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1.
Oat grain is routinely kilned and steamed before milling to develop flavor and to inactivate lipid-degrading enzymes. Heat treatments can significantly affect viscous properties, which have functional and nutritional importance. Oat flour slurries (23%, w/w, solids dry basis) made from steamed (for 20 min) or autoclaved (at 121°C, 15 psi, for 10 min) grain developed high viscosities, whereas flour slurries made from raw or kilned (105°C for 90 min) oats did not. Flour slurries made from raw groats, surface-sterilized by 1% hypochlorite, were more viscous than untreated raw groat flour slurries, suggesting that β-glucan hydrolases on the surface of the groat caused the viscosity losses observed in raw or kilned groats. However, because viscosities developed by surface-sterilized groats were not as great as in steamed oat-flour slurries and because some roasting treatments also inactivated enzymes without enhancing viscosity, it appears steaming might also affect the β-glucan polymer, resulting in its greater hydration in solution. Smaller particle size and higher incubation temperature also resulted in increased flour slurry viscosity, presumably because of increased hydration of the β-glucan. Rmoval of lipids from steamed oat flour significantly increased the oat flour slurry viscosity, apparently by increasing the β-glucan concentration in the flour.  相似文献   

2.
Changes in the sensory attributes, lipid composition, and amounts of volatile and phenolic compounds of native and processed (germinated and dried) crushed oat were followed during a 12‐month storage period. The influence of the chemical attributes on the sensory profiles of oats was analyzed by statistical multivariate techniques (PLS regression). During the storage period, significant changes in the sensory profiles of the native and processed oat groats were observed. The stability of oat groats was significantly increased through germination and subsequent drying because the chemical changes causing rancidity and bitterness developed more slowly in the processed oat when compared with the native oat. In native oat, the most intensive changes due to deteriorat ion had already occurred after one month of storage, whereas in processed oat, these changes were perceived considerably later. Stored oat that had deteriorated was evaluated as being musty and earthy in odor and bitter and rancid in flavor. The accumulation of free fatty acids and volatile compounds related to lipid oxidation were closely correlated with the development of the undesired sensory attributes described above. The total amount of phenolic compounds, as well as the volatile aromatic and branched chain compounds derived mainly from protein degradation, showed a significant relationship with favorable sensory attributes such as roasted odor and flavor. Lipid oxidation occurred during the storage and was observed both in the polar and in the nonpolar lipid classes of native oat, whereas in the processed oat, these changes were nonsignificant. Photo‐oxidation of acylated fatty acids may significantly contribute to the development of volatile lipid oxidation products during storage.  相似文献   

3.
A decrease of the concentration of the synthetic avenanthramide N‐(4′‐hydroxy‐(E)‐cinnamoyl)‐5‐hydroxyanthranilic acid in a buffered slurry of milled oat groats (Avena sativa L.) was temperature and pH‐dependent, with a maximum rate at 30°C and pH 9. The reaction was inhibited in the presence of 2‐mercaptoethanol, acetic acid and at high temperature; suggestive of enzymatically catalyzed nature. Among eight different synthetic avenanthramides tested, the tentative enzyme had highest affinity for avenanthramides comprising caffeic and p‐coumaric acids and lowest for those comprising sinapic and ferulic acids. The activity was found in samples from several oat cultivars and was equally pronounced in both bran and endosperm flour of oats. Steeping of oat grains did not influence the reaction.  相似文献   

4.
Hydrothermal treatments, which are routine in oat processing, have profound effects on oat flour dough rheological properties. The influence of roasting and steam treatments of oat grain on dough mixing and breadbaking properties was investigated when hydrothermally treated oat flour was blended with wheat flour. Roasting of oat grain (105°C, 2 hr) resulted in oat flours that were highly detrimental to wheat flour dough mixing properties and breadbaking quality. Steaming (105°C, 20 min) or a combination of roasting and steaming of oat grain significantly improved the breadbaking potential of the oat flours. The addition of oat flours increased water absorption and mixing requirements of the wheat flour dough and also decreased bread loaf volume. However, at the 10% substitution level, steamed oat flours exhibited only a gluten dilution effect on bread loaf volume when wheat starch was used as a reference. Oat flour in the breadbaking system decreased the retrogradation rate of bread crumb starch. The results indicate that adequate hydrothermal treatments of oat grain are necessary for oat flour breadbaking applications. Steamed oat flours used at a 10% level retarded bread staling without adversely affecting the loaf volume.  相似文献   

5.
Concentrations of avenanthramides and activity of the biosynthetic enzyme hydroxycinnamoyl‐Co A:hydroxyanthranilate N‐hydroxycinnamoyl transferase (HHT) were analyzed in dry or, steeped nonmilled or milled, non‐heat‐treated (raw) or heat‐treated oat samples (Avena sativa L.). Increased avenanthramide concentrations were found when intact raw groats were steeped. The increase was time‐ and temperaturedependent and maximal after 10 hr of steeping at 20°C. Continuous germination in air, after steeping, only contributed to a further increase in avenanthramides when steeping times were shorter than 10 hr. Concentrations of avenanthramides and HHT activity were positively correlated during steeping of intact groats at 8 and 20°C. The increase in avenanthramides was suggested to be due to de novo synthesis and a whole grain structure seemed to be required as no increase was found when groats were milled before steeping. Avenanthramide levels also increased when heat‐treated samples, lacking HHT activity, were steeped. This increase may be due to release of bound forms, possibly formed during the preceding heat treatment.  相似文献   

6.
Changes in fats extracted from cookies stored for three or five weeks and containing different levels of oat flakes (10, 20, 30%) were investigated. The fats used for baking differed in fatty acid (FA) composition and contained 17.6–57.6% saturated (SFA), 0.8–46.8% trans FA (TFA), and 0.6–6.6% polyunsaturated FA (PUFA). Oat flakes were steam stabilized and were in the middle of their shelf‐life. Oat flakes contained 9.5% lipids in which linoleic acid (C 18:2 9c 12c) predominated, amounting to 42.7%. Increasing the content of oat flakes and the storage time of cookies resulted in increased values of primary and secondary fat oxidation products. Highest increases in PV values were found in cookies stored for three or five weeks, especially with a high content of oat flakes (30%). Secondary lipid oxidation products measured by AnV values increased with the time of storage. Highest increases in hydrolytic and oxidation products were associated with higher content (6.6%) of PUFA in utilized fats. Regarding the degree of oxidation, it appears safe to add as much as 30% of oat flakes to cookies when the storage time does not exceed three weeks.  相似文献   

7.
Buckwheat is a pseudocereal with a strong characteristic aroma. Compounds responsible for the aroma of buckwheat groats were recently identified, but the distribution of aromatic compounds between different fractions of the buckwheat kernel (flour, bran, and husk) is not yet known. In this study, the composition of aromatic compounds in buckwheat seed fractions was investigated and compared to the composition of aromatic compounds in groats produced from the same batch of buckwheat seeds. Volatiles from each sample were extracted with simultaneous distillation/extraction with a Likens‐Nickerson apparatus. Extracts were analyzed by gas chromatography coupled with mass spectrometry (GC‐MS) with electron ionization. Apart from the aroma molecules present in all fractions, compounds that are present only in flour or bran, but not in groats, were also found. Furthermore, some compounds were identified only in buckwheat groats but not in buckwheat flour or bran [octanal, (E,E)‐2,4‐heptadienal, (E)‐2‐decenal, and (E,E)‐2,4‐decadienal], others were identified only in husks [(E)‐2‐hexenal, heptanal, (E,E)‐2,4‐hexadienal, phenylacetaldehyde, and alpha‐bisabolol].  相似文献   

8.
Muffins containing different amounts and molecular weights (MW) of β‐glucan were evaluated for the effect of β‐glucan on the physical characteristics of the muffins and on in vitro bile acid binding and fermentation with human fecal flora. Wheat flour muffins were prepared with the addition of β‐glucan extracts with high‐, medium‐, or low‐MW. For oat flour muffins, the native oat flour contained high‐MW β‐glucan; the oat flours were treated to create medium‐ and low‐MW β‐glucan within the prepared muffin treatments. For each 60‐g muffin, the amounts of β‐glucan were 0.52, 0.57, and 0.59 g for high‐, medium‐, and low‐MW β‐glucan wheat flour muffins, and 2.38, 2.18, and 2.23 g for high‐, medium‐, and low‐MW β‐glucan oat flour muffins, respectively. The lower the MW of the β‐glucan in muffins, the lower the height and volume of the muffins. The oat flour muffins were less firm and springy than the wheat flour muffins as measured on a texture analyzer; however, MW had no effect on muffin texture. The oat flour muffins bound more bile acid than did the wheat flour muffins. The muffins with high‐MW β‐glucan bound more bile acid than did those with low‐ and medium‐MW β‐glucan. Muffin treatment affected the formation of gas and total short‐chain fatty acids (SCFA) compared with the blank without substrate during in vitro fermentation. There were no differences in pH changes and total gas production among muffin treatments. The high‐MW β‐glucan wheat flour muffins produced greater amounts of SCFA than did the wheat flour muffin without β‐glucan and the oat flour muffins; however, there were no differences in SCFA production among muffins with different MW. In general, the β‐glucan MW affected the physical qualities of muffins and some potential biological functions in humans.  相似文献   

9.
《Cereal Chemistry》2017,94(3):640-642
Rice kernels were steeped (10°C, 5 h) in an aqueous solution containing gum arabic (0.36%) and xanthan (0.24%) and then drained, wet‐milled, and steamed to prepare rice cakes. The cakes were then frozen (–40°C for 50 min). The effect of the gum addition on the textural properties of the cakes during storage for 46 h at 25°C after being thawed was examined. Using the combination of gum arabic and xanthan mitigated the quality deterioration of rice cakes such as aggregation of rice flour, which had been induced by xanthan alone. Also, the increase in hardness during storage was substantially reduced by soaking rice kernels in the gum arabic/xanthan solution. Overall results revealed that the steeping in the gum solution improved the storage stability of rice cakes.  相似文献   

10.
Sifted oat flour was processed at 25.0, 27.5, and 30.0% moisture content in a twin-screw extruder at screw speed 300 rpm. The preset temperatures of the extruder barrel were 120, 150, or 180°C. Raw material and extrudates were analyzed for the content of diethyl ether-extractable lipids, with and without hydrolysis, and the content of chloroformmethanol-water saturated butanol (C/M/WSB) extractable lipids. The lipid extracts were analyzed for fatty acid (FA) composition. Percentage distribution of palmitic, oleic, and linoleic acids were significantly different in the different lipid extracts. Extrusion processing influenced the amounts of extractable lipids, while FA composition was not affected.  相似文献   

11.
The effects of various commercial hydrothermal processes (steaming, autoclaving, and drum drying) on levels of selected oat antioxidants were investigated. Steaming and flaking of dehulled oat groats resulted in moderate losses of tocotrienols, caffeic acid, and the avenanthramide Bp (N-(4'-hydroxy)-(E)-cinnamoyl-5-hydroxy-anthranilic acid), while ferulic acid and vanillin increased. The tocopherols and the avenanthramides Bc (N-(3',4'-dihydroxy-(E)-cinnamoyl-5-hydroxy-anthranilic acid) and Bf (N-(4'-hydroxy-3'-methoxy)-(E)-cinnamoyl-5-hydroxy-anthranilic acid) were not affected by steaming. Autoclaving of grains (including the hulls) caused increased levels of all tocopherols and tocotrienols analyzed except beta-tocotrienol, which was not affected. Vanillin and ferulic and p-coumaric acids also increased, whereas the avenanthramides decreased, and caffeic acid was almost completely eliminated. Drum drying of steamed rolled oats resulted in an almost complete loss of tocopherols and tocotrienols, as well as a large decrease in total cinnamic acids and avenanthramides. The same process applied to wholemeal made from groats from autoclaved grains resulted in less pronounced losses, especially for the avenanthramides which were not significantly affected.  相似文献   

12.
Nutrient densities, carbon:nitrogen (C:N) ratio, and midday differential canopy temperature (dT), were assessed in oat plants subjected to biotic stresses during two years. Large portions of variation in nutrient densities and C:N ratio of leaves at the boot stage and of kernels and groats at harvest were negatively impacted by the 2- and 3-way interactions of leaves, kernels, and groats with the biotic stress treatments and years. The C:N ratios, but not nutrient densities, were always smaller in groats than in kernels, and during the stress than the no-stress year. Temporal variation accounted for a small variance associated with nutrients in leaves; whereas, stress treatments accounted for the largest variances associated with nutrients in kernels and groats. These indirect relationships among plant architecture components, dT, nutrient densities and C:N ratios, illustrate the complex interactions of biotic and abiotic stresses and their impact on grain yield and its components in oat.  相似文献   

13.
Flours differing in water content of 10% (F10), 12% (F12), and 14% (F14) were stored for 16 weeks at 22, 32, and 45°C. The major changes in lipids concerned the free fatty acids (increase) and the triglycerides (decrease). In all cases, the changes increased with increasing storage temperature and water content. After 16 weeks of storage, the losses in lipoxygenase (LOX) activity increased with increasing flour moisture and storage temperature from 10% for F10 at 22°C to 100% for F14 at 45°C. At the end of storage at 22 and 32°C, the bread volumes decreased by 10 and 25%, respectively, with no statistical differences (P < 0.05) between the samples. At 45°C, the volume losses were equal to 35, 46, and 61% for the F10, F12, and F14 samples, respectively. In the same time, the flour oxidative ability (oxygen uptake during dough mixing) increased for the F10 and F12 samples with increasing storage temperature, whereas it decreased for the F14 samples stored at 45°C. Therefore, provided the residual LOX activity is sufficient (omission of the F14 samples stored at 45°C), the flour oxidative ability increased during storage and is positively correlated to its oxidable PUFA content.  相似文献   

14.
Two cultivars of wheat (Triticum aestivum L.), Sunco and Sunsoft, were used to study the influence of storage time and temperature on the formation of starch-lipid complexes in flour pastes. Untreated and fat-reduced whole meal flours were stored separately for up to 12 months at 4, 20, and 30°C. The stored samples were analyzed for fat acidity, pasting properties, and iodine binding values. Fat acidity increased significantly in the untreated flour samples stored at 30 and 20°C compared with 4°C. Starch pasting properties, as measured using a Rapid Visco Analyser (RVA) indicated that the final viscosity of untreated flour samples of both cultivars increased significantly with storage time and elevated temperature, and correlated positively with increased fat acidity. Iodine binding values of the RVA pastes decreased with storage time and elevated temperature, and correlated negatively with fat acidity and final viscosity. The fat-reduced Sunco and Sunsoft flours showed less pronounced changes compared with untreated flours, whereas small changes in the RVA parameters were noted in grains stored over 12 months. The results indicate that free fatty acids are released during storage and that they increase the potential for starch-lipid complex formation when stored whole meal wheat flours are pasted in the RVA. These changes were evident after two to three months of storage at 20 and 30°C.  相似文献   

15.
A second unusually high viscosity peak appeared at the cooling stage (50°C) of a Rapid Visco‐Analyser (RVA) profile of short‐term stored (two months at room temperature) whole grain sorghum flour, while freshly ground flour had a typical pasting curve with one viscosity peak at the 95°C holding period. The formation of the second viscosity peak was caused by liberation of free fatty acids (FFA), mainly palmitic (15.6%), oleic (41.9%), and linoleic (37.9%) acids from stored flour. After the flour samples were pretreated with pepsin or the protease thermolysin, the second peak disappeared in the presence of FFA while the high viscosity was partially retained, indicating that flour protein was another essential component to the production of the actual peak. Effects of dithiothreitol (DTT), pH, and NaCl on RVA profiles of stored flour suggested that disulfide‐linked protein and electrostatic interaction are required for the peak production. In the presence of sufficient FFA, similar cooling stage viscosity peaks appeared in the RVA profiles of flour samples from maize, rice, millet, and wheat; thus, the effect was not unique to sorghum flour. Coinciding with previously reported findings from our laboratory of a three‐component interaction and discernable complex in a model system, a similar three‐component (starch, protein, and FFA) interaction was revealed in natural flour systems resulting in formation of an unusual and notably high cooling stage viscosity peak. Practical applications and an interaction mechanism are discussed.  相似文献   

16.
Grains of two wheat (Triticum aestivum L.) cultivars, Sunco and Sunsoft, were stored at 4°C and 30°C for 270 days to examine changes in proteins during storage. When whole meal flour extracted from the grains was analyzed using an unfractionated protein extraction procedure, no significant changes were found in protein content or SDS‐PAGE profile for either cultivar in samples stored at 30°C compared with those stored at 4°C. Fractionation of the flour samples from stored grain into soluble and insoluble proteins revealed increases in soluble protein content for both cultivars stored at 30°C compared with 4°C. The soluble protein content, expressed as a percentage of the total protein, increased by 1.5% (P = 0.032) for Sunco and by 8.0 % (P = 0.158) for Sunsoft during storage at 30°C compared with those samples stored at 4°C. Analysis by SDS‐PAGE and subsequent protein identification revealed that the most evident change that occurred during storage at 30°C was an increase in the content of high molecular weight glutenin subunits (HMW‐GS) in the soluble fraction. The potential effect of changes in solubility of HMW‐GS on functional properties is discussed.  相似文献   

17.
Salmon fillets were steamed, or pan-fried without oil, with olive oil, with corn oil, or with partially hydrogenated plant oil. The exchange between the salmon and the pan-frying oils was marginal, but it was detectable as slight modifications in the fatty acid pattern and the tocopherol contents according to the oil used. Primary and secondary oxidation products were only slightly increased or remained unchanged, which indicated a slight lipid oxidation effect due to the heating procedures applied. The same was observed for tocopherol levels, which remained almost stable and were not affected by the oxidation process. The sum of cholesterol oxidation products (COPs) increased after the heating processes from 0.9 microg/g in the raw sample to 6.0, 4.0, 4.4, 3.3, and 9.9 microg/g extracted fat in pan-fried without oil, with olive oil, corn oil, partially hydrogenated plant oil, and steamed, respectively. A highly significant correlation was found between the fatty acid pattern and the total amount of COPs (r2 = 0.973, p < 0.001). No change has been determined in the n-3 fatty acids content and in the polyunsaturated/saturated-ratio of the cooked salmon fillets. Moderate pan-frying (6 min total) and steaming (12 min) of salmon did not accelerate lipid oxidation but significantly increased the content of COPs. The highest increase of COPs was found through steaming, mainly due to the longer heat exposure. The used frying oils did not influence the outcome; no significant difference between heat treatment with or without oil has been determined.  相似文献   

18.
Antioxidant‐rich plant materials could provide protection against oxidation in extruded foods and feeds, but their efficacy is not well established. Degermed yellow cornmeal was mixed with 0.02% (w/w) ascorbic acid or quercetin, or with 2% (w/w) spray‐dried ginkgo extract, onion powder, potato peels, or wheat bran. The mixtures were processed in a laboratory‐scale twin‐screw extruder at a feed rate of 227 g/min. Water pump rate was 16 g/min; screw speed was 200 rpm. Mass temperature during extrusion averaged ≈170°C. Samples were cut into small spheres, dried to 5% moisture, then stored in trilaminate bags at 25°C. Ground sample headspace was assayed for hexanal and other volatile indicators of oxidation by gas chromatography. Ginkgo and potato peels significantly darkened the extrudates. Total soluble phenolics, as ferulic acid equivalents, were highest in the ginkgo sample. Volatile compounds were lower in several treatments during storage compared with the control. These findings suggest that manufacturers may be able to formulate products with improved shelf‐life through addition of antioxidant‐rich food materials.  相似文献   

19.
Functionality of four leavening acids (sodium aluminum phosphate [SALP], sodium aluminum sulfate [SAS], monocalcium phosphate [MCP] and sodium acid pyrophosphate [SAPP‐28]) was evaluated during processing of wheat flour tortillas. Formulas were optimized to yield opaque, large‐diameter tortillas with pH 5.9–6.1. Each leavening acid and sodium bicarbonate was first evaluated at 38°C and then evaluated in combination with fumaric acid at 34 and 38°C. Ionic and pH interactions of leavening salts adversely affected dough properties and resting time. Opacity and pH of tortillas prepared with MCP was lower than for other treatments. Higher dough temperature required more leavening acid and base to compensate for some of the loss of CO2 incurred during dough mixing and resting at 38°C. The addition of fumaric acid decreased the amount of leavening acid, the dough‐resting time and tortilla pH, and improved storage stability. Combinations of MCP, SALP (or SAS), and fumaric acid produced dough and tortillas with good qualities. Tortillas prepared using SALP (or SAS) and fumaric acid tended to be of better quality.  相似文献   

20.
Fats, oils, and grease (FOG) and source separated organics (SSO) were treated with the microwave-enhanced advanced oxidation process (MW-AOP) at 90 and 110 °C, with varying amounts of hydrogen peroxide dosages. The treatment efficiency, in terms of soluble substrates and volatile fatty acids (VFA), increased with an increase in both temperature hydrogen peroxide dosages. Fatty acids and compounds with carbonyl group and/or hydroxyl group in both initial and treated FOG samples were identified by gas chromatography-mass spectrometry. MW-AOP treatment temperatures and hydrogen peroxide dosages dictated the formation of degradation products. The degradation followed peroxidation mechanism to produce lower molecular weight substrates such as short chain fatty acids which would be less inhibitory to microbes. After the MW-AOP treatment, both SSO and FOG comprised of more soluble and low molecular weight compounds. These compounds included VFA and nutrients that would be readily available for bacterial or plant uptake.  相似文献   

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