Discriminating Oat and Groat Kernels from Other Grains Using Near‐Infrared Spectroscopy

Oats and groats can be discriminated from other grains such as barley, wheat, rye, and triticale (nonoats) with near‐infrared spectroscopy. The two instruments tested herein were the manual version of the United States Department of Agriculture–Agricultural Research Service single‐kernel near‐infrared (SKNIR) instrument and the automated QualySense QSorter Explorer high‐speed sorter, both used in similar near‐infrared spectral ranges. Three linear discriminate self‐prediction models were developed: 1) oats versus groats + nonoats, 2) oats + groats versus nonoats, and 3) groats versus nonoats. For all three models, the SKNIR instrument showed high correct classification of oats or groats (94.5–100%), which was similar to results of the QSorter Explorer at 95.0–99.4%. The amount of nonoats that were misclassified as oats or groats was low for both instruments at 0–0.2% for the SKNIR instrument and 0.8–3.7% for the QSorter Explorer. Linear discriminate models from independent prediction and validation sets yielded classification accuracies of 91.6–99.3% (SKNIR) and 90.5–97.8% (QSorter Explorer). Small differences in classification accuracy were attributed to processing speeds between the two instruments: 3 kernels/s for the SKNIR instrument and 35 kernels/s for the QSorter Explorer. This indicated that both instruments are useful for quantifying grain sample compositions of oat and groat samples and that both could be useful tools for meeting consumer demand for gluten‐free or low‐gluten products. Discrimination between grains will help producers and manufacturers meet various regulatory requirements. Examples include requirements such as those from the U.S. Food and Drug Administration and the Commission of European Communities, in which gluten‐free oats or other products can only be labeled as nongluten if they contain gluten at less than 20 ppm, the established safe consumption limit for people with celiac disease. The QSorter Explorer is currently being used to meet these requirements.     

Chemical and Physical Characteristics of Proso Millet (Panicum miliaceum)‐Based Products

Celiac disease and gluten sensitivities, as well as obesity and overweight‐related disorders, have led to the investigation of gluten‐free grains and development of new food products. To address this, refined proso millet and refined corn (control), both gluten‐free grains, were used to produce four different product types (muffin, couscous, extruded snack, and porridge). The products contained four different grain combinations (100% proso millet, 75% proso millet/25% corn, 25% proso millet/75% corn, and 100% corn). All products were evaluated for their nutritional composition, in vitro starch digestibility, and expected glycemic index (eGI). Products made with refined proso millet had increased protein (7.6–11.3%), lipid (1.2–6.1%), fiber (7.0–8.8%), and phenolic content (323.5–425 μg/g) compared with those incorporating corn flour (2.5–9.0%, 0.8–4.0%, 2.1–4.1%, and 213–315 μg/g, respectively). As the proso millet content increased, the eGI decreased significantly (P < 0.05). Products made from refined proso millet appear to be good candidates for producing low‐GI, gluten‐free foods.     

Impact of Baking on Vitamin E Content of Pseudocereals Amaranth,Quinoa, and Buckwheat

The aim of this study was to analyze the vitamin E composition of amaranth, quinoa, and buckwheat pseudocereals. The method used consisted of a one‐step extraction with hexane followed by normal‐phase high‐performance liquid chromatography (NP‐HPLC) coupled with a fluorescence detector. This method afforded complete separation of all vitamin E compounds present. In addition, vitamin E stability following high‐temperature processing such as breadmaking was also studied. The vitamin E composition differed significantly from grain type to grain type, and highest vitamin E content (expressed as α‐tocopherol equivalents) was found in quinoa grains, followed by amaranth and buckwheat (24.7, 15.4, and 6.3 μg/g respectively). None of the pseudocereal grains contained tocotrienols, which were only detected in wheat grains in minor quantities. Vitamin E recovery following breadbaking was high (70–93%) and gluten‐free breads containing pseudocereal had significantly higher vitamin E content compared with the gluten‐free control. Amaranth, quinoa, and buckwheat grains proved to be good sources of vitamin E and may be used as ingredients in gluten‐free products for improving vitamin E content and thus overall nutritional quality.     

Nonenzymatic Browning During Storage of Infant Cereals

The browning indicators furosine and color were determined in infant cereals and infant cereals containing powdered milk to evaluate the utility of these parameters for monitoring storage. Studies were made on seven infant cereal samples including both gluten and gluten‐free products. Samples were stored under laboratory conditions at 28°C for four or 16 weeks; or under modified water activity conditions at 25°C or 55°C for one, two, three, or four weeks; or under industrial conditions in air or nitrogen atmospheres at 32°C or 55°C for one, three, six, or 12 months. Furosine levels increased during the storage of infant cereals containing powdered milk under all time, temperature, and water activity (a_w) conditions assayed, except drastic conditions (55°C, a_w = 0.65). Color values increased in infant cereals with gluten (7‐cereal and 8‐cereal samples), regardless of milk content, when they were stored under drastic conditions (55°C or 25°C with normal or modified water activity). However, the gluten‐free infant cereals (rice‐corn and rice‐corn‐soy samples) that have a characteristic yellow color showed no increase in color during storage. The extent of the Maillard reaction was greatest in the infant cereals that included milk in their formulation.     

Mixograph Responses of Gluten and Gluten‐Fortified Flour for Gluten Produced by Cold‐Ethanol or Water Displacement of Starch from Wheat Flour

The total protein of gluten obtained by the cold‐ethanol displacement of starch from developed wheat flour dough matches that made by water displacement, but functional properties revealed by mixing are altered. This report characterizes mixing properties in a 10‐g mixograph for cold‐ethanol‐processed wheat gluten concentrates (CE‐gluten) and those for the water‐process concentrates (W‐gluten). Gluten concentrates were produced at a laboratory scale using batter‐like technology: development with water as a batter, dispersion with the displacement fluid, and screening. The displacing fluid was water for W‐gluten and cold ethanol (≥70% vol, ‐12°C) for CE‐gluten. Both gluten types were freeze‐dried at ‐10°C and then milled. Mixograms were obtained for 1) straight gluten concentrates hydrated to absorptions of 123–234%, or 2) gluten blended with a low protein (9.2% protein) soft wheat flour to obtain up to 16.2% total protein. The mixograms for gluten or gluten‐fortified flour were qualitatively and quantitatively distinguishable. We found differences in the mixogram parameters that would lead to the conclusion of greater stability and strength for CE‐gluten than for W‐Gluten. Differences between the mixograms for these gluten types could be markedly exaggerated by increasing the amount of water to the 167–234% range. Mixograms for evaluation of gluten have not been previously reported in this hydration range. Mixograms for fortification suggest that less CE‐gluten than W‐gluten would be required for the same effect.     

Observations on the Quality Characteristics of Waxy (Amylose‐Free) Winter Wheats

Previous investigations have suggested waxy (amylose‐free) wheats (Triticum aestivum L.) possess weak gluten properties and may not be suitable for commercial gluten extraction. This limitation could prevent the use of waxy wheat as a source of unique starch, because gluten is a by‐product of the wheat starch purification process. Fifty waxy wheat lines were used to determine the extent to which gluten protein and other grain quality related traits might vary and, consequently, allow the development of waxy wheat with acceptable gluten properties. Among the waxy lines, significant variation was observed for all measured quality traits with the exception of flour protein concentration. No waxy entries statistically equaled the highest ranking nonwaxy entry for grain volume weight, falling number, flour yield, or mixograph mix time. No waxy lines numerically exceeded or equaled the mean of the nonwaxy controls for falling number, flour yield, or mixograph mix time. For grain and flour protein related variables, however, many waxy lines were identified well within the range of acceptability, relative to the nonwaxy controls used in this study. Approximately 50% of the waxy lines did not differ from the highest ranking nonwaxy cultivar for grain and flour protein concentrations. Forty‐three (86%) of the tested waxy lines were not sig‐nificantly different from the nonwaxy line with the highest mixograph mixing tolerance, 22/50 (44%) of the waxy wheat lines did not differ from the highest ranking nonwaxy line in gluten index scores, and 17/50 (34%) did not differ from the highest ranking nonwaxy line in extracted wet gluten. All waxy experimental lines produced gluten via Glutomatic washing. The quality of the gluten, as measured both by mixograph and gluten index, varied widely among the waxy lines tested. These observations suggest that weak gluten is not a natural consequence of the waxy trait, and waxy cultivars with acceptable gluten properties can be developed.     

Degradation of gluten by proteases from dry and germinating wheat (Triticum durum) seeds: An in vitro approach to storage protein mobilization

Vital gluten was used as an ideal substrate to investigate the role of some proteases in storage protein degradation. Aspartic proteinase and carboxypeptidase were identified as endogenous enzymes adsorbed on gluten and their optimum pH values determined. SDS-PAGE of soluble products released by gluten digestion revealed that the activity of these proteases plays a minor role in protein mobilization, whereas cysteine proteinase, purified from wheat seeds at the fourth day of germination, is extremely effective, producing a remarkable protein degradation in short times. Synergistic effects of aspartic and cysteine proteinase were not observed. Spin labeling of the sulfhydryl groups of gluten proteins enabled a comparative EPR investigation of the consequences of proteolytic degradation on gluten elasticity. It was found that storage protein mobilization brings a loss of elasticity to the polymeric network of gluten, which is particularly marked when the hydrolysis is performed by cysteine proteinase.     

Textural Comparisons of Gluten‐Free and Wheat‐Based Doughs,Batters, and Breads

Studies were conducted with two newly developed gluten‐free bread recipes. One was based on corn starch (relative amount 54), brown rice (25), soya (12.5), and buckwheat flour (8.5), while the other contained brown rice flour (50), skim milk powder (37.5), whole egg (30), potato (25), and corn starch (12.5), and soya flour (12.5). The hydrocolloids used were xanthan gum (1.25) and xanthan (0.9) plus konjac gum (1.5), respectively. Wheat bread and gluten‐free bread made from commercial flour mix were included for comparison. Baking tests showed that wheat and the bread made from the commercial flour mix yielded significantly higher loaf volumes (P < 0.01). All the gluten‐free breads were brittle after two days of storage, detectable by the occurrence of fracture, and the decrease in springiness (P < 0.01), cohesiveness (P < 0.01), and resilience (P < 0.01) derived from texture profile analysis. However, these changes were generally less pronounced for the dairy‐based gluten‐free bread, indicating a better keeping quality. Confocal laser‐scanning microscopy showed that the dairy‐based gluten‐free bread crumb contained network‐like structures resembling the gluten network in wheat bread crumb. It was concluded that the formation of a continuous protein phase is critical for an improved keeping quality of gluten‐free bread.     

The Biochemical Basis of Celiac Disease

Celiac disease (CD) is an inflammatory disorder of the upper small intestine triggered by the ingestion of wheat, rye, barley, and possibly oat products. The clinical feature of CD is characterized by a flat intestinal mucosa with the absence of normal villi, resulting in a generalized malabsorption of nutrients. The prevalence of CD among Caucasians is now thought to be in a range of 1:100–300. There is a strong genetic association with human leukocyte antigens (HLA‐)DQ2 and DQ8 and currently unknown non‐HLA genes. During the last decade, intense biochemical studies have contributed to substantial progress in understanding the general principles that determine the pathogenesis of CD. The precipitating factors of toxic cereals are the storage proteins, termed gluten in the field of CD (gliadins and glutenins of wheat, secalins of rye, and hordeins of barley). There is still disagreement about the toxicity of oat avenins. The structural features unique to all CD toxic proteins are sequence domains rich in Gln and Pro. The high Pro content renders these proteins resistant to complete proteolytic digestion by gastrointestinal enzymes. Consequently, large Pro‐ and Gln‐rich peptides are cumulated in the small intestine and reach the subepithelial lymphatic tissue. Depending on the amino acid sequences, these peptides can induce two different immune responses. The rapid innate response is characterized by the secretion of the cytokine interleukin‐15 and the massive increase of intraepithelial lymphocytes. The slower adaptive response includes the binding of gluten peptides (native or partially deamidated by tissue transglutaminase) to HLA‐DQ2 or ‐DQ8 of antigen presenting cells and the subsequent stimulation of T‐cells accompanied by the release of proinflammatory cytokines such as interferon‐γ and the activation of matrix metalloproteinases. Both immune responses result in mucosal destruction and epithelial apoptosis. Additionally, stimulated T‐cells activate B‐cells that produce serum IgA and IgG antibodies against gluten proteins (antigen) and tissue transglutaminase (autoantigen). These antibodies can be used for noninvasive screening tests to diagnose CD. The current essential therapy of CD is a strict lifelong adherence to gluten‐free diet. Dietetic gluten‐free foods produced for CD patients underlie the regulations of the Codex Alimentarius Standard for Gluten‐Free Foods. The “Draft Revised Codex Standard” edited in March 2006 proposes a maximum level of 20 mg of gluten/kg for naturally gluten‐free foods (e.g., based on rice or corn flour) and 200 mg/kg for foods rendered gluten‐free (e.g., wheat starch). Numerous analytical methods for gluten determination have been developed, mostly based on immunochemical assays, mass spectrometry, or polymerase chain reaction. So far, only two enzyme‐linked immunosorbent assays have been successfully ring‐tested and are commercially available. During the last decade, future strategies for prevention and treatment of CD have been proposed. They are based on the removal of toxic epitopes by enzymatic degradation or gene engineering and on blocking parts of the immune system. However, any alternative treatment should have a safety profile competitive with gluten‐free diet.     

REVIEW: Effects of Germination on the Nutritional Profile of Gluten‐Free Cereals and Pseudocereals: A Review

There are a growing number of individuals diagnosed with food allergies and intolerances. Gluten, in particular, is avoided by many individuals because of celiac disease, gluten intolerance, and gluten ataxia. Individuals with allergies, intolerances, or both follow strict diets, but there is concern that these individuals may be at risk of several nutrient deficiencies, including decreased calcium, iron, B vitamins, and fiber. To prevent deficiencies, alternative sources of these nutrients must be provided. Gluten‐free cereals and pseudocereals such as amaranth, buckwheat, corn, millet, rice, sorghum, and quinoa can be excellent sources of vitamins, minerals, fiber, and other important nutrients. Germination of these edible seeds has been shown to further increase nutrient content and to reduce antinutrients. Their use to naturally fortify and enrich gluten‐free foods has great potential. Although there are many benefits to germinated seeds in food, more research must be done to improve texture and sensory properties to gain wider consumer acceptance. A review of germination of gluten‐free cereals and pseudocereals and its effect on their nutritional profile is presented.     

Macromolecular and Micronutrient Profiles of Sprouted Chickpeas to Be Used for Integrating Cereal‐Based Food

Pulse flour may be used to improve nutritional traits of gluten and gluten‐free formulations in traditional food such as bread or pasta. However, owing to some intrinsic nutritional, textural, and sensory properties, the use of pulses as ingredients for production of enriched food remains limited. In this study, we investigated the modification in macromolecules and micronutrients in industrial‐scale flour from partially sprouted chickpeas to define its possible use as an ingredient in cereal‐based foods. Controlled sprouting resulted in significant decrease of antinutritional compounds (e.g., phytic acid and serine protease inhibitors) and in an increase of free minerals and vitamins. Sprouting also affected the overall structural organization of proteins (such as aggregate formation) and their thiol/disulfide balance, and it promoted release of peptides. All of these had a positive effect on dough mixing properties, in particular for dough development. Formulations with enrichment in sprouted chickpea flour (wheat/chickpea ratio = 100:20) were tested also as for their dough leavening properties, which improved with respect to flour from nonsprouted chickpeas. Taking into account the modifications induced by partial sprouting on an industrial scale, we can conclude that sprouted chickpea flour represents an interesting ingredient for production of enriched cereal‐based food with better nutritional and rheological characteristics.     

Farinograph Responses for Wheat Flour Dough Fortified with Wheat Gluten Produced by Cold‐Ethanol or Water Displacement of Starch

The objective of this research was to identify and define mixing characteristics of gluten‐fortified flours attributable to differences in the method for producing the gluten. In these studies, a wheat gluten concentrate (W‐gluten) was produced using a conventional process model. This model applied physical water displacement of starch (dispersion and screening steps), freeze‐drying, and milling. W‐gluten was the reference or “vital” gluten in this report. An experimental W‐concentrate was produced using a new process model. The new model applied coldethanol (CE) displacement of starch (dispersion and screening steps), freeze‐drying, and milling. Freeze‐drying was used to eliminate thermal denaturation and thereby focus on functional changes due only to the separation method. The dry gluten concentrates were blended with a weak, low‐protein (9.2%), soft wheat flour and developed with water in a microfarinograph. We found that both water and cold‐ethanol processed gluten successfully increased the stability (St) and improved mixing tolerance index (MTI) to create in the blended flour the appearance of a breadbaking flour. Notably, in the tested range of 9–15% protein, the St for CE‐gluten was always higher then the St for W‐gluten. Furthermore, the marginal increase in St (slope of the linear St vs. protein concentration) for the CE‐gluten was ≈57% greater than that for the W‐gluten. The slope of the MTI vs. protein data was lower for the CE‐gluten by 24%. Flour fortified with CE‐gluten exhibited higher water absorption (up to 1.8% units at 13.5% P) than flour fortified with W‐gluten.     

In Vitro Starch Digestibility of Gluten‐Free Spaghetti Based on Maize,Chickpea, and Unripe Plantain Flours

Gluten‐free and high indigestible carbohydrate food development is a topic that deserves investigation because of an increased focus on gluten intolerance and celiac disease and on metabolic disorders caused by overweight and obesity. Here, chickpea and maize flours were used as sources of protein and carbohydrate (because of the level used in the mixture) and unripe plantain as an indigestible carbohydrate source in composite gluten‐free spaghetti elaboration. The mixture of unripe plantain, chickpea, and maize was used at different levels to prepare spaghetti (samples S15Pla and S25Pla); control pasta was made of 100% semolina (S100Sem), and a 100% unripe plantain flour (S100Pla) pasta was also evaluated. In vitro amylolysis rate of fresh and stored (three and five days) spaghetti was assessed. The spaghetti with 100% unripe plantain (S100Pla) had higher resistant starch (RS) content than the control sample and the two cooked composite gluten‐free spaghettis (S15Pla, S25Pla), and RS further increased with the storage time. The plantain spaghetti (S100Pla) also had the highest rapidly digestible starch and the lowest slowly digestible starch contents; this pattern agrees with the hydrolysis rate, especially after cold storage. The stored S25Pla spaghetti showed the lowest hydrolysis rate and predicted glycemic index. Blending chickpea, maize, and unripe plantain flours represents a way to obtain gluten‐free spaghetti with high nondigestible carbohydrate content and slow digestion properties.     

Effect of Processing on Functional Properties of Wheat Gluten Prepared by Cold‐Ethanol Displacement of Starch

Functional properties of gluten prepared from wheat flour are altered by separation and drying. Gluten was separated and concentrated by batterlike laboratory methods: development with water, dispersion of the batter with the displacing fluid, and screening to collect the gluten. Two displacing fluids were applied, water or cold ethanol (70% vol or greater, ‐13°C). Both the water‐displaced gluten (W‐gluten) and ethanol‐displaced‐ gluten (CE‐gluten) were freeze‐dried at ‐20°C as a reference. Samples were dried at temperatures up to 100°C using a laboratory, fluidized‐bed drier. Tests of functionality included 1) mixing in a mixograph, 2) mixing in a farinograph, and 3) the baked gluten ball test. Dough‐mixing functionality was assessed for Moro flour (9.2% protein) that was fortified up to 16% total protein with dried gluten. In the mixograph, CE‐gluten (70°C) produced improved dough performance but W‐gluten (70°C) degraded dough performance in proportion to the amount added in fortification. In the microfarinograph, there was a desirable and protein‐proportional increase in stability time for CE‐gluten (70°C) but no effect on stability for W‐gluten (70°C). Baking was evaluated using the baked gluten ball test and the percentage increase in the baked ball volume relative to the unbaked gluten volume (PIBV). PIBV values were as high as 1,310% for freeze‐dried CE‐gluten and as low as 620% for W‐gluten dried at 70°C. PIBV for CE‐gluten was reduced to 77% of the freeze‐dried control by fluid‐bed drying at 70°C. Exposure of CE‐gluten to 100°C air gave a PIBV that was 59% of the reference, but this expansion was still greater than that of W‐gluten dried at 70°C. The highest values of PIBV occurred at the same mixing times as the peak mixograph resistance.     

Improved Protocols for ELISA Determination of Gliadin in Glucose Syrups

Simple modifications of existing protocols for high‐sensitivity detection of gluten proteins by immunochemical methods allowed rapid and sensitive determination of residual gluten in highly viscous samples of glucose and maltose syrups obtained from processing wheat starch. Dilution of the original syrup to no less than 15–20% in solids allowed retention of gluten proteins in a soluble form so that ELISA determination of gliadin was possible without an extraction step in aqueous ethanol. An ultrafiltration step may be added to concentrate residual gluten proteins in the diluted syrup samples and allow a further increase in sensitivity. The results are relevant for quality assessment of wheat starch derived syrups as raw materials for use in gluten‐free foods for celiac individuals.     

Definition of the “Purity Protocol” for Producing Gluten‐Free Oats

Several oat processors in the United States and Canada operate under what is referred to as a Purity Protocol for the provision of gluten‐free oats. This term is derived from a Health Canada position statement that indicated that pure oats, which they defined as oats that are harvested, transported, stored, processed, and manufactured under good manufacturing practices (GMPs) to minimize the presence of gluten, can safely be consumed by some persons with celiac disease. While proprietary definitions of the appropriate GMPs have been used in industry for many years, no independent definition of the requirements to make a Purity Protocol claim has been published. This paper provides a consensus definition of the Purity Protocol requirements based on input from the four largest Purity Protocol oat processors in North America. This definition provides transparency to gluten‐free consumers and allows for auditing of a Purity Protocol claim.     

Formation of Oligosaccharides and Polysaccharides by Lactobacillus reuteri LTH5448 and Weissella cibaria 10M in Sorghum Sourdoughs

Gluten‐free breads, which are composed of gluten‐free flours, starch, and hydrocolloids, differ from wheat and rye breads in relation to texture, volume, and crumb structure. Moreover, the dietary fiber content is lower compared with wheat or rye breads. Cereal isolates of lactic acid bacteria frequently produce oligo‐ and homopolysaccharides from sucrose, which can improve the nutritional and technological properties of gluten‐free breads as prebiotic carbohydrates and hydrocolloids, respectively. Sorghum sourdough was fermented with Lactobacillus reuteri LTH5448 or Weissella cibaria 10M, which synthesize fructooligosaccharides (FOS) and levan, and isomaltooligosaccharides and dextran, respectively. The gluten‐free bread was produced with 14% sourdough addition. L. reuteri LTH5448 formed FOS and 1.5 g of levan/kg DM in quinoa sourdoughs. FOS were digested by the baker's yeast during proofing, and the levan could be qualitatively detected in the bread. W. cibaria 10M produced >60 g of isomaltooligosaccharides/kg DM and 0.6 g of dextran/kg DM, which could still be detected in the bread. Breads prepared with W. cibaria 10M were less firm compared with breads prepared with L. reuteri LTH5448 or a FOS and levan‐negative mutant of L. reuteri LTH5448. The addition of sourdoughs fermented with oligo‐ and polysaccharide forming starter cultures can increase the content of prebiotic oligosaccharides in gluten‐free breads.     

Analysis of taste-active compounds in an enzymatic hydrolysate of deamidated wheat gluten

Hydrolyzed plant proteins are widely used as ingredients in culinary products for their glutamate-like ("umami") taste. Three hydrolysates were prepared from wheat gluten using different enzymatic approaches. Comparison of their taste profiles revealed the enzymatic hydrolysate of an acid-deamidated wheat gluten (WGH-3) to be the least bitter of all and to elicit an intense glutamate-like taste. Its umami taste intensity was similar to that of an enzymatic hydrolysate in which glutaminase had been employed to convert free glutamine to glutamic acid and which had a 3-fold higher concentration of free glutamate. Reconstitution studies based on the results of the chemical analysis of WGH-3 and sensory comparison of the model solution and WGH-3 indicated that other components in addition to glutamate and organic acids contribute to its glutamate-like taste. WGH-3 was fractionated by gel permeation chromatography and reversed phase high-performance liquid chromatography, and two fractions with a pronounced glutamate-like taste were obtained. In one of them four pyroglutamyl peptides were tentatively identified: pGlu-Pro-Ser, pGlu-Pro, pGlu-Pro-Glu, and pGlu-Pro-Gln. Apparently, these peptides were formed by cyclization of the N-terminal glutamine residues during the preparation of the hydrolysates.     

脱酰胺与双酶协同作用提高小麦面筋蛋白酶解效率

为了探讨了不同脱酰胺处理和双酶协同作用方式对小麦面筋蛋白酶解效率及其产物抗氧化活性的影响,该文研究了小麦面筋蛋白在各种预处理方式和酶解条件下的蛋白回收率、水解度、抗氧化性能及肽分子量分布情况。结果显示,单独热处理(90℃,30 min)小麦面筋蛋白对其酶解效率无显著影响,而采用添加0.5 mol/L柠檬酸溶液进行热处理(质量分数为5%,90℃,30 min)可显著(P0.05)提高其蛋白回收率。此外,酶制剂添加顺序及双酶共同水解作用时间对酶解效率均具有较大影响:加入谷氨酰胺酶预先水解对小麦面筋蛋白的深度水解有促进作用;一定时间内的双酶协同作用有利于酶解的进行,但较长时间的双酶作用反而会抑制酶解效率。采用谷氨酰胺酶(质量分数为0.2%)对经柠檬酸加热处理的小麦面筋蛋白作用12 h后再加入胰酶(质量分数为0.6%)共同作用7 h可使蛋白回收率达70.74%,水解度达到9.88%;另外,酶解产物的自由基清除能力ABTS+(2,2’-Azinobis-(3-ethylbenzthiazoline-6-sulphonate)+)值与氧化自由基吸收能力(ORAC,oxygen radical absorbance capacity)值分别达到478.95 mmol/g和213.85μmol/g,提示该酶解产物是一种潜在优秀食品抗氧化剂。研究结果可为拓宽小麦面筋蛋白的应用领域,以及高效制备抗氧化活性肽提供方法和理论指导。