Molybdenum applications had no effect on the grain yield of wheat or barley. Application of limestone increased barley yield at one of the three locations and had no effect on wheat yield at any location. The Mo concentration of boot stage tissue increased with added Mo. In most cases, 0.56 kg Mo/ha applications increased the Mo concentration of boot stage tissue above 10 ppm. Increases in Mo concentration due to added Mo were generally greater at higher rates of limestone application but the Mo x limestone interaction was statistically significant only for barley at the location having the lowest pH and for wheat at the two locations with the lowest pH. Molybdenum applied as a foliar spray was found to be an effective means of increasing the Mo concentration of cereal tissues. In the case of suspected Mo deficiency in cereals, a foliar application of 0.28 kg Mo/ha should correct the problem without any ill effect from an animal nutrition standpoint.     

Epiphytic bacterial complexes in grain crops: Taxonomic composition and antagonistic properties

It is shown that the taxonomic composition of epiphytic bacteria on the leaves of wheat and barley changes in the course of vegetation. Pseudomonas and Arthrobacter predominated on young leaves and were later replaced with the ageing of the leaves by bacteria of the hydrolytic block: myxobacteria and bacilli. Representatives of myxobacteria were found as dominants on grains in wheat and barley ears as well. Thus, the replacement of eccrisotrophs, which feed on plant excreta, with the bacteria of the hydrolytic block, which are capable of destroying dying plant tissues, was observed in the phyllosphere. Bacteria of the same taxa as those from the phyllosphere of the studied crops were isolated from the rhizosphere and the soil, where only the fraction of typical pedobionts increased, such as bacilli, Arthrobacter, and Rhodococci. It was established that the bacteria that prevail on the studied agricultural plants possess antibiotic activity toward three species of phytopathogenic bacteria used in the experiment, which indicates the protective role of epiphytic prokaryotes toward host plants.     

Genotypic and Environmental Effects on Color and Discoloration Potential of Barley in Food Products

Twelve genotypes of barley, including hulled and hulless proanthocyanidin‐containing and hulled proanthocyanidin‐free types, were grown in five environments (location‐year combination) to determine the relative contribution of genotype and environment on quality traits associated with discoloration potential of barley. Barley grains were abraded and milled into flour. Protein, ash, total polyphenol content, and polyphenol oxidase (PPO) activity were determined. Brightness (L*) of abraded kernels, cooked kernels, gels, and dough sheets were determined and used as indicators of discoloration potential. Genetic factors were more important in determining total polyphenol content, PPO activity, and brightness of dough sheets and as important as environmental factors for protein and ash content. Across environments, L* of dough sheets was consistently higher in proanthocyanidin‐free barley (73–76) than in proanthocyanidin‐containing barley (59–70). Total polyphenol content of abraded grains was highest in barley grown in a dry area at 0.18%, lower in high rainfall areas at 0.13%, and lowest in irrigated areas at 0.12%. Genotype (G) by environment (E) interactions were significant for all traits, except for brightness of cooked kernels. However, the effects of the G × E interactions were generally small compared with either the genetic or the environmental effect alone and primarily due to changes in magnitude rather than in rank. Stability analyses confirmed the nature of the G × E interactions.     

灌溉频率对冬小麦产量及叶片水分利用效率的影响

为了探讨中国北方冬小麦高效节水灌溉模式,采用了3种灌溉处理:在拔节期一次灌溉120mm,在拔节期和抽穗期各灌溉60mm及在拔节期、抽穗期和灌浆期各灌溉40mm,研究了在总灌溉量为120mm的情况下,灌溉频率对冬小麦产量及叶片水分利用效率的影响.结果表明,在冬小麦的拔节期和抽穗期各灌溉60mm,显著提高乳熟期和蜡熟期旗叶...     

Relationship of Ethanol Yield to Agronomic and Seed Quality Characteristics of Small Grains

Production of fuel ethanol hinges on the availability of carbohydrate sources, with corn being the crop of choice in most areas. However, in some climatic regions, it is not feasible to grow adequate volumes of corn so other starch sources must be utilized. Here we examined various small grain crops commonly grown in the Northern Great Plains for suitability for ethanol production. Four cultivars each of the hexaploid wheat (Triticum aestivum L.) classes hard red spring (HRS), hard white spring (HWS), soft white spring (SWS), along with durum wheat (Triticum durum L.), and four spring barley (Hordeum vulgare L.) cultivars were grown in replicated plots in two environments in 2006. Agronomic and seed quality traits, along with starch content and ethanol yield over a period of 72 hr were measured on all cultivars. Agronomic yield was highest for the barley cultivars and lowest for HRS and HWS. Seed size was greatest for the durum and barley cultivars. The SWS group had the lowest protein content and the highest starch content. Starch content was highly correlated with final ethanol yield and the SWS group was highest in absolute ethanol yield. However, ethanol yield per hectare was highest for barley, with SWS ranking second, while the HRS and HWS groups had the lowest ethanol yields per hectare. The results indicate that selection for small grain ethanol yield should focus primarily upon agronomic yield at the expense of protein content. Traditional selection for high HRS and HWS milling and baking quality is not consistent with maximal ethanol yield per hectare.     

Bran Characteristics and Bread‐Baking Quality of Whole Grain Wheat Flour

Variations in physical and compositional bran characteristics among different sources and classes of wheat and their association with bread‐baking quality of whole grain wheat flour (WWF) were investigated with bran obtained from Quadrumat milling of 12 U.S. wheat varieties and Bühler milling of six Korean wheat varieties. Bran was characterized for composition including protein, fat, ash, dietary fiber, phenolics, and phytate. U.S. soft and club wheat brans were lower in insoluble dietary fiber (IDF) and phytate content (40.7–44.7% and 10.3–17.1 mg of phytate/g of bran, respectively) compared with U.S. hard wheat bran (46.0–51.3% and 16.5–22.2 mg of phytate/g of bran, respectively). Bran of various wheat varieties was blended with a hard red spring wheat flour at a ratio of 1:4 to prepare WWFs for determination of dough properties and bread‐baking quality. WWFs with U.S. hard wheat bran generally exhibited higher dough water absorption and longer dough mixing time, and they produced smaller loaf volume of bread than WWFs of U.S. soft and club wheat bran. WWFs of two U.S. hard wheat varieties (ID3735 and Scarlet) produced much smaller loaves of bread (<573 mL) than those of other U.S. hard wheat varieties (>625 mL). IDF content, phytate content, and water retention capacity of bran exhibited significant relationships with loaf volume of WWF bread, whereas no relationship was observed between protein content of bran and loaf volume of bread. It appears that U.S. soft and club wheat bran, probably owing to relatively low IDF and phytate contents, has smaller negative effects on mixing properties of WWF dough and loaf volume of bread than U.S. hard wheat bran.     

Macronutrient variation in small grain forage as related to specie and variety

Abstract

Incidence of grass tetany on small grain pastures has been related to forage Mg content and K/Ca + Mg ratio. The objective of this study was to relate P, K, Ca, Mg, and the K/Ca + Mg ratio in winter forage to specie and variety. In one year on unlimed soil with low pH, rye forage tended to be higher in P than oats, barley, or wheat. P content increased the next year on higher pH soil with less specie differences. K differed little with specie, and was higher in November than later harvests. Rye tended to be higher in Ca both years, especially in the early harvest. Percent Mg was lower for wheat the first year on the low pH soil than the other species, and percent Mg increased in all species at all harvests the next year on higher pH soil with wheat having similar Mg levels to the other species. The K/Ca + Mg ratio of wheat was higher than rye, oats, and barley on the low pH soil. Liming reduced this ratio to near 2.2 on all species. Grass tetany has been reported more likely to occur when K/Ca + Mg is over 2.2, and this study suggests rye, followed closely by oats and barley, would maintain lower ratios than wheat under conditions of low Mg availability.     

Comparison of Endoproteinases of Various Grains

Two‐dimensional isoelectric focusing (IEF) × PAGE gels were used to compare the endoproteolytic (gelatinase) activities of germinated barley with those of bread and durum wheat, rye, triticale, oat, rice, buckwheat, and sorghum. Barley was used as the standard of comparison because its endoproteinase complement has been studied previously in the greatest detail. The characteristics of the grain proteases were appraised from their migration patterns and by how they were affected by pH levels. All of the germinated grains contained multiple enzyme activities and their separation patterns and pH levels were at least similar to those of barley. The proteinases of the bread and durum wheats, rye, oat, and sorghum were most similar to those of barley, whereas the other grains provided more varied patterns. The rice and buckwheat proteinases developed much more slowly than those of the other grains. The activity patterns of the triticale resembled those of the parents, wheat and rye, but the triticale contained many more activities and higher overall proteolytic activities than any of the other species. These results should be applied to scientific or commercial procedures with caution because grains contain potent endogenous proteinase inhibitors that could inactivate some of these enzymes in various tissues or germination stages.