高氧化还原电位水对虾的保鲜效果

通过研究高氧化还原电位水(EOW)不同温度和不同作用时间对虾杀菌效果和品质的影响,确定最佳处理条件。将EOW作用的虾4℃保藏,通过测定细菌总数、pH和挥发性盐基氮(TVB-N)等鲜度指标评价保鲜效果。结果表明,EOW电解15min最佳,结合50℃水浴作用5min使细菌总数有效降低2～3个对数值,同时发现4℃保藏,可使虾的保鲜期延长2d,证明EOW和温度协同作用可以有效延长虾的保鲜期。     

电子束辐照对糯米糍荔枝采后保鲜效果的研究

以深圳南山糯米糍荔枝为原料,通过电子加速器辐照,使用0.5、1.0、1.5和2.0 k Gy 4个剂量处理后分别于室温下(26℃~30℃)贮藏3 d,低温(4℃±1℃)下贮藏15 d。以褐变率、失重率、质构、维生素C含量、可溶性固形物等为品质指标,研究不同辐照剂量处理对鲜荔枝保鲜期的影响。结果表明,不同剂量辐照后,各组荔枝外观与对照组均无显著差别。室温下电子束辐照可以使糯米糍荔枝的保鲜期从1 d延长至3 d,4℃冷藏条件下保鲜期可从10 d延长至15 d。0.5 k Gy为最佳辐照剂量,照射剂量在1.5 k Gy以上会加快荔枝外观和营养品质的劣变。     

高压静电场对桔青霉菌的作用效果与机理

利用自制高压静电场装置,对桔青霉菌进行不同场强度、时间及温度的处理来考察高压静电场对其孢子萌发率的作用效果;用典型作用参数处理观察青霉菌芽管长度、接种于健果上的菌斑大小及孢子形态来进一步验证对萌发率作用结果及作用机理的探讨。结果表明,高压静电场对青霉菌孢子的萌发具有促进和抑制两种完全不同的作用。场强小于40000V/m和处理时间小于20min能促进孢子萌发,场强大于62000V/m和处理时间超过60min能抑制孢子萌发,中间剂量的处理效果依据不同的处理而有所变化。温度对电场处理效果有着显著的影响,当温度升高到50℃,高剂量的场强处理可以完全抑制青霉菌孢子萌发。高压静电场对青霉菌的芽管长度、桔果上的菌斑大小的作用有着相似的结果。62000V/m、60min的处理使青霉菌的孢子形态结构受损,导致其孢子失去萌发能力。结果表明高压静电场为柑橘类的果蔬保鲜提供了一条物理处理新途径。     

不同保鲜方式对牡蛎品质及烹饪效果影响研究

以牡蛎为原料,研究了经臭氧处理与超高压处理等不同处理方式对牡蛎保鲜贮藏期间微生物、pH、TVB-N以及烹饪后感官评分的变化情况。结果表明,牡蛎经2.36 mg/L质量浓度臭氧处理5, 10和15 min,及在23.5℃环境下,分别用250, 300和350 MPa超高压处理20 min,都具有一定延长保鲜期作用,臭氧处理在相同浓度下,处理时间越长,其保鲜效果越好,超高压处理在相同时间情况下,压力越大,保鲜效果越好。超高压处理方式优于臭氧处理。     

减菌化预处理对鲜鱼冷藏保鲜的影响

用酒精消毒远红外线脱水，紫外线减菌，真空包装作为预处理在子，对鲜活鲫鱼宰杀后进行减菌处理，然后在4℃下冷藏保鲜，贮藏期内通过感官评定pH值，TVBN含量，细菌总数的测定，结果表明这四个预处理因子的协同作用对延长鲫鱼的保鲜期有明显的效果。酒精消毒后在40℃下远红外脱水10min，紫外线杀菌20min，再进行真空包装冷藏，可以使鲫鱼的保鲜期延长至14d。     

高压静电场处理对甘薯采后愈伤的促进效应

为探讨高压静电场处理对甘薯采后的愈伤效应，在单因素实验的基础上，根据Box-Behnken中心组合实验设计原理，以木质素含量为响应值，优化处理参数。结果表明，高压静电场促进甘薯愈伤的最佳作用条件为：电场强度800.0 KV·m-1、电场时间10.0 h、作用温度26.0 ℃。在此条件下，木质素含量为4.82%，与理论预测值相比，误差为0.2%。影响木质素合成的高压静电场处理影响因素为：作用温度＞作用时间＞电场强度。愈伤期间，相对于对照组，高压静电场处理可以使甘薯受损部位间苯三酚染色更深；高压静电场处理的相对电导率和MDA含量均显著更低，更有利于保护细胞膜。可见，高压静电场处理能提高受损甘薯愈合速度。     

高压静电场连续处理香蕉的品质变化规律研究

通过研究温度在20℃左右,相对湿度为40%的环境下,香蕉果实在连续高压静电场处理过程中品质的变化规律。结果表明:处理组香蕉果实可溶性固形物含量、过氧化物酶活性和果胶酶活性高于对照组,淀粉含量、VC含量和果肉硬度低于对照组,同时连续高压静电场处理使香蕉果实乙烯释放高峰和呼吸高峰提前3d出现。说明连续高压静电场处理可促使香蕉果实成熟,并且-150kV/m处理组的催熟效果好于-100kV/m处理组。     

微波杀菌保鲜面包的技术研究

面包是当今社会人们所衷爱的方便食品之一,但其在室温下保鲜期通常只有3-4d。本实验以当天焙烤的新鲜面包片为原料,经适当的微波杀菌处理后分别置于室温、冷藏(0-4℃)条件下保藏,确定适宜的保鲜期。实验结果表明,微波杀菌面包在室温下保鲜期为12d,冷藏条件下保鲜期为20d;而未经微波杀菌处理的面包在冷藏条件下保鲜期只有12d,说明适宜的微波杀菌处理有利于延长面包的保鲜期。     

高压静电场对大肠杆菌蛋白酶活力的影响

利用自制的试验装置,探讨了直流高压静电场对大肠杆菌蛋白酶活力的影响,结果表明:高压静电场对蛋白酶活力的影响有活化和钝化两种情况。电场强度为0～10kV/3cm场强范围,酶活力提高,在30℃,场强3kV/3cm,处理15min,最大能提高29.9%,而超过10kV/3cm后,酶活力逐渐降低,降幅可达13.2%。     

高压静电场对青霉菌的影响

以苹果霉腐病中青霉菌为材料通过高压静电场(HVEF)进行不同时间的处理,比较处理的孢子菌悬液在不同培养温度下的萌发和产孢量,将处理后的孢子菌悬液接种于苹果,观察苹果的感病率及病斑直径。结果表明：同一温度下培养,高压静电场处理的与未处理菌悬液的孢子萌发率相差不大,但萌发时间滞后;产孢量与处理时间相关,处理30min 后,在20℃培养7d 产孢量要比处理15min 和未处理的低。与对照相比,接种处理的孢子菌悬液的苹果感病率较低,病斑直径较小。     

Thermal Diffusivity Variation Study of Cold Stored Malaysian Pangasius Sutchi at 10°C

This paper presents the use of thermal diffusivity-variation of Malaysian Pangasius Sutchi freshwater fish as a criterion to estimate the freshness in fish marketing. A homogenous specified area of a fresh fish body was cut into slices which were wrapped and preserved in a cold store of 10°C for a period of 28 days. Ansari's approach has been found earlier as an appropriate one to measure the thermal diffusivity of fish through transient cooling. The daily measurement of those slices (samples) along the muscle orientation revealed that thermal diffusivity increased up to 3 days then stayed approximately constant up to the end of the preservation period (28 days). In the literature the shelf life was also found 3 days at 10°C, which in turn agreed with the present investigation. Regression analysis was made to develop an empirical correlation between thermal diffusivity ratio and preservation time of the fish under study. This correlation could be used by food technologists as an index of deterioration of freshness or consumer acceptance     

The effect of certain antibiotics on bolti fish (Tilapia nilotica) preservation

The shelf life of bolti fish (Tilapia nilotica) caught in the river Nile, has been successfully prolonged for about 9 days by dipping in tetracycline (TC) or nisin solution followed by refrigeration, although the initial microbial contamination in the fresh fish was very high. The caught fish were gutted and treated with 10 and 20 ppm TC solutions for 10 and 15 min by dipping, and with 500 and 1000 R.U. nisin/g fish for 20 and 30 min. The treated and control fish samples, were stored and refrigerated at (4 +/- 1) degree C for 12 days. Total bacterial counts, the most probable number of coliform bacteria and lactic acid bacteria in the fish treated with TC or nisin, were lower than those of the control, especially at 20 ppm TC, 15 min dipping, and 1000 R.U. nisin/g, 30 min. Further more TC was more effective against yeasts and moulds. This result suggest that antibiotics would help in transporting chilled fish from the highdam lake in Aswan to Cairo (about 900 km). According to the present results it may be recommended to use the antibiotic TC, with the concentration of 20 ppm for 15 min dipping, for prolonging the shelflife of bolti fish. The presence and increase of coliform bacteria in fish, draw the attention to the necessity of hygienic measures when dealing with such fish until to the consumption.     

苜蓿营养挂面的制作工艺初探

新鲜苜蓿经处理后,加入到100℃的含0.015%醋酸锌和0.3%的碳酸钠混合液中,烫漂3min,加工成浆糊状,用5%环糊精包埋2d,按15%的比例加入到面粉中并加2%的活性面筋粉、2%食盐、0.2%海藻酸钠改善挂面品质,可制得营养丰富的绿色挂面制品,能较长时间保持绿色不变。     

Extraction Using Moderate Electric Fields

ABSTRACT: During moderate electric field (MEF) processing, a voltage applied across a food material may affect the permeability of cell membranes. It is known that high electric fields can cause either reversible or irreversible rupture of cell membranes. In this research, the effect of MEF processing on permeability was studied. Effects of frequency and electric field strength were investigated. Cellular structure was investigated by transmission electron microscopy (TEM). Fermented black tea leaves and fresh or dry mint leaves were placed in tea bags or cut in 1 cm² squares, depending on the experiment, and immersed in an aqueous fluid medium. Control samples were heated on a hot plate. MEF treatments were conducted by applying a voltage across electrodes immersed in opposite sides of the beaker. Control and MEF‐treated fresh mint leaf samples heated to 50°C were analyzed by TEM. MEF processing significantly increased the extraction yield for fresh mint leaves because of additional electric field effects during heating. Dried mint leaves and fermented black tea leaves were not affected by the treatment type. Low frequency resulted in higher extraction rates for fresh mint leaves. The electric field strength study showed that electrical breakdown is achieved even at low electric field strengths. MEF treatment shows potential to be used as an alternative to conventional heating for extraction from cellular materials.     

Reduction in levels of Escherichia coli O157:H7 in apple cider by pulsed electric fields.

Many studies have demonstrated that high voltage pulsed electric field (PEF) treatment has lethal effects on microorganisms including Escherichia coli O157:H7; however, the survival of this pathogen through the PEF treatment is not fully understood. Fresh apple cider samples inoculated with E. coli O157:H7 strain EC920026 were treated with 10, 20, and 30 instant charge reversal pulses at electric field strengths of 60, 70, and 80 kV/cm, at 20, 30, and 42 degrees C. To accurately evaluate the lethality of apple cider processing steps, counts were determined on tryptic soy agar (TSA) and sorbitol MacConkey agar (SMA) to estimate the number of injured and uninjured E. coli O157:H7 cells after PEF treatment. Cell death increased significantly with increased temperatures and electric field strengths. A maximum of 5.35-log10 CFU/ml (P < 0.05) reduction in cell population was achieved in samples treated with 30 pulses and 80 kV/cm at 42 degrees C. Cell injury measured by the difference between TSA and SMA counts was found to be insignificant (P > 0.05). Under extreme conditions, a 5.91-log10 CFU/ml reduction in cell population was accomplished when treating samples with 10 pulses and 90 kV/cm at 42 degrees C. PEF treatment, when combined with the addition of cinnamon or nisin, triggered cell death, resulting in a reduction in E. coli O157:H7 count of 6 to 8 log10 CFU/ml. Overall, the combination of PEF and heat treatment was demonstrated to be an effective pasteurization technique by sufficiently reducing the number of viable E. coli O157:H7 cells in fresh apple cider to meet U.S. Federal Drug Administration recommendations.     

新鲜葡萄酒高强电磁场人工催陈研究

通过采用高强电场处理设备对2002年产新鲜干红葡萄酒进行了人工催陈研究，发现当处理电场强度为3KV／cm，频率为1000Hz，处理时间5min时，与对照相比，酒体变得陈香明显加强，口感柔和协调，更加饱满。     

超高压处理对冰温保鲜牛肉品质的影响

以西门塔尔牛肉为原料,研究150 MPa超高压处理对冰温保鲜牛肉品质的影响,为开发新型牛肉保鲜方式提供参考。结果表明：经过150 MPa超高压在20 ℃条件下处理15 min后的冰温贮藏过程中,牛肉的感官评分高于对照组,质构、蒸煮损失率、pH值等指标的变化趋势均慢于对照组,超高压处理牛肉的贮藏期可达到32 d,比对照组延长7 d。超高压处理有利于延长牛肉的冰温保鲜时间。     

半胱氨酸处理对采后金针菇品质和抗氧化活性的影响

为了研究半胱氨酸处理对金针菇低温贮藏品质和抗氧化活性变化的影响,将新鲜金针菇分别采用15 mmol/L半胱氨酸和清水浸泡处理20 min后于2~3 ℃贮藏12 d,并定期检测相关理化指标。结果表明,15 mmol/L半胱氨酸处理能够抑制新鲜金针菇的呼吸强度和褐变度;延缓可溶性固形物和可溶性蛋白含量下降,并保持较低相对电导率;抑制了多酚氧化酶（polyphenol oxidase,PPO）活性和过氧化物酶（peroxidase,POD）活性,并保持较高的总酚和抗坏血酸含量,贮藏结束时,半胱氨酸处理组的PPO和POD活性比对照组分别降低了13.78%和26.49%,总酚和抗坏血酸含量分别为对照组的1.12和1.37倍;处理组提高了超氧化物歧化酶（superoxide dismutase,SOD）活性、谷胱甘肽还原酶活性以及1,1-二苯基-2-三硝基苯肼自由基（1,1-diphenyl-2-picrylhydrazyl,DPPH）清除率,对失重率无显著影响;相关性分析发现,处理组的呼吸强度与SOD活性、DPPH自由基清除率相关系数分别为?0.951和?0.903,呈显著（P<0.05）负相关。由此得出,低温贮藏期间,半胱氨酸处理能够降低金针菇内部物质的代谢速率,维持较高抗氧化能力和感官品质。