The Application and Optimization of HIPEF Technology in the Processing of Juice from Strawberries Harvested at Two Stages of Ripeness (original) (raw)
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LWT-Food Science and …, 2009
Novel non-thermal processing technologies such as high-intensity pulsed electric field (HIPEF) treatments may be applied to pasteurize plant-based liquid foods as an alternative to conventional heat treatments. In recent years, there has been an increasing interest in HIPEF as a way of preserving and extending the shelf-life of liquid products without the quality damage caused by heat treatments. However, less attention has been paid to the effects of HIPEF on minor constituents of these products, namely bioactive compounds. This review is a state-of-the-art update on the effects of HIPEF treatments on healthrelated compounds in plants of the Mediterranean diet such as fruit juices, and Spanish gazpacho. The relevance of HIPEFprocessing parameters on retaining plant-based bioactive compounds will be discussed.
LWT - Food Science and Technology, 2009
The effects of high-intensity pulsed electric field (HIPEF) processing (35 kV/cm for 1700 ms applying 4-ms 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.
Lwt - Food Science and Technology, 2010
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 ms, the treatments were set at frequencies from 50 to 250 Hz, pulse width from 1 to 7 ms using monopolar or bipolar mode. A second order response function covering the whole range of experimental conditions was obtained for each healthrelated 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 ms 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.
Journal of Food Science and Technology, 2014
The influence of Pulsed Electric Field (PEF) pretreatment of blueberry fruits (Vaccinium myrtillus L.), both on the extraction yield and antioxidant properties of juice obtained by pressing and on the on the recovery of bioactive compounds from berry by-products (press cake) by extraction with solvent, was investigated. PEF treatments carried out at field strengths of 1, 3, and 5 kV/cm and an energy input of 10 kJ/kg achieved a cell disintegration index (Z p) of 0.70, 0.80, and 0.87, respectively. Mechanical pressing (1.32 bar for 8 min) of PEF-treated berries (1, 3, and 5 kV/cm at 10 kJ/kg) significantly increased the juice yield (+28 %) compared with the untreated sample. The juice obtained from PEF pre-treated berries also had a significantly higher total phenolic content (+ 43 %), total anthocyanin content (+60 %) and antioxidant activity (+31 %). However, PEF treatment intensity higher than 1 kV/cm did not significantly improve the quantitative or qualitative characteristics of the juice. Compared to the untreated sample, higher amounts of total phenolics (+ 63 %), total athocyanins (+78 %) and antioxidant activity (+ 65 %) were detected in the press cake extracts. PEF treatment of higher intensity resulted in better extractability of bioactive compounds from blueberry press cake. The results obtained from this study demonstrate the potential of PEF as a mild pretreatment method to improve the efficiency of the industrial processing of berry fruits.
Food Chemistry, 2009
The effects of high-intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1700 ls using pulses of 4 ls at 100 Hz in bipolar mode) and thermal treatments (90°C for 30 s or 60 s) on lipoxygenase (LOX) and b-glucosidase (b-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 heattreated juices during the first 28 days of storage. Moreover, b-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.
Food Control, 2011
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 ms, the treatments were set at frequencies from 50 to 250 Hz, pulse width from 1 to 7 ms using monopolar or bipolar mode. A second order response function covering the whole range of experimental conditions was obtained for each healthrelated 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 ms 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.
Influence of different pulsed electric field strengths on the quality of the grapefruit juice
Grapefruit juice was investigated using pulsed electric fields (PEF) with (electric field strengths: 0, 5, 10, 15, 20 and 25 kV cm À1 ; flow rate: 80 mL min À1 ; pulse frequency: 1 kHz at 40 °C for 600 ls). Total phenolics, DPPH, total antioxidant capacity (TAC), total anthocyanins, total carotenoids, sugars and physicochemical properties of grapefruit juice were studied. In addition, the effect of PEF treatment on microorganisms was also observed. Results indicated that no significant change was observed in pH, Brix, titratable acidity, sugars , total anthocyanins and colour attributes with the increase in pulsed electric strength as compared to control treatment. However, significant decrease in nonenzymatic browning (NEB) and viscosity while an increase in cloud value, DPPH, TAC, total phenolics and total carotenoids, while reduction in the activity of microorganisms , was also observed with the increase in pulsed electric strength as compared to control treatment. This study suggested that PEF at 25 kV cm À1 could improve the quality of grapefruit juice.
Zemdirbyste-Agriculture, 2016
Pulsed electric field (PEF) is a non thermal treatment, which could be employed for plant tissue disintegration which leads to increased juice yield and enhanced extraction of bioactive compounds. Since 97% of red raspberries (Rubus idaeus L.) are sold processed into juices or other products, it is important to increase juice yield and bioactive compounds extraction. This study investigated the effect of PEF pretreatment on red raspberries processing. After PEF pretreatment and mechanical pressing (1.32 bar for 6 min) the juice recovery from raspberries increased in the range of 9-25%. Compared to the untreated sample, press cake extracts contained significantly higher amounts of total phenolics (up to 22%), total anthocyanins (up to 26%) and higher ferric reducing antioxidant power (FRAP) (up to 24%). Mild PEF pretreatment (1 kV cm-1 electric field strength and 6 kJ kg-1 total specific energy) was sufficient to achieve higher raspberry juice recovery and to enhance extraction of bioactive compounds from raspberry press cake left after the juice pressing. PEF pretreatment of red raspberries is a promising technique to improve the efficiency of industrial processing of raspberries.
Food Engineering Reviews, 2020
Understanding the efficacy of viable emerging technologies in preserving overall quality attributes and antioxidant characteristics of fruit juices is of great interest. This study aimed to evaluate the effect of high pressure (HP), ultrasound (US), and pulsed electric fields (PEF) processes on natural microbiota inactivation, as well as changes in physicochemical attributes and phytochemical content of strawberry juice (SJ). HP at 300 MPa (1 min), US at 55°C (3 min) and 517.1 mW/mL acoustic energy density, and PEF at 35 kV/cm (27 μs) using monopolar square pulses with 2 μs pulse width were applied, and then compared with a conventional thermal pasteurization treatment (72°C, 15 s). The nonthermal processes were equivalent in terms of Escherichia coli (E. coli) inactivation since the selected processing conditions led to almost identical inactivation level (at least 5-log) of inoculated E. coli. The current study analyzes why these equivalent processes had different effect on SJ quality. All treatments significantly reduced the initial natural microbiota (i.e., total mesophilic aerobic bacteria and yeast-molds) below 2 log CFU/mL. No significant changes were observed on the total soluble solid content (7.83-8.00°Brix), titratable acidity (0.79-0.84 g/100 mL), and pH (3.45-3.50; except in sonication) between SJ processed samples and the untreated ones (p > 0.05). HPP and PEF significantly promoted higher retention of total phenolic content (TPC) and radical scavenging activity (RSA) than thermal pasteurization, and significantly enhanced total anthocyanin content (TAC) compared with unprocessed SJ. HPP and PEF increased the TPC (4-5%), RSA (18-19%), and TAC (15-17%) in comparison with unprocessed SJ. Multivariate data analysis tools, i.e., principal component analysis (PCA) and hierarchical cluster analysis (HCA), were successfully applied for discrimination and classification of SJ samples based on the similarities or differences among physicochemical and phytochemical characteristics. PCA and HCA indicated that HPP-and PEF-treated samples had similar enhanced properties in terms of phytochemical content and were superior to sonicated, thermally pasteurized, and unprocessed samples. The multivariate data analysis methods were very useful to compare and classify SJ quality characteristics as a function of the processing technology. This study demonstrated that the application of the equivalent processing approach may reveal new opportunities to produce equivalent or even enhanced quality fruit juices.
Journal of Food Process Engineering, 2020
The aim of this study was to investigate the effect of pulsed electric fields (PEF) on bioactive compounds and physiochemical properties present in apricot juice. In which 0, 7, and 14 kV/cm of PEF intensity were applied to treat the juices with a flow rate of 40 ml/min, frequency of 1 kHz at 25 ± 2°C for 500 μs. Thereafter the phenolics, flavonoids, antioxidant volatile compounds, and physiochemical properties of juice were analyzed. Furthermore, the change in functional groups of biological compounds was investigated by Fourier‐transform infrared spectroscopy. Results indicated no significant change in pH, °Brix, and color in PEF treated sample even at increased PEF intensities as compared to untreated. A significant increase in cloud value, phenolic compounds, flavonoids, and antioxidant activity of the PEF treated sample was observed. A decrease in the browning index was observed as compared to unprocessed samples. The little variation in biological compounds was observed in PEF...