冷冻面团冷冻贮存和解冻的工艺

研究了冷冻面团在冷冻贮存和解冻过程中面团温度的变化 ,并选择了冷冻面团面包的最佳冷冻贮存和解冻的工艺条件 :面团 30℃、90 %～ 95%rh前发酵 2 0min ,成型后于- 2 0℃冷冻贮存 ;冷冻面团可在打开包装后 ,38℃ ,95%rh解冻 4 0min ,32℃ ,95%rh醒发 55min ,或用微波炉解冻档解冻 1min再打开包装 ,32℃ ,95%rh醒发 95min     

自带测量尺的饼干面团包装

正烘培市场新产品层出不穷,烘焙食品包装不仅要吸引消费者,还要方便消费者使用。图5所示的这款包装可以直接盛装烘培的饼干面团,且在烘培前可将饼干面团按照一定大小进行分切,这是因为包装设计师奇思妙想,在该包装表面设计了一个测量尺,消费者只需将饼干面团放在该测量尺旁边,就可以将其分切成大小合适的面团。此外,这款纸盒在外观上一改往常的标准长方体结构,而是设计成锥台型,不     

糯小麦粉对混合粉性质及面团冻融稳定性的影响

糯小麦粉中支链淀粉含量很高,糊化特性和冻融稳定性好,在食品加工中应用比较广泛。本文把糯小麦粉以0%、10%、20%和30%的比例添加到小麦粉中,研究不同比例糯小麦粉对混合粉性质及面团冻融稳定性的影响。结果表明,添加糯小麦粉后,混合粉的峰值粘度升高,回生值、糊化温度和焓值都降低;面团的吸水率从62.23%增加到64.57%,但稳定时间从9.80 min降低到5.70 min;DSC分析可知,糯小麦粉显著降低面团中可冻结水分含量。由SEM分析得出,糯小麦粉使面团在冻融过程中面筋结构变差,淀粉裸露在网络外面,这可能跟糯小麦粉本身蛋白面筋差有关系。通过对面团中巯基含量的测定分析可得,糯小麦粉的加入增加了面团在冻融过程中的巯基含量,使面团在经历冻融循环后二硫键断开。     

面筋蛋白对冷冻面团超微结构及馒头品质的影响

采用感官评价、质构分析和扫描电镜的方法,研究了面筋蛋白对冷冻面团及馒头品质的影响.结果显示,添加2％面筋蛋白能明显提高冷冻面团馒头的感官评分、比容,降低冷冻面团馒头的TPA硬度,提高TPA弹性;冷冻面团馒头品质明显劣化时间也从第2周延长至第4周.电镜实验证明,添加2％面筋蛋白的冷冻面团面筋网络抗冻能力明显优于未添加面筋蛋白(空白组)的面团;冻藏1周时,面筋蛋白添加组的面筋网络比空白组连续、清晰;冻藏4周时,面筋蛋白添加组还可观察到破碎的面筋网络,空白组几乎无法观察到面筋膜.     

冷藏面团生产工艺

冷藏面团是指将预先调制好的各种生面团置于一种特殊的包装容器中,在冷藏条件下可储藏1～3个月的方便主食产品,产品最大的特点就是:营养、卫生、方便.从冷藏面团产品配方、生产设备及工艺、微生物控制和包装形式等四个方面作了详细的介绍,为食品生产厂家提供了一种新型的方便主食生产技术.     

小麦粉吸水速率对面团特性及馒头品质的影响

该文以不同吸水速率的小麦粉为基础,研究在相同的揉混条件下,其面团特性及馒头品质的变化。使用粉质仪将面团稠度达到最高时所用的加水量与消耗的时间的比值定义为吸水速率,测定不同吸水速率小麦粉其粉质特性、湿面筋含量、面筋指数、游离巯基与二硫键含量、面团质构特性、馒头比容与高径比、馒头的质构特性。研究结果表明,当小麦粉吸水速率从0.17 g/s增大到3.87 g/s时,面团的稳定时间及粉质质量指数显著下降。其湿面筋含量从38.81%下降到19.19%,二硫键含量从13.31μmol/g下降到9.05μmol/g。面团的质构特性在发酵0 min时呈先升高后降低趋势、在醒发45 min后整体呈下降趋势。馒头的比容从2.67 mL/g降低到2.27 mL/g、高径比从0.68降低到0.56,其硬度、胶着性、咀嚼性均成下降趋势。整体而言,吸水速率低的小麦粉其面团相对较硬且馒头较为筋道有嚼劲;吸水速率较高的小麦粉其面团硬度稍弱且馒头较为松软。     

添加玉米醇溶蛋白对荞麦面团特性的影响

为探究玉米醇溶蛋白（Zein）对荞麦无麸质面团流变学特性的影响,将气流膨化苦荞粉与甜荞粉以1:1混合制得基料粉（以下称混粉）。用90%乙醇溶液对Zein进行增塑处理,然后按照0%、5%、10%、15%、20%的添加量（以混粉计）与混粉及水揉混制得荞麦无麸质面团（以下称面团）,并对面团静态流变学特性（质构特性、拉伸特性和应力松弛特性）、动态流变学特性、光学性质（色度和反光率）以及微观结构等进行测定。结果表明,随着Zein添加量从0%增加到20%,面团的硬度从482.38 g降低到346.60 g,弹性从0.21升高到0.29,拉伸距离从15.44 mm升高到38.16 mm,抗拉伸力从13.10 g升高到72.04 g。面团的残余应力、黏弹系数和松弛时间相对于对照组显著升高（P<0.05）,但随着Zein添加量的增加均逐渐减小,面团G’和tanδ值、面团表面亮度及反光率均得到明显改善,微观结构相比对照组能够明显地观察到蛋白纤维丝。以上结果充分表明,Zein可有效地改善荞麦无麸质面团结合力和延伸性差的缺陷。本研究为无麸质食品结构及加工特性改善提供了一个新的途径。     

类食品乳杆菌412对酸面团发酵的影响

从酸面团中分离得到1株类食品乳杆菌(Lactobacillus parali mentarius)412,添加该菌株的面团在28℃发酵4h后的pH为5.2,发酵24h后pH为3.5;而添加商业化安琪酵母发酵的面团在28℃发酵4h后的pH为5.9,发酵24h后pH为5.2。类食品乳杆菌412与安琪酵母(接种量为107CFU/g)联合发酵测定表明,若菌株412起始接种量为109CFU/g,则面团在28(C发酵24h后的滴定酸度为0.76%(滴定酸度以乳酸计,%为质量分数);若菌株412的起始接种量是108CFU/g或107CFU/g时,则面团在28℃发酵24h后的滴定酸度为0.57%。当向面团添加6.75g/kg的葡萄糖或蔗糖可以促进类食品乳杆菌412的生长。面团在28℃发酵12h后,添加葡萄糖可以使菌株412的细胞数量从起始的2×108CFU/g提高到2.5×1010CFU/g,添加蔗糖则可以使其细胞数量提高到2.6×1010CFU/g;而添加果糖的面团在28℃发酵12h,菌株412的细胞生物量仅3.8×108CFU/g。与25(C或32℃发酵条件相比,28℃下发酵的酸面团中类食品乳杆菌412和安琪酵母菌的活菌数都比较高,且面团酸化速率高于单独采用安琪酵母菌发酵的面团。结果证明,类食品乳杆菌412能够单独或与商业化的安琪酵母联合应用到酸面团发酵中,并对面团的酸化起到积极促进作用。     

胶原抗冻肽的制备及在冷冻面团中的应用

抗冻肽是一类通过抑制冰晶生长使生物有机体免受冰冻伤害的多肽。文中采用酶法制备了高热滞活性的胶原抗冻肽,并考察了该抗冻肽对冷冻面团酵母存活率、发酵时间、馒头比容、质构及感官评分的影响。结果表明:胶原抗冻肽显著改善了冷冻面团的品质,当其添加量为0.3%时,面团经21 d冻藏后,酵母存活率从43%增加到54.5%;醒发时间缩短了33.3%,为60 min;馒头比容从1.74 m L/g增加到2.11 m L/g,上升了27.1%;馒头的硬度和咀嚼性显著减小,其回弹性、黏性、弹性均增加;同时冷冻面团的外观较好,感官总分达到55.5分。     

速冻小笼包制作工艺条件及策略研究

<正>1.引言淮扬风味小笼包的制作工艺过程并不复杂,但要做好其品质还是需要有严格的工艺流程和工艺要求。一般工艺流程为调馅、和面、制皮、成型、速冻、包装、储藏、运输等,如图1所示。其中和面是制作小笼包的关键,面团质量对小笼包产品的口感和质量有重要影响,面团质量好,则蒸出来的小笼包口感和质量都会好一些;面团质量差,蒸出来的小笼包口感和质量就会差一些。做好和面、     

Interpreting results from field deployments of semipermeable membrane devices

Three canisters of semipermeable membrane devices (SPMDs), each containing five SPMDs, were deployed at three different locations on a transect across a small river removed from the impact of near-field point sources. Following a 62-day deployment, the masses of various polynuclear aromatic hydrocarbons (PAH) sequestered by each SPMD in each canister were determined. The compound-specific mean residues (ng/SPMD) obtained for the PAHs with pK(ow) values >4.4 showed statistically significant (alpha = 0.10) differences between the three deployment locations (canisters) ranging from approximately 10 to 160 ng/SPMD, corresponding to relative percent differences (RPDs) ranging from 10% to 54%. There were no statistically significant differences between the same three locations for the single PAH with a pK(ow) <4.4. A detailed discussion of how different (uncontrollable) environmental variables may have impacted the experimental results is provided to illustrate the uncertainties associated with interpreting the results from SPMD field deployments and highlight the need for some means of correcting for these impacts. The results from this work also illustrate the need to account for spatial variability in water column concentrations (i.e., sample heterogeneity) as part of any interpretation.     

Development of a flow controller for long-term sampling of gases and vapors using evacuated canisters

Anthropogenic activities contribute to the release of a wide variety of volatile organic compounds (VOC) into microenvironments. Developing and implementing new air sampling technologies that allow for the characterization of exposures to VOC can be useful for evaluating environmental and health concerns arising from such occurrences. A novel air sampler based on the use of a capillary flow controller connected to evacuated canisters (300 mL, 1 and 6 L) was designed and tested. The capillary tube, used to control the flow of air, is a variation on a sharp-edge orifice flow controller. It essentially controls the velocity of the fluid (air) as a function of the properties of the fluid, tube diameter and length. A model to predict flow rate in this dynamic system was developed. The mathematical model presented here was developed using the Hagen-Poiseuille equation and the ideal gas law to predict flow into the canisters used to sample for long periods of time. The Hagen-Poiseuille equation shows the relationship between flow rate, pressure gradient, capillary resistance, fluid viscosity, capillary length and diameter. The flow rates evaluated were extremely low, ranging from 0.05 to 1 mL min(-1). The model was compared with experimental results and was shown to overestimate the flow rate. Empirical equations were developed to more accurately predict flow for the 300 mL, 1 and 6 L canisters used for sampling periods ranging from several hours to one month. The theoretical and observed flow rates for different capillary geometries were evaluated. Each capillary flow controller geometry that was tested was found to generate very reproducible results, RSD < 2%. Also, the empirical formulas developed to predict flow rate given a specified diameter and capillary length were found to predict flow rate within 6% of the experimental data. The samplers were exposed to a variety of airborne vapors that allowed for comparison of the effectiveness of capillary flow controllers to sorbent samplers and to an online gas chromatograph. The capillary flow controller was found to exceed the performance of the sorbent samplers in this comparison.     

Development and validation of a canister method for measuring ethylene oxide in ambient air

A sampling and analytical method for measuring ethylene oxide (EO) in ambient air was developed and evaluated. The method is based on the use of evacuated canisters and gas chromatography-mass spectrometry (GC-MS). The objectives of this work were to characterize the performance of the method with respect to the following: (1) stability/recovery of ethylene oxide in a canister over a 15-day holding time; (2) detection capability; and (3) measurement of EO in an ambient air matrix. Both electropolished and silica-lined stainless steel canisters were evaluated in this study. The method evaluation involved both laboratory and field tests. The recovery of the EO was evaluated both on an absolute basis and relative to a spiked internal standard of toluene. EO spiked at levels of 2 ppbv and 20 ppbv was found to be stable for holding times of up to 15 days at 25 degrees C in both a humidified nitrogen matrix and in ambient air. The detection limit of the method was found to be 0.25 ppbv using EPA's traditional approach of seven replicate analyses of a low-level standard and 0.20 ppbv using a probability-based approach. EO recoveries in the laboratory stability study generally were 100 +/- 25%, and did not vary by canister type, nor did the EO recoveries decrease with holding time. Field studies demonstrated that the method is capable of detecting EO (as well as benzene and toluene) in an ambient air matrix.     

A field comparison of volatile organic compound measurements using passive organic vapor monitors and stainless steel canisters

Concurrent field measurements of 10 volatile organic compounds (VOCs) were made using passive diffusion-based organic vapor monitors (OVMs) and the U.S. Federal Reference Method, which comprises active monitoring with stainless steel canisters (CANs). Measurements were obtained throughout a range of weather conditions, repeatedly over the course of three seasons, and at three different locations in the Minneapolis/St. Paul metropolitan area. Ambient concentrations of most VOCs as measured by both methods were low compared to those of other large metropolitan areas. For some VOCs a considerable fraction of measurements was below the detection limit of one or both methods. The observed differences between the two methods were similar across measurement sites, seasons, and meteorological variables. A Bayesian analysis with uniform priors on the differences was applied, with accommodation of sometimes heavy censoring (nondetection) in either device. The resulting estimates of bias and standard deviation of the OVM relative to the CAN were computed by tertile of the canister-measured concentration. In general, OVM and CAN measurements were in the best agreement for benzene and other aromatic compounds with hydrocarbon additions (ethylbenzene, toluene, and xylenes). The two methods were not in such good agreement for styrene and halogenated compounds (carbon tetrachloride, p-dichlorobenzene, methylene chloride, and trichloroethylene). OVMs slightly overestimated benzene concentrations and carbon tetrachloride at low concentrations, but in all other cases where significant differences were found, OVMs underestimated relative to canisters. Our study indicates that the two methods are in agreement for some compounds, but not all. We provide data and interpretation on the relative performance of the two VOC measurement methods, which facilitates intercomparisons among studies.     

Changes in volatile production during an infection of potatoes by Erwinia carotovora

The monitoring of volatiles produced by diseased potatoes has been studied as a method of detecting infections in potato storage units. Previous studies attempted to identify pathogen-specific volatiles as markers for the presence of disease, however, consistent results were difficult to obtain. A possible solution is to consider overall qualitative and quantitative changes in the volatile profile over the course of an infection. The objective of this study was to investigate this method of data analysis. The study was done using 1-kg batches of potatoes stored at room temperature in metal canisters fitted with volatile traps containing Chromosorb 105. Either one or all of the potatoes in the batch were inoculated with Erwinia carotovora, the causative agent of soft rot. A canister containing uninoculated healthy potatoes was used as the control. A dynamic headspace sampling method was used to sample periodically the air for volatiles in the experimental and control canisters. The analysis of volatiles was done by gas chromatography. Comparison of the volatile profiles arranged in chronological order showed a progression over time, in the types and amounts of volatiles produced. A wider range of volatiles were produced by infected potatoes than by healthy potatoes. Differences between the volatile profiles of healthy and inoculated potatoes were observed as early as 24 h into the experiment while the total quantity of volatiles produced was initially low and increased exponentially as the infection became well established. The time difference between these two observations was 36–48 h and represented the time in which measures can be taken to contain the infection. The amount of volatile produced was dependent on the initial amount of bacteria, the growth of the bacteria and the detection limits of the Chromosorb and the gas chromatograph.     

Viscosity Measurements of Potato Starch Paste with the Rapid Visco Analyzer

Viscosity behaviour of potato starch paste was measured with the Rapid Visco Analyzer (RVA, Newport Scientific, Warriewood, Australia). By reason of high viscosity properties of potato starch suspensions, starch concentration was reduced from 3.0 to 2.0 g starch weight (14% moisture) in 25 ml distilled water. In view of Brabender viscograms a short temperature profile (13 min including heating, stable hot phase, and cooling) achieved the best results. Reproducibility of RVA-measurements was high as well with new canisters as with re-used ones. Coefficient of variation (s%) was below 2%. A comparison of RVA and Brabender viscograms pointed out a close correlation of r=0.94 for both, the peak viscosity and the viscosity difference between peak and trough.     

Automated sampler for the measurement of non-methane organic compounds

An automated sampler has been constructed for the unattended collection of whole-air samples in Summa passivated stainless steel canisters. The sampler consists of a Viton diaphragm pump; a differential-pressure flow controller; a 2-position, 3-port valve; a 10-port multiposition valve; and a digital valve sequence programmer that controls the sequence and timing of the electrically actuated valves. All connecting tubing was constructed from Silcosteel tubing. Two configurations of the automated sampler and a passive collection system were evaluated by comparing the combined sampling precisions of the three systems with the analytic precision, derived from replicate analyses of an ambient air sample. The analytic precision was generally < +/- 5%, with higher values observed for analytes with mixing ratios in the tens of pptv. However, analytic precision values for methanol and ethanol were poor, greater than +/- 20%. Values for sampling precision were greater by about a factor of 2 than the analytic precision. The poor results for the light oxygenated hydrocarbons could be caused by sorption of the analytes in the preconcentration and sampling systems and difficulties in peak integration.     

长丝短纤复合纱线强伸性能与加捻关系研究

涤棉复合纱线采用涤轮长丝和棉单纱复合加工而成，是一种生产细号轻薄型面料的优良纱线。复合纱线中各组分性能的差异对复合纱线与织物的性能将产生极大的影响。在复合纱线反向加捻的情况下，通过试验分析了复合纱线断裂强力、断裂伸长率与单纱捻度、复合纱线捻度之间的关系。复合纱线也存在着临界捻系数，复合纱线断裂伸长率与复合纱线捻系数呈正线性相关，复合纱线断裂强力、断裂伸长率与单纱捻系数呈正线性相关。     

转杯纺复合纱中长丝组分比的研究

研究长丝超喂率、长丝组分比与转杯纺复合纱性能之间的关系.在两种长丝超喂率下,设计了5种成纱线密度,选用3.33 tex/15 f的涤纶长丝在经过改装的转杯纺纱机上纺制棉涤复合纱,测试分析了复合纱中长丝组分比与成纱线密度之间的关系以及长丝组分比对复合纱结构性能的影响.结果表明:随着复合纱线密度的增加,复合纱中的长丝组分比减小,复合纱的断裂强力和断裂伸长率逐渐增加,条干CV值逐渐减小;复合纱的主要性能与长丝超喂率关系密切;与纯棉转杯纱相比,复合纱的外观和性能有较大程度的改善.     

新型PP纤维/麻复合材料的开发

本文介绍了利用低熔点热塑性PP纤维与麻纤维混合制毡,并通过热压成型和阻燃处理制成一种新型复合材料,这种热塑性复合材料具有强度高、防腐蚀、绝缘、隔音、吸音、吸震、阻燃等优良性能,而且能耗低、无污染、成本低,是麻/酚醛树脂复合材料的理想替代品.本文还在试验的基础上,研究了主要工艺参数对材料最终性能的影响.