蒜泥绿变机理的研究

在前人对洋葱泥红变的研究基础上,研究了蒜泥绿变的机理。通过测定休眠与打破休眠的大蒜中γ-谷氨酰转肽酶的活性存在与否,大蒜中γ-谷氨酰转肽酶活性的变化与蒜泥绿变的关系,以及在不能绿变的大蒜中添加γ-谷氨酰转肽酶而使蒜泥变绿,确定了γ-谷氨酰转肽酶对蒜泥绿变的作用。研究了与蒜泥绿色素形成有关的物质:色素中间体、蒜酶、氨基酸、羰基化合物和色素前体,提出了蒜泥绿色素形成的假说。     

有关蒜泥绿色素形成的反应

本文在前人对洋葱泥红色素形成的研究基础上,研究了与蒜泥绿色素形成有关的物质色素中间体、蒜酶、氨基酸、羰基化合物和色素前体,提出了蒜泥绿色素形成的可能反应。     

Effects of microwave heating on pigment composition and colour of fruit purees

Microwave energy was applied to inactivate the oxydoreductases peroxidase (POD, EC 1.11.1.7) and polyphenol oxidase (PPO, EC 1.14.18.1) in processed fruit products. Microwave blanching of papaya, strawberry and kiwi purees at various conditions of power and time produced inactivation of PPO and POD activities depending on the fruit and the heating conditions. Treatment at 850 W/60 s produced about 60% of POD inactivation for papaya and kiwi fruit. POD activity in strawberry, however, seemed to be more resistant to microwave inactivation; treatment at 850 W/60 s only achieved a loss of POD activity near 8%. Papaya oxidoreductases showed lower stability in the microwave treatments tested. Microwave blanching at 475 W/45 s produced about 75% inactivation of POD activity and nearly complete PPO inactivation. Kiwi fruit and strawberry purees exhibited similar inactivation of PPO – 32% at 475 W/30 s and 70% at 475 W/60 s. The decrease of PPO activity in both products was almost linear at constant power. This thermal treatment, however, directly affects the colour of the fruit pulps. Papaya, kiwi and strawberry purees suffered slight colour (CIE L* a*b*) changes. Carotenoid, chlorophyll and anthocyanin changes were evaluated by HPLC and related to objective colour. Microwave treatments produced small modifications of the quantitative and qualitative composition of carotenoids (in papaya) and anthocyanins (in strawberry). Chlorophylls (kiwi) showed significant degradation as a consequence of microwave heating. © 1999 Society of Chemical Industry     

Temperature dependent electrical conductivities of fruit purees during ohmic heating

Ohmic heating takes its name from Ohm’s law; the food material switched between electrodes has a role of resistance in the circuit. In this study, the apricot and peach purees were heated on a laboratory scale static ohmic heater by applying voltage gradients in the range of 20–70 V/cm. The voltage gradient was statistically significant on the ohmic heating rates for both purees (P < 0.05). The linear temperature dependent electrical conductivity relations were obtained. Bubbling was observed above 60 °C especially at high voltage gradients. The ohmic heating system performance coefficients were in the range of 0.49–1.00. The unsteady-state heat conduction equation for negligible internal resistance was solved with an ohmic heating generation term by the finite difference technique. The predictions of the mathematical model using obtained electrical conductivity equations were found to be very accurate.     

无菌包装技术

介绍了各种无菌包装系统的原理，并讨论了影响无菌包装的有关因素，同时简要介绍了无菌包装的主要特性。     

果蔬汁饮料无菌处理和包装关键技术

详述了果蔬汁饮料无菌处理和包装的技术关键。设备预杀菌、科学制定食品无菌处理工艺规程、包装材料或容器杀菌、无菌性的获得和保持、关键控制点的设立和监控。尤其详细介绍了科学制定食品无菌处理工艺规程的计算方法,以及关键控制点的监控和记录要求。还指出了目前我国无菌处理和包装存在的问题和解决方法。     

双歧杆菌厌氧连续培养技术研究

利用组装的厌氧连续培养装置,对两歧双歧杆菌的厌氧连续培养方法进行了研究。控制连续培养系统 pH值为 6.0,采用了 4种不同的稀释率 (即 0.02 h－ 1, 0.04 h－ 1, 0.06 h－ 1, 0.09 h－ 1）,以检查稀释率对培养物的影响,当达到稳定状态时,分别对其活菌数量、乳酸和乙酸的产量进行了分析,同时以同样体积的静置批量培养为对照。结果表明,当稀释率为 0.064 h－ 1时,培养液中的活菌数最高,为 5.2× 108,而批量培养的活菌数为 2.4× 108。连续培养时,培养液中生成的乳酸和乙酸的摩尔比率,随稀释率不同而有所变化,但均不符合 3∶ 2的理论值。与批量培养相比较,连续培养时乙酸产量较高,乳酸产量较低;反之,静置批量培养时乙酸产量较低,乳酸产量较高。与静置批量培养相比,连续培养方法得到的菌液中活菌数较高,活力好,单位容积的产量较高。     

Determination of expressions for the thermal diffusivity of canned foodstuffs by the inverse method and numerical simulations of heat penetration

This paper deals with the determination of expressions to estimate the thermal diffusivity of foodstuffs placed in cans during their pasteurisation. To this end, experimental data of the temperature in the geometric centre of the can were compared with data obtained by simulations of heat penetration. For these simulations, the diffusion equation was numerically solved by using the finite volume method, with fully implicit formulation. The numerical solution was coupled to an optimiser based on the inverse method, in order to fit this solution to the experimental data obtained during the pasteurisation of tomato puree and custard cream placed within sealed cans. In the literature, the assumption of constant thermal diffusivity during the pasteurisation is common but for the analysed cases such hypothesis resulted in biased fits. Better results were obtained supposing an increasing expression for the thermal diffusivity, as function of the local temperature. In this case, the errors of the experimental data about of the numerical solution can be considered randomly distributed.     

无菌包装微生物安全性

讨论了在无菌包装中如何避免、监控及判定不良微生物的污染。     

液体饮料无菌灌装技术发展趋势

近年来,消费者对于减糖、无糖、无酒精饮料等健康饮料的广泛需求以及市场对于绿色、环保、循环经济重要性的认识提高,推动了饮料市场的转型及稳健发展,液体饮料的无菌灌装技术也随之不断进步,再生塑料、植物基包装等新型包装,脉冲强光、电子束等新型灭菌技术以及自动化智能化无菌灌装设备开始应用于饮料的无菌灌装.本文对近年来液体饮料无菌...     

全自动无菌软包装设备

介绍无菌软包装设备原理,并讨论影响无菌包装的有关因素,简要介绍无菌包装的主要特性。     

立式砖形液体饮料无菌包装机的研制

本文就国内首创的全自动立式砖形液体饮料无菌包装机研制的设计思想、实验使用情况作了介绍,旨在与专家学者们共同探讨这一课题。     

Effect of salt and sucrose content on dielectric properties and microwave freeze drying behavior of re-structured potato slices

Potato puree was used to prepare re-structured potato slices. The effect of salt and sucrose content on microwave freeze drying (MFD) and the variation of the dielectric properties of the potato slices were studied. Results showed that the dielectric constant (ε′) and loss factor (ε″) of the potato purees decreased significantly after freezing. Both salt and sucrose addition increased ε′ and ε″ of the samples at low temperatures (−25 to −5 °C). The salt content had greater influence relative to sucrose content on dielectric properties of the samples. Sucrose addition shows insignificant influence on dielectric properties of the thawing samples; while for the salted samples, ε′ decreased gradually with increasing salt content and ε″ increased significantly with increasing salt content and temperature. MFD drying rate was significant higher after adding salt and sugar.     

The use of continuous-flow electrophoresis to remove pectin in the purification of the minor pectinesterases in lemon fruits (citrus limon)

Continuous-flow electrophoresis was used to separate pectin and coloured substances from extracts of lemon pectinesterase. Two minor lemon pectinesterases were subsequently separated from two major pectinesterases, using chromatography on Sephadex G-75 and CM-Sephadex C-50. One minor pectinesterase was stable at low pH, showed the same initial pectinesterase activity at 88°C as at 25°C, and was active at 85°C for 9 min. This enzyme destabilised the cloud of single-strength lemon juice. It is suggested that the minor pectinesterases might not be true isozymes, but could arise from association of a major enzyme with pectin.     

新型尾奶回收技术

介绍了一种全新的尾奶回收技术-无菌空气吹扫技术的产生和应用。该技术主要通过无茼压缩空气制备系统和无菌压缩空气传输系统的建立，用一定压力的无菌压缩空气将物料管线内的尾奶吹扫至下一工段，并且到下一工段后，尾奶仍可全部回收利用。通过乳品厂的应用，此项技术可为厂家节省大量的资金，减少浪费。