Quality characteristics improvement of low‐phenylalanine toast bread

This study was designed to prepare and evaluate low‐phenylalanine toast bread made from gliadin‐free wheat flour and hydrocolloids. Wheat protein fraction (gliadin) rich in phenylalanine was extracted using aqueous alcohol solution for the production of low‐phenylalanine wheat flour. Pectin, gum arabic and carboxymethylcellulose (CMC) were used separately to improve the quality of bread at levels of 1, 2 and 3%. Chemical, rheological, organoleptic, baking, staling and microstructure of bread were studied. Phenylalanine content of gliadin‐free bread samples reduced by 43.2% compared with control. Separation of gliadin negatively affected the rheological properties of dough and baking quality of bread, while rheological properties, baking quality and staling were improved upon hydrocolloids addition. Microscopic examination of crumb structure revealed remarkable differences in control and treated breads. It was found that acceptable bread could be produced using gliadin‐free wheat flour with the addition of pectin or CMC up to 2 and 3%, respectively.     

Effects of temperature and water content on the formation of 3-chloropropane-1,2-diol fatty acid esters in palm oil under conditions simulating deep fat frying

The influence of NaCl addition, water content, heating temperature and heating time on the formation of 3-chloropropane-1,2-diol fatty acid esters (3-MCPD esters) in palm oil simulating deep fat frying was examined in this study. The results in our study showed that all those four factors had significant effects on the generation of 3-MCPD esters in palm oil during deep fat frying. There was a significant increase in the content of 3-MCPD esters formed in palm oil when heating time was 2 h. The effect of water content was the most evident in 3-MCPD esters formation. The heating process imparted an accretion of up to 130 % from 1,260 to 2,950 mg/kg with increasing the water dosage from 7 to 10 %. In addition, 3-MCPD esters were decomposed when heated at high temperatures for a long time (longer than 2 h).     

Formation of 3-chloropropane-1,2-diol in systems simulating processed foods

Formation of 3-chloropropane-1,2-diol (3-MCPD) from the precursors glycerol, triolein and soy lecithin in the presence of sodium chloride was studied. The precursors were reacted with sodium chloride in an emulsion stabilised with an emulsifier under conditions which modelled the thermal treatment of foods during processing. Three sets of experiments were carried out aimed to monitor the influence of various factors (NaCl, water content and temperature) on the yield of 3-MCPD. The formation of 3-MCPD strongly depended on the concentration of NaCl and reached a maximum level at about 4–7% NaCl. The highest amount of 3-MCPD was formed in media containing approximately 13–17% water. The amount of 3-MCPD increased with increasing temperature over the range 100–230 °C and reached its highest value at 230 °C. The production of 3-MCPD was also followed in models very closely related to selected foods which had been shown to have a high potential to yield 3-MCPD during processing (salami, beefburgers, processed cheese, biscuits, crackers, doughnuts). The highest levels of 3-MCPD were formed in models simulating salami as they had the highest content of both fat and salt of all the samples. The lowest amount of 3-MCPD was formed in the models simulating biscuits and crackers as they had a low salt content and, at the same time, their water content was below the optimum level.     

INSTRUMENTAL TEXTURE and BAKING QUALITY of HIGH-FIBER TOAST BREAD AS AFFECTED BY ADDED WHEAT MILL FRACTIONS

The effect of bran type, level of addition, particle size, addition of wheat germ, as well as other additives like improvers and dough conditioners, on the instrumental texture and baking quality of high-fiber toast bread (white pan bread) has been investigated. the specific loaf volume decreased significantly (3.45 cc/g) when the bran level was raised to 30%, but at 20% bran addition, the specific loaf volume was superior to that of the control bread. the specific loaf volume of test breads remained higher than the control bread up to a level of 7.5% wheat germ addition. Additives like ascorbic acid (50 ppm) and sodium stearoyl-2-lactylate (0.5%) further improved the baking quality of test bread samples. the objective texture values (measured as compression force, kg) indicated that the test bread with bran addition up to 20% and germ up to 7.5% possessed a softer texture (0.80 kg) than the control bread (1.02 kg). In comparison with control bread, the panelists gave higher sensory scores for all attributes of test bread samples containing up to 20% red coarse bran or up to 30% red fine bran. A similar trend in sensory quality of test samples containing up to 7.5% wheat germ was also observed. High-fiber toast bread made from white flour, equal proportions of coarse and fine bran at 20%, wheat germ at 7.5%, plus sodium stearoyl-2-lactylate at 0.5% levels, was found to possess softer texture and improved sensory quality than the whole wheat flour bread.     

Effects of yeast stress and pH on 3-monochloropropanediol (3-MCPD)-producing reactions in model dough systems

A major precursor of 3-monochloropropanediol (3-MCPD) in leavened cereal products is glycerol, which is formed as a natural by-product of yeast fermentation. However, yeast metabolism is affected by stresses such as low osmotic pressure from, for example, the incorporation of sugar or salt in the dough recipe. Tests with model doughs have shown that glycerol production was proportional to yeast mass and limited by available sugars, but that high levels of yeast inhibited 3-MCPD formation. The yeast fraction responsible for the inhibition of 3-MCPD in model dough was shown to be the soluble cytosol proteins, and the inhibition mechanism could be explained by the known reactions of 3-MCPD and/or its precursors with ammonia/amino acids (from yeast proteins). Added glucose did not increase the production of glycerol by yeast but it did promote the generation of 3-MCPD in cooked doughs. The latter effect was attributed to the removal of 3-MCPD inhibitors such as ammonia and amino acids by their reactions with added glucose (e.g. Maillard). The thermal generation of organic acids from added glucose also reduced the pH of cooked doughs, so the effect of pH and short-chain organic acids on 3-MCPD generation in dough was measured. There was a good correlation between initial dough pH and the level of 3-MCPD generated. The effect was weaker than that predicted by simple kinetic modelling, suggesting that the involvement of H⁺ and/or the organic acid was catalytic. The results showed that modifications to dough recipes involving the addition of reducing sugars and/or organic acids can have a significant impact on 3-MPCD generation in bakery products.     

Role of fat on the quality and shelf-life of gluten-free bread baked by Ohmic heating and conventional deck oven

The addition of fat to gluten-free (GF) bread can influence several quality attributes, such as texture and starch retrogradation. Therefore, the aim of this study was to investigate the influence of different fats on GF bread properties using two different baking methods (conventional and ohmic heating), in order to understand how these affect the physical bread quality, the formation of amylose-lipid complexes and its effect on crumb firming behavior. Fats (coconut, rapeseed, butter, and palm) with different physico-chemical properties, and physical state (solid, liquid) were tested in standard GF bread formulations. Results showed that fat significantly improved crumb pore uniformity. Crumb texture and pasting properties were mostly influenced by the type of fat, storage time and baking method. Staling was delayed in all breads added with fat due to the formation of amylose-lipid complexes, which were highest with palm fat and were usually higher when baked by ohmic heating.     

Citrate Starch — Application as Resistant Starch in Different Food Systems

Chemically modified starch was used as resistant starch (RS) to enhance the dietary fibre content in foods. Citrate starch was produced by esterification of starches of various origins and added to toast bread, wafers, pasta and extruded products. The RS content as well as relevant product features were determined and results compared to those of products without any citrate starch addition. The results show that the RS content in toast bread could be increased by approximately 3%, when 7.5% citrate starch was added, compared to non-fortified bread. Changes in product features due to addition of citrate starch could be compensated for by variation in the recipe, such as increasing the amount of water. Thus, appealing products could be obtained with an enriched dietary fibre content. The extend of the RS enhancement depends highly on the food system chosen.     

Effect of adding wheat bran and germ fractions on the chemical composition of high-fiber toast bread

The effect of the type of bran, level of addition, particle size and addition of wheat germ on the chemical composition of high-fiber toast bread was investigated. The bran and germ fractions were found to be high in ash, protein, fat and total dietary fiber contents. The wheat germ had a protein content of 27.88% compared with 11.35, 12.69 and 15.76% for white flour, whole wheat flour and red fine bran, respectively. The chemical composition of high-fiber breads, in terms of minerals, protein, fat and dietary fiber contents, was found to be far superior than that of the whole wheat flour (control) bread sample. Considering these results, it can be concluded that high-fiber toast bread, with lighter crumb color and improved sensory and nutritional qualities than the whole wheat flour bread, can be produced using white flour, and equal proportions of coarse and fine bran at 20%, germ at 7.5%, and sodium stearoyl-2-lactylate at 0.5% levels.     

UTILITY OF CIE TRISTIMULUS SYSTEM IN MEASURING THE OBJECTIVE CRUMB COLOR OF HIGH-FIBER TOAST BREAD FORMULATIONS

The major objectives of this study were to develop high‐fiber toast bread formulations with lighter crumb color and to evaluate the CIE tristimulus system to measure the color of crumb as affected by the addition of various flour mill fractions. The optimized straight‐dough bread making method (AACC method 10‐10B) was used for conducting the baking trials. CIE L* a* b* values of the crumb were measured. Additional color attributes, (whiteness value, redness index (RI), saturation index (SI) and total color difference (ΔE), were calculated from these L* a* b* values. Compared with flour samples, the germ and bran fractions had significantly lower CIE L* a* b* and whiteness values, but higher redness and saturation indices, indicating darker color and hue for the latter. Test bread samples having up to 30% bran and 10% germ, were lighter in crumb color than the control whole wheat flour bread. It was concluded that high‐fiber toast bread, with lighter crumb color than whole wheat flour bread, can be produced by using white flour, and equal proportions of coarse and fine bran at 20%, germ at 5%, and sodium stearoyl‐2‐lactylate at 0.5% levels. The CIE L*a* b* tristimulus system can effectively be utilized for distinguishing crumb color variations in toast bread samples.     

Occurrence of 3-chloropropane-1,2-diol and its esters in coffee

Fifteen coffee samples comprising green, roasted, decaffeinated and instant coffees were analysed for their content of free and bound 3-chloropropane-1,2-diol (3-MCPD). Green coffees contained only traces of the free 3-MCPD. 3-MCPD in roasted coffees was found at the level of 10.1–18.5 µg/kg. The highest 3-MCPD level of 18.5 µg/kg was found in one instant coffee sample and in coffees with very long time application during roasting. The final colour of the roasted coffee beans was directly linked to the 3-MCPD formed, the darker beans having the greatest concentration, and arabica coffees contained lower 3-MCPD levels than robusta coffees. The level of bound 3-MCPD varied between 6 µg/kg (soluble coffees) and 390 µg/kg (decaffeinated coffee) and exceeded the free 3-MCPD level 8–33 times. Arabica coffees contained higher levels of the bound 3-MCPD than robusta coffees. The recognised precursors of 3-MCPD (salt, glycerol, lipids) were also determined and their influence on the formation of the free and bound 3-MCPD was discussed.     

Influence of composition,moisture, pH and temperature on the formation and decay kinetics of monochloropropanediols in wheat flour dough

A study of the formation and decay kinetics of 3-chloropropane-1,2-diol (3-MCPD) and 2-chloropropane-1,3-diol (2-MCPD) in model dough systems is reported. The influence of ingredient composition, moisture, pH and temperature were assessed. It was shown that white flour, salt and water alone were sufficient to generate 2-MCPD and 3-MCPD. The formation of 3-MCPD agreed with zero order kinetics and occurred most readily in dry, full recipe dough; below 15%, the exact moisture content was not critical. The formation of 2-MCPD followed that of 3-MCPD but at approximately one fifth of the rate, irrespective of dough type. The decay of 3-MCPD was consistent with first order kinetics and the overall rate in dough was slower than that in pure water. The decay reaction was inhibited by a decrease in moisture content and a drop in pH seen at high temperatures in the cereal systems investigated. One of the products of 3-MCPD decay in dough was 2-chloropropane-1,3-diol (2-MCPD). Data obtained from the model system studies showed good agreement with 3-MCPD levels formed in real foods. Possible mechanisms of decay and formation in dough are discussed.     

Fatty acid esters of 3-chloropropane-1,2-diol in edible oils.

A series of 25 virgin and refined edible oils, obtained from retailers, was analyzed for levels of free 3-chloropropane-1,2-diol (3-MCPD) and 3-MCPD released from esters with higher fatty acids (bound 3-MCPD). Oils containing free 3-MCPD ranging from <3 microg kg-1 (LOD) to 24 microg kg-1. Surprisingly, bound 3-MCPD levels were much higher and varied between <100 (LOD) and 2462 microg kg-1. On average, virgin oils had relatively low levels of bound 3-MCPD, ranging from <100 (LOD) to <300 microg kg-1 (LOQ). Higher levels of bound 3-MCPD were found in oils from roasted oilseeds (337 microg kg-1) and in the majority of refined oils (<300-2462 microg kg-1), including refined olive oils. In general, it appears that the formation of bound 3-MCPD in oils is linked to preliminary heat treatment of oilseeds and to the process of oil refining. Analysis of unrefined, de-gummed, bleached, and deodorized rapeseed oil showed that the level of bound MCPD decreased during the refining process. However, additional heating of seed oils for 30 min at temperatures ranging from 100 to 280 degrees C, and heating at 230 degrees C (260 degrees C) for up to 8 h, led to an increase in bound 3-MCPD levels. On the other hand, heating of olive oil resulted in a decrease in bound 3-MCPD levels. For comparison, fat isolated from salami was analyzed for intact fatty acid esters of 3-MCPD. This fat contained bound 3-MCPD at a level of 1670 microg kg-1 and the fatty acid esters of 3-MCPD mainly consisted of 3-MCPD diesters; monoesters of 3-MCPD were present in smaller amounts. The major types of 3-MCPD diesters (about 85%) were mixed diesters of palmitic acid with C18 fatty acids (stearic, oleic, linoleic acids). These diesters were followed by 3-MCPD distearate (11%) and 3-MCPD dipalmitate (4%). Generally, very little 3-MCPD existed as the free compound (31 microg kg-1).     

The effects of domestic cooking on the levels of 3-monochloropropanediol in foods

The results are reported of a study to determine the effect of domestic cooking procedures on the level of 3-monochloropropane-1,2-diol (3-MCPD) in selected foods. Samples of 23 foods comprising stock cubes, gravies, a cake mix, batters, breads, cheese and meats were subjected to a range of cooking procedures including grilling, toasting and microwaving. The resulting levels of 3-MCPD were compared with those present in the foods before cooking. Grilling and toasting produced substantial increases in the 3-MCPD content of bread, forming up to 0.3mg/kg, and of most cheeses, resulting in levels of up to about 0.1mg/kg. Microwave cooking produced elevated 3-MCPD levels in some cheeses. Frying laboratoryproduced batters increased 3-MCPD levels to about 0.1mg/kg whereas a retail batter contained no detectable 3-MCPD when fried. The remaining foods showed little or no discernible increase on cooking.     

Enrichment of Egyptian 'Balady' bread. Part 1. Baking studies, physical and sensory evaluation of enrichment with decorticated cracked broadbeans flour (Vicia faba L.)

Physical, rheological and baking properties of decorticated cracked broadbeans-wheat composite flours were studied and the acceptability of the Egyptian 'Balady' bread was evaluated by sensory tests. Decorticated cracked broadbeans flour (DCBF) was used to replace 5%, 10%, 15% and 20% of the wheat flour (WF) in bread. Farinographic studies showed that water absorption, arrival time and dough development time increased as the amount of DCBF increased, while dough stability time increased at 5% and 10% of DCBF substitution and decreased at 15% and 20% substitution. Also, the extensographic energy of the dough decreased as DCBF substitution increased, while the ratio between resistence and extensibility increased. There was a decrease in peak viscosity with increased amounts of DCBF. A reduction of the diameter and weight of bread loaf was observed as the amount of DCBF increased. The sensory properties of 'Balady' bread showed that at the two levels of 5% and 10% DCBF-substitution, the 'Balady' loaves did not show any significant differences (P > 0.05). It is concluded that the replacement of bread flour (WF) with up to 10% decorticated cracked broadbeans flour produced acceptable Egyptian 'Balady' bread.     

几种改良剂对板栗面包焙烤品质及老化指标的影响

采用单因素实验,研究了黄原胶、α-淀粉酶、单甘酯三种面包改良剂对板栗面包焙烤品质及老化指标的影响。实验结果表明：黄原胶的添加对板栗面包的感官品质及老化指标均产生了显著影响,当添加量为板栗粉及面包粉总重的1%时,板栗面包具有良好的焙烤品质,贮存7天后,其硬度比对照组下降了9%;不同添加量的单甘酯对板栗面包的老化均有延缓作用,但对面包的焙烤品质均产生负面影响;当α-淀粉酶添加量为0.01%或0.005%时,板栗面包的抗老化效果及焙烤性能均好于对照组,但当添加量较高时,面包焙烤品质骤然下降。     

Enrichment of Egyptian ‘Balady’ bread. Part 1. Baking studies,physical and sensory evaluation of enrichment with decorticated cracked broadbeans flour (Vicia faba L.)

Physical, rheological and baking properties of decorticated cracked broadbeans‐wheat composite flours were studied and the acceptability of the Egyptian ‘Balady’ bread was evaluated by sensory tests. Decorticated cracked broadbeans flour (DCBF) was used to replace 5%, 10%, 15% and 20% of the wheat flour (WF) in bread. Farinographic studies showed that water absorption, arrival time and dough development time increased as the amount of DCBF increased, while dough stability time increased at 5% and 10% of DCBF substitution and decreased at 15% and 20% substitution. Also, the extensographic energy of the dough decreased as DCBF substitution increased, while the ratio between resistence and extensibility increased. There was a decrease in peak viscosity with increased amounts of DCBF. A reduction of the diameter and weight of bread loaf was observed as the amount of DCBF increased. The sensory properties of ‘Balady’ bread showed that at the two levels of 5% and 10% DCBF‐substitution, the ‘Balady’ loaves did not show any significant differences (P > 0.05). It is concluded that the replacement of bread flour (WF) with up to 10% decorticated cracked broadbeans flour produced acceptable Egyptian ‘Balady’ bread.     

面包专用粉试验方法的研究

烘焙试验是检验面包专用粉操作性能和食用品质最直接、最有效的方法。因此,立足烘焙试验,从面包的制作工艺和品种入手,发现在面包的制作过程中将盐、糖和酵母分别溶解依次加入面粉,对面包的质量及试验结果至关重要。在试验品种方面,主食面包最易区分面包的结构层次;无盖土司最能反映面包的体积和外在质量;圆形面包则可检验面包粉拉力比数的适宜程度,表明面团的耐搅拌、耐醒发及持气能力的大小。     

EFFECT OF BAKING INGREDIENTS AND MIXING DURATION ON DOUGH DEVELOPMENT, GAS RELEASE AND BREAD MAKING PROPERTIES

Three trials were carried out to determine the effect of wet gluten, acetic acid, fat, sodium chloride and mixing duration on dough development, gas release and bread characteristics using regression analysis. Maximum dough height was significantly affected by acetic acid, wet gluten, mixing duration and sodium chloride whereas maximum gas formation was significantly affected by acetic acid and sodium chloride levels. The addition of fat had significant effects on bread volume. Sodium chloride affected overall acceptability followed by wet gluten, mixing duration and fat levels. Bread volume and overall acceptability decreased with an increase in mixing duration. Increased levels of sodium chloride increased bread volume and overall acceptability and decreased CO₂ production. Addition of fat at a level of more than 3% caused a decrease in acceptability. Bread volume and acceptability progressively increased with the increase in wet gluten levels.     

单糖与氯化钠模型反应中3-氯-1,2-丙二醇的形成

以"单糖+氯化钠+水"为模型进行热反应,研究3-氯-1,2-丙二醇(3-monochloropropane-1,2-diol,3-MCPD)的形成机理和消长规律。结果表明,在"葡萄糖+氯化钠+水"模型反应中,反应温度对3-MCPD的形成影响最大,其次是氯化钠添加量、反应时间和葡萄糖添加量;在"单糖+氯化钠+水"模型中,6种单糖都生成了3-MCPD,其中核糖和氯化钠反应生成的3-MCPD量最大(30.604μg/kg),果糖生成的量最小(2.498 6μg/kg);在"葡萄糖+氯化钠+水"模型中,反应后生成的挥发性成分5-羟甲基糠醛含量最大,然后是糠醛和2,5-二甲酰基呋喃。根据实验结果探讨3-MCPD的形成机理,提出在单糖模型反应中缩水甘油可能是关键的中间体。