Secondary structure and conformational change of mushroom polyphenol oxidase during thermosonication treatment by using FTIR spectroscopy

Investigating the impact of ultrasound on the structural, physicochemical, and emulsifying characteristics of Dioscorin: Insights from experimental data and molecular dynamics simulation

This study investigated the impact of ultrasound treatment on dioscorin, the primary storage protein found in yam tubers. Three key factors, namely ultrasound power, duration, and frequency, were focused on. The research revealed that ultrasound-induced cavitation effects disrupted non-covalent bonds, resulting in a reduction in α-helix and β-sheet contents, decreased thermal stability, and a decrease in the apparent hydrodynamic diameter (Dh) of dioscorin. Additionally, previously hidden amino acid groups within the molecule became exposed on its surface, resulting in increased surface hydrophobicity (Ho) and zeta-potential. Under specific ultrasound conditions (200 W, 25 kHz, 30 min), Dh decreased while Ho increased, facilitating the adsorption of dioscorin molecules onto the oil-water interface. Molecular dynamics (MD) simulations showed that at lower frequencies and pressures, the structural flexibility of dioscorin's main chain atoms increased, leading to more significant fluctuations between amino acid residues. This transformation improved dioscorin's emulsifying properties and its oil-water interface affinity.

Effect of oil extraction methods on walnut oil quality characteristics and the functional properties of walnut protein isolate

Walnut oils were obtained by supercritical carbon dioxide extraction (SCB), cold-pressing (CP), hexane extraction (HE), and subcritical butane extraction (SBE), and walnut protein isolates (WPI) from the walnut cakes were performed. The results indicate that SCB has the highest oil yield for walnut oil, which was 62.72%, and the total content of trace nutrients (total tocopherols, total phytosterols, and total phenolic compounds) in SCB-walnut oil was also the highest at 2186.75 mg/kg, approximately 1.05 times higher than CP-walnut oil and 1.21 times higher than SBE-walnut oil. Meanwhile, the treatment of WPI with SCB results in a decrease in β-Sheet and α-Helix structures and an increase in β-Turn and Random coil structures. Thereby increasing its oil-holding capacity (OHC) and solubility by approximately 1.16 times and 1.27 times compared to CP, respectively. Interestingly, SCB as a green oil production technology, also has good prospects for retaining WPI functionality characteristics.

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.

Applications of ultrasonication on food enzyme inactivation- recent review report (2017-2022)

Ultrasound processing has been widely applied in food sector for various applications such as decontamination and structural and functional components modifications in food. Enzymes are proteinaceous in nature and are widely used due to its catalytic activity. To mitigate the undesirable effects caused by the enzymes various technologies have been utilized to inactive the enzymes and improve the enzyme efficiency. Ultrasound is an emerging technology that produces acoustic waves which causes rapid formation and collapse of bubbles. It has the capacity to break the hydrogen bonds and interact with the polypeptide chains due to Vander Waals forces leading to the alteration of the secondary and tertiary structure of the enzymes thereby leading to loss in their biological activity. US effectively inactivates various dairy-related enzymes, including alkaline phosphatase (ALP), lactoperoxidase (LPO), and γ-glutamyl transpeptidase (GGTP) with increased US intensity and time without affecting the natural dairy flavors. The review also demonstrates that inactivation of enzymes presents in fruit and vegetables such as polyphenol oxidase (PPO), polygalacturonase (PG), Pectin methyl esterase (PME), and peroxidase. The presence of the enzymes causes detrimental effects causes off-flavors, off-colors, cloudiness, reduction in viscosity of juices, therefore the formation of high-energy free molecules during sonication affects the catalytic function of enzymes and thereby causing inactivation. Therefore this manuscript elucidates the recent advances made in the inactivation of common, enzymes infruits, vegetables and dairy products by the application of ultrasound and also explains the enzyme inactivation kinetics associated. Further this manuscript also discusses the ultrasound with other combined technologies, mechanisms, and its effects on the enzyme inactivation.

Sono-activation of food enzymes: From principles to practice

Over the last decade, sono-activation of enzymes as an emerging research area has received considerable attention from food researchers. This kind of relatively new application of ultrasound has demonstrated promising potential in facilitating the modern food industry by broadening the application of various food enzymes, improving relevant industrial unit operation and productivity, as well as increasing the yield of target products. This review aims to provide insight into the fundamental principles and possible industrialization strategies of the sono-activation of food enzymes to facilitate its commercialization. This review first provides an overview of ultrasound application in the activation of food protease, carbohydrase, and lipase. Then, the recent development on ultrasound activation of food enzymes is discussed on aspects including mechanisms, influencing factors, modification effects, and its applications in real food systems for free and immobilized enzymes. Despite the far fewer studies on sono-activation of immobilized enzymes compared with those on free enzymes, we endeavored to summarize the relevant aspects in three stages: ultrasound pretreatment of free enzyme/carrier, assistance in immobilization process, and modification of the already immobilized enzyme. Lastly, challenges for the scalability of ultrasound in these target areas are discussed and future research prospects are proposed.

Determination on Tree Species Selection for Lingzhi or Reishi Medicinal Mushroom Ganoderma lucidum (Agaricomycetes) Cultivation by Fourier Transform Infrared and Two-Dimensional Infrared Correlation Spectroscopy

As a wood-degrading Agaricomycetes mushroom, Ganoderma lucidum can be cultivated on broad-leaf hardwoods. Generally, producers care about the yield, but not the quality of G. lucidum cultivated by different tree species. In this study, five broad-leaf hardwood tree species-Quercus variabilis Bl. (Qv), Castanea mollissima Bl. (Cm), Liquidambar formosana Hance (Lf), Dalbergia hupeana Hance (Dh), and Platycarya strobilacea Sieb. et Zucc. (Ps)-were selected for cultivating of G. lucidum. The chemical compositions of G. lucidum fruiting bodies produced by these tree species were determined by Fourier transform infrared and two-dimensional infrared correlation spectroscopy in order to select the most suitable tree species for cultivation. The overall spectra showed less discrimination of each peak variation detected and properly kept most of the primary metabolites. The second derivative unfolded the stagnation of the first spectrum and more base peaks were detected especially in the range of the first two sections. The protein content contained in G. lucidum cultivated on Ps was 92%, like that on Dh. On the other hand, only 27% similarity was determined in G. lucidum cultivated on Ps and Qv. Therefore, the correlation of this range for the protein content can help in tree species selection. The active sequence of 2DIR spectral could be determined by the active bonding of the component reacted to the perturbation. The result could provide a scientific basis for the selection of tree species and the comprehensive utilization of broad-leaf tree resources on G. lucidum cultivation.

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.

Effects of flat sweep frequency and pulsed ultrasound on the activity, conformation and microstructure of mushroom polyphenol oxidase

The effects of thermal processing (TP) and flat sweep frequency and pulsed ultrasound (FSFPU) treatment with different frequency modes on the activity, conformation and physicochemical properties of mushroom polyphenol oxidase (PPO) were investigated. The results showed that the relative enzymatic activity of PPO gradually decreased with increasing temperature and duration, and thermosonication decreased the PPO activity to a greater extent compared with thermal processing. FSFPU treatment with dual-frequency of 22/40 kHz mode showed the most significant effect. Circular dichroism (CD) showed that the content of α-helix and β-turn dropped, while that of β-sheet and random coil raised after FSFPU treatment. The intensity of endogenous fluorescence decreased, indicating that PPO protein unfolded and the tertiary structure was destroyed. The amount of free sulfhydryl, protein aggregation index, and turbidity all rose. Moreover, FSFPU treatment led to the aggregation of protein from the analysis of atomic force microscope (AFM). Conclusively, FSFPU can be used as an effective method to inhibit the activity of endogenous enzymes in food.

Effect of infrared radiation on activity and conformation of polyphenol oxidase from Acetes chinensis

The aim of this paper was to study the effect of infrared radiation (IR) on the activity and conformation of polyphenol oxidase (PPO) in Acetes chinensis. In this paper, the specific activity of PPO was increased from 21.2 to 643.4 U/mg by a four-step purification. The results showed that IR treatment had greater effect on the enzyme activity and conformation of PPO than hot air (HA) treatment. After IR treatment at 70°C, the relative enzyme activity of PPO was 9.28%, the surface hydrophobicity index increased by 80.42%, and the content of sulfhydryl group decreased to 96.99% of the control group. The results of circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) showed that the α-helix of PPO treated by IR decreased and the random coil increased. The intrinsic fluorescence intensity of PPO decreased after IR treatment, indicating that the tertiary structure of PPO was destroyed. Scanning electron microscopy (SEM) results showed that the surface microstructure of PPO after IR treatment became clear and compact. In conclusion, IR treatment can completely destroy the secondary structure and tertiary structure of PPO and cause enzyme inactivation. This study provides a treatment for reducing the activity of PPO from A. chinensis during the production and processing. PRACTICAL APPLICATION: This study shows that IR treatment has a better inhibitory effect on the activity of PPO than HA treatment. It provides a better treatment method for inactivating the activity of PPO from Acetes chinensis during the production and processing.

Ultrasound, infrared and its assisted technology, a promising tool in physical food processing: A review of recent developments

Traditional food processing techniques can no longer meet the ever increasing demand for high quality food across the globe due to its low process efficiency, high energy consumption and low product yield. This review article is focused on the mechanism and application of Infrared (IR) and ultrasound (US) technologies in physical processing of food. We herein present the individual use of IR and US (both mono-frequency and multi-frequency levels) as well as IR and US supported with other thermal and non-thermal technologies to improve their food processing performance. IR and US are recent thermal and non-thermal technologies which have now been successfully used in food industries to solve the demerits of conventional processing technologies. These environmentally-friendly technologies are characterized by low energy consumption, reduced processing time, high mass-transfer rates, better nutrient retention, better product quality, less mechanical damage and improved shelf life. This work could be, with no doubt, useful to the scientific world and food industries by providing insights on recent advances in the use of US and IR technology, which can be applied to improve food processing technologies for better quality and safer products.

Structural characterization and functional properties of CNPP, a byproduct formed during CPP preparation

Casein nonphosphopeptide (CNPP), a byproduct formed during the preparation of casein phosphopeptide (CPP), is often discarded on a large scale. Although our previous studies have demonstrated the ameliorative effect of CNPP on muscle wasting disorders, its structure-function mechanism is still unclear. Therefore, considering the great influence of structural characteristics on function, this study aims to explain the potential mechanism by characterizing the physicochemical and functional properties of CNPP. The results of structural characterization indicated that CNPP was of low molecular weight and composed of the complete range of amino acids; it was particularly rich in leucine. Compared with casein, CNPP had a lower molecular size and total/free sulfhydryl content (reduced 2.44 and 2.02 µmol/g in CNPP, respectively). Additionally, Fourier transform infrared spectroscopic analysis revealed that enzymatic hydrolysis caused protein unfolding, and the content of β-turns and random coils reached 50.20% and 10.67%, respectively. Fluorescence-dependent detection of CNPP indicated a reduction of spectral intensity and the occurrence of a red shift. The changes in the structure of CNPP significantly affected its functional characteristics. CNPP has better solubility, foaming, and digestion properties than those of casein and whey protein. Specifically, the foam stability and emulsification properties decreased in the order of casein > CNPP > whey protein. The present study can provide a substantial basis for future application of CNPP as a functional ingredient against sarcopenia.

Effects of ultrasound-assisted sodium bisulfite pretreatment on the preparation of cholesterol-lowering peptide precursors from soybean protein

In order to take full advantage of the gastrointestinal digestive function, the effects of S-type ultrasound-assisted sodium bisulfite (UASB) pretreatment on the preparation of cholesterol-lowering peptide precursors derived from soybean protein were investigated and the structural characterizations of pretreated proteins were explored. UASB pretreatment with the operational mode of mono-frequency ultrasound at 28 kHz, ultrasonic power density of 200 W/L and ultrasonic time of 50 min exhibited the highest cholesterol-lowering activity (56.90%) of soybean protein hydrolysates (SPH) after simulated gastrointestinal digestion, which increased by 87.17% compared to the control. Under these conditions, the peptide content of SPH after simulated gastrointestinal digestion was not significantly different (p > 0.05) compared to the control. Further FTIR analysis showed that UASB pretreatment increased β-turn and β-sheet content and decreased α-helix and random coil content. The changes in the surface hydrophobicity and microstructures of soybean protein indicated that UASB pretreatment loosened soybean protein structure and exposed more hydrophobic groups. SDS-PAGE indicated that the restriction sites changed after UASB pretreatment. In conclusion, UASB pretreatment is an efficient method for the preparation of cholesterol-lowering peptide precursors.

Inhibition mechanism: Phytic acid, NADH as a peroxidase inhibitor

Peroxidase, a key enzyme causing enzymatic browning, and affected the potential values of fruit and vegetables. Phytic acid and NADH inhibited peroxidase in a competitive manner due to their reducing properties, and it's IC₅₀ (1.18 ± 0.32) × 10^-8, (8.02 ± 0.45) × 10^-6 mol L^-1, respectively. The interaction between phytic acid, NADH and peroxidase contributed to intrinsic fluorescence quenching and conformation alternation with a accuracy determination by multispectroscopic techniques (fluorescence spectra, FT-IR and CD spectra), respectively. Molecular docking simulation revealed that phytic acid, NADH interacted with His170, Ala34, Arg38, Ser73, Arg31, Lys174, Gln176, Asn175, Arg75; Gln176, Asn175, Phe221, Lys174, Gly173, Ser167, Phe172, Gly169, His170 in peroxidase, respectively and blocked substrates into catalytic reactions.

The inhibition mechanism of luteolin on peroxidase based on multispectroscopic techniques

Luteolin, a plant-derived flavonoid, was found to exert effective inhibitory effect to peroxidase activity in a non-competitive manner with an IC50 of (6.62 ± 0.45) × 10-5 mol L-1. The interaction between luteolin and peroxidase induced the formation of a static complex with a binding constant (Ksv) of 7.31 × 103 L mol-1 s-1 driven by hydrogen bond and hydrophobic interaction. Further, the molecular interaction between luteolin and peroxidase resulted in intrinsic fluorescence quenching, structural and conformational alternations which were determined by multispectroscopic techniques combined with computational molecular docking. Molecular docking results revealed that luteolin bound to peroxidase and interacted with relevant amino acid residues in the hydrophobic pocket. These results will provide information for screening additional peroxidase inhibitors and provide evidence of luteolin's potential application in preservation and processing of fruit and vegetables and clinical disease remedy.

Structural and physicochemical characteristics of lyophilized Chinese sturgeon protein hydrolysates prepared by using two different enzymes

The structural and physicochemical characteristics of protein hydrolysates prepared from Chinese sturgeon through the enzymatic hydrolysis process were evaluated. Two different enzymes including papain and alcalase 2.4L were used in the hydrolysis process. The papain enzyme significantly increased the degree of hydrolysis (20.62%) and decreased the ζ-potential (12.4 ± 1.31 mV) as compared to the alcalase enzyme, which represented 15.55% and 15.53 ± 0.77 mV, respectively. Alcalase 2.4L hydrolysate exhibited smaller particle size (822.047 ± 61.26 nm) than papain hydrolysate (1425.39 ± 44.82 nm). Hydrolysis by papain and alcalase 2.4L enzymes decreased the molecular weights (MW ≤ 1,000 Da) to 98.27% and 86.84%, respectively. The surface hydrophobicity and turbidity of the hydrolysates significantly affected by enzyme type and protein concentrations. By using the X-ray diffraction analysis, the papain hydrolysate showed a higher relative crystallinity degree (30.33%) than alcalase 2.4L hydrolysate (29.40%), whereas the Fourier transform infrared spectroscopy showed more clearly peaks for the amide bands of alcalase hydrolysate. The thermal properties also affected by enzymatic hydrolysis conditions, since the melting temperatures were 159.17 and 149.58 °C, whereas the rate of mass loss was 67.04% and 62.8%, for papain and alcalase hydrolysates, respectively. PRACTICAL APPLICATION: The enzymatic hydrolysis process of proteins is employed to obtain the nutritionally and functionality important peptides that result during the preparation of fish protein hydrolysate. The objective of this study was to investigate the structural and physicochemical characteristics of protein hydrolysate prepared from Chinese sturgeon. This study showed that these characteristics were affected by enzymatic hydrolysis conditions especially enzyme type. The finding of this study may be useful in terms of providing new information on the properties of the protein hydrolysate and the structural changes resulting from controlled enzymatic hydrolysis conditions. Overall, these conditions could potentially alter the secondary structure of the protein hydrolysates or peptides and enhance their functional properties.

Thermosonication-induced structural changes and solution properties of mung bean protein

Mung bean protein is considered a highly nutritive food ingredient, but its solution properties are not well defined. In this study, suspensions of mung bean protein isolate (MPI, 10%, w/v) were subjected to high intensity ultrasound (20 kHz, 30% amplitude) at varied durations (5, 10, 20, and 30 min) with controlled temperatures (30, 50, and 70 °C) to determine the effects of thermosonication treatment on physical properties of the protein solution. Results showed that thermosonication treatment significantly reduced the particle size and free sulfhydryl content of MPI in a time-dependent manner. Ultrasound increased surface hydrophobicity, and the exposure of nonpolar groups led to the formation of soluble aggregates. Changes in secondary structure of MPI were minimal at 30 and 50 °C but were significant at 70 °C. The dissociation of native components followed by reaggregation into soluble particles following ultrasound treatment at 70 °C resulted in remarkable improvements of protein solubility (>2 fold), clarity, and stability of the MPI suspensions. The findings indicated that thermosonication could be a promising technology for the processing of mung bean protein beverage.

Cysteine Protease Inhibitors Reduce Enzymatic Browning of Potato by Lowering the Accumulation of Free Amino Acids

Enzymatic browning is a major issue affecting the quality of processed potato (Solanum tuberosum L.). To understand the molecular mechanism of browning, transcriptional analyses were performed by employing potatoes that differed in browning. Coexpression analysis indicated that 9 out of 15 upregulated genes in browning-less groups encoded for potato protease inhibitors (StPIs). In addition, gene otology analysis showed that the enriched terms were mainly involved in protease inhibitors. Overexpression of cysteine StPI 143 and StPI 146 individually reduced browning and lowered protease activities and tyrosine and total free amino acid (FAA) contents, but they could not decrease polyphenol oxidase activity. Moreover, supplementing exogenous tyrosine or total FAAs into transgenic potato mash to wild-type amounts promoted mash browning, browning with total FAAs, more than with tyrosine, resembling wild-type levels. These results implied that cysteine StPIs reduced browning via lowering the accumulation of FAAs in addition to tyrosine. Our findings have enriched the knowledge about the roles and mechanisms of protease inhibitors in regulating enzymatic browning of potato, which provide new ways for controlling potato browning.

Inhibition and molecular mechanism of diosmetin against xanthine oxidase by multiple spectroscopies and molecular docking

Studying the inhibition and molecular mechanism of diosmetin against xanthine oxidase helps to develop natural product xanthine oxidase inhibitors.

Ultrasound treatment on the structure of goose liver proteins and antioxidant activities of its enzymatic hydrolysate

This study was to investigate the effects of ultrasonic treatment on the physical and chemical properties of goose liver protein (GLP) and the anti-oxidative activity of the goose liver protein hydrolysate (GLPH). By measuring the average particle size, sulfhydryl and disulfide bond, secondary structure, hydroxyl radical inhibition, 1, 1-diphenyl-2-picrylhydrazyl radical scavenging rate, and ferrous ion chelating ability, we found that 300 and 600 W ultrasonic treatment reduced the particle size of GLP from 509.7 μm to 313.7 μm and 273.1 μm, respectively, and significantly decreased the content of sulfhydryl and the structures of α-helix and β-turn (p < .05). Meanwhile, the content of disulfide bond and β-sheet structure increased significantly (p < .05); the antioxidant capacity of GLPH increased significantly (p < .05). After 300 W ultrasonic treatment, the GLP in the enzymatic hydrolysis process was more conducive to the release of antioxidant substances compared with the 600 W ultrasonic-treated GLP. PRACTICAL APPLICATIONS: The physical and chemical properties of the GLP were changed by ultrasonic treatment, which was beneficial to improve the texture quality of goose liver paste and the anti-oxidative activity of GLPH. It could enhanced the functional characteristics of goose liver paste by enzymolysis. Meanwhile, antioxidant components extracted by ultrasonic treatment from goose liver could be added to foods as an excipient to improve the antioxidant properties.

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.

Application of vibrational spectroscopy for classification, authentication and quality analysis of mushroom: A concise review

Chemical compositions of mushrooms are greatly dependent on the geographical region, and also the different parts of the same mushroom have different chemical constitutions. Several chemical methods are employed for quality control of mushrooms. However, these methods are destructive, require skilled personnel and are time consuming. To overcome these limitations researchers are aiming for vibrational spectroscopic techniques. This review is focused on various studies related to the application of vibrational spectroscopy for classification, authentication and quality analysis of mushrooms. It was concluded that vibrational spectroscopy could be efficiently employed for assessing the quality, authenticity and geographical origin of the mushrooms. Fourier-transform infrared (FTIR) and near infrared (NIR) spectroscopy were the most explored, whereas, Raman spectroscopy is the least explored technique in this field. Compact and cost-effective spectrometers based on the selective wavelengths have to be designed and installed at commercial and industrial level for rapid quality control of mushrooms.

Activation and conformational changes of chitinase induced by ultrasound

This study investigated the effect of ultrasound on chitinase activity and conformational changes. Results revealed that ultrasound activated chitinase with a maximum enhancement of 19.17% compared with the untreated chitinase. Furthermore, an increase of V_max and a decrease of K_m after sonication were obtained, illustrating that the affinity between chitinase and substrate was intensified. No obvious effect on the tolerance to most metal ions was exhibited whether sonicated or not (p > 0.05). The conformational changes of chitinase were analyzed by circular dichroism (CD), Fourier transform infrared (FTIR), Raman and fluorescence spectroscopy. Results indicated that the activation of chitinase induced by ultrasound was presumably due to the decrease of tryptophan on the chitinase surface and the increase of β-sheet and random coil in chitinase secondary conformation. In brief, ultrasound is a possible way to activate chitinase to increase its application in food industry.

Formation and Stability of Core-Shell Nanofibers by Electrospinning of Gel-Like Corn Oil-in-Water Emulsions Stabilized by Gelatin

Core-shell nanofibers were fabricated by electrospinning of gel-like corn oil emulsions stabilized by gelatin. The oil-in-water (O/W) emulsions satisfied the Herschel-Bulkley rheological model and showed shear-thinning and predominantly elastic gel behaviors. The increasing oil fractions (φ) ranging from 0 to 0.6 remarkably increased the apparent viscosity and then led to an increase in the average diameter and encapsulation efficiency of electrospun fibers. Core-shell structured fibers by emulsion electrospinning were observed in transmission electron microscopy (TEM) images. The encapsulated oil was found to randomly distribute as core, especially inside the beads. The binding of corn oil to gelatin was mainly driven by noncovalent forces. These core-shell fibers at various φ values (φ = 0.2, 0.4, 0.6, and 0.8) showed a high thermal decomposition stability upon heating to 250 °C, and the denaturation temperatures were 85.32 °C, 77.97 °C, 82.99 °C, and 87.25 °C, respectively. The corn oil encapsulated in emulsion-based fiber mats had good storage stability during 5 days. These results contributed to a good understanding of emulsion electrospinning of food materials for potential applications in bioactive encapsulation, enzyme immobilization, and active food packaging.

Effects of UV-B radiation on the isoflavone accumulation and physiological-biochemical changes of soybean during germination: Physiological-biochemical change of germinated soybean induced by UV-B

In this study, the effects of UV-B radiation on the isoflavones accumulation, physiological and nutritional quality, water status, and characteristics of proteins in germinated soybeans were investigated. The results showed that isoflavones content in soybeans increased with appropriate intensity and time of UV-B radiation and decreased with excessive treatment. Fresh weight, length, free amino acids, reducing sugar contents and bulk water (T23) in germinated soybeans decreased with increasing radiation time, indicating that UV-B inhibited the growth and nutrients metabolism of soybean during germination. Cell damage was detected in germinated soybeans with excessive UV-B radiation, as shown by the black spots in cotyledons and the increased intercellular water determined by LF-NMR. Germination resulted in an increase in random coil structures, while UV-B radiation induced no obvious changes in FT-IR spectrum and protein conformation of soybeans. Both UV-B radiation and germination caused the increase in soluble proteins, especially in 1.0-75.0 kDa fraction.

Effects of radio frequency assisted blanching on polyphenol oxidase, weight loss, texture, color and microstructure of potato

This paper is focused on the effects of radio frequency (RF) heating on the relative activity of polyphenol oxidase (PPO), weight loss, texture, color, and microstructure of potatoes. The results showed that pure mushroom PPO was almost completely inactivated at 80 °C by RF heating. The relative activity of potato PPO reduced to less than 10% with increasing temperature (25-85 °C). Enzyme extract showed the lowest PPO relative activity at 85 °C after RF treatment, followed by the potato cuboids and mashed potato, about 0.19 ± 0.017%, 3.24 ± 0.19%, and 3.54 ± 0.04%, respectively. Circular dichroism analysis indicated that RF heating changed the secondary structure of PPO, as α-helix content decreased. Both electrode gap and temperature had significant effect (P < .05) on weight loss, color, and texture of the potato cuboids. Microstructure analysis showed the changes of potato cell and starch during RF heating.

Ultrasound assisted intensification of enzyme activity and its properties: a mini-review

Over the last decade, ultrasound technique has emerged as the potential technology which shows large applications in food and biotechnology processes. Earlier, ultrasound has been employed as a method of enzyme inactivation but recently, it has been found that ultrasound does not inactivate all enzymes, particularly, under mild conditions. It has been shown that the use of ultrasonic treatment at appropriate frequencies and intensity levels can lead to enhanced enzyme activity due to favourable conformational changes in protein molecules without altering its structural integrity. The present review article gives an overview of influence of ultrasound irradiation parameters (intensity, duty cycle and frequency) and enzyme related factors (enzyme concentration, temperature and pH) on the catalytic activity of enzyme during ultrasound treatment. Also, it includes the effect of ultrasound on thermal kinetic parameters and Michaelis-Menten kinetic parameters (k_m and V_max) of enzymes. Further, in this review, the physical and chemical effects of ultrasound on enzyme have been correlated with thermodynamic parameters (enthalpy and entropy). Various techniques used for investigating the conformation changes in enzyme after sonication have been highlighted. At the end, different techniques of immobilization for ultrasound treated enzyme have been summarized.

Ascorbic acid stability in fruit juices during thermosonication

Thermosonication is an emerging technology useful for inactivating microorganisms and enzymes in fruit juices. However, the effect of the ultrasound processing on the ascorbic acid content is not clear and the results reported in the literature are contradictory. In this work, the impact of sonication and thermosonication on the ascorbic acid content was first evaluated in model systems. Degassed model solutions at four different pH values (3-6) were processed with or without sonication for 60min at two different conditions of temperature (25 and 55°C). In all cases, the ascorbic acid was stable under the treatment. After that, two commercial deaerated fruit juices were processed with and without US at 55°C. The ascorbic acid was also retained in these juices after the ultrasound processing under the most severe conditions studied. In conclusion, previous degassing/deaerating of fruit juices is recommended to prevent ascorbic acid degradation when thermosonication is applied.