火龙果真空冷冻干燥的模拟分析和实验研究

为了准确预测冷冻干燥时间，本文基于传热传质理论，利用COMSOL软件对厚度为12 mm、半径为4 cm的红心火龙果片进行建模，模拟升华干燥阶段火龙果内部水蒸气流动耦合热质传递、火龙果温度分布特性、升华界面位移以及冰升华过程，预测升华周期，并通过实验验证模型的可靠性。结果表明：模拟值与实测值相吻合且误差较小，火龙果中心点温度模拟值与实测值绝对误差为0.9℃,火龙果含水率模拟值与实测值相对误差为1.2%,脱水速率模拟值与实测值相对误差为6.63%。本模型可以准确模拟升华干燥过程热质传递动态变化。通过模拟对比不同厚度火龙果片升华周期，同时考虑到冻干制品质量和产量，12 mm为红心火龙果片冻干最佳厚度。     

Quantum effect of cooling down the environment temperature of mesoscopic LC circuit

We examine the quantum effect of cooling down the environment temperature of mesoscopic LC circuit, and find that the ground state of the circuit is no longer in the thermo vacuum state, but in a negative binomial state. We calculate energy of the circuit in this new state, which increases with the cooling of the environment.     

基于有限元分析的扬克烘缸表面轮廓优化研究

利用ANSYS模拟计算了铸铁扬克烘缸在受外加线载荷、蒸汽内压以及自重情况下的变形以及应力分布情况,得到了线载荷区的变形曲线,并与实际工作过程中的变形进行比较。据此对扬克烘缸表面轮廓进行优化,计算出优化后扬克烘缸的变形和应力,与优化前的结果进行比较和分析,提出了扬克烘缸轮廓优化的具体实施步骤。     

一种低挥发润滑脂的应用评价

在复合钠皂稠化多烷基环戊烷中加入复合添加剂制备了一种低挥发润滑脂。对低挥发润滑脂的饱和蒸气压、真空质损、耐辐射、相容性等应用试验性能以及真空热循环台架试验进行了评价。结果表明：该润滑脂不仅具有良好的高低温性、胶体安定性、氧化安定性、防腐蚀性、极压抗磨性，同时具有较低的饱和蒸气压（3.4×10-6 Pa）和挥发性（总损失率0.95%，可凝挥发物质量分数0.088%）；极强的耐辐射性能（可耐受1×105 Gy剂量）以及与真空设备材质良好的相容性，并且通过了真空热循环台架试验。     

真空油炸马铃薯脆片预处理工艺优化

为优化马铃薯脆片的预处理工艺,采用单因素和响应面试验,以破碎力、含油量、L*值、感官评分、综合评分和电子鼻检测挥发性成分为指标,对实验数据进行主成分分析。结果表明:不同的预处理方式对马铃薯脆片的破碎力、感官评价和综合评分有显著影响(p0.05)。主成分分析共提取5个主成分,前3个主成分总贡献率大于85%,说明提取3个主成分能够全面反映马铃薯脆片的品质信息,决定第1主成分的指标主要是感官评价和综合评分,决定第2主成分的是破碎力和含油量;决定第3主成分的是L*值和含油量。以主成分分析得到的规范化综合得分为响应值建立的二次多项式回归模型回归效果极显著(p0.01,R~2=0.9604)。确定最佳工艺参数为漂烫温度91℃、漂烫时间4 min、切片厚度4 mm和冷冻时间3 h,在此条件得到规范化综合评分0.9572,与预测值(0.9453)相接近,表明以主成分分析得到的规范化综合评分为响应值建立的回归模型具有良好的预测能力。     

Vacuum impregnation of chitosan‐based edible coating in minimally processed pumpkin

The goal of this research was to evaluate the use of vacuum impregnation (VI) and soaking techniques (ST) in the application of edible coatings of chitosan and chitosan + lauric acid to minimally processed pumpkins (MPP). The vacuum impregnation method led to greater component incorporation (5.9% and 1.75%, respectively) in the pumpkins when compared to soaking and consequently the formation of more uniform, thicker coatings (25.6 and 22.3 μm, respectively). However, VI caused greater changes in pH, acidity, colour and firmness. Relating to water content and carotenoid content, noncoated pumpkins presented greater losses during the storage period, regardless of impregnation method. The pumpkins with edible coatings, regardless of method, presented lower numbers of psychrotrophic micro‐organisms and coliforms during the storage period. Therefore, soaking was considered the best method for the application of chitosan‐based edible coatings to minimally processed pumpkins, as it led to smaller changes in the properties of the product.     

Simulation of vacuum distillation to produce alcohol-free beer

Several processes have been developed for producing alcohol-free beer while maintaining desirable sensory characteristics. One of the most popular thermal processes used is distillation, where not only ethanol but volatile aromatic components are partly or completely removed from the beer. Based on data from the literature and using the Aspen Plus simulator, this study evaluates and compares the aroma profiles of alcohol-free beers obtained by continuous vacuum distillation with different pressures and processes. Three processes were simulated at pressures of 60, 102, and 200 mbar. The first (Process A) was a standard continuous vacuum distillation, where the bottom product was an alcohol-free beer. In the second (Process B), the bottom product was blended with a standard beer that had not undergone any thermal process. In the third (Process C), part of the top stream was mixed with the bottom product. This study considered eight major compounds in beer: ethanol, propanol, isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol, ethyl acetate, diacetyl and isoamyl acetate. The three simulated pressure ranges showed similar results, indicating that reducing the pressure below 200 mbar did not improve separation. Further, vacuum distillation did not remove diacetyl from the beer. Processes B and C resulted in beer that was richer in flavour compounds. Furthermore, when these processes were compared to Process A, the concentration of esters was markedly higher. © 2019 The Institute of Brewing & Distilling     

比较调理啤酒鲈鱼片在不同贮藏条件下的品质变化

为开发鲈鱼调理食品,解决其贮藏时间短的问题,以本实验室开发的调理啤酒鲈鱼片为对象,通过普通包装(对照组)、真空包装和气调包装,测定其在4℃和-3℃条件下贮藏过程中的菌落总数、挥发性盐基氮(total volatile basic nitrogen,TVB-N)含量、硫代巴比妥酸(thiobarbituric acid,TBA)值、p H值、电导率、汁液流失率,结合感官评价,探究不同包装方式的调理啤酒鲈鱼片在4℃和-3℃条件下的品质变化规律。结果表明:不同包装方式的调理啤酒鲈鱼片在4℃或-3℃贮藏过程的汁液流失率、TVB-N含量、TBA值、电导率和菌落总数均随贮藏时间的延长而呈增长趋势,-3℃贮藏过程增长较缓慢;p H值在贮藏初期降低而贮藏后期增高;感官评分呈降低趋势。综合各项指标变化规律,调理啤酒鲈鱼片采用气调和真空包装的货架期优于普通包装,采用气调包装优于真空包装,其货架期在4℃下可达12 d,比普通包装和真空包装分别延长8 d和4 d;货架期在-3℃下可达50 d,较普通包装和真空包装分别延长35、15 d。与4℃贮藏相比,气调包装调理啤酒鲈鱼片在-3℃条件下能明显保持产品的品质并延长货架期,可满足当前冰鲜流通和消费的需求,为调理啤酒鲈鱼片的开发提供技术依据。