Effects of combined pressure and temperature on enzymes related to quality of fruits and vegetables: from kinetic information to process engineering aspects

Emulsifying properties of egg proteins: Influencing factors, modification techniques, and applications

As an essential food ingredient with good nutritional and functional properties and health benefits, eggs are widely utilized in food formulations. In particular, egg proteins have good emulsification properties and can be commonly used in various food products, such as mayonnaise and baked goods. Egg protein particles can act as stabilizers for Pickering emulsions because they can effectively adsorb at the oil-water interface, reduce interfacial tension, and form a stable physical barrier. Due to their emulsifying properties, biocompatibility, controlled release capabilities, and ability to protect bioactive substances, egg proteins have become ideal carriers for encapsulating and delivering functional substances. The focus of this review is to summarize current advances in using egg proteins as emulsifiers. The effects of influencing factors (temperature, pH, and ionic strength) and various modification methods (physical, chemical, and biological modification) on the emulsifying properties of egg proteins are discussed. In addition, the application of egg proteins as emulsifiers in food products is presented. Through in-depth research on the emulsifying properties of egg proteins, the optimization of their applications in food, biomedical, and other fields can be achieved.

High Hydrostatic Pressure in the Modulation of Enzymatic and Organocatalysis and Life under Pressure: A Review

The interest in high hydrostatic pressure (HHP) is mostly focused on the inactivation of deleterious enzymes, considering the quality-related issues associated with enzymes in foods. However, more recently, HHP has been increasingly studied for several biotechnological applications, including the possibility of carrying out enzyme-catalyzed reactions under high pressure. This review aims to comprehensively present and discuss the effects of HHP on the kinetic catalytic action of enzymes and the equilibrium of the reaction when enzymatic reactions take place under pressure. Each enzyme can respond differently to high pressure, mainly depending on the pressure range and temperature applied. In some cases, the enzymatic reaction remains significantly active at high pressure and temperature, while at ambient pressure it is already inactivated or possesses minor activity. Furthermore, the effect of temperature and pressure on the enzymatic activity indicated a faster decrease in activity when elevated pressure is applied. For most cases, the product concentration at equilibrium under pressure increased; however, in some cases, hydrolysis was preferred over synthesis when pressure increased. The compiled evidence of the effect of high pressure on enzymatic activity indicates that pressure is an effective reaction parameter and that its application for enzyme catalysis is promising.

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.

Production and Purification of Novel Hypocholesterolemic Peptides from Lactic Fermented Spirulina platensis through High Hydrostatic Pressure-Assisted Protease Hydrolysis

This research focuses on the proteolytic capacity of Spirulina platensis and their hypocholesterolemic activity via the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR) inhibitory activity. To select suitable proteases for releasing peptides with high HMGR-inhibiting activity from S. platensis, eight commonly used commercial proteases were used in protease hydrolysis under high hydrostatic pressure (HHP, 100 MPa or 0.1 MPa) at 50 °C for 24 h. The Peptidase R group had the highest inhibitory capacity (67%). First, S. platensis was fermented with seven mixed lactic acid bacteria for 5 h at 42 °C. This was followed by the addition of Peptidase R under high hydrostatic pressure (100 MPa at 50 °C) for 0–6 h of enzymatic hydrolysis (HHP-FH-PR6) to determine the hydrolytic capacity of S. platensis protein. As the hydrolysis time extended to 6 h, the peptide content increased from 96.8 mg/mL to 339.8 mg/mL, and the free amino acid content increased from 24 mg/mL to 115.2 mg/mL, while inhibition of HMGR increased from 67.0% to 78.4%. In an experimental simulation of in vitro gastrointestinal digestion, the IC50 of HHP-FH-PR6G on HMGR was 3.5 μg peptide/mL. Peptides with inhibitory activity on HMGR were purified, and their sequences were identified as Arg-Cys-Asp and Ser-Asn-Val (IC50: 6.9 and 20.1 μM, respectively).

Standardized ileal amino acid digestibility of protein sources for broiler chickens is influenced by the feed form

The aim of present study was to determine the influence of the feed form (FF) on standardized ileal digestibility (SID) of nitrogen (N) and amino acids (AA) in 3 protein sources (PS) for broiler chickens. Six diets were tested in a 3 × 2 factorial arrangement of treatments involving 3 PS (meat and bone meal [MBM], soybean meal [SBM], and canola meal [CM]) in mash and pelleted forms. The basal endogenous N and AA losses were determined by offering a N-free diet in the mash form. From day 1 to 18, the birds were offered a broiler starter diet. The diets and the N-free diet were randomly assigned to 6 replicate cages (8 birds per cage) and fed from day 19 to 23. The ileal digesta were collected on day 23. The SID of N was higher (P < 0.05) in SBM followed by MBM and CM. The average SID of AA in SBM and MBM were similar (P > 0.05), and greater (P < 0.05) than that in CM. The FF had no influence (P > 0.05) on the SID of indispensable AA, the only exception being His, which was reduced (P < 0.05) by pelleting. Pelleting, however, resulted in reduction (P < 0.001) in the SID of all dispensable AA and average of AA. The AA most affected by pelleting was Cys, with a 15.4% decrease in the SID. The standardized ileal digestible contents of protein and the average of indispensable AA and dispensable AA were higher in MBM than in SBM, with CM being the lowest. Pelleting decreased (P < 0.05) the digestible protein and total digestible AA contents. These findings reveal that the FF has a substantial impact on AA digestibility estimates of feed ingredients and it must be considered in AA digestibility assays of ingredients with high protein and AA contents.

Effect of different drying temperatures on the rehydration of the fruiting bodies of Yu Muer (Auricularia cornea) and screening of browning inhibitors

In this study, the color of the dry fruiting bodies, fresh weight (FW): dry weight (DW) ratio, amino acids, and total phenolics, which are of nutritional or commercial interest, were compared among different drying temperature treatments. The effect of rehydration methods and color protection reagents on the fruiting body color, polyphenol oxidase (PPO) activity, and browning inhibition rate were evaluated. The results showed that drying with hot air at 65℃ was quickest and resulted in a better color without compromising the FW:DW ratio and rehydration ratio of the fruiting bodies. Furthermore, some reactions that occurred under high temperatures increased the content of protein, amino acids, and total phenolics. Soaking after boiling was the most suitable rehydration method, leading to the lowest PPO activity (39.87 ± 1.35 U/g). All of the four analyzed color protection reagents could significantly inhibit the browning of Yu Muer fruiting bodies under room temperature water rehydration conditions, with a citric acid content of 6 g/L showing the best performance. These results provide technical support for the development of the Yu Muer industry and for promoting the commercial processing of Yu Muer fruiting bodies slices.

The Effect of High Pressure Processing on Polyphenol Oxidase Activity, Phytochemicals and Proximate Composition of Irish Potato Cultivars

Polyphenol oxidase (PPO) activity, proximate composition, and phytochemicals were determined in four common Irish potato cultivars following a high pressure processing (HPP) at 600 MPa for 3 min. PPO activity was significantly (p < 0.05) lower in all HPP treated samples, while the overall proximate composition was not affected. The total phenolic content was significantly higher in the HPP treated samples. Chlorogenic acid levels significantly decreased with simultaneous increase of caffeic acid and p-coumaric acid levels upon HPP treatment. No significant changes were observed in rutin and ferulic acid levels, although their levels varied, depending on the potato cultivars, while the levels of cytotoxic glycoalkaloids (α-solanine and α-chaconine) remained unaltered.

In vitro oral processing of raw tomato: Novel insights into the role of endogenous fruit enzymes

During consumption of fruits, the breakdown of the fruit tissue due to oral processing (chewing, mixing with saliva) may activate or increase the rate of endogenous enzyme activities via the disruption of the cell wall, cellular decompartmentalization, and particle size reduction allowing the enzymes to reach their substrates. The aim of this study was to investigate the activity of one such endogenous fruit enzyme (pectin methylesterase [PME] [E.C. 3.1.1.11]) during in vitro oral processing of raw tomatoes and associated changes in viscosity and microstructure. Oral processing of tomatoes purees was examined in the presence of artificial saliva (AS) at 37°C. in vitro oral processing was followed using immunofluorescence microscopy, apparent viscosity measurements, spectrophotometric, and titrimetric techniques. The results demonstrated that PME had slight but significant activity in the tomato fruit during in vitro oral processing generating methanol as a function of oral processing time, which was further evidenced using immunolabeling techniques to detect methylated pectin epitopes. A significant shear-thinning behavior of the tomato puree was observed due to dilution and/or endogenous fruit enzyme activity. These results suggest that activity of other fruit enzymes, such as polygalacturonase, which catalyzed the depolymerization of unmethylated pectin chains, might have resulted in a decrease in viscosity, which compensated for the increased potential for gel formation (if any) caused by PME. These interesting insights into the role of endogenous fruit enzymes might pave the way to the understanding of fruit viscosity modification occurring in the mouth and help in rational design of new fruit-based products.

Anti-Inflammatory and Antioxidant Properties of Peptides Released from β-Lactoglobulin by High Hydrostatic Pressure-Assisted Enzymatic Hydrolysis

Background: β-lactoglobulin hydrolysates (BLGH) have shown antioxidant, antihypertensive, antimicrobial, and opioid activity. In the current study, an innovative combination of high hydrostatic pressure and enzymatic hydrolysis (HHP–EH) was used to increase the yield of short bioactive peptides, and evaluate the anti-inflammatory and antioxidant properties of the BLGH produced by the HHP–EH process. Method: BLG was enzymatically hydrolyzed by different proteases at an enzyme-to-substrate ratio of 1:100 under HHP (100 MPa) and compared with hydrolysates obtained under atmospheric pressure (AP-EH at 0.1 MPa). The degree of hydrolysis (DH), molecular weight distribution, and the antioxidant and anti-inflammatory properties of hydrolysates in chemical and cellular models were evaluated. Results: BLGH obtained under HHP–EH showed higher DH than the hydrolysates obtained under AP-EH. Free radical scavenging and the reducing capacity were also significantly stronger in HHP-BLGH compared to AP-BLGH. The BLGH produced by alcalase (Alc) (BLG-Alc) showed significantly higher antioxidant properties among the six enzymes examined in this study. The anti-inflammatory properties of BLG-HHP-Alc were observed in lipopolysaccharide-stimulated macrophage cells by a lower level of nitric oxide production and the suppression of the synthesis of pro-inflammatory cytokines. Peptide sequencing revealed that 38% of the amino acids in BLG-HHP-Alc are hydrophobic and aromatic residues, which contribute to its anti-inflammatory properties. Conclusions: Enzymatic hydrolysis of BLG under HHP produces a higher yield of short bioactive peptides with potential antioxidant and anti-inflammatory effects.

Anti-Inflammatory and Antioxidant Properties of Casein Hydrolysate Produced Using High Hydrostatic Pressure Combined with Proteolytic Enzymes

Casein-derived peptides are shown to possess radical scavenging and metal chelating properties. The objective of this study was to evaluate novel anti-inflammatory properties of casein hydrolysates (CH) produced by an eco-friendly process that combines high hydrostatic pressure with enzymatic hydrolysis (HHP-EH). Casein was hydrolysed by different proteases, including flavourzyme (Fla), savinase (Sav), thermolysin (Ther), trypsin (Try), and elastase (Ela) at 0.1, 50, 100, and 200 MPa pressure levels under various enzyme-to-substrate ratios and incubation times. Casein hydrolysates were evaluated for the degree of hydrolysis (DH), molecular weight distribution patterns, and anti-inflammatory properties in chemical and cellular models. Hydrolysates produced using HHP-EH exhibited higher DH values and proportions of smaller peptides compared to atmospheric pressure-enzymatic hydrolysis (AP-EH). Among five enzymes, Fla-digested HHP-EH-CH (HHP-Fla-CH) showed significantly higher antioxidant properties than AP-Fla-CH. The anti-inflammatory properties of HHP-Fla-CH were also observed by significantly reduced nitric oxide and by the suppression of the synthesis of pro-inflammatory cytokines in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) revealed that 59% of the amino acids of the peptides in HHP-Fla-CH were composed of proline, valine, and leucine, indicating the potential anti-inflammatory properties. In conclusion, the HHP-EH method provides a promising technology to produce bioactive peptides from casein in an eco-friendly process.

Physical, Chemical and Biochemical Modifications of Protein-Based Films and Coatings: An Extensive Review

Protein-based films and coatings are an interesting alternative to traditional petroleum-based materials. However, their mechanical and barrier properties need to be enhanced in order to match those of the latter. Physical, chemical, and biochemical methods can be used for this purpose. The aim of this article is to provide an overview of the effects of various treatments on whey, soy, and wheat gluten protein-based films and coatings. These three protein sources have been chosen since they are among the most abundantly used and are well described in the literature. Similar behavior might be expected for other protein sources. Most of the modifications are still not fully understood at a fundamental level, but all the methods discussed change the properties of the proteins and resulting products. Mastering these modifications is an important step towards the industrial implementation of protein-based films.

Kinetics of Thermal Inactivation of Peroxidase and Color Degradation of African Cowpea (Vigna unguiculata) Leaves

Cowpea leaves form an important part of the diet for many Kenyans, and they are normally consumed after a lengthy cooking process leading to the inactivation of peroxidase (POD) that could be used as an indicator for the potential shelf life of the vegetables. However, color degradation can simultaneously occur, leading to poor consumer acceptance of the product. The kinetics of POD in situ thermal (for thermal treatments in the range of 75 to 100 °C/120 min) inactivation showed a biphasic first-order model, with Arrhenius temperature dependence of the rate constant. The kinetic parameters using a reference temperature (Tref ) of 80 °C were determined for both the heat-labile phase (kref = 11.52 ± 0.95 × 10(-2) min(-1) and Ea of 109.67 ± 6.20 kJ/mol) and the heat-stable isoenzyme fraction (kref = 0.29 ± 0.07 × 10(-2) min(-1) and Ea of 256.93 ± 15.27 kJ/mol). Color degradation (L*, a*, and b* value) during thermal treatment was investigated, in particular as the "a*" value (the value of green color). Thermal degradation (thermal treatments between 55 and 80 °C per 90 min) of the green color of the leaves followed a fractional conversion model and the temperature dependence of the inactivation rate constant can be described using the Arrhenius law. The kinetic parameters using a reference temperature (TrefC = 70 °C) were determined as krefC = 13.53 ± 0.01 × 10(-2) min(-1) and EaC = 88.78 ± 3.21 kJ/mol. The results indicate that severe inactivation of POD (as an indicator for improved shelf life of the cooked vegetables) is accompanied by severe color degradation and that conventional cooking methods (typically 10 min/100 °C) lead to a high residual POD activity suggesting a limited shelf life of the cooked vegetables.

High-Pressure Inactivation of Enzymes: A Review on Its Recent Applications on Fruit Purees and Juices

In the last 2 decades high-pressure processing (HPP) has established itself as one of the most suitable nonthermal technologies applied to fruit products for the extension of shelf-life. Several oxidative and pectic enzymes are responsible for deterioration in color, flavor, and texture in fruit purees and juices (FP&J). The effect of HPP on the activities of polyphenoloxidase, peroxidase, β-glucosidase, pectinmethylesterase, polygalacturonase, lipoxygenase, amylase, and hydroperoxide lyase specific to FP&J have been studied by several researchers. In most of the cases, partial inactivation of the target enzymes was possible under the experimental domain, although their pressure sensitivity largely depended on the origin and their microenvironmental condition. The variable sensitivity of different enzymes also reflects on their kinetics. Several empirical models have been established to describe the kinetics of an enzyme specific to a FP&J. The scientific literature in the last decade illustrating the effects of HPP on enzymes in FP&J, enzymatic action on those products, mechanism of enzyme inactivation during high pressure, their inactivation kinetics, and several intrinsic and extrinsic factors influencing the efficacy of HPP is critically reviewed in this article. In addition, process optimization of HPP targeting specific enzymes is of great interest from an industrial approach. This review will give a fair idea about the target enzymes specific to FP&J and the optimum conditions needed to achieve sufficient inactivation during HPP treatment.

High-pressure processing of berry and other fruit products: implications for bioactive compounds and food safety

Fruits contain a variety of nutrients and polyphenols that are associated with health benefits. Year-round availability of fresh fruits is limited due to perishability. Processing fruits extends shelf life. Individual quick-frozen fruit is the most common for fruits, but nowadays, processing fruits into beverages offers extended shelf life and new market opportunities. Conventional thermal processing is an effective method for producing safe, extended shelf life, and shelf-stable products, including beverages. However, the high temperatures negatively affect nutritive quality by destroying essential nutrients and biologically active "non-essential" components such as polyphenols. Therefore, novel technologies that can preserve nutrient quality while ensuring food safety are warranted. In this review, the application of high-pressure processing (HPP) for preserving nutrients and phytochemicals while ensuring microbiological safety in beverages and other foods containing fruits is discussed.

Effect of ultrasound and high hydrostatic pressure (US/HHP) on the degradation of dextran catalyzed by dextranase

In our current research work, the effect of combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) on the enzymatic activity and enzymatic hydrolysis kinetic parameters of dextran catalytic by dextranase were investigated. Furthermore, the effects of US/HHP on the structure of dextranase were also discussed with the aid of fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The maximum hydrolysis of dextran was observed under US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 25 min), in which the hydrolysis of dextran increased by 163.79% compared with the routine thermal incubation at 50 °C. Results also showed that, Vmax and KM values, as well as, kcat of dextranase under US/HHP treatment were higher than that under US, HHP and thermal incubation at 50 °C, indicated that, the substrate is converted into the product at an increased rate when compared with the incubation at 50 °C. Compared to the enzymatic reaction under US, HHP, and routine thermal incubation, dextranase enzymatic reaction under US/HHP treatment showed decreases in Ea, ΔG and ΔH, however small increase in ΔS value was observed. In addition, fluorescence and CD spectra reflected that US/HHP treatment had increased the number of tryptophan on dextranase surface with increased α-helix by 19.80% and reduced random coil by 6.94% upon US/HHP-treated dextranase protein compared to the control, which were helpful for the improvement of its activity. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the hydrolysis of dextran in many industrial applications including sugar manufacturing processes.

The stability of almond β-glucosidase during combined high pressure-thermal processing: a kinetic study

The thermal and the combined high pressure-thermal inactivation kinetics of almond β-glucosidase (β-D-glucoside glucohydrolase, EC 3.2.1.21) were investigated at pressures from 0.1 to 600 MPa and temperatures ranging from 30 to 80 °C. Thermal treatments at temperatures higher than 50 °C resulted in significant inactivation with complete inactivation after 2 min of treatment at 80 °C. Both the thermal and high pressure inactivation kinetics were described well by first-order model. Application of pressure increased the inactivation kinetics of the enzyme except at moderate temperatures (50 to 70 °C) and pressures between 0.1 and 100 MPa where slight pressure stabilisation of the enzyme against thermal denaturation was observed. The activation energy for the inactivation of the enzyme at atmospheric pressure was estimated to be 216.2±8.6 kJ/mol decreasing to 55.2±3.9 kJ/mol at 600 MPa. The activation volumes were negative at all temperature conditions excluding the temperature-pressure range where slight pressure stabilisation was observed. The values of the activation volumes were estimated to be -29.6±0.6, -29.8±1.7, -20.6±3.2, -41.2±4.8, -36.5±1.8, -39.6±4.3, -31.0±4.5 and -33.8±3.9 cm3/mol at 30, 35, 40, 45, 50, 60, 65 and 70 °C, respectively, with no clear trend with temperature. The pressure-temperature dependence of the inactivation rate constants was well described by an empirical third-order polynomial model.