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.

Pulsed light treatment of whole white button mushroom (Agaricus bisporus): Kinetics and mechanism of microbial inactivation and storage study

The whole white button mushrooms (WWBMs) are highly perishable due to susceptibility to microbial spoilage. This study explored the potential of pulsed light (PL) treatment for decontamination and shelf-life extension of WWBM. WWBM surface was inoculated with Escherichia coli, Listeria monocytogenes, and Aspergillus niger spores (8.1, 8.0, and 8.05 log10 CFU/g, respectively) and tested for inactivation against various PL intensities (fluence 0.13-0.75 J/cm2). The kinetics and mechanism of microbial inactivation were explored, and shelf life was determined at 4, 20, and 37°C. Microbial inactivation increased with increasing PL intensity. PL-induced microbial inactivation was well explained by Weibull model with shape parameters (β-value) for E. coli, L. monocytogenes, A. niger, aerobic mesophiles, and yeast and mold as 0.87, 0.92, 0.91, 0.89, and 0.94, respectively. PL-treatment at 0.75 J/cm2 resulted in >5-log cycle reduction in all inoculated and natural microorganisms. Exposure to PL led to collapse of cellular structure, ruptured cell wall, and leakage of cellular material in all microorganisms and spores along with alterations in nucleic acid and lipid bands. At 4°C, maximum shelf life of 5 days was achieved when WWBM was exposed at 0.75 J/cm2. The WWBM retained 83.3% phenolics, 83.9% antioxidant capacity, and 77.4% vitamin D2 at 4°C while reducing the polyphenol oxidase and peroxidase activity by 89% and 79%. The degradation rate for quality parameters increased with storage temperature. The activation energy of the browning index affirmed it as the most sensitive quality attribute during storage. The study concluded the potential of PL treatment to prolong the shelf life of WWBM.

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.

Effect of dehydration and pulsed light treatment on decontamination of minced onions: Microbial safety and physicochemical properties

Microbial contamination of dehydrated onion products is a challenge to the industry. The study focused on opting for a suitable drying condition for minced onion and exploring the decontamination efficacy of pulsed light (PL) treatment conditions for the dehydrated product. The minced onions were hot air dried at 55-75°C for 280 min. The drying condition selected was 195 min at 75°C with a final water activity of 0.5 and moisture content of 7% (wet basis [w.b.]). The weight losses, browning indexes (BI), shrinkage volumes (%), and thiosulfinate content were considered. The dehydrated product was exposed to PL treatment corresponding to an effective fluence range of 0.007-0.731 J/cm2. A fluence of 0.444 J/cm2 (1.8 kV for 150 s) achieved 5.00, 3.14, 2.96, and 2.98 log reduction in total plate count, yeast and mold count, Bacillus cereus 10876, and Escherichia coli ATCC 43888, respectively. The PL-treated sample (0.444 J/cm2) produced a microbially safe product with no significant difference in the moisture contents (%w.b.) and water activity (aw) from the untreated dehydrated sample. Further, a 30.9% increase in the BI and a 4.25% depletion in thiosulfinate content were observed after PL treatment. An optimum drying combination (75°C for 195 min) of minced onion followed by decontamination using pulsed light treatment at 0.444 J/cm2 fluence satisfies the microbial safety and quality. PRACTICAL APPLICATION: Dehydrated minced onion can be used for dishes requiring low water content and short cooking time. It is helpful during shortages, high price fluctuations, and famines.

Emerging biotechnologies and non-thermal technologies for winemaking in a context of global warming

In the current situation, wine areas are affected by several problems in a context of global warming: asymmetric maturities, pH increasing, high alcohol degree and flat wines with low freshness and poor aroma profile. The use of emerging biotechnologies allows to control or manage such problems. Emerging non-Saccharomyces as Lachancea thermotolerans are very useful for controlling pH by the formation of stable lactic acid from sugars with a slight concomitant alcohol reduction. Lower pH improves freshness increasing simultaneously microbiological stability. The use of Hanseniaspora spp. (specially H. vineae and H. opuntiae) or Metschnikowia pulcherrima promotes a better aroma complexity and improves wine sensory profile by the expression of a more complex metabolic pattern and the release of extracellular enzymes. Some of them are also compatible or synergic with the acidification by L. thermotolerans, and M. pulcherrima is an interesting biotool for reductive winemaking and bioprotection. The use of bioprotection is a powerful tool in this context, allowing oxidation control by oxygen depletion, the inhibition of some wild microorganisms, improving the implantation of some starters and limiting SO2. This can be complemented with the use of reductive yeast derivatives with high contents of reducing peptides and relevant compounds such as glutathione that also are interesting to reduce SO2. Finally, the use of emerging non-thermal technologies as Ultra High-Pressure Homogenization (UHPH) and Pulsed Light (PL) increases wine stability by microbial control and inactivation of oxidative enzymes, improving the implantation of emerging non-Saccharomyces and lowering SO2 additions. GRAPHICAL ABSTRACT.

Evaluation of dry microwave and hot water blanching on physicochemical, textural, functional and organoleptic properties of Indian gooseberry (Phyllanthus emblica)

Indian gooseberry (Phyllanthus emblica) is a seasonal and highly nutritious fruit with shorter shelf-life and astringent taste limiting its utilization. The enzymatic browning and flavor loss are major concerns which makes pre-processing a crucial step for further processing. In this context, dry microwave blanching (MWB) was explored as an alternative to hot-water (HW) blanching to reduce its nutrition losses particularly ascorbic acid (AA) and makes it easier for removal of seed kernel. This study focused on the effect of MW power level (200–500 W) and blanching time (50–100 s) on AA content, color attributes (L*, a*, b*), and enzymatic inhibition in Indian gooseberry. The optimized MWB conditions were 294 W MW power with 70 s blanching time providing satisfactory enzymatic inhibition (75.47%), and retention of AA (417.70 mg/100 g pulp) and color attributes (L*: 58.42, a*: 4.57, b*: 26.23). As compared to HWB (80 °C, 5 min), MWB showed least AA degradation, higher total phenolic content and softening percent with less total color difference owing to its shorter processing time and dry blanching. Quantitative descriptive analysis (QDA) demonstrated that raw and MW blanched Indian gooseberries are the most accepted, followed by HW blanched samples. MWB showed better nutrient retention than HWB with easier seed removal showed the application of MW radiation for blanching of other fruits.

A chemometric approach to evaluate the effects of probe-type ultrasonication on the enzyme inactivation and quality attributes of fresh amla juice

The enzymatic browning induced in amla juice due to the high activity of polyphenol oxidase (PPO) and peroxidase (POD) is one of the critical issues faced by the industry. The present study assessed the suitability of non-thermal, high-intensity ultrasound (US) on the inactivation of PPO and POD in fresh Indian Gooseberry juice. Ultrasonic waves, using a 6 mm titanium alloy probe were irradiated in the juice at a maximum power of 455 W and frequency of 20 kHz. The subsequent effects on biochemical attributes were studied using response surface methodology. Inactivation rates of 90.72 % and 73.18 %, respectively, for PPO and POD enzymes, were observed at the highest US intensity and exposure time. Numerical optimisation using the three-factor, three-level Box-Behnken design suggested that an optimum process at 70 % (energy density: 1610 Wcm-2) pulsed at 5 s on and 5 s off for 7 min 30 s resulted in PPO and POD inactivation of the order of 76.42 % and 64.57 % respectively. At these experimental conditions, the optimized levels of biochemical attributes i.e., ascorbic acid (738.50 mg/100 mL), total phenols (17.10 mg/mL), DPPH antioxidant activity (58.47 %), tannins (7.11 µg/mL), colour change (ΔE = 9.04) and flavonoids (6.14 mg/mL) were achieved. The overall statistical models were significant for all the responses except for reducing sugars. Furthermore, the approximation equations for individual responses indicated that the goodness of fit was adequate (R2 > 0.90). The results suggested that ultrasound is a suitable processing technique for amla juice stabilisation compared to thermal treatments that result in the loss of quality.

Effect of pressure and time on bioactive content, PPO inactivation, physicochemical and sensory properties of aonla (Emblica officinalis) juice during hydrodynamic cavitation processing

Physical and nutritional attributes of aonla juice treated with hydrodynamic cavitation (HC) at a pressure range of 5-15 psi and time between 5 to 30 min were evaluated. Based on maximum retention of bioactives, antioxidant activity, inactivation of polyphenol oxidase (PPO), and physicochemical properties, HC conditions were optimized at 10 psi for 15 min, based on retention of 92.19% antioxidant activity, 88.01% vitamin C, and 96.80% of total phenolic content. Improved sedimentation index and viscosity were noted due to HC processing. The color profile of HC-treated samples was improved with less browning (63.86) and yellowing index (14.79) than that of control (browning index 64.61). Thermally treated samples inactivated 100% of PPO at 95 ℃ for 3 min, however, formation of a dark color with a browning index value of 67.38 was noted. The retention of various bioactives in thermally treated juice samples was much lesser than that of HC-treated samples.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01164-2.

Insight about the biochemical composition, postharvest processing, therapeutic potential of Indian gooseberry (amla), and its utilization in development of functional foods-A comprehensive review

Indian gooseberry/Amla (Emblica officinalis Gaertn. syn. Phyllanthus emblica L) has an amazing nutritional profile and is a reservoir of biologically active compounds which have potential health benefits and are regarded as a remedy for lethal diseases. The unique features of amla, conferred by their bioactive components, have extended future prospects about their usage for useful effects on human nutrition and health globally. With the rapidly growing popularity of this unique therapeutic fruit, it is important to have comprehensive knowledge of this fruit. The current review article presents the nutritional profile, bioactive components, antioxidant and antimicrobial properties, and postharvest processing of amla fruit. Moreover, studies related to therapeutic properties of amla and its utilization in development of functional foods have been presented in this review. E. officinalis is a promising source of bioactive compounds which showed varied potential in the management of a number of human ailments which has been proven through various studies. Therefore, amla should be taken in the regular diet, thereby utilizing its potential health benefits. PRACTICAL APPLICATIONS: Amla (Indian gooseberry), as source of natural bioactive compounds, has a great potential application in improving the status of human nutrition and health. The utilization of amla extract has various biological effects, like antimicrobial, antioxidant, gastroprotective, anticancer, hepatoprotective, cardioprotective, radioprotective, anti-inflammatory, antidiabetic, neuroprotective, and immunomodulatory effect, owing to its bioactive components. The use of amla extract has recently increased in food, pharmaceutical, and cosmetic products to replace synthetic antioxidants which have inherent harmful health effects. The review report will provide information on bioactive components, therapeutic properties, utilization of amla in the development of future functional foods, and postharvest processing of amla, which will provide critical information to researchers all over the world.

Pasteurization of fruit juices by pulsed light treatment: A review on the microbial safety, enzymatic stability, and kinetic approach to process design

Pulsed light (PL) is a polychromatic radiation-based technology, among many other non-thermal processing techniques. The microbiological lethality of the PL technique has been explored in different food matrices along with their associated mechanisms. Pasteurization of fruit juice requires a 5-log cycle reduction in the resistant pathogen in the product. The manufacturers look toward achieving the microbial safety and stability of the juice, while consumers demand high-quality juice. Enzymatic spoilage in fruit juice is also a crucial factor that needs attention. The retailers want the processed juice to be stable, which can be achieved by inactivating the spoilage enzymes and native microflora inside it. The present review argued about the potential of PL technology to produce a microbiologically safe and enzymatically stable fruit juice with a minimal loss in bioactive compounds in the product. Concise information of factors affecting the PL treatment (PLT), primary inactivation mechanism associated with microorganisms, enzymes, the effect of PLT on various quality attributes (microorganisms, spoilage enzymes, bioactive components, sensory properties, color), and shelf life of fruit juices has been put forward. The potential of PL integrated with other non-thermal and mild thermal technologies on the microbial safety and stability of fruit juices has been corroborated. The review also provides suggestions to the readers for designing, modeling, and optimizing the PLT and discusses the use of various primary, secondary kinetic models in detail that have been utilized for different quality parameters in juices. Finally, the challenges and future need associated with PL technology has been summarized.

Effect of Alternative Preservation Steps and Storage on Vitamin C Stability in Fruit and Vegetable Products: Critical Review and Kinetic Modelling Approaches

Vitamin C, a water-soluble compound, is a natural antioxidant in many plant-based products, possessing important nutritional benefits for human health. During fruit and vegetable processing, this bioactive compound is prone to various modes of degradation, with temperature and oxygen being recognised as the main factors responsible for this nutritional loss. Consequently, Vitamin C is frequently used as an index of the overall quality deterioration of such products during processing and post-processing storage and handling. Traditional preservation methods, such as thermal processing, drying and freezing, are often linked to a substantial Vitamin C loss. As an alternative, novel techniques or a combination of various preservation steps ("hurdles") have been extensively investigated in the recent literature aiming at maximising Vitamin C retention throughout the whole product lifecycle, from farm to fork. In such an integrated approach, it is important to separately study the effect of each preservation step and mathematically describe the impact of the prevailing factors on Vitamin C stability, so as to be able to optimise the processing/storage phase. In this context, alternative mathematical approaches have been applied, including more sophisticated ones that incorporate parameter uncertainties, with the ultimate goal of providing more realistic predictions.

Effect of nonthermal treatments on selected natural food pigments and color changes in plant material

In recent years, traditional high-temperature food processing is continuously being replaced by nonthermal processes. Nonthermal processes have a positive effect on food quality, including color and maintaining natural food pigments. Thus, this article describes the influence of nonthermal, new, and traditional treatments on natural food pigments and color changes in plant materials. Characteristics of natural pigments, such as anthocyanins, betalains, carotenoids, chlorophylls, and so forth available in the plant tissue, are shortly presented. Also, the characteristics and mechanism of nonthermal processes such as pulsed electric field, ultrasound, high hydrostatic pressure, pulsed light, cold plasma, supercritical fluid extraction, and lactic acid fermentation are described. Furthermore, the disadvantages of these processes are mentioned. Each treatment is evaluated in terms of its effects on all types of natural food pigments, and the possible applications are discussed. Analysis of the latest literature showed that the use of nonthermal technologies resulted in better preservation of pigments contained in the plant tissue and improved yield of extraction. However, it is important to select the appropriate processing parameters and to optimize this process in relation to a specific type of raw material.