Antioxidant properties of wheat mill streams

Knowing the quality of mill streams is very important for getting flours with improved quality. In the present work, 49 mill streams, obtained by milling common wheat with an industrial roller mill, were characterized in terms of phenolic content, antioxidant activity and iron content. The antioxidant activity was estimated using different methods: DPPH-radical scavenging, Trolox equivalent antioxidant capacity, and iron reducing antioxidant power. The break tailings and first tailings of the reduction passages had the largest contents of iron. The total phenolic contents (TPC) from flour streams ranged between 76.3 and 369 mg ferulic acid equivalent/100 g d.w. The highest TPC were obtained for the second fractions resulting from 1st and 2nd break rolls. The highest antioxidant activity was registered for flour streams collected from: the last two break rolls, the reduction rolls that process the tailings of the first three reduction passages and bran finisher. Trolox equivalent antioxidant capacity had the same trend as DPPH-radical scavenging activity. The highest iron reducing antioxidant power was found in the tailings of the reduction rolls. The knowledge provided by this study could be successfully applied for getting flour with improved antioxidant activity and iron content by mixing different types of mill streams.     

Mechanisms Leading to Excess Alpha -Amylase Activity in Wheat (Triticum aestivum, L) Grain in the U.K.

The frequency and mechanisms of four modes of alpha -amylase enzyme accumulation in U.K. wheat, retained pericarp alpha -amylase activity (RPAA), pre-maturity alpha -amylase activity (PMAA), pre-maturity sprouting (PrMS) and post-maturity sprouting (PoMS), were investigated in field and laboratory experiments. Of 56 cultivar site year combinations (four model cultivars grown at up to four sites from 1994–1997), enzyme activity was detected in 32 cases, in 23 cases sufficient to reduce Hagberg falling number (the usual industry measure of alpha -amylase) below the commercial criterion (250 s). The frequency of occurrence of different modes of enzyme accumulation was in the order PoMS>PMAA>PrMS>RPAA. Both PMAA and PrMS were more common than expected and the most usual pattern was for alpha -amylase to accumulate by several modes. Although green grains are rejected as impurities, study of grain colour in relation to pericarp alpha -amylase activity showed that the enzyme could persist in non-green grains in levels sufficient to affect the Hagberg value. Two factors thought to promote PMAA, grain drying rate and transient changes in temperature in early development, were studied in the field and controlled environment cabinets. No significant difference was found in grain drying rate between samples where PMAA was or was not identified. However, out of 19 transfers from a cool (16/10 °C) to a warm (26/20 °C) temperature regime, six led to significant increases in PMAA. No transfers after 45% grain moisture increased PMAA. PrMS occurred as early as 67% grain moisture and susceptibility usually increased with stage of development, being greatest in the grain dough stage. PrMS susceptibility varied with cultivar (in the same order as PoMS sensitivity) and was affected by environmental factors.     

Protein Inhibitors ofAlpha-amylase in Mature and Germinating Grain of Rye (Secale cereale)

The activities of endogenous (R-type) and exogenous acting (D-type) protein inhibitors ofalpha-amylase and the activities ofalpha- and total amylase were determined in milling fractions of rye. High D-type amylase inhibitor activities were detected in the embryo (255 IU/g) and in the endosperm fraction (64·9 IU/g), low inhibitor activities were found in the aleurone layer fraction (25·9 IU/g). The highest R-typealpha-amylase inhibitor activity was found in the aleurone layer fraction (32·6 IU/g), and the lowest value in the epidermis containing fraction (5·0 IU/g). The D- and R-typealpha-amylase inhibitor activities varied with growing conditions. D-type amylase inhibitor activities were found to be high in those samples which grew under drought conditions and low in samples cultivated under wet and cool weather. Higher R-typealpha-amylase inhibitor activities were found in rye genotypes cultivated under wet conditions and lower values under dry weather. There were small variations inalpha-amylase inhibitor activities between sprout-stable and sprout-sensitive rye genotypes. The D- and R-typealpha-amylase inhibitor activities of all varieties were stable during 72 h of germination. Similar soil conditions will therefore lead to differentialalpha-amylase inhibitor activities depending on weather conditions during growth.     

Molecular weight distribution and content of water-extractable β-glucan in rye crisp bread

Rye crisp doughs and breads were made from three rye flours with different falling numbers (i.e. different enzyme activity), with or without oat bran rich in β-glucan (OBG) added, and with different fermentation times. The aim of the study was to investigate the effect of endogenous enzymes in the flour on molecular weight and content of water-extractable β-glucan in the doughs and breads. The molecular weight distribution of β-glucan was unimodal for the flours, with a calcofluor average molecular weight of about 90×10⁴ g/mol for the rye flours, and 150×10⁴ g/mol for rye flours with added OBG. The molecular weight decreased with increasing fermentation time for all doughs, but was almost unchanged during oven-baking. The calcofluor average molecular weight was highest in doughs and breads made of flour with highest falling number (i.e. lowest enzyme activity), indicating that the endogenous enzymes in the flour were responsible for the breakdown of β-glucan. During fermentation, water-extractable β-glucan was released from the insoluble matrix, probably by the endogenous enzymes in the flour. When the molecular weight of the water-extractable β-glucan decreased, they probably associated with each other or with other components in the dough to form unextractable complexes. The content of water-extractable β-glucan did not change during oven-baking.     

Polyphenol oxidase,alpha-amylase and beta-amylase activities of Triticum monococcum, Triticum turgidum and Triticum aestivum: A two-year study

Enzymatic activity often reduces the nutritional value of wheat flour during food manufacturing, causing compound degradation and/or heat damage. The choice of wheat varieties with low enzymatic activity could therefore help to preserve the nutritional quality of food. The aim of this research was to evaluate polyphenol oxidase, alpha-amylase and beta-amylase activities in whole meal flours of 59 accessions belonging to different wheat species and subspecies, cropped in two years. The extraction pH (7.0), reaction pH (5.5) and reaction temperature (45 °C) were determined by preliminary trials. The ANOVA highlighted significant differences for all enzymes among species/subspecies and, for amylases, between cropping years; however, the year influence was overwhelming only for alpha-amylase. Einkorn showed the highest polyphenol oxidase (362.1 ± 9.46 U/g DM) as well as the lowest alpha-amylase (0.20 ± 0.006 CU/g DM) and beta-amylase (12.0 ± 0.36 B3U/g DM) activities. The embryo/scutellum had the highest polyphenol oxidase and alpha-amylase values, followed by the bran and the endosperm; in contrast, beta-amylase was evenly distributed in the bran and the endosperm, and was absent in the embryo/scutellum.     

Mineral element distributions in milling fractions of Chinese wheats

Malnutrition related to micronutrient deficiency can create immense economic and societal problems. The objective of this study was to quantify the mineral element concentration distribution in milled fractions, using 43 common wheat (Triticum aestivum L.) cultivars sown in Jinan, China during the 2005–2006 crop season. All 43 cultivars had low Fe (average 28.2 mg Kg⁻¹) and Zn (28.6 mg Kg⁻¹) concentrations, and wide ranges of variation for mineral element concentrations. Highly significant effects among milling fractions and cultivars on all traits were observed, with fraction effect being the larger. There was an uneven distribution of mineral element concentrations in wheat grain. Shorts and bran fractions had the highest mineral element concentrations, whereas flours from break and reduction had low concentrations. Compared with those in the central endosperm, the concentration of inorganic phosphorus (Pi) decreased the most with decreasing flour yield, whereas the concentration of phytic acid P (PAP), phytase activity, and Ca decreased the least. Pi was the most concentrated element in the aleurone, whereas PAP, phytase activity, and Ca were the least, compared to those in the central endosperm. Milling technique through adjusting flour yield can be used to improve the element composition of flour.     

Debranning of wheat prior to milling reduces xylanase but not xylanase inhibitor activities in wholemeal and flour

Debranning of wheat to remove the outer 7% of the kernel, prior to grinding or milling reduced xylanase activity in wheat wholemeal and wheat endosperm flour by up to 80 and 60%, respectively, whereas there was no significant reduction of xylanase inhibiting activity. Flours obtained after debranning and milling showed no major differences in moisture content, whereas ash content decreased and protein and arabinoxylan content decreased slightly with increasing debranning degree. Part of the xylanase activity in the flour was lost on addition of Triticum aestivum xylanase inhibitor (TAXI). Since TAXI specifically inhibits glycosyl hydrolase family 11 xylanases and since endogenous cereal xylanases belong exclusively to family 10, part of the xylanase activity in the flour is most likely of microbial origin. Debranning also significantly reduced alpha-amylase activities in wheat wholemeal and wheat flour. Debranning prior to milling can, therefore, impact on flour functionality.     

Effect of particle size on kinetics of starch digestion in milled barley and sorghum grains by porcine alpha-amylase

The influence of milled grain particle size on the kinetics of enzymatic starch digestion was examined. Two types of cereals (barley and sorghum) were ground, and the resulting grounds separated by size using sieving, with sizes ranging from 0.1 to 3 mm. In vitro enzymatic digestion was performed, using pancreatic alpha-amylase, amyloglucosidase and protease, to determine fractional-digestion rates over 24 h. The resulting glucose production rate data were well fitted by simple first-order kinetics. For each sieve screen size, the digestion rate of barley was always higher than that of sorghum. The rate coefficients for digestion showed a decrease with increasing size, and could be well fitted by an inverse square relationship. This is consistent with the supposition that starch digestion in these systems is controlled by diffusion of enzyme through the grain fragment. Apparent diffusion coefficients of alpha-amylase obtained by fitting the size dependence were 0.76 (sorghum) and 1.7 (barley) × 10⁻⁷ cm² s⁻¹, 9 (sorghum) and 4 (barley) times slower than predicted for a molecule of the size of alpha-amylase in water.     

Assessment of antioxidant activity and rheological properties of wheat and buckwheat milling fractions

This study examined the antioxidant properties of the ethanolic extracts of wheat milling fractions (wheat flour type 500 and type 850, and bran) and their polyphenol and tocopherol content, and rheological characteristics of wheat dough supplemented with buckwheat flours (light and wholegrain). The results obtained in this study were correlated with our previously published data on wheat flour type 400, wholegrain wheat flour and buckwheat flours.Buckwheat flours exhibited significantly higher (P < 0.05) antiradical activity on hydroxyl (OH), superoxide anion (O₂⁻) and (1,1-diphenyl-2-picrylhydrazyl) DPPH radicals, antioxidant activity and reducing power than all investigated wheat milling fractions when their corresponding IC₅₀ values were compared.The rheological parameters of wheat dough supplemented with light and wholegrain buckwheat flour (0-50%) were obtained by using Mixolab. Results indicated changes in protein and starch properties of dough.The obtained results indicate the benefit of using buckwheat flours in wheat-based food products, i.e. their contribution in functional and tailor-made-food production.     

Mineral element distributions in milling fractions of Chinese wheats

Malnutrition related to micronutrient deficiency can create immense economic and societal problems. The objective of this study was to quantify the mineral element concentration distribution in milled fractions, using 43 common wheat (Triticum aestivum L.) cultivars sown in Jinan, China during the 2005–2006 crop season. All 43 cultivars had low Fe (average 28.2 mg Kg⁻¹) and Zn (28.6 mg Kg⁻¹) concentrations, and wide ranges of variation for mineral element concentrations. Highly significant effects among milling fractions and cultivars on all traits were observed, with fraction effect being the larger. There was an uneven distribution of mineral element concentrations in wheat grain. Shorts and bran fractions had the highest mineral element concentrations, whereas flours from break and reduction had low concentrations. Compared with those in the central endosperm, the concentration of inorganic phosphorus (Pi) decreased the most with decreasing flour yield, whereas the concentration of phytic acid P (PAP), phytase activity, and Ca decreased the least. Pi was the most concentrated element in the aleurone, whereas PAP, phytase activity, and Ca were the least, compared to those in the central endosperm. Milling technique through adjusting flour yield can be used to improve the element composition of flour.     

Effect of Grain Structure and Cooking on Sorghum and Maize in vitro Protein Digestibility

Uncooked and cooked sorghum showed improvement in in vitro protein digestibility as the structural complexity of the sample reduced from whole grain flour through endosperm flour to protein body-enriched samples. This was not the case for maize. Cooking reduced protein digestibility of sorghum but not maize. Treating cooked sorghum and maize whole grain and endosperm flours with alpha -amylase to reduce sample complexity before in vitro pepsin digestion slightly improved protein digestibility. The reduction in sorghum protein digestibility on cooking was not related to the total polyphenol content of samples. Pericarp components, germ, endosperm cell walls, and gelatinised starch were identified as possible factors limiting sorghum protein digestibility. Electrophoresis of uncooked and cooked protein-body-enriched samples of sorghum and maize, and prolamin fractions of sorghum under non-reducing conditions showed oligomeric proteins with molecular weights (M_r) 45, 66 and >66 kDa and monomeric kafirins and zeins. Protein-body-enriched samples of sorghum had more 45–50 kDa oligomers than those of maize. In cooked sorghum, some of these were resistant to reduction. Pepsin-indigestible residues from protein-body-enriched samples consisted mainly of α-zein (uncooked and cooked maize) or α-kafirin (uncooked sorghum), whilst cooked sorghum had in addition, β- and γ-kafirin and reduction-resistant 45–50 kDa oligomers. Cooking appears to lead to formation of disulphide-bonded oligomeric proteins that occurs to a greater extent in sorghum than in maize. This may explain the poorer protein digestibility of cooked sorghum.     

Developmental Expression of Amylases During Barley Malting

Amylase activity and qualitative changes in amylase isoenzymes as a function of barley seedling age were investigated in 10 Brazilian barley cultivars. All cultivars showed few isoenzymes in early germination. An increase in general activity ensued in the following days when new isoenzymes were detected and those already observed since early germination had their activity increased. All cultivars disclosed increase in amylase activity until the third or fourth day of germination. Some cultivars maintained this high activity until the last day analysed. Other cultivars presented a decrease in activity in the fifth or sixth day. No electrophoretic pattern or allelomorph responsible for a higher amylase activity were detected. Beta -amylase activity was always superior to alpha -amylase activity. High beta -amylase activity was already observed on the second day of germination while alpha -amylase activity began to increase only from the third day on. The results obtained suggest that, at least for the cultivars analysed, there is a high general amylase activity around the fourth day of germination, indicating that germination could stop at this moment, ensuring that hydrolitic enzyme activity required in the brewing process is met. Beta -amylase was lightly correlated with diastatic power (r=0·565) but no correlation was observed between alpha -amylase and diastatic power (r=-0·128), or neither betweenalpha - and beta -amylase with malting quality (r=0·153 andr =−0·348, respectively). These results indicate that beta -amylase activity in barley grains, more than alpha -amylase, can be a good predictor of diastatic power.     

Effects of endosperm texture and cooking conditions on the in vitro starch digestibility of sorghum and maize flours

The effects of endosperm vitreousness, cooking time and temperature on sorghum and maize starch digestion in vitro were studied using floury and vitreous endosperm flours. Starch digestion was significantly higher in floury sorghum endosperm than vitreous endosperm, but similar floury and vitreous endosperm of maize. Cooking with 2-mercaptoethanol increased starch digestion in both sorghum and maize, but more with sorghum, and more with vitreous endosperm flours. Increasing cooking time progressively reduced starch digestion in vitreous sorghum endosperm but improved digestibility in the other flours. Pressure-cooking increased starch digestion in all flours, but markedly more in vitreous sorghum flour; probably through physical disruption of the protein matrix enveloping the starch. Irrespective of vitreousness or cooking condition, the alpha-amylase kinetic constant (k) for both sorghum and maize flours remained similar, indicating that differences in their starch digestion were due to factors extrinsic to the starches. SDS-PAGE indicated that the higher proportion of disulphide bond-cross-linked prolamin proteins and more extensive polymerisation of the prolamins on cooking, resulting in polymers of M_r>100k, were responsible for the lower starch digestibility of the vitreous sorghum endosperm flour.     

Studies on multigrain milling and its effects on physical,chemical and rheology characteristics of milled streams

The multigrain blends of wheat-green gram-barley in the ratio of C (100:0:0); B1 (90:5:5); B2 (80:10:10); B3 (70:15:15) were co milled using a Buhler roller mill to produce nutritious flour. The studies showed that the yield of straight run flour (SRF) increased gradually with an increase in blending of green gram and barley with wheat. The highest SRF of 79.71% was obtained from the B3 blend. The coarse bran decreased from 15.95% for the control sample to 9.52% for B3 blending. The milling yield of pollard and fine bran showed a decreasing trend from control to B3 blending. In general, flour yield decreased for reduction passages from C1 to C3 and reduction passages produced higher flour compared to break rolls for all blends. The multigrain milling resulted in an increase in protein(113.1–13.35%) and dietary fiber (2.91–4.65%) content of flour, but sedimentation values (52–38 ml), which is the index of flour strength, decreased significantly. The distributions of mineral matters and fat show wide variation among the mill streams and concentrated in coarse and fine brans. The rheological properties of flour obtained showed increased water absorption (55.8–57.5%) and decreased dough stability(5.5–2.8 min), amylograph peak viscosity (388-335BU) and setback (265-224BU) with an increase of multigrain in blends.     

Proximate composition and selected functional properties of Detarium microcarpum

The proximate composition and functional properties of Detariummicrocarpum seed flour were evaluated. The dehulled seed flour contained3.5% moisture, 3.5% ash, 2.9% crude fiber, 15% crude fat, 37.1% crude protein and 39%carbohydrate. Functional properties showed bulk densityof 0.86 g/cm³ for dehulled and 0.92 g/cm³ for undehulled flour.Water absorption capacity was 4.9 g/g for dehulled and 5.1 g/g forundehulled seed flour; oil absorption capacity was 0.75 g/g for dehulled.The emulsion activity was 4.4% and 4.3% for dehulled and undehulled,respectively. The results obtained above showed that the Detariummicrocarpum seed flours have good nutritional quality and the functionalproperties confirmed their suitability for use in various food preparations.As a result, its present limited use should be expanded into additionalopportunities.     

Variation of Beta -Amylase Activity in Barley as Affected by Cultivar and Environment and its Relation to Protein Content and Grain Weight

The cultivar and environmental variation of beta -amylase activity was studied using two barley cultivars with contrasting growth properties. There was a significant difference in beta -amylase activity between the two cultivars used, 92-11 being significantly higher than Xiumai 3. A significant variation in beta -amylase activity was detected between grains at different positions within a spike. The two cultivars showed the same pattern, with top grains showing the highest and bottom ones the lowest activities. The relative difference within a spike varied between the cultivars, with 92-11 being larger than Xiumai 3. Both seeding rate and timing of N application dramatically affected the beta -amylase activity. With N application at the booting stage, beta -amylase activity increased, mainly due to the significantly increased beta-amylase activity in the topmost grains. The bottom grains showed a lower response to timing of N application. The variation in protein content and grain weight between cultivars and among the various treatments was also examined. The possible influence of these factors on beta -amylase activity are discussed.     

Deoxynivalenol in wheat milling fractions: A critical evaluation regarding ongoing and new legislation limits

New maximum limits (ML) for deoxynivalenol (DON) in wheat and its products were set in Brazil in 2017, and new changes are scheduled for 2019. The concentration of DON in wheat and milling fractions (bran, shorts, break flour, reduction flour) was evaluated in samples from commercial fields to discuss the effects of the new legislation. Cleaned wheat samples contaminated with DON had concentrations ranging from 308 to 2373 ng g⁻¹ (n = 29), and one sample had a concentration of 3426 ng g⁻¹. DON concentration obtained in bran and shorts were significantly higher than that of the flours. Compared to the initial concentration in cleaned wheat, DON relative concentrations were 73 and 35% higher in bran and shorts, respectively, and 67% lower in the straight run flour (break plus reduction flour). The bran and straight run flour contained DON concentrations that were 62.1 and 17.2% respectively higher than that of the ML set in Brazil in 2017; additionally, these values would reach 65.5 and 34.5%, respectively, according to the changes to be in effect in 2019. The present study demonstrates DON distribution in wheat milling fractions, thus, providing updated information for the management of DON contamination for the industry and policymakers.     

Construction of baker's yeast strains that secrete Aspergillus oryzae alpha-amylase and their use in bread making

The Aspergillus oryzae alpha-amylase cDNA has been cloned into a baker's yeast strain and put under the control of the SUC2 or ACT1 promoters. Integrative YIp and episomal YEp plasmids were constructed and transformants were selected because of their ability to express and export alpha-amylase. In all culture media tested (synthetic medium, flour slurry and bread dough), cells carrying the Aspergillus oryzae alpha-amylase gene under the control of the ACT1 promoter in multicopy plasmids (YEpACT-AMY) gave the highest level of the enzyme. Fermented dough prepared with YEpACT-AMY-containing cells gave a bread with a higher loaf volume, a lower density and a softer crumb than those made with cells containing YIpACT-AMY or with control yeast. The use of [YEpACT-AMY] transformants was also effective at retarding bread firming, increasing shelf-life and freshness of bread. These properties do not appear to be correlated with a large increase in the amount of low molecular weight dextrins.     

Prediction of Sensorial Properties (Color and Taste) of Amala,a Paste From Yam Chips Flour of West Africa,Through Flour Biochemical Properties

Color and taste are permanent features of amala, a traditional thick paste obtained from yam chips flour. To assess these attributes, 23 yam chips presenting various quality attributes were processed. The sensory attributes of their derived amala were determined and some biochemical characteristics of yam flours measured. A panel defined five main taste attributes for amala: sweetness, bitterness, acidity, fermented, and roasted tastes. Amala color was measured instrumentally and sensory scores were highly correlated with flour biochemical analyses; amala sweetness was positively correlated with glucose and fructose content of the flour, whereas amala acidity and fermented taste were linked to organic acids and lactic acid contents of flour, respectively. In addition, darkness, bitterness, and roasted tastes of amala could be tightly predicted by multiple regression analysis from phenolic compound and glucose–fructose contents. Phenolic content of yam flour plays thus a key role on sensorial quality of amala. However, polyphenol oxidase and peroxidase activities were almost null in yam flours and their specific role on yam flour phenolic content needs to be clarified.     

Maillard Reaction Evaluation by Furosine Determination During Infant Cereal Processing

The furosine content of infant cereals has been used to evaluate the thermal damage caused to those foods during their manufacture (toasting, amylolysis and drying steps). The mean furosine contents of raw and toasted flours were 13·7 and 13·8 mg/100 g of protein, respectively. The furosine content increased to 47·3 mg/100 g of protein after hydrolysis usingalpha-amylase. The amylolysis process raised the reducing sugar content from 0·5% for raw samples to 12·7%. The furosine content of infant cereals rose to average levels of 500 mg/100 g of protein after roller-drying. The infant cereals with the highest levels of reducing sugars, with or without soy flour, exhibited the highest furosine contents. Furosine is a useful indicator to evaluate the progress of the Maillard reaction during the amylolysis and roller-drying stages of infant cereals manufacture.