Original Flour Research Articles

Determination of alpha-gliadin content in gluten-containing and gluten-free heated food

The amount of alpha-gliadin and whole gliadin in bread dough after heating at temperatures of 50-100 degrees C was determined by ELISA. At temperatures above 80 degrees C the amount which could be found was greatly reduced. In pasta foods containing wheat (with a max. drying temperature of 75 degrees C) alpha-gliadin could be determined totally but in wheat bread (crust and crumb) only 0.5-40% of the content in the original flour was found. The results of an analysis of "gluten-free" pasta foods on the market and the amounts of alpha-gliadin found are discussed in relation to the recommendations of the Codex alimentarius (WHO).

Antinutritive Factors in Eleven Legumes and Their Air‐classified Protein and Starch Fractions

ABSTRACTPin milting and air classification of starchy legumes enriched the protein content of the light fraction to 49–75%, within the range of defatted soybean flours and protein concentrates. The levels of trypsin inhibitors, hemagglutinating activity, saponin, phytic acid and fiber were high in navy bean flour and the levels in the protein fractions of navy and northern beans greatly exceeded those of soybean flour. Potential nutritional problems in the air‐classified protein fractions of other legume species include trypsin inhibitor in lima bean and chickpea and saponin in lima bean, cowpea and lentil. Fababean and mung bean flours and protein fractions were comparatively lower in each antinutritive factor but fababean products contained vicine and convicine.SUMMARYTHE EFFECTIVENESS of the pin milling and air classification of starchy legumes in the separation of protein and starch fractions has been amply demonstrated (Sosulski and Youngs, 1979). A previous study showed that the protein fractions also contained higher levels of oligosaccharides than the original flours while the starch fractions were depleted in sugars. In the present investigation, the concentrations of trypsin inhibitor, hemagglutinating activity and phytic acid in the protein fractions were up to 300% higher than the original flour while saponins and dietary fiber also tended to segregate with the protein. The starch fractions from most of the nine legume species and biotypes were substantially detoxified by the dry milling process. The protein fractions of navy and northern beans contained particularly high levels of essentially all of the antinutritive fractions and may require extensive processing if food uses of the products are anticipated. On the other hand, mung bean and fababean products were much lower than soybean flour in most antinutritive factors although the fababean protein fraction was enriched in vicine and convicine.

Wheat Flour Proteases and Their Action on Gluten Proteins in Dilute Acetic Acid

The presence in wheat flour of several kinds of proteases was shown on the basis of pH-activity profile, substrate specificity, and response to inhibitors. Among them, 14C-hemoglobin and cbz-Phe-Ala hydrolases (14C-Hbase and CPAase) showed optimal activity around pH 4. 14C-Hbase was inhibited almost completely by pepstatin, and CPAase was partially inhibited by DFP. About 85% of 14C-Hbase activity and 40% of CPAase activity in the original flour were retained in gluten fraction. The decrease in viscosity of the gluten solution in dilute acetic acid was effectively prevented by pepstatin. An SDS-PAGE pattern showed that hydrolysis of gluten proteins was prevented effectively by pepstatin, although not completely, and that the simultaneous addition of pepstatin and DFP prevented completely self-digestion of the gluten proteins. Therefore, pepstatin and DFP sensitive proteases were shown to be responsible for the self-digestion of gluten proteins. The mode of action of these enzymes was relatively specific f...

Protein Concentrate from Air Classification of Flour and Horny Endosperm from High‐Lysine Sorghum

ABSTRACTFlour and shorts from a high‐lysine sorghum were finely ground and air classified. The protein contents of the original flour and horny endosperm were 9.9 and 18.6%, respectively, and the protein contents of the combined high‐protein fractions after air classification were 18.6 and 23.6%. These fractions accounted for 18 and 15% of the flour and horny endosperm weights and for 31 and 19% of the total protein. Protein shifts were 39% for flour and 23% for horny endosperm.

PROTEIN CONCENTRATE FROM AIR CLASSIFICATION OF HIGH‐PROTEIN SOFT WHEAT FLOURS

ABSTRACTAir classification of high‐protein soft wheat flours may have considerable commercial potential. Flours from two varieties of high‐protein soft wheat and a normal soft wheat were air classified. The protein contents of the original flours were 16.4, 12.1 and 8.2%, respectively, and the protein contents of the combined high‐protein k‐actions after air classification were 27.2, 21.5 and 17.4%. These fractions accounted for 39, 46 and 32% of the flour weight and for 65, 82 and 69% of the total protein. Protein shift was 51, 72 and 73% for the respective flours.

Yield and functional properties of air‐classified protein and starch fractions from eight legume flours

AbstractEight legumes were pin‐milled and air‐classified into protein (fine) and starch (coarse) fractions and their functional properties compared with those of soybean and lupine flours. The fine material which represented 22.5 to 29% of the original flours contained from 29 to 66% protein as well as a high proportion of the flour lipids and ash. The coarse material contained 51 to 68% starch and much of the crude fiber which was dense and concentrated in the starch fraction. Generally legumes which showed highly efficient starch fractionation gave lower recoveries of protein in the fine material. High values for oil absorption, oil emulsification, whippability and foam stability were characteristics of the protein fractions, while starch fractions gave high water absorptions, peak and cold viscosities. Gelation occurred in both air‐classified fractions. Pea and northern bean, chickpea and lima bean flours, and airclassified fractions gave generally higher values in the functional property tests, while fababean, field pea, mung bean and lentil gave high protein fractionation in the air classification process.

The stability of wheat starch lipids in untreated and chlorine‐treated cake flours

AbstractUntreated flour and flour treated with chlorine (2.2 g Cl2 kg‐1) were stored in air at 25°C for 4 months. Starch samples prepared from the original flours were stored in air at 25°C for 4 months. Starch samples were also prepared from the fresh flours (control starches) and from the stored flours. Some of the starches from the stored flours were subsequently held at 70°C for 1 month. Starch lipids were not affected by flour chlorine treatment, or by storage at 25°C. There was slight hydrolysis of starch lysophospholipids at 70°C, but negligible autoxidation of unsaturated fatty acids in the total starch lipids. There was appreciable hydrolysis of non‐starch lipids in the untreated stored flour, but no detectable autoxidation of unsaturated fatty acids. Chlorine treatment of flour caused an immediate loss of approximately half of the oleic, linoleic and linolenic acids in all the non‐starch lipids which were examined. There was no further change in the fatty acid composition of the non‐starch lipids when the treated flour was stored, but lipid hydrolysis was substantially reduced compared with the untreated stored flour.

Rapid enzymatic method for partial hydolysis of oilseed proteins for food uses.

Abstract and SummaryPlant enzymes were used to obtain partially hy‐drolyzed oilseed proteins. Hydrolysis of oilseed pro‐teins under different conditions of type of enzyme, enzyme concentration, temperature, and reaction time was investigated to develop optimum conditions. Pilot plant‐produced defatted peanut flour treated with a 0.5% aqueous solution of papain at 45 C yielded a product that had 50% more soluble protein but with no increase in the microbial count of the original flour. Hydrolysis reached equilibrium in 10‐15 min. Because of the mild reaction conditions of the method, enzymatic hydrolysis offers major advan‐tages over nonenzymatic methods for modifying plant proteins for incorporation in specialty food products.

THE FATE OF AFLATOXINS IN THE PREPARATION OF PROTEIN CONCENTRATES AND ISOLATES FROM CONTAMINATED PEANUT AND COTTONSEED FLOURS

ABSTRACTWith the assistance of the laboratories of six major soybean protein producers, simulated commercial protein concentrate and isolate processes were applied to aflatoxin‐contaminated peanut and cottonseed flours to determine the fate of the aflatoxins. Processes for producing, concentrate by washing the flour at the protein isoelectric point (pH 4.5) were ineffective in separating the aflatoxin from the products, but a process using an aqueous alcohol wash accomplished a 90% reduction in the aflatoxin level of the concentrate compared to the flour. Processes for producing isolate by protein dissolution in alkali and its recovery by precipitation at the isoelectric point resulted in some aflatoxin loss but an increase in the aflatoxin concentration associated with the protein isolate compared to the original flour. However, a process applying carbon adsorbent to the alkaline solution accomplished a 90% reduction in the aflatoxin level of the isolate.

Changes in wheat lipids during mixing and resting of flour‐water doughs

AbstractLipids extracted with water‐saturated n‐butanol from flour and flour‐water doughs were examined to determine the extent of oxidations and other changes which occurred in mixing and resting dough. Extracted lipids were converted to fatty acid methyl esters (FAME) and quantified by gas‐liquid chromatography (g.l.c.) using heptadecanoic acid (17 : 0) as internal standard. The original flour or dough and the corresponding solvent‐extracted residues were acid hydrolysed, and the hydrolysate lipids converted to FAME for g.l.c. determination of the total lipid and residual unextracted lipid contents. The total flour or dough lipids equalled the extracted lipids + unextracted lipids, except where there were unavoidable autoxidative losses of linoleate (18 : 2) and linolenate (18 : 3).The unextracted flour lipids (13% of total lipids) were not oxidised during dough mixing. There were no changes in any of the extracted lipid classes other than free fatty acids (FFA) and monoglycerides (MG) which showed losses of 18 : 2 and 18 : 3 after aerobic dough mixing. Losses of FFA and MG are attributed to lipoxygenase activity during dough mixing and the period immediately after. The small amount of 18 : 2 in the “free” petroleum ether‐extracted FFA appeared to be unaffected by lipoxygenase.Recoveries of FFA other than 18 : 2 or 18 : 3 were constant, indicating no lipolysis of glycerolipids and no general oxidation or degradation of FFA. Experiments with [U‐14C]palmitic acid confirmed that there was no oxidation, degradation or re‐esterification of FFA.Much of the non‐polar lipids (steryl ester, triglyceride, diglyceride, FFA, MG) and almost all of the polar lipids were bound on dough mixing. Binding was non‐selective with regard to fatty acid composition. Triglyceride was the only lipid class bound to a greater extent in anaerobic dough than in aerobic dough. Some selectivity of binding between lipid classes was indicated.

Changes in flour lipids during the storage of wheat flour.

AbstractHigh‐ and low‐grade spring and winter wheat flours of ∼13% moisture were stored at 15, 25 and 37 °C and the lipids were then extracted with water‐saturated n‐butanol.In the original (control) flours there were more neutral lipids and glycolipids in low‐grade winter than in high‐grade winter and in low‐grade spring than in high‐grade spring flours, but there were no corresponding differences in the amounts of phospholipids.The total extractable lipid contents of the flours remained constant in the samples stored at 15 °C, but there were slight losses in the samples stored at 25 and 37 °C. Total lipid contents determined by acid hydrolysis remained constant in all cases indicating that no loss of fatty acids had occurred on storage.There was sufficient hydrolysis of all glycerides to account for the increased amounts of free fatty acids in the stored flours. Some complete deacylation of lipids to free fatty acids and water‐soluble products was indicated. The fatty acid composition of all lipids remained constant, and there was no evidence of any lipoxygenase or other enzymic degradation of fatty acids.Stereoanalysis of the principal glycerides indicated that phosphatidylcholine (and probably also phosphatidylethanolamine) was specifically hydrolysed at the 2‐position, presumably by phospholipase‐A2. Hydrolysis of triglycerides, diglycerides and monoglycerides was attributed to the action of wheat and microbial lipases of unknown specificity. Stereoanalysis of N‐acylphosphatidylethanolamine and the galactosyldiglycerides was not attempted, but it was deduced that they were randomly hydrolysed at the 1‐ and 2‐positions. The changes found in the flour lipids differed from those reported to occur in germinating wheat and in stored damp wheat flour which had been damaged by moulds.

Effect of Rhizopus fermentation on the lipid composition of cassava flour

AbstractStudies were made on the complex lipid and fatty acid compositions of commercial cassava flour before and after nutritional ‘upgrading’ with Rhizopus arrhizus. The flour lipids closely resemble those found in other plant tissues except for a lower content of polyunsaturated acids and a higher content of free fatty acid. This can be accounted for by degradation during processing. Rhizopus fermentation leads to the appearance of γ‐linolenic acid and changes in the percentage of other acids. The total lipid content falls and the typical plant glycolipids disappear to be replaced by mould phospholipids. Sterol glycoside present in the original flour is not metabolised and becomes a major component of the final material.

A method for reconstituting fat extracted flour

Summary. A low temperature technique is described for the reconstitution of fat extracted wheat flour which allows the return of lipid material with the minimum alteration of flour properties. A study of the effect of moisture level on lipid binding in reconstituted flour is compared with a similar study of the original flour. Flours with augmented lipid contents were produced and confirmation that the method avoided the introduction of mechanical work obtained.

Distribution of Lipids in Air‐Fractionated Flours

SUMMARYLipids were extracted with petroleum‐ether, water‐saturated butanol following petroleum‐ether, or directly with water‐saturated butanol from a composite hard red winter wheat flour and from five flours separated from the original flour by air classification. The lipids were fractionated by silicic acid column and thin‐layer chromatography. Lipid contents increased as the protein contents of the flour fractions increased. The original flour contained a higher concentration of total and bound lipids than the residual coarse flour; the two flours contained comparable amounts of protein. It is postulated that shifts in particle size and in lipids during air fractionation might be responsible for differences in storability of various flour fractions as such, or in combination with other perishable food ingredients.

Study of wheat proteins soluble in water, salt solution, 70% ethanol and dilute acetic acid by starch‐gel electrophoresis

AbstractStarch‐gel electrophoresis has been used to study the compositions of several fractions obtained by extraction of hard wheat flour. The fractions soluble in water and in salt solution contained, respectively, 22 and 23 components. The extracts with 70% ethanol and dilute acetic acid each contained 10 major components and traces of others, while gluten contained 21 components. This number was reduced to 12 if the gluten was obtained from flour which had previously been extracted with water followed by salt solution. A total of 30 components appeared in a dispersion of the original flour.

Proteins of the cotton seed.

By extracting finely ground cottonseed kernels (hull-free) with benzene (C6H6) nearly all of the fatty and resinous substances and much of the coloring material is eliminated. For this purpose benzene is far superior to ether. Such a thorough removal of the above substances from the flour greatly facilitates a satisfactory subsequent extraction of the proteins by different solvents. The high percentage of nitrogen extracted by sodium chloride solution (Table I) is doubtless due to the method of preparation of the flour.We were able to separate from the salt extract two globulins. Of these one can be precipitated directly at 0.4 to 0.5 of saturation with ammonium sulfate. The other flocculates at a saturation of 0.7 to 0.8, but only after it is diluted with water so that the ratio of the final volume to the weight of the original cottonseed flour extracted is as 50:1.A fraction having a relatively low nitrogen content, but containing a constant and very high ash percentage was obtained from the salt extrac...