Effects of pulsed electric fields on the quality of orange juice and comparison with heat pasteurization

Effects of pulsed electric fields (PEF) at 35 kV/cm for 59 micros on the quality of orange juice were investigated and compared with those of heat pasteurization at 94.6 degrees C for 30 s. The PEF treatment prevented the growth of microorganisms at 4, 22, and 37 degrees C for 112 days and inactivated 88% of pectin methyl esterase (PME) activity. The PEF-treated orange juice retained greater amounts of vitamin C and the five representative flavor compounds than the heat-pasteurized orange juice during storage at 4 degrees C (p < 0.05). The PEF-treated orange juice had lower browning index, higher whiteness (L), and higher hue angle (theta) values than the heat-pasteurized orange juice during storage at 4 degrees C (p < 0. 05). The PEF-treated orange juice had a smaller particle size than the heat-pasteurized orange juice (p < 0.05). degrees Brix and pH values were not significantly affected by processing methods (p > 0. 05).     

Carotenoid profile modification during refrigerated storage in untreated and pasteurized orange juice and orange juice treated with high-intensity pulsed electric fields

A comparative study was made of the evolution and modification of various carotenoids and vitamin A in untreated orange juice, pasteurized orange juice (90 degrees C, 20 s), and orange juice processed with high-intensity pulsed electric fields (HIPEF) (30 kV/cm, 100 micros), during 7 weeks of storage at 2 and 10 degrees C. The concentration of total carotenoids in the untreated juice decreased by 12.6% when the juice was pasteurized, whereas the decrease was only 6.7% when the juice was treated with HIPEF. Vitamin A was greatest in the untreated orange juice, followed by orange juice treated with HIPEF (decrease of 7.52%) and, last, pasteurized orange juice (decrease of 15.62%). The decrease in the concentrations of total carotenoids and vitamin A during storage in refrigeration was greater in the untreated orange juice and the pasteurized juice than in the juice treated with HIPEF. During storage at 10 degrees C, auroxanthin formed in the untreated juice and in the juice treated with HIPEF. This carotenoid is a degradation product of violaxanthin. The concentration of antheraxanthin decreased during storage, and it was converted into mutatoxanthin, except in the untreated and pasteurized orange juices stored at 2 degrees C.     

Effect of processing techniques at industrial scale on orange juice antioxidant and beneficial health compounds

Phenolic compounds, vitamin C (L-ascorbic acid and L-dehydroascorbic acid), and antioxidant capacity were evaluated in orange juices manufactured by different techniques. Five processes at industrial scale (squeezing, mild pasteurization, standard pasteurization, concentration, and freezing) used in commercial orange juice manufacturing were studied. In addition, domestic squeezing (a hand processing technique) was compared with commercial squeezing (an industrial FMC single-strength extraction) to evaluate their influences on health components of orange juice. Whole orange juice was divided into soluble and cloud fractions after centrifugation. Total and individual phenolics were analyzed in both fractions by HPLC. Commercial squeezing extracted 22% more phenolics than hand squeezing. The freezing process caused a dramatic decrease in phenolics, whereas the concentration process caused a mild precipitation of these compounds to the juice cloud. In pulp, pasteurization led to degradation of several phenolic compounds, that is, caffeic acid derivatives, vicenin 2 (apigenin 6,8-di-C-glucoside), and narirutin (5,7,4'-trihydroxyflavanone-7-rutinoside) with losses of 34.5, 30.7, and 28%, respectively. Regarding vitamin C, orange juice produced by commercial squeezing contained 25% more of this compound than domestic squeezing. Mild and standard pasteurization slightly increased the total vitamin C content as the contribution from the orange solids parts, whereas concentration and freezing did not show significant changes. The content of L-ascorbic acid provided 77-96% of the total antioxidant capacity of orange juice. Mild pasteurization, standard pasteurization, concentration, and freezing did not affect the total antioxidant capacity of juice, but they did, however, in pulp, where it was reduced by 47%.     

超高压处理对鲜榨橙汁中主要香气成分的影响

为了了解超高压处理对鲜橙汁香气的影响,分析超高压处理后橙汁香气变化的原因。采用固相微萃取（Solid Phase Microextraction,SPME）方法对不同压力（100～500 MPa）超高压处理的鲜榨橙汁中的香气成分进行富集,并经气相色谱-质谱联用仪（Gas Chromatography-Mass Spectrometry,GC-MS）检测分析,橙汁中的主要香气成分有：3种烯（柠檬烯、月桂烯、α-蒎烯）;2种醇（芳樟醇、α-松油醇）;3种醛（柠檬醛、辛醛、癸醛）;1种酮（香芹酮）;2种酯（丁酸乙酯、3-OH-己酸乙酯）,它们是构成橙汁的主要特征致香成分。通过定量检测分析发现：超高压处理对橙汁中的柠檬烯成分影响很显著,经500 MPa的压力处理15 min后其含量下降了75%,而月桂烯和α-蒎烯受高压影响较小;α-松油醇、香芹酮含量经高压处理后迅速增加;醛类特征香气成分基本不受高压影响;酯类成分在高压下会发生变化,但总体变化不显著。超高压处理橙汁使其中柠檬烯在高压下发生水合、氧化反应分别生成α-松油醇和香芹酮。超高压处理橙汁一般压力要大于300 MPa,而该文研究发现500 MPa处理会造成较多的香气损失,故橙汁超高压处理时的压力最好选择 400 MPa左右。     

Effects of pulsed electric fields on the bioactive compound content and antioxidant capacity of tomato fruit

The effect of moderate intensity pulsed electric fields (MIPEF) on the bioactive compounds (total polyphenol, lycopene, and vitamin C content) as well as on the antioxidant capacity of tomato fruit was studied. The MIPEF treatment conditions were optimized to obtain tomato fruit with a high content of bioactive compounds. Tomato fruits were subjected to different electric field strengths (from 0.4 to 2.0 kV/cm) and number of pulses (from 5 to 30) and then immediately refrigerated at 4 °C for 24 h. A concentration of bioactive compounds higher than that of untreated tomatoes was obtained in MIPEF-treated tomatoes. A 44% increase in total polyphenol content was achieved under 30 pulses at 1.2 kV/cm. The hydrophilic antioxidant capacity was also enhanced by 44% applying 18 pulses at 1.2 kV/cm, and the lipophilic antioxidant capacity was increased by 37% under 5 pulses at 1.2 kV/cm. The maximum overall level of bioactive compounds and antioxidant capacity in the treated tomatoes was obtained under 16 pulses at 1 kV/cm. Therefore, MIPEF treatments could be considered an effective method to enhance the bioactive compound content and antioxidant potential of tomatoes.     

Effect of high-intensity pulsed electric fields processing and conventional heat treatment on orange-carrot juice carotenoids

Liquid chromatography (LC) was the method of choice for quantification of carotenoids (including geometrical isomers) to evaluate the effects of high-intensity pulsed electric field (HIPEF), a nonthermal preservation method, with different parameters (electric field intensities and treatment times), on an orange-carrot juice mixture (80:20, v/v). In parallel, a conventional heat treatment (98 degrees C, 21 s) was applied to the juice. HIPEF processing generally caused a significant increase in the concentrations of the carotenoids identified as treatment time increased. HIPEF treatment at 25 and 30 kV/cm provided a vitamin A concentration higher than that found in the pasteurized juice.     

Comparative study of pulsed electric field and thermal processing of apple juice with particular consideration of juice quality and enzyme deactivation

As an alternative to thermal pasteurization, pulsed electric fields (PEF) were applied to apple juices on laboratory and pilot plant scale, investigating the effects on juice quality. PEF application still falls under the EU Novel Food Regulation. Consequently, extensive investigation of quality parameters is a prerequisite to prove substantial equivalence of juices resulting from the novel process and conventional production, respectively. Juice composition was not affected by PEF treatment. However, browning of the juices provided evidence of residual enzyme activities. On laboratory scale, complete deactivation of peroxidase (POD) and polyphenoloxidase (PPO) was achieved when PEF treatment and preheating of the juices to 60 degrees C were combined. Under these conditions, a synergistic effect of heat and PEF was observed. On pilot plant scale, maximum PPO deactivation of 48% was achieved when the juices were preheated to 40 degrees C and PEF-treated at 30 kV/cm (100 kJ/kg). Thus, minimally processed juices resulted from PEF processing, when applied without additional conventional thermal preservation. Since this product type was characterized by residual native enzyme activities and nondetectable levels of 5-hydroxymethylfurfural, also when preheating up to 40 degrees C was included, it ranged between fresh and pasteurized juices regarding consumers' expectation of freshness and shelf life. Consistent with comparable iron contents among all juice samples, no electrode corrosion was observed under the PEF conditions applied.     

超滤对血橙果汁中抗氧化成分及总抗氧化能力的影响

采用管式聚偏氟乙烯(PVDF)超滤膜，探讨了超滤对血橙果汁中抗氧化成分及总抗氧化能力的影响。结果表明，其对维生素C和花青素类成分的保存率约为85%左右，对几种酚酸和类黄酮组分（除槲皮素外）的保存率均在90%以上。同未杀菌的血橙原汁相比，巴氏杀菌汁的总抗氧化能力(TAA)损失率为23%，而超滤澄清汁仅为10%左右，主要与维生素C和花青素含量损失有关。     

Lycopene, vitamin C, and antioxidant capacity of tomato juice as affected by high-intensity pulsed electric fields critical parameters

The effects of high-intensity pulsed electric field (HIPEF) treatment variables (frequency, pulse width, and pulse polarity) on the lycopene, vitamin C, and antioxidant capacities of tomato juice were evaluated using a response surface methodology. An optimization of the HIPEF treatment conditions was carried out to obtain tomato juice with the highest content of bioactive compounds possible. Samples were subjected to an electric field intensity set at 35 kV/cm for 1000 micros using squared wave pulses, frequencies from 50 to 250 Hz, and a pulse width from 1 to 7 micros, in monopolar or bipolar mode. Data significantly fit (P < 0.001) the proposed second-order response functions. Pulse frequency, width, and polarity significantly affected the lycopene, vitamin C, and antioxidant capacities of HIPEF-treated tomato juice. Maximal relative lycopene content (131.8%), vitamin C content (90.2%), and antioxidant capacity retention (89.4%) were attained with HIPEF treatments of a 1 micros pulse duration applied at 250 Hz in bipolar mode. Therefore, the application of HIPEF may be appropriate to achieve nutritious tomato juice.     

高压脉冲电场对鲜榨梨汁的杀菌效果及其对产品品质的影响

为了采用非热杀菌技术以生产高质量的果汁,研究了高压脉冲电场（PEF）对梨汁的杀菌效果及其对产品品质的影响。结果表明,当电场频率、电场强度和处理时间、温度分别为200 Hz、30 kV/cm和240 μs、10℃时,梨汁中接种的大肠杆菌、酿酒酵母的数量分别下降4.6、2.7个数量级。温度具有辅助杀菌效应,相同频率和场强下处理时间200 μs,当样品温度从10℃上升致40℃时,大肠杆菌致死率提高了1.4个数量级,酿酒酵母致死率提高了2.0个数量级,未接种鲜榨梨汁的细菌致死率提高了2.0个数量级,霉菌酵母致死率提高了1.0个数量级。PEF处理后梨汁理化性质、营养成分比热处理更接近原样。气相色谱－质谱（GC-MS）对梨汁风味物质进行检测的结果表明,梨汁中含量最多的挥发性风味物质为酯类,与传统热处理相比,PEF处理对梨汁风味物质的影响较小。因此脉冲电场不仅有较好的杀菌作用,并且最大限度地保证了梨汁的品质。     

Effects of pulsed electric fields on the activity and structure of pepsin

A continuous pulsed electric field (PEF) system integrated with six co-field flow PEF treatment chambers was used to study the inactivation of pepsin. The inactivation of pepsin activity was a function of applied electric field strength, electrical conductivity, and pH. The inactivation of pepsin by PEF followed a first-order model. The first-order inactivation kinetic constant of pepsin was 0.012 (1/mus) in 7.5 mM HCl (pH 2.0) at 34.2 kV/cm. Aggregation of pepsin was observed during PEF treatment; however, the inactivation took place before the formation of aggregates. Circular dichroism analysis showed that inactivation of pepsin by PEF was correlated to the loss of beta-sheet structure in a pepsin molecule. The relative residual activity of PEF-treated pepsin was correlated to the relative molar ellipticity at 215 nm. Both PEF- and heat-induced inactivation of pepsin were correlated with the alteration of the secondary structure (beta-sheet dominant structure) of pepsin.     

超高压处理对杏汁香气成分的影响

为了探讨超高压处理对杏汁香气成分的影响,将杏原汁在500 MPa压力、25℃温度条件下处理20 min后,经顶空固相微萃取与毛细管气相色谱-质谱联用技术检测超高压处理前后杏汁香气成分的变化,并用面积归-化法测定了各种成分的质量分数.结果表明超高压处理后对杏汁中香气成分的有较明显影响,其中己醛、2-己烯醛、糠醛、己醇、叶醇、芳樟醇、橙花醇、β-苯乙醇等香味成分的质量分数分别增长了68.14%、95.26%、46.76%、61.11%、58.56%、35.75%、37.75%和42.30%;酯类、内酯类的香气成分的含量有所降低;酮类香味成分的含量则没有明显变化.感官评定表明:超高压处理不仅能很好地保持了杏的特征香气,而且使杏汁的青鲜香气更加突出,有利于产品风味品质的提高,这与杏汁中香气成分检测结果相一致,因此对杏加工来说超高压处理是一种很有前景的冷加工技术.     

Bioavailability and antioxidant effects of orange juice components in humans

Seven healthy females and six males consumed daily 256 mg of vitamin C, 271 mg of flavanones (mainly as glycosides), 6 mg of carotenoids (mainly xanthophylls and cryptoxanthins), and 0.16 mg of folate by incorporation of daily three times 236 mL of not from concentrate orange juice (OJ) into their habitual diet. At the end of 3 weeks, mean vitamin C, folate, carotenoid, and flavanone plasma concentrations increased significantly relative to baseline by 59% (p < 0.001), 46% (p = 0.018), and 22% (p < 0.001), and 8-fold (p = 0.045), respectively. Flavanones were excreted in urine 9-fold more at the end of the intervention (p = 0.01) but returned to baseline 2 days after study completion. After the 3 week intervention, plasma concentrations of vitamins A and E did not change. 8-Hydroxydeoxyguanosine in white blood cells declined by 16% (p = 0.38; n = 11), and in individuals with high baseline concentrations by 29% (p = 0.36; n = 7), respectively. Low-density lipoprotein (LDL)-/high-density lipoprotein (HDL)-cholesterol ratios decreased but cholesterol (HDL, LDL, total) and thiobarbituric acid reactive substance plasma concentrations did not change significantly. We conclude from this pilot study that OJ is an excellent food source to enhance circulating concentrations of valuable hydrophilic as well as lipophilic phytochemicals.     

高压二氧化碳处理对橙汁货架期的影响(简报)

为了探讨高压CO2加工技术对橙汁货架期的影响,将新鲜的橙汁在温度为37℃,压力60 MPa的高压CO2中处理9 min后,分别在4、15、25和37℃下贮藏,测定果胶甲基酯酶残存相对活性、浑浊度、维生素C残留量和颜色变化。结果表明：在4和15℃下贮藏,橙汁的货架期分别在84和56 d以上;浑浊稳定性比较好;维生素C含量保持在80%以上;在4、15和25℃下贮藏颜色基本上没变化。因此,高压CO2处理橙汁可有效延长产品的货架期,此技术值得在果汁企业中广泛推广。     

高压脉冲电场对鱼骨液物理状态变化的影响

为了研究高压脉冲电场(high intensity pulsed electric fields,PEF)作用对物质物理状态变化的影响,该试验以鱼骨液为研究对象,采用质构仪分析测试的方法,研究PEF作用下鱼骨液的流变学性质。通过主成分分析法确定PEF下鱼骨液物理状态变化的综合指标公式,通过单因素试验和Box-Behnken中心设计法得出PEF作用鱼骨液最佳参数:液料比9.81 m L/g、场强23.10 k V/cm、脉冲数10,综合指标达到2.3312,此时鱼骨液的物理指标分别为第一压缩功1.2 N,第二压缩功1.3 N,内聚性1.21,弹性9.25 mm,胶着性0.11 N,说明经过PEF处理,鱼骨液在第一循环和第二循环内获得指定形变所需要得能量增加,样品弹性增加,组成样品结构的内部键力降低,综合各物理状态指标的变化,说明PEF处理后的鱼骨液物理状态得到了明显改善(P=0.001210.01),因此高压脉冲电场技术可以应用于鱼骨液的加工处理。     

Effects of thermal treatments and storage on pectin methylesterase and peroxidase activity in freshly squeezed orange juice

A specific indicator of freshness, allowing routine distinction between freshly squeezed orange juices (FSOJs) and FSOJ-like products, was to be identified. Using the Actijoule unit of a tubular heater at a flow rate of 60 L/h, FSOJs from Citrus sinensis (L.) Osbeck cv. Valencia Late were continuously heated on a pilot plant scale at six different temperatures (42-92 degrees C), followed by continuous cooling to ambient temperature and subsequent filling into sterilized glass jars. The cloud stability and residual activities of pectin methylesterase (PE) and peroxidase (POD) were monitored over the storage at 4 degrees C for up to 62 days, thus considering the storage conditions of FSOJs in retail markets. As shown by the viable microbial counts throughout storage, microbial activity was insignificant due to good sanitary practice, thus proving that the enzyme activities detected were of plant origin. The juices processed at temperatures > or =62 degrees C were characterized by minor residual activities. When exposed to temperatures <62 degrees C in the genuine acidic matrix of the juices, the heat stability of PE exceeded that of POD. Compared with the aforementioned samples, the juice processed at 52 degrees C with a residual PE activity of 33.8% was hardly inferior in terms of cloud stability within the first 14 days. After the juice was processed at 42 degrees C, rapid clarification occurred within the first 8 days, consistent with undetectable PE deactivation. Hence, only the range of approximately 50-60 degrees C is relevant in minimal heat-processing for the retention of cloud stability within the short turnover period of FSOJ-like products, with partial PE and POD deactivation being already sufficient to distinguish those juices from FSOJs. Irrespective of the previous thermal treatment, the total PE activity remained nearly constant during storage, whereas the POD activity rapidly declined to minor levels after 20 days. Consequently, as to the future analysis of samples with unknown processing history, PE was suggested as an indicator enzyme for the freshness of FSOJs, allowing their unambiguous distinction from minimally heat-processed juices.     

Flavor, color, and vitamin C retention of pulsed electric field processed orange juice in different packaging materials

Effects of packaging materials, storage temperature, and time on the stability of pulsed electric field (PEF) processed orange juice were investigated. Single-strength orange juice was treated with PEF at an electric field strength of 35 kV/cm for 59 micros using an integrated pilot plant scale PEF processing and glovebox packaging system. The retention of eight orange juice aroma compounds, color, and vitamin C in glass, polyethylene terephthalate (PET), high-density polyethylene, and low-density polyethylene were evaluated at 4 and 22 degrees C for 112 days. Packaging material had a significant effect (p < or = 0.05) on the retention of orange juice aroma compounds, color, and vitamin C. PEF-treated orange juice had a shelf life of >16 weeks in glass and PET at 4 degrees C.     

超高压对鲜榨果蔬汁的杀菌效果

为防止鲜榨果蔬汁受微生物污染而腐败变质,通过超高压加工处理降低其污染的风险,延长产品货架期,提高产品的安全性。该文通过研究超高压处理鲜榨苹果汁和胡萝卜汁及其在贮藏期的菌落总数变化,确定超高压杀菌后的鲜榨苹果汁和胡萝卜汁的生物安全性。试验结果表明：超高压对低pH值的鲜榨苹果汁的杀菌效果优于pH值偏中性的鲜榨胡萝卜汁。随着处理压力的增大和处理时间的延长,鲜榨苹果汁和胡萝卜汁中的菌落总数显著降低（P＜0.05）。经过400 MPa、15 min处理的鲜榨苹果汁可在4℃下贮藏7 d仍保持食用安全性,而鲜榨胡萝卜汁经400 MPa、45 min处理,仅能在4℃下贮藏3d。     

橙汁加工过程对农药炔螨特残留的影响

为弄清橙汁加工过程中农药炔螨特残留的动态,通过田间喷施浓度为5倍于最高推荐剂量的农药溶液以强化炔螨特在甜橙上的残留,然后按照橙汁商业化加工过程进行加工,采用QuEChERS前处理技术结合气相色谱-串联质谱法检测炔螨特的含量,来考察橙汁商业化加工过程对炔螨特残留的影响。结果表明:炔螨特残留主要分布于甜橙果皮中,果肉中炔螨特的残留量不足全果的5%。清洗能除去全果中32.5%的炔螨特残留。初榨果汁、精滤果汁、非浓缩橙汁(NFC橙汁)和浓缩橙汁中的残留量分别为原料果的1.98%、1.95%、1.73%、1.37%,其中NFC橙汁和浓缩橙汁的加工因子分别为0.0173和0.0137,但炔螨特在果渣和精油中发生富集,加工因子分别为1.2822和18.4947。研究结果为橙汁加工工艺的优化和炔螨特残留的膳食暴露评估提供参考。     

超高压处理对砀山梨汁中过氧化物酶活性的影响

该文研究了超高压处理对砀山梨汁中过氧化物酶活性的影响。试验压力为0.1～500 MPa，温度为20～60℃。此外，考察了不同pH值(3～7)和保压时间(2～34 min)超高压处理对酶活性的影响。试验结果表明：在处理温度为50℃、保压时间为10 min和梨汁pH 5的条件下，300 MPa以下压力范围内高压处理酶被激活，其活性增加；大于300 MPa时酶的活性随压力增大而下降。高压处理时，温度低于40℃对酶的活性影响不大；有效影响高压处理的最小温度为40℃。保压时间超过10 min后时间延长对酶的活性影响