超高压杀灭低酸性食品中耐压菌的动力学模型

为了描述超高压杀菌过程和预测杀菌效果,该文建立了超高压对低酸性食品中4种耐压菌及其芽孢的杀菌动力学模型。首先在300～500 MPa的超高压条件下获得了枯草芽孢杆菌、地衣芽孢杆菌、嗜热脂肪芽孢杆菌和致黑梭状芽孢杆菌的芽孢致死曲线。选取线性模型和Weibull模型来拟合超高压杀菌的动力学过程,以精确因子、均方差和决定系数R2作为模型拟合度优劣的评判指标。数据分析结果表明,Weibull模型在300～500 MPa具有很好的拟合性（R2＞0.9）,线性模型的拟合效果不佳（R2＜0.83）。所得Weibull方程可有效预测特定压力-时间组合下的灭菌效果,可用于指导超高压灭菌的实际生产。     

糖姜间歇微波真空干燥特性及其动力学模型

为了探讨避免糖姜焦糊的微波真空干燥模式,该文以湿糖姜为原料,研究真空度、功率质量比及姜块的体积对糖姜间歇微波真空干燥速率及品质的影响,建立糖姜干燥动力学模型。结果表明：糖姜采用间歇式微波真空干燥技术,能避免焦糊和褐变的发生,适宜微波加热和间歇时间分别为30和90?s,功率质量比为10～?15?W/g,真空度为-80?kPa;糖姜微波真空干燥的动力学满足指数模型,该模型能很好预测微波真空干燥过程中糖姜含水率随干燥时间、比功率、真空度和姜块体积的变化关系,试验结果为实现糖姜的可控制工业化干燥提供技术依据。     

银耳微波真空干燥特性及动力学模型

利用微波真空干燥技术,对银耳微波真空干燥特性进行研究,探讨不同微波强度、真空度及初始含水率对失水速率的影响,其中微波强度对失水速率影响最大。根据试验数据建立银耳微波真空干燥的水分比与干燥时间关系的动力学模型,并对模型进行拟合检验。结果发现银耳微波真空干燥过程符合Page模型,该模型预测值与实测值拟合良好。该模型可以准确预测银耳在微波真空干燥过程中的含水率和失水速率。     

微波技术在食品和农产品加工中应用研究进展

微波加热技术具有速度快、可控性高等特点,在食品和农产品的热加工过程中具有较强应用潜力。该研究在分析微波加热原理的基础上,从技术应用、设备研制和仿真研究等方面介绍微波加热应用现状,如在农产品干燥、杀菌、萃取和膨化等方面进行深入研究和应用。指出微波加热在机理解析、工艺局限性、加热不均匀性和能量利用低等问题,尤其是微波场对物料内极性成分作用机制的研究深度、微波加热时在物料内温度和水分分布的不均匀性规律定量表征等方面,严重影响产品质量稳定性和能量充分利用。从揭示微波在加热腔体内传递和物料内吸收的机理,提高微波加热均匀性和改善加工质量,以及研制智能化工业用微波加工设备等方面,指出微波加热技术在食品和农产品加工中应用热点研究方向。针对微波加热技术在农产品和食品加工中科学问题、技术需求和设备现状,为发挥技术优势、拓展应用领域,该文提出微波加热理论研究与技术应用的发展趋势,以期提高微波热加工技术工业化应用适用性、保证产品质量和能量利用率。     

微酸性电解水储藏和杀菌过程中有效氯衰减的动力学模型

为探明微酸性电解水(slightly acidic electrolyzed water, SAEW)在储藏及杀菌过程中理化指标的变化规律,将SAEW置于25、30、35、40、50℃环境温度下,测定其主要理化特性参数pH值、氧化还原电位(ORP),以及有效氯质量浓度(ACC)随储藏时间(0～12 d)的变化,同时也测定了SAEW对大肠杆菌(ATCC 25922)杀菌过程中ACC的变化规律。SAEW的pH值随储藏时间的延长而增大,ORP和ACC则减小,且储藏温度越高,各理化特性参数的变化幅度越大;在SAEW对大肠杆菌的杀菌过程中,ACC值不断降低。同时对储藏过程及杀菌过程中的有效氯衰减建立动力学模型,拟合后决定系数均达0.90以上。结果表明储藏温度和储藏时间对SAEW的理化特性参数有明显影响,且储藏过程与杀菌过程中的有效氯衰减符合一级动力学模型。相关研究结果为SAEW在农业、食品、医疗及环保等领域的应用提供了参考。     

微波杀菌对枇杷果汁品质的影响

为了探讨微波杀菌工艺对枇杷果汁贮藏期间品质的影响,以宁海白枇杷为原料加工成汁,经巴氏灭菌和微波杀菌处理后,研究4℃冷藏过程中菌落总数、总酚含量、Vc含量、DPPH·清除能力、pH、可溶性固形物(SSC)、多酚氧化酶(PPO)和过氧化物酶(POD)活性等指标的变化情况。结果表明,微波杀菌与传统巴氏杀菌相比,有相同的杀菌效果,能很好地延长果汁贮藏期;同时,微波杀菌处理的枇杷果汁总酚、Vc含量和DPPH·清除能力均显著升高,PPO和POD完全失活,而对果汁pH和SSC无显著影响。说明微波杀菌技术不仅具有较好的杀菌效果,而且能最大限度地保持枇杷果汁品质。本研究结果为微波杀菌在果汁工业的应用中提供了理论依据。     

松嫩平原土壤次生盐渍化过程模型研究

分析了松嫩平原土壤盐渍化过程的特殊性,认为本区土壤盐渍化地球化学模型的建立,必须同时考虑离子交换这一重要的地球化学过程,并提取出土壤盐分迁移的滞留因子R.建立了土壤次生盐渍化地球化学过程模型,探讨了模型的求解方法,模型计算与实测结果表现出较好的拟合度.同时利用该模型对不同环境、不同时间尺度条件下土壤剖面的水分及盐分状况进行了预测.     

Logistic模型模拟乙醇发酵产物动力学

乙醇发酵产物动力学的研究有助于更好的认识发酵过程,为其工业放大及生产操作条件的优化提供理论基础。基于Logistic方程的菌体生长动力学模型可较好的描述细胞生长期及细胞自身抑制作用,但由于该模型方程中的比例参数与积分常数没有明显的生物学意义,使其应用受到了限制。该文从生物学与化学工程学结合角度对Logistic模型方程重新参数化,将发酵产物乙醇生成动力学与酵母生长动力学方程类比,给出了乙醇浓度的显式函数模型,模型中不再出现酵母菌浓度变量,大大简化了模型,并且赋予参数其物理意义;在研究了以葡萄糖和玉米淀粉为原料乙醇质量浓度、总糖质量浓度在不同底物质量浓度和料液比条件下随发酵时间的变化规律的基础上运用该模型拟合了以葡萄糖和玉米淀粉为原料进行乙醇发酵的试验数据,结果表明:模型值与试验数据具有较好一致性,拟合度均大于0.97,可见该重新参数化的Logistic模型可以描述发酵生产乙醇过程中产物乙醇的动力学行为,具有预测工业上实际发酵过程中乙醇浓度的潜力。     

基于多智能体的土地利用变化模拟

建立土地利用变化模型,模拟多种情景下的土地利用变化过程,能够为科学的土地利用决策提供辅助支持。以常州市新北区为研究区,从政策特征因子、全局特征因子和空间特征因子3个方面构建土地利用情景特征因子体系;运用多智能体建模方法构建基于主体的土地利用情景模拟模型;设定快、中、慢3种经济社会发展条件下的土地利用情景(I、II、III),模拟研究区2006-2020年土地利用变化。结果表明:3种土地利用类型的空间全局拟合度都相对较高,城镇用地、农村居民点用地和耕地的空间全局拟合度分别为78.45%、99.85%、98.35%;空间变化拟合度较低,分别为55.18%、0.02%、69.11%。在3种土地利用情景下,城镇用地增加面积分别为3788.44、2922.83和2114.64hm2,农村居民点用地减少面积分别为1106.60、858.61和592.35hm2,耕地减少面积分别为5378.72、4817.03和4238.97hm2。说明情景I下城镇化速度较快,城乡用地转换明显,农村居民点整治力度较大;情景II下城镇用地空间扩张和人口增长都减缓速度,耕地资源的流失得到一定程度控制;情景III下城乡用地变化速度显著放缓,耕地资源流失得到有效控制。     

秸秆料包微波加热过程的温度分布的数值模拟

为深入了解微波加热过程,该文主要对秸秆料包微波加热过程的升温特性进行研究。将微波加热考虑成内热源,并使用Lambert定律对内热源分布进行简化计算,进而采用具有内热源形式的导热微分方程对微波加热过程中大尺寸物料内的温度分布进行了数值计算。最后,采用自制的微波加热装置,对秸秆料包微波加热过程中的温度分布进行了测量,并与模拟结果进行了对比。结果表明：数值模拟结果能较好地反映微波加热过程中大尺寸物料内部的温度分布,进而揭示大尺寸物料内部的传热规律。研究结果对微波热解装置的设计和优化,以及微波热解技术的推广利用有一定帮助。     

微生物不同生长期及介质参数对脉冲磁场杀菌效果的影响

利用脉冲磁场对大肠杆菌和金黄色葡萄球菌在不同生长阶段、不同介质温度及pH值的情况下进行杀菌试验，结果表明：这两种菌在对数生长期比稳定生长期和延迟生长期对磁场更敏感，两种细菌在对数生长期的后期杀菌效果均出现反弹变差的现象，反弹趋势延长至稳定生长期，并趋于平缓；介质温度越高，脉冲磁场杀菌效果越好，但该温度远低于热致死温度；介质pH值越偏中性，杀菌效果越差，pH值小于5时，杀菌效果较好。     

Composition and antibacterial activity of Pseudocytisus integrifolius (Salisb.) essential oil from Algeria

The essential oil composition of an endemic Algerian Cruciferae, Pseudocytisus integrifolius (Salisb.) Rehder, was analyzed by gas chromatography (GC) and GC-mass spectrometry (MS). Eighty-three components representing more than 96.5% of the oil were identified. The major components were dimethyl disulfide (33.4%), dimethyl trisulfide (24.2%), and an unsaturated nitrile (31.7%). Fractionation on a silica gel column led to the identification of trace-level compounds, in particular, polar compounds such as nitriles and aldehydes, and to the isolation of dimethyl disulfide, dimethyl trisulfide, and an unsaturated nitrile. Structural analysis using high-resolution mass spectrometry (HRMS) and 1H,13C NMR techniques enabled the identification of pent-4-enenitrile. Variation in essential oil composition and yields was studied according to harvesting time, drying, and parts of the plant. The essential oil of aerial parts was tested for its antibacterial activity using a paper disk method. The oil was effective on the inactivation of Escherichia coli and Pseudomonas aeruginosa and ineffective on the inactivation of Staphylococcus aureus.     

Water properties in cream cheeses with variations in pH, fat, and salt content and correlation to microbial survival

Water mobility and distribution in cream cheeses with variations in fat (4, 15, and 26%), added salt (0, 0.625, and 1.25%), and pH (4.2, 4.7, and 5.2) were studied using (1)H NMR relaxometry. The cheese samples were inoculated with a mixture of Listeria innocua, Escherichia coli O157 and Staphylococcus aureus, and partial least-squares regression revealed that (1)H T(2) relaxation decay data were able to explain a large part of the variation in the survival of E. coli O157 (64-83%). However, the predictions of L. innocua and S. aureus survival were strongly dependent on the fat/water content of the samples. Consequently, the present results indicate that NMR relaxometry is a promising technique for predicting the survival of these bacteria; however, the characteristics of the sample matrix are substantial.     

Green-leaf-derived C6-aroma compounds with potent antibacterial action that act on both Gram-negative and Gram-positive bacteria

All eight C6-aliphatic alcohol and aldehyde compounds in naturally occurring green leaves showed bacteriostatic effects against Staphylococcus aureus IFO 12732, methicillin-resistant S. aureus, Escherichia coli IFO 3301, E. coli O157:H7, and Salmonella enteritidis, with bacteriostatic activities of less than 12.5 microg mL(-1). In this study, the susceptibility of Gram-positive bacteria tested was observed to be greater than that of Gram-negative bacteria. The bactericidal action of the aldehyde compounds was found to be much stronger than that of the alcohol compounds under both liquid and gaseous conditions. The most effective compound was (3E)-hexenal at concentrations of 0.1 and 1 microg mL(-1), which killed 2.1 x 10(5) cfu mL(-1) of S. aureus IFO 12732 and 1.4 x 10(5) cfu mL(-1) of E. coli IFO 3301, respectively, by direct contact with the compound. Lethality of (3E)-hexenal against S. aureus IFO 12732 and E. coli IFO 3301 was also observed as a result of gaseous contact at concentrations of 3 and 30 microg mL(-1), respectively. The bactericidal effects of 30 microg mL(-1) (3E)-hexenal were thoroughly maintained throughout periods of 2 days and 1 day against S. aureus IFO 12732 and E. coli IFO 3301, respectively, by a complex formation with alpha-cyclodextrin.     

鸵鸟异嗜白细胞抗菌肽的分离纯化及部分性质研究

目的：分离纯化出鸵鸟异嗜白细胞抗菌肽,并对其部分特性进行研究,为开发新一代高效肽类抗菌药提供依据。方法：使用氯化铵裂解、超声波破碎、醋酸提取、CM-Sepharose F F弱酸性阳离子交换层析和反相高效液相色谱（RP-HPLC）等方法,从鸵鸟异嗜白细胞中分离纯化出了抗菌肽,使用微量琼脂糖弥散法进行了抗菌活性与最小抑菌浓度（MIC）的测定,应用二级质谱（MS/MS）对抗菌肽的分子量进行测定。结果：在鸵鸟异嗜白细胞中存在抗菌肽,其对金黄色葡萄球菌S.aureus 1056MRSA、鸡大肠杆菌E.coli O78和白色念珠菌C.albicans ATCC10231具有较强的抑制作用;抗菌肽具有阳离子性质;热稳定性良好;经RP-HPLC纯化得到峰6、峰16和峰24,峰6对白色念珠菌的MIC为0.065μg/mL,峰16的分子量为4012.472Da,对鸡大肠杆菌和金黄色葡萄球菌的MIC分别为3.971μg/mL和5.245μg/mL,峰24的分子量为3542.479Da,对鸡大肠杆菌和金黄色葡萄球菌的MIC分别为26.472μg/mL和21.561μg/mL。结论：本研究得到的抗菌肽与已报道的鸵鸟抗菌肽ostricacins相比显示出更强的抑菌活性,是否为同一物质需要进一步的验证。     

Thermal inactivation of mushroom polyphenoloxidase employing 2450 MHz microwave radiation.

Browning reactions in fruits and vegetables are a serious problem for the food industry. In mushrooms, the principal enzyme responsible for the browning reaction is polyphenoloxidase (PPO). A microwave applicator has been designed and used for studying mushroom PPO inactivation. The effects of microwaves and conventional heating on the kinetics of the monophenolase and diphenolase activities of PPO were studied. Conventional and microwave treatments produce different enzyme intermediates with different stability and kinetic properties. We describe how considerable time can be saved during microwave inactivation of the enzyme compared with the time needed when conventional hot-water treatment is used, resulting in greater profitability and enhanced quality. The short exposure time required for samples irradiated with microwaves is very important for maintaining the quality of mushrooms. The fast microwave treatment used resulted in an increase in antioxidant content and a considerable decrease in browning.     

Thermal inactivation of pectin methylesterase,polygalacturonase, and peroxidase in tomato juice

Thermal inactivation kinetics have been determined for pectin methylesterase (PME), polygalacturonase (PG), and peroxidase (POD) in tomato juice. Two parameters, the inactivation rate constant (k) at a reference temperature and the activation energy for inactivation (E(a)), were determined for each enzyme. For PME and PG, the k and E(a) values reported here do not agree with those in several previously published reports. These differences can be explained either by the differences in pH values used for inactivation determinations or by inadequacies in the heating methods used in some previous studies. POD showed simple first-order inactivation kinetics and was less thermally stable than either PME or PG. When different cultivars of tomatoes were evaluated, there was no difference in the thermal inactivation kinetics of these enzymes.     

Chemical composition and antibacterial activity of essential oils from Thymus spinulosus Ten. (Lamiaceae)

The chemical composition of essential oils from aerial parts of Thymus spinulosus Ten. (Lamiaceae) is reported. Four oils from plants growing in different environmental conditions were characterized by GC and GC-MS methods; the oils seem to indicate a new chemotype in the genus Thymus. Influences of soil and altitude characteristics on the essential oil composition are discussed. The oils showed antibacterial activity against Gram-positive (Staphylococcus aureus, Streptococcus faecalis, Bacillus subtilis, and Bacillus cereus) and Gram-negative (Proteus mirabilis, Escherichia coli, Salmonella typhimuium Ty2, and Pseudomonas aeruginosa) bacteria.     

Inhibition of pathogenic bacterial adhesion by acidic polysaccharide from green tea (Camellia sinensis)

An acidic polysaccharide CS-F2 from Camellia sinensis was examined to characterize its anti-adhesive effects against pathogenic bacteria, most notably Helicobacter pylori, Propionibacterium acnes, and Staphylococcus aureus. CS-F2 showed marked inhibitory activity against the pathogen-mediated hemagglutination with a minimum inhibitory concentration (MIC) between 0.01 and 0.1 mg/mL, which is lower than the previously reported MIC values for Panax ginseng and Artemisia capillaris. The inhibitory effects of CS-F2 on the adhesion of H. pylori to AGS adenocarcinoma gastric epithelial cells, or P. acnes and S. aureus to NIH 3T3 fibroblast cells, were further assessed resulting in MIC values between 0.063 and 0.13 mg/mL. Importantly, CS-F2 showed no inhibitory effects against Lactobacillus acidophilus, Escherichia coli, or Staphylococcus epidermidis. Our results suggest that CS-F2, which is a pectin-type polysaccharide with a molecular weight of approximately 8.0 x 10(4) Da, may exert a selective anti-adhesive effect against certain pathogenic bacteria, while exerting no effects against beneficial and commensal bacteria.     

Antimicrobial and bactericidal activities of esters of 2-endo-hydroxy-1,8-cineole as new aroma chemicals

Fourteen kinds of alkyl esters of 2-endo-hydroxy-1,8-cineole were synthesized, with yields of 57.8-98.0%. Each ester had a characteristic and unique odor. Especially, the tert-butyl acetate of 2-endo-hydroxy-1,8-cineole had the most interesting odor of all the synthetic esters. The antimicrobial and bactericidal activities of these synthetic esters against test bacteria (Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescens) were examined using the broth dilution method. As a result, the tert-butyl acetate of 2-endo-hydroxy-1,8-cineole showed the highest antimicrobial and bactericidal activities against all kinds of the test bacteria.