食品酶制剂对冷冻面团流变学和微结构的影响

应用动态流变仪,Brabender拉伸仪,扫描电子显微镜(SEM)研究了葡萄糖氧化酶和谷氨酰胺转胺酶对冷冻面团粘弹模性量粘弹模量,抗拉伸阻力R5及微结构影响。空白面团(未加添加剂),含有葡萄糖氧化酶面团和含有谷氨酰胺转胺酶面团于-18℃冷冻贮藏7,21,35d,随冷冻贮藏时间延长,面团弹性模量(G′)降低。在同一冷冻贮藏时期内空白面团弹性模量最小,添加葡萄糖氧化酶面团弹性模量最大;含有葡萄糖氧化酶和含有谷氨酰胺转胺酶面团抗拉伸阻力R5大于空白面团。葡萄糖氧化酶和谷氨酰胺转胺酶使新鲜面团(未冷冻面团)面筋网络增强,淀粉颗粒镶嵌于交错的面筋网络之间,在-18℃经过35d冷冻贮藏,空白面团面筋网络不再连续,支离破碎,并与淀粉颗粒分离,而且面筋膜变薄。含有葡萄糖氧化酶和含有谷氨酰胺转胺酶面团依然有大量连续面筋网络存在。葡萄糖氧化酶和谷氨酰胺转胺酶抑制了面团弹性模量和抗拉伸阻力R5的恶化,而且抑制冰晶对面团中面筋三维网络结构的破坏。     

重组华根霉脂肪酶协同转谷氨酰胺酶提高冷冻面团抗冻发酵特性的研究

采用差示扫描量热仪和F3流变发酵仪研究重组华根霉脂肪酶(RCL)和转谷氨酰胺酶(TG)共同作用对冷冻面团抗冻发酵特性的影响。将面团于-18℃冻藏0、7、21、35d,结果发现:随着冻藏时间的延长,甘油含量有所降低,可冻结水含量增加;引入RCL和TG到冷冻面团中可以显著增加面团中的甘油含量,显著降低面团中可冻结水的含量,减少冰晶体的形成,并且可以提高酵母的存活数。F3流变发酵仪测定面团的发酵流变学特性,结果表明:RCL和TG同时作用可以显著降低冻藏对面团发酵高度的削弱作用,改善酵母的发酵性能和增加面团的持气率。     

面团配方对冷冻面团发酵活力的影响

在优选一株优良的耐低温面包酵母菌种的基础上,对冷冻面团配方进行了研究。结果表明,面筋含量高的面粉适于制作冷冻面团,配方宜采用 (以面粉为基准 )：蔗糖 10％～ 15％、鲜酵母 4％、盐 0.5％、水 55％～ 60％、起酥油 3％、蛋黄 5％、法国添加剂 0.5％。     

提高冷冻面包面团稳定性的研究

阐述了冷冻面包面团的生产工艺，并通过测定面团醒发时间和面包比容，研究了影响冷冻面包贮藏稳定性的因素，结果表明：适当的面团配方和工艺条件能有效地提高冷冻面团的稳定性。     

冷冻面团发酵特性的研究

以小麦高筋粉为原料,采用预发酵、未发酵、二次发酵3种发酵方式制作冷冻面团,研究不同发酵方式对冷冻面团理化特性的影响。结果表明,发酵方式影响了水的流动性和半结合水的含量,3种面团相比较,二次发酵面团相对较软,预发酵面团相对较硬;不同的发酵方式对于其面团内的面筋网络和酵母细胞的破坏有显著影响。     

冷冻面包面团的稳定性研究

制备冷冻面团时添加不同的添加剂,研究这些添加剂对冷冻面包面团品质的影响。结果表明,单独添加适量的溴酸钾或二乙酰酒石酸单双甘油酯,对制成面包的比容和柔软度均有一定的改善效果;以溴酸钾、二乙酰酒石酸单双甘油酯、活性面筋、魔芋精粉为正交试验的四个因素,每个因素设定三个水平,进行正交试验,当添加量分别为:溴酸钾30mg/kg、二乙酰酒石酸单双甘油酯0.3%、活性面筋3.0%、魔芋精粉0.1%时,冷冻面团的稳定性显著提高。     

冷冻面包面团的稳定性研究

制备冷冻面团时添加不同的添加剂,研究这些添加剂对冷冻面包面团品质的影响。结果表明,单独添加适量的溴酸钾或二乙酰酒石酸单双甘油酯,对制成面包的比容和柔软度均有一定的改善效果;以溴酸钾、二乙酰酒石酸单双甘油酯、活性面筋、魔芋精粉为正交试验的四个因素,每个因素设定三个水平,进行正交试验,当添加量分别为:溴酸钾30mg/kg、二乙酰酒石酸单双甘油酯0.3%、活性面筋3.0%、魔芋精粉0.1%时,冷冻面团的稳定性显著提高。      

食品添加剂对面团动态流变学及冷冻面团烘焙特性的影响研究

应用动态流变仪，研究了食品添加剂硬脂酰-2-乳酸钠（SSL）、刺槐豆胶（LBG）、葡萄糖氧化酶（GOD）、木聚糖酶（XY）及葡萄糖氧化酶和木聚糖酶（GOD＋XY）复合对面团动态流变学特性以及对冷冻面团烘焙特性的影响。结果表明，在频率0．1～40Hz扫描过程中，与未添加任何添加剂的面团相比，添加SSL的面团弹性模量、粘性模量和损耗角正切都减小；添加LBG的面团弹性模量和粘性模量增大．损耗角正切减小；添加GOD的面团弹性模量增大．粘性模量和损耗角正切减小；含有XY的面团弹性模量和粘性模量减小，损耗角正切增大；而含有GOD＋XY的面团弹性模量和粘性模量增大，损耗角正切减小。     

冷冻面团的研究与发展

冷冻面团是面包生产的一种新工艺,本文对冷冻面团开发的背景、现状和主要技术问题作了简要的介绍,探讨了酵母耐冷冻性的研究。可通过两种途径提高酵母的耐冷冻性：一方面利用改良剂来保护酵母细胞;另一方面通过生物技术培养发酵良好的耐冻藏酵母,最后对我国冷冻面团的发展前景作了展望。     

响应面法研究冷冻甜面团的流变发酵特性

本文主要采用F3肖邦流变发酵仪研究了海藻糖、起酥油、食盐、面团温度和乳酸对冷冻甜面团的发酵特性(Hm、Hm’、CO2产气量)的影响作用。结果表明,起酥油和海藻糖对Hm’和CO2产气量的影响效果是高度显著的,而食盐、面团温度和海藻糖对Hm的影响作用比较大。应用响应面分析法建立了描述各因素与响应值之间关系的模型。所有回归模型与测定数据(p<0.05)显示出良好的相关性,Hm、Hm’、CO2产气量和面包比容的R2值分别为93.67%、98.37%、98.12%和91.43%,表明响应面法可以作为推测研究海藻糖、起酥油、食盐、面团温度和乳酸各因素以及它们之间交互作用对冷冻甜面团发酵特性影响效果的适宜方法。     

Influence of yeast and frozen storage on rheological, structural and microbial quality of frozen sweet dough

The aim of the present study was to investigate the effect of yeast content and frozen storage (9 weeks at −40 °C) on the structural and rheological parameters, and fermentative activity of frozen sweet dough. Two types of dough were studied (to estimate dough shelf life): simple yeasted dough (SY) and double yeasted dough (DY). Fermentative activity (yeast viability, gassing power, and dough volume), rheological and textural parameters were assessed for frozen sweet doughs.These effects were explored by different and complementary methods: Fourier transform infrared (FTIR), dynamic rheology, texture profile analysis (TPA) and differential scanning calorimetry (DSC).The data showed that the longer the frozen storage time at −40 °C, the higher the decreased of frozen sweet dough quality. The rheological attributes such as hardness, ΔS, springiness, tan δ and yeast activity declined significantly during frozen storage. This modification led to lower specific volume of frozen sweet dough during proofing.The observed changes of the frozen sweet doughs rheological properties after thawing may be attributed to the damage on the gluten cross-linking, mainly produced by the ice crystallization during frozen storage. The storage effect was particularly concentrated in the first 27 days of storage.     

冷冻面团品质改良综述

较系统地介绍了国内外冷冻面团的研究开发现状,综述了常用添加剂(乳化剂、酶制剂、氧化剂、磷酸盐类、糖类等)对冷冻面团的品质的影响,并对我国冷冻面团的发展前景进行了展望。      

冷冻生坯面制品品质劣变及改良剂的研究进展

冷冻生坯在具有便捷、易于生产等优点的同时,也存在着内部结构发生劣变的可能。市场上常用的改良剂包括抗冻多糖、抗冻蛋白、亲水胶体、变性淀粉、酶制剂和乳化剂等。它们通过各自的作用方式来保护面筋蛋白不被破坏并提高酵母活性,从而抑制品质劣变,提高冷冻生坯的质地和感官。本文讨论了冷冻生坯品质劣变的几种可能的机制以及各种改良剂的作用机理和研究进展,总结了冷冻生坯的劣变机制与各种改良剂的作用方式之间的关系,以期为冷冻生坯面制品的工业发展提供参考。     

冷冻面团制作的面包在储存期间风味的变化

在冷冻甜面团的研究开发中,通过感官评价小组采用描述性分析对面包样品的风味剖析,同时采用固相微萃取(SPME)技术分别提取样品中的挥发性风味物质,并经气相色谱-质谱(GC-MS)联用法进行鉴定,重点研究了冷冻甜面团在不同冷冻储存阶段所制作的面包的风味变化问题。结果发现,用冷冻甜面团制作的面包与相同配方制得的新鲜面包相比,在冷冻期间21～28d内,烘焙风味的劣化即呈现出来并急速降级,如酸含量明显升高,醇类明显降低,醛类相对较高,酯类、呋喃类有所升高但芳香族化合物却较低,并在长达70d的冷冻储存期间趋于不可逆转的稳定状态。     

Weight loss of frozen bread dough under isothermal and fluctuating temperature storage conditions

Evaporative weight loss from food leads to both loss of saleable weight and quality deterioration so it need to be minimized. The effect of isothermal and fluctuating conditions on frozen dough weight loss was measured and compared with kinetic, physical and artificial neural network (ANN) models. Frozen dough samples were regularly weighed during storage for up to 112 days in loose-fitting plastic bags. The storage temperatures were in the range of −8 to −25 °C with fluctuations of ±0.1 °C (isothermal), ±1, ±3 or ±5 °C about the mean. For each combination of temperature and fluctuation amplitude, the rate of dough weight loss was constant. The rate of weight loss at constant temperature was nearly proportional to water vapour pressure consistent with standard theories for evaporative weight loss from packaged foods but was also accurately fitted by Arrhenius kinetics. Weight loss increased with amplitude of temperature fluctuations. The increase could not be fully explained by either the physic model based on water vapour pressure differences or the kinetic model alone. An ANN model with six neurons in the input layer, six neurons in hidden layers and one neuron in the output layer, achieved a good fit between experimental and predicted data for all trials. However, the ANN model may not be accurate for product, packaging and storage systems different to that studied.     

Improving freeze tolerance of yeast and dough properties for enhancing frozen dough quality - A review of effective methods

BackgroundFrozen dough technology could effectively extend the shelf life of bread to ensure the freshness, which is widely used and gradually replace the traditional bread production. However, during the production and storage of frozen dough, a series of problems could take place, such as inhibition of yeast activity, damage of the structure of the dough, leading to the deterioration of dough quality.Scope and approachThis review summarizes the factors that affect the final quality of frozen dough, including yeast activity, dough structure and dough properties. Some effective methods for improving freeze tolerance of yeast, dough structure and dough properties are discussed, including addition of various additives, use of genetic engineering technique, optimization of freezing and storage conditions, and employment of novel freezing technology.Key findings and conclusionsThe addition of additives can not only improve the freeze tolerance of yeast but also maintain the rheological and thermophysical properties of dough. Through the modification of gene, freeze tolerance and fermentation ability of yeast can be improved. Optimizing freezing and storage conditions ensures the activity of yeast as well as dough network structure so that freezing damage due to ice crystals can be minimized. In addition, novel freezing technology such as ultrasound-assisted freezing can simultaneously accelerate the freezing process as well as generate fine and uniform ice crystals, thus protecting dough network structure.     

Bread quality of frozen dough substituted with modified tapioca starches

Rheological properties of dough and bread quality of frozen dough-bread containing 18.4% of hydroxypropylated (HTS), acetylated (ATS), and phosphorylated cross-linked (PTS) tapioca starch with different degrees of modification and 1.6% of dried powdered gluten were compared to the same amount of native tapioca starch (NTS) or wheat flour-bread. Doughs substituted with native or modified tapioca starches had the same mixing tolerance as 100% wheat flour. The dough was frozen and stored for 1 week at −18°C, and thawed (one freeze-cycle). The amount of freezable water in the dough substituted with native or modified tapioca starches was not significantly different from that of wheat flour. Frozen dough-bread substituted with highly modified HTS (degree of substitution; DS 0.09–0.11) retarded bread staling, while lowly modified HTS (DS 0.06–0.07) or ATS (DS 0.02–0.04), and PTS (0.004–0.020% phosphoryl content) substitution fastened bread staling as compared with frozen dough-bread baked from wheat flour. The breadcrumbs containing HTS and ATS felt tacky, whereas the bread containing PTS was dry feel. HTS and ATS swelled and collapsed easily during heating, while PTS was difficult to swell and disperse as compared with NTS, therefore the gelatinization properties seemed to affect the texture of bread. Breadcrumb containing HTS showed small firmness during storage, and highly modified HTS-h (DS 0.1) was the smallest. This means highly hydroxypropylated tapioca starch significantly retards bread staling. Staling properties and texture of frozen dough-bread with various tapioca starches were the same as conventional bread baked with the same amount of tapioca starches. These results suggest that a one freeze–thaw cycle and a 1-week frozen period do not change characteristics of starch, gelatinization and retrogradation properties as compared with the conventional method, and the highly modified HTS-h is prominent anti-staling food-stuff in frozen dough.     

Combined effects of freezing rate, storage temperature and time on bread dough and baking properties

This study compares the effects of freezing temperature and rate as well as storage temperature and time on the quality of frozen dough. Yeasted bread dough was frozen using four freezing rates (19-69 °C/h), then stored at −10, −20, −30, or −35 °C for up to 180 days. Dough strength diminished with longer storage time and higher storage temperatures. Cryo-SEM showed that dough stored at −30 and −35 °C had the least damaged gluten network. NMR studies showed that more rapidly frozen dough, and that stored at lower temperatures had lower transverse relaxation (T₂) times (9-10 ms). However, dough stored at −20 °C displayed the highest yeast activity among samples. Bread loaf volume decreased with storage time, and bread made from dough stored at −20 °C showed the highest loaf volume. Breads produced from −30 and −35 °C stored dough displayed less change in the texture profile during storage as well as less change in T₂ values. Response surface analysis showed that optimal properties occurred at freezing rates of around 19-41 °C/h and storage temperatures of −15 to −20 °C.     

面团的玻璃化储存

由于面团在冷冻储存过程中受到结晶与再结晶的影响,产生结构松弛和水份迁移,品质显著下降。实现面团的玻璃化储存是解决问题的最佳方案。通过加入合适添加剂,可提高面团玻璃化转变温度,实现一般冷冻储存温度（-18℃）下的面团玻璃化储存。分析了各种玻璃化转变温度测定方法和添加剂在提高面团玻璃化转变方面的应用。