A lipase based approach for studying the role of wheat lipids in bread making

Safety evaluation of a food enzyme containing phospholipase activity produced by a strain of Fusarium commune

Phospholipases are commonly used food enzymes, e.g. to improve bread-making properties. For organic food certifications, enzymes need to be produced by non-genetically modified organisms, but no such 'classical' phospholipases are currently available. To this aim, a phospholipase product was developed with a Fusarium commune strain, a microorganism having no reported uses in the food industry. The safety of microbially-derived food enzymes depends largely on the safety of the production strain. Strain F. commune LFC was obtained by classical strain improvement. Whole-Genome Sequencing and literature search allowed to identify potential gene clusters for the mycotoxins beauvericin (BEA), moniliformin (MON), and fusaric acid (FA). Analysis of these mycotoxins revealed that no toxicologically relevant levels were produced during controlled submerged fermentation. The enzyme concentrate was assessed in a range of toxicity studies. The Ames test (OECD 471) was concluded to be equivocal, but the ToxTracker® AO assay suggested an indirect mode of action, induced by dose-dependent oxidative stress. The in vitro micronucleus test (OECD 487) and the in vivo follow-up Comet assay (OECD 489) confirmed that the food enzyme was not genotoxic. The repeated-dose oral toxicity study (OECD 408) showed no adverse effects in any of the treatment groups and allowed to derive a NOAEL of 1124 mg TOS/kg bw/day. The Margin of Exposure with estimated dietary intakes in human food applications was determined to be > 2500. It is therefore concluded that the use of the phospholipase enzyme LFC as processing aid in baking and other cereal-based applications is safe.

Lipidomic Profiling of Common Wheat Flours from 1891-2010

Wheat lipids are a minor constituent of wheat, with an important influence on its processing properties. While breeding aimed to improve the protein composition of wheat flour, its influence on the lipid composition remains unknown. We therefore analyzed the lipidome of 60 different common wheat (Triticum aestivum) flours representing cultivars registered and grown in Germany from 1891 to 2010. Four different extraction techniques were tested before the application of a semiquantitative, untargeted UHPLC-MS/MS method. The measurements included 16 different lipid classes and 102 different lipid species. Based on the lipid profile, discrimination between old (registered between 1891 to 1950) and modern (1951 to 2010) cultivars was possible. While the lipid class composition remained constant, differences were due to variations within the class of triacylglycerols, with modern cultivars containing less unsaturated fatty acids than the older ones. Our results imply that improving the lipid class composition of common wheat is a promising target for further breeding.

Changes in Lipid Metabolites and Enzyme Activities of Wheat Flour during Maturation

The maturation of wheat flour is a transformative process that elevates its processing and culinary attributes to their peak performance levels. Despite extensive research on starch and gluten protein modifications, the impact of lipid changes has been largely unexplored. This study addresses this gap by examining the maturation of freshly milled wheat flour at 15 °C, 25 °C, and 40 °C over 60 days, focusing on enzymatic activities-lipase, lipoxidase, and catalase-and lipid metabolites, including free fatty acids, conjugated trienes, p-anisidine value, and total oxidation value. The results of this study showed that free fatty acids continued to increase at all temperatures, with the most significant increase of 50% at 15 °C. The p-anisidine value followed a pattern of initial increase followed by a decline, while conjugated trienes were markedly higher at 40 °C, suggesting temperature's significant influence on lipid peroxidation. Notably, total oxidation values became erratic post 30 days, indicating a shift in oxidative dynamics. This study underscores the correlation between lipid metabolites and enzymatic activities, revealing the enzymes' pivotal role in lipid oxidation. The interplay of temperature and time offers valuable insights for optimizing wheat flour maturation, ensuring superior quality for various applications.

Recent advances in enzymatic modification techniques to improve the quality of flour-based fried foods

Flour-based fried foods are among the most commonly consumed foods worldwide. However, the sensory attributes and nutritional value of fried foods are inconsistent and unstable. Therefore, the creation of fried foods with desirable sensory attributes and good nutritional value remains a major challenge for the development of the fried food industry. The quality of flour-based fried foods can sometimes be improved by physical methods and the addition of chemical modifiers. However, enzyme modification is widely accepted by consumers due to its unique advantages of specificity, mild processing conditions and high safety. Therefore, it is important to elucidate the effects of enzyme treatments on the sensory attributes (color, flavor and texture), oil absorption and digestibility of flour-based fried foods. This paper reviews recent research progress in utilizing enzyme modification to improve the quality of flour-based fried foods. This paper begins with the effects of common enzymes on the physicochemical properties (rheological property, retrogradation property and specific volume) of dough. Based on the analysis of the mechanism of formation of sensory attributes and nutritional properties, it focuses on the application of amylase, protease, transglutaminase, and lipase in the regulation of sensory attributes and nutritional properties of flour-based fried foods.

Lipidomic insights into the reaction of baking lipases in cakes

Lipases are promising improvers of cake batter and baking properties. Their suitability for use in various cake formulations cannot be predicted yet, because the reactions that lead to macroscopic effects need to be unravelled. Therefore, the lipidome of three different cake recipes with and without lipase treatment was assessed by ultra high performance liquid chromatography-mass spectrometry before and after baking. By comparing the reaction patterns of seven different lipases in the recipes with known effects on texture, we show that lipase substrate specificity impacts baking quality. Key reactions for the recipes were identified with the help of principal component analysis. In the eggless basic cake, glyceroglycolipids are causal for baking improvement. In pound cake, lysoglycerophospholipids were linked to textural effects. Lipase substrate specificity was shown to be dependent on the recipe. Further research is needed to understand how recipes can be adjusted to achieve optimal lipase substrate specificity for desirable batter and baking properties.

Improvement of cake baking properties by lipases compared to a traditional emulsifier

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Lipases can improve the baking characteristics of different cakes.

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In comparison to DATEM they lead to softer products and less staling.

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The use of eggs or yeast diminishes the improvement by lipases.

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Lipase activity and specificity influence the extent of improvement.

Lipases are commonly used as clean-label improvers for bread. However, their potential use in cakes with different formulations remains unknown. The aim was to analyze the effects of seven baking lipases on three different cake formulations (an eggless cake, a pound cake with eggs and a yeast-based cake) in comparison to a traditional emulsifier. Product density, water loss during baking and product texture were assessed. If and to what extent the product quality was improved depended on both the lipase and the cake formulation. Lipase-induced effects mostly exceeded those of the emulsifier and were most pronounced in formulations without intrinsic emulsifiers like eggs. The lipases differed in their extent of improvement, hinting at the importance of their specific reactivity patterns and the resulting range of interactions with macromolecules. Further research is needed to unravel the mechanistic background of baking quality improvement in cakes.

A review on mechanistic aspects of individual versus combined uses of enzymes as clean label-friendly dough conditioners in breads

Numerous dough improvers are used alone or in combination to enhance the quality of baked goods such as breads. While modern consumers demand consistent quality, the expectations for ingredients have changed over the past few years, and reformulations have taken place to provide "clean label" options. However, the effects and mechanisms of blended dough conditioners suitable for such baked products have not been systematically summarized. In this review, dough and bread properties as affected by different improver combinations are examined, with a focus on additive or synergistic interactions between enzymes or between enzymes and ascorbic acid. The combination of enzymes that hydrolyze starch and cell wall polysaccharides has been shown to reduce textural hardness in fresh and stored bakes goods such as breads. Enzymes that hydrolyze arabinoxylans, the main nonstarch polysaccharide in wheat, have synergistic effects with enzymes that result in cross-linking of wheat flour biopolymers. In some studies, the effects of bread improvers varied for wheat flours of different strength. Overall, bread products in which wheat is used in whole grain form or in a blend with other flours especially benefit from multiple improvers that target different flour constituents in doughs.

Enzymatic modifications of gluten protein: Oxidative enzymes

Oxidative enzymes treat weak flours in order to restore the gluten network of damaged wheat flour and reduce the economic and technological losses. The present review concentrates on oxidative exogenous enzymes (transglutaminase, laccase, glucose oxidase, hexose oxidase) and oxidative endogenous enzymes (tyrosinase, peroxidase, catalase, sulfhydryl oxidase, lipoxygenase, lipase, protein disulfide isomerase, NAD(P)H-dependent dehydrogenase, thioredoxin reductase and glutathione reductase) and their effects on the rheological, functional, and conformational features of gluten and its subunits. Overall, transglutaminase is used in wheat-based foods through introducing isopeptide bonds (ε-γ glutamyl-lysine). Glucose oxidase, hexose oxidase, peroxidase, sulfhydryl oxidase, lipase, and lipoxygenase form disulfide and nondisulfide bonds through producing hydrogen peroxide. Laccase, tyrosinase, and protein disulfide isomerase form cross-links between tyrosine and cysteine residues by generating radicals. Thioredoxin reductase and glutathione reductase create new inter disulfide bonds. The effect of oxidative enzymes on the formation of covalent cross-linkages were substantially more than non-covalent bonds in gluten structure.

Normal-Phase HPLC-ELSD to Compare Lipid Profiles of Different Wheat Flours

Normal-phase high-performance liquid chromatography (HPLC) is widely used in combination with evaporative light scattering detection (ELSD) for separating and detecting lipids in various food samples. ELSD responses of different lipids were evaluated to elucidate the possibilities and challenges associated with quantification by means of HPLC-ELSD. Not only the number and type of polar functional groups but also the chain length and degree of unsaturation of (free or esterified) fatty acids (FAs) had a significant effect on ELSD responses. Tripalmitin and trilinolein yielded notably different ELSD responses, even if their constituting free FAs produced identical responses. How FA structure impacts ELSD responses of free FAs is thus not predictive for those of triacylglycerols and presumably other lipids containing esterified FAs. Because ELSD responses of lipids depend on the identity of the (esterified) FA(s) which they contain, fully accurate lipid quantification with HPLC-ELSD is challenging and time-consuming. Nonetheless, HPLC-ELSD is a good and fast technique to semi-quantitatively compare the levels of different lipid classes between samples of comparable FA composition. In this way, lipid profiles of different flours from near-isogenic wheat lines could be compared.

Optimization of gluten-free sponge cake fortified with whey protein concentrate using mixture design methodology

This study aimed to optimize mixtures of whey protein concentrate (WPC) and two flours of rice and maize flours for the production of gluten-free sponge cakes. This was obtained by using mixture design methodology. WPC incorporation had positive effects on specific volume and baking loss of cakes, whilst, their incorporation increased their hardness. Considering all cakes properties, two formulas F1 (78.5% Maize, 15% Rice and 6.5% WPC) and F2 (82.4% Maize, 12% Rice and 5.6% WPC) were optimized using a mixture design. The microstructure F1 was more organized and very well structured with smaller aggregates. According to the organoleptic evaluation, F1 was also most appreciated by the tasting panel. The findings of the present study indicated that maize and rice flours, and WPC could be used as a substitute for wheat flour in producing sponge cakes of high quality.

Cereal bran protects vitamin A from degradation during simmering and storage

Food supplementation with vitamin A is an efficient strategy to combat vitamin A deficiency. The stability of vitamin A during cooking and storage is, however, low. We here show that cereal bran protects retinyl palmitate (RP) during simmering and storage. Native wheat bran stabilized RP the most during simmering. About 75% RP was recovered after 120 min of cooking, while all RP was lost after 80 min in the absence of bran. Heat-treated rice bran protected RP the best during forced storage, with a 35% recovery after 8 weeks. RP was degraded entirely in the absence of bran in less than one week. Results suggested that the physical entrapment of oil within the large wheat bran particles protects RP from the action of water and pro-oxidants during simmering. During storage, the high amount and diversity of lipid components present in rice bran are presumably responsible for its protective effect.

Genetic variation in wheat grain quality is associated with differences in the galactolipid content of flour and the gas bubble properties of dough liquor

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A QTL for breadmaking quality is associated with more galactolipids in flours.

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Dough liquor fractions from the same flours also have higher galactolipid contents.

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The dough liquor fractions with higher galactolipids exhibit increased elasticity.

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These increases indicate a mechanism of action for the quality QTL.

Lipids affect the quality of wheat flour for breadmaking. One possible mechanism is stabilization of the gas cells which are formed during dough mixing and expanded during fermentation, leading to a greater loaf volume and evenness of texture. We therefore compared the lipidomic profiles of flour and dough liquor fractions (which contain surface-active components present at the gas bubble interface) from two sets of wheat lines differing in allelic variation at a QTL for loaf volume. Analyses of fractions from three field trials showed consistent increases in the contents of galactolipids (monogalactosyl diglyceride and digalactosyl diglyceride) in flour and dough liquor of the lines with the increasing (good quality) allele. Biophysical analysis showed that this was associated with greater elasticity of the dough liquor fraction. This is consistent with published studies reporting a relationship between galactolipids and breadmaking quality and suggests a mechanism of action for the QTL.

Do puroindolines affect the impact of enzymatic lipid hydrolysis on loaf volume in bread making?

This paper is the first to study whether and how interactions between puroindolines (PINs) and lipids affect bread loaf volume (LV). Flour from near-isogenic wheat lines differing in PIN haplotype and lipases were used in bread making. That lipase impact on LV strongly depended on the flour used supported the hypothesis that PINs modify the impact of enzymatic lipid hydrolysis on LV. In dough prepared from gluten-starch blends (GSB) differing in PIN levels, PINs did not affect enzymatic lipid hydrolysis itself. Gas cells in these GSB doughs were apparently not surrounded by surface-active compounds so that the impact of PIN-lipid interactions on LV could not be evaluated. This allowed concluding that lipase impact on LV is exclusively related to stabilization of gas cell interfaces in dough since lipase application did not change GSB LVs. Our results advance knowledge on PIN-lipid interactions and the impact of lipases in bread making.

Bovine Milk Fats and Their Replacers in Baked Goods: A Review

Milk fats and related dairy products are multi-functional ingredients in bakeries. Bakeries are critical local industries in Western countries, and milk fats represent the most important dietary lipids in countries such as New Zealand. Milk fats perform many roles in bakery products, including dough strengthening, textural softeners, filling fats, coating lipids, laminating fats, and flavor improvers. This review reports how milk fats interact with the ingredients of main bakery products. It also elaborates on recent studies on how to modulate the quality and digestibility of baked goods by designing a new type of fat mimetic, in order to make calorie- and saturated fat-reduced bakery products. It provides a quick reference for both retailers and industrial manufacturers of milk fat-based bakery products.

Effects of starch addition on the activity and specificity of food-grade lipases

Lipases are surface-active enzymes, acting on their substrates at the polar/nonpolar interface in emulsions. This study was aimed to test whether their activity, specificity, and the rates of formation/degradation of the various hydrolysis intermediates (i.e., mono- and diglycerides of interest as surface-active agents) could be modulated by adhesion of the triglyceride substrates as a thin layer on the surface of solids. These hypotheses were tested by using an array of food-grade lipases used in bakery, testing various types of starch as the "solid" phase. Starch-dependent increase in the hydrolysis rate was tested by pH-stat techniques on pure triglycerides and on food-grade oils in diluted emulsions. Starch-related improvements in the rate of fatty acids release were most evident at temperatures above 40 °C, and when using maize starch instead of wheat starch. Starch-dependent changes in the nature of the hydrolysis products were tested by chromatographic profiling of ethyl ether extracts from aqueous slurries containing up to 33% fat and 33% starch. Accumulation of mono- and diglycerides as hydrolysis intermediates was found to be modulated by the type of oil being used, by the reaction conditions, as well as by the enzyme nature and amount.

Wheat (Triticum aestivum L.) flour free lipid fractions negatively impact the quality of sponge cake

The functionality of wheat flour lipids in sponge cakes prepared from flour, sugar, eggs and leavening agents only was investigated by altering their location or content in flour. Hexane (hex) or the more polar hexane:isopropanol (3:2 v/v) (hex:isoprop) were used to impact free flour lipid (FFL) or both FFL and bound flour lipid (BFL) fractions, respectively. Flour from which the FFLs were removed resulted in significantly improved cake volumes and crumb structures. Additional removal of part of the BFLs did not further impact cake quality. Prior contact of flour with hex:isoprop followed by gently removing the solvent broke native interactions between BFLs and starch or gluten and relocated more lipids than did hex. Cakes from flour with relocated lipids had coarse crumb structures. Our study demonstrates that FFLs and relocated flour lipids negatively impact sponge cake quality by disturbing air-liquid interface stabilization during mixing and the early phases of baking.

Relating the composition and air/water interfacial properties of wheat, rye, barley, and oat dough liquor

Gas cell stabilization in dough by its aqueous phase constituents is arguably more important in non-wheat than in wheat dough due to weaker protein networks in the former. Dough liquor (DL), a model for the dough aqueous phase, was isolated from fermented wheat, rye, barley, and oat doughs by ultracentrifugation. DL composition (protein, lipid, arabinoxylan, β-glucan) and air/water interfacial functionality [foaming, viscosity, surface tension, surface dilatational modulus (E)] were related to bread quality. Poor foaming and low E of wheat DL were ascribed to lipids and proteins co-occurring at the interface. Nonetheless, the presence of a gluten network resulted in high-quality wheaten breads. Homogeneous and heterogeneous crumb structures of rye and barley breads, respectively, were attributed to high and low E values of their respective DLs. High lipid content and low surface tension of oat DL indicated a lipid-dominated interface, which may explain the heterogeneous crumb structure of oat breads.

Intrinsic wheat lipid composition effects the interfacial and foaming properties of dough liquor

Doughs were prepared from a single variety breadmaking flour (cv. Hereward), from three successive harvests (years; 2011, 2012 and 2013). A preparation of the aqueous phase from dough, known as dough liquor (DL), was prepared by ultracentrifugation and its physico-chemical properties were investigated. Surface tension and interfacial rheology, showed that the interface of DL was lipid-dominated and that 2013 DL had a different type of interface to 2011 and 2012 DL. This data was consistent with the improved foam stability observed for 2013 DL and with the types of lipids identified. All foams collapsed quickly, but the most stable foam was from 2013 DL with 89.2% loss in foam, followed by 2011 DL with 91.7% loss and 2012 had the least stable foam with a loss of 92.5% of the foam structure. Glycolipids (DGDG and MGDG) were enriched in 2013 DL, and were also present in DL foam, contributing towards improved stability. Neutral lipids, such as FFAs, were enriched in DL foams contributing towards instability and rapid foam collapse. Baking trials using 2012 and 2013 flour, showed increased loaf volumes and gas bubble diameter in 2013 bread compared to 2012 bread, highlighting the potential impact that surface active polar lipids, enriched in the aqueous phase of dough, could have on improving breadmaking quality.

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During proving, gas bubble stability is determined by the types of lipids adsorbed at the air-water interface of the aqueous phase.

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Both proteins and lipids were active at the air-water interface of dough liquor (DL), but it was dominated by lipids.

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FFAs were enriched in DL foams and were detrimental to foam stability, whilst Polar lipids were enriched in DL.

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Greatest loaf volumes were generated from flour that produced DL with the highest enrichment of polar lipids.

A novel galactolipase from a green microalga Chlorella kessleri: purification, characterization, molecular cloning, and heterologous expression

We have identified an enzyme, galactolipase (ckGL), which hydrolyzes the acyl ester bond of galactolipids such as digalactosyldiacylglycerol (DGDG), in the microalga Chlorella kessleri. Following purification of the enzyme to electrophoretic homogeneity from cell-free extract, the maximum activity toward DGDG was observed at pH 6.5 and 37 °C. ckGL was Ca²⁺-dependent enzyme and displayed an apparent molecular mass of approx. 53 kDa on SDS-PAGE. The substrate specificity was in the order: DGDG (100%) > monogalactosyldiacylglycerol ≈ phosphatidylglycerol (~ 40%) > sulfoquinovosyldiacylglycerol (~ 20%); the enzyme exhibited almost no activity toward glycerides and other phospholipids. Gas chromatography analysis demonstrated that ckGL preferably hydrolyzed the sn-1 acyl ester bond in the substrates. The genomic DNA sequence (5.6 kb) containing the ckGL gene (designated glp1) was determined and the cDNA was cloned. glp1 was composed of 10 introns and 11 exons, and the 1608-bp full-length cDNA encoded a mature ckGL containing 475 amino acids (aa), with a presequence (60 aa) containing a potential chloroplast transit peptide. Recombinant functional ckGL was produced in Escherichia coli. Although the deduced aa sequence of ckGL contained the typical GXSXG motif of serine hydrolases together with conserved histidine and aspartate residues which would form part of the catalytic triad of α/β-hydrolases, ckGL showed no significant overall similarity with known lipases including GLs from Chlamydomonas reinhardtii and Aspergillus japonicus, indicating that ckGL is a novel GL. ckGL, with high specificity for DGDG, could be applicable to food processing as an enzyme capable of improving material textures.

Effects of Cultivar and Nitrogen Nutrition on the Lipid Composition of Wheat Flour

Despite being minor components of flour, wheat (Triticum aestivum L.) lipids contribute to grain processing. They are particularly important for bread making, where they adsorb to the surface of gas bubbles formed during the proving stage of bread making, stabilizing the gas cells and improving gas retention within the dough. This contributes to the volume and texture of the loaf. However, little is understood about how their amount, composition, and properties vary in response to genotype (G), environment (E) or G × E interactions. Six wheat lines were therefore grown at three levels of nitrogen supply at Rothamsted Research, and 48 lipid species across six lipid classes were identified and quantified in white flour using electrospray ionization-tandem triple quadrupole mass spectrometry (ESI-MS/MS). This showed clear differences in the contents and compositions of lipids between cultivar as well as effects of nitrogen fertilization, which would be expected to have impacts on the processing properties of the samples.

Genotypic Variation in Wheat Flour Lysophospholipids

Lysophospholipids (LPLs) are the most abundant polar lipids in wheat endosperm and naturally complex with amylose, affecting starch physicochemical properties. We analyzed LPLs in wheat flour from 58 cultivars which differ by grain hardness using liquid chromatography mass spectrometry (LCMS). There were significant differences in LPL content between cultivars, demonstrating that genotype rather than environment contributes most to the total variance in wheat endosperm LPLs. Polar lipids such as LPLs may play a role in grain hardness through their interaction with puroindoline proteins, however, no strong correlation between kernel hardness and LPLs was detected. This may reflect the location of LPLs within the starch granule as opposed to the puroindoline proteins outside starch granules. LPLs may have an indirect relationship with kernel hardness as they could share the same origin as polar lipids that interact with puroindoline on the starch granule surface.

Lipases as Processing Aids in the Separation of Wheat Flour into Gluten and Starch: Impact on the Lipid Population, Gluten Agglomeration, and Yield

Three lipases with different hydrolysis specificities were tested in a laboratory-scale dough-batter wheat flour separation process in two concentrations. Lipolase specifically hydrolyzed nonpolar flour lipids. At the highest concentration tested, it significantly improved gluten agglomeration and yield, also when combined with a xylanase with hydrolysis specificity toward water-extractable arabinoxylan. We hypothesize that its action is due to the release of adequate levels of free fatty acids, which, because at least a part of them is dissociated, act as anionic surfactants. Lipolase at the lowest concentration, Lecitase Ultra, hydrolyzing both nonpolar and polar lipids, and YieldMAX, which specifically hydrolyzed phospholipids, had no or a negative impact on gluten agglomeration and yield. In conclusion, this study demonstrated that lipases with hydrolysis specificity toward nonpolar lipids can be used as processing aids in wheat flour separation in the absence or presence of added xylanases to maximize gluten agglomeration and yield.

Distribution of Lipids in the Grain of Wheat (cv. Hereward) Determined by Lipidomic Analysis of Milling and Pearling Fractions

Lipidomic analyses of milling and pearling fractions from wheat grain were carried out to determine differences in composition that could relate to the spatial distribution of lipids in the grain. Free fatty acids and triacylglycerols were major components in all fractions, but the relative contents of polar lipids varied, particularly those of lysophosphatidylcholine and digalactosyldiglyceride, which were enriched in flour fractions. By contrast, minor phospholipids were enriched in bran and offal fractions. The most abundant fatty acids in the analyzed acyl lipids were C16:0 and C18:2 and their combinations, including C36:4 and C34:2. Phospholipids and galactolipids have been reported to have beneficial properties for breadmaking, whereas free fatty acids and triacylglycerols are considered detrimental. The subtle differences in the compositions of fractions determined in the present study could therefore underpin the production of flour fractions with optimized compositions for different end uses.