Thermosonication for polyphenoloxidase inactivation in fruits: Modeling the ultrasound and thermal kinetics in pear, apple and strawberry purees at different temperatures

Chemical kinetics and thermodynamics of PPO activity, colour changes and microbial degradation during blanching of the sugarcane billets

BACKGROUND

Sugarcane juice, which has a short shelf life, is a popular thirst-quenching and rejuvenating beverage worldwide. The limited shelf life is a result of changes in polyphenol oxidase (PPO) activity, total plate count (TPC) and color attributes (L*, a* and b*-values). We hypothesized that chemical kinetics and thermodynamics of blanched sugarcane cane juice causing alterations in PPO, TPC, and L, a* and b*-values will address the challenges of sugarcane juice preservation.

RESULTS

Sugarcane billets were blanched at variable time-temperature combinations in the range 0-20 min and 70-90 °C. Reaction rates increased with increasing temperature; PPO activity, TPC and colour followed first-order kinetics. PPO activity had an activation energy (Ea) of 81 kJ mol-1. The half life (t½) dropped from 16.5 to 3.47 min and decimal reduction time (D-values) dropped from 54.83 to 11.52 min. Thus reactions were temperature-sensitive. Thermodynamic studies indicated an endothermic (positive enthalpy values, ΔH > 0; 78.10 kJ mol-1) and reversible process (negative entropy values ΔS < 0; -0.044 kJmol-1 K-1). Michaeli-Menten constant (Km) and maximum velocity (Vmax) of PPO activity were determined by adding variable lemon juice concentrations in sugarcane juice. As the Km values increased (from 5.53 to 15.81 mm) and Vmax values decreased (from 666.67 to 384.61 UmL-1), a Lineweaver-Burk plot suggested decreased PPO affinity of sugarcane juice.

CONCLUSION

The results of the present study indicate that studies on chemical kinetics and thermodynamics (PPO, TPC and L, a* and b*-values) of blanched sugarcane cane juice shall mitigate challenges of sugarcane juice preservation. © 2024 Society of Chemical Industry.

Development of thermoultrasound assisted blanching to improve enzyme inactivation efficiency, drying characteristics, energy consumption, and physiochemical properties of sweet potatoes

Thermoultrasound (USB) as a promising alternative to traditional hot water (HWB) blanching was employed to blanch sweet potatoes and its influence on enzyme activity, drying behavior, energy consumption and physiochemical properties of sweet potatoes were investigated. Results showed that successive increases in blanching temperature and time resulted in significant (p < 0.05) decreases in PPO and POD activities. Compared to HWB, USB led to more effective drying by promoting texture softening, moisture diffusion, microstructure alterations, and microchannels formation, which significantly reduced energy consumption and improved the overall quality of the dried sample. Specifically, USB at 65 °C for 15 min improved water holding capacity and ABTS, while USB at 65 °C for 30 min improved color (more red and yellow), total phenolic content, total carotenoid content, and DPPH. Unfortunately, blanching process showed detrimental effects on the amino acid composition of dried samples. Overall, the development of thermoultrasound assisted blanching for sweet potatoes has the potential to revolutionize the processing and production of high-quality sweet potato products, while also improving the sustainability of food processing operations.

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.

Enzymatic browning in apple products and its inhibition treatments: A comprehensive review

Apple (Malus domestica) is widely consumed by consumers from various regions. It contains a high number of phenolic compounds (majorly hydroxybenzoic acids, hydroxycinnamic acids, flavanols, flavonols, dihydrochalcones, and anthocyanins) and antioxidant activity, which are beneficial for human health. The trends on healthy and fresh food have driven the food industry to produce minimally processed apple, such as fresh-cut, puree, juice, and so on without degrading the quality of products. Enzymatic browning is one of the problems found in minimally processed apple as it causes the undesirable dark color as well as the degradation of phenolics and antioxidant activity, which then reduces the health benefits of apple. Proper inhibition is needed to maintain the quality of minimally processed apple with minimal changes in sensory properties. This review summarizes the inhibition of enzymatic browning of apple products based on recent studies using the conventional and nonconventional processing, as well as using synthetic and natural antibrowning agents. Nonconventional processing and the use of natural antibrowning agents can be used as promising treatments to prevent enzymatic browning in minimally processed apple products. Combination of 2-3 treatments can improve the effective inhibition of enzymatic browning. Further studies, such on as other potential natural antibrowning agents and their mechanisms of action, should be conducted.

Chestnut Lily Beverage (CLB) Processing Using Ultrasound-Assisted Nisin: Microbiota Inactivation and Product Quality

We evaluated the effects of ultrasound (US) and ultrasound combined with nisin (NUS) treatments on the properties of chestnut lily beverages (CLB) using conventional thermal pasteurisation (TP) as a control. After CLB samples were treated with US and NUS for 20, 40, or 60 min, the polyphenol oxidase activity (PPO), microbial inactivation effect, colour, pH value, total phenolic content, and antioxidant capacity of the CLB were observed. It was found that the inactivation rate of PPO in CLB after NUS treatment was higher than that in the US, indicating that NUS treatment aggravated PPO inactivation. Treatment time was important in the inactivation of microorganisms by US and NUS; NUS had a lethal synergistic lethal effect on microorganisms in CLB and when compared with US, NUS reduced changes in the CLB colour value. Notably, the total phenolic content and antioxidant capacity of the US- and NUS-treated CLB significantly increased relative to the TP group. These results that suggest NUS has a potential application value in the development of CLB because it reduces the risk of microorganism contamination and helps improve the quality of CLB. This study provides technical support and a theoretical basis for the improved production of CLB.

Control of Enzymatic Browning in Strawberry, Apple, and Pear by Physical Food Preservation Methods: Comparing Ultrasound and High-Pressure Inactivation of Polyphenoloxidase

Polyphenoloxidase (PPO) enzyme can be found in fruits, vegetables and crustaceans. Its activity, promoted by oxygen, causes food browning with subsequent loss of quality and limited shelf life. Foods are pasteurized with conventional and novel physical methods to inactivate spoilage enzymes, thus avoiding the addition of unhealthy chemical preservatives. Ultrasound and high- pressure processing (HPP) are non-thermal technologies capable of retaining vitamins, bioactives and sensory components of fresh fruits. Enzyme residual activity vs. processing time were plotted for strawberry, apple, and pear purees subjected to thermosonication (1.3 W/g—71 °C), HPP-thermal (600 MPa—71 °C) and heat treatment alone at 71 °C. The PPO residual activities after treatments were highly variable. TS was the most effective for inactivating PPO, followed by thermal processing. HPP-thermal did not improve the inactivation compared with thermal treatment at 71 °C. The resistance of the three fruits’ PPOs exhibited the same pattern for the three technologies: pear PPO was the most resistant enzyme, followed by apple PPO and, lastly, strawberry PPO. However, the resistance of the three PPOs to TS was lower and very similar. Given the huge variability of PPO resistance, it is important to run inactivation tests for different fruits/cultivars. The results can assist manufacturers to avoid browning during processing, storage and distribution of fruit purees, juices and concentrates.

Combined effect of Bacillus siamensis and chlorogenic acid on maintenance of quality, control of disease in stored wax apple fruit

Objectives

The purpose of this study was to evaluate the effect of combined postharvest use of Bacillus siamensis strain and chlorogenic acid on quality mainteance and disease control in wax apple fruit.

Materials and Methods

Wax apple fruit were treated with Bacillus siamensis strain (N1), chlorogenic acid (CHA) and N1+CHA and preserved at 25℃for 12 days. The appearance and quality parameters were evaluated, along with the disease index (DI), content of total soluble solids (TSS), total acid (TA), vitamin C (Vc), total phenolic, and flavonoids during cold storage. Meanwhile, the activities of β-1,3-glucanase (GLU) , phenylalanine ammonialyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) were determined. Furthermore, the transcriptome and the expression level of key defense enzyme genes were analyzed by RNA-seq and real-time quantitative reverse transcription PCR (qRT-PCR).

Results

N1+CHA treatment significantly lowered DI and delayed fruit quality deterioration by slowing TSS and TA loss and enhancing antioxidant capacity, including Vc, total phenolic, and flavonoids content. Meanwhile, the activities of GLU, PAL, PPO and POD were dramatically increased by N1+CHA treatment. Additionally, N1+CHA treatment modulated several metabolic pathways, including those involved in plant-hormone signal transduction and plant-pathogen interaction. The expression level of key defense enzyme genes were significantly up-regulated in stored wax apple fruit by the N1+CHA treatment, which were well coincided with the transcriptome data.

Conclusion

The combined use of N1+CHA significantly prevent disease and maintain fruit quality of wax apple during storage. These findings indicate that it could serve as a promising biological technique for preserving wax apple fruit.

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.

Effect of Ultrasound on the Activity of Mushroom (Agaricus bisporous) Polyphenol Oxidase and Observation of Structural Changes Using Time-resolved Fluorescence

Polyphenol oxidase (PPO) is an enzyme associated with the browning process that can occur from mechanical injury and postharvest storage. Thus, its inactivation to inhibit this process is of great interest to the food industry. Recently a nonthermal technology, high frequency ultrasound (100–1 MHz), has found usage in this aspect. In this work, the application of high-frequency (378 kHz, 583 kHz, 1144 kHz, and 1175 kHz) and low frequency (20 kHz) treatment on a PPO extract (from mushrooms) by monitoring the residual enzymatic activity is described. A control thermal treatment at 40 °C was also performed for comparison purposes. High-frequency inactivation data fitted well using the Weibull model, whereas those obtained upon low frequency followed first-order kinetics. The inactivation rate constant obtained ranged from 0.0054 (20 kHz) to 0.028 min−1 (at 583 kHz). To elucidate changes in the enzyme structure time-resolved spectroscopy of a commercial PPO enzyme model was employed. Results indicated that ultrasound-induced structural changes in PPO, in keeping with the activity behaviour upon sonication.

Thermal, High Pressure, and Ultrasound Inactivation of Various Fruit Cultivars’ Polyphenol Oxidase: Kinetic Inactivation Models and Estimation of Treatment Energy Requirement

Polyphenol oxidase (PPO) catalyses the browning reaction during fruit processing and storage. It is considered a threat to clean labels and minimally processed fruit products. Unwanted changes in fruits’ appearance and quality represent a cost to the industry. High pressure and ultrasound, in addition to thermal treatment, are effective in reducing PPO activity and producing high-quality products. PPO from different fruit cultivars behaves differently when submitted to different treatments. A systematic review was conducted, where treatment parameters, PPO inactivation data (≥80% inactivation), and kinetic inactivation parameters (rate constant (k), activation energy (Ea), D-value, and z-value) by different treatments were collected. Additionally, the estimated energy requirements for the inactivation of PPO (≥80%) by different treatments were calculated and compared. Resistance to various treatments varies between fruit cultivars. For the same temperature, the inactivation of PPO by ultrasound combined with heat is more effective than thermal treatment alone, and the high pressure combined thermal process. The majority of the thermal, HPP, and ultrasound inactivation of PPO in fruits followed first-order behaviour. Some fruit cultivars, however, showed biphasic inactivation behaviour. The estimated specific energy requirements calculated based on the mass of processed fruit sample to inactivate ≥80% polyphenol oxidase for the thermal process was 87 to 255 kJ/kg, while for high pressure processing it was 139 to 269 kJ/kg and for ultrasound it was 780 to 10,814 kJ/kg.

Application of High-Intensity Ultrasound to Improve Food Processing Efficiency: A Review

The use of non-thermal processing technologies has grown in response to an ever-increasing demand for high-quality, convenient meals with natural taste and flavour that are free of chemical additions and preservatives. Food processing plays a crucial role in addressing food security issues by reducing loss and controlling spoilage. Among the several non-thermal processing methods, ultrasound technology has shown to be very beneficial. Ultrasound processing, whether used alone or in combination with other methods, improves food quality significantly and is thus considered beneficial. Cutting, freezing, drying, homogenization, foaming and defoaming, filtration, emulsification, and extraction are just a few of the applications for ultrasound in the food business. Ultrasounds can be used to destroy germs and inactivate enzymes without affecting the quality of the food. As a result, ultrasonography is being hailed as a game-changing processing technique for reducing organoleptic and nutritional waste. This review intends to investigate the underlying principles of ultrasonic generation and to improve understanding of their applications in food processing to make ultrasonic generation a safe, viable, and innovative food processing technology, as well as investigate the technology's benefits and downsides. The breadth of ultrasound's application in the industry has also been examined. This will also help researchers and the food sector develop more efficient strategies for frequency-controlled power ultrasound in food processing applications.

Emerging Non-Thermal Technologies as Alternative to SO2 for the Production of Wine

SO₂ is an antioxidant and selective antimicrobial additive, inhibiting the growth of molds in the must during the early stages of wine production, as well as undesirable bacteria and yeasts during fermentation, thus avoiding microbial spoilage during wine production and storage. The addition of SO₂ is regulated to a maximum of 150–350 ppm, as this chemical preservative can cause adverse effects in consumers such as allergic reactions. Therefore, the wine industry is interested in finding alternative strategies to reduce SO₂ levels, while maintaining wine quality. The use of non-thermal or cold pasteurization technologies for wine preservation was reviewed. The effect of pulsed electric fields (PEF), high pressure processing (HPP), power ultrasound (US), ultraviolet irradiation (UV), high pressure homogenization (HPH), filtration and low electric current (LEC) on wine quality and microbial inactivation was explored and the technologies were compared. PEF and HPP proved to be effective wine pasteurization technologies as they inactivate key wine spoilage yeasts, including Brettanomyces, and bacteria in short periods of time, while retaining the characteristic flavor and aroma of the wine produced. PEF is a promising technology for the beverage industry as it is a continuous process, requiring only microseconds of processing time for the inactivation of undesirable microbes in wines, with commercial scale, higher throughput production potential.

Aplicação do ultrassom no processamento de frutas e hortaliças

Resumo Este trabalho objetivou apresentar aspectos relacionados à utilização do ultrassom no processamento de frutas e hortaliças, como o funcionamento do método, os efeitos no alimento, as aplicações, os aspectos sensoriais e a percepção dos consumidores. As mudanças dos hábitos alimentares e a busca do bem-estar refletem no aumento da procura por alimentos naturais, como as frutas e as hortaliças. Estes alimentos podem sofrer alterações microbiológicas ao longo da cadeia produtiva, sendo necessária a aplicação de boas práticas agrícolas e de manipulação, e processos tecnológicos de conservação para a garantia da qualidade do produto. O ultrassom é uma tecnologia emergente aplicada no processamento de frutas e hortaliças que está relacionada a melhorias na qualidade e preservação. O princípio básico do ultrassom é a cavitação acústica, que envolve o crescimento e colapso de bolhas durante períodos de rarefação e compressão, causando alterações químicas, físicas e mecânicas no alimento. Essas alterações estão relacionadas à inativação de micro-organismos e de enzimas, à remoção de resíduos e às melhorias na qualidade físico-química, e à acessibilidade de compostos bioativos. Além disso, a aplicação deste método pode ter boa aceitabilidade pelos consumidores, que procuram alimentos mais naturais e submetidos a processos que não causem impacto ambiental.

Tri-frequency ultrasound as pretreatment to infrared drying of carrots: impact on enzyme inactivation, color changes, nutrition quality parameters and microstructures

The effects of tri-frequency ultrasound as pretreatment on the peroxidase (POD) inactivation and infrared drying attributes of carrots were studied in the temperature range of 60–80 °C. Thermosonication (TS) treatment reduced 65.21, 73.33 and 81.43% POD activity after 5 min for the temperatures at 60, 70 and 80 °C, respectively, which were all higher than hot water (HW) blanching treated samples. The first-order kinetics fitted well for the POD inactivation curves. Similar retention ranges of vitamin C (VC) were observed after TS (88.41–82.51%) and HW (91.91–88.75%) treatments at the studied range of temperatures. Compared to HW treated samples, drying times of thermosonicated carrot slices were shortened by 13.6, 15 and 15.8% for blanching temperatures at 60, 70 and 80 °C, respectively. The aid of ultrasound showed a positive effect on the rehydration ration (RR) of samples. Sonicated dried samples exhibited higher hardness compared with thermal dried samples. No significant variation (p > 0.05) in the total color difference (ΔE) was attained for dried carrot slices pretreated by TS and HW processes.

Ultrasonication and thermosonication blanching treatments of carrot at varying frequencies: Effects on peroxidase inactivation mechanisms and quality characterization evaluation

The effects of ultrasonication (US) and thermosonication (TS) blanching at varying frequencies on the carrot peroxidase (POD) inactivation and potential mechanisms were studied. The physicochemical properties were evaluated. Hot water (HW) blanching was used as control. Thermosonication decreased the POD activity to a greater extent, with a dual-frequency of 22/40 kHz showing the most significant effect. The POD-related gene expression was down-regulated by TS, which was contrary to the thermally treated samples. Electron paramagnetic resonance (EPR) spectra revealed that ultrasound-induced radicals from water sonolysis might involve in the POD inactivation. Thermosonication substantially increased the total carotenoid content (TCC). The color analysis showed that thermosonicated samples with a dual-frequency (22/40 kHz) exhibited the maximum values of C* and ΔE, and the minimum value of the whiteness index (WI). The micrographs verified the alterations in TCC and relative electrolyte leakage (REL) of carrot treated by HW, US, and TS.

The effect of high-power ultrasound on the rheological properties of strawberry pulp

This study investigated the effects of high-power ultrasound (HPU, 0-45 °C, 242-968 W/cm², 2-16 min) on the rheological properties of strawberry pulp. Following the HPU treatment, the strawberry pulp exhibited an increase in apparent viscosity, storage modulus (G'), and loss modulus (G″). The water-soluble pectin (WSP), pectin methylesterase (PME) activity, and free calcium ions (Ca²⁺) of the strawberry pulp after HPU treatment were investigated to determine a possible reason for this phenomenon. HPU caused a significant decrease in the degree of esterification (DE), molecular weight (Mw), and particle size of strawberry WSP, but no significant changes were evident in the galacturonic acid (GalA) content and the zeta (ζ)-potential (P > 0.05), resulting in decrease in the apparent viscosity. Moreover, the largest reduction of PME activity was 22.6% after HPU treatment at 605 W/cm² and 45 °C for 16 min, indicating that the PME was resistant to the HPU treatments. The free Ca²⁺ content in the strawberry pulp was significantly decreased after exposure to HPU (P < 0.05). The maximal reduction of 52.01% in the free Ca²⁺ was achieved at 605 W/cm² and 45 °C for 16 min. The overall results indicated that the high residual activity (RA) of PME after HPU might induce the low esterification of WSP, while HPU promoted the interaction of free Ca²⁺ and low-methylated pectin, to form the network structure of Ca²⁺-low-methylated pectin, resulting in an increase in viscosity in the complex strawberry system.

Antibrowning effect of commercial and acid-heat coagulated whey on potatoes during refrigerated storage

Potato color turns to brown after some process such as peeling, cutting, and slicing. In this research, the effect of acid-heat coagulated whey and commercial whey solutions on the color, polyphenol oxidase, phenylalanine ammonia-lyase activity, malondialdehyde, hydrogen peroxide content of potatoes were compared with pure water (control) immersion and sodium hydrogen sulfide solution. According to color results, there was no significant (P > 0.05) difference was found in the L^* and b^* values, browning index, and whitening index of the treatment groups. The polyphenol oxidase activity of the sulfide and commercial whey solution groups decreased from the initial values on day 3 then increased over that value. The use of the whey solution in preventing polyphenol oxidase activity showed a similar curve with the use of the sulfide solution. A rapid increase was observed in the malondialdehyde and hydrogen peroxide values of all treatment groups during the first 3-day storage. PRACTICAL APPLICATION: Immersion of potato cubes to whey protein solution prevents the browning and inhibits polyphenol oxidase activity. The browning index of the samples was not affected by the immersing water or whey solutions.

Influence of high-intensity ultrasound on color, chemical composition and antioxidant properties of araçá-boi pulp

In this study, we evaluated the influence of the ultrasound application on five levels of energy density (1000; 3000; 5000 and 7000 J g^-1) compared to two pasteurization techniques (70 °C/5 min and 94 °C/0.5 min) on color parameters, polyphenoloxidase activity, chemical composition, and antioxidant properties of araçá-boi pulp. Ultrasound caused changes in the parameters brightness/darkness, hue angle, and total color difference, but did not change chroma, yellowness/blueness, color index, and yellow index. Moreover, this technique was efficient for inactivating polyphenoloxidase. Ultrasound at 7000 J g^-1 was responsible for an increase in soluble solids (16%), vitamin C (46.5%), phenolics (15.65%), flavonoids (50%) and antioxidant capacity in relation to untreated pulp, while ultrasound at 5000 J g^-1 increased the relative intensity of compounds of biological interest. Thus, ultrasound can be considered as a promising technique to maintain the shelf life, without drastically affecting the nutritional and functional qualities of this fruit.

Application of ultrasound technology in processing of ready-to-eat fresh food: A review

With the increase in food standardization and the pace of modern life, the demand for ready-to-eat foods is growing. The strong processing conditions of traditional technology often accelerate the rate of deterioration of quality, and microbes are the safety hazard of ready-to-eat foods. Ultrasound technology is an environmentally friendly technology that hardly causes thermal damage to raw materials. In this paper, the ultrasound technology is used in the disinfection, sterilization, enzyme inactivation, desensitization, dehydration, curing, tenderization and cooking process of fresh food from the perspective of microbial safety and quality of fresh food. The cavitation effect of ultrasound can improve the mass transfer rate of infiltration processes such as dehydration and curing, promote the oxidation of lipids and proteins for enrich the flavor of meat products, improve the microbiological safety and reduce the sensitization by destroying the integrity of the microbial cells and the conformation of the protein. In addition, ultrasound as an auxiliary processing technology can reduce the damage of traditional production technology to reserve the quality and nutritional value of food. Ultrasound has proved to be an efficient and green processing technology for ready-to-eat food.

Application of non-thermal pretreatment techniques on agricultural products prior to drying: a review

BACKGROUND

Most agricultural crops contain high moisture content (80-95% wet basis (wb)) which makes them very susceptible to microbial damage leading to shorter shelf-life and high postharvest losses. The high perishability of these agricultural products requires preservation techniques to prolong their shelf-lives. Drying remains an important component of processing in this regard. Therefore, any pretreatment methods for drying agricultural product that decreases the moisture content and minimizes drying time by conserving the quality of the crop product is of prime significance. This article is a comprehensive review of recent developments of non-thermal pretreatment (NTP) methods. A summary of their significance, emerging and innovative methods of this technology together with its applications and limitations are discussed. This article further examines the environmental impact of NTP techniques.

RESULTS

NTP techniques, such as high pressure, ultrasound, pulsed electric field and osmotic dehydration methods are essential operations for pre-dehydration of agricultural products prior to drying. These techniques can avoid the deleterious effects of heat on nutritive value, colour and flavour of agricultural products compared to thermal pretreatments. They also enhance the inactivation of the enzymes, improve energy efficiency and mass transfer, reduce processing time, preserve bioactive compounds, improve drying kinetics and drying rate, minimize enzymatic browning, and enhance product quality.

CONCLUSION

These findings will provide a better understanding of different NTP methods and also make available more information for selecting pretreatment techniques for drying of agricultural products. © 2020 Society of Chemical Industry.

Effects of high hydrostatic pressure on the microbial inactivation and extraction of bioactive compounds from açaí (Euterpe oleracea Martius) pulp

The aim of this study was to investigate the effects of high hydrostatic pressure (HHP) on the inactivation of Lactobacillus fructivorans, on the inactivation of Alicyclobacillus acidoterrestris spores and on the extraction of anthocyanins and total phenolics from açaí pulp. The tested conditions comprised pressures of 400-600 MPa, treatment times of 5-15 min, and temperatures of 25 °C and 65 °C. Results were compared to those of conventional thermal treatments (85 °C/1 min). Regarding A. acidoterrestris spores, applying HHP for 13.5 min, resulted in a value of four-decimal reduction. L. fructivorans presented considerable sensitivity to HHP treatment, achieving inactivation rates above 6.7 log cycles at process conditions at 600 MPa and 65 °C for 5 min. All samples of açaí pulp processed showed absence of thermotolerant coliforms during the 28 days of refrigerated storage (shelf life study). The açaí pulps processed by HHP (600 MPa/5 min/25 °C) had anthocyanin extraction increased by 37% on average. In contrast, conventional thermal treatment reduced anthocyanin content by 16.3%. For phenolic compounds, the process at 600 MPa/5 min/65 °C increases extraction by 10.25%. A combination of HHP treatment and moderate heat (65 °C) was shown to be an alternative to thermal pasteurization, leading to microbiologically safe products while preserving functional compounds.

Emergence and era of ultrasonic's in fruit juice preservation: A review

Ultrasonic's has emerged to an unconditional extent in the last decade. It has found its application in fruit juice and beverage industry due to its multifunctional desired effects. The technology is inexpensive, simple, reliable, and environmentally friendly and highly effective in the preservation of juices with enhanced quality attributes. This review will enlighten your knowledge in understanding the basic concept of ultrasonic's with the principle, mechanism, and application in the food sector. It specifically reviews the explored effect of ultrasonication on different juices. It explores the influence of technology in enzyme inactivation, microbial inactivation and different quality attributes of fruit juices. It gives you an in-depth insight into the technology.

Effects of ultrasound, osmotic dehydration, and osmosonication pretreatments on bioactive compounds, chemical characterization, enzyme inactivation, color, and antioxidant activity of dried ginger slices

The effect of ultrasound (US), osmotic dehydration (OD), and osmosonication (OS) pretreatments on total phenolic content (TPC), total flavonoids content, (TFC), phytochemical constituents (gingerol derivatives and diarylheptanoids), polyphenol oxidase (PPO), peroxidase (POD), 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), cupric ion reducing capacity (CUPRAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power capacity (FRAP), and color of ginger slices dried under relative humidity convective dryer was investigated. OS pretreatment improved the preservation of TPC (13.80-34.79 mg GAE/g d.w), TFC (26.46-62.16 mg CE/g d.w), ABTS (30.37%-86.10%), CUPRAC (36.89-73.97 mg/g), DPPH (50.57%-92.60%), FRAP (26.44-83 mg/g), and phytochemical constituents than US and OD. The OS-treated sample was more effective in inactivating both PPO (12.09%-35.93%) and POD (16.21%-39.58%) enzymes compared to US and OD-treated samples. However, US pretreatment retained the color quality of dried ginger slices than the OS and OD treatments. OS pretreatment (5.43) also increased the total color change (ΔE) of the dried ginger samples compared to US (2.81) and OD (4.60). PRACTICAL APPLICATIONS: Ginger is commonly used in the food, beverage, and pharmaceutical industries owing to their distinctive flavor and various health potentials. However, its high moisture content makes its inappropriate for long-term storage which results in its high perishability. Drying is one of the most common techniques to prolong its shelf life. Hence, any pretreatment for ginger that reduces the moistures content and lessens the drying time by preserving the quality of the crop is of vital importance. Ultrasound, osmotic dehydration, and osmosonication are novel pretreatment techniques that are widely used prior to drying of various agricultural products due to its numerous advantages over conventional methods. Its application in drying of foods could help shorten the drying time, reduce processing costs, improve energy consumption and efficiency, and preserve the physical and nutritional properties of the dried product. The current findings will also offer more information for selecting pretreatment techniques for ginger drying.

Comparative transcriptome analysis reveals fruit discoloration mechanisms in postharvest strawberries in response to high ambient temperature

The aim of this study was to examine both physiological and molecular evidences related to fruit discoloration in postharvest strawberries under high ambient temperature. The results showed the total anthocyanin and their main components in the strawberries under 35 °C were greatly increased due to the significant up-regulations of anthocyanin biosynthetic genes and transportation genes. High ambient temperature greatly improved the activities of peroxidase (POD) and enhanced gene expressions of POD3, POD6 and POD63. At the same time, high storage temperature activated laccase genes expression including laccase-9 and laccase-14, which was closely related to anthocyanin degradation. Levels of reactive oxygen species (ROS) metabolism were also increased under high ambient temperature at transcript levels. Therefore, we concluded that high ambient temperature could enhance anthocyanin accumulation and degradation at the same time, which maybe the main reasons for the fruits discoloration of postharvest strawberries under high ambient temperature.

Optimization of thermosonication conditions for cloudy strawberry nectar with using of critical quality parameters

The optimum thermosonication parameters, temperature and ultrasound energy density (UED), determined by using response surface methodology to inactivate polyphenol oxidase (PPO) and protecting the quality parameters, especially color of strawberry nectar. The PPO inactivation was successfully achieved by thermosonication treatment. Increasing of temperature resulted with decreasing of browning index and increasing of hydroxymethyl furfural. High temperature-low UED combination can be applied to obtain minimum change in ΔE^∗ and maximum protection of ascorbic acid. Thermosonication at mild temperature (∼50 °C) and UED (∼230 J/g) ensured the maximum levels of total monomeric anthocyanin and total phenolic content. The combination of 59 °C and 455 J/g was the conditions of optimum thermosonication to minimize quality parameters which cause undesirable changes like color degradation in nectar and maximize desirable ones which have beneficial effects on characteristics of nectar or on human health like phenolic content of nectar.