Changes of health-related compounds throughout cold storage of tomato juice stabilized by thermal or high intensity pulsed electric field treatments

The effect of high intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1500 μs in bipolar 4-μs pulses at 100 Hz, with an energy density of 8269 kJ/L) on the main bioactive compounds and antioxidant capacity of tomato juice was investigated and compared to heat pasteurization (90 °C for 1 min or 30 s) having the fresh juice as a reference. HIPEF and heat treated tomato juices showed higher lycopene and lower vitamin C levels than the untreated juice. However, no significant changes in the total phenolic content and antioxidant capacity were observed between treated and fresh juices just after processing. Lycopene, vitamin C and antioxidant capacity of both treated and untreated juices decreased exponentially during storage following a first order kinetics (R² = 0.763–0.987), whereas tomato juices maintained their initial phenolic content. HIPEF-treated tomato juice maintained higher lycopene and vitamin C content than the thermally treated juices during the storage time. Hence, the application of HIPEF may be appropriate to achieve nutritious and fresh like tomato juice.

Industrial relevance

HIPEF processing can lead to tomato juice with higher nutritional value than that thermally processed. HIPEF-treated (35 kV/cm for 1500 μs with 4-μs bipolar pulses at 100 Hz, energy input of 8269 kJ/L) tomato juice shows greater lycopene, vitamin C and antioxidant capacity just after the treatment and during the storage time than heat treated (90 °C­30 s and 90 °C­60 s) tomato juice. Therefore, HIPEF technology is a feasible alternative to thermal treatment to obtain tomato juice with a high presence of health-related compounds.     

Influence of high-intensity pulsed electric field processing parameters on antioxidant compounds of broccoli juice

The effect of high-intensity pulsed electric field (HIPEF) processing parameters (electric field strength, treatment time, and polarity) on broccoli juice carotenoids, vitamin C, total phenolic (TP) content and antioxidant capacity (AC) was evaluated. Results obtained from HIPEF-processed broccoli juice were compared with those of thermally treated (90 °C/60 s) and untreated juices. HIPEF processing parameters influenced the relative content (RC) of bioactive compounds, and the relative AC (RAC). Maximum RC of lutein (121.2%), β-carotene (130.5%), TP (96.1%), vitamin C (90.1%) and RAC (5.9%) was reached between 25 and 35 kV/cm and from 2000 μs to 500 μs. The highest RAC and RC of bioactive compounds were observed in HIPEF treatments applied in bipolar mode, except for vitamin C. HIPEF-treated broccoli juice exhibited greater RC of bioactive compounds and RAC than juice treated by heat. HIPEF technology could be considered a promising option for preserving the antioxidant quality of broccoli juice.Industrial relevanceVegetable juices are becoming more and more popular because of their wide range of health-related compounds. Particularly, broccoli juice is attracting the food industry attention because it contains high amounts of vitamins, carotenoids and phenolic compounds, among other bioactive compounds. Broccoli juice requires treatment conditions that protect its microbial, nutritional and sensorial quality. HIPEF is a non-thermal technology for liquid food preservation that inactivates microorganisms and enzymes without compromising the nutritional and sensorial features of foods. Consequently, this technology could be used in the food industry as an alternative for thermal treatment to preserve the bioactive compounds present in vegetable juices, offering to consumers a healthy product.     

Changes on phenolic and carotenoid composition of high intensity pulsed electric field and thermally treated fruit juice–soymilk beverages during refrigerated storage

The effects of high intensity pulsed electric fields (HIPEF) (35 kV/cm with 4 μs bipolar pulses at 200 Hz for 800 or 1400 μs) or thermal (90 °C, 60 s) treatments over phenolic and carotenoid compounds of a fruit juice–soymilk (FJ–SM) beverage stored at 4 °C were evaluated and compared, having the untreated beverage as a reference. Coumaric acid, narirutin and hesperidin were the most abundant phenolic compounds in the FJ–SM beverage, while the main carotenoids were lutein, zeaxanthin and β-carotene. Immediately after HIPEF or heat processing, hesperidin content of the beverage showed a huge rise, resulting in a significant increase on the total phenolic concentration. Regarding carotenoid concentration, HIPEF or thermal treatment lead to a significant decrease; lutein, zeaxanthin and β-cryptoxanthin being the most affected compounds. In contrast, the content of some individual phenolics and carotenoids increased with time, while others tended to decrease or remained with no significant changes with regards to their initial values. Total phenolic concentration seemed to be highly stable during storage; while, total carotenoid content gradually diminished, irrespectively of the treatment applied. Overall, the changes observed in HIPEF treated FJ–SM beverage were less than those in the heat processed one. Hence, HIPEF is a feasible technology to obtain FJ–SM beverages with extended shelf-life and a similar profile of antioxidant compounds to freshly made beverages.     

Impact of Thermal and Pressure-Based Technologies on Carotenoid Retention and Quality Attributes in Tomato Juice

The aim of this study was to investigate the impact of thermal processing (TP) (90 °C, 90 s), high-pressure processing (HPP) (600 MPa, 46 °C, 5 min), and high-pressure homogenization (HPH) (246 MPa, 99 °C, <1 s) on product quality parameters, specifically carotenoid content, and physicochemical attributes of particle size, color, viscosity, total soluble solids, and pH in tomato juice. Unprocessed tomato juice was used as control. The four major species of carotenoids (lycopene, β-carotene, phytoene, and phytofluene) in tomato juice were analyzed by HPLC. The content of total lycopene, all-trans-lycopene, cis-lycopene isomers,  phytoene, and phytofluene, in TP-, HPP-, and HPH-treated tomato juice did not significantly differ from that in unprocessed (control) juice. Significant reduction in β-carotene content was observed after TP treatment but not after HPP and HPH treatments. HPH significantly reduced tomato juice particle volume mean diameter from ～330 μm in control, HPP-, and TP-treated tomato juices to ～17 μm. A concomitant increase in apparent viscosity was observed in HPH-treated juice versus control. HPH-treated juice had increased redness (a*) and yellowness (b*) than that in control and HPP-treated tomato juices. These results indicate that high-pressure-based technologies (HPP and HPH) can preserve carotenoids as well as improve physicochemical properties.     

Flavour retention and related enzyme activities during storage of strawberry juices processed by high-intensity pulsed electric fields or heat

The effects of high-intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1700 μs using pulses of 4 μs at 100 Hz in bipolar mode) and thermal treatments (90 °C for 30 s or 60 s) on lipoxygenase (LOX) and β-glucosidase (β-GLUC) activities as well as on the production of volatile compounds were assessed in strawberry juice for 56 days of storage. HIPEF-treated juice kept higher residual LOX activity than heat-treated juices during the first 28 days of storage. Moreover, β-GLUC increased its initial activity just after HIPEF processing. The concentration of DMHF in HIPEF-processed strawberry juice was above those of untreated and heat-treated juices during the first 14 days of storage. On the other hand, concentrations of ethyl butanoate and 1-butanol obtained after HIPEF processing were better maintained than after thermal processing. However, thermally-treated samples showed an increase in the amount of 1-butanol beyond day 35, causing an unpleasant flavour to the product. Thus, flavour stability in HIPEF-processed strawberry juice was greater than in thermally-treated samples during storage.     

Changes on flavor compounds throughout cold storage of watermelon juice processed by high-intensity pulsed electric fields or heat

The application of HIPEF processing (35 kV/cm for 1727 μs using bipolar pulses of 4-μs at 188 Hz) on watermelon juice was evaluated as an alternative to conventional heat treatments (90 °C for 30 s or 90 s) in order to achieve better preservation of watermelon aroma compounds for 56 days of storage at 4 °C. HIPEF processing not only induced a rise (roughly 20%) in the concentrations of hexanal, (E)-2-nonenal, nonanal, 6-methyl-5-hepten-2-one and geranylacetone but also achieved less reductions on the retention of volatiles than the thermal treatment at 90 °C for 60 s. In contrast, the content of (Z)-6-nonenal, 1-nonanol and (Z)-3-nonen-1-ol in the untreated and processed juices remained unchanged after processing. Despite the decrease in overall flavor compounds observed during storage irrespective of the treatment applied, HIPEF-treated juices showed better flavor retention than heat-treated samples for at least 21 days of storage. Moreover, changes in aldehydes and ketones during storage of treated watermelon juices were well fitted by a model based on the Weibull distribution function. Therefore, the application of HIPEF may be appropriate to preserve the initial volatile profile of watermelon juices during storage.     

Evaluation of microbial inactivation and physicochemical properties of pressurized tomato juice during refrigerated storage

Effects of high pressure processing (300-500 MPa/25 °C/10 min) on microbial inactivation and processing qualities of tomato juices during refrigerated storage at 4 °C for 28 days were investigated to compare with those of conventionally thermal processing. Conventionally, thermal processing almost inactivated all the microorganisms and pectolytic enzymes and produced microbially and consistency stable tomato juices; however, they also reduced the color, extractable carotenoids and lycopene and vitamin C compared with fresh juice. During storage, all the pressure processing could improve the extractable carotenoids and lycopene contents compared with fresh juice, and they also retained more vitamin C contents than thermal processing. Although 300- and 400-MPa processing could retain a/b values of tomato juices as fresh juice during storage for 21 and 28 days, 500-MPa processing could improve the color of juices even after storage. Syneresis occurred in the 300- and 400-MPa processing juices by storing for 7 and 14 days; however, viscosity stable juice was produced by 500-MPa processing. Moreover, 400- and 500-MPa processing significantly inactivated microorganisms and the juices were microbially stable during storage. This study demonstrated that 500-MPa processing would be an alternative for conventionally thermal processing for tomato juice with improvement of some processing quality attributes.     

Impact of high-intensity pulsed electric fields variables on vitamin C, anthocyanins and antioxidant capacity of strawberry juice

A response surface methodology was used to determine the combined effect of HIPEF critical processing conditions on vitamin C, anthocyanins and antioxidant capacity of strawberry juice. Keeping constant the electric field strength at 35 kV/cm and the treatment time at 1000 μs, the treatments were set at frequencies from 50 to 250 Hz, pulse width from 1 to 7 μs using monopolar or bipolar mode. A second order response function covering the whole range of experimental conditions was obtained for each health-related compound. Strawberry juice antioxidant potential was affected linearly by frequency, pulse width and pulse polarity. The quadratic term of frequency and the combined effect of frequency and pulse width were also significant. HIPEF treatments conducted at 232 Hz with bipolar pulses of 1 μs led to strawberry juices with the greatest presence of health-related compounds. The evaluation of the HIPEF critical parameters influence on health-related compounds can contribute to achieve optimal processing conditions to obtain strawberry juices with high antioxidant potential.     

Changes in quality attributes throughout storage of strawberry juice processed by high-intensity pulsed electric fields or heat treatments

The effects of high-intensity pulsed electric field (HIPEF) processing (35 kV/cm for 1700 μs applying 4-μs pulses at 100 Hz in bipolar mode) on color, viscosity and PME and PG activities in strawberry juice were studied and compared to those of heat treatments (90 °C for 60 s or 30 s) through 63 days of storage. L^∗ and viscosity values of the HIPEF-processed juices were higher than those found in the thermally treated. In addition, HIPEF-treated juice exhibited lower 5-(hydroxymethyl)-2-furfural (HMF) concentration and browning index than heat-treated juices throughout storage. On the other hand, HIPEF-treated juice maintained low residual pectin methylesterase (PME) activity (13.1%) for 63 days, whereas in the case of the thermally treated, 22.2 and 48.8% was retained after 60 s and 30 s, respectively. Strawberry juice treated by HIPEF achieved lower residual polygalacturonase (PG) activity (73.3%) than those of heat-processed at 90 °C for 60 s (76.2%) or 30 s (96.8%). Thus, HIPEF could be a feasible alternative to thermal processing to minimize browning and viscosity loss in strawberry juice during storage.     

Short-wave ultraviolet-C light effect on pitaya (Stenocereus griseus) juice inoculated with Zygosaccharomyces bailii

Fresh pitaya (Stenocereus griseus) juice was inoculated with Zygosaccharomyces bailii to be processed using a continuous ultraviolet-C light (UV-C) (57 μW/cm²) system. Inoculated and uninoculated juices were processed at selected flow rates (16.49, 23.78, and 30.33 mL/s) and treatment times (5, 10, 15, 20, 25, and 30 min). Untreated, inoculated, and uninoculated pitaya juices were stored at 4 °C during 25 days. Microbiological (yeasts plus molds and total counts) and physicochemical (pH, total soluble solids, color, phenolic compounds, betalains, and antioxidant activity) characteristics were evaluated in fresh and processed juices. The net change in color increased as treatment time increased, reaching a maximum value of 3.9. A substantial reduction of phenolic compounds (11.6%), betalains (14.6%), and antioxidant activity (37.0%) were observed in juice treated at 30.33 mL/s during 30 min. A reduction of 1.8 log cycles of Z. bailii was observed at the highest UV-C light treatment.     

Effects of UV-C,red light and sun light on the carotenoid content and physical qualities of tomatoes during post-harvest storage

Mature-green (breaker-stage) tomatoes were harvested and treated daily with short bursts of UV-C, red light or sun light for up to 21 days. Control untreated tomatoes were kept in the dark for the same period. The effects of the treatments on the levels of the major tomato carotenoids, skin colour, tissue firmness and total soluble refractive solids were evaluated throughout storage. Results indicated that the concentration of lycopene in tomato exocarp was significantly increased after 4 days and dramatically enhanced by UV-C or red light treatments. However, the concentration of β-carotene was not affected by UV-C or red light treatments, and decreased by sun light treatment during 21 days of storage, compared to the control samples. The colour (a∗ and b∗ values) and force required to penetrate the tomatoes was, to a small but significant extent, influenced by the light treatments. However, the total soluble refractive solids of all tomato samples remained the same throughout storage. The findings reported here could be employed to improve tomato nutritional qualities lycopene content without inducing significant changes to the physical properties of tomatoes during post-harvest storage.     

Volatile compounds and changes in flavour‐related enzymes during cold storage of high‐intensity pulsed electric field‐ and heat‐processed tomato juices

BACKGROUND: The effects of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs, using 4 µs bipolar pulses at 100 Hz) on the production of volatile compounds and flavour‐related enzymes in tomato juice were investigated and compared with those of thermal processing (90 °C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 °C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 °C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 °C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF‐treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat‐treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments. Copyright © 2010 Society of Chemical Industry     

Quality Changes in Mango Juice Treated by High-Intensity Pulsed Electric Fields Throughout the Storage

The effect of high-intensity pulsed electric fields (HIPEF) processes on Listeria innocua inhibition, physicochemical parameters and activity of oxidative enzymes of mango juice was evaluated to set the optimal HIPEF treatment time. Quality parameters, microbial population and bioactive compounds of HIPEF-treated (35 kV/cm, 1800 μs) and thermally treated (TT) (90 °C, 60 s) mango juices were studied and compared with those non-treated during 75 days of storage at 4 °C. HIPEF treatment for 800 μs ensured 5 log reductions of L. innocua. Polyphenoloxidase (PPO), lipoxygenase (LOX) and peroxidase (POD) residual activities were significantly reduced to 70, 53 and 44%, respectively, at treatment times of 1800 μs. Similar sensory properties compared with fresh mango juice were attained from product treated at 1800 μs. Moreover, fresh mango juice colour (L* = 38.79, h° = 106.57) was preserved after HIPEF treatment throughout storage. Moulds and yeasts and psychrophilic bacteria counts in HIPEF-treated (1800 μs) mango juice remained below 6 log cycles CFU/mL up to 2 months of refrigerated storage. The content of total phenolic compounds in those HIPEF-treated increased from 333 to 683 μg of GAE/mL from day 0 to the end of storage. Hence, the application of HIPEF may be a feasible treatment in order to ensure microbiological stability, high bioactive compound content and fresh-like characteristics of mango juice.     

Phenolic acids, flavonoids, vitamin C and antioxidant capacity of strawberry juices processed by high-intensity pulsed electric fields or heat treatments

The effect of high-intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1,700 μs in bipolar 4-μs pulses at 100 Hz) on individual phenolic compounds (phenolic acids and flavonoids), vitamin C and antioxidant capacity of strawberry juice was evaluated and compared to heat (90 °C for 60 or 30 s) and fresh juice as a reference. Although strawberry juice underwent a substantial depletion of health-related compounds with storage time irrespective of the treatment conducted, ellagic acid was enhanced. HIPEF-treated strawberry juice maintained higher amounts of phenolic acids (ellagic and p-coumaric acid) and total anthocyanins than the thermally treated juices during the storage period. Regarding the antioxidant capacity, similar DPPH and ABTS values were obtained so that differences among pasteurized juices were non significant. HIPEF processing may be a technology as effective as thermal treatments not only to achieve safe and stable juices, but also to obtain juices with a high content of antioxidant compounds.     

Effects of direct-electric-current on secondary plant compounds and antioxidant activity in harvested tomato fruits (Solanum lycopersicon L.)

The effects of direct-electric-current (DC) on secondary plant compounds and antioxidant activity in harvested tomato fruits were investigated. A new technology was developed to supply DC to the tomatoes. Different intensities of DC (100–500 mA) with varied application times (15–60 min) were applied during postharvest. Almost all DC treatments significantly affected the secondary metabolism, resulting in an accumulation of carotenoids, phenolic compounds, and antioxidant activity in tomatoes. In the present study, optimal DC treatments were found in order to obtain the highest content of all investigated secondary plant compounds. After an adaptation time (AT) of 2 h, the maximum contents of lycopene (122.4%), ß-carotene (140.4%), total phenol (120.0%), and antioxidant activity (126.5%) were attained with a DC treatment of 500 mA for 15 min. The results changed after an adaptation time of 24 h (AT 24 h), where the highest contents of lycopene (128.7%), ß-carotene (129.6%), total phenol (113.6%), and antioxidant activity (120.9%) were obtained using the same DC treatment (500 mA), but with an application time of 30 min. Therefore, the application of DC in harvested tomato fruits may be appropriate to improve the health-promoting properties of tomatoes.     

Comparative study on antioxidant properties of carrot juice stabilised by high‐intensity pulsed electric fields or heat treatments

BACKGROUND: The effect of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs using 6‐µs bipolar pulses at 200 Hz) on the antioxidant features (vitamin C, β‐carotene, total phenolic compounds and antioxidant capacity) of carrot juice as well as on peroxidase activity was investigated and compared to the observed in heat pasteurised juices (90 °C for 60 s or 30 s) having the fresh juice as a reference. RESULTS: HIPEF and heat‐treated carrot juices had higher β‐carotene and lower vitamin C contents than the untreated juices immediately after processing. The antioxidant capacity of the juices was significantly modified neither by HIPEF nor by thermal treatments. POD activity decreased drastically (≥93.3%) after processing irrespective of the treatment applied. Vitamin C and β‐carotene content decreased throughout the storage following an exponential trend (R² = 0.801–0.984) with degradation rates between 1.7 × 10^?2 and 3.5 × 10^?2 day^?1. Vitamin C and β‐carotene contents were better maintained in HIPEF‐treated than in heat‐pasteurised juices throughout the storage. Total phenolic content and the antioxidant capacity of the HIPEF‐treated juice did not substantially differ from that of the thermally treated juice for 56 days. CONCLUSION: HIPEF processing may help to achieve fresh‐like carrot juices with increased amounts of health‐related phytochemicals. Copyright © 2009 Society of Chemical Industry     

Industrial orange juice debittering: Impact on bioactive compounds and nutritional value

The impact of an industrial debittering process (DP) on nutritional and bioactive compounds in orange juice (OJ) was studied. The DP was aimed at removing bitter components in OJ by physical adsorption in a resin. The levels of bioactive compounds (carotenoids, ascorbic acid and phenolics), total antioxidant activity and the colour in the fresh orange juices (non-debittered) and in the debittered counterparts were measured. The results demonstrated that the carotenoid contents were not significantly affected by the treatment. However, the debittered orange juices showed a reduction (p < 0.001) of 26% in ascorbic acid, 32% in hydroxycinnamic acids, 28% of flavones and 41% of flavanones in comparison with the non-treated juices. The antioxidant activity of the hydrophilic fraction (HF) was significantly higher (p < 0.05) in untreated juice than in debittered juices. Some colour parameters (L^∗, a^∗ and h_ab) were also affected. Discriminant analysis revealed that the canonical function related to the levels of HF compounds allowed a 100% correct classifications of the different types of juices.     

Concentration of camu–camu juice by the coupling of reverse osmosis and osmotic evaporation processes

The objective of this work was to evaluate the technical feasibility of coupling two membrane separation processes, reverse osmosis (RO) and osmotic evaporation (OE), in order to concentrate clarified camu–camu juice, focusing on the vitamin C, phenolic compounds and antioxidant activity of the final product. The juice was firstly pre-concentrated by RO, reaching 285 g kg⁻¹ of soluble solids. During this step, the juice’s osmotic pressure showed to be the main factor controlling mass transfer. The juice was then concentrated by OE, reaching 530 g kg⁻¹ of soluble solids. Vitamin C, total phenolics and antioxidant activity levels of 94.6 g ascorbic acid kg⁻¹, 105.2 g galic acid kg⁻¹ and 762 mmol Trolox kg⁻¹, respectively, were achieved in the final product. The use of integrated membrane processes proved to be an interesting alternative to the concentration of thermosensitive juices, reaching concentration levels up to 7 times for camu–camu juice’s bioactive compounds.     

Carotenoids and Their Geometry Isomers in Selected Tropical Fruits

This study determined the carotenoids content in cherry tomato, pink guava, and red grapefruit pulps and juices. Cherry tomato pulp exhibited the highest β-carotene content whereas pink guava pulp had the highest lycopene content. However, β-carotene and lycopene contents in the studied fruit juices were lower than their pulps in the same sample portion. Interestingly, six to twelve cis-isomers of carotenoids were identified in the fruit pulps and juices studied. A higher number of trace amounts of cis-carotenoids was found in fruit pulps as compared to juices. Therefore, consumption of whole fruit is recommended as the studied fruit juices have lower carotenoids content.