苹果脆片的防褐变研究

探讨了抗坏血酸在不同温度、品种、浓度、真空度条件下对苹果多酚氧化酶的抑制效果。通过真空冻干及正交设计试验确定了脱水苹果片非硫钝酶工艺的最佳参数。     

低定量胶版印刷纸真空眼及印刷性能改善

分别从打浆工艺、浆网速差、辅料助剂优化等角度对减少低定量胶版印刷纸真空眼及改善印刷性能进行了阐述。     

真空处理对鲜切莲藕褐变控制的效果

目的探讨真空条件对控制鲜切莲藕褐变的影响。方法通过测定4℃常压和真空两种条件下鲜切莲藕L*值、呼吸强度、Vc和丙二醛含量及褐变度等生理生化指标,研究真空条件对鲜切莲藕品质的影响。结果与相同温度下的常压贮藏相比,真空显著有利于鲜切莲藕感官品质保持,减慢L*值的下降和Vc的损失,抑制呼吸强度、丙二醛和褐变度的上升,并能有效抑制多酚氧化酶(PPO)和过氧化物酶(POD)的活性。结论真空处理能够显著抑制鲜切莲藕贮藏期间的褐变进程。     

微真空贮藏条件下莱阳梨果实褐变的生理机制

在贮藏温度(3±1)℃、真空压力500～600torr微真空贮藏条件下,分析了微真空贮藏条件对莱阳梨果实中CAT、SOD、POD活性及O2ˉ?、H2O2含量的变化、膜透性与LOX活性、MDA含量及PPO活性、多酚含量与果实褐变等的影响。结果表明：与相同温度下的常压贮藏相比,微真空贮藏能显著提高梨果实CAT、SOD、POD活性,降低 LOX、PPO的活性及O2ˉ?生成与H2O2含量,延缓相对电导率和MDA含量的增加,推迟组织褐变出现的时间(P＜0.05)。结果表明：微真空贮藏条件一方面可能通过提高梨果实的内源抗氧化酶活性及降低LOX活性,以减少活性氧的积累及膜脂过氧化程度,维持膜的结构与功能,抑制果肉褐变;另一方面,微真空贮藏条件可能通过降低酚类物质的代谢、PPO活性及贮藏环境中氧的含量,延缓梨果实组织褐变。     

鼓式真空洗浆机低位布置设计探讨

根据鼓式真空洗浆机脱水的基本原理,浅析了鼓式真空洗浆机对麦草浆洗涤所需的脱水水柱,并提出了鼓式真空洗浆机低位布置的设计方案.     

蒸汽灭酶与破碎制浆耦合对苹果鲜榨汁品质的影响

为了探讨蒸汽处理对鲜榨果浆褐变及品质的影响,自行设计并搭建了小型蒸汽灭酶与破碎制浆耦合实验装置。试验发现,蒸汽环境打浆结束时果浆温度超过后80℃时,果浆色泽明亮、稳定,多酚氧化酶(PPO)基本失活,有效抑制了酶促褐变。对蒸汽环境打浆结束时温度93、83℃的果浆与25℃打出的果浆的理化性质、抗氧化性、风味物质进行了分析和比较。合适的蒸汽处理可以改善苹果浆理化性质,极大地保留了果浆的抗氧化性,但同时也损失了一些果浆风味物质。     

真空耦合超声波提取苹果渣多酚的工艺优化

在单因素试验基础上,采用响应面优化法建立基于真空耦合超声波提取苹果渣中多酚类物质的工艺条件优化,并通过高效液相色谱检测多酚组成且对抗氧化活性进行分析。结果表明,最佳提取工艺条件为乙醇溶液体积分数50%、提取温度50℃、真空度0.08 MPa、超声功率420 W、提取时间13 min、料液比1∶30(g/mL),在此条件下,苹果渣中多酚提取得率为6.46 mg/g。与超声波提取法相比,该方法可以明显缩短提取时间,获得多酚中表儿茶素及芦丁含量较高,并且具有较强的抗氧化活性。     

真空浸渍辅助L-半胱氨酸处理对贮藏期鲜切马铃薯的护色作用

为研究L-半胱氨酸(L-cysteine,L-cys)对鲜切马铃薯的抗褐变机制,以鲜切马铃薯为研究对象,采用真空浸渍技术辅助0.7 g/L的L-cys溶液处理鲜切马铃薯,分析贮藏期鲜切马铃薯褐变指数(browning index,BI)、多酚氧化酶活性(polyphenol oxidase,PPO)、过氧化物酶活性(peroxidase,POD)、苯丙氨酸解氨酶活性(phenylalanineammonialyase,PAL)、总酚含量及抗氧化活性的变化。结果表明,在贮藏期,试验组鲜切马铃薯BI值、PPO活性、POD活性、PAL活性均显著低于对照组(p<0.05)。试验组总酚含量在贮藏0~6 d,显著低于对照组(p<0.05),但贮藏后期则显著上升(p<0.05)。另外,两组鲜切马铃薯抗氧化活性在贮藏期,均呈先上升后下降趋势。因此,结果表明,L-cys处理可以抑制鲜切马铃薯酶活性,从而延缓鲜切马铃薯在贮藏期间的褐变。     

微波真空干燥柠檬片护色剂配方优化及其品质变化

为保持微波真空干燥(MVD)柠檬片的色泽,优化了柠檬片护色液的成分及其浓度,并分析了其对柠檬片品质变化的影响.以蒸馏水处理组为空白对照组,通过单因素和响应面试验确定了无硫护色剂组成,为0.60％乙二胺四乙酸二钠(EDTA-2Na)、0.38％L-半胱氨酸和0.82％柠檬酸;所处理产品的L*值及色差值均最优,验证试验得出...     

真空充氮热处理对鲜切双孢蘑菇贮藏中褐变的影响

为延缓鲜切双孢蘑菇褐变的发生,研究了不同真空度(0,-20,-40,-60,-80,-98k Pa)下充氮热处理对鲜切双孢蘑菇贮藏中的色泽以及过氧化物酶、多酚氧化酶、苯丙氨酸解氨酶和总酚含量的影响。结果表明,在实验范围内,真空充氮热处理可以减缓鲜切双孢蘑菇L*值(亮度)的下降速率,抑制其颜色向红色和黄色方向加重,减缓了鲜切双孢蘑菇褐变的发生;与对照组(0 k Pa)和其他真空度充氮热处理相比,在40℃、热处理5 min时,-40 k Pa和-80 k Pa真空充氮可使鲜切双孢蘑菇过氧化物酶和多酚氧化酶活性保持在较低水平,而保持较高的苯丙氨酸解氨酶活性和总酚含量,进而延缓鲜切双孢蘑菇的衰老并提高其抗性。     

Comparison between atmospheric and vacuum frying of apple slices

Vacuum deep-fat frying is a new technology that can be used to improve quality attributes of fried food because of the low temperatures employed and minimal exposure to oxygen. In this paper atmospheric and vacuum frying of apple slices were compared, in terms of oil uptake, moisture loss and color development. In addition, some apple slices were pre-dried (up to 64% w.b.) before vacuum frying to determine the overall effect. To carry out appropriate comparisons between both technologies equivalent thermal driving forces were used in both processes (ΔT = 40, 50, 60 °C), keeping a constant difference between the oil temperature and the boiling point of water at the working pressure. Vacuum frying was shown to be a promising technique that can be used to reduce oil content in fried apple slices while preserving the color of the product. Particularly, drying prior to vacuum frying was shown to give the best results. For instance, when using a driving force of ΔT = 60 °C, pre-dried vacuum fried slices absorbed less than 50% of the oil absorbed by atmospheric fried ones. Interestingly, a strong relationship between water loss and oil content was observed in both technologies, allowing the extension of observations that have been made for atmospheric frying.     

中小民营企业招聘存在的问题及对策

我国中小民营企业招聘一直存在着不少问题,严重阻碍了企业的发展。本文指出了有的中小民营企业在招聘中存在缺乏实事求是的招聘态度,没有前瞻性和后顾性,招聘条件和岗位的实际需求相脱节,面试安排不合理、效率低、质量差,招聘人员和用人部门沟通不够等问题,提出了对策,以便中小民营企业能得到持续发展。     

Pulsed electric field assisted vacuum freeze-drying of apple tissue

Impact of apple treatment by pulsed electric field (PEF) on vacuum freeze-drying was studied. Apple discs were PEF treated at an electric field strength of E = 800 V/cm for the different values of disintegration index Z. Then vacuum cooling was applied to decrease the temperature to sub-zero level and freeze-drying experiments were done at a pressure of 10 mbar. Time evolution of temperature and moisture content were compared for the PEF treated and untreated apple samples. Acceleration of cooling and drying processes was observed for the PEF treated samples. The microscopic, macroscopic analysis and data of capillary impregnation test evidenced that the PEF treatment facilitates preservation of the shape of the dried samples, allows avoiding shrinking and results in increase of the tissue pores. The sample rehydration capacity strongly depends on Z. At Z = 0.96 a high level of rehydration capacity (≈ 1.3) was observed.Industrial relevanceDifferent methods of food drying are very popular for food processing and are widely used for food preservation. However, they are very energy intensive processes and can cause undesirable changes of colour, flavour, nutrient and textural properties of foods. Vacuum freeze-drying allows obtaining high-quality food products. On the other hand, this process is power consuming, requires long time and low pressure and can provoke the damage of final dried product. Thus, the development of efficient and optimal methodology for freeze-drying of foodstuff is relevant. Application of PEF as a pretreatment procedure may be useful for improving the efficiency of drying and the quality of dried products.     

Natural colorant enrichment of apple tissue with black carrot concentrate using vacuum impregnation

Coloured apple discs containing black carrot concentrate (BCC), calcium lactate and lactic acid were formulated and produced as a new functional fresh fruit product using vacuum impregnation. Sensory test was conducted to select the most preferred impregnation formulation containing an addition of 0.0%, 0.4%, 0.8% and 1.2% BCC, 1.5%, 3.0% and 4.5% calcium lactate and 2.0%, 3.0% and 4.0% lactic acid. Results indicated that the formulation with the addition of 3% Ca‐lactate, 3% lactic acid and 0.8% BCC within 0.2 m mannitol solution was significantly preferred. The optimum vacuum pressure (211 mm Hg), vacuum time (3 min) and restoration time (20 min) according to highest colorant transfer, while the minimum cellular disruption occurs were estimated using response surface methodology. The use of Ca‐lactate and BCC contributed the treated apple to resemble untreated apple properties in terms of texture, total phenolic, total flavonoid contents and antioxidant capacity.     

Efficacy of sanitation and cleaning methods in a small apple cider mill

The efficacy of cleaning and sanitation in a small apple cider processing plant was evaluated by surface swab methods as well as microbiological examination of incoming raw ingredients and of the final product. Surface swabs revealed that hard-to-clean areas such as apple mills or tubing for pomace and juice transfer may continue to harbor contaminants even after cleaning and sanitation. Use of poor quality ingredients and poor sanitation led to an increase of approximately 2 logs in aerobic plate counts of the final product. Reuse of uncleaned press cloths contributed to increased microbiological counts in the finished juice. Finally, using apples inoculated with Escherichia coli K-12 in the plant resulted in an established population within the plant that was not removed during normal cleaning and sanitation. The data presented in this study suggest that current sanitary practices within a typical small cider facility are insufficient to remove potential pathogens.     

关于中小造纸企业信息化的几点思考

我国众多中小造纸企业当前正处于激烈市场竞争之中，本文提出如何在竞争中脱颖而出的一种思路：走企业信息化道路。针对中小造纸企业的特点，本文认为企业差异化经营必须以信息化为基础，企业信息化要以人为本，以支撑企业当前管理模式为出发点，坚持花小钱办大事的方针。     

中小服装企业的电子商务转型模式

针对目前国内炙手可热的电子商务技术,通过文献回溯、实证调查、案例探讨、统计分析等方式,归纳出中小型服装企业电子商务转型的四种模式,分析了同经营模式同行业转型、经营模式转型、同经营模式跨行业转型及跨行业转型的特征与策略。提取各个转型模式下的能力要素和能力结构,在企业战略经营、组织管理、人力资源管理、市场应变以及流程控制方面是转型的关键点。产业升级转型的关键是技术的进步,基于互联网的电子商务技术,是国内服装企业转型升级发展的有效途径之一,服装企业必须建立以信息化为纽带的企业运营模式,与传统经营方式、行业领域的发展空间进行匹配。     

中小型服装企业界定方法的探讨

通过对国内外服装企业现状分析,探讨了"中小型服装企业"的界定方法,并提出了服装中小企业界定标准设定的依据及意义.     

热风真空组合干燥苹果片试验研究

以苹果为原料,通过试验探讨了在热风真空组合干燥条件下,热风温度、热风时间、真空温度、真空度等因素对热风真空组合干燥苹果片品质的影响。结果表明:热风真空组合干燥较热风干燥而言可有效提高其干制品的质量;热风真空组合干燥苹果片较优的工艺参数为:热风温度60℃、热风时间1h,真空温度50℃、真空度30kPa。