Inactivation Kinetics of Pectin Methylesterase,Polyphenol Oxidase,and Peroxidase in Cloudy Apple Juice under Microwave and Conventional Heating to Evaluate Non-Thermal Microwave Effects

Continuous-flow microwave pasteurization provides important advantages over conventional heat exchangers such as fast volumetric heating, lower tube surface temperature, and possible non-thermal effects that enhance enzymatic and bacterial inactivation. Conventional and microwave-assisted inactivation of pectin methylesterase (PME), polyphenol oxidase (PPO), and peroxidase (POD) in cloudy apple juice were investigated to evaluate non-thermal effects. Experiments were conducted to provide uniform heating with accurate temperature acquisition and similar temperature profiles for conventional and microwave treatments. A two-fraction first-order kinetic model was successfully fitted to the data in a procedure that took into account the whole time-temperature profile instead of assuming isothermal conditions. Predicted inactivation curves for pasteurization at 70 and 80 °C of the cloudy apple juice showed that PME has the highest thermal resistance (residual activity of 30% after 250 s at 80 °C) and that there was no evidence of non-thermal microwave effects on the inactivation of these enzymes.     

Thermosonication of peach juice: investigation of PPO and POD activities,physicochemical and bioactive compounds changes,and development of FT-IR–based chemometric models for the evaluation of quality

In this research, the effect of thermosonication on peach juice was investigated. Enzyme inactivation increased with increasing power, temperature, and time. Enzymes were completely inactivated by thermosonication at 60 °C that was lower than the complete inactivation temperature (70 °C) of thermal treatment. Generally, as pH decreased, titratable acidity and °Brix increased by increasing temperature for each thermosonication treatment. The color of peach juice was preserved, and it became lighter. The bioactive components were protected with thermosonication. Fourier transform infrared (FT-IR) spectroscopy with chemometrics was used to evaluate polyphenol oxidase and peroxidase activity and quality attributes during thermosonication treatment. Moreover, the treatment methods were differentiated using principal component analysis, and models that correlated enzyme activity, quality attributes, and bioactive compounds with infrared spectra were constructed using partial least-squares. FT-IR with chemometrics can be used as a reliable method in peach juice quality determination during thermosonication.     

Thermosonication: a potential technique that influences the quality of grapefruit juice

Thermosonication (TS) is an emerging nonthermal processing technique used for the liquid food preservation and is employed to improve the quality and acceptability of grapefruit juice. In this study, fresh grapefruit juice samples were subjected to TS treatment in an ultrasonic cleaner with different processing variables, including temperature (20, 30, 40, 50 and 60 °C), frequency (28 kHz), power (70%, 420 W) and processing time (30 and 60 min) for bioactive compounds, inactivation of enzymes pectin methylesterase (PME), peroxidase (POD) and polyphenolase (PPO) and micro‐organisms (total plate count, yeasts and moulds). The micro‐organism activity was completely inactivated in the treatment (60 °C for 60 min). The TS treatment at 60 °C for 60 min exposure reduced PME, PPO and POD activity by 91%, 90% and 89%, respectively. Results indicate that the advantages of TS for grapefruit juice processing at low temperature could enhance the inactivation of enzymes and micro‐organisms and it can be used as a potential technique to obtain better results as compared to alone .     

Pasteurization of Apple Juice Contaminated with Escherichia coli by a Combined UV–Mild Temperature Treatment

The bactericidal efficacy of ultraviolet (UV) treatments to fruit juices is limited because of their low UV transmittance; therefore, it is necessary to design combined processes to improve their lethality. This investigation was carried out to determinate the lethal effect of UV-C treatments at mild temperatures (UV-H treatments) on the UV-resistant Escherichia coli strain Spanish Type Culture Collection (STCC) 4201 suspended in apple juice. A synergistic effect was observed and the optimum temperature for the combined process was established. Subsequently, the effect of the optimized treatment on the lethality of an E. coli cocktail (STCC 4201, STCC 471, American Type Culture Collection (ATCC) 27325, ATCC 25922, and O157:H7 Chapman strain) and on freshly squeezed apple juice quality was evaluated. A UV treatment of 20.33 J/mL reached 0.61?±?0.01, 0.83?±?0.07, 1.38?±?0.04, 1.97?±?0.06, 3.72?±?0.14, 5.67?±?0.61, and more than 6 log₁₀ cycles of inactivation at 25.0, 40.0, 50.0, 52.5, 55.0, 57.5, and 60.0 °C, respectively. The optimum conditions for exploiting the synergistic effects were UV doses of 27.10 J/mL, temperature of 55.0 °C, and 3.58 min of treatment time. This treatment guaranteed more of 5 log₁₀ reductions of the cocktail of five strains of E. coli without affecting pH, °Brix, and acidity of freshly squeezed apple juice. The UV-H treatment did not increase the loss of ascorbic acid compared to the same UV treatment at room temperature but approximately doubled the inactivation of polifenoloxidase.     

Textural Changes of Yellow Peach in Pouches Processed by High Hydrostatic Pressure and Thermal Processing During Storage

Textural changes of yellow peach in pouches (YPP) treated by high hydrostatic pressure (HHP) and thermal processing during storage at 4?±?1 °C and 25?±?1 °C for 180 days were studied. Hardness, syrup viscosity, pectin compositions, and cell structure of YPP samples were evaluated in this study. The hardness of YPP stored at 4?±?1 °C exceeded 50–70 % as compared to those stored at 25?±?1 °C. Moreover, the higher flesh hardness and lower syrup viscosity were obtained at longer pressure-holding time of HHP processing. Water-soluble pectin (WSP), sodium carbonate-soluble pectin (NSP), and total pectin contents in flesh decreased, while chelate-soluble pectin (CSP) in flesh and water-soluble pectin in syrup (WSPS) increased after 180 days storage. The texture degradation in YPP was mainly caused by solubilization and depolymerization of WSP and NSP. The temperature of 4?±?1 °C inhibited pectin degradation and delayed the softening of flesh and the increase of syrup viscosity more effectively than 25?±?1 °C. Comparing with the flesh tissue microstructure of HHP-processed YPP stored at 25?±?1 °C, better cell structures of YPP were retained during storage at 4?±?1 °C. Since the breakdown of intercellular cementing pectin was obviously delayed at lower storage temperature, thus cell wall loosening and distortion were prevented.     

Enzyme Activity and Nutritional Quality of Peach (Prunus persica) Juice: Effect of High Hydrostatic Pressure

The inactivation of polyphenol oxidase and pectin methylesterase in peach juice was investigated after high hydrostatic pressure processing at 400–600 MPa and 25°C for 5–25 min, respectively. At 400 MPa, polyphenol oxidase and pectin methylesterase were activated by 7.3 and 2.6%. At 500 and 600 MPa, polyphenol oxidase and pectin methylesterase were inactivated significantly with increasing the pressure and time, and the inactivation kinetics was fitted by the first order model. Moreover, some physio-chemical properties were studied. The results revealed that high hydrostatic pressure treatment preserved more L-ascorbic acid and maintained the color and sensory quality better than thermal treatment.     

Optimisation of High Hydrostatic Pressure Processing of Pêra Rio Orange Juice

The influence of high hydrostatic pressure (HHP) on Pêra Rio orange juice was investigated using response surface methodology. A central composite design was used to evaluate the effects of three processing conditions (independent variables), namely pressure (100–600 MPa), temperature (30–60 °C) and time (30–360 s), on the native microflora and pectin methylesterase (PME) activity of orange juice. Analysis of variance showed that second-order polynomial models fitted well with the experimental data for PME residual activity (R ²?=?0.9586, p?<?0.001) and aerobic microorganism count (R ²?=?0.9879, p?<?0.001). The optimum HHP processing conditions to produce orange juice with PME residual activity of less than 20 % and low microorganism count (<2 log cycles CFU/mL) were 550 to 600 MPa, 55 to 60 °C and 330 to 360 s.     

Inactivation kinetics of food enzymes during ohmic heating

Ohmic heating of milk and fruit and vegetable juices was carried out at several incubation temperatures to investigate inactivation of alkaline phosphatase, pectin methylesterase and peroxidase. Mechanisms of inactivation of these enzymes and corresponding kinetic models were verified for each food material, using the multitemperature evaluation of inactivation data. Compared to inactivation by conventional indirect heating, kinetic parameters were changed but inactivation mechanisms remained the same. The kinetic parameter changes were relatively minor for pectin methylesterase and alkaline phosphatase. A significant destabilization of the labile isozyme fraction of peroxidase occurred by the effect of ohmic heating when the greatest decrease of stability was obtained for carrot juice.     

Effect of Cold Atmospheric Plasma on Inactivation of <Emphasis Type="Italic">Escherichia coli</Emphasis> and Physicochemical Properties of Apple,Orange, Tomato Juices,and Sour Cherry Nectar

In this study, orange, tomato, apple juices, and sour cherry nectar were exposed to an atmospheric pressure plasma jet. Plasma treatments were carried out using air as a precursor under constant gas flow (3000 L/h) at 650 W for different treatment times (30, 60, 90, and 120 s). After plasma processing, reduction of Escherichia coli, Hunter’s color parameters (L*, a*, b*), total phenolic content, and pH values were evaluated. The inactivation effect of cold atmospheric plasma (CAP) was investigated on E. coli, and the highest significant reductions were achieved in apple juice (4.02 ± 0.03 log CFU/mL) followed by sour cherry (3.34 ± 0.09 log CFU/mL), while the values in orange (1.59 ± 0.17 log CFU/mL) and tomato juices (1.43 ± 0.22 log CFU/mL) were lower, which could be attributed to the food matrix. Color parameters, except for apple juice, did not show significant changes after processing. Compared to untreated juice, plasma treatment yielded higher phenolic content from 10 to 15%, while pH values did not change significantly and the temperature remained below 40 °C after all plasma treatments. This study showed that CAP treatment had positive influences on phenolic stability and color change in all samples regardless of food intrinsic factors, while it was more effective on bacterial inactivation in clear juices than turbid ones. Our results indicate that atmospheric plasma appears to be a promising technology for microbial inactivation without causing undesirable changes in food product.     

Comparative inactivation studies of <Emphasis Type="Italic">Aegle marmelos</Emphasis> (<Emphasis Type="Italic">bael</Emphasis>) peroxidase in crude extract of fruit by heat processing and ultrasonication treatment

Bael (Aegle marmelos) is considered as a holy fruit comprised of vast number of phytonutrients. Whole bael tree including all its parts has medicinal significance. Lack of awareness and seasonal nature makes its processing rather challenging. Conventional heat processing may lead to inactivation of quality hampering enzymes such as peroxidase, but at the cost of loss in essential phytonutrients. In the present work it was observed that thermal inactivation of bael peroxidase obeyed first order kinetics with enzyme activation energy of 7.7 kJ mol^?1. Complete inactivation of bael peroxidase was achieved within 11 min at 85?°C while ultrasound treatment attained in lesser time of 4 min at 64.07 W cm^?2 ultrasonic intensity. Loss of marmelosin a well-known phytonutrient in bael fruit was found to be 83.29?% by heat (11 min, 85?°C) and only 50.20?% by ultrasonication (4 min, 64.07 W cm^?2 ultrasonic intensity). Ultrasonication has potential to overcome harmful effects of heat processing with retention of phyto-constituents and hence has promising future in various food processing applications.     

Comparative study on color,viscosity and related enzymes of tomato juice treated by high-intensity pulsed electric fields or heat

The effects of high intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1,500 μs using bipolar 4-μs pulses at 100 Hz) on color parameters and viscosity, as well as peroxidase (POD), pectin methylesterase (PME) and polygalacturonase (PG), were evaluated during 77 days of storage at 4 °C and compared to thermal treatments at 90 °C for 1 min or 30 s for unprocessed tomato juice. HIPEF-treated tomato juice showed higher values of lightness than the thermally processed and the untreated juice throughout storage time (P < 0.05). Viscosity of HIPEF-treated tomato juice was also greater than both thermally treated and untreated for the first 35 days of storage. POD of HIPEF-treated tomato juice was inactivated by 97% whereas in the case of the thermally treated, 90 and 79% inactivation was achieved after 1 min and 30 s, respectively. The highest PME inactivation in tomato juice was obtained by PEF (82%) and heat treatment at 90 °C for 1 min (96%). PG of PEF-treated tomato juice was inactivated by 12% whereas thermal treatments at 90 °C for 1 min or 30 s achieved 44 and 22%, respectively. Despite the low rates of PG inactivation obtained, the pattern followed in the residual activity along the storage time was similar in the tomato juice treated by HIPEF than the thermally processed.     

Effect of Ultrafiltration Combined with High-Pressure Processing on Safety and Quality Features of Fresh Apple Juice

Ultrafiltration (UF, 0.05 μm) with a ceramic membrane was combined with high-pressure processing (HPP) at 500 MPa/6 min and high-temperature short time (HTST) at 110 °C/8.6 s to process fresh apple juice. The aim of this study was to compare the effect of UF + HPP and UF + HTST on quality features of fresh apple juice and analyze the quality changes of the juice treated by UF + HPP and stored during 60 days at 4 °C. Applying UF, total plate count (TPC) and yeasts and molds (Y&M) significantly decreased by 0.29 and 0.28 log cycle, total phenols and ascorbic acid decreased by 33.50 and 26.52 %, and antioxidant capacity, using the DPPH and FRAP assay, significantly decreased by 26.40 and 25.37 %. Meanwhile, the juice clarity was 99.75?±?0.07 % and seven aroma compounds were changed. TPC and Y&M in juices treated by UF + HPP and UF + HTST were <1 log cycle. When compared to the juice treated by UF + HTST, the juice treated by UF + HPP showed lower browning degree and higher total phenols and clarity, and retained seven main volatile aroma compounds. Fresh apple juice processed by UF + HPP was microbiologically safe (TPC <1.8 log cycles and Y&M <1 log cycle) during 60 days of storage at 4 °C. The first-order model was a suitable model for all quality parameters of refrigerated fresh apple juice; however, rate constant k of first-order model was between ?0.0157 and 0.0350, showing the quality features of the refrigerated juice was stable.     

Effect of a combination of electrodialysis with bipolar membranes and mild heat treatment on the browning and opalescence stability of cloudy apple juice

The purpose of this work was to develop a process enabling the quick inactivation of the polyphenol oxidase and pectin methylesterase enzymes, which are present in cloudy or unclarified apple juice; These enzymes are respectively responsible for enzymatic browning and opalescence instability. In order to fulfill this objective, acidification of the apple juice to pH 2.0 was conducted by electrodialysis (bipolar–anionic membranes) followed by mild heat treatment at temperature of 40, 45 and 50 °C for a duration of 0–60 min. Then, juice pH was readjusted to its initial value by electrodialysis with bipolar–anionic membranes. It was shown that a mild heat treatment at 45 °C for 5 min performed on the acidified juice represents an appropriate condition to quickly inactivate the enzymes. Furthermore, the organoleptic properties of the juice after treatment were found to be preserved and the adjusted juice (pH readjusted to its initial value) shows a better color than an untreated apple juice. Opalescence of the adjusted juice was also more stable than for an untreated cloudy apple juice, when stored at 4 °C for 3 months.     

High Pressure and Temperature Effects on Enzyme Inactivation in Strawberry and Orange Products

High hydrostatic pressure treatment (50-400 MPa) combined with heat treatment (20–60°C) effects on peroxidase (POD), polyphenoloxidase (PPO) and pectin methylesterase (PME) activities of fruit-derived products were studied. Assays were carried out on fresh orange juice and strawberry puree. Pressurization/depressurization treatments caused a significant loss of strawberry PPO (60%) up to 250 MPa and POD activity (25%) up to 230 MPa, while some activation was observed for treatments carried out in 250–400 MPa range for both enzymes. Optimal inactivation of POD was using 230 Mpa and 43°C in strawberry puree. Combinations of high pressure and temperature effectively reduced POD activity in orange juice (50%) to 35°C. The effects of high pressure and temperature on PME activity in orange juice were very similar to those for POD.     

Thermal inactivation kinetics parameters of browning enzymes in starfruit (Averrhoa carambola L.) juice

This study aimed to evaluate the thermal inactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in starfruit juice. It followed the Malaysia Food Regulations 1985 and CODEX STAN 247-2005. Glucose, fructose and sucrose were the main sugars in starfruit juice. The total soluble solids, pH, titratable acidity, and total phenolics content of the starfruit juice produced were 8.13 ± 0.25 °Brix, 3.80 ± 0.05, 0.43% ± 0.02% malic acid, and 93.67 ± 4.96 mg GAEL⁻¹, respectively. Thermal inactivation kinetics of PPO and POD followed the first-order kinetic model. The decimal reduction time at 83.6 °C (D_83.6) of PPO and POD was 198.48 and 98.4 s, respectively, while the thermal resistance constant (z value) of PPO and POD was 12.8 and 5.4 °C, respectively. In conclusion, PPO might be a suitable signal for thermal processing on starfruit juice since it has higher heat resistance than POD.     

超高压处理对鲜橙汁中果胶酶及过氧化物酶活性的影响

为推进国内非冷冻浓缩橙汁加工业的发展,对新型超高压杀菌技术对橙汁中酶钝化的效果进行研究,采用200～600MPa超高静压处理鲜榨橙汁,使用紫外分光光度法、滴定法分别测定鲜橙汁中过氧化物酶(POD)和果胶酶(PME)的活性,进行两种酶在常温下超高压钝化酶一级动力学拟合研究。结果表明：在常温条件下200MPa处理10min使两种酶轻微激活,在300～600MPa条件下,随压力和处理时间的增大,两种酶钝化反应明显,且符合一级动力学模型,且果胶酶对压力钝化更加敏感。     

Evaluation of Microbial Stability,Bioactive Compounds,Physicochemical Properties,and Consumer Acceptance of Pomegranate Juice Processed in a Commercial Scale Pulsed Electric Field System

This paper investigated the feasibility for pasteurizing raw (100 %) pomegranate juice in a commercial scale pulsed electric field (PEF) processing system. The juice was processed at 35 and 38 kV/cm for 281 μs at 55 °C with a flow rate of 100 L/h. Effect of PEF processing on microbial stability, color, °Brix, pH, sediment, antioxidant activity, total phenolic content, anthocyanin, and sensory properties after the treatments and during storage at 4 °C for 12 weeks were studied and compared to those of thermally processed juice. PEF treatments significantly (p?<?0.05) inhibited the growth of total aerobic bacteria, which remained at <2.5 log colony-forming units (CFU)/ml during the 12-week storage. No yeast and mold were detected (<0.69 log CFU/ml) in the PEF-treated juices during storage up to weeks 10 and 12, which is similar to the thermally processed juice. There were no significant differences in pH and °Brix values between the PEF processed juice and unprocessed juice. PEF processing did not alter the contents of total phenolics and anthocyanin as compared to unprocessed juice. PEF processing had significantly (p?<?0.05) less impact on the color of pomegranate juice than thermal processing. PEF-treated juice had the same consumer satisfaction scores as the unprocessed juice, which were significantly (p?<?0.05) higher than thermally processed juice samples. There was no significant difference between the two PEF treatments in all results. This study demonstrated that PEF technology extended microbial shelf-life and preserved the major quality and nutritional characteristics of pomegranate juice, and hence, is technically feasible for commercialization in the juice industry.     

Ultraviolet Light-Assisted Photocatalytic Disinfection of <Emphasis Type="Italic">Escherichia coli</Emphasis> and Its Effects on the Quality Attributes of White Grape Juice

Ultraviolet (UV) light-assisted titanium dioxide (TiO₂) photocatalysis is an emerging technology in food safety that utilizes TiO₂ photocatalysts to accelerate the generation of reactive oxygen species during UV illumination. In this work, we studied the use of immobilized TiO₂-SiO₂ photocatalysts illuminated with UVA radiation (350 nm; 14.8 mW/cm²) for the inactivation of Escherichia coli ATCC 25922 in white grape juice, and compared the effectiveness of the photocatalytic disinfection with respect to the quality attributes of white grape juice against those of thermal and UVC (254 nm; 19.7 mW/cm²) treated samples. To obtain a 5-log reduction of the target microorganism, treatment durations of UVA in the absence and presence of the photocatalyst were 60 and 40 min, respectively. A 5-log reduction with UVC radiation led to the loss of health-related compounds such as vitamin C, total phenolic content, and total antioxidant capacity at 92.0?±?1.1%, 19.4?±?5.6%, and 54.3?±?10.0%, respectively. However, the same level of reduction with UVA led to a loss of 74.2?±?2.3%, 7.1?±?3.6%, and 39.7?±?2.5%, and with UVA-assisted photocatalytic method resulted in a loss of 75.8?±?6.1%, 13.6?±?5.8%, and 45.6?±?4.4% of vitamin C, total phenolic content, and total anti-oxidant capacity, respectively. Given its efficacy in deactivating E. coli while retaining a relatively higher level of health-related constituents in the fruit juice compared to other common pasteurization techniques, the photocatalyst developed in this study provides a promising technology for food disinfection.     

Effects of pulsed thermosonication treatment on fungal growth and bioactive compounds of Berberis vulgaris juice

In this study, the single and combined effects of pulsed‐ultrasound amplitude (100 W, 30 kHz with 25 and 50% amplitude levels for up to 30 min) and temperature (65 °C and 75 °C) on fungal growth, total phenolics, flavonoids and antioxidant activity of Berberis vulgaris juice were investigated. The combination of pulsed ultrasound at 50% amplitude for 30 min at temperature of 75 °C as the most effective treatment was resulted in a reduction of about?3.083 ± 0.02, ?3.04 ± 0.03, ?3.10 ± 0.01 and ?2.88 ± 0.02 log (N/N₀) on S. cerevisiae, A. flavus, A. versicolor and B. fulva, respectively. Additionally, the highest total phenolics, flavonoids and antioxidant activity were noted for the barberry juice after 30 min of sonication with 50% pulsed‐ultrasound amplitude at either 65 °C or 75 °C. Pulsed thermosonication is a promising technology to extend the shelf life of B. vulgaris fruit juice because of the improvement of antioxidant activity as well as microbial quality.     

Thermal Stability of Ricin in Orange and Apple Juices

ABSTRACT: Ricin is a potent protein toxin that could be exploited for bioterrorism. Although ricin may be detoxified using heat, inactivation conditions in foods are not well characterized. Two brands of pulp-free orange juice and 2 brands of single-strength apple juice (one clarified and the other unclarified) containing 100 μg/mL added ricin were heated at 60 to 90 °C for up to 2 h. With increasing heating times and temperatures the heat-treated juices exhibited decreasing detectability of ricin by enzyme-linked immunosorbent assay (ELISA) and cytotoxicity to cultured cells. Z-values for ricin inactivation in orange juices were 14.4 ± 0.8 °C and 17 ± 4 °C using cytotoxicity assays, compared to 13.4 ± 1.5 °C and 14 ± 2 °C determined by ELISA. Although insignificant differences were apparent for z-values measured for the 2 orange juice brands, significant differences were found in the z-values for the 2 brands of apple juice. The z-values for ricin inactivation in the clarified and unclarified apple juices were 21 ± 4 °C and 9.5 ± 1.1 °C, determined by cytotoxicity assays, and 20 ± 2 °C and 11.6 ± 0.7 °C, respectively, using ELISA. Overall, there were no significant differences between results measured with ELISA and cytotoxicity assays. Ricin stability in orange juice and buffer was evaluated at 25 °C. Half-lives of 10 ± 3 d and 4.9 ± 0.4 d, respectively, indicated that active ricin in juice could reach consumers. These results indicate that ricin in apple and orange juices can remain toxic under some processing and product storage conditions. Practical Application: Ricin is a potent toxin that is abundant in castor beans and is present in the castor bean mash by-product after cold-press extraction of castor oil. U.S. Health and Human Services recognizes that ricin could be used for bioterrorism. This study reports the stability of ricin in apple and orange fruit juices at temperatures ranging from 60 to 90 °C (140 to 194 °F).