嗜热真菌耐热木聚糖酶对面包品质的改善

研究了纯化的耐热木聚糖酶对面包品质及老化的影响，探讨了耐热木聚糖酶影响面包发酵及烘烤过程的作用机理。适量添加木聚糖酶的面包体积显著增加且面包芯的组织结构优良，同时老化变缓：本试验条件下，添加纯酶1．5mg／kg为最适酶添加量，体积增加43％，硬度减小44％，老化速度放缓近一半。     

几种改良剂对面包老化的影响

通过实验对比研究了α-淀粉酶、木聚糖酶、乳化油脂、苹果纤维对面包老化的影响。实验结果表明,适量添加α-淀粉酶、木聚糖酶、乳化油脂、苹果纤维对面包老化都有延缓作用,其中乳化油脂对面包老化速率延缓作用较大,α-淀粉酶、木聚糖酶、苹果纤维对面包老化速率延缓作用相对较小。     

绵毛嗜热丝菌(Thermomyces lanuginosus)木聚糖酶对面包品质的改善

研究了绵毛嗜热丝菌（Thermomyces lanuginosus）W205耐热木聚糖酶的添加量对面包品质及老化的影响。结果表明,添加2．5～5mg／kg纯酶为较适酶添加量。在此添加量下,面包比容增加17％,面包瓤硬度与高径比略为下降,面包内部质构明显提高,老化速率放缓。     

绵毛嗜热丝孢菌(Thermomyces lanuginosus)木聚糖酶对面包品质的改善

研究了绵毛嗜热丝孢菌(Thermomyces lanuginosus)W205耐热木聚糖酶的添加量对面包品质及老化的影响。结果表明,添加2·5~5mg/kg纯酶为较适酶添加量。在此添加量下,面包比容增加17%,面包瓤硬度与高径比略为下降,面包内部质构明显提高,老化速率放缓。     

酶制剂对面包品质的影响

研究木聚糖酶、脂肪酶和蛋白酶对面包品质及老化的影响。通过正交试验确立添加0.001%木聚糖酶、0.00013%脂肪酶,不添加蛋白酶为加工面包的最优化工艺条件。脂肪酶是影响感官的主要因素,三种酶共同影响面包的硬度及破碎性。     

橄榄绿链霉菌木聚糖酶组对面包品质的改善

本文研究了橄榄绿链霉菌(Streptomyces olivaceovirdis)E-86产生的分子量约1200kDa木聚糖酶组对面包品质的影响。焙烤试验结果表明，添加20ppm木聚糖酶组的面包比容增加了38．8％，新鲜面包芯硬度降低了1／3，面包老化速率也明显减小。该木聚糖酶组具有内切酶和切枝酶的活性，在面粉中水溶性和水不溶性阿拉伯木聚糖组成比例范围内，对水不溶性阿拉伯木聚糖的降解作用比水溶性阿拉伯木聚糖快。因此，该酶组能够改善面包的品质。     

木聚糖酶对面粉糊化特性和面包品质的影响

探讨不同添加量的木聚糖酶对面粉的糊化特性、面包焙烤品质以及面包贮存品质的影响.结果表明:添加木聚糖酶对面粉的糊化温度、衰减值、回生值影响不大,但可降低面粉的峰值黏度、最低黏度和最终黏度,木聚糖酶能有效地改善面包焙烤品质,显著增加面包比容,有效改善面包的硬度和弹性,明显的降低了面包的老化程度.当木聚糖酶添加量为10 mL/kg面粉时,面包焙烤品质及贮存效果最佳.     

中性木聚糖酶在面包制作中的应用

通过探讨不同浓度的中性木聚糖酶对面粉粉质、面包焙烤品质以及面包贮存过程中老化程度的影响 ,研究中性木聚糖酶作为焙烤添加剂的可行性。结果表明 ,中性木聚糖酶能显著地改善面粉的粉质 ,当添加量为 0 3mL/kg(面粉 )时 ,面团的形成时间可减少 5 0 %左右 ;能有效地改善面包焙烤品质 ,明显地增加面包的体积和比容 ,同时可以改善面包心的弹性和硬度 ,减小面包皮的硬度 ;酶添加范围为 0 0 5～ 0 48mL/kg(面粉 ) ,能增加面包的抗老化作用 ,贮藏 7d后 ,面包的硬度和弹性没有明显变化 ,延长了货架期     

酶制剂对于麸皮面包的改良研究

研究了纤维素酶、真菌木聚糖酶、葡萄糖氧化酶、真菌α-淀粉酶对麸皮面包品质的影响。结果显示,四种酶单独使用都能很大程度上增大麸皮面包的体积,改善其质构,降低其老化速率。在此基础上,利用正交实验得出复配型酶制剂的最佳配方。     

酶在面包加工中的应用及研究现状

酶是一种高效、安全、纯天然的生物制品。针对酶对面团流变学特性、对面包感官品质和保藏老化以及对面包冷冻面团等方面的影响进行了综述,介绍了淀粉酶、木聚糖酶、谷氨酰胺转氨酶、脂肪酶、葡萄糖氧化酶、巯基氧化酶等在面包加工中的应用,为酶在面包加工中的进一步开发应用提供参考。     

Improvement of the breadmaking quality of wheat flour by the hyperthermophilic xylanase B from Thermotoga maritima

The study was carried out to investigate the effect of hyperthermophilic xylanase B (XynB) from Thermotoga maritima on the properties of wheat bread and its staling during storage. The presence of XynB in the dough led to improvements in the breadmaking quality (i.e. specific volume and crumb structure) and provided an anti-staling effect on breads compared to the control. Addition of XynB could cause ≈60% increase in specific volume in comparison with the control. By fitting the crumb firming kinetics during storage to the Avrami equation, it showed that XynB retarded the bread staling by reducing the initial crumb firmness and the firming process during storage. XynB hydrolyzed the isolated WU-AX faster than WE-AX under the ratio of wheat AX in wheat flour. Improvement of bread quality by XynB can partly be ascribed to the enzyme specificity.     

Effect of different carbohydrases on fresh bread texture and bread staling

The effect of cellulase, xylanase and #-glucanase on the properties of wheat bread and its staling during storage was studied. The presence of the carbohydrases tested led to breads with high specific volume compared to the control. The texture profile analysis was greatly modified in that the firmness of bread crumb was reduced by all the carbohydrases. A kinetic study of the firmness along with the storage by the Avrami equation showed that the presence of carbohydrases produced softer crumbs and also reduced the rate of bread firming, although no great differences were found between enzymes. Since retrogradation of starch is one of most important factors related to bread staling, the modification of the amylopectin retrogradation was measured by scanning calorimetry. Those studies showed that all the carbohydrases decrease the starch retrogradation, and that the xylanases had the greatest effect. The simultaneous analysis of the firming and starch retrogradation results revealed that the anti-staling effect of xylanase might be due to the retardation in the starch retrogradation, while in the case of cellulase and #-glucanase some other mechanism should be implied in their anti-staling action.     

Impact of microbial transglutaminase on the staling behaviour of enzyme-supplemented pan breads

The effects of microbial transglutaminase (TGM) when added singly and in combination with amylolytic (-amylase, NMYL) and non-amylolytic (xylanase) enzymes on the textural profile of fresh pan beads and pan breads stored for up to 20 days have been investigated in samples made with low and high extraction rate wheat flours following a sponge-dough process. White and whole-wheat enzyme-supplemented bread samples evidenced a similar sensory firming profile but a different quantitative instrumental staling pattern during storage. Two groups of samples with different staling behaviour can be defined according to the absence (faster staling kinetics) or the presence (slower kinetics) of NMYL in the bread formula, the separation being particularly clear for hardness, cohesiveness and resilience in white bread samples. TGM when added to NMYL-supplemented doughs induced synergistic beneficial effects on fresh bread quality and staling kinetics retardation. The binary combination led to breads with softer and less chewy fresh crumbs, increased initial crumb cohesiveness and resilience, and slower crumb staling kinetics and sensory deterioration during storage, particularly for samples made with white flour.     

Staling in Starch Bread: the Effect of Gluten Additions on Specific Loaf Volume and Firming Rate

Hypotheses on the role of gluten in bread staling range from gluten having an anti-firming effect, or no effect on firming, to gluten-starch interactions being essential for bread firming. To test these hypotheses, the firming rate of starch bread made from protein-free synthetic flour was compared with that of starch-gluten breads made from synthetic flours containing 1–15% gluten (Fig. 1). Only loaves of similar specific loaf volume and crumb moisture content were compared to eliminate these parameters as variables that might influence firming rate. The starch breads clearly increased in firmness up to six days, indicating that gluten was not essential to the firming process, starch alone causing bread to firm with time. The starch-10% gluten breads and starch-15% gluten breads had very similar specific loaf volumes, moisture contents and firming rates to that of the starch breads. This indicates that protein possibly has some role in firming, because if only starch has a role in firming then adding gluten would effectively dilute the starch and reduce the rate of firming. We propose that increasing bread firmness results from glucan chains of partially leached amylose and amylo-pectin attached to swollen starch granules forming hydrogen bonds with other starch granules and, to a smaller extent, with gluten fibrils.     

Effect of baking conditions and storage with crust on the moisture profile,local textural properties and staling kinetics of pan bread

To investigate the impact of baking conditions on staling kinetics and mechanical properties, pan breads were baked at 180 °C/34 min and 220 °C/28.6 min using a ventilated oven and metallic moulds. After baking, bread slices were stored with and without crust at 15 °C in hermetic boxes for 9 days. This investigation provides a textural and physical analysis by examining the Young's modulus, crumb density and crust/crumb ratio during storage. In order to understand the relationship between firmness and moisture content, a moisture profile and a Young's modulus profile were determined during the storage of bread. To fit the staling, a first order model was used. It was found that the kinetics were faster for samples baked with a fast heating rate than for those baked with a slow heating rate. Moreover, the staling rate of bread stored with crust was faster than for bread without crust and the outer crust area staled more rapidly than the centre of the bread slice. These results suggest that the firming of the crumb is related to moisture distribution between the crumb and crust and to the impact of local baking conditions on local firmness.     

Effect of chitosan on physical and chemical processes during bread baking and staling

The objective of this research was to investigate the effect of chitosan on the interaction of water with bread ingredients and on the rate of staling. The changes in freezable bound water and total water contents in bread crumb were assessed by differential scanning calorimetry from water melting and evaporation endothermic peak areas. It was found that freezable water content and total water content in bread crumb decrease during staling more rapidly in the presence of chitosan. The weak interaction of freezable water with protein and starch polymeric chains in bread crumb becomes stronger, but the interaction of nonfreezable bound water with protein and starch molecules in bread crumb becomes weaker in the course of staling during bread storage. Two stages of bread crumb staling were indicated. Chitosan increases the rate of bread staling during both stages. It was suggested that during bread staling chitosan increases water migration rate from crumb to crust, prevents amylose-lipid complexation, and increases dehydration rate both for starch and gluten.     

Thermo-physical assessment of bread during staling

Staling of bread is a highly complex phenomenon that is not yet fully understood. This study examined the effect of staling on thermal (DSC) and thermo-physical (DMA) properties of bread. The staling process increased water migration from the crumb to the crust and increased unfreezable water (UFW) fraction. Amylopectin retrogradation incremented during bread staling, and it was showed that the loss in freezable water (FW) was caused from water incorporation into the starch crystalline structure and water migration from the crumb to the crust. DMA was able to follow the shrinking behavior of bread crumb during freezing. Crumb shrank through the entire cooling and freezing process. The matrix shifts through their freezing process incremented the rate of their contraction, probably due to the matrix dehydration as consequence of ice formation. The ageing process changes the thermo-mechanical profile of the crumb, and it was showed that a greater amount of retrogradated starch, affected significantly the contraction capacity of bread crumb.