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).     

Impact of high pressure and pulsed electric fields on bioactive compounds and antioxidant activity of orange juice in comparison with traditional thermal processing

Bioactive compounds (vitamin C, carotenoids, and flavanones) and DPPH* radical scavenging capacity (RSC) were measured in orange juice (OJ) subjected to different technologies. High pressure (HP) (400 MPa/40 degrees C/1 min), pulsed electric fields (PEF) (35 kVcm(-1)/750 micros), low pasteurization (LPT) (70 degrees C/30 s), high pasteurization (HPT) (90 degrees C/1 min), HPT plus freezing (HPT+F) (-38 degrees C/15 min), and freezing (F) were studied. Among the treatments assayed, even though the losses in total vitamin C were < 9%, treatments with the higher temperatures tended to show the higher decrease in the content of both forms of vitamin C. HP treatment led to an increased (P < 0.05) carotenoid release (53.88%) and vitamin A value (38.74%). PEF treatment did not modify individual or total carotenoids content. Traditional thermal treatments did not exert any effect on total carotenoid content or vitamin A value. With regard to individual carotenoid extraction, HPT and HPT+F led to different releases of carotenoids. With respect to flavanones, HP treatment led to increased (P < 0.05) naringenin (20.16%) and hesperetin (39.88%) contents, whereas PEF treatment did not modify flavanone content. In general, pasteurization and freezing process led to a diminished (P < 0.05) naringenin content (16.04%), with no modification in hesperetin. HP and PEF treatments did not modify DPPH* RSC. In the case of traditional thermal technologies, HPT treatment showed a decrease (P < 0.05) in RSC (6.56%), whereas LPT, HPT+F, and F treatments did not modify RSC. Vitamin C modulated RSC, in terms of antioxidant concentration (EC50) and kinetics (AE = 1/EC50TEC50), in the treated and untreated OJ. In summary, HP and PEF technologies were more effective than HPT treatment in preserving bioactive compounds and RSC of freshly squeezed orange juice.     

Commercial scale pulsed electric field processing of tomato juice

Effects of commercial scale pulsed electric field (PEF) processing on the quality of tomato juice were studied and compared with those of thermal processing. Tomato juice was prepared by hot break at 88 degrees C for 2 min or by cold break at 68 degrees C for 2 min and then thermally processed at 92 degrees C for 90 s or PEF processed at 40 kV/cm for 57 micros. Thermally processed, PEF processed, and unprocessed control juices were packed into 50 mL sterilized polypropylene tubes in a sanitary glovebox and stored at 4 degrees C for 112 days. Both thermally and PEF processed juices showed microbial shelf life at 4 degrees C for 112 days. The lipoxygenase activities of thermally and PEF processed juices were 0 and 47%, respectively. PEF processed juice retained more ascorbic acid than thermally processed juice at 4 degrees C for 42 days (p < 0.05). No significant differences were observed in the concentration of lycopene, degrees Brix, pH, or viscosity between thermally and PEF processed juices during the storage (p > 0.05). Sensory evaluations indicated that flavor and overall acceptability of PEF processed juice were preferred to those of thermally processed juice (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.     

Influence of temperature, modified atmosphere packaging, and heat treatment on aroma compounds in broccoli

The aroma compounds in broccoli stored in different modified atmospheres were studied. The packaging materials used were oriented polypropylene (OPP), poly(vinyl chloride) (PVC), and low-density polyethylene (LDPE) containing an ethylene-absorbing sachet. All samples were stored for either 1 week at a constant temperature of 10 degrees C or for 3 days at 4 degrees C, followed by 4 days at 10 degrees C. The atmospheres that developed inside the packaging materials differed significantly. The broccoli samples were analyzed raw and after cooking, with regard to volatile compounds, using gas-phase (headspace) extraction followed by gas chromatography-mass spectrometry (GC-MS) and GC-olfactometry. Dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), hexanal, 3-cis-hexen-1-ol, nonanal, ethanol, and a group of thiocyanates were selected for a detailed study because these compounds cause off-odor and can be used as indicators of stress. Significant differences were found in the aroma profiles of the broccoli samples relative to the packaging materials used for storage. Storage in OPP (14% O(2), 10.5% CO(2)) resulted in most of the off-odors, while storage in LDPE (6% O(2), 7% CO(2)) and PVC (17.9% O(2), 4% CO(2)) was found to maintain the concentration of DMS, DMDS, and DMTS during storage. Heat treatment of the broccoli increased the content of aroma compounds as well as the number of compounds containing sulfur.     

Kinetic study of anthocyanins, vitamin C, and antioxidant capacity in strawberry juices treated by high-intensity pulsed electric fields

A kinetic study of anthocyanins, vitamin C, and antioxidant capacity was carried out in strawberry juice treated with high-intensity pulsed electric fields. Samples were subjected to electric field strengths from 20 to 35 kV/cm for up to 2000 mus applying 1 mus bipolar pulses at 232 Hz. The suitability of simple first-order kinetics and an empirical model based on Weibull distribution function to describe changes in experimental data are discussed. In addition, different secondary models relating the antioxidant property retention to the electric field strength and treatment time are given. The Weibull kinetic model was the most accurate ( R (2) adj >or= 0.727) to predict anthocyanins, vitamin C, and antioxidant capacity changes in strawberry juice through the HIPEF treatment time. The combined effect of treatment time and electric field strength on health-related compounds of strawberry juice was successfully predicted (R(2) adj >or= 0.874) through secondary expressions. The proposed models are useful to predict the variation of the antioxidant potential of strawberry juice with the key parameters involved in HIPEF treatments.     

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.     

锦橙汁辐照和巴氏灭菌处理后相关品质的分析

为探讨辐照和巴氏杀菌对橙汁品质的影响,对锦橙汁分别进行1.4、2.8、5.6kGy3种不同剂量辐照及巴氏灭菌处理,使用固相微萃取-气质联用技术对挥发性成分进行分析,测定橙汁色度、pH值和Vc含量,并对橙汁香气进行感官评定。在鲜橙汁、巴氏灭菌汁和3种辐照样品中分别检测到了54、47、57、55和53种成分,2.8kGy剂量辐照处理后橙汁挥发性成分总峰面积最高,β-月桂烯、柠檬烯和γ-松油烯等橙汁特征香气物质经辐照后保持率高于巴氏灭菌。各种处理后Vc含量均有所下降,橙汁橙香均减弱。1.4kGy辐照后的橙汁感官评价结果最好,因此可以对橙汁进行低剂量辐照灭菌。     

Influence of thermal treatment on black currant (Ribes nigrum L.) juice aroma

The influence of thermal treatment on black currant juice aroma was investigated in temperature and time ranges relevant for black currant juice concentration processes, namely, 45, 60, 75, and 90 degrees C. Forty-nine aroma compounds were quantified, and the thermal treatment resulted in concentration increases of most terpenes, aldehydes, furans, and phenols, whereas the concentration of esters slightly decreased. Higher temperatures and longer exposure times had larger effects on the aroma compounds. Odor triangle tests showed no sensory difference between pasteurized juice and juice heated at 60 degrees C, whereas juice heated at 90 degrees C differed significantly from pasteurized juice. It is concluded that a 90 degrees C thermal treatment of black currant juice, which is in the temperature range used for conventional evaporation of black currant juice, has an effect on the aroma and sensory properties.     

Processing and storage effects on orange juice aroma: a review

Freshly squeezed orange juice aroma is due to a complex mixture of volatile compounds as it lacks a specific character impact compound. Fresh hand-extracted juice is unstable, and thermal processing is required to reduce enzyme and microbial activity. Heating protocols range from the lightly heated not from concentrate, NFC, to the twice heated, reconstituted from concentrate, RFC, juices. Thermal processing profoundly effects aroma composition. Aroma volatiles are further altered by subsequent time-temperature storage conditions. Heating reduces levels of reactive aroma impact compounds such as neral and geranial, and creates off-flavors or their precursors from Maillard, Strecker, and acid catalyzed hydration reactions. Off-flavors such as 4-vinylguaiacol, p-cymene, and carvone are the products of chemical reactions. Other off-flavors such as butane-2,3-dione, guaiacol, and 2,6-dichlorophenol are indicators of microbial contaminations. Since most orange juice consumed worldwide is processed, the goal of this review is to summarize the widely scattered reports on orange juice aroma differences in the three major juice products and subsequent aroma changes due to packaging, storage, and microbial contamination with special emphasis on results from GC-O studies.     

Effect of ultrahigh-temperature continuous ohmic heating treatment on fresh orange juice

The scope of this study is the effect of ohmic heating thermal treatment on liquid fruit juice made of oranges. Effects of ohmic heating on the quality of orange juice were examined and compared to those of heat pasteurization at 90 degrees C for 50 s. Orange juice was treated at temperatures of 90, 120, and 150 degrees C for 1.13, 0.85, and 0.68 s in an ohmic heating system. Microbial counts showed complete inactivation of bacteria, yeast, and mold during ohmic and conventional treatments. The ohmic heating treatment reduced pectin esterase activity by 98%. The reduction in vitamin C was 15%. Ohmic-heated orange juice maintained higher amounts of the five representative flavor compounds than did heat-pasteurized juice. Sensory evaluation tests showed no difference between fresh and ohmic-heated orange juice. Thus, high-temperature ohmic-heating treatment can be effectively used to pasteurize fresh orange juice with minimal sensory deterioration.     

Storage temperature effects on blood orange fruit quality.

Orange fruits of two blood varieties (Tarocco and Moro) were stored at 8 degrees C and 22 degrees C for 85 and 106 days, respectively, and analyzed periodically for standard quality parameters (total soluble solids, total acidity, ascorbic acid, juice yield, and rind color) and sensory influencing parameters (anthocyanins, and total and free hydroxycinnamic acids). A decrease in total acidity (TA) and juice yield during storage was observed for both cultivars; total soluble solids (TSS) increased only in the Tarocco oranges stored at 8 degrees C. The increase in TSS observed for Tarocco and the simultaneous decrease in TA in both varieties resulted in a higher maturity index (TSS/TA) for the two cultivars. No loss of vitamin C was noted in Tarocco orange at either temperature, whereas a sharp reduction in vitamin C occurred in the first 50 days of storage for Moro. A significant increase in anthocyanin content was observed in Tarocco and Moro stored at 8 degrees C. Overlong storage induces extensive hydrolysis of hydroxycinnamic derivatives to free acids in Moro orange and these, in turn, could develop the malodorous vinylphenols.     

高压脉冲杀菌集成冷冻浓缩加工果汁的工艺

为了最大限度的保留果汁原有的生鲜风味和营养,采用高压脉冲电场杀菌和冷冻浓缩这两种非热加工的集成技术,应用在果汁浓缩加工中,其中高压脉冲电场技术可以有效地抑制微生物生长,而冷冻浓缩可以有效地钝化酶活力。将该系统非热力加工工艺应用于浓缩橙汁,经感官评定分析,结果表明,产品品质明显优于巴氏杀菌橙汁。     

Characterization of the interaction between two food aroma components, alpha-pinene and ethyl butyrate, and ethylene-vinyl alcohol copolymer (EVOH) packaging films as a function of environmental humidity

The ethylene-vinyl alcohol copolymers (EVOHs) are well-known high oxygen barrier materials that are being used successfully in the design of packaging structures for oxygen-sensitive food or pharmaceutical products. Recently, there has been increasing interest in using EVOH materials to provide a high barrier to organic compounds as a means to reduce food aroma scalping. However, the barrier function of this family of materials diminishes significantly in humid environments, and it is supposed that so does the organic vapor barrier. In this work, a new sorption-based method to characterize the interaction between food aroma and polymer films for packaging as a function of relative humidity is presented and is used to determine the barrier to ethyl butyrate and alpha-pinene of EVOH at 23 degrees C. The results show that although EVOH is an excellent barrier to food aroma when dry, a property that even improves at low relative humidity (RH), the solubility and diffusivity of the compounds tested increase dramatically with humidity at medium to high water activities. However, even in the worst case (100% RH), EVOH outperforms low-density polyethylene (LDPE) as a barrier to organic vapors at least 500,000-fold.     

Use of 2-furoylmethyl derivatives of GABA and arginine as indicators of the initial steps of maillard reaction in orange juice

The formation of 2-furoylmethyl derivatives of GABA (2-FM-GABA) and arginine (2-FM-Arg) as early indicators of nonenzymatic browning in different types of orange juice was studied. In dehydrated orange juice, the presence of 2-FM-GABA and 2-FM-Arg was detected from the first day of storage at 30 degrees C. In this type of juice, the content of these two compounds increased with temperature (30, 50 degrees C) and time (1-7 days) of storage. A noticeable increase in 5-hydroxymethylfurfural was only observed after 4 days of storage at 50 degrees C. No formation of 2-FM-GABA and 2-FM-Arg was detected in liquid orange juice heated under conditions similar to those used in the industry. These furoylmethyl derivatives were also found in commercial orange juice made from concentrates. A slight increase in their concentration was observed in the two samples stored during 8 months at room temperature. According to the results obtained, 2-FM-GABA and 2-FM-Arg contents could be suitable indicators to assess the main modifications due to Maillard reaction produced during the manufacture and/or storage of orange juice concentrates.     

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%.     

GC-olfactometric characterization of aroma volatiles from the thermal degradation of thiamin in model orange juice

Model orange juice solutions containing 0.024 mM thiamin hydrochloride were stored for up to 8 weeks at 35 degrees C in amber glass containers. Volatiles were evaluated, primarily, using gas chromatography (GC) with olfactometry but also with flame ionization detector, pulsed-flame photometer detector (PFPD) (sulfur specific), and MS detection. Both 2-methyl-3-furanthiol (MFT) and its dimer, bis(2-methyl-3-furyl) disulfide (MFT-MFT) were identified thus confirming that thiamin could serve as the precursor to these potent off-flavors in thermally degraded citrus juices. Thirteen aroma active components were observed. MFT and MFT-MFT were observed after only a few days storage, and produced 33% of the total aroma activity after 7 d storage. Both compounds were observed olfactometrically earlier than they could be detected using PFPD. Other aroma-active compounds included 4,5-dimethylthiazole (skunky, earthy), 3-thiophenethiol (meaty, cooked), 2-methyl-4,5-dihydro-3(2H)-thiophenone (sour-fruity, musty, green), 2-acethylthiophene (burnt), 2-formyl-5-methylthiophene (meaty), and 2-methyl-3-(methyldithio) furan (meaty).     

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.