Effect of UV-C and UV-B treatment on polyphenol oxidase activity and shelf life of apple and grape juices

Variations in quality attributes of pulsed light-treated table grape juice during refrigerated storage (4°C) and ambient conditions (25°C)

Pulsed light (PL) pasteurization is being explored as a substitute for the conventional thermal pasteurization of juices in recent times due to better retention of nutrients and overall quality. However, the long-term stability of the PL-pasteurized juice must be investigated to promote its application by the industry. The effect of PL treatment (effective fluence of 1.15 J·cm-2) and thermal treatment (90°C for 60 s) on microbial quality, enzyme activity, bioactive compounds, sensory acceptance, and color profile of table grape juice during storage at 4 and 25°C was investigated in this study. The PL pasteurization enhanced the microbial shelf-life of the juice (<6 log10cfu·mL-1) from 5 to 35 days at 4°C. The PL and thermally-pasteurized juice demonstrated a shelf-life of only 10 days when stored at 25°C. The total soluble solids and titratable acidity did not alter significantly throughout the storage period. The peroxidase, polyphenol oxidase, and pectin methylesterase activities were below 10% for the PL and thermally-treated beverage when stored at 4°C. The sensory acceptability of the PL-pasteurized juice after 35 days of refrigerated storage (6.9 ± 0.3) was close to the untreated juice (7.2 ± 0.3) and greater than thermally-treated juice (6.2 ± 0.2). After the 35th day of storage at 4°C, PL-treated grape juice retained 55%, 12%, and 15.3% more phenolics, flavonoids, and antioxidant capacity, respectively, than the thermally-pasteurized juice. Hence, PL pasteurization can effectively prolong the shelf-life of table grape juice while achieving microbial and enzymatic stability, along with high sensory and nutritional appeal. PRACTICAL APPLICATION: Exploring non-thermal methods like pulsed light (PL) pasteurization as a substitute for conventional thermal methods is gaining recognition for its ability to retain nutrients and improve overall juice quality. However, the industry's adoption depends on understanding the shelf-stability of PL-pasteurized juice. This study specifically investigates the practical applications of PL treatment in comparison with conventional thermal treatment in enhancing microbial safety and enzymatic stability in table grape juice. The findings contribute insights into optimizing the shelf life of table grape juice and preserving its quality, supported by microbial, enzymatic, and sensory evaluations.

Effect of UV LED and Pulsed Light Treatments on Polyphenol Oxidase Activity and Escherichia coli Inactivation in Apple Juice

Enzymatic browning in fruits and vegetables, driven by polyphenol oxidase (PPO) activity, results in color changes and loss of bioactive compounds. Emerging technologies are being explored to prevent this browning and ensure microbial safety in foods. This study assessed the effectiveness of pulsed light (PL) and ultraviolet light-emitting diodes (UV-LED) in inhibiting PPO and inactivating Escherichia coli ATTC 25922 in fresh apple juice (Malus domestica var. Red Delicious). Both treatments' effects on juice quality, including bioactive compounds, color changes, and microbial inactivation, were examined. At similar doses, PL-treated samples (126 J/cm2) showed higher 2,2- diphenyl-1-picrylhydrazyl inhibition (9.5%) compared to UV-LED-treated samples (132 J/cm2), which showed 1.06%. For microbial inactivation, UV-LED achieved greater E. coli reduction (>3 log cycles) and less ascorbic acid degradation (9.4% ± 0.05) than PL. However, increasing PL doses to 176 J/cm2 resulted in more than 5 log cycles reduction of E. coli, showing a synergistic effect with the final temperature reached (55 °C). The Weibull model analyzed survival curves to evaluate inactivation kinetics. UV-LED was superior in preserving thermosensitive compounds, while PL excelled in deactivating more PPO and achieving maximal microbial inactivation more quickly.

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 ultraviolet light-emitting diode processing on fruit and vegetable-based liquid foods: A review

Ultraviolet light-emitting diode (UV-LED) technology has emerged as a non-thermal and non-chemical treatment for preserving liquid fruit and vegetable foods. This technology uses ultraviolet light to interact with the food at different wavelengths, solving problems related to product stability, quality, and safety during storage. UV-LED treatment has been shown to affect microbe and enzyme inactivation, and it increases and improves retention of bioactive compounds. Moreover, computational simulations are a powerful and relevant tool that can be used optimize and improve the UV-LED process. Currently, there are a limited studies of this technology in liquid fruit and vegetable-based foods. This review gathers information on these food type and shows that it is a promising technology for the development of new products, is environmentally friendly, and does not require the addition of chemicals nor heat. This is relevant from an industrial perspective because maintaining the nutritional and organoleptic properties ensures better quality. However, due to the scarce information available on this type of food, further studies are needed.

Stability of polyphenols in food processing

In recent years, polyphenols have attracted considerable attention due to their diverse potential health-beneficial effects on humans. Polyphenols are widely distributed in natural plants, and therefore play an important role in human food. Thermal processing, irradiation, fermentation, high pressure, microwave, and drying are several popular food processing methods. However, polyphenols are instable in food processing, which easily degrade and react with other components because of their polyhydroxy characteristic. Traditional and advanced technologies have been used to characterize the stability of polyphenols. The main influence factors of stability of polyphenols such as pH, temperature, light, oxygen, enzymes, metal ions, as well as macromolecules, are summarized. Besides, thermal processing greatly promoted the degradation of polyphenols. Thermal degradation mechanisms and products of some polyphenols, such as quercetin and rutin, have been intensively demonstrated. Nevertheless, the structural changes of polyphenols caused by food processing, may lead to different bioactivities from the obtained results based on unprocessed polyphenols. Therefore, to maximize the beneficial effects of polyphenols ingested by human from processed food, the stability of polyphenols in food processing must be thoroughly investigated to assess their real bioactivities. In addition, some available technologies for improving the stability of polyphenols in food processing have been proposed.

UV-C treatment inhibits browning, inactivates Pseudomonas tolaasii and reduces associated chemical and enzymatic changes of button mushrooms

BACKGROUND

Button mushrooms with completely white appearance are popular with consumers. However, button mushrooms are susceptible to infection with Pseudomonas tolaasii, which results in browning. This study evaluates the effects of ultraviolet-C (UV-C) treatment on the inactivation of P. tolaasii in vitro and in vivo and on the physiological and chemical changes of button mushrooms during storage for 21 days at 4 °C.

RESULTS

UV-C doses of 0.5 to 9.0 kJ m^-2 resulted in 3.91-6.26 log CFU mL^-1 reduction of P. tolaasii populations in vitro, and UV-C treatment reduced P. tolaasii populations inoculated on mushroom cap surfaces and browning severity. Moreover, P. tolaasii increased polyphenol oxidase (PPO) activity, and decreased phenylalanine ammonia-lyase (PAL) activity, the accumulation of phenolics and contents of brown melanin precursors, including γ-l-glutaminyl-4-hydroxybenzene (GHB), γ-l-glutaminyl-3,4-dihydroxybenzene (GDHB), and tyrosine in button mushrooms. UV-C treatment was found to reduce the negative changes due to P. tolaasii infection.

CONCLUSION

These results indicated that the application of UV-C treatment inhibited browning, inactivated P. tolaasii and reduced P. tolaasii - associated chemical and enzymatic changes of button mushrooms. © 2021 Society of Chemical Industry.

Thermal treatment alternatives for enzymes inactivation in fruit juices: Recent breakthroughs and advancements

Fruit juices (FJs) are frequently taken owing to their nutritious benefits, appealing flavour, and vibrant colour. The colours of the FJs are critical indicators of the qualitative features that influence the consumer's attention. Although FJs' intrinsic acidity serves as a barrier to bacterial growth, their enzymatic stability remains an issue for their shelf life. Inactivation of enzymes is critical during FJ processing, and selective inactivation is the primary focus of enzyme inactivation. The merchants, on the other hand, want the FJs to stay stable. The most prevalent technique of processing FJ is by conventional heat treatment, which degrades its nutritive value and appearance. The FJ processing industry has undergone a dramatic transformation from thermal treatments to nonthermal treatments (NTTs) during the past two decades to meet the requirements for microbiological and enzymatic stability. The manufacturers want safe and stable FJs, while buyers want high-quality FJs. According to the past investigation, NTTs have the potential to manufacture microbiologically safe and enzymatically stable FJs with low loss of bioactive components. Furthermore, it has been demonstrated that different NTTs combined with or without other NTTs or mild heating as a hurdle technology increase the synergistic effect for microbiological safety and stability of FJs. Concise information about the variables that affect NTTs' action mode has also been addressed. Primary inactivates enzymes by modifying the protein structure and active site conformation. NTTs may increase enzyme activity depending on the nature of the enzyme contained in FJs, the applied pressure, pH, temperature, and treatment period. This is due to the release of membrane-bound enzymes as well as changes in protein structure and active sites that allow substrate interaction. Additionally, the combination of several NTTs as a hurdle technology, as well as temperature and treatment periods, resulted in increased enzyme inactivation in FJs. Therefore, a combination of thermal and non-thermal technologies is suggested to increase the effectiveness of the process as well as preserve the juice quality.

Ifs and buts of non-thermal processing technologies for plant-based drinks' bioactive compounds

Vegetables and fruits contain a variety of bioactive nutrients and non-nutrients that are associated with health promotion. Consumers currently demand foods with high contents of healthy compounds, as well as preserved natural taste and flavour, minimally processed without using artificial additives. Processing alternatives to be applied on plant-based foodstuffs to obtain beverages are mainly referred to as classical thermal treatments that although are effective treatments to ensure safety and extended shelf-life, also cause undesirable changes in the sensory profiles and phytochemical properties of beverages, thus affecting the overall quality and acceptance by consumers. As a result of these limitations, new non-thermal technologies have been developed for plant-based foods/beverages to enhance the overall quality of these products regarding microbiological safety, sensory traits, and content of bioactive nutrients and non-nutrients during the shelf-life of the product, thus allowing to obtain enhanced health-promoting beverages. Accordingly, the present article attempts to review critically the principal benefits and downsides of the main non-thermal processing alternatives (High hydrostatic pressure, pulsed electric fields, ultraviolet light, and ultrasound) to set up sound comparisons with conventional thermal treatments, providing a vision about their practical application that allows identifying the best choice for the sectoral industry in non-alcoholic fruit and vegetable-based beverages.

Physical, Chemical and Microbiological Properties during Storage of Red Prickly Pear Juice Processed by a Continuous Flow UV-C System

The effects of pH (3.6 and 7.0) and irradiation UV-C dose irradiation (0, 9.81, 15.13, and 31.87 mJ/cm2) on the physicochemical properties and natural microbiota of red prickly pear juice were evaluated during processing and storage. Thermal treatments were used as the control applying high temperatures for a short time (HTST 80 °C/30 s) or ultra-high temperature (UHT 130 °C/3 s). UV-C treatments applied to juices with both pHs inactivated coliforms and mesophiles with the same efficacy as thermal treatments. Yeasts and molds were inactivated at a dose of >15.13 mJ/cm2 at both pHs. The UV-C doses showed no differences in betalains, polyphenols, or antioxidant activity. However, a decrease in these compounds was observed during storage. The lowest reductions in betacyanins (11.1–16.7%) and betaxanthins (2.38–10.22%) were obtained by UV-C treatment at pH 3.6. Thermal treatments (HTST and UHT) caused a reduction greater than UV-C irradiation in betacyanins, betaxanthins, polyphenols, and antioxidant activity after treatment. However, after storage at pH 3.6, the contents of these compounds reached those of the UV-C treatments, except for polyphenols. In specific pigments, betanin retention was highest at pH 3.6 (62.26–87.24%), and its retention decreases with UV-C dose increase and storage. The indicaxanthin retentions were higher (75.85–92.27%) than those of betanin, and the reduction was mainly due to storage. The physical properties (pH, acidity, and °Brix) were not affected by treatments, except for the color. The results suggest that a dose of 15.13 mJ/cm2 of a continuous UV-C system is a non-thermal alternative for the processing of red prickly pear juice at pH 3.6, preserving its properties.

Effect of whey protein isolate/chitosan/microcrystalline cellulose/PET multilayer bottles on the shelf life of rosebud beverages

Multilayer bottles consisting of chitosan (CS), microcrystalline cellulose (MCC), whey protein isolate (WPI), and polyethylene terephthalate (PET) were tested as novel materials for packaging and extending shelf life of rosebud beverages. We studied the storage stability at 4 °C, 25 °C, 37 °C, and 55 °C by assessing the physical and biochemical parameters. The results show that multilayer PET bottles had better barrier performance and improved soluble solids content, pH, polyphenol content, color indices, and browning degree in rosebud beverages over the control at all studied temperatures. A shelf life model was established based on the Arrhenius equation, and the number of days when polyphenol contents dropped to <50% of the initial content was defined as the shelf life. Our results highlight the reliability of the prediction model, and we conclude that packaging rosebud beverages in multilayer PET bottles significantly extends the product shelf life, and this benefit was further extended at low temperatures.

Effect of UV-C irradiation on the inactivation kinetics of oxidative enzymes, essential amino acids and sensory properties of coconut water

The impact of ultraviolet light (UV-C) irradiation on oxidative enzymes [Polyphenol oxidase (PPO) and Peroxidase (POD)], free essential amino acids and sensory profile of coconut water were investigated. PPO and POD activities were lost to 94 and 93%, respectively of its original value at fluence level of 400 mJ/cm2. Inactivation kinetics of both enzymes were fitted to nonlinear Weibull model with an increase in UV dosage with a high coefficient of determination (R2 > 0.97) and low root mean square error (RMSE < 0.06). No significant change was observed in all essential amino acids (p > 0.05) after UV-C treatment up to maximum delivered fluence of 400 mJ/cm2. Sensory attributes of coconut water up to a treated UV-C fluence level of 200 mJ/cm2 were well retained in terms of chosen descriptors (p > 0.05). This study allow to further investigate the development of UV-C light technology for inhibition of spoilage enzymes and prolonged shelf-life of low acid beverages.

Effect of Pulsed Light Treatment on Natural Microbiota, Enzyme Activity, and Phytochemical Composition of Pineapple (Ananas comosus [L.] Merr.) juice

The effect of pulsed light (PL) on numerous important quality characteristics of pineapple juice was studied and compared with untreated and thermally pasteurised samples. The laboratory scale PL batch system used was operated with each three different voltages (1.8, 2.1, and 2.4 kV) and numbers of pulses (47, 94, and 187). Treatments with 2.4 kV and either 94 or 187 pulses (757/1479 J·cm−2) resulted in a 5-log reduction in aerobic mesophiles and the yeast and mould counts. Peroxidase was more resistant to PL than polyphenol oxidase, whereas the bromelain activity was completely retained in all PL-treated juices. Colour and antioxidant capacity were minimally affected, while vitamin C, genuine pineapple furanones, and phenolic compounds declined. In contrast, thermal pasteurisation was more detrimental to colour, antioxidant capacity, and vitamin C content, but resulted in a superior inactivation of microorganisms and enzymes and retention of phenolic compounds. Principal component analysis (PCA) permitted the differentiation of fresh, thermally pasteurised, and all PL-treated juices. PCA on the basis of the individual juice constituents additionally arranged the latter juices according to the number of pulses and voltage levels applied, particularly promoted by the oxidation of ascorbic to dehydroascorbic acid. In conclusion, PL treatment represents a promising new alternative to conventional thermal preservation techniques, whereby the inactivation of deteriorative enzymes may be further optimised.

Influence of a Selenium Biofortification on Antioxidant Properties and Phenolic Compounds of Apples (Malus domestica)

Biofortified apples seem to be a suitable produce. In this study, different selenium forms and application levels were applied to the two apple varieties ‘Golden Delicious’ and ‘Jonagold’, grown in the years 2017 and 2018 in order to increase the selenium uptake within a typical Western diet. It was shown that the biofortification, which was performed as a foliar application implemented in usual calcium fertilization, led to significantly increased selenium contents in the fruits. Furthermore, biofortification affected the total phenolic content (TPC), the polyphenol oxidase activity (PPO), as well as the antioxidant activity (AOA), the latter measured with the two well-known assays Trolox Equivalent Antioxidant Capacity Assay (TEAC) and Oxygen Radical Absorbance Capacity Assays (ORAC). The varying selenium forms and application levels showed a differing influence on the parameters mentioned before. Higher fertilizer levels resulted in higher selenium accumulation. It was found that PPO activity fluctuates less in biofortified apples. With regard to TPC, selenate led to higher amounts when compared to the untreated controls and selenite resulted in lower TPC. AOA analysis showed no clear tendencies as a result of the selenium biofortification. In the case of ‘Jonagold’, a higher AOA was generally measured when being biofortified, whereas, in the case of ‘Golden Delicious’, only one form of application led to higher AOA. Additionally, differences in the amount of major phenolic compounds, measured with High Performance Liquid Chromatography Mass Spectrometry (HPLC-DAD-ESI-MSⁿ), were observed, depending on the conditions of the biofortification and the variety.

Shelf Life Extension of Tomato Paste Through Organoleptically Acceptable Concentration of Betel Leaf Essential Oil Under Accelerated Storage Environment

This study was attempted with two objectives: (1) to find an acceptable concentration of betel leaf essential oil (BLEO) based on sensory evaluation that can be employed in tomato paste; (2) to evaluate the effect of the acceptable concentration of BLEO in the paste during accelerated storage under 89 ± 1.2% RH at 39 ± 1 °C. Linguistic data obtained from sensory evaluation of tomato paste treated with 4 different concentrations of BLEO were analyzed using fuzzy logic approach. The organoleptically acceptable concentration was determined to be 0.25 mg/g of BLEO in tomato paste. The effect of the selected concentration of BLEO on different physicochemical and microbial attributes of tomato paste during accelerated storage was studied. Untreated tomato paste was found to have 12% less total antioxidant capacity than treated paste at the end of storage. Based on a^* /b^* value in CIELAB color space, the BLEO treated paste efficiently extended the shelf life by 14 days with respect to untreated paste samples under accelerated storage conditions. BLEO comes with a tag contributing to green consumerism, and its application as food preservative is no less than a value addition to the product.

PRACTICAL APPLICATIONS

Essential oil is considered to have promising potential as an alternative food preservative, and its use is practically possible if they could overcome the sensory barrier, while retaining the preservative potency. The importance of identifying the sensory attributes for commercial success of essential oil treated food product was considered in this study. It contributes to the potency of organoleptically acceptable concentration of BLEO in shelf life extension of tomato paste under accelerated storage conditions. At industrial level, the estimated shelf life of treated tomato paste can be increased by incorporating more hurdles alongside BLEO.

The use of fuzzy logic to determine the concentration of betel leaf essential oil and its potency as a juice preservative

The present study was attempted to determine organoleptically acceptable concentration of betel leaf essential oil (BLEO) in raw apple juice using fuzzy logic approach, and to evaluate the efficacy of the acceptable concentration in the juice under refrigerated storage. The presence of BLEO components in treated juice was confirmed by FTIR spectroscopy. Based on similarity values, the acceptable concentration in the juice was found to be 0.19µl/ml of BLEO. Total antioxidant capacity of untreated juice was found to be 16% less than treated juice at the end of storage. The treated juice exceeded total aerobic plate count of 2 log₁₀ (cfu/ml) on 15th day of storage. Based on safe limits of microbial load, the shelf life of treated juice was extended by 6days as compared to untreated juice under refrigerated storage. BLEO contributes to green consumerism and its application as food preservative will add value to the product.

Effect of high-pressure processing and thermal pasteurization on overall quality parameters of white grape juice

BACKGROUND

The aim of this study was to investigate the microbial levels, physicochemical and antioxidant properties and polyphenol oxidase (PPO) and peroxidase (POD) activities as well as to conduct a sensory analysis of white grape juice treated with high-pressure processing (HPP) and thermal pasteurization (TP), over a period of 20 days of refrigerated storage.

RESULTS

HPP treatment of 600 MPa and TP significantly reduced aerobic bacteria, coliform and yeast/mold counts. At day 20 of storage, HPP-600 juice displayed no significant differences compared with fresh juice in terms of physicochemical properties such as titratable acidity, pH and soluble solids, and retained less than 50% PPO and POD activities. Although significant differences were observed in the color, antioxidant contents and antioxidant capacity of HPP-treated juice, the extent of these differences was substantially lower than that in TP-treated juice, indicating that HPP treatment can better retain the quality of grape juice. Sensory testing showed no significant difference between HPP-treated juice and fresh juice, while TP reduced the acceptance of grape juice.

CONCLUSION

This study shows that HPP treatment maintained the overall quality parameters of white grape juice, thus effectively extending the shelf life during refrigerated storage. © 2016 Society of Chemical Industry.

Effect of UV Irradiation on the Nutritional Quality and Cytotoxicity of Apple Juice

UV-C irradiation operating at 254 nm wavelength on the polyphenolic and vitamin contents of apple juice including cytotoxicity analysis was studied. UV doses ranging from 0 to 150 mJ·cm^-2 were selected for the treatments. Polyphenols (catechin, epicatechin, chlorogenic acid, and phloridzin) and vitamins (riboflavin, thiamine hydrochloride, pyridoxal hydrochloride, pyridoxine, pyridoxamine dihydrochloride, cyanocobalamin, choline chloride, biotin, niacin, and niacinamide) were chemically profiled. It was observed that UV treatment of apple juice at disinfection doses caused minor reductions (p < 0.05) in the concentrations of two main polyphenols (i.e., chlorogenic acid and epicatechin). In contrast, significant (p < 0.05) decreases in vitamin concentrations were observed (p < 0.05). The irradiated juice was evaluated for cytotoxic effects. The irradiated apple juice showed no cytotoxic effects on normal intestinal cells, and both irradiated and nonirradiated samples are significantly comparable in inhibiting the growth of human colon cancer cells. Overall, these results indicated that UV-C treatment of apple juice neither significantly degraded polyphenols nor generated cytotoxic compounds.