Processing concepts based on high intensity electric field pulses

Emerging non-thermal food processing techniques are receiving considerable attention. This is because of their potential for quality and safety improvement of our food supply, for the ability to enhance conventional processing operations or to create alternative ones, as well as modify existing or non-conventional raw materials, food constituents or processed foods. High intensity electric field pulse technology is one of the most advanced emerging non-thermal processing methods and is currently undergoing intensive scientific and developmental evaluation. The objectives of this review are to summarize and identify the key advantages of this emerging technology and to convert it into optimum use. Those attempts are a combination of research on a kinetic basis and on a cellular level and the subsequent transfer of the knowledge gained into pilot scale.     

高场强脉冲电场在胡萝卜汁加工中应用的研究

研究高场强脉冲电场 (HEFP)的产生及其处理胡萝卜浆提高出汁率的机理 ,探讨处理后的胡萝卜汁的营养成分、外观、色泽、风味的变化情况。     

Impact of high intensity electric field pulses on cell permeabilisation and as pre-processing step in coconut processing

The impact of high intensity electric field pulses (HELP) for cell permeabilisation of coconut was studied. A preliminary investigation of suitable field strength and total energy input for HELP treatment (field strength, 0.1–2.5 kV/cm, number of pulses, 0–200, pulse width, 575 μs and pulse frequency 1 Hz) was carried out. A comparison of the HELP process (E=2.5 kV/cm, n=20 pulses, t=575 μs and frequency 1 Hz) was made with other methods of cell disintegration (e.g. mechanical rupture, thermal treatment, freeze-thaw cycle) on the yield of coconut milk obtained and its protein and fat contents. A combination of HELP treatment and centrifugation (10 000×g for 10 min) was employed as pre-processing step prior to coconut dehydration in a fluidised bed dryer (60°C, air velocity 1 m/s) in an attempt to enhance drying rates. Treatment with HELP under suitable conditions (E=2.5 kV/cm, n=20 pulses, t=575 μs and frequency 1 Hz) resulted in 20% increase in milk yield with reference to the untreated samples. The fat contents of the extracted milk from HELP treated and untreated samples were 58.0% and 61.2%, respectively, and the corresponding protein contents of the aqueous medium after separation by centrifugation were 50.0% and 51.6%. The combination of HELP and centrifugation step resulted in a reduction of approximately 22% of the drying time as compared to the untreated samples which could be of advantage in the production of copra.     

Effect of electric field pulses on microstructure of muscle foods and roes

The effect of pulsed electric fields (PEF) and combination of PEF and high pressure were studied on microstructure of salmon, chicken and lumpfish roes. The results showed that PEF treatment with low field strength (less than 2 kV/cm and 20–40 pulses) had considerable effect on the microstructure, i.e. the muscle cells decreased in size and gaping occurred. PEF treatment had greater effect on salmon than chicken samples. However, roes seem to tolerate up to 18.6 kV/cm and seven pulses without visible effect. Reduction of microorganisms was still not sufficient at the same time. Combination of PEF and high pressure (200–300 MPa) had more detrimental effect on microstructure than PEF treatment alone.     

高压脉冲电场对食品微生物、酶及成分的影响

高压脉冲电场加工是一种非热杀菌技术,是指在高电场强度、短脉冲和温和的温度下处理食品。与传统的热杀菌比较,它具有很多优点,不仅能杀死微生物钝化酶类,而且能保持食品的营养成分和新鲜度。本文综述了高压脉冲电场对食品的杀菌效果、杀菌机制、影响杀菌的因素以及对食品中酶类和成分的影响。      

高压脉冲电场技术制备大豆肽螯合钙

目的研究大豆肽螯合钙最佳工艺参数以及高压脉冲电场对螯合效果的影响。方法以鸡蛋壳粉和大豆肽粉为原料,以螯合率为衡量指标,研究了大豆肽粉和蛋壳粉的质量比、反应体系pH、螯合过程中电场强度以及电场的频率等因素对螯合反应的影响情况,并利用响应面试验设计的方法。结果回归方程为:Y=94.96-0.074X_1+0.30X_2-0.14X_3-0.45X_4+0.012X_1X_2+0.060X_1X_3+0.37X_1X_4-0.32X_2X_3+0.64X_2X_4-0.085X_3X_4-0.42X_1~2-0.93X_2~2-0.34X_3~2-0.15X_4~2,优化出大豆肽螯合钙的最佳工艺条件为:大豆肽粉和蛋壳粉质量比1:1.75、pH 8.0、电场强度15 kV/cm、电场频率1200 Hz。在此条件下,螯合率高达95.38%±0.18%。结论本研究为大豆肽螯合钙技术研究提供一种新思路。     

Effects of high voltage electric field on storage life and antioxidant capacity of whole pomegranate fruit

The objective of this study was to investigate the effects of high voltage electric field (HVEF) on the antioxidant system in stored pomegranate fruit. The experiments were conducted at cold storage for two months under three selected electric field levels (0, 1.5 and 3 kV/cm). Results showed that non-enzymatic antioxidant contents including phenols and ascorbic acid were better preserved by 1.5 kV/cm treatment than control after 60 days of storage. While the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in pomegranate fruit were significantly enhanced with 1.5 kV/cm treatment compared to control, Guaiacol peroxidase (G-POX) levels in the control group increased steadily and were highest at the end of the storage. Although the results obtained from 3 kV/cm treatment were acceptable till the end of the first month, due to oxidative damage of reactive oxygen species (ROS) produced in response to HVEF stress, their results come close to the control group at the end of the second month. These data suggest that the optimum electric field intensity for enhancing antioxidant contents in stored pomegranate fruits was 1.5 kV/cm.     

Effects of high intensity pulsed electric field and thermal treatments on a lipase from Pseudomonas fluorescens

Milk and dairy products may contain microorganisms capable of secreting lipases that cause sensory defects and technological problems in the dairy industry. In this study, the effects of thermal and high-intensity pulsed electric field (HIPEF) treatments on an extracellular lipase from Pseudomonas fluorescens, suspended in a simulated skim milk ultrafiltrate (SMUF) have been evaluated. Heat treatments applied were up to 30 min from 50 to 90 degrees C. HIPEF treatments were carried out using pilot plant facilities in a batch or continuous flow mode, where treatment chambers consisted of parallel and coaxial configuration, respectively. Samples were subjected to up to 80 pulses at electric field intensities ranging from 16.4 to 37.3 kV/cm. This resulted in a lipase that was quite resistant to heat and also to HIPEF. High (75 degrees C-15 s) and low pasteurization treatments (63 degrees C-30 min) led to inactivations of 5 and 20%, respectively. Using the batch-mode HIPEF equipment, a 62.1% maximum activity depletion was achieved after 80 pulses at 27.4 kV/cm. However, when HIPEF treatments were applied in the continuous flow mode, an inactivation rate of just 13% was achieved, after applying 80 pulses at 37.3 kV/cm and 3.5 Hz. The results of both heat and HIPEF treatments on enzyme inactivation were adjusted with good agreement to a first-order kinetic model (R2 > 62.3%).     

高压脉冲电场对美拉德反应的影响

建立了葡萄糖/甘氨酸(Glu/Gly)模拟体系,从模拟溶液pH、电场强度、脉冲数、贮藏期四方面研究了高压脉冲电场对葡萄糖/甘氨酸模拟溶液美拉德反应的影响。结果表明:场强为28kV/cm,pH为7.96时,PEF处理对葡萄糖/甘氨酸模拟溶液的美拉德反应有显著的促进作用,这种促进作用与其热效应无关,若电场强度小于24kV/cm,PEF处理对美拉德反应无显著影响。不同脉冲个数对于反应的影响差异不显著。PEF处理后的模拟溶液美拉德反应程度随贮藏时间的延长和贮藏温度的升高而逐渐增强,且比未处理组显著。      

高压电场干燥牛肉技术研究

目的:探讨一种新型的干燥技术来提高牛肉干制品的品质;方法:以熟牛肉为对象进行高压电场干燥试验,在不同形状电极下进行干燥试验;结果:高压电场能够干燥熟牛肉,且干燥速度随电压升高而升高,针状电极下的干燥速度大于平板状电极下的;结论:高压电场干燥技术是牛肉干制品领域里一项实用、有效的新型技术.     

高频电场对毛霉蛋白酶活力的影响

本文研究不同的电场强度、频率、波形、处理时间及不同的介质对毛霉蛋白酶活力的影响。在一定范围内，电场有提高酶活力的作用。在含盐7％的酒水中，酶的活力受到抑制；但经电场处理后，在此介质中酶活的增长率最大的达20％，优于以水为介质的情况。     

高压电场对SOD活性的影响及其紫外光谱研究

利用不同电场强度处理超氧化物歧化酶(Superoxide dismutase,SOD),测试高压电场处理前后酶的活性和紫外光谱。结果表明:高压电场可使酶活性降低,其紫外光谱测试表明,不同电场强度可以改变酶的构象。酶活性的降低可能是由酶构象的改变引起。研究结果对解释静电宏观生物效应具有重要意义。     

交变电场在还原染料电化学还原染色中的增效作用研究

采用自制的间接电化学还原染色装置将还原艳绿FFB还原成隐色体钠盐,在染色过程中加以交变电场,从而促进还原染料隐色体上染纤维,研究了电场强度、温度和pH、染色时间对染色效果的影响。结果表明：在电场强度1600N／C、pH11．5、染色温度45℃的条件下染色,9min即可达到染色平衡,染色K／S值最高可达20．07,在相同染料浓度下较常规电化学还原染色和传统还原染料染色高,且湿摩擦牢度和皂洗牢度可提高0．5—1级。     

Effects of pulsed electric field on freeze-thaw quality of Atlantic salmon

Freezing and thawing have unexpected impacts on quality of Atlantic salmon, and efforts are needed to reduce side-effects of these processes. In order to evaluate the effects of pulsed electric field (PEF) treatment on quality of frozen-thawed salmon, the indicators associated with quality of PEF-treated (1.0 kV/cm) samples were compared with those of samples frozen and thawed without external treatment (control). Results showed that the application of PEF decreased the thawing time by 20 min from −2 °C to 0 °C. The muscle fiber of PEF-treated sample was preserved better after thawing, resulting in the total loss reduced by 6%. Sample texture and TVB-N content (12.51 mg/100 g less) showed positive effects as a result of PEF treatment. However, b value and lipid peroxidation were slightly increased due to the oxidation effect of PEF. It can be concluded the rational application of PEF has potential of extending freshness of frozen-thawed Atlantic salmon.     

Effect of high intensity pulsed electric fields on enzymes and vitamins in bovine raw milk

Pulsed electric fields (PEF) were applied to fresh bovine raw milk using a laboratory-scale continuous PEF system to study the impact on selected native enzyme activities and on vitamin degradation. The activities of protease, lipase, alkaline phosphatase and lactoperoxidase following PEF treatment at electric field strengths ranging from 15 to 35 kV/cm for treatment times of 12.5 µs to 75 µs were examined. Reductions in enzyme activity, even under the most severe conditions employed, were quite modest, amounting to 14%, 37% and 29% for lipase, protease and alkaline phosphatase, respectively, while the activity of lactoperoxidase remained unchanged. The PEF treatment had no effect on the levels of thiamin, riboflavin, retinol and α-tocopherol in the milk .     

Effects of high pressure treatment on the proteolytic enzymes in meat

This paper describes the effects of high-pressure treatment on proteolytic enzymes in muscle, especially catheptic enzymes which influence meat tenderization, and on acid phosphatase, used as an index of disruption of lysosomal membranes. Acid phosphatase activity in the extract from pressurized muscle increased with increasing pressure applied to the muscle up to 500 MPa. Activity of cathepsin B, D and L increased up to 400 MPa, then tended to decrease at 500 MPa. Cathepsin H and aminopeptidase B decreased with the increasing pressure. Measurements of enzymic activity in the pressurized crude extract, to investigate the pressure effect on the enzymes themselves, showed that all enzymes studied in this paper lost their enzymic activity as applied pressure increased. When the pressurized extracts were subjected to the gel-filtration chromatography, a decrease in the activities of cathepsin H and aminopeptidase B and an increase in the activities of cathepsins B and L and acid phosphatase were observed. It seems that the decrease in activity of the enzymes eluted early from the column (cathepsin H and aminopeptidase B) is due to decrease in the amount of protein eluted by the pressure treatment, whereas the increase in activity of the enzymes eluted late (cathepsin B, L and acid phosphatase) is due to an increase in the amount of protein eluted. From the results, it was concluded that the pressure-induced increase in the amount of protease activity in the muscle was due to the release of the enzymes from lysosomes.     

高压脉冲电场对干红葡萄酒色度的影响

通过改变电场强度,研究高压脉冲电场对新鲜干红葡萄酒色度的影响.结果表明：处理后酒样的色度有一定程度的提高,其变化趋势基本符合陈酿效果.     

高强脉冲电场与臭氧联用降解壳聚糖

利用臭氧的强氧化性和电场的高能量降解大分子壳聚糖为壳寡糖。在乙酸均相体系中,高强脉冲电场与臭氧联用处理壳聚糖30min时,壳聚糖的降解率达到98．5％。设计了脉冲电场、臭氧单独处理和电场与臭氧联用处理3种实验方案,结果表明：电场与臭氧联用的处理效率要高于分别处理效率,电场与臭氧联用具有协同作用。经红外光谱分析,降解产物与原料壳聚糖结构基本一致。     

高压静电场解冻对冻罗非鱼片品质的影响

本文以冻罗非鱼片为研究对象,分析了不同高压静电场（0、1.8、3.8 k V）、不同解冻温度（25、15、5℃）条件下解冻,其解冻曲线、解冻时间和解冻速率的变化情况;并以解冻损失率、菌落总数、感官品质、色差值、总挥发性盐基氮（TVB-N）、脂质氧化（TBA）等为衡量指标,研究了高压静电场解冻对罗非鱼片品质指标变化影响。结果显示,对各解冻温度组,3.8 k V高压静电场解冻速率更快,解冻时间更短,在5℃时,3.8 k V高压静电场解冻速率是对照组速率的1.59倍;高压静电场解冻后鱼片TVB-N值和菌落总数都显著低于对照组,15℃时,3.8 k V高压静电场解冻候的菌落总数为4.29 log CFU/g显著低于对照组的4.67 log CFU/g（p<0.05）;总体上高压静电场解冻不仅可以加速冻罗非鱼片的解冻,而且能更好地保持鱼肉的品质,从解冻速率和品质指标综合考虑,15℃、3.8 k V高压静电场解冻是最佳的选择。