Effect of static electric field on ice crystal size reduction during freezing of pork meat

The objective of this research was to evaluate the influence of static electric field (SEF) on the freezing of pork meat (pork tenderloin muscle) with respect to the size of ice crystal formulation. The results showed that by increasing the strength of the static electric field, the degree of supercooling was reduced. The measured degree of supercooling varied from 3.93 ± 1.3 °C to 1.92 ± 1.45 °C for the control and the frozen sample under 12 kV SEF, respectively. Meat microstructure was investigated after Carnoy fixation of the frozen tissues. The overall relative surface of the ice crystals was unchanged. The average equivalent circular diameter of the ice crystals was significantly reduced with increasing SEF; values from 32.79 ± 4.04 μm for the control to 14.55 ± 8.20 μm for the sample frozen at the maximum magnitude electric field which was tested were observed respectively. These findings demonstrate clearly the advantage of freezing under SEF which appears as a promising and innovative freezing process for food systems.Industrial relevanceThe reduction of freeze damage exerted to any tissue undergoing freezing remains a challenge. The mechanical and biochemical stress caused by the ice crystals to the cellular membranes results in irreversible tissue damage. Freezing under static electric field (SEF) has been identified as a possible means to reduce the size of ice crystals during freezing of biological tissues. In the present study SEF was applied during freezing of pork meat. Our results indicate that the size of the formed ice crystals was significantly reduced under SEF freezing leading to a lower damage on the microstructure of meat. This paper describes an innovative freezing process that could be used in order for higher quality frozen products to be produced.     

高压静电场处理对几种呼吸跃变型果实呼吸强度的影响

以苹果等几种呼吸跃变型果实为试材,研究了100kV/m的高压静电场每天处理2h对其呼吸强度变化规律的影响并与相同条件下的对照果进行了比较,发现高压静电场处理能够有效地降低这几种果实呼吸强度的最大值,并不影响它们呼吸高峰出现的时间。     

Designing of high voltage electric field for soybean and sunflower oil bleaching

To the best of our knowledge, this work for the first time in the world carried out at the Tarbiat Modares University. In the present research, high voltage electric field (HVEF) method was utilized for bleaching of soybean and sunflower oil. For optimization of the bleaching process, the effect of different independent variables such as clay percentage (0.5–2%), voltage (0–24 kV), distance (8–12 mm), different numbers of cathode–anode (4–8) and inert-electrolyte (HCl; 0–50 mM) was studied. In order to compare the properties of the bleached samples using HVEF and control (industrial condition) bleaching methods, the indexes of Lovibond, Hunter lab, carotenoid, chlorophyll, bleaching efficiency (BE), peroxide (PV), tiobarbituric acid (TBA), free fatty acid (FFA), tocopherol, sterol and fatty acid composition were measured. According to the results, the BE value of HVEF technique in bleached soybean (88.35%) and sunflower oil (75.41%) were higher in comparison with the soybean (85.80%) and sunflower (58.14%) oils bleached using control method. Consequently, the HVEF bleaching method seems to be an alternative to the industrial method as it reduced clay percentage (50 and 66%), temperature (28% and 28%) and process time (35% and 35%) in soybean and sunflower oil bleaching, respectively.Industrial relevanceHigh voltage electric field (HVEF) method for bleaching of soybean and sunflower oil was done, for the first time in the world to the based of our knowledge, and was optimized under different conditions including clay percentage (0.5–2%), voltage (0–24 kV), distance (8–12 mm) with different numbers of cathode–anode (0–8), inert electrolyte (HCl; 0–50 mM). HVEF could be an alternative for bleaching method in the oil industry; HVEF could reduce %clay, temperature and time consumption in oil industry with low energy consumption; HVEF could produce micro and Nano clay by pulsed corona and pulsed spark type systems.-To Patent No: A23D; C11B; C11C; H03, “Design of high voltage electric field for the oil bleaching”, Tehran-Iran (2015).     

不同冷冻方式对调理猪肉贮藏期品质影响的对比研究

本文以猪肉为主要原料,添加适量的调味料或辅料,经适当加工,使预冷12h后,中心温度约为10℃的调理猪肉通过风冷冷冻和浸渍式冷冻两种方式对其进行处理,将其中心温度分别降至-5、-18℃,然后把-5、-18℃的肉块放入相应温度的冰箱保藏,并对四种保藏处理下的调理猪肉在一定贮藏期内(24周)的保水性、滴水损失、蒸煮损失、质构特性、TVB-N、菌落总数、p H、色泽(L*a*b*)进行了对比研究。研究表明:四种冷冻处理下,-18℃组肉样的色差、TVB-N、TBA要显著低于-5℃组(p0.05),而巯基含量则显著高于-5℃组;其中浸-18℃组的菌落总数要显著低于其他组。且浸渍式冷冻工艺要优于风冷冷冻工艺,除保水性外,浸渍式冷冻组在色泽、菌落总数、挥发性盐基氮(TVB-N)、硫代巴比妥酸值(TBA)、质构特性等其他各项指标要优于风冷冷冻组。     

A comparative study on the structure of Saccharomyces cerevisiae under nonthermal technologies: high hydrostatic pressure, pulsed electric fields and thermo-sonication

Nonthermal technologies are becoming more popular in food processing; however, little detailed research has been conducted on the study of the lethal effect of these technologies on certain microorganisms. Saccharomyces cerevisiae is a yeast related to spoilage of fruit products such as juices; novel technologies have been explored to inactivate this yeast. Three nonthermal technologies, high hydrostatic pressure (HHP), pulsed electric fields (PEF) and thermo-sonication (TS), were used to evaluate and to compare the structural damage of yeast cells after processing. Processing conditions were chosen based on previous experiments to ensure the death of cells; HHP was conducted at 600 MPa for 7 min (room temperature, 21 °C); for PEF, 30.76 kV/cm at 40 °C and 21 pulses (2 μs each), and finally for TS the conditions were 120 μm, 60 °C and 30 min in continuous and pulsed modes; all treatments were applied in apple juice. Cells were prepared for electron microscopy using an innovative and short microwave assisted dehydration technique. Scanning electron microscopy showed the degree of damage to the cells after processing and illustrated the important and particular characteristics of each technology. Cells treated with high hydrostatic pressure showed a total disruption of the cell membrane, perforation, and release of the cell wall; scars were also observed on the surface of the pressurized cells. PEF treated cells showed less superficial damage, with the main changes being the deformation of the cells, apparent fusion of cells, the formation of pores, and the breakdown of the cell wall in some cells. Finally, the thermo-sonicated cells showed a similar degree of cellular damage to their structure regardless of whether the TS was applied continuously or pulsed. The main characteristics of cellular death for this technology were the erosion and disruption of the cellular membrane, formation of orifices on the surface, lysis of cells causing the release of intracellular contents, roughness of the cell membrane, and displacement of cell debris to the surface of other cells. This study confirms some theories about cell inactivation and presents new and detailed results about nonthermal technologies, but also shows that after using the above mentioned conditions, recovery of cells, specifically those that are pressurized and thermo-sonicated, it is not possible to do it following the high extent of damage observed in the entire population. Furthermore, a faster methodology that was used in sample preparation for electron microscopy provided high quality resolution images, allowing closer study of the detail of structural lethal effects on treated cells.     

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。     

高压静电场处理对冬枣和北京14号桃品质的影响

以冬枣和北京14号桃果实为原料,研究了100kV/m高压静电场处理对果实呼吸强度、细胞膜透性和果实可溶性固形物含量变化的影响。试验结果表明,高压静电场处理对果实的呼吸强度具有明显的抑制作用,电场处理使冬枣呼吸跃变推迟了70d,使北京14号桃的呼吸高峰降低了41.7%。高压静电场处理对冬枣和桃的果皮组织相对电导率的影响在贮藏前期和贮藏后期表现出不同的变化规律,贮藏前期电场处理组高于对照,贮藏后期电场处理组低于对照。同对照相比,高压静电场对冬枣和桃果实可溶性固形物含量的变化影响较小。     

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。     

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。      

Effect of high voltage electrostatic field treatment on thawing characteristics and post-thawing quality of frozen pork tenderloin meat

The thawing characteristics and post-thawing quality of frozen pork treated with high voltage electrostatic fields (HVEF) were compared with those of an air-thawed control. A multiple points-to-plate electrode operating at voltages above 6 kV significantly shortened the thawing time. Under electrode voltages 4, 6, 8, and 10 kV, thawing times were 70, 52, 46, and 40 min respectively, versus 64 min in the control. HVEF treatment was particularly effective in the temperature range −5–0 °C. HVEF treatment reduced the total microbial counts in thawed frozen meat by 0.5–1 log CFU/g, without affecting meat quality. During five days of post-thawing storage, the volatile basic nitrogen (VBN) levels increased from 10.64 to 16.38 mg/100 g under 10 kV applied voltage, while the control VBNs increased from 10.66 to 19.87 mg/100 g. This suggests an application potential for HVEF treatment in the thawing and storage of frozen meat.     

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.     

高压脉冲电场技术在果蔬汁加工及贮藏中的研究进展

高压脉冲电场(HPEF)技术是近年来国际上热门的非热加工技术之一,不仅具有好的杀菌、钝酶效果,耗能较低,而且可较大程度地保持原料原有的营养物质和感官特性。近年来,HPEF技术在液态食品加工领域中的研究取得了一定进展,特别是在果蔬汁领域中。文章介绍了HPEF技术的原理以及在果蔬汁加工及贮藏过程中的影响因素和应用途径,并对HPEF技术在果蔬汁行业的应用前景进行了分析和展望。     

高压脉冲电场处理对初榨橄榄油得率和品质的影响

为开发一种能提高初榨橄榄油(VOO)得率、对品质无不利影响且适用于工业化生产的新工艺,以甘肃陇南产区莱星、鄂植8号品种油橄榄鲜果为原料,采用高压脉冲电场(PEF)处理辅助传统工艺提取VOO,通过与传统提取工艺比较,研究PEF处理对VOO得率、理化性质、总多酚含量和脂肪酸组成及相对含量的影响。结果表明:与传统提取工艺相比,采用PEF处理VOO得率平均增幅为15.38%,果渣含油率平均降幅为22.28%,对VOO的色泽、酸值、过氧化值、总多酚含量和脂肪酸组成及相对含量等总体无显著性影响。研究认为,在VOO传统提取工艺的基础上,鲜果破碎之后增加PEF处理环节,可显著提高VOO得率,而且对VOO品质无不利影响,该技术在VOO工业化生产中有良好的应用潜力。     

交变磁场对猪肉和牛肉冻藏品质的影响

以猪肉和牛肉为研究对象,探究交变磁场对其冻藏2,4,6,8周后品质的影响.结果表明:在1 mT交变磁场的作用下猪肉和牛肉样品相对于对照组降温速率更快,冰点分别降低了0.9,0.5℃,相变时间分别缩短了66.67％,65.00％;干耗损失和汁液损失明显减少、水分含量更高,且交变磁场组冻藏4周后样品的持水力仍大于80.00...     

Using electric field to modify wet gluten as meat analogue material: A comparative study between pulsed and direct current electric fields

To assess the efficacy of electric field (EF) on vegetable protein juice-holding and texturisation as a low denaturation processing means, the impacts of pulsed (PEF) and low direct current (DCEF) electric field on the water- (WHC) and oil-holding capacity (OHC), microstructure, texture and physical structure of wheat gluten were investigated using wet gluten dough. The results showed that the PEF and DCEF affected the WHC and OHC significantly. The PEF seemed not to affect the textural properties so severely although significant differences appeared in hardness, chewiness, gumminess, and cohesiveness; there were no significant differences either in springiness or in resilience. The DCEF had a stronger impact on all the textural indices. Scanning electronic microscopy suggested that the PEF caused smaller and uniform micropores and the DCEF derivated more continuous and compact microstructure. Fourier transform infrared spectrometry demonstrated that EF significantly altered the composition proportion of the secondary structure. A slight blue shifts of UV spectra, a red shift of fluorescence spectra, and an increased surface hydrophobicity of gluten could be observed after EF treatment. X-ray diffractometry demonstrated that the EF significantly made the physical structure of wet gluten compacter. The results suggested that EF is promising in vegetable protein texturisation.     

高压脉冲电场加工牛初乳的研究

探索了利用高压脉冲电场处理牛初乳的可行性,对以高 压脉冲电场不同加工参数处理的牛初乳样品进行主要微 生物(细菌总数、大肠菌群、霉菌和酵母)的检测,并检测 其中功能性成分IgG含量,与未经处理的牛初乳中IgG 含量对比,证明了用高压脉冲电场加工技术处理牛初乳 的可行性,并确定了较适合的工艺条件。     

Novel technologies applied for recovery and value addition of high value compounds from plant byproducts: A review

Plant byproducts of food processing industry line are undervalued yet important resource. These byproducts contain large percentage of high value functional substances such as antioxidants, pectin, polyphenols and so on. Recently, many research studies concentrated on innovative technologies that promise to overcome such issues as time consuming, inefficiency, and low yield, among others, which exist in most conventional techniques. Consequently, to achieve the recovery of nutraceuticals from high added-value by-products, it is necessary to have more knowledge of these novel technologies and more importantly explore the possibility of application of these latest technologies to the recovery downstream processing. The present work will summarize state-of-the-art technological approaches concerning extraction, superfine and drying applied to plant food processing residues. Simultaneously, the application of the bioactive components originated from byproducts in food industry will also be reviewed.