加热过程对马铃薯淀粉糊流变特性的影响研究

为探讨马铃薯淀粉糊在加热过程中的流变特性,利用DV-I型旋转式黏度计对马铃薯淀粉糊进行流变性测定,并对其流变特性进行分析.结果表明:在讨论的加热温度范围内马铃薯淀粉糊是假塑性非牛顿流体,其流变特性服从幂律指数模型,随着加热温度的升高其稠度系数k减小,流变指数n基本上没有变化,随着浓度的增大其稠度系数k增大,流变指数n减小.     

超声波处理对全蛋液流变特性的影响

采用不同超声声能密度(0.4,0.8,1.2,1.6,2.0 W/g)及超声作用时间(0,5,10,15,20 min)对全蛋液进行处理,再用流变仪测其流变特性。试验结果表明,全蛋液是一种假塑性非牛顿流体,具有剪切稀化现象,其流变曲线在温度为0～40℃时服从Herschel-Bulkley模型。随着超声作用时间及声能密度的增大,全蛋液的流变特性指数增大,屈服应力及黏稠系数减小,流动性增加,全蛋液的非牛顿流体特性减弱,牛顿流体特性增强。动态流变试验结果表明,随着超声作用时间及声能密度的增大,全蛋液的损耗模量G"和贮能模量G'均减小,说明全蛋液的黏性特征和弹性特征均减弱,流动性增强,与静态流变试验结果一致。     

间位芳纶纤维悬浮液的屈服特性及其与成纸匀度关系的研究

为探究间位芳纶纤维悬浮液的絮凝特性,本研究从流变学角度出发,分别研究了单一间位芳纶短切纤维和间位芳纶沉析纤维悬浮液及两者共混悬浮液的絮凝浓度、剪切屈服应力和压缩屈服应力,同时通过湿法成形工艺探索间位芳纶纤维悬浮液的屈服流变特性与成纸匀度间的构效关系。结果表明,不同纤维配比间位芳纶纤维悬浮液的凝结点在0.37~0.68 g/L之间,悬浮液的压缩屈服应力和剪切屈服应力与纤维浓度间分别呈线性和指数函数关系;除100%短切纤维悬浮液外,在同一浓度下,间位芳纶纤维悬浮液的压缩屈服应力和剪切屈服应力均随着沉析纤维比例的增大而减小;间位芳纶纤维悬浮液Froude数随着浓度的增大而减小,对特定配比的间位芳纶纤维悬浮液,间位芳纶纸的匀度指数随着悬浮液Froude数的增大而增大。     

高浓度iota卡拉胶溶液的流变性能研究

本文研究了高浓度iota卡拉胶溶液的流变特性以及浓度、温度、转速和甘油等的影响。在实验条件范围内,结果显示:iota卡拉胶溶液粘度随浓度的增大而增加;粘度随温度的增大而减小;4%和60℃下3.5%的iota卡拉胶溶液具有剪切变稀现象,流变性能呈现假塑性,属于非牛顿流体,低于3.5%的iota卡拉胶溶液呈现牛顿流体特点;非牛顿态iota卡拉胶溶液具有复合触变性;甘油含量可以改变卡拉胶溶液的粘度。     

芋头浆的流变特性

研究不同质量分数芋头浆在不同温度下的流变学性质。静态流变性质测定结果表明：在研究的质量分数（10%～30%）和温度（0～80 ℃）范围内,芋头浆是具有假塑性的非牛顿流体,其流变特性服从Herschel-Bulkley模型;随着质量分数的增大,芋头浆的非牛顿性在逐渐增强,浆体的屈服应力和黏稠系数逐渐增大,流变特性指数逐渐减小;随着温度的升高,芋头浆的表观黏度不断降低,浆体的非牛顿性逐渐减弱,黏稠系数逐渐减小,流变特性指数逐渐增大,温度与芋头浆黏稠系数的关系可用Arrhenius方程进行拟合;动态流变性质测定结果表明：芋头浆显示弱凝胶特性。     

废纸浆纤维悬浮液屈服应力的主要影响因素研究

基于屈服应力的纸浆纤维悬浮液的流变特性直接影响造纸过程的能耗和生产效率。利用SPSS统计分析软件,对浓度为1.5%～4.0%的废箱纸板（OCC）和旧报纸（ONP）浆纤维悬浮液,分别采用流变曲线回归法（RCR）和剪切应力梯度法（SSG）测得的屈服应力进行方程回归,并与原生木浆的进行比较分析。结果表明,ONP浆和OCC浆纤维悬浮液的屈服应力τy与浆料浓度Cm的回归方程采用RCR法测定的结果分别为τy=3.34C2.43m、τy=2.33C2.57m,采用SSG法测定的结果分别为τy=3.58C2.43m、τy=2.83C2.47m;在相同浓度下采用相同测定方法时,ONP浆纤维悬浮液的屈服应力均大于OCC浆纤维悬浮液的;对于相同浓度的同种浆料纤维悬浮液,采用SSG法测得的屈服应力要比RCR法测得的大,对ONP浆纤维悬浮液而言,约大5.1%～9.4%,而对于OCC浆纤维悬浮液,约大1.3%～13.9%;且Δτy在2.7～17.2 Pa之间,两种方法测得的屈服应力值偏差随纸浆纤维悬浮液浓度的增大而逐渐增大,即随着废纸浆纤维悬浮液浓度和纤维长宽比的增大,屈服应力增大。漂白针叶木浆纤维悬浮液的屈服应力明显大于ONP浆、OCC浆和阔叶木浆纤维悬浮液的。     

玉米淀粉糊流变特性研究

利用AR–500流变仪,研究了不同质量浓度、温度和加热时间条件下玉米淀粉糊的流变特性。结果表明:玉米淀粉糊主要表现为假塑性非牛顿流体,流变特性服从Carreau模型。在同一剪切速率下,黏度随着质量浓度增大而增大,随着温度升高而降低,随着加热时间延长而下降;在同一质量分数条件下,黏度随着剪切速率的增加而呈现先增加后降低的趋势;在同一温度条件下,黏度随着剪切速率的增加而降低。     

小麦粉储藏期面团流变发酵特性的变化（网络首发、推荐阅读）

传统发酵面制品工业化生产过程中,小麦粉后熟期对馒头类发酵食品生产工艺及产品特性有明显的影响,常常造成质量波动。以自制的室内储藏小麦粉为样品,借助面团流变发酵仪等设备,定期分析面团流变发酵特性,以及馒头质量感官评价数据,确定合理的小麦粉后熟期。结果显示,小麦粉在储藏过程中,面团稳定时间增加,弱化度降低;流变学特性改善;发酵流变仪的发酵体积明显降低;蒸制馒头体积降低,但馒头感官评价数据的变化趋势不甚明显。F4流变发酵仪测试结果可以反映面团的流变发酵特性;其面团达到最大高度时所需时间（T1）、最大发酵高度（Hm）和发酵终点高度（h）等参数对馒头制作具有明显地指导意义。建议工业化制作馒头专用小麦粉的储藏期不低于7 d。     

CMC对漂白针叶木浆悬浮液屈服应力的影响及其应用

通过向漂白针叶木浆中添加CMC来改善纸浆悬浮液的流变特性,并对纸浆悬浮液的屈服应力进行了研究。结果表明,在稳态剪切条件下,纸浆悬浮液的屈服应力τy随浆浓Cm的增大而迅速增大,两者符合指数关系τy=aCbm,且添加CMC不影响两者的指数关系;对于浓度一定的纸浆悬浮液,随CMC添加量的增加,纸浆悬浮液的屈服应力先减小后增大,当添加相对绝干浆质量约1.5%的CMC时,纸浆悬浮液的屈服应力显著减小;随浆浓的增大,CMC对其屈服应力的影响也越来越显著,向浆浓为4%的漂白针叶木浆中添加1.5% CMC时,纸浆悬浮液的屈服应力下降最多,降低了16.2%,且纸浆的搅拌能耗明显降低,降低约40.6%;此外,添加CMC会降低纸浆初始流态化时的能量耗散因子εF,使得纸浆更易于输送。实验结果可为漂白针叶木浆的输送、筛选和混合等过程的工艺节能降耗和装备技术研发与优化提供理论依据。     

纤维悬浮液的数值模拟中粘度及轨道系数的研究

粘度是悬浮液的宏观流变特性，数字模拟的结果可以描述这种流变特性，TIF方程对稀释纤维悬浮液的流变特性有很好的描述，纤维轨道系数（Jeffery常数）可以描述纤维在微观模型中的物理状态，本文对纤维轨道系数（Jeffery常数）进行了推导，Jeffery常数的范围在Cj=0.45-1.15的轨道中移动。     

鹅肉发酵香肠生产工艺研究

目的:获得鹅肉发酵香肠的生产工艺及技术参数。方法:在鹅肉香肠的制作过程中,添加适当的发酵剂,利用正交试验对其生产工艺进行研究。结果:确定发酵剂为植物乳杆菌和啤酒酵母菌,菌悬液(La:Sa)体积比为2:3,得出最佳的鹅肉香肠制作工艺条件为发酵温度33℃、接种量2.0%、发酵时间36h。结论:该鹅肉发酵香肠的制作工艺条件稳定、可行。     

酵母浓度（生物量浓度）实时在线检测方法的研究

微生物的存在会改变发酵液的电物性,发酵液在无线电频率范围内的电特性可用电容率和电导率充分地描述。实验证实发酵液在无线电频率范围内的电容率增量是测量频率和生物量浓度的函数。基于对发酵液电容率分布的研究,本文提出了测量生物量浓度的新方法。此方法不用取样就能对发酵液中的生物量进行实时在线测量,而且测得的是活的酵母浓度。     

用电容率频谱法测量啤酒酵母的浓度和活性

酵母的存在会改变发酵液的电特性,发酵液在无线电频率范围内的电特性可用电容率和电导率充分地描述。实验证实发酵液在无线电频率范围内的电容率增量是测量频率和生物量浓度的函数。基于对发酵液电容率分布的研究,提出了测量酵母浓度的新方法。用本方法不用取样就能对发酵液中的酵母浓度进行实时在线测量,而且测得的是活的酵母浓度。本研究制作的的电极直接插入发酵器中并满足高温蒸汽灭菌条件。本方法在生化制药、食品发酵、啤酒酿造、污水检测等工业领域里有很好的推广应用前景     

啤酒酵母浓度实时在线检测方法的研究(一)

酵母的存在会改变发酵液的电特性,发酵液在无线电频率范围内的电特性可用电容率和电导率充分地描述。实验证实发酵液在无线电频率范围内的电容率增量是测量频率和生物量浓度的函数。基于对发酵液电容率分布的研究,本文提出了测量酵母浓度的新方法。用本方法不用取样就能对发酵液中的酵母浓度进行实时在线测量,而且测得的是活的酵母浓度。本文制作的电极直接插入 发酵器中并满足高温蒸汽 灭菌条件。本方法在生化制药、食品发酵、啤酒酿造、污水检测等工业领域里有很好的推广应用前景     

Cell wall fermentation kinetics are impacted more by lignin content and ferulate cross‐linking than by lignin composition

BACKGROUND: We used a biomimetic model system to ascertain how reductions in ferulate–lignin cross‐linking and shifts in lignin composition influence ruminal cell wall fermentation. Primary walls from maize cell suspensions with normal or reduced feruloylation were artificially lignified with various monolignols previously identified in normal, mutant, and transgenic plants. Cell wall fermentability was determined from gas production during in vitro incubation with rumen microflora and by analysis of non‐fermented polysaccharides. RESULTS: Hemicellulose fermentation lag time increased by 37%, rate decreased by 37%, and the extent declined by 18% as cell wall lignin content increased from 0.5 to 124 mg g^?1. Lignification increased lag time for cellulose fermentation by 12‐fold. Ferulate–lignin cross‐linking accounted for at least one‐half of the inhibitory effect of lignin on cell wall fermentation. Incorporating sinapyl p‐coumarate, a precursor of p‐coumaroylated grass lignin, increased the extent of hemicellulose fermentation by 5%. Polymerizing varying ratios of coniferyl and sinapyl alcohols or incorporating 5‐hydroxyconiferyl alcohol, coniferaldehyde, sinapyl acetate, or dihydroconiferyl alcohol into lignin did not alter the kinetics of cell wall fermentation. CONCLUSION: The results indicate that selection or engineering of plants for reduced lignification or ferulate–lignin cross‐linking will improve fiber fermentability more than current approaches for shifting lignin composition. Copyright © 2008 Society of Chemical Industry     

微滤膜偶联生物反应器制备泡菜发酵剂

采用自主研发的微滤膜偶联生物反应器制备泡菜用液体发酵剂,直接用于泡菜发酵。研究表明,通过生物反应器可控制乳酸菌培养过程中的pH、温度、溶氧量和追加营养物质的时间,植物乳杆菌在生物反应器内恒定pH培养12 h后活菌数达到5～8×109 CFU/mL;选择中空纤维膜膜滤的操作条件为蠕动泵转速50 r/min,压力0.15 MPa,对菌悬液进行膜滤浓缩1 h可得到4 L活菌数为2～3×1010 CFU/mL的浓缩菌液。浓缩菌液稀释5 000倍作为泡菜用发酵剂,直接用于泡菜发酵。室温条件下发酵3 d得到优质泡菜,比自然发酵短2 d。此微滤膜偶联生物反应器结构简单、使用方便、自动化程度高、适用于工业化大规模连续生产泡菜发酵剂。     

Erratum

Cooking and processing of starch-containing foodstuffs results in a portion of the starch becoming resistant to hydrolytic enzymes secreted in the small intestine of man. In order to determine whether this resistant starch (RS) was degraded in the colon, samples of RS and readily digestible starch (RDS) for comparisons were incubated with (a) cell-free supernatants from faecal suspensions and (b) washed faecal bacterial cell suspensions. The data obtained showed that, whereas pancreatic amylase and faecal supernatants hydrolysed RDS, with the production of oligosaccharides, RS totally resisted breakdown. In contrast, both RS and RDS were completely degraded by the washed bacterial cells with the generation of volatile fatty acids (VFA) and organic acids. Hydrolysis and fermentation of RDS was extremely rapid and, as a consequence, oligosaccharides and lactate initially accumulated in the culture medium. RS was broken down more slowly, howevér, and oligosaccharides and lactate never accumulated. The rate of polysaccharide hydrolysis had a significant effect on the quantities of VFA produced, in that 54% of carbohydrate was fermented to VFA in cultures incubated with RDS as sole carbon source as compared to only 30% in cultures incubated with RS. However no qualitative difference was observed in the VFA produced by fermentation of RDS or RS.     

Production of potentially probiotic beverages using single and mixed cereal substrates fermented with lactic acid bacteria cultures

In the present work, single and mixed cereal substrates were fermented with lactic acid bacteria to study and compare the effect of the media formulation on fermentation parameters. Three cereal flours namely malt, barley and barley mixed with malt (barley–malt) were selected and fermented with two probiotic strains: Lactobacillus plantarum (NCIMB 8826) and Lactobacillus acidophilus (NCIMB 8821). The effect of the single and mixed cereal flour suspensions on the fermentation of these two strains of lactic acid bacteria (LAB) was studied at an incubation temperature of 30 °C for 28 h. It was found that the LAB growth was enhanced in media containing malt and significant amounts of lactic acid were produced (0.5–3.5 g/L). A cell concentration between 7.9 and 8.5 Log₁₀ CFU/mL and a pH below 4.0 was achieved within 6 h of fermentation. Though the cell populations in the mixed culture fermentations of mixed substrates were similar to the ones obtained with single cereal flours, significant differences in the production of lactic acid were observed. These results suggest that the functional and organoleptic properties of these cereal-based probiotic drinks could be considerably modified through changes in the substrate or inocula composition.     

Effect of ratio of roughage concentrate on glucose-induced heat production in sheep rumen fluid in vitro

The effect of ration on heat of glucose fermentation in sheep rumen fluid was investigated. Heat production was measured in a semiadiabatic calorimeter. In trial 1, the effect of glucose (.4 to 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25 or 100% roughage diet. Heat of glucose fermentation decreased with increase in glucose dose in both diets. Maximal heat of glucose fermentation in both diets agreed with stoichiometric calculations. However, at 6.4 mg glucose, maximal heat was 18 kcal/mol in the 25% roughage diet and 14 kcal/mol in the 100% roughage diet. Purine N and maximal rate of heat production were not affected by diet type. In trial 2, the effect of glucose (1.6 and 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25, 50, 75, and 100% roughage. In addition, fermentation pattern was measured in donors of the rumen fluid. Heat of glucose fermentation was positively correlated with organic matter digestibility and negatively correlated with rumen pH and acetate concentration. These observations indicate that in addition to the effect of roughage on the fermentation pattern, supplemental adaptation may occur, as indicated by the reduction in the heat of glucose fermentation.     

利用D-最优混料设计优化浓香型白酒生物发酵液的配方

以黄水澄清液、酒尾、尾水为主要原料,通过添加生物酶制剂和控制发酵条件得到己酸乙酯含量较高的浓香型白酒生物发酵液。利用D-最优混料设计试验,研究不同黄水澄清液、酒尾和尾水配比对生物发酵液己酸乙酯生成量的影响,建立了配比与生物发酵液中己酸乙酯含量之间的回归模型,探讨了配方中各原料的互作效应,获得了浓香型白酒生物发酵液的最佳配方为：黄水澄清液26.20%、酒尾36.34%、尾水37.46%。在此最佳条件下,生物发酵液己酸乙酯含量达16.32 g/L,总酸含量为152.30 mg/100 mL,总酯（以己酸乙酯计）含量为17.66 g/L。所得生物发酵液风味成分种类丰富,黄色清亮,具有典型的发酵液复合香味。