Mineral binding capacity of dephytinized insoluble fiber from extruded wheat,oat and rice brans

Insoluble fiber fractions from raw and extruded oat, rice and wheat brans were isolated and phytate removed. In vitro mineral binding studies were performed utilizing copper (Cu²⁺), calcium (Ca²⁺) and zinc (Zn²⁺) ions, which were added individually to enzymatically treated (Prosky et al., 1985), acid washed insoluble fiber residues from oat, rice and wheat brans. The enzymatic digestion step with alpha-amylase, protease and amyloglucosidase served to remove protein and starch from the samples. Mineral binding studies were performed on the insoluble fiber residue. Mineral content was determined by flame atomic absorption spectroscopy. Raw brans served as controls. A twin-screw extruder Model DNDG-62/20D, manufactured by Bühlerag (CH-9240, Uzwil, Switzerland) was utilized. The objectives of the study were to determine the total Cu²⁺, Ca²⁺ and Zn²⁺binding capacity of the dephytinized insoluble fiber from each bran; and to determine if extrusion screw speed affected the brans' insoluble fiber mineral binding capacity. Although dephytinized, the brans' insoluble fiber fraction bound Cu²⁺, Ca²⁺ and Zn²⁺ions. Oat bran bound more Cu²⁺, Ca²⁺ and Zn²⁺ than wheat bran, which bound more than rice bran. Extrusion processing did not affect the brans' insoluble fiber binding capacity to bind Cu²⁺. However, it increased the binding capacity of Ca²⁺ and Zn²⁺ of the insoluble fiber fraction from rice and oat brans.     

The effect of infrared stabilized rice bran substitution on physicochemical and sensory properties of pan breads: Part I

Infrared stabilized rice bran (SRB) substitution to white wheat, wheat bran and whole grain wheat breads at the levels of 2.5, 5.0 and 10.0% was evaluated in terms of proximate composition, crumb color, dietary fiber, texture and sensory attributes. An increasing tendency was observed in crude fat and ash content of the breads. Redness (+a*), yellowness (+b*) chroma and redness (a*/b*) values were increased gradually with the addition of SRB. Crumb color was found to be darker when 10% of SRB was added to the breads. SRB inclusion did not affect the content of soluble dietary fiber while it significantly increased the insoluble and total dietary fiber contents of the breads (p < 0.05). In general, whole grain wheat bread differed from the other bread types in terms of textural behavior. Based on the overall acceptability scores, white wheat and wheat bran breads were sensory accepted up to 10% of flour replacement with rice bran, while substitution levels higher than 2.5% negatively affected the sensory scores of whole grain wheat bread.     

Effect of extrusion treatment on enzymatic hydrolysis of wheat bran

Although, wheat bran is a good source of dietary fibre (DF), it has certain disadvantages due relatively lower levels of soluble DF. Therefore, in the current study, the effect of extrusion treatment on microstructure and enzymatic hydrolysis of wheat bran was investigated. Extrusion treatment increased fibre solubility at all process conditions and the screw speed was found to be the most effective parameter. Physicochemical properties of bran were affected from extrusion treatments. While the water-binding capacities of extruded brans were lower than that of non-extruded wheat bran, their water solubilities were higher. Enzymatic hydrolysis increased the soluble DF content of the bran samples as compared to those of respective samples at the beginning of incubation. The results showed that extrusion treatment can be used to disrupt the wheat bran microstructure and thus to increase the soluble fibre content. Enzymatic hydrolysis can also be used for increasing solubility further. The outcomes of this study can be utilized for improving the technological functionality of cereal fibres to develop high fibre ingredients for food applications.     

Effect of extrusion pretreatment on extraction,quality and antioxidant capacity of oat (Avena Sativa L.) bran oil

Extrusion is an alternative pretreatment for oil extraction from cereal resource. The objective of this study was to assess the feasibility of extrusion pretreatment of oat bran for oil extraction. The effects of extrusion conditions including feed moisture content, screw speed and die temperature on the extraction, quality and antioxidant capacity of oat bran oil were investigated. The results showed that the extraction yield of oat bran oil varied from 3.93% to 8.43% under different extrusion conditions. A feed moisture content of 25% had an important effect on the extraction of oil from oat bran. Extrusion pretreatment could increase oil extraction efficiency by increasing expansion index and porosity of oat bran extrudates. Extrusion processing had no positive or adverse effect on the fatty acid compositions, and acid, peroxide and iodine values. Meanwhile, extrusion processing did not affect the phytochemical components and antioxidant capacity of oat bran oil. But refining process could result in decrease of phytochemical components and antioxidant capacity of oat bran oil. These results indicated that extrusion is a feasible and potential pretreatment procedure for oil extraction from oat bran.     

Extrusion process improves the functionality of soluble dietary fiber in oat bran

Extrusion processing is a thermal process applied to food preparation. However, its effects on food ingredients are ambiguous. The aim of this study was to elucidate the effects of extrusion processing on soluble dietary fiber (SDF) in oat bran. The yield, composition, thermal properties, rheological behavior and functionality of SDF in extruded oat bran were compared with those of SDF in untreated oat bran. The results showed that SDF in extrude oat bran had higher yields (14.2%), mean particle diameter (1718.1 nm), peak temperature (T_p = 69.0 °C), solubility, swelling capacity, solvent retention capacity, foam ability, apparent viscosity and consistency coefficient, and lower flow behavior index than those of SDF in untreated oat bran. The extrusion process improves some properties of SDF from oat bran.     

Estimated Glycemic Index and Dietary Fiber Content of Cookies Elaborated with Extruded Wheat Bran

The increasing demand for high-fiber products has favored the design of numerous bakery products rich in fiber such as bread, cookies, and cakes. The objective of this study was to evaluate the dietary fiber and estimated glycemic index of cookies containing extruded wheat bran. Wheat bran was subjected to extrusion process under three temperature profiles: TP1;(60, 75, 85 and 100 °C), TP2;(60, 80, 100 and 120 °C), and TP3;(60, 80, 110 and 140 °C) and three moisture contents: (15, 23, and 31 %). Cookies were elaborated using extruded wheat bran (30 %), separated into two fractions (coarse and fine). The dietary fiber content of cookies elaborated with extruded wheat bran was higher than the controls; C0 (100 % wheat flour) and C1 (30 % of no extruded bran coarse fraction) and C2 (30 % of no extruded bran fine fraction). The higher values of dietary fiber were observed on cookies from treatments 5 (TP1, 31 % moisture content and coarse fraction) and 11 (TP2, 31 % moisture content and coarse fraction). The estimated glycemic index of cookies ranged from 68.54 to 80.16. The dietary fiber content of cookies was increased and the lowest glycemic index corresponded to the cookies elaborated with extruded wheat bran. Cookie made with the treatment 11 had a better dietary fiber content and lower estimated glycemic index.     

Functional suitability of commercially milled rice bran in India for use in different food products

The effect of blending of commercially available full fat and defatted rice brans in India from modern multistage rice mills with parboiling/stabilizing facilities in different food products in comparison to those obtained from laboratory milling of rice is reported. Bread volume and cookie spread decreased but muffin volume increased with the addition of different types of bran to wheat flour, however, the cookie spread factor was not affected by addition of full fat rice bran. The yields of the extrudate were increased by the blending of full fat rice bran but were decreased by the addition of defatted rice bran. Rice brans could be added to different food products to the extent of 5–10%. However, the full fat rice bran could not be used for production of extruded snack food.     

挤压膨化对绿茶茶渣中粗纤维影响

利用双螺杆挤压膨化机对绿茶茶渣进行挤压膨化加工,采用响应面设计方法建立物料含水量、喂料速度、螺杆转速以及套筒温度与绿茶茶渣中粗纤维含量之间的回归模型。结果表明,各参数对绿茶茶渣中粗纤维含量影响由大到小依次为：螺杆转速>套筒温度>喂料速度>物料含水量,获得低粗纤维含量的最佳挤压膨化参数为物料含水量70%,喂料速度90r/min,螺杆转速90r/min,套筒温度50℃。在此条件下,茶渣中粗纤维含量为15%,与膨化前原料相比,粗纤维含量下降了3%。     

Development of β-glucan enriched wheat bread using soluble oat fiber

Soluble oat fiber (SOF) containing 70% oat β-glucan was incorporated into wheat bread by replacing 10, 12, and 14% of flour in wheat bread formulas. At each level of SOF, bread was made at the farinograph water content defined by the amount of water required to develop a dough consistency of 500 Brabender Units in farinograph tests, and 10 and 20% extra water above the farinograph water content. At the farinograph water content, bread formulated at each level of SOF exhibited lower specific volume and porosity, darker color, higher hardness, and lower springiness and cohesiveness than the control white bread. These negative effects were effectively counteracted by optimizing the water content in bread formulas. For the three levels of bran addition, when the water content was increased by 20% above the farinograph water content, the obtained loaves exhibited similar loaf volume, microstructure, textural properties, and crumb porosity to the control white bread. A serving (28 g) of the developed bread contained respectively 0.95, 1.12, and 1.28 g of β-glucan, which substantially exceed the minimum standard for approved health claims.     

In vitro mineral binding capacity of five fiber sources and their insoluble components for copper and zinc

Five fiber-rich food sources, wheat bran (WB), rice bran (RB), oat fiber (OF), apple fiber (AF), and tomato fiber (TF) and their isolated insoluble fiber fractions were evaluated in vitro for their binding capacity for zinc (Zn) and copper (Cu). Endogenous Zn concentrations of the fibers varied from 11.0 µg/g for OF to 136.0 µg/g for WB, whereas Cu concentrations ranged from 1.0 µg/g for OF to 14.0 µg/g for WB. In all the fibers, total Cu bound was significantly higher than Zn. Total Cu bound ranged from 3687 µg/g for OF to 8019 µg/g and 8073 µg/g for WB and AF, whereas, bound Zn levels varied from 1213 µg/g for OF to 7121 µg/g and 7166 µg/g for WB and RB, respectively. Significantly more Zn and Cu were bound by the fiber fractions than the whole fibers, probably due to the exposure of more binding sites on the polymers during the fractionation process. Generally, the fiber components of all five fibers showed Cu and Zn binding capacities decreasing in the order; hemicellulose A>lignocellulose>lignin>cellulose. A strong correlation was seen between the combined effects of protein, hemicellulose, and lignin contents of the fibers versus total Zn binding capacity and a lesser correlation with Cu.Paper presented in part at the annual meeting of the Institute of Food Technologists, 25–29 June 1994, Atlanta, Georgia, USA.     

Stabilization of Tarom and Domesiah cultivars rice bran: Physicochemical,functional and nutritional properties

Extrusion is a multi-step thermal process which has been extensively utilized in food preparations. Effects of temperature, moisture content and speed screw on the stabilization of rice bran were optimized using response surface methodology. Furthermore, the effect of extrusion processing on the physicochemical, nutritional and functional properties of Tarom and Domesiah cultivars stabilized rice bran (SRB) were studied. The colour of rice bran was improved by extrusion processing, but the protein content was reduced, which can be related to the denaturation of protein. Extrusion had also a reduction significant effect on the phyitic acid and vitamin E in stabilized rice bran. However, the content of vitamins B₂, B₃, B₅ and folic acid were remained unchanged, but the dietary fibre was enhanced which has beneficial health effect. In comparison with raw rice bran, water holding capacity was enhanced, but the oil absorption capacity was reduced. Foaming capacity and foaming stability of SRB was more than that of untreated rice bran. Although, they were less than that of rice bran protein concentrate/isolate. As a result, extrusion process improves some functional and nutritional properties of rice bran which are valuable for industrial applications and have potential as food ingredient to improve consumer health.     

Effect of various heat treatments on rancidity and some bioactive compounds of rice bran

Rice bran contains natural phytochemicals but unstable against hydrolytic and oxidative rancidity. Various heat treatments, such as dry-heating (DH), freeze-drying followed by dry-heating (FDDH), microwave heating (MH), autoclaving (AC), and ethanol vapor (EV) treatment were applied to rice bran and their effects on the storage stability at room temperature were evaluated. The free fatty acid (FFA) content of untreated rice bran gradually increased from 2.14 to 19.81% during 24 weeks, whereas those of the treated rice brans were not or marginally changed. The FFA content in DH samples was greater than that in FDDH samples, indicating the positive effect of freeze-drying prior to DH. Among the treatments, autoclaving was most effective in retarding the FFA formation. The tocol content in the rice brans varied with the treatments, ranging from 181.4 mg/kg (EV) to 310.6 mg/kg (AC), whereas that in untreated rice bran was 216.3 mg/kg. Amounts of other bio-functional components such as phytosterols and policosanols were either unchanged or increased by the treatments. Policosanol level was increased by all the heat treatments, but not affected by EV treatment, indicating that the thermal treatments induced the release of free policosanols.     

Arabinoxylan and hydroxycinnamate content of wheat bran in relation to endoxylanase susceptibility

Hydroxycinnamate and protein contents and monosaccharide composition were determined for 11 industrial wheat (Triticum aestivum) brans and related to the susceptibility of their arabinoxylans (AX) to enzymatic degradation. There was significant variation in carbohydrate, A/X ratio, protein, hydroxycinnamic acid and diferulic acid (DiFA) content among the wheat brans. In addition, a strong correlation was found between AX and ferulic acid contents. Brans were extracted with water followed by a dry-thermal treatment to remove 90% starch and to inactivate endogenous enzymes and proteinaceous inhibitors. Treated brans were compared with respect to AX degradation by a family 11 xylanase. Digestion with xylanase had a strong impact on the chemical composition of the residual bran. The A/X ratio changed from 0.60 to 1.07. The solubilised AX had an A/X ratio of 0.32. The A/X ratio of enzyme-depleted bran was negatively correlated with the loss of AX. Total DiFA in destarched brans was negatively correlated with the amount of soluble AX. These relationships indicate that structural features of AX and the extent of its cross-linking in the cell walls of the bran tissues influence its susceptibility to xylanase treatment. Thus, the amount of enzyme-solubilised AX was not directly related to the content of AX in the destarched bran. However, brans differed in their susceptibility to xylanase attack.     

Dietary fiber and other functional components in two varieties of crude and extruded kiwicha (Amaranthus caudatus)

Two varieties (Centenario and Oscar Blanco) of Andean native grain, kiwicha (Amaranthus caudatus), were evaluated as sources of dietary fiber and of some bioactive compounds. The impact of low-cost extrusion on the content of these components was studied for technological applications. The content of total dietary fiber in Centenario was higher (16.4%) than in Oscar Blanco (13.8%). In both varieties, the content of total and insoluble dietary fiber decreased during the extrusion process. In Centenario, the content of soluble dietary fiber increased, from 2.5 to 3.1% during the extrusion process. The content of phytic acid in raw kiwicha was 0.3% for both varieties, and the content of total phenolic compounds was 98.7 and 112.9 mg GAE/100 g of sample, for Centenario and Oscar Blanco, respectively.     

Effect of proccesing on dietary fiber content of cereals and pulses

Total dietary fiber (TDF), insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) content of rice, wheat, sorghum, maize, ragi, bajra, whole grains of pigeonpea, chickpea, green gram and lentil as well as their dehusked split dhals were analyzed. Cereals except rice flours were made into chapati (unleavened bread), while rice and dhals were cooked in a pressure cooker. After the processing, IDF and SDF contents of these foods were also analyzed. Among the cereals, rice had the lowest TDF (4.1%) and wheat had the highest (12.5%). TDF content of whole pulses ranged from 15.8% in lentil to 28.3% in chickpea. IDF as % of TDF constituted 85 to 89% in whole pulses. Dehusking of pulses into dhals decreased the TDF and IDF contents significantly. Among the dhals, green gram dhal had the lowest (8.2%, 6.5%) and chickpea dhal (15.3%, 12.7%) had the highest TDF and IDF contents, respectively. Processing of cereals had no effect on their TDF and IDF contents, rith the exception of ragi, where a significant increase in TDF and IDF was observed. Cooking of dhals brought about a significant increase in their TDF and IDF contents.     

Antioxidant properties of wheat and rye bran extracts obtained by pressurized liquid extraction with different solvents

Rye and wheat brans are valuable sources of bioactive compounds, which could be used for the development and commercialization of high added value functional ingredients such as dietary antioxidants. The aim of this study was to evaluate antioxidant potential of rye and wheat bran using different polarity solvents. Cereal brans were ground to four different particle size fractions and extracted at 10.3 MPa pressure and 80 °C temperature by consecutive application of hexane, acetone and methanol:water (80:20%). The highest extract yield was obtained from rye bran using methanol-water; particle size in most cases had a significant effect. Antioxidant potential of extracts was assessed by ABTS^+•, DPPH^• scavenging, ORAC and total phenols content (TPC) assays. Extraction solvent had a major influence on TPC and antioxidant activity of the extracts. The most active extracts were obtained using methanol:water; rye bran extracts, in general, were stronger antioxidants than wheat bran extracts. For the majority of assays, reduction of particle size resulted in higher antioxidant activity values. However, ABTS^+• scavenging was found to decrease by decreasing particle size of rye bran used for extraction.     

Cereal and nut bars,nutritional quality and storage stability

Six snack-type bars were manufactured, to contain oat and wheat germ and two different walnut levels, agglutinated with natural sweeteners and fats. Two bars also contained toasted amaranth with brown sugar cover and wheat extrudate, while two others, contained puffed instead of toasted amaranth. Water activity (Aw) and moisture were determined in the manufactured products. Quality and sensory evaluation and proximate analysis were carried out on the bars containing highest levels of walnuts (18%). The caloric contribution of the bars was computed by Atwater methods. The nutritional quality of the bars was determined by means of the Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR), and the results were used to obtain relative PER and relative NPR. Samples of the latter bars were kept under accelerated storage for 15 days at 37 °C and analyzed every 5 days to determine their Aw, moisture, peroxide and sensory acceptability. The drying time for the cereal — and walnut — based bars was 45 min at 120 °C. All bars presented a good fiber supply and the CN₁ bar, containing only oat, wheat germ and walnut, had the greatest protein content. In the sensory evaluation, the walnut level with the greatest preference was 18%. PER and NPR values of the bars did not differ significantly showing values approximately 86% that of the casein value. During storage, the moisture and Aw decreased in all the bars. Peroxides remained within the acceptable ranges; acceptability based on sensory evaluation remained best in the bar with toasted amaranth. Walnuts can successfully be used in the manufacture of snack bars as these offer good nutritional and sensory quality and remain stable in storage.     

Preparation, physicochemical and texture properties of texturized rice produce by Improved Extrusion Cooking Technology

Using broken rice and rice bran as raw material, texturized rice (TR) was prepared by Improved Extrusion Cooking Technology (IECT) in which gelatinization is formed by means of low temperature and high pressure. The expansion of extrudate was hardly changed so that TR showed similar texture properties and shape with polished rices. The effect of rice bran addition (0% and 4%) and IECT conditions, including feed moisture content (26.6-33.4%), screw speed (20.1-32.6 rpm) and shearing compression metering zone temperature (SCMT, 69.8-120.2 °C) on the physicochemical, texture and nutritional characteristics of TR, were investigated by response surface methodology using Central Composite Design. When the bran addition was 4%, feed moisture content was 30%, screw speed was 26.6 rpm, SCMT was 95 °C, prepared TR contained 16.61 ± 0.02% of total dietary fiber, 9.40 ± 0.04% of protein, 3.68 ± 0.03% of fat, 2.42 ± 0.02 μg/g of thiamin, 0.52 ± 0.01 μg/g of riboflavin and 16.07 ± 0.12 mg/100 g of γ-oryzanol (dry matter content). The content increase of TDF for TR was 15.81% and the content increases of nutrients for thiamin, riboflavin, and γ-oryzanol were 1.39 μg/g, 0.24 μg/g, and 8.99 mg/g dry matter content, respectively, compared with those of polished rice.     

Phenolic content,anthocyanins and antiradical capacity of diverse purple bran rice genotypes as compared to other bran colors

Anthocyanins are flavonoids, a subgroup of phenolic compounds in bran of purple rice that have shown health benefits in animal studies and human clinical trials. We studied the genetic diversity of the concentrations of total phenolics, flavonoids and anthocyanins, and, antiradical capacity in diverse purple rice brans. More than 13-, 12-, 25- and 8-fold variations were found for these respective traits. Cyanidin-3-glucoside and peonidin-3-glucoside were the major anthocyanins identified. The color parameter b* of whole grain rice was correlated with anthocyanins and can be used as a non-destructive quick screening tool. Purple brans that accumulated both anthocyanins and proanthocyanidins had the highest total phenolics, total flavonoids, and oxygen radical absorbance capacity among all color brans. Purple brans had the widest genotypic diversity of these chemical traits, followed by red, brown, light brown, and white. In terms of antioxidant properties of total flavonoid compounds in the sample extracts, purple and red brans had similar reducing capacity per unit of total flavonoids; while purple bran had higher oxygen radical absorbance capacity per unit of total flavonoids. In conclusion, new rice cultivars with colored bran having specific amounts and types of phenolic compounds can be developed using traditional breeding.     

Effects of selected extrusion parameters on physicochemical properties and in vitro starch digestibility and β-glucan extractability of whole grain oats

Whole grain oat flour was extruded under different moisture contents (15%, 18%, 21%), barrel temperatures (100 °C, 130 °C), and screw speeds (160 rpm, 300 rpm, 450 rpm), and selected physicochemical properties, in vitro starch digestibility, and β-glucan extractability of the extrudates were analyzed. An increase in screw speed resulted in an increase in radial expansion index, water absorption index, and water solubility index. Screw speed significantly affected slowly and rapidly digestible starch. Moderate screw speed (300 rpm) led to higher slowly digestible starch with an accompanying decrease in rapidly digestible starch. Low moisture conditions (15%) resulted in the highest resistant starch and water-extractable β-glucan. Under the conditions used in this study, extrusion did not result in changes in water-extractable β-glucan molecular weight. Thus, extrusion might be beneficial in improving functionality and consumer acceptability by affecting physicochemical properties, in vitro starch digestibility, and β-glucan extractability of oat extrudates.