Effect of wheat bran on the mechanical properties of extruded starchy foams

Incorporation of wheat bran has a significant effect on the texture of extruded starchy products. This can be explained by changes in the mechanical parameters of the products. The stress at rupture and elastic modulus of wheat flour-based solid foams, obtained at different extrusion conditions and bran concentration, were measured using a three-point bending test. Both parameters were positively correlated with the foam relative density according to the Gibson–Ashby model. At same relative densities and bran concentration, finer structures with higher density of small cells led to a higher mechanical strength of the foams. The stress at rupture of the unexpanded material was decreased when increasing the bran concentration. Nevertheless, expanded foams with added bran at an intermediate level showed increased mechanical strength. This was attributed to the finer cellular structures obtained. The effect of increasing the bran to a higher concentration on the mechanical properties was depending on the cell wall thickness and bran particle dimensions. At high relative density, the strength of the foams was further increased due to the even finer structures obtained. At low relative density, even though finer structures were also obtained, the stress at rupture of the foams was decreased. This may be explained by the lower cell wall thicknesses and low adhesion properties between bran and starch favoring rupture of the cell walls.     

Expansion mechanism of extruded foams supplemented with wheat bran

Addition of bran reduces the expansion of extruded starchy foams. This may be attributed to changes in parameters driving expansion. Wheat flour was supplemented with wheat bran to achieve two levels of fibers (12.6% and 22.4%) and extruded under different conditions of barrel temperature (120 or 180 °C), water content in the feed (18% or 22%) or screw speed (400 or 800 rpm). Increasing the bran concentration decreased sectional and volumetric expansions and increased longitudinal expansion. Finer cellular structures consisting of an increased number of small cells with more spherical shapes were generated. This may be linked to an increased nucleation at the die. The reduction in volumetric expansion was associated with an increase in shear viscosity only at the highest bran concentration. At same extrusion conditions the glass transition temperature of starch was reduced by down to 15 °C by supplementation with bran. This may induce a decrease in the viscosity of the starch phase and counteract the matrix viscosity increase linked to the properties of bran. A higher surface porosity was observed in the bran containing recipe due to earlier burst of the bubbles during growth.     

麦麸膳食纤维对小麦粉糊化及凝胶质构特性的影响

为研究膳食纤维对淀粉糊化及凝胶质构的影响,本实验以2种不同筋力小麦粉为原料,添加麦麸膳食纤维,5个添加量处理,分析其小麦粉糊化特性、凝胶质构及其微观结构。结果表明:随麦麸膳食纤维添加量的增加,峰值粘度、低谷粘度、稀懈值、最终粘度和回生值等糊化特征参数均呈显著下降趋势,糊化时间和糊化温度的变化不明显,且没有规律性;添加膳食纤维显著降低了糊化凝胶的硬度、粘附性和咀嚼度(p<0.05),而弹性、内聚性和胶粘性未见显著变化;膳食纤维对2种不同筋力小麦粉糊化和凝胶质构特性的影响趋势基本一致;膳食纤维改变了面团和糊化凝胶体系的微观结构,可增加面团的紧致性,但会降低凝胶结构的致密性和均匀性。     

Effect of extruded wheat bran on dough rheology and bread quality

Bran extrusion is mainly under study and works should be performed to know the effect on dough and bread. This study was designed to investigate the effect of bran extrusion (addition of 2.5 g/100 g to 20 g/100g bran) on the rheological characteristics of bread dough, behaviour during fermentation, and bread quality. Extruded bran increased dough development time and tenacity to a greater extent than non-extruded bran, and minimized the loss of stability if over-mixing occurred. Extruded bran, due to its greater gas production, also reduced loss of dough height during fermentation to a greater extent than untreated bran. However, breads with extruded bran showed a higher volume and lower initial firmness than breads with normal bran if improver was added. However, no differences were found in the organoleptic evaluation. Bran extrusion therefore modified dough rheology but did not negatively affect bread quality. It could even improve the quality of breads with bran when improvers are added.     

The effect of rice bran on physicochemical,textural and glycaemic properties of ready-to-eat extruded corn snacks

In this work, corn extruded snack products were enriched with rice bran (RB) at 10% and 15%. A co-rotating twin-screw extruder was used with a feed moisture content of 16 g 100 g⁻¹, a screw speed of 240 r.p.m. and four heating sections of the barrel (100, 140, 150 and 150 °C). The impact of RB inclusion on nutritional profile, starch digestion, physicochemical and textural properties of snack products was evaluated. RB-enriched extrudates showed a lower specific volume and hardness and higher crispness than control. RB at 15% gave a water-holding capacity lower than control. Rheology of extrudate dispersions indicated an increase in elastic interactions and solid-like behaviour with RB supplementation. Differences in rheological properties resulted in attenuation of predictive glycaemic response for RB-enriched snacks.     

细度对挤压麦麸理化特性及其全麦粉加工品质特性的影响

以挤压麦麸(粗麸、细麸、胚芽、次粉混合料)为原料,研究筛分细度(粒径44.15~198.48μm)对挤压麦麸的理化特性及其全麦粉加工品质特性的影响。结果表明:随着筛分目数的增加,挤压麦麸的粒径范围分布变窄;筛分细度对其戊聚糖、阿魏酸含量的影响较大;对其持水性、溶胀性的影响较小,对全麦粉的糊化特性、粉质特性的影响较小;挤压处理麦麸混合料可获得较均一的麦麸产品。     

超微粉碎对小麦麸皮功能特性的影响研究

通过3种麸皮在黄酮功能成分溶出、阳离子交换能力、有害离子的清除及抗氧化活性方面的对比分析,研究了超微粉碎技术对麸皮功能特性方面的影响。采用体外试验方法,与大、中麸皮相比,超微麸皮总黄酮得率、对NO_2~–清除率、对Pb~(2+)、Hg~(2+)、Cd~(2+)金属混合液的吸附能力均有不同程度的提高;对胆酸钠的吸附力略有下降;对阳离子交换能力略有增加。3种粒径的麸皮黄酮提取液对1,1-二苯基-2-三硝基苯肼自由基(DPPH·)、羟自由基(·OH)和超氧阴离子自由基(O_2~–·)均具有较好的清除能力。超微麸皮的粒径小、粉体均匀性好,将其应用于功能性食品开发具有重要意义。     

Effect of thermal processing on antioxidant properties of purple wheat bran

Antioxidant activity of purple wheat bran, heat-treated purple wheat bran, and purple wheat bran muffins was evaluated to determine the impact of thermal processing on potential health benefits. The purple wheat bran and muffin samples were analyzed for total phenolic content, anthocyanin content and free radical scavenging activity using peroxyl (oxygen radical absorbance capacity assay) and 2,2-diphenyl-1-picrylhydrazyl (DPPH assay) radicals. Total phenolic content and oxygen radical absorbance capacity (ORAC) values of sample extracts were significantly affected by various extracting solvents. The conditions selected for heat treatment did not markedly change antioxidant activity of purple wheat bran. However, there was a significant reduction in total phenolic contents, ORAC values and total anthocyanins during processing of purple wheat bran- or heat-treated purple wheat bran-enriched muffins. On the contrary, muffin extracts still remained excellent in DPPH radical scavenging activity.     

干燥方式对挤压麸皮理化性质和抗氧化活性的影响

目的：确定挤压小麦麸皮的最佳干燥方式。方法：探究3种干燥方式(流化床干燥、微波干燥、热风干燥)对挤压麸皮基本成分、持水力、水溶性、膨胀力、持油力、色值、抗氧化性、总酚和总黄酮含量等的影响;以抗氧化性、总酚和总黄酮含量为指标,确定挤压麸皮最佳干燥方式。结果：3种干燥方式对挤压麸皮的粗蛋白、粗脂肪、灰分和总膳食纤维含量无显著性影响;与流化床干燥相比,微波干燥和热风干燥能提高淀粉和粗纤维含量;干燥对挤压麸皮水溶性的影响是：热风干燥＞流化床干燥＞微波干燥;与微波干燥和热风干燥相比,流化床干燥能提高挤压麸皮的膨胀力和持油力;与流化床干燥和热风干燥相比,微波干燥能提高挤压麸皮的持水力、抗氧化性、总酚和总黄酮含量,降低亮度和白度。结论：挤压麸皮最佳干燥方式为微波干燥。     

Elastic properties of extruded starchy melts containing wheat bran using on-line rheology and dynamic mechanical thermal analysis

Addition of wheat bran reduces the expansion volumes of extruded cereals. This may be explained by the influence wheat bran has on the elastic properties of the melt. The elastic properties of extruded refined wheat flour supplemented with wheat bran were investigated using a complementary on-line and an off-line rheological technique. The Bagley pressure (end pressure), reflecting extensional properties of the melt, was measured on-line using the orifice die method (dies with different lengths). The storage modulus of the extruded samples was measured using dynamic mechanical thermal analysis (DMTA). Increasing the bran concentration to an intermediate level significantly increased the Bagley pressure likely due to a reduced mobility of starch molecules. Further increasing the bran concentration significantly decreased the Bagley pressure. This might be caused by physical rupture of the melt at the die exit due to the low adhesion properties between starch and bran particles. This change in Bagley pressure indicates that the elastic properties of the composite melt may be reduced by bran particles. The storage modulus measured by DMTA was decreased when increasing the bran concentration, further supporting a potential decrease of the elastic properties of the melt with bran.     

小麦麸皮粉体的电学性质初探

研究了经过粉碎、筛分后的麦麸粉体的电学特性。小麦麸皮经振动研磨20 min后,颗粒最为分散,将此时获得的麦麸颗粒进行高频振动筛分,获取3种不同粒径、结构和组成的麦麸粉体。通过电晕给电和摩擦起电两种方式使得麦麸颗粒带电,结果表明:在两种给电方式下,粒径在45～75μm的麦麸颗粒带电效果均最好。在电晕给电方式中,当电压达到46 kV时,3种麦麸颗粒所带电荷出现明显差异。对于摩擦起电,聚四氟乙烯对于3种麦麸颗粒的摩擦起电效果均最好,可以作为摩擦起电的管道材料。经过初步的探索研究,基于不同的荷质比,麦麸粉体可以通过高压静电场分离得以分离。     

麸皮的添加比例对全麦粉流变学特性的影响

研究添加不同比例麸皮对小麦粉流变学特性的影响。以国审强筋品种晋麦92号为原料,进行磨粉制得小麦粉,添加麸皮的比例分别为5%、10%、15%、20%、25%和30%,纯小麦粉和纯麸皮分别作为阴性对照和阳性对照,采用电子粉质仪、电子拉伸仪和全自动吹泡仪等依照GB/T14614—2006、GB/T14615—2006和GB/T14614.4—2005对其进行流变学特性测定。结果表明,随着添加麸皮的比例由30%降低到5%,沉降值、粉质稳定时间和拉伸能量逐渐升高,高吹泡最大压力和Dmax逐渐降低,吹泡曲线长度、吹泡充气指数和吹泡形变能量均呈先降低后升高趋势,拉伸比例和吹泡曲线比值则是先升高后降低。麸皮添加比例为5%～25%的全麦粉均达到中筋乃至中强筋水平,可用于面条或馒头制作。     

酶解条件对麦麸低聚木糖含量及其性质的影响

采用酶法水解麦麸水不溶性阿拉伯木聚糖制备低聚木糖,研究酶解温度、酶解时间和加酶量对低聚木糖含量及其糖组成、平均聚合度以及益生元活性的影响。结果表明:随着酶解时间由1h延长至2 h、酶解温度由40℃增加至50℃和加酶量由0.125 g/L增加至1 g/L时,低聚木糖含量增加,平均聚合度减小,木二糖、木三糖和木四糖的相对含量比值减小;不同酶解条件下得到的低聚木糖培养青春双歧杆菌的菌体浓度含量均有不同程度的增加;青春双歧杆菌代谢不同酶解条件下得到的低聚木糖发酵液中代谢产物均含乳酸、乙酸和丙酸,乙酸含量最高,其产酸量变化趋势与菌体浓度和低聚木糖含量相一致,与低聚木糖平均聚合度相反。当酶解温度50℃,酶解时间2 h和加酶量1 g/L时,低聚木糖含量达到最大为101 mg/g,平均聚合度降至最小3.23,木二糖、木三糖和木四糖的相对含量比值也最小,菌体浓度增值倍数达到最大为5.65倍。     

Effect of ultrafine grinding on hydration and antioxidant properties of wheat bran dietary fiber

Wheat bran dietary fiber (DF) powders was prepared by ultrafine grinding, whose effects were investigated on the composition, hydration and antioxidant properties of the wheat bran DF products. The results showed that ultrafine grinding could effectively pulverize the fiber particles to submicron scale. As particle size decrease, the hydration properties (water holding capacity, water retention capacity and swelling capacity) of wheat bran DF were significantly (p < 0.05) decreased and a redistribution of fiber components from insoluble to soluble fractions was observed. The antioxidant activities of wheat bran and DF before and after grinding were in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, ferrous ion-chelating activity, reducing power and total phenolic content (TPC). Compared with DF before and after grinding, micronized insoluble DF showed increased chelating activity, reducing power and TPC yet decreased DPPH˙ radical scavenging activity. Positive correlations were detected between chelating activity, reducing power and TPC.     

发酵麦麸对面包面团生化特征及烘焙学特性的影响

采用马克斯克鲁维酵母(Marx Kluyveromyces)发酵麦麸,通过生化分析、流变特性测试及微观结构观察(Scanning electron microscope,SEM)等多种分析手段,研究其对面包面团生物化学特征和烘焙学特性的影响。结果表明:马克斯克鲁维酵母发酵麦麸中富含多种天然酶,主要包括纤维素酶、木聚糖酶和阿魏酸酯酶;水解酶在面包制作过程中持续作用,促进木聚糖溶解和酚类化合物释放,赋予面包较高的营养价值;与仅添加木聚糖酶的麦麸面包面团相比,马克斯克鲁维酵母发酵麦麸面包面团具有更好的持气性及连续的面筋网络结构,面包全质构特性和比容显著提升。研究结果显示,马克斯克鲁维酵母发酵麦麸可以作为一种天然面包功能配料。     

Nutritional quality of extruded snacks developed from composite of rice brokens and wheat bran

Wheat bran was mixed with broken rice to develop nutritionally balanced extruded crisp snacks for human consumption. The inclusion of wheat bran enhanced the content of nutrients such as calcium, phosphorus, iron, copper, thiamine, riboflavin, lysine and also of antinutrients like phytic phosphorus and trypsin inhibitor. Extrusion cooking decreased the content of thiamine, riboflavin and lysine. The degradation of phytic phosphorus and inactivation of trypsin inhibitor had an improving effect on the nutritional quality of the extruded snacks as reflected by higher in vitro digestibility of its proteins.     

麦麸成分对曲霉多糖产量的影响研究

研究了麦麸及其成分对菌体生长和多糖累积的影响。结果表明,麦麸蛋白和可溶性纤维对曲霉菌体增殖和多糖累积无积极的作用,而麦麸阿魏酸对菌体增殖虽无明显作用但却可显著提高多糖产量。当以葡萄糖发酵培养基培养菌体36h时添加2%的麦麸阿魏酸,使得曲霉多糖产量提高至7.89g/L,比葡萄糖培养基提高了37.9%。