热水处理诱导西葫芦采后低温逆境抗冷性研究

为了研究热水处理诱导西葫芦果实抗冷性,从而减轻冷害。该实验以西葫芦为原料,将西葫芦在45℃及35℃热水中分别浸泡5 min及10 min,以室温（20±2）℃下未经热水处理的西葫芦为对照,测定西葫芦果实在4℃低温下,不同贮藏时间（0、3、6、9、12、15 d）的可溶性糖含量、过氧化氢（H₂O₂）含量、过氧化氢酶（CAT）活性、超氧化物歧化酶（SOD）活性、过氧化物酶（POD）活性、丙二醛（MDA）含量、相对电导率及冷害指数等抗冷性相关指标。结果表明,与对照相比,热水处理显著增加了西葫芦果实可溶性糖含量（p<0.05）,诱导果实在贮藏初期（0³ d）H₂O₂含量短暂增加,而显著减少贮藏中后期（6¹5 d）H₂O₂含量的积累（p<0.05）,激发贮藏前期（0⁶ d）CAT和SOD活性的升高,减轻贮藏后期（9¹5 d）的活性下降,尤其是POD活性在贮藏中后期（6¹5 d）显著升高（p<0.01）,降低了MDA含量及相对电导率的升高,减少冷害指数的上升（6¹5 d）（p<0.05）,从而说明热水处理诱导西葫芦果实低温逆境下的抗冷性,有效减轻冷害,本实验中35℃热水处理10 min的效果更佳。      

热激处理对黄瓜低温贮藏特性的影响

为研究热激处理对低温贮藏中黄瓜冷害发生的防治效果及对贮藏特性的影响,以\     

热激处理对黄瓜低温贮藏特性的影响

为研究热激处理对低温贮藏中黄瓜冷害发生的防治效果及对贮藏特性的影响,以"金田208"黄瓜为试材,通过测定黄瓜果实硬度、可溶性固形物、失重率、腐烂率、冷害指数、相对电导率、丙二醛含量、VC含量、叶绿素和可溶性蛋白含量,确定黄瓜适宜的热激处理条件。结果表明:不同的热激方式、处理温度及时间会对黄瓜造成不同的影响。不适宜的热水处理会造成大量霉变,不适宜的热空气处理则会出现不同程度的失水、褪绿或烫斑。适宜的热水和热空气处理均可以对黄瓜的冷害起到推迟或减轻的效果,并有效的控制低温贮藏期间黄瓜果实的失水,能够延缓黄瓜细胞膜渗透率的增加和MDA的积累,防止可溶性蛋白含量降低。利用42℃的热水处理10min可以显著(p0.05)降低黄瓜的冷害指数和腐烂率,延缓果实硬度、可溶性固形物的下降,并维持较低的丙二醛(MDA)含量和相对电导率,对减轻黄瓜冷害症状起到了较好效果,适宜用作黄瓜的热激处理条件。     

5 种淡水鱼肌肉热特性比较研究

为研究不同品种名优淡水鱼冷藏保鲜及热加工的特性,采用差示扫描量热法研究武昌鱼、草鱼、黄颡鱼、鲈鱼和鳜鱼5 种新鲜淡水鱼鱼肉的水分含量、冰点、变性温度、变性热焓和比热容并进行品种间的比较。结果发现：5 种淡水鱼冰点分布在－0.57～－0.1 ℃之间;50 ℃附近热吸收峰起始温度分布在37～41.57 ℃之间,终止温度分布在60.47～62.33 ℃之间;变性热焓在1.680 0～2.499 7 J/g之间;70 ℃附近热吸收峰的起始温度分布在66.33～71.13 ℃之间,终止温度分布在73.60～82.20 ℃之间,变性热焓在0.418 0～0.512 2 J/g之间;鱼肉的比热容在1.658 0～3.862 3 J/（g·K）之间。结果表明：在5 种新鲜淡水鱼中,武昌鱼水分含量和冰点相对较低;草鱼肌球蛋白和鳜鱼肌动蛋白变性温度和变性热焓相对较高,蛋白质稳定性更高;新鲜鱼肉的比热容高于冻结鱼肉,加工后鱼肉的比热容高于未加工鱼肉。     

热水处理减轻采后黄瓜果实低温贮藏冷害的条件优化

为探索热水热激处理减轻黄瓜冷害的最佳处理条件,采用"申青"黄瓜作为试验试材,以电解质外渗率作为冷害评价指标,利用三因素二次正交旋转组合设计建立模型,结果表明,优化得到的最佳热水热激处理温度37. 5℃,最佳热激时间24 min。黄瓜果实经热激处理后,在温度4℃、湿度85%冷库中贮藏5 d的电解质外渗率实测值为25. 13%,与理论值相对误差为1. 21%,较未处理黄瓜果实提高了34. 07%,说明该方法稳定可靠。该试验优化了热水处理黄瓜果实低温贮藏冷害参数,建立的模型稳定可行,为黄瓜果实抗冷性的提高和冷敏型果蔬冷害的防治提供了一定的试验参考和理论依据。     

果实对高温逆境的响应及其信号转导机理

介绍了高温对果实生理的主要影响,讨论了提高果实抗热性的机制及高温条件下果实对高温响应所介导的第二信使系统和热激蛋白(HSPs)在提高果实耐高温能力方面所起到的重要作用。高温锻炼作为一种果实对高温环境的适应性措施,显著提高了果实的抗热性。钙离子(Ca2 )、肌醇磷酯信使系统和过氧化氢(H2O2)都可能作为第二信使参与果实对高温逆境响应的信号转导过程。HSPs的产生和表达增强对提高果实细胞的抗高温能力起到了关键的作用。建议深入研究第二信使与果实耐热性之间的关系。     

不同品种李果实低温贮藏特性研究

为明确不同品种李果实低温((0±0.5)℃,相对湿度80%~90%)贮藏特性,以早熟品种‘盖县’、‘美国一号’、‘总统’,中熟品种‘御皇’以及晚熟品种‘黑宝石’、‘澳洲十四’李果实为材料,研究了低温贮藏过程中果实硬度、可溶性固形物含量(SSC)、可滴定酸含量、pH、失重率、出汁率、乙烯释放速率等指标的变化规律,比较分析了不同品种李果实低温贮藏特性差异。结果表明:‘御皇’李耐贮性最强,‘澳洲十四’与‘黑宝石’次之,但风味更为浓郁;‘盖县’柔软多汁,但SSC低;‘美国一号’、‘总统’李软化快,易发生腐烂,不耐贮藏。研究结果为揭示不同品种李果实的低温贮藏差异性提供了理论依据和应用基础。     

不同品种金枪鱼肌肉组织的热物理特性

为研究不同品种金枪鱼肌肉组织的热物理学特性,对5个品种金枪鱼的背部与腹部肌肉进行主要营养成分测定与运用差示扫描量热的方法研究相变过程热特性,同时进行相关性与聚类分析。结果表明:金枪鱼肌肉的比热随温度升高而升高,在融化过程中出现峰值后回归稳定,不同品种金枪鱼的比热值相差不大;通过聚类分析可将样品分为3类,可以根据聚类分类特点指导解冻工艺,以进行差异性的解冻工艺与设备研发。     

热激处理后低温贮藏下香蕉果实的挥发物成分分析

为探讨热激处理诱导香蕉果实产生抗冷性的机理,利用热激处理（52℃热水浸泡3 min）香蕉果实,之后将香蕉果实置于7℃下贮藏。采用气相离子迁移谱检测香蕉果实的挥发物,测定香蕉果实冷害指数。结果表明,与对照组和H+7℃4 h处理组相比,7℃4 h处理组明显降低了丁酸乙酯、己二酮、2,3-丁二酮、甲基丙醛、羟基丙酮、3-甲基丁酸、芳樟醇等19种成分的含量,明显增加了乙醇、三乙胺、2-己醇、戊酮-2,3-二酮、苯乙醛、2-丁酮、3-甲基-3-丁烯-1-醇等30种成分的含量。与对照组和7℃4 h处理组相比,H+7℃4 h处理组明显增加了1-戊醇、糠醇、4-甲基苯酚、2-戊酮等13种组分的含量。根据主成分分析,H+7℃4 h处理组与对照组的组分含量比较接近,而与7℃4 h处理组的组分含量差异较大。进一步研究发现,热激处理能明显减轻7℃冷藏香蕉果实的冷害症状,推测这13种成分含量的迅速增加可能在热处理诱导香蕉抗冷性中起到重要调控作用。     

脆肉鲩低温相变区热特性的研究

采用差示扫描量热仪,研究脆肉鲩鱼肉在低温相变区的冰点、表观比热和热焓以及NaCl、NaCl 与蔗糖混合物添加量对脆肉鲩热特性的影响。结果表明,脆肉鲩鱼肉的冻结相变温区为－ 12.5～－ 11℃,熔融相变温区为－ 1.9～0.1℃,冰点为－ 0.2℃,冰点的表观比热和热焓值分别为130.56J/g·℃、305.57J/g。随着NaCl、NaCl和蔗糖混合物添加量的增加,脆肉鲩肌肉的相变温区向低温方向移动,冰点的表观比热和热焓值下降。鱼肉中NaCl添加量较低时,添加蔗糖可减缓相变温度的下降,当NaCl 添加量大于2% 时,添加蔗糖对鱼肉相变区温度的影响不大,NaCl 起主导作用。     

Composition‐Based Prediction of Temperature‐Dependent Thermophysical Food Properties: Reevaluating Component Groups and Prediction Models

Prediction of temperature‐dependent thermophysical properties (thermal conductivity, density, specific heat, and thermal diffusivity) is an important component of process design for food manufacturing. Current models for prediction of thermophysical properties of foods are based on the composition, specifically, fat, carbohydrate, protein, fiber, water, and ash contents, all of which change with temperature. The objectives of this investigation were to reevaluate and improve the prediction expressions for thermophysical properties. Previously published data were analyzed over the temperature range from 10 to 150 °C. These data were analyzed to create a series of relationships between the thermophysical properties and temperature for each food component, as well as to identify the dependence of the thermophysical properties on more specific structural properties of the fats, carbohydrates, and proteins. Results from this investigation revealed that the relationships between the thermophysical properties of the major constituents of foods and temperature can be statistically described by linear expressions, in contrast to the current polynomial models. Links between variability in thermophysical properties and structural properties were observed. Relationships for several thermophysical properties based on more specific constituents have been identified. Distinctions between simple sugars (fructose, glucose, and lactose) and complex carbohydrates (starch, pectin, and cellulose) have been proposed. The relationships between the thermophysical properties and proteins revealed a potential correlation with the molecular weight of the protein. The significance of relating variability in constituent thermophysical properties with structural properties––such as molecular mass––could significantly improve composition‐based prediction models and, consequently, the effectiveness of process design.     

Thermophysical Properties of Extruded Beef/Corn Flour Blends

Thermal properties, specific heat, and thermal conductivity of three beef/corn meal blends extruded to reach end product temperatures of = 91°C and 109°C were analyzed. Density was also measured and used to calculate thermal diffusivity. The extruded products had densities of 1,054 to 1,091 kg/m³; specific heat was 2.944 to 3.055 kJ/ kgK; and thermal conductivity, 0.26 to 0.39 W/mK. Calculated values of thermal diffusivity were 0.831 to 1.200 (xl0^-7m7sec). With the exception of specific heat, extrusion conditions and formulation affected some of the products physical characteristics and thermal properties.     

海参低温贮藏过程中品质与理化性质的变化

研究预处理的海参在4℃条件下贮藏60 d的品质及理化性质变化.定期分析处理组和对照组海参可溶性胶原蛋白含量、硬度和咀嚼度变化,蛋白质降解情况,组织蛋白酶-L的活性,Caspase-3的活性,结构蛋白表达量的变化及自由基的生成情况.结果表明,随着低温处理时间的延长,前期各指标变化不显著,可溶性胶原蛋白含量从第10天开始明...     

低温热敏变色材料的研究及其应用

介绍了热变色材料的分类和发展状况,对其各分类的变色机理进行剖析,对热变色材料的应用进行探讨,对其发展的前景进行展望。     

反演法求小麦面团在冻结温度范围内的热导率

为确定小麦面团在冻结温度范围内的热导率,采用差式量热扫描法测量了3个不同水分含量面团的比热,然后利用COMSOL软件反演求出面团在-30~30℃范围内的热导率。结果表明,面团热导率随水分含量增大(38%~44%)而逐渐升高;且随着温度的降低,面团的热导率逐渐降低,但是当面团的温度降至冰点后,面团的热导率急剧上升,然后又呈缓慢上升趋势。通过对面团热导率与水分含量关系的进一步分析,建立了速冻温度范围内面团热导率随温度和水分含量变化的数学模型。     

A Novel Method for Simultaneous and Continuous Determination of Thermal Properties during Phase Transition Applied to Calanus finmarchicus

Abstract: The thermal properties of a product are the most important parameters for practical engineering purposes and models in food science. Calanus finmarchicus is currently being examined as a marine resource for uncommon aquatic lipids and proteins. Thermal conductivity, specific heat, enthalpy and density were measured over the temperature range from −40 to +20 °C. The initial freezing point was determined to be −2.3 °C. The thermal properties were recorded continuously on 4 samples using a new method, and the results were compared with predictive models. The accuracy of the new method is demonstrated by different calibration runs. Significant differences in the thermal conductivity of the frozen material were found between the parallel-series model and the data, whereas the model of Pham and Willix (1989) or the Maxwell–Euken adaption showed better agreement. The measured data for specific heat, enthalpy, and density agreed well with the model. Practical Application: The thermal data obtained can be used directly in food engineering and technology applications, for example, in a thin layer model for freezing food for which precise thermal data for each layer are now available, enabling the more accurate prediction of freezing times and temperature profiles. Dimensionless numbers (such as the Biot number) can also be based on measured data with minor deviations compared to more general modeled thermal properties. Future activities will include the generation of a comprehensive database for different products.     

低温冷冻技术对纸张性能的影响

目前图书馆、档案馆多选用低温冷冻技术杀灭害虫。为研究该技术对纸张的影响,选择6种纸样(道林纸、字典纸、双胶纸、打字纸、新闻纸和试卷纸)进行180个周期的低温冷冻处理,测定其与室温下避光保存纸样的机械性能和水抽提液pH值等性能指标的相对变化。结果显示,各项性能指标相对变化率基本都不超过5%,只有打字纸冷冻后抗张指数相对变化率达到8. 6%。因此多次低温冷冻基本不会对纸张性能造成影响,还有利于缓解漂白程度较高的纸张保存过程中白度和抗张强度的下降程度,适宜用于图书档案的杀虫操作。     

Heat transfer properties of chicken-drum muscle

Thermal properties namely bulk density, specific heat capacity and thermal conductivity of chicken-drum muscle were measured over a wide range of muscle moisture content and temperature. Variation of muscle density was quadratic with respect to moisture content. Specific heat capacity and thermal conductivity also showed quadratic variation with moisture content. The effect of temperature on specific heat capacity was related to the state of thermal denaturation of the chicken muscle protein. Regression equations of density, specific heat capacity and thermal conductivity are presented. © 1998 Society of Chemical Industry.     

低温等离子体处理对精练后棉织物性能的影响

通过改变低温等离子体处理的气体类型，功率、时间工艺参数，对精练后的棉织物进行改性处理，测试了处理后棉织物的性能。结果表明，经等离子改性处理后，棉织物的拉抻断裂强力和毛细管效应有明显提高，撕裂强力和折皱回复角变化不大，在扫描电子显微镜下可观测到棉纤维表面有明显刻蚀现象。