Differences in content and composition of free lipids and carotenoids in flour of spring and winter wheat cultivated in Poland

The work presents the content and composition of free lipids and carotenoids in spring and winter classes of wheat flour. It discusses genetical and physiological aspects of their synthesis and accumulation in wheat kernels and also indicates how methodological differences explain differences in results presented in the literature. It has been reported that spring wheat flours are richer in free lipids, especially in the non-polar fraction. The content of glycolipids ranged from 134 to 215 mg/100 g flour and was more stable within the winter wheat class. The percentages of the two main fractions, namely DGDG and MGDG, were similar in both wheat classes and reached ca. 77%. Phospholipids constituted the smallest fraction of the flour free lipids in both wheat classes; however, spring wheat flours were richer in these compounds, which is likely associated with a greater content of spherosomes in the endosperm of this wheat class. The free lipids of spring wheat flour contained more oleic and slightly less linoleic and linolenic acids. Spring wheat flour was also richer in carotenoids, although there were varieties in both classes that deviated from this. The main carotenoid was lutein, whose total percentage in the form of different isomers ranged from 71.3% to 83.3% and was slightly lower for spring wheat flour. Lutein, in the form of a trans-isomer, constituted about 62% and 70% of all carotenoids in spring and winter wheat flours, respectively.     

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

Untreated 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.     

A comparison of equilibrated lipid water systems and the effect of added lecithin on dough rheology of flour milling-streams

The lipid part of four wheat flour milling streams was extracted by ethanol. The flours were two spring wheats and two winter wheats, where one of each spring and winter wheats were obtained from the reduction-roll system and the other one from the break-roll system. Equilibrated lipid water mixtures were prepared and centrifuged to distinguish between non-polar and polar lipids. The lipids interacting with water were investigated in the microscope under polarised light to establish the presence of the lamellar liquid-crystalline phase. The stress relaxation behaviour of flour water doughs and doughs made with lamellar lecithin added were also studied. The largest amount of lipids able to form the lamellar liquid-crystalline phase was recovered for the winter wheat from the reduction milling-stream. The corresponding spring wheat also formed the lamellar phase, while the break flours did not. A large amount of oil phase was obtained from the two break flours. The rheological parameters increased to the same value for the two break flours and the two reduction flours when lecithin was added. This suggests that a flour containing protein and lipids of approximately the same quality will be improved to the same extent when lamellar lecithin is added. © SCI 1998.     

Distribution of soft wheat kernel lipids into flour milling fractions

Samples of whole and manually degermed Atou wheat were milled on a micro-mill to give straight-run flour, coarse offal, fine offal, finished bran and bran finisher flour. The non-starch lipids in these products were compared with non-starch lipids in the aleurone-free starchy endosperm, and with lipids in the germ and aleurone of the original wheat. About half of the triglyceride in flour was derived from the germ; no glycolipids or phospholipids were derived from germ, and no lipids of any kind were derived from the aleurone. Non-starch lipids in the aleurone-free endosperm of a mixed English soft wheat grist were then compared with the non-starch lipids in 11 flour streams from a commercial mill. All flours had much more triglyceride than the endosperm. In flours from the reduction system there were significant correlations between flour colour grade, sterylester, triglyceride, diglyceride, free fatty acid and diacylphospholipids, but none between ash or protein and colour or any class of lipid. Analysis of the principal components of variation in a simplified matrix describing all 11 flours placed triglyceride, diglyceride, free fatty acid, and diacylphospholipids close together in one group, and all glycolipids and N-acylphospholipids in a separate unrelated group. Sterylester and colour were loosely associated with the first group but could also be regarded as part of a third loose group with ash and protein. The results are interpreted in terms of lipid distribution within the wheat kernel, and their significance in milling and baking practice.     

Selective extraction and quantitative analysis of non-starch and starch lipids from wheat flour.

Wheat flour non-starch lipids (lipids not bound to starch) were quantitatively extracted with water-saturated n-butanol (WSB), benzene-ethanol-water (10:10:1, by vol.) or ethanol-diethyl ether-water (2:2:1, by vol.) in 10min at 20 °C. Starch lipids (lipids bound to starch) were subsequently extracted with WSB at 90–100 °C. Carotenoid pigments were quantitatively extracted with the non-starch lipids. There was no significant hydrolysis of esterified fatty acids and no detectable autoxidation of unsaturated acids in the hot solvent extracts. Non-starch and starch lipids from a high grade spring wheat flour and three grades of winter wheat flour were separated by thin-layer chromatography and quantified as fatty acid methyl esters (FAME) by gas-liquid chromatography (g.l.c.) using heptadecanoic acid (or its methyl ester) as internal standard. Total flour and starch lipids after acid hydrolysis were also converted to FAME for quantitation by g.l.c. Non-starch lipids consisted of 59–63% non-polar (neutral) lipids, 22–27% polar glycolipids and 13–16% phospholipids. Steryl esters, triglycerides, and all the diacyl galactosylglycerides and phosphoglycerides were present only in non-starch lipids. Starch lipids consisted of 6–9% non-polar (neutral) lipids (mostly free fatty acids), 3–5 % polar glycolipids and 86–91 % phospholipids (mostly lysophosphatidyl choline). Starch lipids were almost exclusively monoacyl lipids. Factors are given for converting weight of FAME into weight of original lipid for all individual lipid classes in wheat which contain O-acyl groups. Factors for total lipids are: total starch lipids = FAME × 1.70, total non-starch lipids = FAME × 1.20, and total flour (non-starch + starch) lipids = FAME × 1.32. Similar factors could be used to convert weight of lipids obtained by conventional acid hydrolysis methods into weight of unhydrolysed lipids. Phospholipid contents are given by: total starch phospholipids = P × 16.51, total non-starch phospholipids = P × 23.90, total flour phospholipids = P × 17.91.     

Effect of different milling methods on chemical composition of whole wheat flour

In order to assess the effect of different types of milling methods on protein and lipid composition of whole wheat flour, two types of wheat varieties belonging to strong and weak wheat type were selected and milled in different mills such as plate, hammer, stone and roller mills. The temperatures generated during grinding of wheat in stone, plate, hammer and roller mills were 90, 85, 55 and 35 °C respectively. The studies on SDS-PAGE indicated degradation in proteins of whole wheat flour obtained from stone and plate mills, especially in the high molecular glutenin regions. Greater loss of total amino acids was also observed in the above milled flours when compared with that of hammer and roller milled samples. Free lipid content was lower in flours milled in stone and plate mills when compared with that of flours milled in other mills. Unsaturated fatty acid content, particularly linolenic acid, was lower in stone milled flour (1.3%) followed by plate mill (2.2%), hammer mill (2.8%) and roller flour mill (3.8%). The trends in the above values as influenced by different milling methods remained similar both in the weak and strong wheat types.     

Changes of chemical composition and dough rheology in two fractions of sieve-classified Polish spring wheat flour

The study of chemical composition and dough rheology changes in sieve-classified two fractions (up to 60 and 60-240 microm particles) of wheat flour was the subject of this study. The straight grade flours were obtained by the milling of three Polish varieties of spring wheat, differing in particle size index (PSI) values. The flours were separated with the use of an SZ-1 laboratory sifter. The yield of fine fraction was in the range 50.0-55.7%. The obtained fractions were assayed for the content and composition of free lipids, gluten proteins, damaged starch, ash, water absorption and amylograph viscosity. Dough rheology (extrusion in OTMS cell, alveograph and farinograph tests) and baking trials were also performed. The content of free lipids, including the non-polar and phospholipids was lower and the content of glycolipids was higher in fine flours. Those fractions were more rich in linoleic acid but the lower content of oleic and linolenic acids resulted in a higher oxidizability index of free lipids. Fine flours contained less ash and significantly more damaged starch. At the same time, they were characterized by a higher content of wet gluten, water absorption, amylograph viscosity and better dough parameters. This was reflected in the bread volume, which was higher by 6.3-10.7%. The influence of the changes in composition and the content of free lipids upon the rheology of the dough after the 90 days flour storage has not been defined unambiguously and requires further research.     

Changes of chemical composition and dough rheology in two fractions of sieve‐classified Polish spring wheat flour

The study of chemical composition and dough rheology changes in sieve‐classified two fractions (up to 60 and 60–240 μm particles) of wheat flour was the subject of this study. The straight grade flours were obtained by the milling of three Polish varieties of spring wheat, differing in ?? abbreviation? (PSI) values. The flours were separated with the use of a SZ‐1 laboratory sifter. The yield of fine fraction was in the range 50.0–55.7%. The obtained fractions were assayed for the content and composition of free lipids, gluten proteins, damaged starch, ash, water absorption and amylograph viscosity. Dough rheology (extrusion in OTMS cell, alveograph and farinograph tests) and baking trials were also performed. The content of free lipids, including the non‐polar and phospholipids was lower and the content of glycolipids was higher in fine flours. Those fractions were more rich in linoleic acid but the lower content of oleic and linolenic acids resulted in a higher oxidizability index of free lipids. Fine flours contained less ash and significantly more damaged starch. At the same time, they were characterized by a higher content of wet gluten, water absorption, amylograph viscosity and better dough parameters. This was reflected in the bread volume, which was higher by 6.3–10.7%. The influence of the changes in composition and the content of free lipids upon the rheology of the dough after the 90 days flour storage has not been defined unambiguously and requires further research.     

The composition,rheological properties and breadmaking behaviour of stored flours

Flours milled from English (‘weak’), Canadian (‘strong’) and mixed English and Canadian wheats (‘medium’) had different rates of lipolysis (weak>medium>strong) during prolonged storage at ambient temperatures (average about 12°C). Lipolysis was more rapid in the medium flour at 25°C, but was very slow in ‘control’ flours kept at - 20°C in an inert atmosphere. Loss of baking quality in stored flours was assessed using the Chorleywood Bread Process (CBP), a long fermentation process (LFP) and the Activated Dough Development process (ADD). The loaf volume changes varied with the flour type and test method, especially depending on whether or not fat was included in the recipes. In tests with fat, the CBP was the most sensitive to deteriorative changes (strong?medium>weak); with the medium and strong flours, loaf volumes were nearly constant for 24 months before decreasing rapidly. Deterioration became apparent more gradually when using LFP and ADD tests with fat. When fat was omitted, short-term improvement (weak>medium>strong) occurred with all three baking methods, but there was subsequent loss of volume. To account for these changes in baking behaviour, it is suggested that the tests differ in their sensitivity to flour type and variations in dough composition, especially to the level of bakery fat, the level of fatty acids (generally deleterious), and to protein changes which were also detectable by rheological tests on stored flour doughs (flour ‘maturation’; generally beneficial).     

Changes in the carotenoids and sterol fractions during the prolonged storage of wheat flour

Changes in the carotenoid and sterol fractions of three wheat flours have been studied during storage. Total carotenoid decreased throughout the storage period; the relative rates of loss in each flour were the same as the relative rates of oxidation of polyenoic acids previously found to occur in these flours. Hexane-extractable total sterol content remained unchanged during storage. Esterification of free sterol was demonstrated and esterification of free lutein was also indicated.     

Fate of deoxynivalenol and nivalenol during storage of organic whole-grain wheat flour

This study was carried out to determine the level of retention of the mycotoxins deoxynivalenol (DON) and nivalenol (NIV) during 120 days of storage (aging) of flours produced from organic wheat grain naturally infected with Fusarium fungi. Three types of flour (standard white flour prepared by a roller-grinder mill - IRG, whole-grain flour produced by a hammer-crusher mill - IHC and whole-grain flour prepared by a millstone - OMS) were packaged in food-grade paper or polypropylene plastic bags and stored at two different storage temperatures (constant 10 °C or 25 °C). The concentrations of DON and NIV were measured prior to and after storage by means of HPLC-UV detection methods. After 120 days of storage, the concentrations of DON and NIV decreased between 0% and 29% compared to the initial measurements, depending on the combination of experimental factors. The greatest decrease in mycotoxin concentration was observed in the IHC and OMS flours packaged in paper bags and stored at 25 °C. The smallest decrease in mycotoxin concentration was observed in the IRG flours packaged in sealed plastic bags and stored at 10 °C. Statistical analysis showed that the level of retention of DON and NIV depended significantly on the type of packaging material, but did not depend on the type of flour or the storage temperature.     

Quality characteristics of wheat flour milled streams

In order to develop specific quality flour for use in different bakery products, quality characteristics such as sedimentation value, flour color and oil and its fatty acid composition of flour mill streams obtained from three different commercial roller flour mills were determined. The studies showed there was an increase in the sedimentation value, protein, falling number and oil and a decrease in flour color with increasing number of break flour streams, and the trend was similar for the streams obtained from the three different mills. However, no appreciable difference with regard to the above parameters was observed in reduction flour streams. Palmitic and linoleic acid contents were the predominant saturated and unsaturated fatty acids respectively present in oil of the milled streams. The levels of these fatty acids were high in V break, 1st, 2nd, 3rd and 6th reduction streams in all three mills. The flours from the reduction passages in general had more saturated fatty acid compared to break flour streams.     

Effect of buckwheat flour addition to wheat flour on acylglycerols and fatty acids composition and rheology properties

In this paper, the rheological properties and lipids composition with an emphasis on acylglycerols and fatty acids composition of dough with various portions of buckwheat flour (BWF) are investigated. The results show lipids from wheat-buckwheat flour mixture has higher ratio of total unsaturated to saturated fatty acids content (3.77-4.78 g/100 g) than those of wheat flour only (3.71 g/100 g). The value of dough water absorption (WA), development time (DT), dough stability (DSt), gelatinization temperature (T_max) and maximal pasta viscosity (η_max) increases when content of free fatty (FFA) acids increases, i.e. when buckwheat flour portion in flour mixtures increases, so FFA content has a proper influence on these dough properties. Dough with buckwheat flour has higher WA (54.3-56.0 ml/100 g), T_max (82.0-84.1 °C) and η_max (630-860 AU), longer Dst (0.7-4.6 min) and lower Dsf (82-90 FU) than dough with wheat flour only, whose appropriate values are 54.3 ml/100 g, 81.2 °C, 480 AU, 0.3 min and 90 FU, respectively. So, the flour mixture with buckwheat flour of at least 5 g/100 g can be considered good quality flour.     

Comparison of lipid effects on structural features of hard and soft wheat flour proteins assessed by front-face fluorescence

Front-face fluorescence was used to assess changes in the structural features of proteins in wheat flour dough upon addition of different exogenous lipids. Structural changes resulting from the solvation of proteins and from the mechanical deformation of proteins in dough or dough containing lipids were measured. The effects of lipid type and addition on changes in overall protein surface hydrophobicity were estimated by titrating soft and hard wheat flours, mixed with water and varying the lipid levels, with increasing concentrations of the fluorescence hydrophobic probes 1,8 anilino-napthalene-sulphonate (ANS) and thioflavin T. The lipid type and level modified the exposure of the probe to the solvent. The effects of lipids were more apparent with soft wheat flour having low-affinity hydrophobic sites on the protein surface. The dough was then characterized upon consistent mixing and physical modification in the farinograph at constant water and ANS/thioflavin T concentration, while varying the type and amount of lipids. Lipid-dependent shifts toward longer wavelengths in the probe fluorescent emission with low-protein flour suggest differences in protein coating effects related to lipid structure and protein quality.     

Influence of storage on the protein quality of pearl millet flour

Whole grain flours of two cultivars of pearl millet (Pennisetum typhoides Rich) were stored in cans for 8 days at the prevailing room temperature (25±5°C), until the flours developed an off-flavour and bad taste. The flour samples were then evaluated for protein quality. The values of protein efficiency ratio, true digestibility, biological value, net protein retention and protein utilisation fell markedly during storage. The protein quality of the cultivar with the higher amount of oil was affected more severely.     

Some observations on wheat gluten solubilities

A study of wheat protein solubilities in dilute acetic acid is presented. Up to 4% more protein can be extracted from defatted flours than from the non-defatted flour. High-speed homogenisation can render up to 88% of flour protein and up to 97% of dough protein soluble. One criterion for optimum fatty acid or lipid protein interaction (causing protein insolubility) is that the fatty acids or lipids should contain C7-C9 hydrocarbon chain lengths.     

Studies on cake quality made of wheat–chickpea flour blends

Legume flours, due to their amino acid composition and fibre content are ideal ingredients for improving the nutritional value of bread and bakery products. In this study, the influence of the total or partial replacement of wheat flour by chickpea flour on the quality characteristics of two kinds of cake was analyzed. The effects of the chickpea variety and the kind of flour used (white or whole) were also considered. Volume, symmetry, chroma, and crust and crumb L^* diminished when increasing the amount of chickpea flour. The replacement of wheat flour by chickpea flour also induced an increase in the initial firmness but cohesiveness and resilience diminished, increasing the tendency to hardening. Among the studied varieties, Pedrosillano and Sinaloa produced cakes with the highest volume. Those varieties also gave layer cakes with the lowest firmness, gumminess and chewiness. White flours produced sponge cakes with higher volume and symmetry than whole flours. No significant differences, however, were observed in layer cakes between white and whole flours. In both layer and sponge cakes, white flour produced cakes with lower firmness, gumminess and chewiness than whole flours.     

The composition of a gel formed when wheat flour is suspended in phenol-acetic acid-water (1:1:1, w/v/v)

A gel which formed when wheat flour was suspended in phenol-acetic acid-water (1:1:1, w/v/v/) was fractionated into a protein-rich soluble fraction and a carbohydrate-rich insoluble fraction. Gel electrophoresis showed that the soluble fraction contained several proteins and had an amino acid composition with a high content of proline and glutamyl residues and a low content of lysine. The soluble fraction also contained lipids which were mainly phospholipids, phospholipid derivatives and glycolipids and other compounds, which yielded galactose and glucose after acid hydrolysis. The insoluble fraction contained a polysaccharide with similar properties to starch, and lipids which were mainly neutral fats, sterols and sterol esters. Both fractions contained arabinoxylans and mannans. The gel did not contain any nucleic acids. The protein-rich soluble fractions of gels prepared from other wheat flours and air-classified flour fractions, from wheat gluten and from rye and barley flours, showed marked differences in amino acid composition. It is concluded that a heterogeneous class of proteins, rather than specific proteins in fixed proportions, is involved in gel formation.     

Supplementation of pearl millet flour with soybean protein: effect of cooking on in vitro protein digestibility and essential amino acids composition

In vitro protein digestibility (IVPD) and amino acids profile of pearl millet (Dempy cultivar) supplemented with soybean protein (5–15%) were investigated. Supplementation of dempy flour with soybean protein steadily decreased IVPD with increasing the portion of soybean in the blend. The in vitro protein digestibilities of the cooked supplemented dempy flours were higher when compared with the raw ones, whereas the highest value was that of the 5% soybean protein. All essential amino acids of dempy flour were enriched on supplementation with soybean protein. The levels of amino acids increased with increasing the amount of soybean protein in the blend. Essential amino acids in dempy supplemented with 15% soybean are comparable to those in the FAO reference pattern. Supplementation increased significantly lysine to 1.5–2.4 folds. Essential amino acids content remained higher in the cooked composite flours when compared with the cooked native dempy flour.     

Natural fermentation of lentils. Functional properties and potential in breadmaking of fermented lentil flour

The effects of fermentation on functional properties of lentil flour and rheological properties of doughs and breads produced from blends of wheat and fermented lentil flour were studied. Lentil protein solubility was higher at neutral pH than acid pH; the lowest and highest protein solubility values were observed at pH 4.0 and pH 7.0, respectively. Water hydration capacity and fat binding capacity of fermented lentil flour (FLF) were always higher than those of non-fermented lentil flour (NFLF), irrespective of fermentation temperature (28–42°C) and flour concentration (79–221 g/l). Emulsifying properties of NFLF were similar to the properties of other legume flours in the range used in experiment. In contrast, the emulsion capacity and stability of FLF were very low and flours fermented at 42°C did not even form emulsion. Rheological properties of doughs made from wheat-fermented lentil blends were similar to those from wheat flour with the addition of other legume flours such as pea and bean. Good quality breads were produced at 2.5 to 10% NFLF and FLF supplementation (except for bread with 10% FLF addition which was middle quality).