面包老化抑制因素的研究

在西方国家,面包是餐桌上的主食,面包的质量与人们的健康和幸福息息相关.随着经济水平的提高,面包已经悄悄走进了我们的生活.但是,老化的面包口感差,易掉屑且香味丧失,不为广大消费者所接受.我们需要研究面包老化的机理,并从理论上寻找抑制面包老化的方法,提高面包的质量.本文综述了近年来国内外对面包老化的研究结果,从水分、淀粉结晶、添加剂、淀粉酶、贮存和温度几方面论述了抑制面包老化的方法.并对抑制面包老化,全面提高面包质量的研究趋势进行了展望.     

谷朊粉对速冻馒头品质影响的研究

研究了谷朊粉的添加量对速冻馒头比容、柔软度、总评分等品质的影响。实验结果表明：随着谷朊粉添加量的变化,速冻馒头的比容、柔软度、总评分也发生变化。合理掌握谷朊粉的添加量可以使速冻馒头获得较好感官品质、比容、柔软度、总评分。     

不同面筋蛋白组分对面包品质的影响

为探究麦谷蛋白、麦醇溶蛋白以及两者的不同配比对面包品质的影响,将谷朊粉、提取的麦谷蛋白、麦醇溶蛋白分别添加到面包中,以面包比容为评价指标,研究其对面包品质的影响。结果表明,三者均能提高面包比容,且在质量分数1.5%（占面粉基）的添加量下,麦谷蛋白与谷朊粉的改善效果相当。再将麦谷蛋白与麦醇溶蛋白重新配比添加到面包中,当麦谷蛋白/麦醇溶蛋白质量比为3∶1时,在质量分数1.1%（占面粉基）的添加量下,与空白组相比,面包比容提高了11.4%,面包硬度降低。贮藏5 d后,面包硬度增量低于空白组13.1%,延缓了面包的老化,且效果优于质量分数1.5%（占面粉基）谷朊粉添加量的效果。     

乳清分离蛋白对无麸质大米面包品质的影响

本研究将乳清分离蛋白（Whey protein isolate, WPI）添加到无麸质大米面包中,通过质构、切面分析和比容等方法综合评价面包品质,并运用流变学方法研究其原因。结果表明：WPI能显著降低米粉糊化黏度,提升糊化稳定性。在面团流变测试中,WPI弱化能生面团刚性结构,增加面团黏性,使发酵气体产生量最高提升14.01%。温度扫描表明WPI能降低面团热诱导凝胶tan δ值,熟化时面包内部支撑能力更强。在面包品质方面,添加WPI能显著提升面包比容,加深表皮色泽,降低面包芯硬度,使面包内部孔隙趋向多而密集,而WPI添加量超过12%时会导致面包表面开裂,硬度增加。综上所述,WPI添加量在8%~12%范围内能显著提升大米面包整体品质。     

Laboratory‐scale Dry/Wet‐Milling Process for the Extraction of Starch and Gluten from Wheat

A laboratory‐scale process is presented for the manufacture of starch and gluten from wheat. Main feature of this process is that whole wheat kernels are crushed dry between smooth rolls prior to wet disintegration in excess water in such way that gluten formation is prevented and fibres can be removed by sieving. Centrifugation of the endosperm suspension yields a dough which can be separated into starch and gluten using an established batter process. The results suggest that starch recovery is increased in comparison to a conventional wheat flour process without a concomitant decrease in protein recovery. Although starch purification was omitted, a total starch with a low protein content is obtained. On the other hand, the protein content of the gluten fraction is rather low due to difficulties in removing the starch. Despite this, the effect on dough mechanical properties by the addition of gluten obtained from wet‐milled wheat is comparable to the effect of gluten from flour.     

魔芋葡甘聚糖改善馒头品质的研究

为改善馒头老化,在馒头制作过程中,研究改良剂魔芋葡甘聚糖(konjac glucomannan,KGM)对馒头制品抗老化的影响。采用响应面方法(Plackett-Burman 试验)筛选并确定馒头的制作因素,并用正交试验对工艺进行优化。结果表明：面粉200g、加水量100.0mL、KGM 添加量12.5g、酵母粉2g、白砂糖1g、搅拌1h、醒发时间3h。根据优化条件下制得的馒头表皮光滑、高挺、比容大、内部结构细腻,并可改善馒头老化速度。     

添加剂对面包老化的影响

综述了添加淀粉酶、乳化剂、起酥油、可溶性蛋白、戊聚糖和水解胶体等品质改良剂对面包老化的影响,根据不同面粉的要求正确、合理选用一种或几种添加剂,能达到延缓面包老化的目的。     

酶制剂对全麦面包品质作用分析

全麦面包富含各类有益于人体健康的营养物质,但其消费量却远低于白面包,其原因主要在于全麦面包质地坚韧且感官品质不佳,因此需要对全麦面包的品质进行改良。添加酶制剂是全麦面包品质优化措施之一。本文阐述了木聚糖酶、α-淀粉酶、植酸酶、淀粉葡萄糖苷酶、葡萄糖氧化酶及脂肪酶单独作用时对全麦面包的比容、质构及老化方面的影响及作用机制,并介绍了复合酶制剂应用于改良全麦面包的研究成果。通过多种酶制剂的复配,可以更全面地改善全麦面包的品质,避开了单一酶制剂对全麦面包品质改良的局限性。     

Characterization of the Bread Made with Durum Wheat Semolina Rendered Gluten Free by Sourdough Biotechnology in Comparison with Commercial Gluten‐Free Products

Durum wheat semolina was fermented with sourdough lactic acid bacteria and fungal proteases aiming at a complete gluten hydrolysis. The gluten‐free (GF) semolina, added with naturally GF ingredients and structuring agents, was used to produce bread (rendered GF bread; rGFB) at industrial level. An integrated approach including the characterization of the main chemical, nutritional, structural, and sensory features was used to compare rGFB to a gluten‐containing bread and to 5 commercial naturally GF breads. High‐performance liquid chromatography was used for free amino acids (FAAs), organic acids, and ethanol analysis. A methanolic extract was used for determining total phenols and antioxidant activity. The bread characterization also included the analysis of dietary fibers, mycotoxins, vitamins, and heavy metals. Beyond chemical analysis, nutritional profile was evaluated considering the in vitro protein digestibility and the predicted glycemic index, while the instrumental texture profile analysis was performed to investigate the structure and the physical/mechanical properties of the baked goods. Beyond the huge potential of market expansion, the main advantages of durum wheat semolina rendered GF can be resumed in the high availability of FAAs, the high protein digestibility, the low starch hydrolysis index, and the better technological properties of bread compared to the commercial GF products currently present on the market. Vitamins, minerals, and dietary fiber profiles are comparable to those of gluten‐containing wheat bread. Also the sensory profile, determined by a panel test, can be considered the most similar to those of conventional baked goods, showing all the sourdough bread classic attributes.     

发酵时间对馒头品质及面筋蛋白结构的影响

利用体积仪、质构仪和傅里叶变换红外光谱分别测定馒头比容、质构特性与面筋蛋白二级结构,探究发酵时间对馒头品质及面筋蛋白结构的影响。结果表明：馒头中醇溶蛋白与麦谷蛋白中β-折叠含量均为最高。随着发酵时间的不断延长,醇溶蛋白中β-折叠、α-螺旋相对含量无显著性变化,无规则卷曲逐渐减少,而β-转角则逐渐增加;羟基吸收带逐渐增强,醇溶蛋白的水合作用增强。麦谷蛋白中α-螺旋与无规则卷曲相对含量变化不大,β-折叠相对含量先上升后下降,而β-转角相对含量则是先下降后上升;羟基带强度逐渐减弱;当发酵时间延长到80?min时,麦谷蛋白红外光谱位于1?082?cm－1与1?155?cm－1处的峰消失,可能是蛋白质环状结构的C—C振动减弱。     

Current and Forward‐Looking Approaches to Technological and Nutritional Improvements of Gluten‐Free Bread with Legume Flours: A Critical Review

The gluten‐free market currently offers a range of products which can be safely consumed by patients affected by celiac disease. Nevertheless, challenges for optimal formulation remain on the way in terms of appreciable texture, flavor, and adequate nutritional characteristics. Within that framework, legumes have recently attracted attention among scientists as structure‐ and texture‐forming agents, as source of nutrients and bioactive compounds, and as a low‐glycemic‐index ingredient. This work aims at providing an updated and comprehensive overview of the advantages and disadvantages in the use of legumes in gluten‐free breadmaking. It also shows how legumes can contribute to tackling the main technological, nutritional, and organoleptic challenges. From this critical analysis, it emerged that viscoelastic properties of gluten‐free bread batter can be enhanced by the use of carob germ, chickpea, lupin, and soybean. Gluten‐free bread organoleptic acceptability can be improved by incorporating leguminous flours, such as carob, chickpea, lupin, and soybean. Moreover, a better nutritional quality of gluten‐free bread can be obtained by the addition of chickpea and soybean. Gaps and needs in the use of legumes in gluten‐free breadmaking emerged and were gathered together to have a sound basis for future studies. The technological and nutritional potential of sourdough should be more extensively exploited. Moreover, in vitro and in vivo studies should be prompted to understand the health benefits of bread formulated with legumes. A holistic approach, interfacing food science, nutrition, and health might help to have, on the market, products with improved sensory properties and nutritional profile.     

Water Redistribution and Structural Changes of Starch During Storage of a Gluten‐free Bread

The objective of the present work was to analyze molecular and supramolecular changes of bread starch and to relate bread firmness increase during storage with starch recrystallization and water hydration levels and migration in gluten‐free bread. At the studied conditions starch was in the supercooled region of the state diagram, at a temperature between T_g (glass transition temperature) and T_m (melting temperature), feasible to crystallize. The crystalline degree during storage was followed by the intensity increase in the X‐ray diffraction peaks. During bread storage, water migration occurred from the crumb towards the crust. Water amount and redistribution affected the kind of starch crystallites formed and firmness of aged bread. It was not the total amount of crystalline fraction that determined bread firmness, but the type of crystallites formed. These observations are a further evidence that bread firmness development and starch recrystallization, although being related phenomena, are obviously separate events.     

Effect of hydrocolloids on gluten‐free batter properties and bread quality

The objectives of this study were to assess the effect of the addition of different hydrocolloids on gluten‐free batter properties and bread quality and to obtain information about the relationship between dough consistency and bread quality. Breads were made of rice, corn and soy flours and 158% water. Following hydrocolloids were added: carrageenan (C), alginate (Al), xanthan gum (XG), carboxymethylcellulose (CMC) and gelatine (Gel). Batter consistency, bread specific volume (SV), crumb analysis, crust colour, crumb hardness and staling rate were determined. Hydrocolloids increased batter consistencies: the highest value was obtained with XG, which doubled that of control batter, followed by CMC. Breads with hydrocolloid presented higher SV than control, especially with XG whose SV was 18.3% higher than that of control bread. A positive correlation was found between SV and batter consistency (r = 0.94; P < 0.05). Crumbs with Gel, XG and CMC presented higher cell average size. XG and CMC crumbs looked spongier. Breads containing hydrocolloid evidenced lighter crusts. Crumb firmness was decreased by XG and CMC addition, and staling rate was slower. Overall, XG was the hydrocolloid that most improved gluten‐free bread quality. These results show that, in formulations with high water content, batter consistency is strongly associated with bread volume.     

Thermal and Rheological Properties of Dough and Bread as Affected by Various Cross‐linked Cornstarch Substitutions

Various kinds of cross‐linked cornstarches (CLCSs) were used to substitute for wheat flour (5 and 10%), and thermal and rheological properties of dough and bread were examined. The pastes of the substituted flours had lower gelatinization temperatures and higher viscosities than those of the control. The substitution with low‐swelling waxy CLCS (L‐CWCS) had higher paste consistency and lower transition enthalpy than those with high‐ or low‐swelling non‐waxy CLCS (H‐CNCS or L‐CNCS) or the control. The substitutions with L‐CNCS made harder doughs and higher firmness of breadcrumbs during storage than the others. The specific volumes of breads with cross‐linked cornstarch substitutions were slightly smaller than that of the control because of the lack of gluten. The firmness of bread substituted with L‐CWCS was softer than that with H‐ or L‐CNCS. In addition, the breads with H‐CNCS were softer than that with L‐CNCS. The results showed that the compression stress of dough was highly positively correlated with firmness of breads after storage for one and three days (r = 0.876, P < 0.01 and r = 0.809, P < 0.05, respectively). Also, significant positive correlations were detected between the transition enthalpy of dough and firmness of breads after storage for one and three days (r = 0.840, P < 0.05 and r = 0.853, P < 0.05, respectively), whereas no correlation between transition enthalpies of breadcrumbs and firmness of breads was observed.     

Aging Effects on Sorbitol‐ and Non‐Crystallizing Sorbitol‐Plasticized Tapioca Starch Films

The effect of aging on the properties of tapioca starch films plasticized with either sorbitol (S) or non‐crystallizing sorbitol (NCS) was investigated in this study. Tapioca starch, plasticizer and deionized water were mixed, heated, cast on high‐density polyethylene plates and dried at ambient conditions. The results showed that S was more effective in plasticizing fresh starch film than NCS. However, sorbitol crystallization was observed in S‐plasticized starch film after one month of storage, while there was no crystallization observed in NCS‐plasticized starch film after two months of storage. Mechanical properties of both S‐ and NCS‐plasticized starch films changed significantly with time, but with less change in the NCS‐plasticized films. Tensile strength, elastic modulus and toughness increased over time; conversely, elongation decreased. Additionally, the water vapor transmission rate decreased as storage time increased. The fact that mechanical properties of both S‐ and NCS‐plasticized films changed is likely due to an increase in crystallinity of the starch in the films with time.     

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。     

Effect of adding fresh and freeze‐dried buckwheat sourdough on gluten‐free bread quality

This study demonstrates new possibilities in using freeze‐dried buckwheat sourdoughs in the processing of gluten‐free bread (GFB). Fresh and freeze‐dried (at temperatures of 20, 40 and 60 °C) sourdoughs were added in the amounts of 10, 20, 30 and 40% of the total flour content. Significant and beneficial changes in the quality of bread under the influence of different quantities of fresh and freeze‐dried sourdoughs additive were observed. Freeze‐dried buckwheat sourdoughs at the level of 20 and 30% gave the best baking results for GFB. pH of bread significantly changed, which had a positive effect on increasing its suitability for the storage. Buckwheat sourdough dried at 40 °C is the most highly recommended for GFB processing. Higher temperatures (60 °C) caused the least change in bread volume; however, a bitter aftertaste from burning was slightly detectable. Freeze‐dried buckwheat sourdoughs can be used directly in processing, thus eliminating the long fermentation of sourdough.