Research progress in the application of catalytic infrared technology in fruit and vegetable processing.

Fruit and vegetable processing can effectively maintain the quality and safety of fruit and vegetable-based products while extending the shelf life of products and saving transportation costs. Infrared (IR) technology has been widely used in many operating units of fruit and vegetable processing because of its versatility of uniform heating, high heat transfer efficiency, and minimized damage to fruit and vegetable tissues. Catalytic IR (CIR), compared to traditional electric IR, is powered by natural gas or liquefied gas, which can improve thermal efficiency while significantly saving energy. However, there is no comprehensive overview discussing and summarizing the utilization and application of the CIR technology in fruit and vegetable processing. Therefore, this review aims to highlight recent advances in the application of CIR technology in fruit and vegetable processing. Specifically, a comprehensive discussion of the physicochemical properties and underlying mechanisms of CIR is provided, and its applications as a single method or in combination with other technologies in fruit and vegetable processes, such as blanching, peeling, microbial population reduction, and drying, are also presented. Besides, the currently used laboratory and pilot-scale equipment of CIR has also been summarized.

Research progress on extraction of active components from apple processing waste.

Apple waste (APW) is the residual product after apple processing, including apple peel, apple core, apple seed, and other components. A large quantity of APW produced is abandoned annually, leading to serious resource waste and environmental pollution. APW is rich in natural active compounds, such as pectin, polyphenols, fatty acids, and dietary fiber, which has a good use value. This paper reviewed the current research on recovering active components from APW. The traditional extraction methods (acid, alkali, physical, enzyme, etc.) and the novel extraction methods (SWE, UAE, MAE, RFAE, etc.) for the recovery of pectin, polyphenols, apple seed oil, apple seed protein, and dietary fiber from APW were systematically summarized. The basic principles, advantages, and disadvantages of different extraction methods were introduced. The requirements of different extraction methods on extraction conditions and the effects of different extraction methods on the yield, quality, and functional activity of extracted products were analyzed. The challenges and future study direction of APW extraction have prospected. This paper aims to provide a reference for other researchers interested in APW extraction, improve the utilization rate of APW and extend the value chain of the apple industry.

Application of pretreatment methods on agricultural products prior to frying: a review.

Frying is one of the methods of processing foods, which imparts flavour, taste, colour and crispness in the fried foods. In spite of an increase in the demand for fried foods by consumers all over the world, the danger posed by consuming too much fat is still a challenge. Many researchers have put forward many ideas on how to reduce the oil uptake and improve the nutritional and organoleptic qualities of foods during frying. Several pretreatment techniques applied to food materials prior to frying have been investigated by researchers in a bid to reduce the oil uptake and improve the quality parameters of fried foods. Therefore, this review focuses on the various pretreatment methods and the recent novel methods like ultrasound, infrared, superheated steam drying, microwave technique and pulsed electric field applied to foods prior to frying and its effects on the qualities of fried foods. © 2017 Society of Chemical Industry.

Degradation kinetics of aflatoxin B1 and B2 in solid medium by using pulsed light irradiation.

BACKGROUND: Pulsed light (PL) is a new potential technology to degrade aflatoxin. The objective of this study was to investigate the degradation characters of aflatoxin B1 (AFB1 ) and B2 (AFB2 ) treated under PL irradiation. A kinetic degradation study of AFB1 and AFB2 in solid medium was performed under PL irradiation at different initial concentrations of AFB1 (229.9, 30.7 and 17.8 µg kg-1 ) and AFB2 (248.2, 32.2 and 19.5 µg kg-1 ) and irradiation intensities (2.86, 1.60 and 0.93 W cm-2 ) of PL. A second-order reaction model was applied to describe degradation of AFB1 and AFB2 . RESULTS: The results showed that the degradation of AFB1 and AFB2 followed the second-order reaction kinetic model well (R2  > 0.97). The degradation rate was proportional to the intensities of PL irradiation and the initial concentrations of aflatoxins. CONCLUSION: It is concluded that the degradation of AFB1 and AFB2 with the use of PL could be accurately described using the second-order reaction kinetic model. © 2018 Society of Chemical Industry.

Simultaneous decontamination and drying of rough rice using combined pulsed light and holding treatment.

BACKGROUND: Pulsed light (PL) technology has been proven effective in food disinfection. However, increasing the light intensity or treatment time could swiftly increase the temperature of the food product. Using the thermal effect in an appropriate way may achieve a simultaneous disinfection and drying effect. The objective of this study was to investigate the feasibility of simultaneous disinfection and drying of rough rice using PL and holding treatment. RESULTS: Freshly harvested rice samples were inoculated by Aspergillus flavus (A. flavus) and treated using PL under different intensities and durations followed by holding treatment. The PL treatment under intensity of 1.08 W cm(-2) for 21 s led to a reduction of 0.29 log cfu g(-1) on the population size of A. flavus spores. After holding treatment, a 5.2 log cfu g(-1) reduction was achieved. The corresponding total moisture removal reached 3.3% points. No adverse effect on milling quality was detected after the treatment. CONCLUSION: The obtained results revealed that the combined PL and holding treatment had good potential for successful application in the rice industry to simultaneously achieve disinfection and drying. © 2015 Society of Chemical Industry.

Ultrasound Intensify the Flavonoid Production of the Willow Bracket Mushroom, Phellinus igniarius (Agaricomycetes), Fermentation Mycelia.

This research aimed to use a novel and effective ultrasound (US) approach for obtaining high bio-compound production, hence proposing strategies for boosting active ingredient biosynthesis. Furthermore, the US promotes several physiological effects on the relevant organelles in the cell, morphological effects on the structure of Phellinus igniarius mycelium, and increases the transfer of nutrients and metabolites. One suitable US condition for flavonoid fermentation was determined as once per day for 7-9 days at a frequency 22 + 40 kHz, power density 120 W/L, treated 10 min, treatment off time 7 s. The flavonoid content and production increased about 47.51% and 101.81%, respectively, compared with the untreated fermentation (P < 0.05). SEM showed that sonication changes the morphology and structure of Ph. igniarius mycelium; TEM reveals the ultrasonic treatment causes organelle aggregation. The ultrasound could affect the metabolism of the biosynthesis of the active ingredients.

Effect of thermosonication on texture degradation of carrot tissue in relation to alterations in cell membrane and cell wall structure.

Thermosonication as an alternative to hot water blanching of carrots, the effect of thermosonication on the carrot texture and cell structure required deep investigation. This study was conducted from the aspects of cell membrane, cell water, and cell wall pectin. Results showed that thermosonication at 60 °C significantly increased carrot tissue hardness by up to 10.3% compared with fresh. Rheological curves showed that the carrot tissues remained rigid after thermosonication. Cell membrane permeability was damaged to different extents during processing, inducing bound and immobilized water to migrate to free water and bring intracellular electrolytes to outflow. Thermosonication affected cell structure by altering the characteristics of pectin, including uronic acids and neutral sugar contents, degree of linearity and branching, and degree of methoxylation. The modified pectin can seize more divalent cations such as Ca2+ retained in the thermosonicated carrot cell wall, conducive to preserving the textural property of processed fruits and vegetables.

Ultrasonic-assisted flowing water thawing of frozen beef with different frequency modes: Effects on thawing efficiency, quality characteristics and microstructure.

This study aimed to evaluate the effects of ultrasonic-assisted thawing at different frequency modes (mono-, dual- and tri-frequency) on the thawing efficiency and quality evaluation of frozen beef. The thawing time, muscle quality, and microstructure of frozen beef were studied. The results showed that ultrasonic-assisted thawing effectively reduced the thawing time by 15.7-45.4% compared with flowing water thawing. For the quality properties of beef tissue, the ultrasound-assisted thawing with the single-frequency of 22 kHz and the dual-frequency of 22/33 kHz showed a higher water holding capacity; meanwhile, shear force values were also significantly decreased, and the tenderness of beef tissue was improved accordingly under such conditions. The microstructure analysis showed that the distribution of beef muscle fibers became closer and more regular. Therefore, ultrasound-assisted thawing treatments at 22 kHz single-frequency and 22/33 kHz dual-frequency have a high potential application value in the thawing industry of frozen beef.

Thermosonication inactivation of horseradish peroxidase with different frequency modes: Effect on activity, structure, morphology and mechanisms.

This study aimed to investigate the effect of thermosonicaion (TS) with different frequency modes on the horseradish peroxidase (HRP) inactivation from the aspects of ultrasound field and enzyme structural changes. The relationships between the activity and structural modification were also evaluated. A thermal-only treatment was performed to estimate the action of ultrasound in TS treatment. Compared to mono-frequency, especially the 33 kHz, TS with dual- and tri-frequency modes showed an intensive inactivation impact on HRP. Exogenous hydroxyl radical test showed the hydroxyl radical played a vital role in HRP inactivation. Changes in hematin group, tertiary and secondary structures were also confirmed, and the inactivation process followed an all-or-none model. Morphological images indicated the aggregation and deformation of HRP molecules during TS treatment, and roughness values were changed accordingly. Pearson correlation analysis implied that the structural destruction on the spatial conformation of HRP was strongly related to its activity.

[Study on the structure of defatted wheat germ protein isolate under ultrasonic treatment].

The structure changes of defatted wheat germ protein Isolate (DWGP) treated by ultrasonic was determined by FTIR and fluorescence spectra, and the effect of its structure changes on the high-efficient enzymatic hydrolysis was studied. Research showed that the efficiency of hydrolysate could be improved by ultrasonic treatment. Compared with control group, inhibitory activity of the hydrolysate was increased by 23.96% after the treatment of 600 W for 10 min. The fluorescence intensity of DWGP after ultrasonic treatment was found discovered to be changed. An appropriate ultrasonic treatment can unfold the protein molecule and make the chromogenic groups uncovered, which contribute to the acquirement of the higher-activity inhibitory peptide. The effects of various ultrasonic power and time on the secondary structure of DWGP were quantitatively determined via analysis of the amide I changes of infrared spectra using curve fitting method. Content of beta-sheet was decreased and beta-turn was increased after ultrasonic treatment, which could be the main factor to make the prepared inhibitory peptides high efficient. The results provide a theoretical basis for the mechanism research of enzymatic hydrolysis of ultrasonic treated protein.

Enhancing jackfruit infrared drying by combining ultrasound treatments: Effect on drying characteristics, quality properties and microstructure.

This study investigates the enhancing effect of power ultrasound (US, 80 W) on the drying characteristics, quality properties and microstructure of jackfruit slices treated with infrared (IR) treatments of 900 W, 1200 W and 1500 W in the meantime. Results showed that when ultrasound was applied, the drying time was reduced by 31%, 35% and 25% compared to pure IR 900 W, 1200 W and 1500 W, respectively. Meanwhile, Deff values of dried samples were improved. The application of ultrasound significantly increased vitamin C retention and total phenolic content at IR 900 W. The micrographs indicate that ultrasound provided a more porous microstructure of dried jackfruit slices thus accelerating the drying process. The color characteristics of IR-US samples showed no significant change compared to IR drying slices. This study shows that infrared assisted with ultrasound can be a potential method for industrial production of dried jackfruit slices.

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.

Application of multi-frequency power ultrasound in selected food processing using large-scale reactors: A review.

Ultrasound as an eco-friendly green technology has been widely studied in food processing. Nevertheless, there is a lack of publications regarding the application of ultrasound in food processing using large-scale reactors. In this paper, the mechanisms and the devices of multi-frequency power ultrasound (MFPU) are described. Moreover, the MFPU applied in enzymolysis of protein, and washing of fruits and vegetables are reviewed. The application of MFPU can improve the enzymolysis of protein through modification on enzyme, modification on substrate materials, and facilitation of the enzymatic hydrolysis process. The ultrasound treatment can enhance the removal of microorganisms, and pesticides on the surface of fruits and vegetables. Furthermore, the reactors of ultrasound-assisted enzymolysis of protein, and washing of fruits and vegetables on the industrial scale are also detailed. This review paper also considers future trends, limitations, drawbacks, and developments of ultrasound application in enzymolysis and washing.

Vacuum pretreatment coupled to ultrasound assisted osmotic dehydration as a novel method for garlic slices dehydration.

This study investigated the effects of multi-frequency mode ultrasound and vacuum technology on the water loss (WL) of garlic slices during osmotic dehydration (OD), and their effects on the microstructure of garlic. A new method of OD for garlic slices was proposed - Vacuum pretreatment coupled to ultrasound assisted osmotic dehydration (VUOD). The results indicated that the WL of the garlic slices treated with VUOD (21.12%) was significantly (p < 0.05) higher than slices treated with normally OD (NOD) (10.67%), vacuum pretreatment OD (VOD) (14.18%), and multi-frequency mode ultrasound assisted OD (UOD) (11.20-13.56%). A mass transfer mechanism of VUOD was proposed. Low-field nuclear magnetic resonance results quantified the moisture migration in the vacuole, cytoplasm and intercellular space, and the cell wall of garlic cells. The quality properties (allicin content, surface color change and firmness) of VUOD treated garlic slices are predominately better than NOD, VOD and UOD treated samples.

Effect of vacuum and ethanol pretreatment on infrared-hot air drying of scallion (Allium fistulosum).

This study examined the effects of vacuum, ethanol pretreatment, and infrared-hot air drying methods on the characteristics and quality of scallion slices. The pretreatment of scallion includes four conditions: 1) Control: soaking in distilled water under normal pressure, 2) Ethanol: soaking in 75% ethanol under normal pressure, 3) Water + VC: soaking in distilled water under a vacuum of 0.6 bar, 4) Ethanol + VC: soaking in 75% ethanol under a vacuum of 0.6 bar. The pretreatment times were 5, 10, 20 and 30 min. The drying process was done in an infrared hot air drying oven at 60 °C. The ethanol pretreated samples exhibited better rehydration, odor, vitamin C retention, bactericidal effect and significantly reduced drying time. Water + VC samples showed better scallion morphology and color. Ethanol + VC samples showed the combined advantages of ethanol and Water + VC pretreatments. Therefore, Ethanol + VC pretreatment can significantly improve the drying rate and quality of scallion.

Modification of garlic skin dietary fiber with twin-screw extrusion process and in vivo evaluation of Pb binding.

This study investigated the effects of a twin-screw extrusion-cooking process on the modification of garlic skin dietary fiber (DF) under optimal conditions (feed moisture 25%, extrusion temperature 170 °C and screw speed 170 rpm). The evaluation of the soluble dietary fiber (SDF) from the extruded garlic skin on the capacity of Pb binding was determined in vivo. Compared with the untreated garlic skin, the content of extruded garlic skin SDF increased from 5.31 ±â€¯0.58% to 15.87 ±â€¯0.88%. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images demonstrated that the macromolecules deteriorated to form smaller SDF fractions during extrusion. Moreover, differential scanning calorimetry (DSC) spectra showed the thermal stability of the extruded SDF was highly improved after extrusion. Additionally, in vivo experimental results indicated that the addition of extruded DF significantly reduced the Pb absorptivity of rats with exposed Pb concentrations at 20, 100 and 200 mg/kg. The findings showed that the extruded garlic skin DF has a positive effect on Pb binding.

Effect of catalytic infrared dry-blanching on the processing and quality characteristics of garlic slices.

This study investigates the effects of catalytic infrared (CIR) dry-blanching (CIRDB) on the processing and quality of garlic slices. CIRDB processing parameters of CIR processing temperature, slice thickness and processing time were studied versus the processing characteristics of internal temperature, peroxidase (POD) activity and moisture reduction. Blanched garlic quality characteristics of surface color change (ΔE), allicin retention rate, vitamin C retention rate and microbial content were determined. Hot water blanching (WB) was used as a comparison. The results indicated that increasing CIR processing temperature and/or reducing the slice thickness accelerated internal temperature rise and POD inactivation and moisture reduction. To achieve 90% inactivation of POD, the CIRDB treatment resulted in moisture reductions of 15.87-40.37%, microbial reductions of 1.76-3.91-log, ΔE between 2.03 and 10.01, retention rate of allicin between 10.63 and 33.31%, and retention rate of vitamin C between 55.00 and 81.13%. CIRDB achieved the high-quality garlic products compared with WB.

Effect of pulsed light on activity and structural changes of horseradish peroxidase.

The objective of this research was to investigate the effects of pulsed light on the activity and structure of horseradish peroxidase in buffer solution. Enzyme residual activities were measured. Surface topography, secondary, and tertiary structures of horseradish peroxidase were determined using atomic force microscopy (AFM), Raman spectroscopy, and fluorescence spectroscopy, respectively. Results showed that a complete inactivation of horseradish peroxidase was achieved by application of 10 pulses of pulsed light treatment at an intensity of 500J/pulse. The AFM analysis revealed that the aggregation of enzyme protein increased and surface roughness decreased with the increase in the treatment time. Fluorescence and Raman spectroscopy analysis exhibited that pulsed light destroyed the tertiary and secondary protein structures. The ß-sheet composition was decreased while ß-turn and random coils were increased. Pulsed light could effectively inactivate horseradish peroxidase by destroying the secondary and tertiary structures of protein in the active center of the enzyme.

Effective disinfection of rough rice using infrared radiation heating.

The objective of this study was to investigate the effect of infrared (IR) heating and tempering treatments on disinfection of Aspergillus flavus in freshly harvested rough rice and storage rice. Rice samples with initial moisture contents (IMCs) of 14.1 to 27.0% (wet basis) were infected with A. flavus spores before the tests. The infected samples were heated by IR radiation to 60°C in less than 1 min, and then samples were tempered at 60°C for 5, 10, 20, 30, 60, or 120 min. High heating rates and corresponding high levels of moisture removal were achieved using IR heating. The highest total moisture removal was 5.3% for the fresh rice with an IMC of 27.0% after IR heating and then 120 min of tempering. IR heating followed by tempering for 120 min resulted in 2.5- and 8.3-log reductions of A. flavus spores in rough rice with the lowest and highest IMCs, respectively. To study the effect on disinfection of rewetting dried storage rice, the surface of the dry rice was rewetted to achieve IMCs of 14.7 to 19.4% (wet basis). The rewetting process for the dry rice had a significant effect on disinfection. IR heating followed by tempering for 60 min resulted in 7.2-log reductions in A. flavus on rewetted rough rice. The log-linear plus tail model was applied to estimate the tempering time needed to achieve a 5-log reduction of A. flavus in rice of different IMCs. At least 30 and 20 min of tempering were needed for fresh rice and rewetted rice, respectively, with the highest IMCs. The recommended conditions of simultaneous disinfection and drying for fresh rice was IR heating to 60°C followed by tempering for 120 min and natural cooling, resulting in a final MC of 16.5 to 22.0%, depending on the IMC. For the rewetted dry rice with an IMC of 19.4%, the recommended condition for disinfection and drying involved only 20 min of tempering. The final MC of the sample was 13.8%, which is a safe MC for storage rice.