The Impact of Thermosonication and Pulsed Electric Fields on Staphylococcus aureus Inactivation and Selected Quality Parameters in Orange Juice

Application of Ultrasound Treatments in the Processing and Production of High-Quality and Safe-to-Drink Kiwi Juice

This study explores the potential of thermosonication as an alternative to traditional heat treatments, such as pasteurization, in the processing of fruit juices. Conventional methods often lead to undesirable quality changes in fruit juices, whereas thermosonication offers promising results regarding microbial inactivation and quality preservation. This work focused on the inactivation kinetics of Listeria innocua 2030c, a surrogate for pathogenic L. monocytogenes, in kiwifruit juice using thermosonication at 45 °C, 50 °C, and 55 °C. These treatments were compared with equivalent heat treatments. Quality attributes of the juice were also evaluated to assess process efficiency. Survival data of L. innocua were fitted with the Weibull model, estimating first decimal reduction times (δ) and shape parameters (n). The results reveal temperature and process dependencies on δ, while n remains mostly temperature and treatment independent. Thermosonication outperforms heat treatment, achieving higher L. innocua reductions while retaining quality attributes like pH, soluble solid content, and total phenolics and chlorophylls. Thermosonication at 55 °C stands out, providing a 6.2-log-cycle reduction in just 3 min with superior quality retention. These findings highlight the synergistic effect of temperature and ultrasound, making mild heat processes feasible while enhancing product quality. Thermosonication, particularly at 55 °C, emerges as an effective alternative to traditional thermal treatments for fruit juices, offering improved microbial safety without compromising product quality.

Ultrasonication and thermosonication applied in the processing of jalapeno pepper (Capsicum annuum var. annuum) sauce

Ultrasonication is one of the non-thermal physical methods that can be used on foods and when used in synergy with temperature (thermosonication), this technique proves to be more effective, thus reducing the duration and intensity of heat treatment and the consequent damage to the foods. This work aimed to use the technique of ultrasonication and thermosonication in the processing of jalapeno pepper sauces in comparison with pasteurization. Two types of sauces were produced, one with pre-cooking (a) and the other without cooking (b), and the influence of time and temperature was analyzed by applying ultrasonication and thermosonication. Times of 15 and 30 min and temperatures of 25 and 65 °C were used. Both treatments stood out for their effectiveness when compared to the traditional method (pasteurization 65 °C and 30 min). The results demonstrate that, in general, the sauces are good sources of phenolic compounds (141.83 ± 0.10 mg gallic acid equivalent/100 g), flavonoids (50.40 ± 0.30 mg quercetin equivalent/100 g) and carotenoids (2.39 ± 0.07 mg β-carotene/100 g). The sauces had an increase in carotenoids by about 25% (thermosonicated at 15 and 30 min and pre-cooked) and in antioxidant activity (ferric reducing antioxidant power) with about 12% and 13% (thermosonicated at 30 min with and without cooking, respectively) in relation to control (pasteurization). On comparing thermosonication with ultrasound process total phenolics had improved by around 14% and flavonoids by 55%. At the first time, capsantin, capsaicin, dihydrocapsaicin, and nordihydrocapsaicin were identified by ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS). Finally, as both treatments demonstrate efficiency (thermosonication at 15 and 30 min), the use of 15 min is indicated as feasible by the reduced process time and in preventing the loss of bioactive compounds in the sauces when compared to the pasteurization treatment.

Synergistic effect of ultrasound and antimicrobial solutions of cecropin P1 in the deactivation of Escherichia coli O157:H7 using a cylindrical ultrasonic system

This study investigates the synergistic effect of ultrasonication and antimicrobial action of antimicrobial peptide cecropin P1 on the inactivation of Escherichia coli O157:H7 in a cylindrical ultrasonication system. The inactivation of E. coli at pH 7.4 was performed using: ultrasonication (14, 22, and 47 kHz), cecropin P1 (20 µg/mL), and a combination of both. We found the treatment at 22 kHz, 8W for 15 min of exposure and a combination of ultrasound at higher frequency (47 kHz, 8 W) and cecropin P1 for one minute of exposure were more efficient, reducing the cell density by six orders of magnitude, compared to individual treatments (ultrasound or cecropin P1 only). Dye leakage studies and transmission electron microscopy further validated these results. A continuous flow system was designed to demonstrate synergism of ultrasonication with antimicrobial peptide Cecropin P1 in the inactivation of E. coli; synergism was shown to be more at higher ultrasonication frequencies and power levels. Acoustic cavitation by ultrasonic treatment could drastically improve microbial deactivation by antimicrobial peptides cecropin P1 by increasing their ability for pore formation in cell membranes. A continuous ultrasonication and antimicrobial peptides system can lead to an energy-efficient and economical sterilization system for food safety applications.

Non-thermal emerging processing Technologies: Mitigation of microorganisms and mycotoxins, sensory and nutritional properties maintenance in clean label fruit juices

The increase in the fruit juice consumption and the interest in clean label products boosted the development and evaluation of new processing technologies. The impact of some emerging non-thermal technologies in food safety and sensory properties has been evaluated. The main technologies applied in the studies are ultrasound, high pressure, supercritical carbon dioxide, ultraviolet, pulsed electric field, cold plasma, ozone and pulsed light. Since there is no single technique that presents high potential for all the evaluated requirements (food safety, sensory, nutritional and the feasibility of implementation in the industry), the search for new technologies to overcome the limitations is fundamental. The high pressure seems to be the most promising technology regarding all the aspects mentioned. Some of the outstanding results are 5 log reduction of E. coli, Listeria and Salmonella, 98.2% of polyphenol oxidase inactivation and 96% PME reduction. However its cost can be a limitation for industrial implementation. The combination of pulsed light and ultrasound could overcome this limitation and provide higher quality fruit juices. The combination was able to achieve 5.8-6.4 log cycles reduction of S. Cerevisiae, and pulsed light is able to obtain PME inactivation around 90%, 61.0 % more antioxidants, 38.8% more phenolics and 68.2% more vitamin C comparing to conventional processing, and similar sensory scores after 45 days at 4 °C comparing to fresh fruit juice. This review aims to update the information related to the application of non-thermal technologies in the fruit juice processing through systematic and updated data to assist in industrial implementation strategies.

Effect of Thermosonication on Amino Acids, Phenolic Compounds, Sensory Properties and Microbial Quality in Freshly Squeezed Verjuice

Thermosonication is a process that can be used as an alternative to thermal pasteurization by combining mild temperature and ultrasound treatments. This study evaluated the effects of verjuice on the thermosonication process and its bioactive values modeled with the RSM (response surface method). The bioactive components of verjuice were found to increase with high predictive values. Additionally, the presence and amounts of 20 free amino acids in C-VJ (untreated verjuice), P-VJ (thermally pasteurized verjuice) and TS-VJ (thermosonicated verjuice) samples were investigated. Significant (p < 0.05) differences were detected among C-VJ, P-VJ and TS-VJ samples in all free amino acid values except methionine. Although 17 free amino acids were detected at various concentrations, glycine, taurine and cystine were not found in any samples. Thirteen phenolic filters in C-VJ, P-VJ and TS-VJ samples were also examined in this study. Eight phenolic donors with various abilities were detected in the C-VJ sample, along with nine phenolic acceptors in the P-VJ sample and eleven phenolic contents in the TS-VJ sample. The content of phenolic products in the TS-VJ sample increased by 37.5% compared to the C-VJ techniques and by 22.22% compared to the P-VJ techniques. Thermosonication did not significantly affect color and physiochemical values. Panelists generally appreciated the effects of thermosonication. It is concluded that the thermosonication process is a good alternative to thermal pasteurization. The results of this study provide essential data for future in vivo studies and show that the bioactive values of verjuice can be increased by using the thermosonication process.

Advances in pulsed electric stimuli as a physical method for treating liquid foods

There is a need for alternative technologies that can deliver safe and nutritious foods at lower costs as compared to conventional processes. Pulsed electric field (PEF) technology has been utilised for a plethora of different applications in the life and physical sciences, such as gene/drug delivery in medicine and extraction of bioactive compounds in food science and technology. PEF technology for treating liquid foods involves engineering principles to develop the equipment, and quantitative biochemistry and microbiology techniques to validate the process. There are numerous challenges to address for its application in liquid foods such as the 5-log pathogen reduction target in food safety, maintaining the food quality, and scale up of this physical approach for industrial integration. Here, we present the engineering principles associated with pulsed electric fields, related inactivation models of microorganisms, electroporation and electropermeabilization theory, to increase the quality and safety of liquid foods; including water, milk, beer, wine, fruit juices, cider, and liquid eggs. Ultimately, we discuss the outlook of the field and emphasise research gaps.

Thermosonication Applied to Kiwi Peel: Impact on Nutritional and Microbiological Indicators

The peels of many fruits are rich sources of nutrients, although they are not commonly consumed. If they are properly decontaminated, they can be used as healthy food ingredients reducing food waste. The objective was to apply thermosonication processes to kiwi peel and evaluate the impact on Listeria innocua survival (a non-pathogenic surrogate of L. monocytogenes) and key nutrients and quality indicators: proteins, fibers, minerals (Ca, K, Mg, Na, and P), chlorophylls, and phenolic contents. Kiwi peels were artificially inoculated with L. innocua and thermal and thermosonication treatments were performed at 55 °C and 60 °C for 30 and 15 min maximum, respectively. Bacteria were enumerated through treatment time, and quality indicators were assessed before and at the end of treatments. A Weibull model with a decimal reduction time (D-value) was successfully used in L. innocua survival data fits. Results showed that coupling temperature to ultrasound had a synergistic effect on bacteria inactivation with significant decreases in D-values. Thermosonication at 60 °C was the most effective in terms of protein, fiber, chlorophylls, and phenolics retention. Minerals were not significantly affected by all treatments. Applying thermosonication to kiwi peel was more effective for decontamination than thermal treatments at the same temperature while allowing the retention of healthy compounds.

Equivalent processing for pasteurization of a pineapple juice-coconut milk blend by selected nonthermal technologies

Identifying equivalent processing conditions is critical for the relevant comparison of food quality attributes. This study investigates equivalent processes for at least 5-log reduction of Escherichia coli and Listeria innocua in pineapple juice-coconut milk (PC) blends by high-pressure processing (HPP), pulsed electric fields (PEF), and ultrasound (US) either alone or combined with other preservation factors (pH, nisin, and/or heat). The two blends (pH 4 and 5) and coconut milk (pH 7) as a reference were subjected to HPP at 300-600 MPa, 20°C for 0.5-30 min; PEF at an electric field strength of 10-21 kV/cm, 40°C for 24 µs; and US at 120 µm amplitude, 25 or 45°C for 6 or 10 min. At least a 5-log reduction of E. coli was achieved at pH 4 by HPP at 400 MPa, 20°C for 1 min; PEF at 21 kV/cm, 235 Hz, 40°C for 24 µs; and US at 120 µm, 45°C for 6 min. As L. innocua showed greater resistance, a synergistic lethal effect was provided at pH 4 by HPP with 75 ppm nisin at 600 MPa, 20°C for 5 min; PEF with 50 ppm nisin at 18 kV/cm, 588 Hz, 40°C for 24 µs; and US at 45°C, 120 µm for 10 min. The total soluble solids (11.2-12.4°Bx), acidity (0.47%-0.51% citric acid), pH (3.91-4.16), and viscosity (3.55 × 10^-3 -4.0 × 10^-3  Pa s) were not significantly affected under the identified equivalent conditions. HPP was superior to PEF and US, achieving higher ascorbic acid retention and lower color difference in PC blend compared to the untreated sample.

Combinatorial physical methods for cellular therapy: Towards the future of cellular analysis?

The physical energy activated techniques for cellular delivery and analysis is one of the most rapidly expanding research areas for a variety of biological and biomedical discoveries. These methods, such as electroporation, optoporation, sonoporation, mechanoporation, magnetoporation, etc., have been widely used in delivering different biomolecules into a range of primary and patient-derived cell types. However, the techniques when used individually have had limitations in delivery and co-delivery of diverse biomolecules in various cell types. In recent years, a number of studies have been performed by combining the different membrane disruption techniques, either sequentially or simultaneously, in a single study. The studies, referred to as combinatorial, or hybrid techniques, have demonstrated enhanced transfection, such as efficient macromolecular and gene delivery and co-delivery, at lower delivery parameters and with high cell viability. Such studies can open up new and exciting avenues for understanding the subcellular structure and consequently facilitate the development of novel therapeutic strategies. This review consequently aims at summarising the different developments in hybrid therapeutic techniques. The different methods discussed include mechano-electroporation, electro-sonoporation, magneto-mechanoporation, magnetic nanoparticles enhanced electroporation, and magnetic hyperthermia studies. We discuss the clinical status of the different methods and conclude with a discussion on the future prospects of the combinatorial techniques for cellular therapy and diagnostics.

Effective control of antibiotic resistance using a sonication-based combinational treatment and its application to fresh food

Antibiotics have been widely used to treat several infectious diseases. However, the overuse of antibiotics has promoted the emergence and spread of antibiotic resistant bacteria (ARB) in various fields, including the food industry. In this study, the antimicrobial efficacies of two conventional sterilization methods, mild heat, and sonication, were evaluated and optimized to develop a new strategy against ARB. Simultaneous mild heat and sonication (HS) treatment led to a significant reduction in viable cell counts, achieving a 5.58-log reduction in 4 min. However, no remarkable decrease in viable cell counts was observed in individually treated groups. Interestingly, the release of antibiotic resistance genes (ARGs) increased in a time-dependent manner in the heat-treated and HS-treated groups. The inactivation levels of ARGs increased as the HS treatment time increased from 2 to 8 min, and most ARGs were degraded after 8 min. In contrast, no significant inactivation of ARGs was observed in the heat-treated and sonication-treated groups after 8 min. These results reveal the synergistic effect of the combination treatment in controlling not only ARB but also ARGs. Finally, on applying this newly developed combination treatment to fresh food (cherry tomato and carrot juice), 3.97- and 4.28-log microbial inactivation was achieved, respectively. In addition, combination treatment did not affect food quality during storage for 5 days. Moreover, HS treatment effectively inactivated ARGs in fresh food systems.

Applications of Innovative Non-Thermal Pulsed Electric Field Technology in Developing Safer and Healthier Fruit Juices

The deactivation of degrading and pectinolytic enzymes is crucial in the fruit juice industry. In commercial fruit juice production, a variety of approaches are applied to inactivate degradative enzymes. One of the most extensively utilized traditional procedures for improving the general acceptability of juice is thermal heat treatment. The utilization of a non-thermal pulsed electric field (PEF) as a promising technology for retaining the fresh-like qualities of juice by efficiently inactivating enzymes and bacteria will be discussed in this review. Induced structural alteration provides for energy savings, reduced raw material waste, and the development of new products. PEF alters the α-helix conformation and changes the active site of enzymes. Furthermore, PEF-treated juices restore enzymatic activity during storage due to either partial enzyme inactivation or the presence of PEF-resistant isozymes. The increase in activity sites caused by structural changes causes the enzymes to be hyperactivated. PEF pretreatments or their combination with other nonthermal techniques improve enzyme activation. For endogenous enzyme inactivation, a clean-label hurdle technology based on PEF and mild temperature could be utilized instead of harsh heat treatments. Furthermore, by substituting or combining conventional pasteurization with PEF technology for improved preservation of both fruit and vegetable juices, PEF technology has enormous economic potential. PEF treatment has advantages not only in terms of product quality but also in terms of manufacturing. Extending the shelf life simplifies production planning and broadens the product range significantly. Supermarkets can be served from the warehouse by increasing storage stability. As storage stability improves, set-up and cleaning durations decrease, and flexibility increases, with only minor product adjustments required throughout the manufacturing process.

Ultrasound and heat treatment effects on Staphylococcus aureus cell viability in orange juice

Ultrasounds are being considered an excellent alternative technology in juice preservation. Yet, when combined with heat treatment, the process seems to be further intensified. This work aimed to evaluate and compare the impact of ultrasounds and heat treatments, when applied alone or in combination, on Staphylococcus aureus survival in orange juice. Inoculated commercial pasteurized orange juice was treated at different times at 20, 30, 40, 50 and 60 °C. SEM analyses were applied to identify morphological changes in S. aureus cells appearance. The microbial inactivation data were fitted using two mathematical models, depending on the behaviour observed. Sonication at 20, 30, and 40 °C induced 4.02 ± 0.52, 3.80 ± 0.49 and 4.30 ± 0.74 log cycles reduction of S. aureus after treatments of 90, 60 and 60 min, respectively. The heat treatments at the same temperatures had no impact on S. aureus survival. When 50 and 60 °C were applied, more than 5-log reductions were attained for both thermosonication and heat treatments alone. A synergistic effect was observed between sonication and high temperatures. At 50 °C, the thermosonication reduced the treatment time from 60 to 35 min and the microbial load from 5.14 ± 0.08 to 10.76 ± 0.28 log cycles reduction, compared to heat treatment alone. Results from SEM images showed that cells undergo membrane damage during sonication exposure. This was observed by collapsed cells, cell disruption, and holes in the cell's membrane. Thermosonication proved to be a viable alternative to thermal pasteurization of orange juice since milder treatments can be safely applied, improving the final product quality.

Rapid Pasteurization of Apple Juice Using a New Ultrasonic Reactor

A new ultrasonic reactor was used to rapidly inactivate Escherichia coli and Staphylococcus aureus in apple juice. It was found that high pulp content made ultrasound less lethal to S. aureus, while it had no significant effect on E. coli. When the pulp free apple juice was ultrasonically processed, the 5-log reduction time was 35 s for E. coli at 60 °C and 30 s for S. aureus at 62 °C. Ultrasound treatment had no significant effect on antioxidant activity determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, but it significantly increased the total phenolic content. The treatment also resulted in more stable juice with higher uniformity. During 28 d of storage at 4 °C, the total plate count in apple juice ultrasonically treated at 60 °C for 35 s remained around 1.00 log CFU/mL, whereas it was nearly zero for a stronger ultrasound treatment at 62 °C for 30 s. These values were much lower than those in the untreated one, which increased from 3.65 log CFU/mL to 8.36 log CFU/mL during the storage. At the end of the storage, the control and thermally treated apple juice lost almost 70% of antioxidant activity, whereas the ultrasonically treated juice only lost 20-40%.

Effect of Thermosonication and Physicochemical Properties of Wine on Culturability, Viability, and Metabolic Activity of Brettanomyces bruxellensis Yeast in Red Wines

The aim of this research was to investigate the short- and long-term effects of thermosonication and different physicochemical properties of wine on culturability, viability, and metabolic activity of Brettanomyces bruxellensis yeast. Thermosonication was conducted at 43 °C during 1, 2, and 3 min, while wine variations included several pH, alcohol, and sugar levels. Cell culturability and viability were determined immediately after treatment and during 90 days of storage, while metabolic activity was determined after 90 days of storage. Results showed that, although culturability was not confirmed in dry wines immediately after 3 min of treatment, thermosonication did not result in complete inactivation of the B. bruxellensis population. Herein, the first evidence of a viable but not culturable (VBNC) state of B. bruxellensis after thermosonication exposure was observed. Moreover, thermosonication reduced the production of volatile phenols. Obtained results suggest application of thermosonication for reduction of the B. bruxellensis population only in early stages of wine contamination.

Ascorbic acid stability in fruit juices during thermosonication

Thermosonication is an emerging technology useful for inactivating microorganisms and enzymes in fruit juices. However, the effect of the ultrasound processing on the ascorbic acid content is not clear and the results reported in the literature are contradictory. In this work, the impact of sonication and thermosonication on the ascorbic acid content was first evaluated in model systems. Degassed model solutions at four different pH values (3-6) were processed with or without sonication for 60min at two different conditions of temperature (25 and 55°C). In all cases, the ascorbic acid was stable under the treatment. After that, two commercial deaerated fruit juices were processed with and without US at 55°C. The ascorbic acid was also retained in these juices after the ultrasound processing under the most severe conditions studied. In conclusion, previous degassing/deaerating of fruit juices is recommended to prevent ascorbic acid degradation when thermosonication is applied.

Quality-related enzymes in plant-based products: effects of novel food-processing technologies part 3: ultrasonic processing

High-power ultrasound is a versatile technology which can potentially be used in many food processing applications including food preservation. This is part 2 of a series of review articles dealing with the effectiveness of nonthermal food processing technologies in food preservation focusing on their effect on enzymes. Typically, ultrasound treatment alone does not efficiently cause microbial or enzyme inactivation sufficient for food preservation. However, combined with mild heat with or without elevated pressure (P ≤ 500 kPa), ultrasound can effectively inactivate enzymes and microorganisms. Synergistic effects between ultrasound and mild heat have been reported for the inactivation of both enzymes and microorganisms. The application of ultrasound has been shown to enhance the rate of inactivation of quality degrading enzymes including pectin methylesterase (PME), polygalacturonase (PG), peroxidase (POD), polyphenol oxidase (PPO), and lipoxygenase (LOX) at mild temperature by up to 400 times. Moreover, ultrasound enables the inactivation of relatively heat-resistant enzymes such as tomato PG1 and thermostable orange PME at mild temperature conditions. The extent to which ultrasound enhances the inactivation rate depends on the type of enzyme, the medium in which the enzyme is suspended, and the processing condition including frequency, ultrasonic intensity, temperature, and pressure. The physical and chemical effects of cavitation are considered to be responsible for the ultrasound-induced inactivation of enzymes, although the dominant mechanism depends on the structure of the enzyme.

Inactivation of Escherichia coli O157:H7 on Orange Fruit Surfaces and in Juice Using Photocatalysis and High Hydrostatic Pressure

Nonpasteurized orange juice is manufactured by squeezing juice from fruit without peel removal. Fruit surfaces may carry pathogenic microorganisms that can contaminate squeezed juice. Titanium dioxide-UVC photocatalysis (TUVP), a nonthermal technique capable of microbial inactivation via generation of hydroxyl radicals, was used to decontaminate orange surfaces. Levels of spot-inoculated Escherichia coli O157:H7 (initial level of 7.0 log CFU/cm(2)) on oranges (12 cm(2)) were reduced by 4.3 log CFU/ml when treated with TUVP (17.2 mW/cm(2)). Reductions of 1.5, 3.9, and 3.6 log CFU/ml were achieved using tap water, chlorine (200 ppm), and UVC alone (23.7 mW/cm(2)), respectively. E. coli O157:H7 in juice from TUVP (17.2 mW/cm(2))-treated oranges was reduced by 1.7 log CFU/ml. After orange juice was treated with high hydrostatic pressure (HHP) at 400 MPa for 1 min without any prior fruit surface disinfection, the level of E. coli O157:H7 was reduced by 2.4 log CFU/ml. However, the E. coli O157:H7 level in juice was reduced by 4.7 log CFU/ml (to lower than the detection limit) when TUVP treatment of oranges was followed by HHP treatment of juice, indicating a synergistic inactivation effect. The inactivation kinetics of E. coli O157:H7 on orange surfaces followed a biphasic model. HHP treatment did not affect the pH, °Brix, or color of juice. However, the ascorbic acid concentration and pectinmethylesterase activity were reduced by 35.1 and 34.7%, respectively.

Effect of heat-assisted pulsed electric fields and bacteriophage on enterohemorrhagic Escherichia coli O157:H7

Pulsed electric fields (PEF), heat-assisted PEF (H-PEF), and virulent bacteriophage (VP) are non-thermal techniques for pathogen inactivation in liquids that were investigated individually, and in combination (PEF/VP, H-PEF/VP) to control enterohemorrhagic Escherichia coli (EHEC) O157:H7 in Luria-Bertani broth (LBB) and Ringer's solution (RS). Treated cells were subsequently incubated at refrigeration (4°C) and temperature-abuse conditions (12°C) for 5 days. When EHEC cells grown in LBB were subjected to non-thermal processing and subsequently stored at 12°C for 5 days, reductions in count of between 0.1 and 0.6 log cycles were observed and following storage at 4°C the decrease in counts varied between 0.2 and 1.1 log10 . For bacteria cells suspended in RS values ranged from 0.1 to ≥3.9 log cycles at both storage temperatures. The most effective treatments were H-PEF and H-PEF/VP, both producing a >3.4 log cycle reduction of cells suspended in non-nutrient RS. Analysis of EHEC recovery on selective and non-selective media indicated no occurrence of sub-lethal damage for VP, PEF/VP, and H-PEF/VP-treated cells. The findings indicate that combining PEF and lytic phage may represent a suitable alternative to conventional fluid decontamination following further process optimization.

Change in Color and Volatile Composition of Skim Milk Processed with Pulsed Electric Field and Microfiltration Treatments or Heat Pasteurization

Non-thermal processing methods, such as pulsed electric field (PEF) and tangential-flow microfiltration (TFMF), are emerging processing technologies that can minimize the deleterious effects of high temperature short time (HTST) pasteurization on quality attributes of skim milk. The present study investigates the impact of PEF and TFMF, alone or in combination, on color and volatile compounds in skim milk. PEF was applied at 28 or 40 kV/cm for 1122 to 2805 µs, while microfiltration (MF) was conducted using membranes with three pore sizes (lab-scale 0.65 and 1.2 µm TFMF, and pilot-scale 1.4 µm MF). HTST control treatments were applied at 75 or 95 °C for 20 and 45 s, respectively. Noticeable color changes were observed with the 0.65 µm TFMF treatment. No significant color changes were observed in PEF-treated, 1.2 µm TFMF-treated, HTST-treated, and 1.4 µm MF-treated skim milk (p ≥ 0.05) but the total color difference indicated better color retention with non-thermal preservation. The latter did not affect raw skim milk volatiles significantly after single or combined processing (p ≥ 0.05), but HTST caused considerable changes in their composition, including ketones, free fatty acids, hydrocarbons, and sulfur compounds (p < 0.05). The findings indicate that for the particular thermal and non-thermal treatments selected for this study, better retention of skim milk color and flavor components were obtained for the non-thermal treatments.

Effects of ultrasound treatments on quality of grapefruit juice

Sonication is recognised as a potential technique for improvement in the quality of fruit juices. This study was initiated with the objective of evaluating the effect of sonication treatments on some important quality parameters of grapefruit juice such as physico-chemical (pH, acidity and °Brix), Hunter colour values (L(*), a(*) and b(*)), cloud value, electrical conductivity, total antioxidant capacity, DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity, ascorbic acid, total phenolics, flavonoids and flavonols. Sonication of grapefruit juice was done in a bath type sonicator at a frequency of 28 kHz by maintaining a constant temperature of 20 °C. Results showed that there was significant improvement in the cloud value, total antioxidant capacity, DPPH free radical scavenging activity, ascorbic acid, total phenolics, flavonoids and flavonols in all the juice samples sonicated for 30, 60 and 90 min but no changes occurred in the pH, acidity and °Brix value as compared to control. Some differences in all the colour values were also observed but overall quality of grapefruit juice was improved, suggesting that sonication technique may successfully be implemented an industrial scale for the processing of grapefruit juice.

Effect of thermal and non-thermal pasteurisation on the microbial inactivation and phenolic degradation in fruit juice: a mini-review

Fruit juice has been traditionally preserved by thermal pasteurisation. However, the applied heat can cause detrimental effects on health-promoting components such as phenolic compounds. Several non-thermal technologies such as membrane filtration, pulsed electric field (PEF) and ultraviolet (UV) exposure are promising methods developed for liquid food preservation. In particular, the combination of UV and PEF has proven to be more effective for microbial inactivation and maintaining nutritional quality of fruit juice compared with individual applications.