Inactivation Of Oxidative Enzymes Research Articles

Inactivation of Oxidative Enzymes Using UV-C LEDs and Sensory Quality Assessment Using E-Nose and E-Tongue in Tender Coconut Water

Inactivation of Oxidative Enzymes Using UV-C LEDs and Sensory Quality Assessment Using E-Nose and E-Tongue in Tender Coconut Water

Emerging biotechnologies and non-thermal technologies for winemaking in a context of global warming.

In the current situation, wine areas are affected by several problems in a context of global warming: asymmetric maturities, pH increasing, high alcohol degree and flat wines with low freshness and poor aroma profile. The use of emerging biotechnologies allows to control or manage such problems. Emerging non-Saccharomyces as Lachancea thermotolerans are very useful for controlling pH by the formation of stable lactic acid from sugars with a slight concomitant alcohol reduction. Lower pH improves freshness increasing simultaneously microbiological stability. The use of Hanseniaspora spp. (specially H. vineae and H. opuntiae) or Metschnikowia pulcherrima promotes a better aroma complexity and improves wine sensory profile by the expression of a more complex metabolic pattern and the release of extracellular enzymes. Some of them are also compatible or synergic with the acidification by L. thermotolerans, and M. pulcherrima is an interesting biotool for reductive winemaking and bioprotection. The use of bioprotection is a powerful tool in this context, allowing oxidation control by oxygen depletion, the inhibition of some wild microorganisms, improving the implantation of some starters and limiting SO2. This can be complemented with the use of reductive yeast derivatives with high contents of reducing peptides and relevant compounds such as glutathione that also are interesting to reduce SO2. Finally, the use of emerging non-thermal technologies as Ultra High-Pressure Homogenization (UHPH) and Pulsed Light (PL) increases wine stability by microbial control and inactivation of oxidative enzymes, improving the implantation of emerging non-Saccharomyces and lowering SO2 additions. GRAPHICAL ABSTRACT.

Instant controlled pressure-drop assisted pressing for defatting and dewatering of yellow mealworm larvae: process study and optimisation

Insects are gaining interest as a sustainable and highly nutritious source of proteins and lipids for food and feed production sectors. Insect bio-refinery includes lipid extraction by pressing, dewatering, microbiological decontamination, and protein fractionation. The present study is experimenting the use of instant controlled pressure-drop (DIC), an emerging technology, for treating yellow mealworms and evaluating its combined effects on insect bio-refinery steps. A preliminary study allowed identifying the optimal hydraulic pressing conditions forTenebrio molitor larvae. Then, establishing an experimental design with DIC operative parameters of the saturated dry steam absolute pressure and treatment time ranging between (0.15 and 0.45 MPa) and (15 and 35 s), respectively, allowed identifying the DIC impact as a pretreatment on different larvae properties. It was possible to identify the optimal pressing parameters at 6 MPa, 60 °C, 2 cm of thickness, and 0.15 mm/s as initial piston speed. Moreover, DIC performed at 0.15 MPa for 25 seconds stood as an efficient killing method. Thanks to the changes in the membrane’s structure it provokes, DIC treatment modified larvae properties, ensured a partial expulsion of the matter (up to 0.47 g/g dry basis (db)), and resulted in larval expansion (up to 67%) which resulted in a decrease in the apparent density. As for the chemical properties, the larvae and larvae juice colours were found to become lighter as we increased the treatment conditions, which might be caused by the inactivation of oxidative enzymes. Moreover, severe DIC operative parameters decreased the pressing yields from 68 to 55%, possibly caused by protein aggregation and denaturation phenomena that prevent molecules from coming out by pressing. However, the water activity and moisture, lipid, and protein contents remained unaffected.

Alternating current electric field inhibits browning of Pleurotus ostreatus via inactivation of oxidative enzymes during postharvest storage

Oyster mushrooms (Pleurotus ostreatus, P. ostreatus) are rich in nutrients and have a pleasant flavour. However, they brown easily during storage, reducing consumer acceptance and decreasing market value. The present study was aimed at assessing the inhibitory effect of an alternating current electric field (ACEF) on the browning of oyster mushrooms and the possible mechanisms involved. Results revealed that treatment of P. ostreatus mushrooms with an ACEF (600 kV/m, 50 Hz, 120 min) reduced the browning of oyster mushrooms by 40% after 12 d of storage, and the effect was closely related to the inactivation of polyphenol oxidase, the delay of electrolyte leakage, and lower malondialdehyde levels that may be a consequence of decreased lipoxygenase activity. In conclusion, ACEF treatment can increase the quality of P. ostreatus during storage by delaying browning.

S‐Nitrosation and denitrosation of proteins by variation of superoxide/nitric oxide ratio – implications for prevention of sulfoxidation‐dependent enzyme inactivation during ischemia/reperfusion

Oxidative stress plays a key role for the development of cardiovascular, metabolic and neurodegenerative disease. This concept was never widely proven by the therapeutic use of classical antioxidants in large scale clinical trials. However, we know from numerous (pre)clinical studies that the formation of reactive oxygen and nitrogen species (RONS) as well as stable oxidative stress markers are a hallmark of most forms of diseases and higher oxidative stress markers are frequently associated with higher disease risk and mortality. Besides the detrimental role of RONS, they are also involved in cellular functions via redox signalling. We have previously identified an efficient mechanism of S‐nitrosation by low levels of nitric oxide and superoxide (3:1 ratio) with potential formation of N2O2 [Daiber A, Schildknecht S, Müller J, Kamuf J, Bachschmid MM, Ullrich V. Chemical model systems for cellular nitros(yl)ation reactions. Free Radic Biol Med. 2009 Aug 15;47(4):458–67.]. Here we, elucidated whether S‐nitrosation in the presence of higher nitric oxide than superoxide concentrations (as observed under hypoxic conditions) could prevent sulfoxidation and thereby oxidative inactivation of enzymes in the presence of higher superoxide than nitric oxide concentrations (as observed during reoxygenation). We found that increasing concentrations of xanthine oxidase/hypoxanthine caused conversion of S‐nitrosoglutathione (GSNO) to reduced glutathione (GSH) up to a certain concentration of xanthine oxidase, indicating that superoxide can induce denitrosation of GSNO. This finding was unexpected since in the presence of excess superoxide one would not expect regeneration of reduced GSH from GSNO. This was even more surprising since we observed substantial dihydrorhodamine oxidation that was prevented by uric acid and tyrosine nitration of albumin during denitrosation of GSNO by superoxide, all of which points to intermediary formation of peroxynitrite. In summary, we propose that S‐nitrosation of (mitochondrial) proteins during ischemia represents a protective mechanism to prevent irreversible overoxidation of thiols during the reperfusion phase and to re‐establish reduced thiol state in (mitochondrial) key enzymes of energy metabolism and cell survival. Wide‐spread mitochondrial protein S‐nitrosation may represent a central feature of the protective preconditioning effects of nitric oxide.Support or Funding InformationThe present work was supported by the European Cooperation in Science and Technology (COST Action BM1203/EU‐ROS and COST Action CA16225/EU‐CARDIOPROTECTION).

The study of bas complex in chlorophyll­containing vegetables and development of health­improving nanoproducts by a deep processing method

The BAS complex was determined in chlorophyll-containing vegetables (broccoli, spinach, Brussels sprouts, green beans). Presence of the BAS complex (chlorophyll, phenolic compounds, L-ascorbic acid, β-carotene) in 100 grams of fresh CCV in a quantity capable of satisfying the daily demand of the human body was established. It was found that in comparison with boiling in conventional equipment, steam thermal treatment of CCV in an automatic steam convection oven proceeds at a more intensive inactivation of oxidative enzymes. It was shown that a complete inactivation of enzymes occurs after 10 minutes of steam thermal treatment of CCV. Health-improving nanoproducts with a high content of chlorophyll were developed. A combined action on the raw materials of the processes of steam thermal treatment and mechanolysis with the use of a new generation of equipment for heat treatment and fine-dispersed shredding was used for the first time. Conditions of steam thermal treatment of CCV were established in which not only preservation of a and b chlorophylls and β-carotene but also thermal destruction and extraction from hidden forms take place. In comparison with fresh CCV, a 1.33...1.4 times larger mass fraction of chlorophyll and a 2-fold increase in β-carotene were observed. The mechanism of this process involves inactivation of oxidative enzymes and thermal destruction of hydrogen and other bonds between hidden forms of chlorophylls in nanocomplexes and proteins and polysaccharides. It has been established that significantly greater effect of extraction of hidden BAS forms occurred when using fine shredding of thermally treated chlorophyll-containing vegetables. Increase in chlorophyll and β-carotene content was 2.0...2.1 and 2.0...3.3 times, respectively, in the case of production of fine-dispersed CCV purees. With the help of the innovations used, it was possible to establish existence of hidden forms of chlorophylls and carotenoids and transform the product into an easily digestible nanoform. It has been shown that quality of fine-dispersed purees prepared from CCV with the use of these innovations exceeds quality of the starting raw material. Based on fine-dispersed CCV purees, a wide range of health-improving food products were developed. The products are in an easily digestible nanosized form. Thick soups, nanodrinks, nanosorbets, dressings sauces have been developed, their quality was studied and a comparison with counterparts made. It has been established that new types of products made from chlorophyll-containing vegetables exceed existing counterparts in the content of the BAS complex (chlorophyll, ascorbic acid, β-carotene, phenolic compounds, etc.). One portion of the product contains from 1/3 to the daily person’s demand of BAS. The BAS content in the obtained nanoproducts can be included to the health-improving products and recommended for immunizing people.

Pulsed electric fields (PEF) applications on wine production: A review

Novel techniques have been searched in the last decades as a result of increasing demand for high quality food products. Non-thermal processing technologies, such as pulsed electric fields (PEF) have been improved to achieve inhibition of deleterious effects on quality-related compounds. The working principle of PEF is based on the application of pulses of high voltage (typically above 20 kV/cm up to 70 kV/cm) to liquid foods placed between two electrodes. Pulsed electric fields technique has also been studied in winemaking process. Certain positive influences of PEF on vinification have been reported as elimination of pathogenic microorganisms, reduction of maceration time, increase in phenolic compounds extraction , acceleration of wine aging and inactivation of oxidative enzymes. The aim of this review is to summarize the potential applications of PEF in winemaking and to express its effects on quality of wine.

Deep processing of carotene-containing vegetables and obtaining nanofood with the use of equipment of new generation

We proposed and designed a new method of deep processing of carotene­containing vegetables – alternative to cryogenic treatment, based on the comprehensive action of steam thermal treatment and finely dispersed grinding on raw materials using a new generation of equipment that is applied in restaurant business, which makes it possible to more fully utilize biological potential (2...3 times higher than in the original raw materials). It was found that during deep (steam convection) processing of carotene­containing vegetables (carrot and pumpkin) with the use of modern steam convection equipment, the fermentative processes proceed with less intensity than during traditional method of thermal treatment – blanching by immersion in boiling water. The quantitative indicator of the maximum fermentative activity during treatment of the carotene­containing vegetables in a combi steamer, compared to blanching, is 2–4,5 times less for polyphenol oxidase, by 3 times for peroxidase. It was demonstrated that the complete inactivation of oxidative enzymes during thermal treatment of carotene­containing vegetables in a combi steamer occurs earlier than during blanching and takes place in 20 minutes, which is 10–15 minutes faster than at blanching. The complete inactivation of oxidative enzymes during blanching of carotene­containing vegetables occurs in 30–35 minutes. It was demonstrated that, compared with fresh raw materials, during thermal treatment of carotene­containing vegetables (carrot, pumpkin) in a combi steamer (under the above­mentioned modes), not only the preservation of b­carotene is achieved in 10 minutes, but also the increase in its mass by 2...2,3 times that occurs due to the release from the hidden state (forms, associated with biopolymers) to free form that is registered by the chemical methods of research. It was found that the loss of vitamin C during thermal treatment of carotene­containing vegetables in a combi steamer is much lower than at blanching. Thus, after 20 minutes of thermal treatment in the combi steamer, the mass fraction of L­ascorbic acid remained by 65…80 %, while after blanching by 40…50 %. It was also demonstrated that after steam thermal treatment and finely dispersed grinding of carotene­containing vegetables when making puree, a significant increase in the extraction of L­ascorbic acid and b­carotene occurs in comparison to the original raw materials, which is 2 and 3 times larger for pumpkin, respectively, and for carrot – 1,7 and 2,5 times, respectively. It was found that the comprehensive application of steam thermal treatment of vegetable raw materials in a combi steamer with finely dispersed grinding makes it possible to obtain puree, the quality of which is close to the quality of the puree, obtained using the cryogenic product treatment (in particular, the content of b­carotene is 2,5…3 times during steam thermal treatment and is 2,8...3,5 times during cryogenic treatment).

Inactivation of Oxidative Enzymes by High-Intensity Pulsed Electric Field for Retention of Color in Carrot Juice

The effects of high-intensity pulsed electric fields (HIPEF) on oxidative enzymes and color of fresh carrot juice were studied. A response surface methodology (RSM) was used to evaluate the effect of pulse polarity (mono or bipolar mode), pulse width (from 1 to 7 μs), and pulse frequency (from 50 to 250 Hz) on color and peroxidase (POD) inactivation of carrot juice treated by HIPEF. The total treatment time and the electric field strength were set at 1,000 μs and 35 kV/cm, respectively, at a temperature below 35°C. The physicochemical characteristics of carrot juice were measured. There was a linear relationship between electrical conductivity and temperature of the carrot juice. The results showed that HIPEF-treated carrot juice at 35 kV/cm for 1,000 μs applying 6 μs pulse width at 200 Hz in bipolar mode led to 73.0% inactivation of POD. The color coordinates did not change significantly. Therefore, HIPEF was effective in POD inactivation and carrot juice color preservation.

Hydroperoxide inactivation of enzymes within spores of Bacillus megaterium ATCC19213

Hydroperoxide inactivation of the protoplast enzymes enolase, aldolase and glucose-6-phosphate dehydrogenase in intact spores of Bacillus megaterium ATCC19213 was assessed by first treating the cells with lethal levels of H 2O 2, then germinating them in the presence of chloramphenicol prior to permeabilization and enzyme assays. Glucose-6-phosphate dehydrogenase proved to be more sensitive to H 2O 2than enolase or aldolase, in agreement with findings for isolated enzymes. Average D values (time for 90% inactivation) for spores treated with 0.50% H 2O 2 were 173 min for enolase, 67 min for aldolase and 32 min for glucose-6-phosphate dehydrogenase, compared with a D value of 34 min for spore killing. H 2O 2 killing of spores was found to be conditional in that recoveries of survivors were greater on complex medium than on minimal medium. Overall, it appeared that oxidative inactivation of enzymes may be important for hydroperoxide killing of spores.

Hydroperoxide inactivation of enzymes within spores ofBacillus megateriumATCC19213

Hydroperoxide inactivation of the protoplast enzymes enolase, aldolase and glucose-6-phosphate dehydrogenase in intact spores of Bacillus megaterium ATCC19213 was assessed by first treating the cells with lethal levels of H2O2, then germinating them in the presence of chloramphenicol prior to permeabilization and enzyme assays. Glucose-6-phosphate dehydrogenase proved to be more sensitive to H2O2than enolase or aldolase, in agreement with findings for isolated enzymes. Average D values (time for 90% inactivation) for spores treated with 0.50% H2O2 were 173 min for enolase, 67 min for aldolase and 32 min for glucose-6-phosphate dehydrogenase, compared with a D value of 34 min for spore killing. H2O2 killing of spores was found to be conditional in that recoveries of survivors were greater on complex medium than on minimal medium. Overall, it appeared that oxidative inactivation of enzymes may be important for hydroperoxide killing of spores.

Oxidative modification of enzymes by stimulated neutrophils.

We have previously demonstrated that a variety of enzymic and non-enzymic mixed-function oxidation (MFO) systems catalyze the oxidative inactivation of E. coli glutamine synthetase (GS) and other key metabolic enzymes.1,2 Considerable evidence has been presented that the inactivation of GS correlates with the loss of a single histidine residue and is accompanied by the generation of a protein carbonyl derivative.3 Further oxidation renders the enzyme highly susceptible to known proteases4 as well as to a new class of nonlysomal proteases which exhibit selectivity for the oxidatively modified enzyme.5 These in vitro studies have suggested that oxidative inactivation of enzymes is a marking step for selective degradation of enzymes and is under metabolic control. We have subsequently undertaken studies to examine the possible physiological role of this process in biological systems, and one such system is activation of polymorphonuclear leukocytes (PMN, neutrophils).

Kinetics of ascorbic acid degradation in potato blanching

SummaryDegradation kinetics of ascorbic acid was investigated on potato strips wrapped in aluminium foil and blanched for 5–60 min at different temperatures between 65°C and 100°C. The results confirmed that first order kinetics is adequate in describing the degradation reaction. The value of the rate constant was found to pass through a maximum at 85–90°C, indicating the inactivation of oxidative enzymes around these temperatures. Comparison of the degradation losses based on the present investigation with results on total loss of ascorbic acid during blanching reported in the literature showed that thermal degradation accounts for a considerable portion of the total loss.

Factors affecting the toxicity of oxygen towards airborne coliform bacteria.

SUMMARY: The maximum bactericidal effect of oxygen on airborne coliform bacteria occurred at the lowest relative humidity tested. Escherichia coli commune and Klebsiella aerogenes were very much less sensitive than E. coli b and E. coli jepp.Only a small partial pressure of oxygen in a nitrogen-oxygen mixture at atmospheric pressure was required to produce the maximum effect. The oxygen toxicity for each bacterial strain was altered by changing the growth conditions or by including certain chemicals in the spray fluid. These chemicals are protective to freeze-dried bacteria and therefore inactivation of oxidative enzymes in freeze dried and airborne bacteria probably occur by similar mechanisms. The same oxidative enzymes in bacterial colonies were slightly inactivated by hyperbaric oxygen pressures.

Studies on the oxidative inactivation of enzymes

The activity of ribonuclease after treatment with hydrogen peroxide in a peroxide/enzyme ratio of 55,000 was determined at pH 5.00. Very little loss of activity was found under these conditions. Using a modified Kunitz method, the slope obtained in the presence of H 2O 2 was −0.072 ± 0.014 compared with a control of −0.086 ± 0.016 (The absolute value of the slope is a measure of enzyme activity.) The presence of 3-aminotriazole caused little effect on the activity in the presence of peroxide (slope −0.080 ± 0.016). These data, together with other information in the literature, suggest that denaturation of the enzyme is a necessary first step for complete inactivation of the enzyme by peroxide. A similar situation may prevail in the case of catalase. 3-Aminotriazole, a known inhibitor of catalase, was found to be unreactive to a series of twelve amino acids. 3-Aminotriazole (3-AT), however, did react with the oxidized form of cystine and cysteine. 3-AT was also found to react strongly with basic hemin alone (especially in the presence of hydrogen peroxide) and in the presence of histidine and acetate. From these data and other information in the literature, a mechanism for the inactivation of catalase caused by 3-AT and H 2O 2 is suggested.