玉米中蛋白质对赖氨酸生产的影响

以玉米为原料生产赖氨酸成本较低，但是玉米中蛋白质含量较高，对赖氨酸生产过程中的糖化和发酵两个工序影响比较大。对糖化影响主要反映在滤饼的过滤和糖转化率；对发酵的影响主要为蛋白质产生胶体溶液和泡沫使发酵溶液供氧不足，影响茵种的成长。     

传统酸粥发酵过程中营养成分及风味的变化规律

该研究通过理化指标测定,电子舌和电子鼻分析对酸粥发酵过程进中的营养及风味行了考察,并对各指标和感官结果进行了相关分析。结果显示,发酵过程中pH和总糖含量随发酵的进行逐渐降低,总酸含量和蛋白质含量随发酵进行逐渐增加,脂肪含量基本保持不变,发酵过程中8种维生素含量随发酵的进行而增加,最高含量分别为烟酰胺23. 51μg/mL(24 h)、VB63.57μg/mL(24 h)、VB559.99μg/mL(18 h)、VB12190. 14μg/mL(30 h)、VC78. 15μg/mL(30 h)、叶酸546. 30μg/mL(18 h)、VB281.63μg/mL(30 h)和生物素1 132. 67μg/mL(24 h)。电子舌分析结果显示,随着发酵进行咸味(saltness)和鲜味(umami)值逐渐降低,酸味(sourness)和涩味(astringency)值逐渐加大。发酵过程中电子鼻的2号传感器W5S(氮氧化合物)值逐渐上升,6号传感器W1S(烷类)值逐渐下降。各成分间含量的相关性分析表明,发酵过程中pH、总酸与大部分营养成分及风味信号之间存在显著相关性(P<0. 05)...     

草莓酵素发酵过程中氨基酸成分分析和蛋白质营养评价

为研究不同发酵时间草莓酵素发酵液中的蛋白质、氨基酸和非蛋白质氨基酸γ-氨基丁酸(γ-aminobutyric acid,GABA)含量及营养价值,利用氨基酸自动分析仪对草莓酵素发酵过程中的氨基酸含量进行分析,通过氨基酸评分标准评价其蛋白质营养成分,通过与WHO/FAO推荐的人体必需氨基酸模式进行对比,并利用氨基酸含量阀值评价发酵过程中不同风味氨基酸对发酵液口感贡献。结果得出:在草莓酵素发酵过程中,蛋白质含量在发酵前期明显增加,经小幅度下降后再缓慢增加;总氨基酸含量有明显上升,其中氨基酸含量最高的是天冬氨酸(Asp)和谷氨酸(Glu),在检测限范围内未检出甲硫氨酸(Met)、苯丙氨酸(Phe)和组氨酸(His);利用聚类分析可将不同发酵时间的草莓酵素氨基酸发酵液分为四类;比值系数分在发酵前期波动较大,后期有缓慢上升。不同时间发酵液中除Met外其它8种必需氨基酸得分均大于1,属较严重的营养过剩。除发酵前30 d外,SRC值均大于55%,在整个发酵过程营养价值由高到低依次是:155 d > 140 d > 110 d > 30 d > 75 d > 50 d;发酵过程中只有Asp和Glu两种鲜味氨基酸的含量阀值比大于1,其它风味氨基酸对草莓酵素风味的影响不明显。经过155 d的发酵,草莓酵素中蛋白质和氨基酸含量有所提高,其中必需氨基酸含量显著上升(p<0.05),草莓酵素营养丰富,适当的延长发酵时间,蛋白质营养均衡度也将有所提高。     

发酵玉米面条的制备及其营养成分分析

以玉米面为原料,通过研磨、酵母发酵、成型、熟化等工艺,制成具有可口酸味的玉米面条。这种方法具有发酵周期短、加工工艺简捷等优点。此外还测定了产品中蛋白质和VB6含量。     

浓香型白酒窖池微生物生态因子的动力学分析

利用浓香型白酒酿造行业中的理化指标检验方法,监控窖池发酵过程中不同空间位置和不同发酵时间糟醅的生态因子伴随微生物活动而发生的动态变化.结果表明,温度在主发酵期逐渐上升至33℃左右,维持15d左右开始逐渐下降;与入窖时相比,酸度在发酵过程中总体呈上升趋势,其中中层粮糟的增幅达59.4%;总糖在发酵过程中总的呈下降趋势,而还原糖呈波动式下降;在0d～21d期间,乙醇大量积累,达入窖水平的21倍.后期乙醇含量呈波动式变化,下层底糟的下降最为明显.发酵过程中,上层、中层糟醅含水量总体呈下降趋势;发酵过程中,同一层面糟醅样的蛋白质含量变化几乎一致.在21d～50d,蛋白质消耗最大.但在50d以后,各层蛋白质含量又有比较大的上升.     

玉米中蛋白质对赖氨酸生产的影响

以玉米为原料生产赖氨酸成本较低,但是玉米中蛋白质含量较高,对赖氨酸生产过程中的糖化和发酵两个工序影响比较大。对糖化影响主要反映在滤饼的过滤和糖转化率;对发酵的影响主要为蛋白质产生胶体溶液和泡沫使发酵溶液供氧不足,影响菌种的成长。     

乳酸菌发酵促进小麦胚芽累积γ-氨基丁酸条件的研究

以纸层析法测定发酵液中γ-氨基丁酸含量,考察了发酵时间、温度、初始p H、缓冲体系以及磷酸吡哆醛和VB6对植物乳杆菌(Lactobacillus plantarum)DY-1发酵脱脂小麦胚芽累积γ-氨基丁酸的影响。在单因素实验基础上,利用正交实验设计优化了γ-氨基丁酸累积的发酵条件。研究结果表明,发酵时间对γ-氨基丁酸的累积有显著影响,γ-氨基丁酸累积的最适条件为发酵时间24 h,起始p H 5.0、VB6浓度0.2 mmol/L,在此条件下利用纸层析法测得发酵液中γ-氨基丁酸含量为0.954 mg/m L,进一步利用氨基酸分析得到γ-氨基丁酸含量为0.402mg/m L。经乳酸菌发酵后,麦胚中γ-氨基丁酸含量提高了3.4倍。     

腐乳生产技术(七)

6　腐乳前期发酵6 .1　发酵机理在酿造腐乳过程中 ,有物理化学和生物化学变化 ,整个过程又分为前期发酵和后期发酵两个阶段。前期发酵 (亦称发花 ) ,主要是将毛霉菌 (或根霉菌 )接种于豆腐坯上 ,让其在蛋白质 (豆腐坯 )培养基上充分繁殖 ,使豆腐坯表面生成一层白色细柔的菌膜 ,同时分泌大量蛋白酶 ,便于后期发酵使蛋白质缓慢水解。在前期菌丝生长阶段 ,豆腐坯的蛋白质已开始被蛋白酶水解为水溶性蛋白质(胚和胨 )。豆腐坯的水溶性蛋白质含量为3.6 1 %、而通过前期发酵后的水溶性蛋白质含量达 55.54%。前期发酵主要是培养毛霉菌过程 ,其目的归…     

生米发酵食品的研究进展

生米发酵食品是一种重要的米制品种类,在我国具有悠久的发展历史。本文阐述了几种生米发酵食品的特点及大米在发酵过程中的微生物的变化情况及发酵对化学组成和理化性质的影响。发酵过程中微生物对大米中的物质进行降解,形成发酵制品的特殊风味,其中优势菌种为乳酸菌。发酵后淀粉的含量有所增加,脂肪、蛋白质和灰分的含量逐渐减少,但游离脂肪酸的含量增加。发酵有利于淀粉的糊化,较大地改变了大米制品的质地。随着对发酵米制品的制作机理的深入研究,生米发酵制品在食品工业中的应用将越来越广泛。     

不同炒制程度糊米水发酵对雪茄烟叶化学成分和香味品质的影响

为明确不同炒制程度糊米水特色发酵工艺对雪茄烟叶化学成分和香味品质的影响，以什烟1号和德雪1号雪茄烟叶为材料，以清水发酵为对照，根据大米炒制时间不同，设置炒制7、10和13min 3个不同炒制程度的糊米水发酵处理，分析发酵过程中烟叶的常规化学成分、中性香气成分含量（质量分数）及感官质量的变化。结果表明：(1)糊米水处理后，烟叶中的总糖、还原糖及淀粉含量明显升高，随发酵的进行，总糖、还原糖及淀粉含量逐渐降低；总氮和烟碱含量在发酵过程中逐渐降低，且随糊米炒制程度的提高，下降幅度增大；蛋白质含量在发酵过程中逐渐降低。对照烟叶总糖、还原糖、淀粉、总氮及烟碱含量在发酵过程中缓慢降低，蛋白质变化规律与糊米水处理相同。(2)烟叶发酵过程中，中性香气成分含量呈现出不同的变化趋势。与发酵前及对照相比，糊米水发酵后除新植二烯含量显著降低以外，其他香气成分总量显著升高。其中，炒制10 min的糊米水发酵处理烟叶中的中性香气物质总量高于炒制7 min和13 min的处理。(3)糊米水发酵后的烟叶感官质量与发酵前及对照组烟叶相比明显提高，香气质好，甜润感提高，刺激性和杂气降低，劲头减弱，醇和度增加，其中以炒制10...     

Effect of baked wheat germ on gluten protein network in steamed bread dough

The effect of baked wheat germ (BWG) on the gluten network structure in steam bread dough was investigated. The secondary structure, free sulphydryl (-SH) content, disulphide (-SS-) bonds content and microstructure of gluten were analysed to evaluate gluten structural changes. The addition of different amounts of BWG (0, 2, 4, 6, 8, 10, and 12%) in dough resulted in decreased content of α-helix and β-sheet structures, but increased random coils, which indicated that a disordered structure was formed. The presence of BWG increased the -SH content but decreased the -SS- bonds content, which indicated fracture of disulfide bonds. Confocal laser scanning microscopy (CLSM) analysis indicated that steamed bread dough containing BWG had larger-sized gas cell and granules of starch separated by the protein matrix, which weakened the gluten network structure. These changes may inevitably affect the viscoelastic properties of steamed bread dough.     

Effect of Flour Extraction Rate and Baking on Thiamine and Riboflavin Content and Antioxidant Capacity of Traditional Rye Bread

ABSTRACT:  The effect of rye flour extraction rates and baking on thiamine and riboflavin content, and antioxidant capacity of traditional rye bread were studied and compared with white wheat flour. The content of thiamine was higher (10.9%) in rye dough formulated with dark rye flour (F-100%; extraction rate of 100%) than in rye dough formulated with brown rye flour (F-92%; extraction rate of 92%) that was similar to dough made with wheat flour. The riboflavin content in rye dough made from flour F-100% was also higher (16%) than in dough formulated with flour F-92%, and both provided larger riboflavin content than wheat dough. Baking led to reductions in thiamine of 56% for wheat bread and of 20% for both rye breads; however, this process caused only a 10% decrease in riboflavin for wheat bread and a 30% decrease for rye breads. Trolox equivalent antioxidant capacity, peroxyl radical scavenging capacity, DPPH radical scavenging activity, and Folin–Ciocalteu reducing capacity were higher in rye than in wheat dough and bread. Baking process produced slight changes in antioxidant activity, except for Superoxide Dismutase-like activity where a sharp decrease was observed. Our findings showed that rye breads are an important source of B vitamins and rye breads formulated with dark and brown flours showed better antioxidant properties than wheat bread. Therefore, rye breads should be more widely recommended in human nutrition.     

双波长分光光度法测定维生素B_(12)在糖液中的稳定性

采用双波长分光光度法,排除羟钴胺素干扰,测定维生素B12在糖液中的含量变化,测定主波长为356.0nm,参比波长为344.7 nm,平均回收率为101.71%,RSD为4.41%(n=6);结果表明,加糖后维生素B12在日光灯照射存放3 d过程中有不同程度的降解,其中低聚半乳糖、低聚异麦芽糖和麦芽糖变化最为明显,而在避光存放过程中均无明显降解;随着蔗糖浓度增加,维生素B12降解程度呈现先升后降的趋势.     

云南6种食用菌中维生素B1和B2的含量调查

目的 调查分析云南省6种食用菌中维生素B1和B2的含量。方法 定点采集云南省6种常见新鲜食用菌, 按GB 5009.84-2016《食品安全国家标准 食品中维生素B1的测定》和GB 5009.85-2016《食品安全国家标准 食品中维生素B2的测定》, 用高效液相色谱法测定样品中的维生素B1和B2的含量。结果 6种常见新鲜食用菌中维生素B1的含量平均值最高的是虎掌菌0.0812 mg/100 g, 最低的是干巴菌为0.0298 mg/100 g; 维生素B2含量平均值最高的是干巴菌为0.587 mg/100 g, 平均值最低的是人工种植的羊肚菌为0.0510 mg/100 g。 结论 人工种植和野生的食用菌均含有一定量的维生素B1和B2, 具有一定的营养价值。     

Identification of Baking Expansion Phases of Leavened Dough Using an Experimental Approach

A measurement system was designed to study changes in the volume, pressure, and viscosity of dough leavened by baking powder during model baking. Analysis of the volume changes demonstrated two baking stages, i.e. dough expansion and crumb shrinking. Through the analysis of pressure and viscosity extremes, the expansion stage was divided into five phases: stress relaxation (R) characterised by a mild pressure decline; gluten matrix softening (S), during which the decrease in viscosity is accompanied by a gradual pressure rise contributing to substantial dough expansion (by ～54 %); starch gelatinisation and protein aggregation (G) characterised by rapidly increasing viscosity; gas bubble opening (O) reflecting a rapid pressure reduction; and boiling of water in dough (B), which ends at initiation of crumb shrinking. The study showed that enrichment of the dough with carob fibre increased the contribution of phases S and O to dough expansion at the cost of phase G. A similar contribution of the expansion phases was reported for the Bombona cultivar, which exhibits the highest gluten content. In contrast, the Finezja and Katoda cultivars, which have a lower gluten level, were characterised by an approximately two-fold higher impact of phase G on the increase in dough expansion. The results indicated that the developed method for identification of baking expansion phases of leavened dough can be useful in baking characteristics of raw materials and bakery additives.     

Effects of dough mixing and oxidising improvers on free reduced and free oxidised glutathione and protein-glutathione mixed disulphides of wheat flour

Changes in free reduced glutathione (GSH), free oxidised glutathione (GSSG) and protein-glutathione mixed disulphides (PSSG) during dough mixing were monitored. After a rapid decrease in the GSH content and an increase in the GSSG content, the contents of both GSH and GSSG decreased progressively, whereas the PSSG content increased, as a simple flour-water dough was mixed. Total glutathione (GSH plus GSSG plus PSSG) levels in simple flour-water doughs and doughs treated with ascorbic acid or potassium bromate remained essentially constant during dough mixing, indicating that the reactions in which glutathione is involved are simple oxidations of sulphydryl (SH) groups to disulphide (SS) bonds and SH/SS interchange reactions. Yeast contributed high levels of GSH and GSSG to doughs, but analysis of dough aqueous phases (liquors) and the similarity of the PSSG contents of simple and yeasted flour-water doughs suggested that the yeast GSH and GSSG were largely unavailable to react with flour proteins. The GSH content of ascorbic-acid-treated and yeasted dough decreased rapidly on wetting the flour, the magnitude of the decrease indicating that the ascorbate oxidation system oxidised the yeast intracellular GSH as well as the flour GSH. With further mixing, the GSH content of the ascorbate dough remained constant at low levels similar to those of the simple flour-water dough. The GSSG content of the ascorbate dough increased rapidly on wetting the flour, but declined as dough mixing continued. The PSSG content of the doughs increased markedly as dough mixing proceeded to the optimum and then stabilised. The increase in the PSSG content lagged behind the rapid oxidation of GSH to GSSG. Potassium bromate caused a pattern of changes similar to those observed for ascorbate, but the changes in GSH and PSSG contents were smaller in magnitude. The results indicate that the changes in the different glutathione pools and the effects of oxidising bread improvers are rather more complex than envisaged previously, particularly the effects on PSSG.     

双波长分光光度法测定维生素B12在糖液中的稳定性

采用双波长分光光度法,排除羟钴胺素干扰,测定维生素B12在糖液中的含量变化,测定主波长为356．0nm,参比波长为344．7Bin,平均回收率为101．71％,RSD为4．41％（n=6）;结果表明,加糖后维生素B12在日光灯照射存放3d过程中有不同程度的降解,其中低聚半乳糖、低聚异麦芽糖和麦芽糖变化最为明显,而在避光存放过程中均无明显降解;随着蔗糖浓度增加,维生素B12降解程度呈现先升后降的趋势。     

Effect of glucose levels on the rheo-fermentation properties of dough during fermentation

In this study, recombinant dough and simulated dough medium were used to study the effect of different glucose levels on quality of dough. With the increase of glucose levels (3, 6, 9, 12 and 15 g/100 g mixed flour) in recombinant dough, the water absorption and extensibility of the dough decreased significantly. Compared with the sugar-free medium, the maximum height of the dough added with glucose gradually increased, and the CO₂ retention rate decreased slightly. The glucose levels in the dough changed the water mobility and distribution. Compared with 3% glucose levels, yeast produced much more glycerol content and ethanol content in 6% and 15% glucose medium, which affected rheological properties of dough. Different glucose levels affected the fermentation state of yeast and metabolites significantly, 3% glucose medium was more suitable for the dough fermentation and growth of yeast during dough fermentation.     

Effect of storage on the vitamin B6 activity of foods (author's transl)

In a study of the effect of storage on the vitamin B6 activity of foods, the vitamin B6 content of different foods of plant and animal origin and also of a mixed feed with added pyridoxine were analyzed microbiologically using Saccharomyces carlsbergensis as test organism. Vitamin B6 activity was determined initially, in some of the specimens after storage for 10 months and again in all foods after 40 months. The storage period of 10 months caused a loss of the natural vitamin B6 content of about 25--30%. This loss increased to more than 50% after 40 months storage. The diet containing the high level of synthetic pyridoxine lost 85% of its vitamin B6 content.     

抗冻蛋白对预发酵冷冻面团中蛋白质特性及水分状态的影响

采用Ellman’s试剂比色法、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳技术、傅里叶变换红外光谱技术以及核磁共振技术,研究冻藏和冻融循环条件下抗冻蛋白对冷冻面团的蛋白质特性以及水分子存在状态的影响。结果表明：经过冻藏和冻融循环,冷冻面团中游离巯基含量上升,二硫键含量下降。添加抗冻蛋白对冷冻面团亚基无影响。随着冻藏时间的延长,二级结构中分子间β-折叠含量增大,β-转角含量减小,而冻融循环使得α-螺旋结构含量下降,添加抗冻蛋白组的蛋白质特性变化均小于无添加组。无添加抗冻蛋白冷冻面团的失水率明显升高,驰豫时间随冻藏时间的延长逐渐变大,结合水含量减少,表明抗冻蛋白能够抑制二硫键的断裂和二级结构的变化,减少冰晶的重结晶,防止面团的水分散失,维持面团的持水能力。