Nutrient addition to corn masa flour: effect on corn flour stability, nutrient loss, and acceptability of fortified corn tortillas

BACKGROUND: Iron, zinc, and vitamin B complex are among the most prevalent nutritional deficiencies in Mexico, with iron deficiency being the leading cause of anemia. Mexico has the highest per capita consumption of corn in the world, consumed mainly as tortilla. Thus, corn flour for making tortillas has been suggested as an effective strategy to overcome malnutrition in developing countries such as Mexico where corn is a staple food. The stability of micronutrients added to food is an important factor for the success of fortification programs. OBJECTIVE: The aim of this study was to evaluate the stability of corn flour fortified with micronutrients, and to measure the effect of micronutrient fortification on the sensory quality and stability of the fortificants in fresh and stored tortilla. METHODS: A commercially homogenized nonfortified corn flour (NCFC) produced from degermed white corn was fortified with a premix containing iron, zinc, thiamin, and riboflavin. Changes in thiamin, riboflavin, iron, and zinc content in fortified corn flour (FCF) and nonfortified corn flour (NFCF) during storage were investigated. Vitamin B1 and B2 content was determined by fluorescence spectroscopy while iron and zinc content was analyzed by atomic absorption. RESULTS: Thiamin content in FCF and NFCF showed a significant (p < .05) decrease (24% and 37%, respectively) after 90 days of storage. Riboflavin losses of 18% and 22% were observed for FCF and NFCF, respectively. FCF retained over 90% of iron, while zinc content remained constant. Losses of thiamin (27 to 39%) and riboflavin (37%) were produced during the process to convert corn masa flour into tortillas. CONCLUSIONS: Storage time slightly affected the stability of riboflavin and thiamin in FCF while the cooking process produced considerable losses of both vitamins. Tortillas made from FCF were well accepted by Mexican adults. We conclude that the addition of vitamins and minerals in the forms and quantities used in this study do not modify the shelf-life of corn flour, and neither do they cause sensorial changes in tortillas made from FCF.     

Effect of frozen storage on deep-fat fried breaded onion rings

Freshly fried and frozen breaded onion rings with and without in-pack dessicant were compared with freshly fried similar rings for moisture content of onion and for moisture content, colour and shear force/toughness of the coating. Moisture migration from onion to coating during freezing/storage/thawing increased significantly without dessicant, but did not remain in the coating with dessicant. Significant moisture loss/juiciness occurred from the onion in both frozen packs, and neither procedure was satisfactory.     

全麦粉对油炸方便面品质的影响

以全麦粉代替部分普通精制面粉,研究全麦粉对油炸方便面原料的糊化特性以及产品质构、颜色、脂肪含量及复水时间的影响。结果表明,全麦粉对方便面原料的峰值粘度、谷值粘度及最终粘度起显著负相关(P0.05)作用。方便面质构方面,随着全麦粉取代量的增加,硬度降低,咀嚼性及回弹性下降,粘度增加;色泽变暗,红度加深;复水时间延长,当全麦粉替代量从60%提高到80%时,复水时间从390s增加到600s。全麦粉替代量低于80%时,方便面的表面脂肪含量(SUOC)、结构脂肪含量(SOC)及总脂肪含量(TOC)均与全麦粉替代量呈正相关(分别从2.31%,17.55%,19.86%上升到3.01%,24.03%,27.03%),当替代量超过80%后,SUOC值、SOC值及TOC值基本不变(分别为3%,19%,27%左右)。依据本试验结果,建议全麦方便面中全麦粉取代量为60%。     

挤压膨化对玉米粉发酵的影响

以玉米碴为原料,植物乳杆菌P8菌粉为发酵菌,考察了挤压膨化对玉米粉发酵的pH、总酸度、挥发酸的影响,并测定了玉米粉、膨化玉米粉的比表面积和孔径分布。结果表明,挤压膨化使玉米粉比表面积增加178%,孔径从2.89~17.93nm增大到3.42~20.47nm;与玉米粉相比,膨化玉米粉发酵至pH3.80时间约缩短12h、发酵至酸度13.5g/kg时间缩短6h;膨化增大了植物乳杆菌的作用面积,加快了发酵速度。      

大米粉对油炸挂糊食品外壳食用品质的影响

为使油炸食品获得更好的食用品质,对组成糊的米粉原料进行了筛选。采用深层油炸模型,研究了泰国香米、东北长粒香米、稻花香米和长糯米等4种米粉对挂糊油炸食品外壳的吸油率、表观色度、剪切力及感官品质的影响。结果表明,当米粉添加量为16%时,稻花香米粉外壳吸油率最低为11.26%;当添加量为32%时,泰国香米粉的外壳吸油率最低为10.71%。当米粉添加量为16%时,泰国香米粉外壳L值最大为61.31;糯米粉外壳L值始终呈现上升趋势。在硬度方面,当米粉添加量为16%时,稻花香米粉外壳剪切力最大为47.75N;当米粉添加量40%时,糯米粉外壳剪切力仅为19.21N。综合考虑,在4种米粉中,稻花香米粉是挂糊油炸产品优先选用的米粉品种。      

Studies on the quality of fried snacks based on blends of wheat flour and soya flour

Wheat flour and defatted soya flour blended in the ratio of 65:20, 60:25, 55:30 and 45:40 were studied in respect of dough characteristics and quality of fried savoury and sweet snacks prepared from them. Farinograph characteristics of flour blends showed that as the proportion of soya flour increased there was a slight increase in water absorption and decrease in dough stability. In fried savoury snacks the protein content increased gradually from 20.75 to 27.50%. When the proportion of soya flour was raised from 20 to 40% in the blend, the corresponding rise in protein content in fried sweet snack was from 15.75 to 21.75%. The products were subjected to sensory evaluation by adopting preference ranking test and analyzing the data using Friedman's test and Wilcoxon Mann–Whitney U Test. No significant difference (P⩽0.05) was found among the samples for overall acceptability. In sweet snack, irrespective of levels of soya flour significant difference was not found (P⩽0.05) for all the attributes namely color and appearance, texture, aroma and taste. Color values expressed as L¹, a¹, b¹ showed that development of color during deep fat frying of snacks was not markedly affected by the levels of soya flour. Hardness of fried snacks was measured as force required for 50% compression. Duncan's Multiple Range Test (DMRT) of the texture values showed a significant increase in hardness (P⩽0.05) with the level of soya flour.     

Effect of batter formulation on lipid uptake during frying and lipid fraction of frozen battered squid

The present paper studies the influence that batter ingredients (wheat flour, corn flour, salt and leavening agent) have on fat content and oxidative degradation of the lipid fraction of deep-fried frozen battered squid. The use of a leavening agent significantly increases the fat content during frying; the generation of gas cells where oil easily lodges is the most important event observed by scanning electron microscopy when this additive is used in the formulation. The addition of salt in the formulation also increases fat content, but replacement of wheat flour by corn flour decreases significantly the oil content of the battered squids. The acidity index values indicate a relatively low degree of hydrolysis for all the batters studied. The batter formulation influences the degree of oxidation of the lipid fraction of the deep-fried products; the battered product with leavening in its formulation shows a lesser oxidation (P<0.05), which might be connected with the high absorption of oil during deep fat frying.     

Effect of calcium content in the corn flour on RVA profiles

Corn flour was produced using the traditional nixtamalization process and different steeping times of 0, 1, 5, 6, 10, 13, and 24 h. The flour particle size distribution was then evaluated in terms of the particles retained by using a 40 US mesh screen. The lime content, the Rapid Visco Analyzer (RVA) profiles, maximum peak viscosity, breakdown and final viscosity (V) were measured as a function of the steeping time. It was found that the initial rate of increase in viscosity (dV/dt), maximum peak viscosity, breakdown and final viscosity of fractions depended on the amount of calcium incorporated in the corn kernels during the steeping time (T_s) of the nixtamalization process. The particles retained using a 40 mesh that were steeped for 0-5 h, do not have the characteristic points of an RVA profile, i.e., maximum peak viscosity and breakdown. However, the particles retained using a 40 mesh and steeped for 6-24 h developed peak viscosity, breakdown and final viscosity. The corn flours that are recommended for making tortillas are precisely the flours whose particle size distributions develop these three characteristic points in the RVA profile. Differences in RVA measurements of the size fractions can be explained on the basis of the calcium content of the course fractions of corn flours. It was concluded that RVA characteristics may be changed by the calcium content in the starch polymer structures created during the nixtamalization process. Consequently, the increased calcium content in starch particles should be reflected in RVA measurements as an increase in the peak viscosity, in the gelatinization rate and in the development of a noticeable breakdown.     

生物酶对玉米面粉糊化性质的影响

采用蛋白酶、脱支酶、乳酸菌胞外酶处理玉米面粉,用RVA测其糊化曲线,筛选出对糊化性质有所改善的生物酶及其用量,并分析其改良机理。结果表明:蛋白酶可明显改善原面粉的糊化性质,其回生值和破损值都减小;脱支酶的作用效果不明显;乳酸菌胞外酶在一定浓度下也可以改善面粉的糊化性质。     

Effects of frying parameters on the colour development of fried potatoes

The effects of frying time and temperature on the colour development of potatoes during frying was studied. Potato disks 0.025 m in diameter and 0.005 m thick were used. Sunflower oil was used as a frying medium at temperatures 150 °C, 160°C, 170°C and 180°C. Colour parameters of Hunter L and b values followed first-order reaction kinetics during frying. The temperature dependence of the rate constants for Hunter L and b values showed good agreement with Arrhenius relation, the activation energies, Ea, being equal to 22.67 kcal/mol and 17.13 kcal/mol, respectively. Hunter a value increased as frying time and/or temperature increased. A multiple regression equation was developed for total colour change as a function of time and temperature. The increase in time and temperature increased total colour change. Received: 22 October 1999     

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

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

粒度对玉米粉及玉米面条影响的研究进展

粒度是衡量玉米粉品质的一个重要的物理性参数,极大的影响着玉米粉及玉米面条的品质。随着玉米粉筛分粒度的减小,总淀粉、损伤淀粉含量增加,直链淀粉含量降低;同时,淀粉结晶度下降,水合特性增强,糊化温度降低。这些性质的变化一定程度上影响着玉米面条的品质特性。本文首先对影响玉米粉粒度的因素进行了概述,重点阐述了粒度对玉米粉关键组分与理化性质的影响,最后综述了粒度对玉米面条品质的影响,旨在为相关研究人员与玉米面条行业提供一些参考。     

玉米淀粉对油炸鸡肉块保水性和感官品质的影响

研究玉米淀粉添加量对油炸鸡肉块品质和油炸得率的影响,并分析了油炸鸡肉块色差、剪切力、感官品质、水分分布状态和水分迁移特性。与未添加玉米淀粉相比,添加玉米淀粉显著(P0.05)提高油炸鸡肉块的得率,且随着玉米淀粉的增加而增大。添加玉米淀粉提高油炸鸡肉块的L*、a*和b*值,降低剪切力。添加量为20g/kg和30 g/kg时,油炸鸡肉块的L*、a*和b*值最大,剪切力最小。低场核磁共振结果表明,提高玉米淀粉的添加量,T22起始弛豫时间延长(P0.05),峰比例增加,自由水含量增加,油炸鸡肉块的保水性提高。添加玉米淀粉提高油炸鸡肉块色泽、嫩度、多汁性、风味和整体接受性评价分值,添加量为20 g/kg和30 g/kg时油炸鸡肉块的感官评价分值最高。综合油炸得率、色差、剪切力和感官评价分析,玉米淀粉添加量在30 g时油炸鸡肉块的品质最佳。     

Effect of taro (Colocasia esculenta) flour addition on the functional and alveographic properties of wheat flour and dough

BACKGROUND: Taro is a plant widely produced in tropical areas for its underground corms. Taro corms are highly perishable owing to their high moisture content. In order to limit post‐harvest losses and improve the production and consumption, production and utilization of taro flour have been envisaged. In connection with this, the incorporation of taro flour into wheat‐based products has been reported to increase their keeping quality. Before consideration is given to taro flour as a substitute for wheat in bread manufacture, it is necessary to characterize the functionality of the composite flour and dough. The present study investigated the physicochemical and alveographic properties of wheat–taro composite flour. RESULTS: Three varieties of taro flour (WCN, RIN and KWN) were incorporated into wheat flour in proportions of 10%, 20% and 30% (w/w) and the water absorption capacity (WAC), retrogradation index (RI), foam capacity (FC) and other functional properties were measured. In addition, characteristics of dough rupture pressure (P), extensibility (L), elasticity index (Ie) and strength (W) of flour made from the different composites were measured using an alveograph. The results showed that WAC significantly increased from 132% (wheat flour) to 156% (30% composite flour), while RI significantly decreased from 38% to a mean value of 22%. Principal component analysis revealed that WAC and P formed a group of variables negatively correlated with a second group made of RI, FC, W, Ie and L. CONCLUSION: Incorporating taro flour up to a level of 10% had no significant effect on the functional and alveographic properties of the flours. This suggested that in order to guarantee the quality of bread made from wheat–taro composite the level of taro addition should not exceed 10%. Copyright © 2007 Society of Chemical Industry     

Effect of soybean addition on the rheological properties and breadmaking quality of wheat flour

The effects of enzyme‐active full‐fat (EAFFSF), heat‐treated full‐fat (HTFFSF) and enzyme‐active defatted (EADSF) soy flours and commercial soy protein isolates (SPIs) on mixing properties and extensibility of dough, gluten formation, gas production and retention properties of dough and bread quality were studied. The soy products utilised in this study presented values of urease activity, nitrogen solubility index (NSI) and enthalpies of protein denaturation according to their previous heat processing. Soy products interfered in gluten formation, weakened dough strength and decreased dough gas retention capacity. Bread quality was negatively affected by soy product addition. The negative effects were exacerbated by an increase in soy/wheat ratio. Soybean protein state was identified as an important factor in determining dough and bread properties. Copyright © 2005 Society of Chemical Industry     

玉米粉配比对玉米-小麦混合粉面条品质的影响

采用不同的配比将玉米粉与小麦粉混配,用混合粉制作面条,通过测定玉米-小麦混合粉鲜湿面条的蒸煮、质构及感官品质,研究玉米粉添加量对混合粉鲜湿面条品质的影响。结果表明:随着玉米粉配比的增大,面条的蒸煮损失率呈上升趋势,硬度、咀嚼性和剪切力则逐渐减小,而总评分呈先增加后降低的趋势。玉米粉、小麦粉质量比为25∶75及以下时,面条煮后没有断条现象,当二者质量比达30∶70时,开始出现断条现象,熟断条率为7.5%。各配比的玉米-小麦混合粉鲜湿面条总评分均比纯小麦粉的低,玉米粉、小麦粉质量比为15∶85时制作的鲜湿面条总评分最高,感官品质较好。