不同真空预冷抽气速率对卷心菜预冷过程及贮藏后品质的影响

利用风冷预冷、不同真空预冷抽气速率(降压速率指数Y值分别为A-0.126 min-1;B-0.185 min-1;C-0.315 min-1)等技术对卷心菜进行预冷,预冷后包装并放置于5±2℃冷库贮藏。通过测定其过程以及贮藏过程中的相关指标来评价不同预冷方式对卷心菜的影响。结果表明,无论何种抽气速率预冷都要快于风冷,但C组(65 min)与B组(70 min)预冷时间相当,且差异性不显著(p0.05)。同一真空抽气速率对卷心菜不同部位的降温几乎是同时的。贮藏6 d后,B较其他组而言,其呼吸速率183.9 mg/(kg·h)及顶端CO2(7.2%)含量要明显低于A、C组,而维生素含量C(46 mg/kg)及顶端O2(2.1%)则相反,且差异性均显著(p0.05)。综上所述,0.185 min-1的抽气速率更适合于卷心菜的预冷。     

新鲜蔬菜真空预冷实验分析

本研究针对三种不同类型的新鲜蔬菜进行了真空预冷实验。比较了白菜、卷心菜、土豆不同深度处温度在真空预冷过程中随时间的变化,真空室内压力高低对叶菜类和非叶菜类蔬菜真空预冷的影响;分析了蔬菜表面洒水对其在真空预冷中的失重和预冷效果的影响。     

蔬菜真空预冷实验分析

针对白菜、萝卜、土豆三种蔬菜,进行了真空预冷实验,分析了真空室内压力、蔬菜大小、蔬菜表面洒水等因素对蔬菜真空预冷的影响,为真空预冷工艺改进和预冷技术的推广应用提供参考。      

蔬菜真空预冷实验分析

针对白菜、萝卜、土豆三种蔬菜,进行了真空预冷实验,分析了真空室内压力、蔬菜大小、蔬菜表面洒水等因素对蔬菜真空预冷的影响,为真空预冷工艺改进和预冷技术的推广应用提供参考。     

白蘑菇真空预冷工艺的研究

考察预冷温度、水分添加量、预冷压力等因素对白蘑菇的色差和可溶性固形物的影响,通过中心组设计和响应面分析考察因素间的交互作用,优化白蘑菇的预冷工艺.研究结果表明,白蘑菇最优的预冷工艺条件为:预冷温度为5℃、水分添加量5%和最终预冷压力250 Pa.     

真空预冷双孢菇及其贮藏保鲜工艺

为探究双孢菇保鲜新方法,采用真空预冷技术,研究了不同真空压力和预冷温度处理对双孢菇保鲜效果的影响。结果表明:在5℃预冷终温下,对预冷压力为800、1 000、1 200 Pa真空预冷处理的蘑菇进行冷藏保鲜时,经1 000 Pa真空预冷处理的双孢菇质量损失和硬度减少最低;在1 000 Pa预冷压力下,对预冷终温为5、7、9℃进行真空预冷处理的蘑菇进行比较,得出经5℃真空预冷处理的双孢菇质量、硬度、色差变化率最低。双孢菇经真空预冷处理后可明显延长其保鲜期。双孢菇的最佳真空预冷工艺条件:预冷压力为1 000 Pa,预冷温度为5℃     

几种蔬菜真空预冷过程的实验研究

以卷心菜、土豆等为对象进行了真空预冷实验。分析了在真空预冷过程中,蔬菜内不同部分的温度变化,不同种类蔬菜的及其真空槽内压力等因素对真空预冷效果的影响。蔬菜的含水量及其分布,蔬菜结构紧密程度,真空槽内压力影响着蔬菜在真空预冷过程中内部水蒸气的产生及其散失,从而影响蔬菜的预冷温度及其失重。。     

叶菜类蔬菜真空预冷模型的研究

为研究叶菜类蔬菜在真空预冷过程中温度场、水及水蒸气浓度场变化规律,利用Comsol软件建立真空预冷模型,模型包括多孔介质的扩散与传热耦合过程,由五部分联立求解。通过对结构简单的肉制类火腿的模拟,验证了真空预冷模型可靠性,进一步验证模型对叶菜类蔬菜的适用性。模拟与实验对比结果表明:肉制类表面最大温差3.1 ℃,中心最大温差4.3 ℃,整体趋势相同,模型具有可靠性;叶菜类中菠菜最大温差在3 ℃以内,菠菜、小白菜、菜心、芥兰温度变化趋势与模拟一致,模型适用于叶菜类蔬菜。预测表明:叶脉影响叶菜类蔬菜的参数分布,沿叶脉处温度、水及水蒸气浓度均较低,模拟对真空预冷中各参数设定有指导作用。     

草莓真空预冷理论分析及实验研究

为了研究不同预冷压力对草莓真空预冷的影响,本文首先对草莓真空预冷建立了数学模型并进行了理论分析,得出草莓表面水蒸气扩散量与其表面温度的平方根呈正比,与舱内压力呈反比的结论。同时,分别对草莓在0.5、0.8、1.0 kPa的预冷压力下进行真空预冷实验。实验结果表明:舱内温度变化与预冷压力无关,不同预冷压力下的相对湿度变化趋势相同;不同预冷压力对草莓的冷却速率、失水率以及预冷之后草莓的呼吸强度影响较大,预冷压力越低,冷却速率越高,失水率越低,预冷之后的呼吸强度越弱,预冷压力为0.5 kPa时,其冷却速率为2.36 ℃/(kg·h),失水率为1.67%,呼吸强度为12 mg CO₂/(kg·h);并且有预冷压力越低,同一颗草莓不同位置处(草莓表面、草莓1/4处、草莓中心)的温降差异越大;草莓可溶性固形物含量不受预冷压力的影响。     

马兰和菊花脑真空预冷保鲜技术研究

比较了不同预冷方法和贮藏温度对贮藏期间马兰和菊花脑营养成分和外观的影响。结果表明,真空预冷后低温贮藏效果最好,Vc含量下降少,粗纤维含量增加少,与对照相比可延长保鲜期2d。     

Feasibility assessment of vacuum cooling of cooked pork ham with water compared to that without water and with air blast cooling

To optimise vacuum cooling for application in the meat industry, an improved cooling method, i.e. vacuum cooling with water (or immersion vacuum cooling), was designed to cool cooked pork ham (2.2 ± 0.2 kg). It was found that the cooling time of vacuum cooling with water was significantly shorter than that of traditional air blast cooling (P < 0.05). For the cooling loss, vacuum cooling with water was significantly lower (6.99%) than that of vacuum cooling without water (13.71%) (P < 0.05). Significant differences in physical and chemical attributes were also observed for ham processed by vacuum cooling with and without water (P < 0.05). Therefore, for a certain size of pork ham, vacuum cooling with water could be an effective method to meet safety guidelines and obtain compatible quality attributes with air blast cooling.     

Feasibility assessment of vacuum cooling followed by immersion vacuum cooling on water-cooked pork

Vacuum cooling followed by immersion vacuum cooling was designed to cool water-cooked pork (1.5 ± 0.05 kg) compared with air blast cooling (4 ± 0.5 °C, 2 m/s), vacuum cooling (10 mbar) and immersion vacuum cooling. This combined cooling method was: vacuum cooling to an intermediate temperature of 25 °C and then immersion vacuum cooling with water of 10 °C to the final temperature of 10 °C. It was found that the cooling loss of this combined cooling method was significantly lower (P < 0.05) than those of air blast cooling and vacuum cooling. This combined cooling was faster (P < 0.05) than air blast cooling and immersion vacuum cooling in terms of cooling rate. Moreover, the pork cooled by combined cooling method had significant differences (P < 0.05) in water content, color and shear force.     

蔬菜真空冷却喷水率的研究

为了研究喷水率对真空冷却蔬菜的影响,本文选取叶菜类有代表性的茼蒿在自行设计的装置中进行了真空冷却实验,考察了不同喷水率对相对能耗、降温速率和失水率的影响。结果表明,采用高喷水率时,真空冷却过程中的相对能耗较少,降温速率较快,失水率较低。     

真空冷却技术在蛋糕制品冷却中的应用研究

采用真空冷却技术对新鲜出炉的蛋糕进行冷却处理,分别考察了冷却终温、冷却终压、水分添加量等因素对蛋糕品质的影响。实验结果表明在真空冷却终温20℃、冷却终压1800Pa和水分添加量5%的条件下能最大程度保持蛋糕的品质,在总体感官上与自然冷却样品无显著差异;与传统自然冷却的150min相比,真空冷却将250g蛋糕由81℃冷却至20℃仅需11min,且样品中心与表面温差不超过1℃。     

液体真空制冷的机理分析

分析了绝热情况下真空制冷过程中的传热传质机理,建立了真空制冷的数学模型,推导了液体温度随时间的变化函数,预测了液体温度随时间的变化趋势.在理论计算基础上,对所建立的模型进行了实验验证,情况表明,二者非常吻合.     

Optimisation of immersion vacuum cooling operation and quality of Irish cooked sausages by using response surface methodology

The effects of initial water temperature (X₁, 20–72 °C), pressure reduction rate (X₂, 60–90 mbar/min), agitation speed (X₃, 300–600 rpm) as well as condensing temperature (X₄, ?10 ?2 °C) during immersion vacuum cooling (IVC) of Irish cooked sausages were evaluated and optimised by response surface methodology for the first time. The cooling loss, colour, texture and moisture content of the sausages were estimated. The significant polynomial regression models on cooling time (P < 0.001) and hardness (P < 0.05) were established. Results showed that the condensing temperature affected the cooling time of IVC sausage significantly (P < 0.001), while hardness was significantly influenced by initial water temperature and condensing temperature. Three optimum operational modules were determined and validated. The cooling times in all modules were compliant within US Department of Agriculture (USDA). Module 3 (X₁: 4.51 °C, X₂: 72.88 mbar/min, X₃: 459.09 rpm, X₄: ?8 °C) was the most practical option for achieving the required high cooling rate with high‐quality properties.     

真空冷却过程中飞溅现象分析及其防止研究

真空快速冷却带汤汁食品时,会发生汤汁飞溅现象。以水为研究对象,在真空冷却实验台上,通过可视窗观察分析了容器中的热水在冷却过程中沸腾飞溅现象;并提出采用控制冲气阀门的启闭,使用梯度降温方法可有效防止沸腾飞溅的发生,使失水率减少16%,但冷却时间相对延长了5～10min。     

白煮整鸡浸泡真空冷却改进技术的研究

以白煮整鸡为研究对象,分别使用风冷(AB)、水冷(WI)、浸泡真空冷却(IVC)及先浸泡真空冷却后水浸泡冷却(IVC-WI)4种方式对其进行冷却处理,并对样品的冷却效果进行分析。结果表明:实验样品从中心温度(约为95℃)冷却到10℃,IVC-WI的冷却时间(53min)比AB(145min)的缩短92min,且前者的冷却速率(1.54℃/min)约是后者(0.62℃/min)的2.5倍。与传统风冷冷却相比,IVC-WI处理后的样品冷却损失更少,产品得率和水分含量显著升高(P<0.05),而且IVC-WI处理后的样品的色差和质构也有所改善,从而很好地改善了实验样品的品质。     

Effects of processing parameters on immersion vacuum cooling time and physico-chemical properties of pork hams

The effects of agitation (1002 rpm), different pressure reduction rates (60 and 100 mbar/min), as well as employing cold water with different initial temperatures (IWT: 7 and 20 °C) on immersion vacuum cooling (IVC) of cooked pork hams were experimentally investigated. Final pork ham core temperature, cooling time, cooling loss, texture properties, colour and chemical composition were evaluated. The application for the first time of agitation during IVC substantially reduced the cooling time (47.39%) to 4.6 °C, compared to IVC without agitation. For the different pressure drop rates, there was a trend that shorter IVC cooling times were achieved with lower cooling rate, although results were not statistically significant (P > 0.05). For both IWTs tested, the same trend was observed: shorter cooling time and lower cooling loss were obtained under lower linear pressure drop rate of 60 mbar/min (not statistically significant, P > 0.05). Compared to the reference cooling method (air blast cooling), IVC achieved higher cooling rates and better meat quality.     

酱卤鸡肉真空冷却的可行性评估研究

研究了真空冷却、浸液真空冷却、自然冷却和鼓风冷却,得到冷却方式对冷却速率、冷却损失、品质变化及后期贮藏阶段微生物的影响,进一步对真空冷却和浸液真空冷却可行性评估。普通真空冷却质量损失过多,对产品产生一些负面影响。实验尝试对样品进行浸液真空冷却,避免了水分的大量损失,其冷却时间明显小于自然冷却和鼓风冷却(p0.05)。对品质的影响:不同冷却方式之间,剪切力、TPA、色度值均存在差异。真空冷却样品的剪切力、硬度、咀嚼性要明显大于其他冷却(p0.05),弹性较差,真空冷却形成的多孔结构对后期储藏阶段脂肪氧化有促进作用。真空冷却的样品微生物数量显著低于自然冷却和鼓风冷却,对产品的保藏有利。综合评估,浸液真空冷却要优于其他冷却方式。