Effects of combining ultraviolet and mild heat treatments on enzymatic activities and total phenolic contents in pineapple juice

Ultraviolet (UV) is able to inactivate most microorganisms in fruit juices with a low absorption coefficient but its effect is limited in inactivating undesired enzymes. The aim of this study was to overcome limitation of ultraviolet light (UV) by combining mild heat with UV. Pineapple juice was treated with mild heat (temperature: 50, 55 and 60 °C; holding time: 10, 20 and 30 min) and subsequently exposed to UV (5.61, 7.55 and 11.23 mJ·cm^− 2). The effects of these combined treatments on pectin methylesterase (PME), bromelain activities and total phenolic content (TPC) were determined. Both enzymatic activities were reduced by mild heat but not by UV treatment. Increasing holding time and UV dosage led to higher depletion of TPC. Treating pineapple juice with mild heat at 55 °C for 10 min and UV at 5.61 mJ·cm^− 2 decreased PME by 60.53% whilst retaining 61.57 ± 0.21% and 72.80 ± 0.33% of bromelain and TPC, respectively.Industrial relevanceAs opposed to traditional heat pasteurisation, ultraviolet (UV) treatment has the potential to produce pineapple juice with added value, such as high amount of health benefiting phenols and bromelain. Despite being known for being economically feasible, this technology is not widely adapted by the industry due to its inability to inactivate pectin methylesterase (PME). To overcome the limitation of UV, mild heat (MH) is introduced as hurdle technology. This study demonstrates that combining UV and MH could be able to effectively inactivate the PME in pineapple juice whilst preserving relatively high amount of bromelain and phenols.     

Antioxidant capacity,phenolic composition and microbial stability of aronia juice subjected to high hydrostatic pressure processing

The aim of this study was to characterize the effect of high hydrostatic pressure (200–600 MPa/15 min) and storage (4 °C/80 days) on aronia juice quality. The total antioxidant capacity, phenolic content and composition were assessed using an updated analytical strategy. Microbial growth was also analyzed following juice storage. Among all the analyzed juices, the untreated aronia juice had the greatest reduction (36%) in total polyphenols over the entire storage period. At the end of the storage period, the pressurized juices demonstrated ABTS and FRAP values higher by 14% and 5% as compared to the untreated juices. The main antioxidants identified in the aronia juice were: chlorogenic acid; neochlorogenic acid; cyanidin 3-galactoside; cyanidin 3-xyloside; cyanidin 3-arabinoside; cyanidin 3-glucoside. Cyanidin 3-glucoside was the most stable compound during juice storage. Microorganism growth in juices pressurized at 400–600 MPa was below the detection limit (< 1 CFU mL^− 1) upon storage.Industrial relevanceAronia berries are rarely consumed fresh since they give off several negative sensory attributes. Multiple health-promoting properties of aronia berries make them a valuable raw material for juice production. However, processing involves pasteurization or hot-filling strongly diminishes the product quality due to the changes in quantity and quality of thermolabile phytochemicals. The objective of this work was to characterize the effect of high hydrostatic pressure on the antioxidant capacity, polyphenol content and composition and microbial stability of aronia juice. Results of this study may be useful for the juice industry commercialize this technology for the development healthy, nonclarified aronia juices with desired level of quality.     

Apple,grape or orange juice: Which one offers the best substrate for lactobacilli growth? — A screening study on bacteria viability,superoxide dismutase activity,folates production and hedonic characteristics

Fermentation can contribute to improve functional aspects of foods. The first goal of this study was to determine amongst apple, grape and orange juices, the one with the best bacterial growth performance during fermentation by Lactobacillus strains from commercial and artisanal food origins, at 40 °C for 48 h. The juice with the highest bacterial growth was evaluated for bacteria viability during 4 weeks of cold storage, superoxide dismutase (SOD) activity and folates production analyzed through HPLC/fluorimetry. Acceptability of fermented juice was appraised through hedonic analysis. Lactobacilli counts were the highest in apple and the lowest in orange juices at t = 48 h. In most cases, bacteria counts were higher in fermented (5.5 to 9.5 log CFU/ml) than in supplemented apple juices (4.2 to 5.7 log CFU/ml), at the 4th week of cold storage. SOD activity was significantly increased in all apple juices fermented by commercial Lactobacilli strains. Folates were produced in apple juices fermented by Lactobacillus plantarum and Lactobacillus rhamnosus. Apple juice was the best substrate for Lactobacillus growth and, considering bacterial viability and overall acceptance by the panelists, Lactobacillus acidophilus L10 was the most suitable strain for apple juice fermentation.     

Processing of clear and turbid grape juice by a continuous flow UV system

The inactivation of inoculated (S. cerevisiae) and spoilage microorganisms, i.e. yeasts and lactic acid bacteria (LAB), in clear and turbid grape juice was investigated using a pilot scale UV system. The biodosimetry method was used for UV dose prediction in a continuous flow UV reactor. Weibull model was applied for fitting the inactivation data. The flow rates (774, 820 ml/min) in this system were very close to the ones used in fruit juice processing. S. cerevisiae in clear juice was reduced by 3.39 ± 0.04 at 65.50 mJ/cm² of UV dose. 1.54 ± 0.04 and 1.64 ± 0.03 log CFU/ml reductions were obtained for spoilage yeasts and LAB in turbid juice at UV dose of 78.56 and 67.97 mJ/cm², respectively. The soluble solids (°Brix) and pH of grape juice samples were not affected by UV-C treatment (p > 0.05). Although the color parameters slightly were changed after irradiation, the color of PCGJ and FSTGJ did not show visual difference compared to the untreated samples.Industrial relevanceUV light has a potential to reduce the levels of microbial contamination in liquid foods. Although grape juice has many beneficial health effects, it has a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics have markedly expanded in recent years. In the current study, the microbial inactivation efficiency of a pilot scale UV system for non-thermal treatment of clear and turbid grape juice was evaluated under conservative conditions. Most of the physicochemical properties of grape juice samples were not significantly affected from UV-C treatment (p > 0.05). This would be a major advantage in the processing of nutritious juice products.     

“Ice” juice from apples obtained by pressing at subzero temperatures of apples pretreated by pulsed electric fields

The impact of apple pretreatment by pulsed electric field (PEF) on juice extraction using the freezing-assisted pressing was studied. Apple discs were PEF pretreated at electric field strength of E = 800 V/cm and then air blast frozen inside the freezer (− 40 °C). Then, pressing experiments in a laboratory-pressing chamber (2–5 bars) were started at sub-zero temperature (− 5 °C). Time evolution of juice yield and its nutritional qualities were compared for PEF and untreated apple samples. High improvements of juice yield were obtained for freeze-thawed (FT) and PEF + FT samples. The combination of PEF + pressing (5 bar) at sub-zero temperature gave optimum results for juice extraction with high levels of carbohydrates, and antioxidant bioactive compounds. At fixed value of extraction yield, Y, PEF pretreatment improved nutritional parameters. E.g., at Y = 0.6, an increase in °Brix (by ≈ 1.27), carbohydrates (by ≈ 1.42), total phenolic compounds (by ≈ 1.16), flavonoids (by ≈ 1.09) and antioxidant capacity (by ≈ 1.29) was observed after PEF pretreatment.Industrial relevancePressing constitutes one of the most commonly used technologies at industrial scale to obtain fruit juices. However, during the pressing some undesirable chemical, physical and biological changes may occur in juices, thus reducing their nutritional and sensorial properties. For instance, the use of freezing-assisted pressing is a promising technique for the production of juice concentrates rich in sugars and other solids as the low temperature operation prevents undesirable modifications. But this method is rather expensive and requires strong control of the quality of “ice” juices, their sensory and compositional profiles. Thus, there is an increased search for obtaining new efficient methodologies for producing high quality juices. In this line, PEF-assisted pressing has been shown as a useful technology to increase juice yield. Therefore, the combination of PEF-assisted “ice” juice extraction by pressing of fruits at subzero temperatures may be a useful tool to improve the extraction yield of juices, thus improving their nutritional, physicochemical and sensorial properties.Keywords: “Ice” juice, Apple, Pulsed electric fields, Freezing-assisted pressing     

Combined densification and pulsed electric field treatment for selective polyphenols recovery from fermented grape pomace

The aim of this study is to assess a new process for the valorization of fermented grape pomace using pulsed electric fields (PEF). The combination of densification and PEF treatment was applied on grape pomace of low relative humidity, without any addition of conductive liquid. The kinetics of extraction and the composition of polyphenols were evaluated throughout the subsequent hydro-alcoholic extraction at different temperatures.Optimal parameters of PEF treatment (field strength E = 1.2 kV·cm^− 1; energy input W = 18 kJ·kg^− 1; density ρ = 1.0 g·cm^− 3) increased the content of total polyphenols regardless of the temperature of extraction. The ratio of total anthocyanins to total flavan-3-ols at 20 °C was equal to 7.1 and 9.0 for control and PEF treated modalities, respectively. These results demonstrate the selective nature of PEF treatment in anthocyanin extraction, and thus reveal new possibilities to produce extracts with different biochemical compositions.Industrial relevanceThis study examines the feasibility of densification combined with PEF pre-treatment of relatively low humidity grape pomace for the enhancement of bioactive compounds extraction. The concentration of total phenolic compounds obtained after PEF treatment showed that the use of this technique is relevant for an industrial use, since solvent amount and extraction time can be reduced. Moreover, the selective nature of PEF opens the opportunity to produce extracts of different biochemical compositions. This process is an alternative to conventional pre-treatments of raw material (e.g. dehydration and grinding), which have impacts on product quality and are more energy consuming.     

Inactivation kinetics of Listeria monocytogenes,Salmonella enterica serovar Typhimurium,and Campylobacter jejuni in ready-to-eat sliced ham using UV-C irradiation

To investigate the applicability of UV-C irradiation on the inactivation of foodborne pathogenic bacteria in ready-to-eat sliced ham, UV-C treatment was evaluated. Irradiation dose required for 90% reduction of the populations of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Campylobacter jejuni were determined to be 2.48, 2.39, and 2.18 J/m². Ready-to-eat sliced hams were inoculated with the pathogens and irradiated with UV-C light of 1000, 2000, 4000, 6000, and 8000 J/m². Microbiological data indicated that foodborne pathogen populations significantly (p < 0.05) decreased with increasing UV-C irradiation. In particular, UV-C irradiation at 8000 J/m² reduced the populations of L. monocytogenes, S. Typhimurium, and C. jejuni in the ham by 2.74, 2.02, and 1.72 log CFU/g. The results indicate that UV-C irradiation can be used as a microbial inactivation method for ready-to-eat sliced ham, and inactivation kinetics of the foodborne pathogens fit the Weibull model better than the first-order kinetics model.     

Dynamics of the loss and emergence of volatile compounds during the concentration of cashew apple juice (Anacardium occidentale L.) and the impact on juice sensory quality

Concentrating cashew apple juice alters the beverage aroma and flavor, compromising consumer acceptability of the concentrated beverage. To understand the mechanisms involved in these changes, this research characterized the dynamics of the loss and emergence of volatile compounds during cashew apple juice concentration, reporting their impact on beverage sensory quality. Fresh cashew apple juice (10.3°Brix) was concentrated in a thermal-siphon type evaporator operating in a closed system. Five samples were taken throughout the concentration process with the following soluble solids contents: 11.8°Brix, 14.9°Brix, 20.2°Brix, 29.6°Brix and 42.1°Brix. Trained judges rated the aroma note intensities, described as “fresh cashew apple” and “cooked” as perceived in the fresh and concentrated beverages. The headspace volatiles of the six samples were identified and quantified by GC–MS. The results indicated the esters as the major component in the fresh juice (226.46 μg kg^− 1) representing 45.0% of the total mass of volatiles, followed by the terpenes (118.98 μg kg^− 1), acids (45.23 μg kg^− 1), aldehydes (39.10 μg kg^− 1), alcohols (18.91 μg kg^− 1), lactones (19.15 μg kg^− 1), hydrocarbons (18.02 μg kg^− 1) and ketones (11.05 μg kg^− 1). Predictive statistical models (R² > 0.956, p ≤ 0.002) revealed that on reaching 14.9°Brix, the ester concentration declined more than 90%, the terpene content almost 100%, alcohols 85%, aldehydes 80% and hydrocarbons 90%. At 14.9°Brix, the intensity of “fresh cashew apple” aroma still predominated in the juice, but the panelists detected the presence of a weak “cooked” aroma. Concentration of the beverage to 20.2°Brix or above expressively increased the cooked aroma intensity and the concentration of hydrocarbons, alcohols and some aldehydes usually associated with off-flavors such as pentanal and decanal. This raises the possibility that some of these compounds might have been formed during juice processing. Juice with better sensory quality could possibly be obtained by concentrating the beverage to levels below 20.2°Brix, recovering the esters that evaporated off the juice until ~ 15°Brix is reached, and re-adding them to the juice concentrated.     

Minimal processing of mucilage from the pulp of yam (Dioscorea pseudojaponica Yamamoto) using bubble separation and ultraviolet irradiation

Recently the applications of the low starch contents of yam mucilage in nutraceutical and cosmeceutical industries are required. A novel continuous pilot-scale bubble separation system was used for recovering yam slurry mucilage. The objectives of these studies were to follow the previous design for continuously separating, recovering and irradiating yam slurry mucilage for inactivation of microorganisms. The UV-C dose of 32000 μW/sec/cm² at 254 nm has a germicidal effect against microorganisms and is used for the disinfection. Two sets of custom made UV-C irradiators containing four UV-C germicidal lamps were added to the system. The effectiveness of this UV-C irradiator for reducing the aerobic bacteria count (APC) and yeasts and molds (YM) count in yam slurry mucilage was investigated. The results showed UV-C irradiation was successfully applied to reduce the microbial load in the yam slurry mucilage. If the slurry mucilage completes the process for both two sets of UV-C irradiators, a 4.5 log₁₀ APC reduction and a 4.1 log₁₀ YM reduction were achieved after 200 sec irradiation at a UV-C dosage of 32000 μW/sec/cm², resulting in zero cfu/ml APC and YM. Escherichia coli and Salmonella are both negative. This novel continuous UV-C pilot-scale bubble separation technology could be an alternative technology not only separate and recover mucilage but also reduce the microorganisms to acceptable levels.Industrial relevanceThis novel continuous pilot-scale bubble separation system was used for recovering yam slurry mucilage. Recently the applications of the low starch contents of yam mucilage in nutraceutical and cosmeceutical industries are required.This novel continuous UV-C pilot-scale bubble separation technology could be an alternative technology not only to separate and recover mucilage but also reduce the microorganisms to acceptable levels. Actually the pilot scale of this system is going to build in our university. We also try to further use it for non-thermal fermentation. There are many potential industrial applications using this idea.     

Determination of polyphenols in apple juice and cider by capillary electrophoresis with electrochemical detection

A simultaneous determination of phloridzin, (−)-epicatechin, chlorogenic acid and myricetin in apple juices and ciders by capillary electrophoresis with electrochemical detection (CE-ED) was reported. Effects of several important factors such as the pH and concentration of running buffer, separation voltage, injection time and detection potential were investigated to acquire the optimum conditions. Under the optimum conditions, the analytes could be separated within 20 min in a 75 cm length capillary at a separation voltage of 18 kV in a 50 mmol/l borate buffer (pH 8.7). A 300 μm diameter carbon disk electrode generates good response at +0.90 V (vs. SCE) for all analytes. The relationship between peak currents and analyte concentrations was linear over about three orders of magnitude with detection limits (S/N = 3) ranging from 1 × 10⁻⁷ to 5 × 10⁻⁷ g/ml for all analytes. This proposed method demonstrated long-term stability and reproducibility with relative standard deviations of less than 4% for both migration time and peak current (n = 7). It has been successively used for the determination of the analytes in apple juices and ciders, and the assay result was satisfactory.     

Reactions of polyphenols in masticated apple fruit with nitrite under stomach simulating conditions: Formation of nitroso compounds and thiocyanate conjugates

By the ingestion of fresh apple fruit, it is masticated squeezing apple juice into the oral cavity and the juice is mixed with saliva. The mixture of saliva and apple juice is swallowed into the stomach where the pH is around 2. This paper deals with the reactions of polyphenols in the juice obtained by mastication of apple fruit with salivary nitrite under acidic conditions. The concentrations of catechins, procyanidins, and chlorogenic acid in the apple juice were approximately 55, 55, and 170 μM, respectively, and the polyphenols were oxidized by salivary nitrite under conditions of the stomach. Rates of the oxidation increased in order chlorogenic acid < catechins < procyanidins. The oxidation of catechins and procyanidins resulted in the formation of the nitroso compounds, and the oxidation of chlorogenic acid resulted in the formation of the thiocyanate conjugate. The production of dinitroso compounds is proposed to be due to the addition of nitric oxide (NO) to radicals of catechins and procyanidins. As the mechanism of thiocyanate conjugate formation, reaction of o-quinone of chlorogenic acid with a salivary component thiocyanate is proposed, and the formation of the thiocyanate conjugate is discussed from the point of detoxification of chlorogenic acid quinone.     

Flavanone glycosides in Brazilian orange juice

Authentic samples of oranges, frozen concentrated orange juice and pulp-wash, and retail samples of freshly squeezed orange juice and frozen concentrated orange juice have been collected in Brazil and analysed for the flavanone glycosides (FG) narirutin and hesperidin by reversed phase HPLC with UV detection at 280 nm. The juice from hand-squeezed fruit gave narirutin and hesperidin concentrations of 16–142 mg l⁻¹ and 104–537 mg l⁻¹, respectively. The ratio of hesperidin to narirutin showed varietal difference with Pera having the highest ratio (mean 8.4) and Baı́a the lowest (3.6). Frozen concentrated orange juice contained higher quantities of FG with narirutin ranging from 62 to 84 mg l⁻¹ and hesperidin from 531 to 690 mg l⁻¹ (after dilution to 12 °Brix). In frozen concentrated orange juice pulp-wash, the narirutin level ranged from 155 to 239 mg l⁻¹ and hesperidin from 1089 to 1200 mg l⁻¹. The analysis of 23 samples of freshly squeezed juice from the Brazilian market place showed that the FG content of most samples (9.1 to 94.8 and 105.8 to 586.6 mg l⁻¹, respectively, for narirutin and hesperidin) was similar to those found for authentic ones, indicating that these orange juices were not adulterated.     

Comparison of the effect of pulsed electric field or high voltage electrical discharge for the control of sweet white must fermentation process with the conventional addition of sulfur dioxide

The present work discusses the efficiency of pulsed electrical treatments for the inactivation of yeasts. The application of pulsed electric fields (PEFs) and high voltage electrical discharges (HVEDs) as alternatives to sulfites, which are used as anti-microbial to stop the fermentation of sweet white wine, was investigated. The influence of sulfite concentration (from 0 mg·L^− 1 to 500 mg·L^− 1), PEF (from 4 kV·cm^− 1 to 20 kV·cm^− 1; from 0.25 ms to 6 ms) and HVED (40 kV/cm; 1 ms or 4 ms) treatments on the inactivation of total yeasts and non-Saccharomyces yeasts was determined. The addition of SO₂ (250 mg·L^− 1) resulted in 8 log total yeast reduction. The maximum yeast inactivation obtained with PEF and HVED was respectively 3 and 4 logs. The use of SO₂, HVED and PEF allows decreasing the non-Saccharomyces yeast level by 7, 5 and 4 logs respectively. However, the wine browning was less pronounced for the samples treated by PEF in comparison with HVED and SO₂ treatments. PEF seems to be the most suitable alternative technique to sulfite addition.     

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 on Escherichia coli inactivation and quality attributes in apple juice treated by combinations of pulsed light and thermosonication

Pulsed light (PL) and Thermosonication (TS) were applied alone or in combination using a continuous system to study their effect on Escherichia coli inactivation in apple juice. Selected quality attributes (pH, °Brix, colour (L, a, b, ΔE), non-enzymatic browning (NEBI) and antioxidant activity (TEAC)) were also evaluated pre- and post-processing. Two PL (360 μs, 3 Hz) treatments were selected and the juice exposed to energy dosages of 4.03 J/cm² (‘low’ (L)) and 5.1 J/cm² (‘high’ (H)) corresponding to 51.5 and 65.4 J/mL, respectively. The juice was also processed by TS (24 kHz, 100 μm) at 40 °C for 2.9 min (L) or 50 °C for 5 min (H), corresponding to 1456 and 2531 J/ml energy inputs, respectively. The effect of the resulting four energy levels and sequence (PL + TS and TS + PL) was studied. When the technologies were applied individually the maximum reduction achieved was 2.7 and 4.9 log CFU/mL (for TS (H) and PL (H) respectively), while most of the combined treatments achieved reductions in the vicinity of 6 log CFU/mL, showing an additive effect for both technologies when acting in combination, regardless of the sequence applied. All treatments significantly changed the colour of apple juice and the sequence in which the technologies were applied affected colour significantly (P < 0.05). The energy level applied did not affect any of the measured quality attributes.     

Competitive interactions inside mixed-culture biofilms of Salmonella Typhimurium and cultivable indigenous microorganisms on lettuce enhance microbial resistance of their sessile cells to ultraviolet C (UV-C) irradiation

Salmonella Typhimurium (ST) is one of the leading causes of foodborne diseases in fresh produce, such as lettuce. Despite this, the role of the possible interactions between lettuce indigenous microorganisms and ST on their ability to form biofilm on lettuce and subsequently on the sensitivity of their sessile cells to ultraviolet C (UV-C) irradiation, remains relatively unexplored. Here, the interaction of a mixed-culture of ST and cultivable indigenous microorganisms (CIMs) was examined, as well as the efficacy of UV-C. Initially, the CIMs were isolated and cultured with ST at 15 °C either planktonically or left to form biofilms on stainless steel (SS) and lettuce leaves. Microbial growth, biofilm formation, and survival following UV-C treatment were monitored using traditional plate count methods while biofilm formation, production of extracellular polymeric substance (EPS), and stomatal colonization were also observed by field emission scanning electron microscopy (FESEM). Internalization strength, color, and texture were analyzed by standard methods. Results revealed that the mixed-culture of ST and CIMs presented significantly (p < 0.05) decreased biofilm formation on lettuce leaves compared to mono-cultures (i.e. ST or CIMs alone), which indicated competitive interaction between them, while no interactions were observed for biofilms on SS and for the planktonic cultures. It was also demonstrated that a mixed-culture biofilm on lettuce presented significantly higher resistance (p < 0.05) to UV-C treatment compared to mono-culture biofilms, but such an effect was not observed for biofilms formed on SS and for the planktonic cultures. The Weibull model fitted well to microbial inactivation curves with R² values that ranged from 0.90 to 0.97. Regarding the mixed-culture conditions, a UV-C fluency of 35 mJ/cm² was required to achieve a 5.0 log CFU/mL or cm² reduction in planktonic and biofilms on the SS for the mixed-culture, while 360 mJ/cm² was required to reduce biofilm cell number by approximately 2.0 log CFU/cm² on lettuce. Furthermore, FESEM analysis indicated higher EPS production, and greater stomatal colonization on lettuce mixed-cultures compared to mono-cultures. Finally, internalization strength was significantly higher (p < 0.05) for the mixed-culture on lettuce, thus supporting the notion that internalization in lettuce is a factor that contributes to microbial UV-C resistance. The absence of adverse effects of UV-C on the color and texture of the lettuce suggests it as an alternative means of eliminating ST.     

Thermal and light stabilities and antioxidant activity of carotenoids from tomatoes extracted using an ultrasound-assisted completely solvent-free method

The use of petroleum-derived solvents, particularly volatile organic compounds (VOCs), in the chemical industry has increased the contamination and residual effects of these solvents. Ionic liquids (ILs) can potentially replace VOCs, thereby reducing the risks of environmental contamination and toxicity. In this context, the objectives of this study were as follows: 1 — to obtain an ionic liquid for use in extracting carotenoids from tomatoes with ultrasound assistance; and 2 — to determine the stability and antioxidant activity of tomato carotenoid extracts. Ultrasound can also efficiently extract carotenoid compounds with ionic liquids in comparison with conventional VOC solvents (obtained from an all-trans-lycopene 7.5–8.0 μg·g^− 1 tomato sample by IL and 6.2–7.7 μg·g^− 1 by acetone). Similarly, the activation energies (E_a) in aqueous medium were obtained for the IL carotenoid extract (10.8 kJ·mol^− 1) and acetone carotenoid extract (9.4 kJ·mol^− 1). The antioxidant activities of the tomato carotenoid extract were 7.4 and 12.4 relative to α-tocopherol for the ionic liquid extract and acetone extract, respectively. The combination of chromatographic analysis and degradation kinetics provided data for positive assessment similarity of thermal and light stabilities of tomato carotenoids extracted by IL and extracted by acetone.     

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.     

Quality comparison of carrot juices processed by high-pressure processing and high-temperature short-time processing

The effects of high-pressure processing (HPP) at 550 MPa for 6 min and of high-temperature short-time (HTST) processing at 110 °C for 8.6 s on carrot juice were evaluated. After HPP and HTST, the total plate count (TPC) was found to significantly decrease by 4.30 and 4.88 log₁₀ CFU/mL, respectively, and yeasts and molds (Y&M) were completely inactive. HPP-treated juice showed higher carotenoids, polyphenols, antioxidant capacity, viscosity, turbidity, and lower browning degrees (BDs) than HTST-treated juice, while HTST-treated juice contained higher polyacetylenes. HPP provided a more fresh-like quality and exhibited better aroma, taste, and overall acceptability. During 20 days of storage at 4 °C, both HPP- and HTST-treated juices were microbiologically safe (i.e., TPC < 2.4 log₁₀ CFU/mL, and Y&M were not detected), and their antioxidant capacities decreased linearly due to a decrease in carotenoid and polyphenol contents. The two juices did not precipitate any solids when their particle sizes decreased, and their viscosity increased; however, their organoleptic properties deteriorated as storage time increased.Industrial RelevanceThis study was intended to develop fresher and more stable carrot juice, which is not available on the market now. Acid blanching for a proper time was proved as an effective process in preventing juice serum isolation phenomenon of HPP juice, which is more likely to be accepted by consumers. HPP-treated juice had an advantage in nutritional and organoleptic properties than HTST-treated juice. This study provided a comprehensive technical support for novel application of HPP in carrot juice processing.