Comparing equivalent thermal, high pressure and pulsed electric field processes for mild pasteurization of orange juice. Part I: Impact on overall quality attributes

Mild heat pasteurization, high pressure processing (HP) and pulsed electric field (PEF) processing of freshly squeezed orange juice were comparatively evaluated examining their impact on microbial load and quality parameters immediately after processing and during two months of storage. Microbial counts for treated juices were reduced beyond detectable levels immediately after processing and up to 2 months of refrigerated storage. Quality parameters such as pH, dry matter content and brix were not significantly different when comparing juices immediately after treatment and were, for all treatments, constant during storage time. Quality parameters related to pectinmethylesterase (PME) inactivation, like cloud stability and viscosity, were dependent on the specific treatments that were applied. Mild heat pasteurization was found to result in the most stable orange juice. Results for HP are nearly comparable to PEF except on cloud degradation, where a lower degradation rate was found for HP. For PEF, residual enzyme activity was clearly responsible for changes in viscosity and cloud stability during storage.

Industrial relevance

Development of mild processing technologies with a minimal impact on fruit juice can be considered as a true alternative of fresh fruit. The present work presents a fair comparison of mild heat treated, high pressure (HP) and pulsed electric field (PEF) processed orange juice as an alternative for thermal pasteurization. Orange juices were monitored during two months of storage.     

Defining treatment conditions for pulsed electric field pasteurization of apple juice

The influence of temperature and the presence of N^α-lauroyl ethylester (ethyl lauroyl arginate, LAE) on the inactivation caused by continuous pulsed electric field treatments (PEF) in Escherichia coli O157:H7 suspended in apple juice have been investigated to define treatment conditions applicable at industrial scale that promote an equivalent safety level when compared with thermal processing. In the range of experimental conditions investigated (outlet temperature: 20-40 °C, electric field strength: 20-30 kV, treatment time: 5-125 μs) at outlet temperatures equal or lower than 55 ± 1 °C, the inactivation of E. coli O157:H7 treated in apple juice ranged from 0.4 to 3.6 Log₁₀ cycles reduction and treated in apple juice supplemented with LAE (50 ppm) ranged from 0.9 to 6.7 Log₁₀ cycles reduction.An empirical mathematical model was developed to estimate the treatment time and total specific energy input to obtain 5 Log₁₀ cycles reduction in the population of E. coli O157:H7 suspended in apple juice supplemented with 50 ppm of LAE at different electric field strengths and inlet temperatures. Treatment conditions established for E. coli O157:H7 were validated with other PEF resistant Gram-positive (Listeria monocytogenes, and Staphylococcus aureus) and Gram-negative (Salmonella enterica serovar Typhimurium) strains. When the treatment was applied to the apple juice, a treatment of 25 kV/cm for 63 μs corresponding with an outlet temperature of 65 °C and input energy of 125 kJ/kg was required to achieve more than 5 Log₁₀ cycles in the four strains investigated. The addition of LAE reduced the treatment time required to obtain an equivalent inactivation (> 5 Log₁₀ cycles) in the four microorganisms to 38.4 μs, the outlet temperature to 55 °C, and the input energy to 83.2 kJ/kg.     

Effects of pulsed electric field treatment of apple mash on juice yield and quality attributes of apple juices

The influence of apple mash treatment with pulsed electric fields (PEF) on yield and quality attributes of the resulting cloudy juices were investigated. Apple juice was produced at laboratory scale (400 g apples per lot) by mash treatment with pulsed electric fields at three different field intensities (1, 3, 5 kV/cm, n = 30 pulses) and manual pressing at room temperature. The juices were compared with untreated control juices of the same mash and with a juice after pectolytic mash treatment. Relative to the control samples, juice yield increased with increasing field intensities. The overall composition as described by pH, total soluble solids, total acidity, density, contents of sugar, malic acid and pectin, respectively, as well as the nutritive value with respect to polyphenol contents and antioxidant capacities (TEAC, FRAP, DPPH) of the PEF-treated apple juices did not significantly differ from the controls.Industrial relevanceThis paper addresses the composition of apple juice after mash treatment applying pulsed electric fields and maceration enzymes, respectively. Since substantial equivalence of products derived from novel technologies, such as PEF, relative to their conventionally produced counterparts is required according to European food law, this aspect is of great relevance, especially for commercialisation of fruit juices based on PEF technology. Furthermore, the nutritional value of juices produced at different pulsed electric field activities is of relevance for their marketing.     

Improving apple juice expression and quality by pulsed electric field on an industrial scale

This study investigated the Pulsed Electric field (PEF) effect on apple mash, regarding quantitative, qualitative and sensory attributes, on an industrial scale. PEF treatment (E = 650 V/cm, t_PEF = 23.2 ms, q = 32 kJ/kg) was applied to apple mash at the flow rate of 4400 kg/h in a module of colinear design made of four treatment chambers.Juice yield significantly increased from 71.1% to 76.3% due to PEF treatment. A significant increase of 8.8% was also observed for the native polyphenols concentration when an inhibitor of the enzymatic oxidation was added. Juice colour was significantly altered by the PEF treatment. The saturation in the yellow rose significantly from 17.9 to 26.8.The juice from treated mash was less turbid and was described by odour intensity and typical odour of apple significantly higher than the untreated sample. Similarly, the overall and typical taste of apple juice were significantly more intense. The chemical composition (Fructose, Glucose and Malic acid) of juice did not vary despite a significant increase of the dry matter for treated samples. On the contrary, a significant depletion of fructose and glucose was noted for the pomace from treated mash as compared to the control.     

Comparing equivalent thermal, high pressure and pulsed electric field processes for mild pasteurization of orange juice: Part II: Impact on specific chemical and biochemical quality parameters

The impact of thermal, high pressure (HP) and pulsed electric field (PEF) processing for mild pasteurization of orange juice was compared on a fair basis, using processing conditions leading to an equivalent degree of microbial inactivation. Examining the effect on specific chemical and biochemical quality parameters directly after treatment and during storage at 4 °C revealed only significant differences in residual enzyme activities. For pectin methylesterase inactivation, none of the treatments was able to cause a complete inactivation, although heat and HP pasteurization were the most effective in limiting the residual activity. Peroxidase was completely inactivated by heat pasteurization and was much less susceptible to HP and PEF. All other quality parameters investigated, including the sugar profile, the organic acid profile, bitter compounds, vitamin C (ascorbic acid and dehydroascorbic acid), the carotenoid profile, furfural and 5-hydroxymethylfurfural, experienced no significantly different impact from the three pasteurization techniques.

Industrial relevance

HP and PEF processing have received important attention during the last years for application as alternatives to traditional thermal pasteurization. For the further implementation of HP and PEF treatment in the food industry, legal approval of such processes is required. Accordingly, an in-depth characterization of products treated by these novel technologies is indispensable. This paper addresses orange juice as a relevant model food product to compare the impact of HP and PEF processing with that of a conventional thermal pasteurization process and to search for significant differences in specific known nutrients, undesired substances and other quality-related aspects of orange juice.     

Effect of high hydrostatic pressure on immunomodulatory activity of cloudy apple juice

Present study investigated the effects of high hydrostatic pressure treatment (HHP, 500 MPa/3 min/ 25°C) on bioactive compound as well as antioxidant, immunomodulatory potentials, and microbial safety of cloudy juice from ‘Fuji’ apples. HHP did not cause any significant changes in vitamin C content whereas total polyphenol content was increased. The antioxidant potentials measured by DPPH and nitric oxide (NO) radical scavenging tests were preserved by HHP, while thermal treatment reduced antioxidant potentials. NO scavenging activity was greater than DPPH scavenging activity. The immunomodulatory effect assessed by splenocyte proliferation was increased in a dose-dependent manner, and HHP preserved immunomodulatory activity of apple juice. Furthermore, HHP treated juice was microbiologically safe without any physicochemical changes during 21 days of storage at 4°C. These results demonstrated the efficacy of HHP for preserving both nutritional and immunomodulatory functional characteristics of apple juice, and alternative method for preserving as freshly squeezed for up to 21 days.     

高压脉冲电场在苹果汁加工中的应用研究进展

在分析高压脉冲电场技术(PEF)对苹果微形态特征的影响及杀菌钝酶效果的基础上,重点综述了PEF技术对苹果汁品质的影响所取得的最新进展及存在的问题,并对今后的研究方向进行了展望,为PEF技术更好地应用于苹果汁的加工提供研究依据。     

Impact of temperature on lethality and energy efficiency of apple juice pasteurization by pulsed electric fields treatment

The applicability of pulsed electric fields as a non-thermal preservation process for liquid food decontamination has been shown in several studies. However, high costs of operation due to the occurrence of a high amount of dissipated electrical energy inhibited an industrial exploitation so far. In this study the focus was put on improving energy efficiency of this process for pasteurization of apple juice inoculated with Escherichia coli by investigating the relation between achieved reduction in survivor count and electric field strength and treatment temperature. An empirical mathematical model was derived to predict the required input of electrical energy for a given inactivation. Using synergistic effects of elevated treatment temperature of 35–65 °C on microbial inactivation the energy consumption could be reduced from above 100 to less than 40 kJ kg⁻¹ for a reduction of 6 log cycles and the need to preheat the juice before treatment provided a possibility to recover the dissipated electrical energy after treatment, leading to a drastic reduction in operation costs. To evaluate the thermal load of the product the pasteurization unit (PU) and the cook value, key benchmarks for the thermal load, were used to compare PEF and conventional heat treatment.     

Identification of equivalent processing conditions for pasteurization of strawberry juice by high pressure,ultrasound, and pulsed electric fields processing

The objective of this study was to evaluate the effectiveness of high pressure processing (HPP), ultrasound (US) and pulsed electric fields (PEF) for the pasteurization of strawberry juice (SJ). Acid-adapted Escherichia coli was used to inoculate SJ prior to treatment with HPP, US, and PEF. HPP was applied at several pressures (200–400 MPa) up to 2 min while US (120 μm, 24 kHz) was conducted at 25, 40, and 55 °C up to 10 min in continuous pulsing mode. In order to avoid excessive use of SJ, PEF was performed using a model solution (MS) basically composed of citric acid (8 g/L), fructose (35 g/L), glucose (35 g/L), Na₂HPO₄ (0.2 M) and NaCl (5%) to simulate the SJ electrical conductivity, pH, and total soluble solid (TSS). A face-centered composite design was conducted for PEF processing at different electric field intensities (EFI) (25–35 kV/cm) and treatment times (5–27 μs). Processing conditions were selected that resulted in 5-log CFU/mL inactivation of E. coli. HPP at 300 MPa for 1 min, and US at 55 °C (thermosonication) for 3 min reduced E. coli in SJ by 5.75 ± 0.52 and 5.69 ± 0.61 log CFU/mL, respectively. PEF treatment at 35 kV/cm, 27 μs treatment time, 350 mL/min flow rate, and 2 μs pulse width in monopolar mode resulted in 5.53 ± 0.00 log reduction of E. coli in MS. Likewise, E. coli population in SJ was also reduced by 5.16 ± 0.15 log after applying the same PEF conditions to SJ. No E. coli was detected in SJ subjected to conventional thermal pasteurization at 72 °C for 15 s. All technologies reduced the natural microbiota below 2 log CFU/mL in terms of the total aerobic bacteria and yeast-mold counts. Thus, this study identified the equivalent conditions for the SJ pasteurization by three nonthermal processing technologies.Industrial relevanceConsumers have an increasing interest towards fresh-like food products with desirable nutritional and sensorial attributes. High pressure, ultrasound and pulsed electric field are three relevant novel nonthermal technologies as alternatives to conventional thermal treatments. This study identified the processing conditions of these three nonthermal technologies for the pasteurization of strawberry juice based on equivalent inactivation of acid-adapted E. coli. From an industrial point of view, the established processing conditions are useful references for the development of novel berry juices. In addition to microbiological safety, this study on equivalent processing allows direct efficacy and quality comparisons of a given juice pasteurized by the three nonthermal technologies under consideration.     

高压脉冲电场和热处理对蓝莓汁品质的影响

以蓝莓汁为原料,比较了高压脉冲电场(PEF)杀菌和热力杀菌处理对蓝莓汁中微生物和理化指标的影响,以及不同处理的蓝莓汁在贮藏期间的品质变化规律。结果表明:PEF可以有效杀灭蓝莓汁中的微生物;PEF杀菌对蓝莓汁色泽参数影响程度小;杀菌处理后,贮藏期内PEF处理和热处理对蓝莓汁的还原糖、总酸、可溶性固形物含量、总酚含量影响较小,PEF处理较热处理能更好地保持蓝莓汁中的VC和花青素含量。      

Safety and quality assessment during the ozonation of cloudy apple juice

Traditionally, ozone processing within the food industry has focused on solid foods by either gaseous treatment or washing with ozonized water. However, with the FDA's approval of ozone as a direct additive to food, the potential for liquid applications has emerged. This study investigates the effect of ozone processing on microbial inactivation (E. coli ATCC 25922 and NCTC 12900) and quality parameters (color, phenolic content) of cloudy apple juice. Apple juice samples were ozonated at room temperature (20 ± 1.5 °C) with a generated ozone concentration of 0.048 mg O(3) at a constant flow rate of 0.12 L/min and treatment time of 0 to 10 min. E. coli inactivation kinetics in apple juice were described quantitatively by using the Shoulder log-linear and the Weibull model. Ozone treatment of E. coli in apple juice demonstrate that a desired 5 log reduction can be achieved within 5 min. Apple juice color (L*, a*, and b*) and total phenols were significantly affected by ozone concentration and treatment time.     

Inactivation of E. coli K12 in apple juice by high voltage pulsed electric field

Pulsed Electric Field (PEF) technology is an emerging non-thermal food preservation technique that has mainly been applied to improve the shelf life of such foods as bread, milk, orange juice, apple juice and liquid eggs. It involves the application of pulses of high voltage to liquid or semi-solid materials, placed between two electrodes at ambient, sub-ambient, or slightly above ambient temperature. The voltage is typically in the range 20–80 kV/cm, and may be applied in the form of exponentially decaying, square wave, oscillatory, or in some cases, bipolar (instant-charge-reversal) pulses. In the present work, the effect number of pulses on the inactivation of E. coli K12 in apple juice was studied at two different voltages, namely 20 and 40 kV/cm and the number of pulses was varied from 0 to 100. The results indicate that the regulatory requirement of 5-log reduction in microbial count for food safety purposes could only be achieved with 40 kV/cm applied voltage and 100 pulses. The experiments were carried out at 20 °C and the maximum temperature rise was 2 °C.     

Reduction of diazinon and dimethoate in apple juice by pulsed electric field treatment

BACKGROUND: Organophosphorus pesticides (OPPs) are widely used in agricultural production in China, and residues of OPPs in agro‐products and foods have become a public health concern. Chronic exposure to OPPs can result in potential immunosuppressive effects, cytotoxicity and mutagenicity. Pulsed electric fields (PEFs) have the potential to be used as an alternative to conventional techniques of food production. The aim of the present study was to investigate the influence of PEFs on the degradation of diazinon and dimethoate added to apple juice. RESULTS: PEF treatment significantly promoted the degradation of both pesticides (P < 0.05). The extent of degradation was strongly influenced by the electric field strength and treatment time, and maximum degradation of both diazinon (47.6%) and dimethoate (34.7%) was achieved by treatment at 20 kV cm^?1 for 260 µs. The degradation behaviour of the pesticides was described by Weibull and Hülsheger models, both of which successfully fitted the degradation of diazinon and dimethoate. In addition, the decline in the toxicity of samples was observed with a photobacterium bioassay. CONCLUSION: PEF treatment was effective in eliminating residues of diazinon and dimethoate spiked in apple juice and in mitigating sample toxicity. Copyright © 2011 Society of Chemical Industry     

均质工艺对苹果浊汁品质的影响

利用不同均质压力(0、10、20、30和40MPa)、均质次数对苹果浊汁进行均质,研究均质工艺对苹果浊汁的褐变情况、悬浮稳定性的影响,还对果汁中果肉颗粒的大小、果汁粘度这两个影响果汁悬浮稳定性的因素进行了探讨。实验结果表明,在30MPa下均质一次可以得到最理想的苹果浊汁。     

Comparative study on cloudy apple juice qualities from apple slices treated by high pressure carbon dioxide and mild heat

Qualities of cloudy apple juices from apple slices treated by high pressure carbon dioxide (HPCD) and mild heat (MH) were evaluated. Temperatures were from 25 to 65 °C, time 20 min, and pressure 20 MPa. Polyphenol oxidase (PPO) was completely inactivated by HPCD and its minimal residual activity (RA) by MH at 65 °C was 38.6%. RA of pectin methylesterase (PME) with HPCD was significantly lower than MH and its minimum was 18%. L value of cloudy apple juice from HPCD-treated apple slices was significantly greater than that from MH-treated apple slices, however, b value, browning degree (BD) and turbidity were lower. And no differences in a value, total soluble solids, pH and conductivity were observed. After 7-day storage at 4 °C, HPCD caused no BD alteration but a significant turbidity loss. MH increased BD at 55 and 65 °C, and led to turbidity loss from 35 to 65 °C. The turbidity was not well related to RA of PME.Industrial relevanceCloudy apple juice is one of the popular fruit juices, and it requires strict processing treatment conditions to protect its quality, especially to prevent enzymatic browning and cloud loss. HPCD is one promising novel non-thermal technique and is likely to replace or partially substitute thermal processes. This study analyzed the effect of HPCD as a pretreatment means on qualities of cloudy apple juice, including inactivating enzymes which are crucial to quality control. Available data provided in this study will benefit the fruit juice industry.     

Effects of high pressure CO2 treatments on microflora, enzymes and some quality attributes of apple juice

The inactivation of microorganisms and enzymes of cloudy apple juice, and some physico-chemical properties of the juice were investigated after continuous high pressure carbon dioxide (HPCD) at 25 MPa and 43 °C, for 2 min and at 22 MPa and 60 °C for 3, 5 and 10 min, respectively. The coliform bacteria were completely inactivated in all the cases. Total aerobic bacteria was reduced by 3.72 log cycles, pectin methylesterase was reduced by 54.3% and polyphenol oxidase was completely inactivated after 10 min treatment at 22 MPa and 60 °C. The yeasts and molds were completely inactivated and the turbidity increased at 22 MPa and 60 °C regardless of time, while the L and a value reduced, but browning degree did not change. The particle size distributions of the juice changed after HPCD but were regained as treatment time was prolonged. The pH was reduced at 22 MPa and 60 °C for 3 or 5 min.