HEADSPACE GAS CHROMATOGRAPHY AND SENSORY ANALYSES OF BUCKWHEAT STORED UNDER CONTROLLED ATMOSPHERE1

The composition of volatile components in freshly-milled buckwheat flour produced from seed stored under controlled atmospheres (97% N₂ 1.5% O₂ and 1.5% CO₂) for 1 year was studied using capillary gas chromatography, mass spectrometry, sniffing port analysis, and sensory evaluation. Twenty-five volatiles were identified from over 100 compounds removed from the flour by a novel dynamic headspace technique and separated by capillary gas chromatography. Eighteen odor-active regions were detected but none were characteristic of the typical buckwheat flour aroma. The concentration of the major buckwheat volatiles decreased with storage of the seed under low O₂ and high CO₂ levels. The content of two of the odor-active volatiles, hexyl acetate and 1-hexanol, however, increased up to 4 fold in samples stored under controlled atmosphere for 60 weeks.     

Effects of ingredients on the oxidation of linoleic acid by lipoxygenase in bread doughs

Flour and water doughs containing 1-¹⁴C-linoleic acid (18:2) and various ingredients were prepared to study the oxidation of linoleic acid by lipoxygenase in bread doughs. Lipids were extracted, treated with diazomethane, and ¹⁴C-labelled fatty acid methyl esters separated by thin-layer chromatography. Radioactivity was determined in silica gel bands containing unoxidised 18:2, hydroperoxy acids (L₁), hydroxy acids (L₂), hydroxyepoxy acids (L₃) and trihydroxy acids (L₄). Minor components detected by autoradiography were present mainly in L₃ and L₄. Recoveries of total radioactivity were always > 95%. Untreated flour-water dough was mixed aerobically for ?4 min, rested, and the lipids extracted after 10 min total dough time. Yields of ¹⁴C products were unoxidised 18:2 = 28.6 μmol, L₄ = 93.9 μmol/100 g dry flour. Similar yields were obtained from ClO₂-treated flour, both after 10 min and 60 min dough time. Salt, salt + yeast, or salt + yeast + ascorbic acid in the dough did not reduce 18:2 oxidation significantly, but increased L₃ at the expense of L₄. Soya flour preparations inhibited linoleic acid oxidation by 25–44%, but pure soya lipoxygenase had no effect at all. Heat treatment reduced the inhibitory effect of soya flour. Accessible thiol groups were not essential for lipoxygenase activity or for the reduction of L₁ to L₂ since adding cysteine or N-ethyl maleimide had negligible effects on the 18:2 oxidation products. Most of the flour carotenoids (xanthophylls) were bleached by wheat enzymes in non supplemented doughs, and all were bleached in doughs supplemented with soya flour. ¹⁴C-labelled triglyceride was not oxidised except in doughs containing soya flour mixed in air (1.5% oxidation) or oxygen (3 % oxidation). Soya flour contains lipoxygenase isoenzymes (principally lipoxygenase-2) which oxidise linoleate in triglycerides. This isoenzyme is evidently not present in wheat.     

Carob bean germ seed (Ceratonia siliqua): Study of the oil and proteins

The oil and flour of the seed germ of carob bean (Ceratonia siliqua L) were studied. The fatty acid composition included, as main components, palmitic (14·2%), stearic (3·0%), oleic (38·5%) and linoleic (43·6%) acids. Lipolysis with pancreatic lipase shows the following glyceride composition: S₃ (0·0%), US₂ (2·7%), SU₂ (27·9%) and U₃ (63·7%). The protein flour was separated into protein classes according to their solubility and molecular weight, and the preparation of an isolate (with more than 90% protein) is described.     

Effects of ball‐milling on the glass transition of wheat flour constituents

BACKGROUND: Starch and gluten, the major components of wheat flour, greatly influence the structural characteristics of food products made with wheat flour. The effects of ball‐milling on the change in the semicrystalline structure of starch granules to the amorphous state have been reported. However, the effects of ball‐milling of native wheat flour on physicochemical changes in wheat flour constituents have not been elucidated. Therefore in this study the effects of ball‐milling on the glass transition of wheat flour constituents were investigated. RESULTS: Crude gluten, non‐gluten proteins and separated starch were obtained from wheat flour ball‐milled for 0–10 h, and the glass transition temperature (T_g) of these constituents was evaluated. The T_g of all wheat flour constituents decreased with increasing ball‐milling time. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that changes in band position and intensity did not occur for gluten but did occur for non‐gluten proteins. X‐ray diffraction revealed decreased crystallinity and greater plasticisation by water in separated starch as the ball‐milling time was prolonged. CONCLUSION: The results showed that the ball‐milling process decreased the T_g of wheat flour constituents as a function of milling time. The decrease in T_g was probably due to changes in conformation of protein subunits in gluten and depolymerisation of the non‐gluten protein fraction. The information obtained here about the physical alteration of wheat flour constituents may enhance the ability to successfully use ball‐milled wheat flour in food applications. Copyright © 2008 Society of Chemical Industry     

Two-Steps Procedure for the Purification of Corn Flour Hydrolysate

When corn flour hydrolysate filtrate (CFHF) was treated with 100% (w/v) (NH₄)₂SO₄ for purification, 80.5% of the protein was removed. Among the pH values studied, at pH 1.5, 90.2% of the total protein was precipitated from CFHF and supernatant was removed by decantation. The corn flour hydrolysate was purified with Amberlite and DEAE-cellulose after precipitating the protein at pH 1.5. Charcoal was better than cation- and anion- exchange resins for the removal of proteins, amino acids and pigments from the hydrolysate.     

Fate of Chlorine During Flour Chlorination

Unbleached flour (pH 5.8) was treated with ³⁶Cl₂ (g) in a closed-system flour chlorinator to pH levels of 5.25, 4.41, and 4.01. Of the total active Cl₂ generated (12.38, 20.71 and 28.17 mg, respectively), 98.6–99.6% was shown to react with the flour. Only 0.35–1.37% was recovered in NaOH traps. Extraction of the treated flour with chloroform showed that 27.0–33.7% of the total ³⁶Cl was incorporated into flour lipids, of which 31.2–39.1% of the radioactivity went to nonpolar lipids and 60.9–68.8% to polar lipids. The water-insoluble and water-soluble fractions of defatted flour contained 17.9–21.4% and 2.1–4.7% of the total ³⁶Cl, respectively. The remaining ³⁶Cl (40.3–49.1%) was present as ³⁶Cl^-.     

Physicochemical and sensory characteristics of a low-fat tofu produced using supercritical CO2 extracted soy flour

The potential of supercritical CO₂ (SC-CO₂) extracted soy flour was evaluated as a raw material for functional foods. The fat content in SC-CO₂ soy flour was reduced from 19.5% to 7.1%, which influenced some textural and sensory properties of soymilk and tofu. The viscosity of low-fat soymilk decreased from 50 to 40 cp. Low-fat tofu had a higher yield of 69.7%, compared to a yield of 60.8% for full-fat soymilk. The two types of tofu had similar flavor and texture intensity sensory scores, although low-fat tofu had a reduced score for roasted, nutty flavor than full-fat tofu. The pH of a low-fat tofu immersion solution during 30 days of storage was lower than for a full-fat tofu solution, particularly during the first 6 days. A low-fat tofu that is similar to full-fat tofu can be prepared using SC-CO₂ extracted soy flour.     

Production of iron-fortified bread employing some selected natural iron sources

Iron fortification of wheat breads is the optimal approach for reducing the high prevalence of iron deficiency in wheat-eating developing countries as in Egypt. The effectiveness of some natural iron-fortificants for potential use in Egyptian bread was tested. Defatted soybean flour, soybean flour, soybean hull flour, molasses and fenugreek flour at different levels besides FeSO₄ · 7H₂O as standard were separately incorporated in the wheat flour dough. Dough characteristics were studied using a Brabender Farinograph, where addition of such fortificants improves significantly (p < 0.05) the water absorption, development time, dough stability and dough weakening. Good breads with high nutritive value, excellent crust color, crumb grain and high overall acceptability were produced by adding either 10% defatted soybean flour, 5% soybean hull flour, 2% molasses or 4% fenugreek flour. Rat feeding trials have shown a good haematological response, i.e. higher haemoglobin (Hb) and haematocrit (Hct) values gained. Additional work is needed to identify other fortification options and to develop targeted fortification programes that will supply iron to all segments of a population in greatest need.     

Improvement by oxidising agents of the baking performance of pure and composite flours from nigerian-grown wheats (Lee X and Inia 66)

The feasibility of improving the bread-baking performance of two varieties of Nigerian-grown wheat (Lee X and Inia 66) in pure and composite flour, using the oxidising agents potassium bromate and ascorbic acid was studied. Composite flour was prepared by mixing pre-cooked bambara bean (Voandzeia subterranean) flour at levels between 0 and 50% with each of commercial (control), Lee X and Inia 66 wheat flour. Physical and sensory evaluations showed that the performance of straight Lee X and Inia 66 flours was inferior to that of the commercial flour. The commercial flour showed better tolerance to blending with bambara flour, producing acceptable loaves at up to 20% substitution with bean flour; Lee X and Inia 66 could not tolerate blending beyond 15% and 5% levels, respectively. Physical properties and baking performance of the Lee X and Inia 66 flours were improved by treatment with various levels of the oxidising agents KBrO₃, ascorbic acid and KBrO₃/ascorbic acid combinations. Lee X flour was more responsive to the treatments than Inia 66. Concentrations of 25 mg kg^?1 KBrO₃ and 80 mg kg^?1 ascorbic acid singly were found to improve Lee X flours adequately, but a combination of the two agents at a level of 25/60 mg kg^?1 KBrO₃/ascorbic acid was optimal. When treated with the optimal level of improver combination, Lee X flour performed as well as the commercial flour; and treated Lee X composite flours containing up to 30% pre-cooked bambara flour were found to produce loaves not significantly different from 100% commercial wheat bread (P≤0.05).     

Determination of thiol groups and disulphide bonds in wheat flour and dough

A study was made of the conditions for determining all thiol (SH) groups and disulphide (S—S) bonds in wheat flour and dough. Thiol groups were determined by amperometric titration with Ag₂SO₄, the flour or dough which contains proteins and peptides being suspended in a solution of 6 m urea and 10^?4 M sodium dodecyl sulphate (SDS). The potential of the platinum electrode was ?0.24 V vs calomel reference electrode. Disulphide bonds were determined in two ways: (a) Using an excess of Ag₂SO₄ in the presence of 9 M urea; when the reaction was finished, the excess Ag₂SO₄ was removed by adding an exact quantity of glutathione. The glutathione which remained after binding the Ag₂SO₄ excess was determined by amperometric titration with a 5.10^?5 M Ag₂SO₄ solution, (b) Determination after reduction with NaBH₄; the disulphide bonds were reduced to thiol groups and the total amount of thiol groups was determined with Ag₂SO₄. The results indicated that wheat flour contains 5–7 μmol SH-groups, which is about six times the level found by previous workers, and 11-18 μmol disulphide bonds per gram flour. A correlation with baking quality was not observed.     

Techno‐functional properties of wheat flour‐resistant starch mixtures applied to breadmaking

Resistant starch can be used to reduce the availability of carbohydrates in baked products. In this study, the effect of type 4 resistant wheat starch (RS₄) on wheat flour dough and breads was evaluated. Wheat flour was substituted by RS₄ at 10%, 20% and 30% w/w (RS10, RS20 and RS30, respectively). Rheological and thermal behaviours of dough were evaluated. Besides, bread quality, starch digestibility and bread staling were analysed. All substituted dough exhibited viscoelastic behaviour but lower elastic and viscous moduli. Regarding to bread quality, specific volume and crumb texture were negatively affected in samples with RS₄. However, all samples were technologically acceptable. During storage, crumb hardening was observed in breads without and with RS₄ but amylopectin retrogradation was not particularly affected. The in vitro digestibility of bread with RS showed a lower release of reducing sugars and a lower estimated glycaemic index, suggesting a healthier profile for these breads.     

AN IMPROVED PROCESS FOR ISOLATION OF GLANDLESS COTTONSEED PROTEIN USING INDUSTRIAL MEMBRANE SYSTEMS

An improved process employing a combination of isoelectric precipitation and ultrafiltration to isolate glandless cottonseed protein was developed. The effectiveness of Ca(OH)₂, NaOH, and KOH in extracting storage protein (SP) was compared at pH 10, 9.5 and 9.0. KOH and NaOH each solubilized ca 88% of the flour nitrogen at pH 10, 87% at pH 9.5, and 85% at pH 9.0. Ca(OH), proved less effective, solubilizing about one-fifth as much as the other two hydroxides. Nonstorage protein (NSP) extract was separated by acid precipitation into curd and whey: The lysine-rich NSP whey was then added to SP extract and the mixture ultrafiltered to obtain a higher yield of SP isolate having a lighter color and increased lysine content.     

Isolierung und Charakterisierung derl -Ascorbins?ureoxidase (EC 1.10.3.3) aus Weizenmehl

Zusammenfassung Weizenmehl (Caribo, 0,55% Asche) wurde mit 0,4 m-NaCl-Lösung extrahiert, diel-Ascorbinsäureoxidase mit (NH₄)₂SO₄ gefällt und das Konzentrat aufgetrennt mit der Dünnschichtisoelektrischen Focussierung an Polyacrylamid- bzw. Dextrangel. 8–12 aktive Fraktionen (Isoenzyme) werden festgestellt, die eine hohe Spezifität fürl-Ascorbinsaure gegenüberd-Isoascorbinsaure aufweiseri (im Mittel nur 7% Fremdaktivität). Die Molekulargewichte liegen zwischen 165 000 and 175 000 (bestimmt durch Dextrangel-Dünnschichtchromatographie). In frischem Mehl liegt die Aktivität bei 28 mgl-Ascorbinsäure pro kg Mehl in 30 min, nach 30 Tagen ist die Aktivität auf 5% abgesunken, nach 60 Tagen nicht mehr nachweisbar.

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Isolation and Characterisation ofl-ascorbic Acid Oxidase (EC 1.10.3.3) from Wheat Flour

Summary Wheat flour (Caribo, 0.55% ash) is extracted with 0.4 M-NaCl-solution, the L-ascorbic acid oxidase precipitated with (NH₄)₂SO₄ and this concentrate separated by thinlayer isoelectric focussing on polyacrylamid-and dextrangel. 8–12 active fractions (isoenzymes) are detected with a high specifity forl-ascorbic acid in respect ind-isoascorbic acid activity). The molecular weights are 165,000–175,000 (determined by dextran gel-thin layer chromatography). In fresh flour the activity is near 28 mgl-ascorbic acid per kg flour in 30 min, after 30 days the activity has diminished to 5%, after 60 days no activity is detectable.

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1. Mitteilung

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Wir danken dem Forschungskreis der Ernährungsindustrie e. V. and der AIF für die finanzielle Unterstützung der Arbeit

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Experimentelle Unterlagen aus der Dissertation von S. Reoung, Universität Bonn, 1978     

Structure characterization and its antiobesity of ball-milled konjac flour

Effect of ball-milled treatment done by high-frequency oscillatory-type mill for different time on structure and antiobesity of konjac flour was investigated. Konjac flour granules became smoother and remained its original shape in the first 1.5 h treatment, however its grain size changed from 657.3 (d₅₀) to 23.7 μm (d₅₀) after 4 h treatment, which meant that the pulverized model of konjac flour was a mixture of surface pulverized model and volume pulverized model, and mainly showed by the latter. The morphology and structural change of ball-milled konjac flour was characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and electron spectroscopy for chemical analysis (ESCA). The results indicated that the crystallinity decreased while free energy increased obviously. However, thermal stability and the atomic building changed little or no. Compared with native konjac flour, the 4 h milled konjac flour could significantly decrease the body weight and total wet weight of fat of nutritional obese rats (P<0.05), and also decreased the content of triglyceride, glucose and high-density lipoprotein in blood of nutritional obese rat significantly (P<0.05). So the antiobesity effect of the 4 h milled konjac flour was significantly higher than that of the native konjac flour.     

Effect of water and guar gum content on thermal properties of chestnut flour and its starch

Thermal properties of chestnut flour and chestnut starch at several water content (40, 50, 60 and 95%, flour basis, f.b.) as well as the influence of guar gum (0.5, 1.0, 1.5 and 2.0%, f.b.) on both raw materials at fixed water content (50%, f.b.) were determined by differential scanning calorimetry (DSC). Thermal properties of guar gum–water systems at several guar content (0.5, 1.0, 1.5 and 2.0%, w/w) were also obtained by DSC. Results indicated that the water content and the presence of guar gum had a significant impact on the thermal properties of chestnut flour and its starch. For each endothermic curve, the values of onset (T_o), peaks (T_p1, T_p2) and final (T₁) temperatures decreased linearly with increasing water content. Experimental data were successfully (R² > 0.997) described following the Flory equation. A reverse trend was observed in the enthalpy values. Thermal properties of chestnut flour and chestnut starch were suppressed by the presence of guar gum even at the lowest concentrations employed (0.5%, f.b.). The guar gum addition to the assayed systems promoted a starch gelatinization delay and the enthalpy values showed a threshold content above 1.0% of guar gum. Analyses of aqueous guar gum mixtures showed that the existence of a second transition in chestnut starch systems can be successfully explained by means of hydrocolloid–starch interactions, whereas in the flour other interactions should be taken into account.     

Effects of water requirement and substitution level on wheat–rice noodles with hydrocolloids

Substitution of wheat flour with rice flour in noodles can increase rice flour utilization, reduce cost, and lower the allergenicity of wheat gluten. High‐AM rice flour (32.5%) was used to dilute high‐protein wheat flour (14.8%) on account of its excellent gel‐forming properties. Target noodles should obtain qualities comparable to noodles made from all‐purpose wheat flour (10.4% protein). RSM technique was applied for optimization of substitution level, water requirement and hydrocolloid level. The coefficient of determination (R²) showed that only substitution level and water requirement could predict textural characteristics and lightness (L*) of cooked noodles. Increased amounts of rice flour resulted in a decrease in all cooked noodle textural qualities but an increase in L*. Water absorption of rice flour was significantly higher than that of wheat flour; therefore, increased water content of substituted wheat noodles was necessary. However, water requirement should correspond well with rice substitution level. CMC was observed to be more appropriate for use in wheat–rice noodles. Wheat–rice noodles were not significantly different from wheat noodles at 30–47% substitution, water requirement 43.5–59%, and 1.2–1.5% CMC. The addition of 1.5% Na₂CO₃ resulted in a significant improvement in cooked wheat–rice noodle texture (p ≤ 0.05).     

真空碱溶液润麦处理对全麦粉稳定性和品质特性的影响

为了得到低脂肪酶活性、高稳定性的全麦粉,将小麦在不同真空度(-0.04,-0.07 MPa)下用不同浓度Na_2CO_3溶液(0.10%,0.25%,0.50%)润麦处理,利用低场核磁共振技术(LF-NMR)探究真空润麦过程中水分迁移情况,测定不同浓度Na_2CO_3溶液润麦下小麦中脂肪酶的相对活性。将润麦后的小麦制成全麦粉后,测定重组全麦粉的储藏稳定性和品质特性。结果表明:润麦过程中小麦籽粒的A_(21)值持续上升,结合水含量增加;真空碱溶液润麦可以降低小麦籽粒中脂肪酶活性,增加全麦粉贮藏稳定性,当Na_2CO_3溶液浓度为0.5%时脂肪酶活性最低;对全麦粉的粉质特性、RVA和面团流变学分析表明,真空碱溶液润麦能显著延长全麦粉的稳定时间,增强面团中面筋筋力,提高全麦粉的糊化特性,增加全麦面团的黏弹性,Na_2CO_3溶液润麦可有效改善全麦粉的品质特性。     

GLUTEN QUALITY PREDICTION AND CORRELATION STUDIES IN SPRING WHEATS

ABSTRACT

Gluten, “cohesive, viscoelastic, proteinaceous material prepared as a by‐product of the starch isolation from wheat flour” and the storage and dough‐forming protein of wheat flour, is the key to the unique ability of wheat to suit the production of leavened products. Wet gluten was only affected by wheat varieties, while dry gluten was affected by wheat varieties, crop years and their interaction. The wet and dry gluten ranged 8.0–43.13% and 2.58–14.55%, respectively, and were positively correlated with Zeleny value, sodium dodecyl sulfate sedimentation value and falling number. The gluten content was higher in Pavon, SA 42 and Faisalabad 85, while Zeleny value was higher in GA 02 and C 518, resulting in better gluten quality. Zeleny value was negatively correlated with crude protein content (r = –0.1857*). The lowest amount of wet and dry gluten was detected in Triticale and durum wheats as compared to common wheats. Zeleny value and sedimentation value may be used as indicators of gluten content and quality while working on wheats. The information thus collected will be valuable for cereal chemists and wheat breeders for improvements in their future breeding programs.

PRACTICAL APPLICATIONS

This research work will be a breakthrough and helpful for wheat breeders, growers, millers and bakers for their intended uses as every consumer demand specific wheat quality characteristics for their end products.

     

Solubilization and Electrophoretic Characterization of the Great Northern Bean (Phaseolus vulgaris L.) Proteins

Protein content of dry beans (Phaseiolus vulguris L.) cultivar Great Northern, was 26.10% (dry weight basis). The isoelectirc pH of the NaCl extractable proteins was about 4.4. Several salts, NaOH, and HCl were employed to solubilize the Great Northern bean proteins. Amongst all the protein solubilizing agents, Na₂CO₃, K₂SO₄, sodium dodecyl sulfate (SDS), and NaOH at respective concentrations of 0.5, 5, 5% (all w/v), and 0.02N were found to be better protein solubilizers than the rest; solubilizing 93.6g of Lowry protein per 100g of Kjeldahl protein. Albumins and globulins accounted for 21.18 and 73.40% respectively, of the total bean proteins. Protein content of albumins, globulins, protein concentrates, and protein isolates was 81.68, 92.26, 85.44, and 92.43% (dry weight basis) respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the bean flour, albumins, globulins, protein concentrates, and protein isolates revealed the presence of 22, 14, 10, 14, and 11 subunits, respectively. The bean flour, albumin's, globulins, protein concentrates and protein isolates were characterized by the predominance of subunits with apparent molecular weights of 294,000, 266,000, 123,000, 146,000, and 135,000 daltons, respectively. Isoelectric focusing of the bean flour, albumins, globulins, protein concentrates, and protein isolates indicated 15, 13, 15, 16, and 11 subunits, respectively. Molecular sieve chromatography of the bean flour proteins, albumins, and globulins followed by SDS-PAGE was also employed to study the complexities of these proteins.     

Tocol Composition and Supercritical Carbon Dioxide Extraction of Lipids from Barley Pearling Flour

Samples of whole grain and 35% pearling flour of 20 different barley varieties grown in Alberta were analyzed for their lipid contents. Total lipid contents of whole grains were within 1.9% to 3.0% (w/w), whereas those of the 35% pearling flour were 4.3% to 7.9%. Lipids of 35% pearling flour fraction of Tercel barley were extracted using supercritical carbon dioxide (SC‐CO₂) at different pressures (24, 45, and 58 MPa) and temperatures (40 and 60 °C) for 3 h. Lipid recoveries of 73% to 97% were achieved using SC‐CO₂ extraction under different operational conditions. Tocol contents and compositions of whole grain, 35% pearling flour, and SC‐CO₂ extracts were analyzed using HPLC. Tocol content of the whole grain was 53.8 to 124.9 μg/g and that of the pearling flour was 195 to 363 μg/g of flour. The hulless barley varieties were higher in tocols, with waxy, double waxy and Tercel varieties having the highest levels (P < 0.05). The ratios of total tocotrienols to total tocopherols varied within 1.6 to 3.9 range. Tocol concentrations of SC‐CO₂ extract fractions varied from 1171 to 4391 μg/g extract depending on the operational conditions. Barley oil is a good natural source of different tocol isomers rich in tocotrienols.