Ohmic heating and pulsed vacuum effect on dehydration processes and polyphenol component retention of osmodehydrated blueberries (cv. Tifblue)

Recent advances in vacuum impregnation of fruits and vegetables processing: A concise review

Vacuum impregnation (VI) is a novel, non-thermal treatment that aims to modify the composition of food material by partially removing water and air and impregnating it with physiologically active compounds without affecting the structural integrity of food matrix. Application of VI accelerates the mass transfer processes, which leads to few changes in food composition and improves dehydration. Large volumes in intracellular spaces of fruit and vegetable tissues make it suitable to introduce different agents like nutrients, cryoprotectants, browning inhibitors, enzymes, and chemicals; enhancing texture profile and inhibiting tissue softening, or compounds lowering water activity and pH. water activity Thus, the VI may help to achieve new product quality associated with physicochemical features and sensory attributes. This review highlights the evolution and mechanism of VI technique, major factors affecting VI of fruits and vegetables and their responses to processing, and industrial relevance. Vacuum impregnation consists ability to revolutionize various aspects of food processing and preservation. VI serves as a versatile tool that enhances the quality, shelf life, and nutritional content of processed fruits and vegetables. It offers unique advantages of altering product composition by introducing desired compounds while preserving structural integrity. VI improves mass transfer processes, reduces water content, enhances the absorption of nutrients, antioxidants, and preservatives. This technology finds application in producing fortified foods, extending shelf life, and creating innovative products with improved sensory attributes. VI's ability to efficiently impregnate substances into porous materials, combined with its energy-saving potential and compatibility with other processing methods, makes it a valuable tool in the food industry. As consumers demand healthier and long-lasting products, VI emerges as a promising solution for meeting market demands.

Development and investigation of ultrasound-assisted pulsed ohmic heating for inactivation of foodborne pathogens in milk with different fat content

The central objective of this research was to develop an ultrasound-assisted pulsed ohmic heating (POH) system for inactivation of food-borne pathogens in phosphate buffered saline (PBS) and milk with 0-3.6% fat and investigate its bactericidal effect. Combining ultrasound with POH did not significantly affect the temperature profile of samples. Both POH alone and ultrasound-assisted POH took 120 s to heat PBS 60℃. Milk with 0, 1, and 3.6% fat was heated to 60℃ by POH alone and ultrasound-assisted POH after 335, 475, and 525 s, respectively. This is because the electrical conductivity of the samples was the same for POH alone and ultrasound-assisted POH. Despite identical temperature profiles, ultrasound-assisted POH exerted a synergistic effect on the reduction of Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus. In particular, the inactivation level of S. Typhimurium in PBS subjected to ultrasound-assisted POH treatment for 120 s corresponding to a treatment temperature of 60℃ was 3.73 log units higher than the sum of each treatment alone. A propidium iodide assay, intracellular protein measurements, and scanning electron microscopy revealed that ultrasound-assisted POH treatment provoked lethal cell membrane damage and leakage of intracellular proteins. Meanwhile, fat in milk reduced the efficacy of the bacterial inactivation of the ultrasound-assisted POH system due to its low electrical conductivity and sonoprotective effect. After ultrasound-assisted POH treatment at 60℃, there were no significant differences (P > 0.05) in the pH, color, and apparent viscosity of milk between the untreated and treated group.

Application of novel pretreatment technologies for intensification of drying performance and quality attributes of food commodities: a review

Drying is an energy-intensive process that can be reduced by the application of pretreatment prior to drying to enhance mass transfer and minimize energy consumption. This review summarizes the mechanistic aspects and applications of emerging pretreatment approaches, namely ohmic heating (OH), ultrasound (US), high pressure processing (HPP), and pulsed electric field (PEF), with emphasis on the enhancement of mass transfer and quality attributes of foods. Novel pretreatments significantly improved the drying efficiency by increasing mass transfer, cavitation, and microchannel formation within the cell structure. Various processing parameters have great influence on the drying performance and quality attributes of foods. Several studies have shown that novel pretreatments (individual and combined) can significantly save energy while improving the overall drying performance and retaining the quality attributes. This work would be useful for understanding the mechanisms of novel pretreatment technologies and their applications for future commercial research and development activities.

Processing of Enriched Pear Slices with Blueberry Juice: Phenolics, Antioxidant, and Color Characteristics

This study evaluated the effectiveness of phenolic compound incorporation from blueberry juice into pear slices (PS) using a combination of ohmic heating (OH) and vacuum impregnation (VI), followed by air-drying (AD) or freeze-drying (FD). Our results showed that OH increased the content of bioactive compounds and antioxidant capacity of blueberry juice, with the optimal OH condition set at 50 °C for 20 min under an electric field of 13 V·cm^-1. Furthermore, the combination of VI and OH was efficient in enriching PS with bioactive compounds from blueberry juice (such as cyanidin and epigallocatechin), with the optimal VI/OH condition set at 50 °C for 90 min under an electric field of 7.8 V·cm^-1. Moreover, anthocyanin pigments from blueberry juice affected the color parameters of PS by increasing the a* parameter and decreasing the b* and L* parameters. However, both FD and AD (at 40, 50, and 60 °C) negatively affected (p ≤ 0.05) the phenolic content and antioxidant capacity. Notably, AD at 60 °C showed the highest levels of phenolic compounds and antioxidant potential for both impregnated and non-impregnated PS.

Efficient thermal treatment of radish (Raphanus sativus) for enhancing its bioactive compounds

Old preserved radish (OPR), a traditional pickled-food of Asia, contains the healthy bioactive compounds, such as phenols and flavonoids. To preserve the phenols levels in radish by thermal treatment, which are decreased due to the polyphenol oxidase activity during long storage. Range of thermal processing evaluated to retain the maximum phenols level in the radish while processed at temperatures of 70 °C, 80 °C and 90 °C for 30 days. In this study, the bioactive compounds and antioxidant activity of thermal processing radish (TPR) were evaluated and compared with commercial products of OPR. Results showed the best condition of thermal processing, 80°C for 30 days, could increase the values of phenols, flavonoids and antioxidant activity that were 2.27, 2.74 and 2.89 times, respectively. When comparing the thermally processed radish or TPR with OPR, TPR has a higher content of phenols and flavonoids, indicating that the thermal processing was effective to increase the content of functional compounds in radish and significantly improved its nutritional values.

The Impact of Different Pretreatment Processes (Freezing, Ultrasound and High Pressure) on the Sensory and Functional Properties of Black Garlic (Allium sativum L.)

Black garlic (BG) is an emerging derivative of fresh garlic with enhanced nutritional properties. This study aimed to develop functional BG products with good consumer acceptance. To this end, BG was treated with freezing (F-BG), ultrasound (U-BG), and HHP (H-BG) to assess its sensory and functional properties. The results showed that F-BG and H-BG had higher S-allyl-cysteine (SAC), polyphenol, and flavonoid contents than BG. H-BG and F-BG displayed the best sensory quality after 18 days of aging, while 5-hydroxymethylfurfural (5-HMF), SAC, and polyphenols were identified as the most influential sensory parameters. Moreover, the F-BG and H-BG groups achieved optimal taste after 18 days, as opposed to untreated BG, which needed more than 24 days. Therefore, the proposed approaches significantly reduced the processing time while enhancing the physical, sensory, and functional properties of BG. In conclusion, freezing and HHP techniques may be considered promising pretreatments to develop BG products with good functional and sensory properties.

Advanced osmotic dehydration techniques combined with emerging drying methods for sustainable food production: Impact on bioactive components, texture, color, and sensory properties of food

The food industries are looking for potential preservation methods for fruits and vegetables. The combination of osmosis and drying has proved the efficient method to improve the food quality. Osmotic dehydration is a mass transfer process in which water molecules from the food move to an osmo-active solution and the solutes from the solution migrate into the food. Advanced osmotic dehydration techniques such as electric field pulse treatment, ultrasonic and microwave-assisted dehydration, pulsed vacuum, and osmodehydrofreezing can improve the nutritional quality (bioactive) and sensory properties (color, texture, aroma, flavor) of fresh and cut-fruits without changing their reliability. Emerging osmotic dehydration technologies can preserve the structure of fruit tissue by forming microscopic channels and increasing effective water diffusivity. However, it is important to analyze the effect of advanced osmotic dehydration techniques on the quality of food products to understand the industrial scalability of these techniques. The present paper discusses the impact of recent osmotic dehydration techniques on bioactive, antioxidant capacity, color, and sensory profile of food.

Sustainable food processing of selected North American native berries to support agroforestry

Chokeberries, elderberries, blueberries, and blackberries are highly nutritious native fruits in the US Midwest region. Their high moisture content, delicate structure easily leads to fruit loss/waste. This review focuses on different drying methods for whole fruits and juices to preserve their quality and improve their shelf life. Solar drying, hot-air drying, spray drying, freeze-drying, vacuum-drying, electromagnetic drying, and osmotic dehydration are the commonly used dehydrating methods for berries. Berries are photo, heat-sensitive, and rich source of essential nutrients. Texture, flavor, color, water content, phytonutrients, physicochemical properties can be influenced by dryer and processing parameter selection. Drying is a complex dynamic process, due to structural differences among various foods, combined thermal and non-thermal techniques could improve fruit quality. Hence, knowledge of drying behavior and degradation kinetics is vital for optimizing the process parameters to enhance the fruit quality. Freeze drying and spray drying showed better preservation of nutrients. Existing research suggests that chokeberries (Aronia) are underutilized compared to blueberries and blackberries. Aronia fruit has a lot of potentials containing health-promoting compounds and is yet to be explored. Future research suggestions have been put forward for the efficient use of drying techniques and to improve the fruit quality.

Osmotic dehydration: More than water loss and solid gain

The immersion of food in a hypertonic solution results in an osmotic dehydration process (OD) with the loss of water (WL) from the food to the solution and the gain of solids from the solution (SG) by the food. For this reason, OD is commonly used to produce semi-dehydrated or enriched foods by incorporation. Although the most of OD studies are focused on the WL and SG processes, many publications addresses the physicochemical and nutritional changes resulting from OD in the food matrix and in the osmotic solution. Such changes must be handled in order to improve the quality of the product. This work is a compilation of publications with this approach.

Currently Applied Extraction Processes for Secondary Metabolites from Lippia turbinata and Turnera diffusa and Future Perspectives

The poleo (Lippia turbinata Griseb.) and damiana (Turnera diffusa Wild) are two of the most valued species in the Mexican semidesert due to their medicinal uses. The conventional essential oil extraction process is hydrodistillation, and for the extraction of antioxidants, the use of organic solvents. However, these techniques are time-consuming and degrade thermolabile molecules, and the efficiency of the process is dependent on the affinity of the solvent for bioactive compounds. Likewise, they generate solvent residues such as methanol, hexane, petroleum ether, toluene, chloroform, etc. Therefore, in recent years, ecofriendly alternatives such as ohmic heating, microwaves, ultrasound, and supercritical fluids have been studied. These methodologies allow reducing the environmental impact and processing times, in addition to increasing yields at a lower cost. Currently, there is no up-to-date information that provides a description of the ecofriendly trends for the recovery process of essential oils and antioxidants from Lippia turbinata and Turnera diffusa. This review includes relevant information on the most recent advancements in these processes, including conditions and methodological foundation.

Thermal treatment enhances the α-glucosidase inhibitory activity of bitter melon (Momordica charantia) by increasing the free form of phenolic compounds and the contents of Maillard reaction products

Inhibition of α-glucosidase can slow carbohydrate metabolism, which is known as an effective strategy for diabetes treatment. The aim of this study is to evaluate the effect of thermal treatment (50, 60, and 70℃) for 15 days on the α-glucosidase inhibitory activity of bitter melon. The results show that the bitter melon heated at 70℃ for 12 days had the best α-glucosidase inhibitory effect. However, the amount of free polyphenols, 5-hydroxymethyl-2-furfural (5-HMF), and the browning degree of bitter melon generally increased with the time (15 days) and temperature of the thermal treatment, which is positively related to their antioxidant and α-glucosidase inhibitory activities. In conclusion, aged bitter melon shows great α-glucosidase inhibitory activity, which may be related to the increased free form of the involved phenolic compounds and Maillard reaction products. This suggests that thermal processing may be a good way to enhance the application of bitter melon for diabetes treatment. PRACTICAL APPLICATION: The thermal processing of bitter melon provides an application for diabetes treatment. This study demonstrated that heat-treated bitter melon can lower the blood glucose level; therefore, it can be used as a potential anti-hyperglycemic and functional food.

Increase of mass transfer rates during osmotic dehydration of apples by application of moderate electric field

Osmotic dehydration (OD) is a drying process that consists in placing the food in contact with concentrated solutions of soluble solids to reduce its water activity. The use of moderate electric field (MEF) may promote increase of the mass transfer rates due to the non-thermal effects of electroporation and permeabilization of the cells. In this context, the objective of this study was to investigate the mass transfer process kinetics during apples OD assisted by MEF, evaluating the non-thermal effects of this emerging technology. The experiments were conducted with sucrose solutions (40, 50 and 60%, m/m) at 40 °C. Samples were submitted to electrical field strength (0, 5.5 and 11.0 Vcm−1), according to an experimental design. Results indicated that the application of MEF favoured water loss and solid gain. The effective mass diffusivities of water and solids increased as voltage applied increases. Moreover, MEF negatively influenced color and reducing capacity of the samples.

Changes in unfrozen water content and dielectric properties during pulse vacuum osmotic dehydration to improve microwave freeze-drying characteristics of Chinese yam

BACKGROUND

As a pretreatment before drying, the purpose of osmotic dehydration (OD) is to reduce the initial water content of samples and shorten the drying time. When OD is combined with pulse vacuum, the mass transfer is enhanced. Furthermore, the properties of materials, which affect the absorption and dissipation of microwaves, can be changed by OD. In this work, pulsed vacuum osmotic dehydration (PVOD) with sucrose solution was adopted before microwave freeze-drying (MFD). The effects of PVOD on the drying characteristics and quality of dried products were studied.

RESULTS

Results showed that the unfrozen water content was increased by PVOD, which made the dielectric constant and loss factor of Chinese yam larger than that of untreated samples, and the difference amplified with the increasing temperature. Thus, the shortened drying time (up to 38.5%) and increased average drying rate (up to 16.8%) were achieved by MFD combined with PVOD. While in traditional freeze-drying, PVOD resulted in slightly shortened drying time but decreased drying rate. The mechanism of PVOD on improving drying rate of MFD was analyzed from the perspective of unfrozen water content and dielectric properties. Furthermore, the quality assessments indicated that PVOD treatment retained a better color and improved the total phenolic content of dried yams compared to untreated and dried samples.

CONCLUSION

PVOD using sucrose solution was an effective method to change the characteristics of yam, enhancing the MFD rate and improving the product qualities. © 2019 Society of Chemical Industry.

Innovative technologies for producing and preserving intermediate moisture foods: A review

Intermediate moisture foods (IMF) or semi-dried foods (SDF) have gained more attention worldwide having features very similar to fresh food products, but with a longer shelf life. This review presents the recent developments in novel technologies and methods for the production and preservation of IMF. These include new drying methods, using agents to reduce water-activity, innovative osmotic dehydration technologies, electro-osmotic dewatering, thermal pasteurization, plasma treatments (PT), high pressure processing (HPP), modified atmosphere packaging (MAP), edible coating, active packaging (and energy efficiency, improve quality and extend the shelf life of the final food AP) and hurdle technologies (HT). Innovative methods applied to producing and preserving IMF can enhance both drying products. Yet more systematic research is still needed to bridge knowledge gaps, in particular on inactivation kinetics and mechanisms related to thermal and non-thermal pasteurization technologies for control of pathogens and spoilage micro-organisms in IMF.

Enrichment of Apple Slices with Bioactive Compounds from Pomegranate Cryoconcentrated Juice as an Osmodehydration Agent

Pomegranate juice is an important source of bioactive compounds, and cryoconcentrated juice is an interesting osmodehydration agent to enrich a vegetal matrix. This investigation aimed to incorporate bioactive compounds from pomegranate cryoconcentrated juice into apple slices using osmodehydration (OD) assisted by pulse vacuum (PV) and ohmic heating (OH). The apple slices (3 × 4 × 0.5 cm) were osmodehydrated using a 47 °Brix pomegranate cryoconcentrated juice at 30, 40, or 50°C for 180 min with an electric field of 6.66 V/cm (50 V) and a 5 min pulsed vacuum. Over the time, all of the treatments applied to the apple slices increased the soluble solids and bioactive compounds compared with the fresh sample. PVOD/OH at 50°C had the highest content of total anthocyanin during processing, and the best results for the total flavonoids were obtained with OD/OH at 50°C and 40°C. The osmodehydration assisted by pulse vacuum and ohmic heating using a cryoconcentrated juice is a useful combined technique to acquire enriched vegetal samples with bioactive compounds.

Microwave pretreatment and optimization of osmotic dehydration of wild blueberries using response surface methodology

This study investigated the effects of pretreatments and optimized osmotic dehydration (OD) of lowbush blueberries using response surface methodology (RSM) to produce dehydrated blueberries with high antioxidants content and shelf life. Fresh wild blueberries (WB) were initially pretreated and then subjected to osmotic dehydration. Microwave pretreated WB had shown better water loss during osmotic dehydration as compared to other pretreatment methods investigated. The highest levels of phenolics, flavonoids, and anthocyanin content of the dehydrated WB were found to be 742.61 mg/100 g, 263.12 mg/100 g, and 428.11 mg/100 g d.m respectively, at optimized temperature of 40 °C, for 5 h OD, with 65% (w/w) Brix and 1:5 ratio of sample to Brix%. These results revealed that with rigorous optimization of the critical osmotic dehydration parameters high level of antioxidants could be obtained in the dehydrated product.