In Vitro Binding of Bile Acids by Rice Bran,Oat Bran,Wheat Bran,and Corn Bran

The in vitro bile acid binding by rice, oat, wheat, and corn brans was determined using a mixture of bile acids normally secreted in human bile at a physiological pH of 6.3. The objective of the study was to relate bile acid binding of cereal brans to health promoting properties. Three experiments were conducted testing substrates on an equal weight (dry matter) basis, an equal total dietary fiber (TDF) basis, and an equal TDF and equal fat basis. Each experiment was repeated to validate the results (for a total of six experiments). The relative in vitro bile acid binding of the cereal brans on an equal TDF basis considering cholestyramine as 100% bound was rice bran 51%, wheat bran 31%, oat bran 26%, and corn bran 5%. The data suggest that cholesterol lowering by rice bran appears to be related to bile acid binding. The primary mechanism of cholesterol lowering by oat bran may not be due to bile acid binding by soluble fiber. Bile acid binding did not appear to be proportional to the soluble fiber content of the cereal brans tested. Bile acid binding by wheat bran may contribute to cancer prevention and other healthful properties.     

Properties of 3-deoxyanthocyanins from sorghum

There is increasing interest in natural food colorants with functional properties. Anthocyanins from black, brown (containing tannins), and red sorghums were characterized by spectrophotometric and HPLC techniques. The antioxidant activity and pH stability of the anthocyanins were also determined. Sorghum brans had 3-4 times higher anthocyanin contents than the whole grains. Black sorghum had the highest anthocyanin content (average = 10.1 mg/g in bran). The brown and red sorghum brans had anthocyanin contents of 2.8-4.3 mg/g. Only 3-deoxyanthocyanidins were detected in sorghum. These compounds are more stable to pH-induced color change than the common anthocyanidins and their glycosides. Additionally, crude sorghum anthocyanin extracts were more stable than the pure 3-deoxyanthocyanidins. The antioxidant properties of the 3-deoxyanthocyanidins were similar to those of the anthocyanins. Pigmented sorghum bran has high levels of unique 3-deoxyanthocyanidins, which are stable to change in pH and have a good potential as natural food pigments.     

Decorticating sorghum to concentrate healthy phytochemicals

The growing prominence of nutrition-related health problems demands strategies that explore nontraditional natural ingredients to expand healthy food alternatives. Specialty sorghums were decorticated using a tangential abrasive dehulling device (TADD) to remove successive bran layers, which were collected at 1 min intervals and analyzed for phenols, tannins, 3-deoxyanthocyanins, dietary fiber, and antioxidant activity. The first two bran fractions had the highest levels of phenols and antioxidant activity (3-6 times as compared to whole grain). Brown (tannin-containing) and black sorghums had at least 10 times higher antioxidant activity than white sorghum or red wheat brans. Black sorghums had the highest 3-deoxyanthocyanin content (up to 19 mg/g bran). Dietary fiber in sorghum brans ranged between 36 and 45%, as compared to 48% for wheat bran. Specialty sorghum brans are rich in valuable dietary components and present promising opportunities for improving health attributes of food.     

Calcium-binding capacities of different brans under simulated gastrointestinal pH conditions. In vitro study with (45)Ca

The present study was performed to investigate calcium-binding characteristics of different brans under simulated gastrointestinal pH conditions and to explore the significance of dietary fiber, oxalate, and phytate for calcium binding. Different brans (rice, rye, soy, fine wheat, coarse wheat, and oat) and CaCl(2) solution containing (45)Ca were incubated at 37 degrees C at gastric pH (2.2) followed by buffering steps of 1 degree from pH 3.0 to pH 8.0. Total calcium binding and calcium-binding capacity of the pH 2.2 soluble bran fraction were determined. Additionally, oxalate and phytate contents of brans and solubility profiles of phytic acid were investigated. Calcium-binding capacities of brans showed a clear pH dependence. At gastric pH calcium binding was low in all brans, ranging from 0.022 to 0.040 mmol of calcium/g of bran. Soy bran, nearly phytate-free, showed higher binding values up to pH 4.0 and lower values between pH 5.0 and 8.0. In all other brans, binding values increased strongly with increasing pH in the quantitative order rice bran > coarse wheat bran > fine wheat bran > rye bran > oat bran. The solubility profiles indicate that in the cases of rye, wheat, and rice bran phytate accounts for 70-82% of their total calcium-binding capacities. The results suggest that dietary fiber makes no important contribution to calcium binding, except for soy and oat brans. Oxalate plays only a minor role in calcium binding by brans.     

REVIEW: Cereal Carbohydrates and Colon Health

Providing balanced energy and nutrients for microbiota growth is essential for the maintenance of the colon ecosystem, and dietary fiber (DF) fermentation, particularly butyrogenic fermentation, augments colon health. Cereal DF, which are the complex carbohydrates of cereal grains that escape small intestine digestion and function either as substrate for colonic fermentation or as bulking material, are a dietary measure to mitigate the occurrence of certain colonic diseases, and perhaps to some degree act as therapeutic agents. In developed Western countries, as well as in many developing countries, colon cancer is one of the major causes for premature death and disability, and inflammatory bowel disease and other colonic disorders have become serious health issues. The function of DF in colon health is mediated through its physicochemical properties (e.g., water‐holding for laxative effect) or effect on colon microbiota (e.g., leading to immune regulation), as well as through colonic fermentation products, principally the short chain fatty acids (SCFA) of acetate, propionate, and butyrate. Due to the chemical diversity and complexity of DF and because not all DF materials function equally, new developments in DF fermentation behavior (pattern and end product profile) will be reviewed from a structure‐function viewpoint. The effect of cereal DF, mainly nonstarch cereal polysaccharides and resistant starch on colonic microbiota, fermentation products of SCFA, microbiota modulation, as well as on colon health will be summarized.     

Introduction to the Focus Issue

Cereal biomacromolecules are an important source not just of calories but also of functional ingredients in foods and as raw materials for biodegradable nonfood applications. Their important role is evidenced by an ever‐increasing number of peer‐reviewed publications on these topics. Current research is increasingly focused on understanding the fine structure of the macromolecules and their interactions with other ingredients within a food matrix for their impact on health. Furthermore, these learnings about the fine structure and interactions have relevance to functionality in nonfood applications. This focus issue attempts to summarize the state of the knowledge and research gaps related to the three major biomacromolecules in cereals: starch, proteins, and nonstarch polysaccharides (dietary fiber). Click on Current Issues on left and then July/August 2013 to view the articles in this Focus Issue. (From the Mobile site, go to the July/August 2013 issue.)     

Effect of Extrusion on Hypocholesterolemic Properties of Rice,Oat, Corn,and Wheat Bran Diets in Hamsters

Brans from rice, oats, corn, and wheat were cooked in a twin-screw extruder at either high or low energy input, and their cholesterol-lowering effects were compared with those of unprocessed brans when fed to four-week-old male golden Syrian hamsters (n = 10 per treatment) for three weeks. Peanut oil was added to oat, corn, and wheat bran during the extrusion process to match the oil content of rice bran. Diets contained 10% total dietary fiber, 10.3% fat, 3% nitrogen, and 0.3% cholesterol. Plasma and liver cholesterol and total liver lipids were significantly lower with low-energy extruded wheat bran compared with unprocessed wheat bran. Extrusion did not alter the hypocholesterolemic effects of rice, oat, or corn brans. Plasma and liver cholesterol levels with corn bran were similar to those with oat bran. Relative cholesterol-lowering effects of the brans, determined with pooled (extruded and unextruded) bran data, were rice bran > oat bran > corn bran > wheat bran. Rice bran diets resulted in significantly lower levels of total plasma cholesterol and very low density lipoprotein cholesterol compared with all other brans. Total liver cholesterol and liver cholesterol concentrations (mg/g) were significantly lower with high-energy extruded rice bran compared with the cellulose control group. Plasma cholesterol and total liver cholesterol values with low-energy extruded wheat bran were similar to those with rice bran (unextruded or extruded) diets. Lowered cholesterol with rice bran diets may result in part from greater lipid and sterol excretion with these diets. Results with low-energy extruded wheat bran suggest that this type of processing may improve the potential for lowering cholesterol with wheat bran products.     

Growth-Inhibitory Effects of Pigmented Rice Bran Extracts and Three Red Bran Fractions against Human Cancer Cells: Relationships with Composition and Antioxidative Activities

We determined the phenolic, anthocyanin, and proanthocyanidin content of three brown, purple, and red rice brans isolated from different rice varieties using HPLC-PDA with the aid of 27 standards of known structure and matching unknown peaks to a spectral library of known compounds. Antioxidative capacities were determined by DPPH and ORAC and cell-inhibiting effects using an MTT assay. Based on the calculated IC(50) values, the light-brown bran had no effect, the purple bran exhibited a minor effect on leukemia and cervical cancer cells, and the red bran exhibited strong inhibitory effects on leukemia, cervical, and stomach cancer cells. High concentrations of protocatechuic acid and anthocyanins in purple bran and proanthocyanidins in red bran were identified. The red bran was further fractionated on a Sephadex column. Fraction 3 rich in proanthocyanidin oligomers and polymers had the greatest activity. Red bran has the potential to serve as a functional food supplement for human consumption.     

Sorghum Bran as a Potential Source of Kafirin

Sorghum bran, a coproduct of sorghum dry milling, could be a source of protein for industrial applications. Condensed tannin‐free red and white sorghum samples were decorticated by abrasion until ≈10 or 25% grain by weight was removed. Kafirin was then extracted from the milling fractions using an aqueous ethanol based solvent system. The brans were darker and considerably higher in protein and fat compared with the whole grain flours and decorticated grain flours, with the 25% bran having higher protein than the 10% bran. This is due to increased contamination of the bran with protein‐dense, corneous endosperm. The protein extracted from all the milling fractions, including the brans, was pure kafirin. However, the yield of kafirin from the brans (15.9–26.7% of total protein present) was somewhat lower than that from whole grain and decorticated grain flours (45.0–57.9% of total protein present), due to the fact that kafirin is located solely in the endosperm. Also, the kafirin from bran was more contaminated with fat, polyphenols, and other substances, and more highly colored, particularly the kafirin from red sorghum. Thus, sorghum bran could be used as a source of kafirin but further purification steps may be necessary.     

Effects of Brans from Specialty Sorghum Varieties on In Vitro Starch Digestibility of Soft and Hard Sorghum Endosperm Porridges

Brans of specialty sorghum varieties (high tannin, black, and black with tannin) were used to investigate the effects of sorghum phenolic compounds on starch digestibility of soft and hard sorghum endosperm porridges. Endosperms of varieties with the highest and lowest grain hardness index were mixed with brans of specialty sorghum varieties in the ratio of 85:15 and cooked into porridges with distilled water using a Rapid Visco Analyzer. Brans of condensed tannin containing sorghum varieties (high‐tannin and black with tannin sorghums) significantly (P < 0.05) decreased starch digestibility and estimated glycemic index (EGI) and increased resistant starch (RS) content of endosperm porridges. However, the addition of phenolic‐rich tannin‐free (mostly anthocyanins) black sorghum bran significantly (P < 0.05) increased starch digestibility and EGI but did not affect RS content of endosperm porridges. The disparate effects with black bran may, in part, result from its larger particle size and different bran structure compared with other sorghum varieties evaluated. Thus, our study showed that not only presence of phenolic compounds in the brans but also structural differences of specialty sorghum brans can have significant effects on starch digestibility.     

Evaluation of antioxidant capacity of cereal brans

Several oat brans (crunchy oat bran, oat bran alone, and oat breakfast cereal) and wheat brans (wheat bran alone, wheat bran powder, wheat bran with malt flavor, bran breakfast cereal, tablet of bran, and tablet of bran with cellulose) used as dietary fiber supplements by consumers were evaluated as alternative antioxidant sources (i) in the normal human consumer, preventing disease and promoting health, and (ii) in food processing, preserving oxidative alterations. Products containing wheat bran exhibited higher peroxyl radical scavenging effectiveness than those with oat bran. Wheat bran powder was the best hydroxyl radical (OH*) scavenger. In terms of hydrogen peroxide (H2O2) scavenging, wheat bran alone was the most effective, while crunchy oat bran, oat bran alone, and oat breakfast cereal did not scavenge H2O2. The shelf life of fats (obtained by the Rancimat method for butter) increased most in the presence of crunchy oat bran. When the antioxidant activity during 28 days of storage was measured by the linoleic acid assay, all of the oat and wheat bran samples analyzed showed very good antioxidant activities. The Trolox equivalent antioxidant capacity (TEAC) assay was used to provide a ranking order of antioxidant activity. The wheat bran results for TEAC (6 min), in decreasing order, were wheat bran powder > wheat bran with malt flavor > or = wheat bran alone > or = bran breakfast cereal > tablet of bran > tablet of bran with cellulose. The products made with oat bran showed lower TEAC values. In general, avenanthramide showed a higher antioxidant level than each of the following typical cereal components: ferulic acid, gentisic acid, p-hydroxybenzoic acid, protocatechuic acid, syringic acid, vanillic acid, vanillin, and phytic acid.     

Processing of novel elevated amylose wheats: functional properties and starch digestibility of extruded products

Different types of novel wheat lines with different starch contents and amylose/amylopectin ratios, relating to defined alterations in the number and activity of starch synthase IIa genes, were processed by pilot-plant extrusion. Two types of products were produced: pure wholemeal products and breakfast cereals made from wholemeal/maize blends. Lower apparent shear viscosity was obtained in the extruder with lower starch content and higher amylose/amylopectin ratio flours (SSIIa-deficient line). The bulk density of the products decreased with increasing extrusion temperature and was always higher for the triple-null line. The bulk density was not completely explained by the melt shear viscosity, suggesting the importance of the fillers (fibers, brans) in the process of expansion and structure acquisition. The different mechanical properties were explained by the density and by the material constituting the cell walls. Enzyme-resistant starch (RS) content and hydrolysis index (HI) were not correlated to the extrusion temperature, but RS was higher in pure wholemeal products and in the SSIIa-deficient line. These results are discussed in terms of starch molecular architecture and product microstructure.     

In Vitro Binding of Bile Acids by Rice Bran,Oat Bran,Barley and β‐Glucan Enriched Barley

The in vitro bile acid binding by rice bran, oat bran, dehulled barley, and β‐glucan enriched barley was determined using a mixture of bile acids at a duodenal physiological pH of 6.3. Six treatments and two blank incubations were conducted testing substrates on an equal protein basis. The relative in vitro bile acid binding of the cereal brans on an equal total dietary fiber (TDF) and insoluble dietary fiber (IDF) basis considering cholestyramine as 100% bound was rice bran 45 and 49%; oat bran 23 and 30%; dehulled barley 33 and 57%; and β‐glucan enriched barley 20 and 40%, respectively. Bile acid bindings on equal protein basis for the respective cereals were 68, 26, 41, and 49%. Bile acid binding by rice bran may account to a great extent for its cholesterol‐lowering properties, while bile acid binding by oat bran suggests that the primary mechanism of cholesterol lowering by oat bran is not due to the bile acid binding by its soluble fiber. Bile acid binding was not proportional to the soluble fiber content of the cereal brans tested. Except for dehulled barley, bile acid binding for rice bran, oat bran, and β‐glucan enriched barley appear to be related to their IDF content. Highest relative bile acid binding values for rice bran and β‐glucan enriched barley were observed on an equal protein basis, whereas highest values for dehulled barley were based on IDF. Data suggest that of all four cereals tested, bile acid binding may be related to IDF or protein anionic, cationic, physical and chemical structure, composition, metabolites, or their interaction with active binding sites.     

Antioxidative, antimutagenic, and anticarcinogenic activities of rice bran extracts in chemical and cell assays

Ethanol-water (70:30 v/v) extracts from rice brans removed from seeds of two blackish-purple pigmented (Sanhaehyanghyulla and Suwon 415) and one nonpigmented (Chuchung) brown rice cultivars were evaluated for antioxidative, anti-tumor-promoting, and anticarcinogenic activities in chemical assays and in mammalian cells (human leukemia HL-60, marmoset B lymphoblastoid B95-8, and Chinese hamster V79 lung cells) by the following tests: inhibition of xanthine oxidase activity; chelation of ferrous ions; reduction of potassium ferricyanide; scavenging of superoxide anions, hydroxyl radicals, and intracellular peroxides; inhibition of 4-nitroquinoline N-oxide-induced mutagenesis; and inhibition of phorbol ester-induced tumor promotion. The extracts from the pigmented rice seeds had generally higher activities in all tests than did the extract from the nonpigmented variety. The results suggest that brans from pigmented rice varieties may provide a source of new natural antioxidants and anticarcinogens and that such rice cultivars with high antioxidative potential also provide a genetic resource for the development of new, improved rice cultivars that may make it possible to enhance both the nutritional and medical value of rice-based diets.     

Esterase activity able to hydrolyze dietary antioxidant hydroxycinnamates is distributed along the intestine of mammals.

Hydroxycinnamic acids are effective antioxidants and are abundant components of plant cell walls, especially in cereal bran. For example, wheat and rye brans are rich sources of the hydroxycinnamates ferulic acid, sinapic acid, and p-coumaric acid. These phenolics are part of human and animal diets and may contribute to the beneficial effects derived from consumption of cereal bran. However, these compounds are ester linked to the main polymers in the plant cell wall and cannot be absorbed in this complex form. The present work shows that esterases with activity toward esters of the major dietary hydroxycinnamates are distributed throughout the intestinal tract of mammals. In rats, the cinnamoyl esterase activity in the small intestine is derived mainly from the mucosa, whereas in the large intestine the esterase activity was found predominantly in the luminal microflora. Mucosa cell-free extracts obtained from human duodenum, jejunum, and ileum efficiently hydrolyzed various hydroxycinnamoyl esters, providing the first evidence of human cinnamoyl esterase(s). This study first demonstrates the release by human colonic esterase(s) (mostly of microbial origin) of sinapic acid and p-coumaric acid from rye and wheat brans. Hydrolysis by intestinal esterase(s) is very likely the major route for release of antioxidant hydroxycinnamic acids in vivo.     

Impact of Solid‐State Fermentation (Aspergillus oryzae) on Functional Properties and Mineral Bioavailability of Black‐Eyed Pea (Vigna unguiculata) Seed Flour

Solid‐state fermentation (SSF) represents a technological alternative feature for a great variety of legumes and cereals to improve their functional and nutritional properties. Iron and zinc deficiencies are major health concerns as a public health problem. Therefore, the present investigation was carried out to assess the consequences of SSF on functional properties and in vitro bioavailability of minerals through Caco‐2 cells. Fungal strain Aspergillus oryzae (generally recognized as safe) was used for SSF. The effect of SSF on the functional properties (bulk density, water‐ and oil‐binding capacities, emulsion activity and stability, and foaming capacity and stability) of a black‐eyed pea flour sample was evaluated. SSF significantly (P < 0.05) decreased the bulk density of black‐eyed pea flour; however, significant (P < 0.05) improvement was observed in other functional properties. An unfermented flour sample showed significantly (P < 0.05) decreased iron and zinc bioavailability and digestibility compared with that of the SSF flour sample. SSF significantly increased iron and zinc transport and retention through Caco‐2 cells. Significantly increased ferritin content was also observed in the fermented flour sample compared with that of unfermented flour samples.     

Whole Grains and Digestive Health

Whole grains contain all parts of the grain: the endosperm, germ, and bran. Whole grains are rich in fermentable carbohydrates that reach the gut: dietary fiber, resistant starch, and oligosaccharides. Most research that supports the importance of grains to gut health was conducted with isolated fiber fractions, rather than whole grains. Whole grains are an important source of dietary fiber and grain fibers such as wheat, oats, barley, and rye increase stool weight, speed intestinal transit, get fermented to short chain fatty acids, and modify the gut microflora. Wheat bran is particularly effective in increasing stool weight; wheat bran increases stool weight by a ratio of 5:1. In contrast, many novel fibers that are easily incorporated into beverages and foods increase stool weight only on a ratio of 1:1. In vitro fermentation studies with whole grains have been published. Carbohydrates of oat bran (rich in β‐glucan) were consumed by bacteria faster than those of rye and wheat brans (rich in arabinoxylan). Grain fibers were fermented more slowly than inulin, causing less gas production. Wheat is particularly high in fructo‐oligosaccharides, while wheat germ is high in raffinose oligosaccharides. Some in vivo studies show the prebiotic potential of whole grains. Whole grain breakfast cereal was more effective than wheat bran breakfast cereal as a prebiotic, increasing fecal bifidobacteria and lactobacilli in human subjects. Wheat bran consumption increased stool frequency. Thus, the gut enhancing effects of cereal fibers are well known. Limited data exist that whole grains alter gut health.     

Composition,Nutritional Value,Functionality, Processing,and Novel Food Uses of Pulses and Pulse Ingredients

Pulses, the dry edible seeds of plants in the legume family, include field pea, dry bean, lentil, chickpea, and fababean. The contemporary definition of pulses excludes oilseed legumes and legumes consumed in immature form. Pulses have been nourishing people around the world for thousands of years and are well known as a rich, sustainable source of protein that is high in lysine and therefore complementary to protein from cereals. They also are good sources of energy and dietary fiber, are low in fat, and contain significant levels of vitamins, minerals, and other micronutrients and bioactives. Owing to its intermediate amylose content, starch from pulses is digested more slowly than are most cereal and tuber starches. Whole and split pulses and pulse flours also exhibit relatively high levels of type 1 resistant starch. As a result, the consumption of pulses is beneficial to the management of type 2 diabetes, metabolic syndrome, and obesity, is associated with a reduced risk of cardiovascular disease and cancer, and contributes to overall health and wellness. Pulses are used in whole or dehulled form in canned goods, sweets, soups, and pastes, whereas pulse flours are becoming common ingredients in a wide variety of food and pet food products such as baked goods, pasta and noodles, biscuits, and condiments. There is considerable interest currently in dry and wet fractionation of pulses into starch, protein, and fiber concentrates for use in both food and nonfood applications. As consumers are becoming increasingly health conscious and focused on a wellness‐oriented lifestyle, they are demanding tasty and convenient food products that are plant‐based and provide both nutritional and health benefits. In recent years, interest in the use of pulses and their ingredients in food formulation has grown tremendously owing to their nutritional and health benefits and unique functionality, a rise in the incidence of food allergies, and the availability of novel processing technologies. The United Nations declared 2016 as the International Year of Pulses, which was celebrated through the hosting of scientific and educational activities worldwide, all aimed at increasing consumer awareness of the benefits of pulse consumption and of the role of pulses in sustainable crop production systems. The ultimate goal was increased production and consumption of pulses in both developed and developing countries. This focus issue of Cereal Chemistry captures current research related to pulse composition, processing technologies, nutritional and functional attributes of pulse ingredients, impacts of processing on composition and functionality, potential health benefits, and novel food applications. It also includes review articles on composition, nutritional value and health benefits, traditional and new food uses, determination of protein nutritional quality, evaluation of cooking time, effects of processing on antinutrients, and flavor aspects of ingredients.     

Quantification and In Vitro Bioaccessibility of Selenium from Osborne Fractions of Selenium‐Rich Cereal Grains

Cereal crops cultivated in the seleniferous belt of Punjab, India, were observed to hyperaccumulate a significantly high concentration of selenium (20–123 µg/g). Selenium concentration (µg/g) in storage proteins of wheat, maize, and rice, namely, albumin (401, 280, and 29, respectively), globulin (264, 192, and 242, respectively), glutelin (563, 359, and 178, respectively), and prolamin (629, 339, and 257, respectively) indicated variable selenium levels, with prolamin contributing significantly higher levels of selenium when compared with other proteins with reference to the total concentration of the protein fraction. The simulated gastric and gastrointestinal digestion studies indicated better accessibility of selenium during intestinal digestion, with variability across proteins and cereal types. The observations provide an insight into the bioavailability of selenium in selenium‐rich cereal grains, used in the study, and their potential use as source for selenium supplementation to deficient populations, or as “bioactive” selenium‐rich nutraceutical blends for health benefits.     

影响禾谷类作物籽实营养素含量的遗传因素分析

禾谷类作物是最重要的粮食作物,为人类提供了必需的营养物质,淀粉、脂肪、蛋白质、维生素和矿物质作为谷物的主要营养素,其含量是培育健康谷物的关键。为给育种研究中有效提升禾谷类籽实的营养品质及谷物的有效利用提供参考,并为培育更具全面营养的谷物提供理论依据,从饮食源头上为人类健康保驾护航。本文基于近年来相关文献资料的梳理归纳,对几种主要的禾谷类作物小麦、大麦、燕麦、水稻和玉米中的几种主要营养素含量进行比较分析,对影响这些营养物质含量和品质的遗传因素进行分析总结,认为小麦、大麦、燕麦、水稻、玉米等禾谷类籽实所含的各类营养物质有较大差异,不同物种遗传背景的差异是导致不同禾谷类籽实营养物质差异的根本原因,而在进化过程中基因突变的平行性又是导致禾谷类籽实中相同营养元素被同类基因编码调控的直接原因。