High pressure enhancement of enzymes: A review

ACE-inhibitory and antioxidant peptides from coconut cake albumin hydrolysates: purification, identification and synthesis

Coconut cake albumin was hydrolysed by sequential digestion with alcalase, flavourzyme, pepsin and trypsin to purify bioactive peptides with ACE-inhibitory and antioxidant activities. Following fractionation with sequential ultrafiltration, Sephadex gel chromatography and RP-HPLC, three novel peptides KAQYPYV, KIIIYN and KILIYG were identified. KAQYPYV, KIIIYN and KILIYG provided an IC₅₀ value of 37.06 μM, 58.72 μM and 53.31 μM on ACE-inhibitory activity, respectively. For hydroxyl radical scavenging activity, KAQYPYV, KIIIYN and KILIYG demonstrated an IC₅₀ value of 70.84 μM, 77.62 μM and 95.23 μM, respectively. All the three peptides exhibited a mixed modality of noncompetitive and uncompetitive inhibition on ACE and KAQYPYV showed good stability against gastrointestinal enzymes digestion. Moreover, these peptides could effectively lower intracellular endothelin-1 content without significant cytotoxicity, and protected vascular endothelial cells from reactive oxygen species mediated damage. Furthermore, KAQYPYV, KIIIYN and KILIYG also demonstrated high ion chelating ability (62.13% ± 4.21%, 64.66% ± 5.51% and 69.82% ± 7.24% at 0.1 mg mL⁻¹, respectively) and considerable superoxide radical scavenging activity (39.30% ± 2.72%, 46.79% ± 1.70% and 51.16% ± 3.23% at 1.0 mg mL⁻¹, respectively). These results indicate that coconut cake albumin is a potential source of bioactive peptides possessing ACE-inhibitory and antioxidant activities.

Three ACE-inhibitory and antioxidant peptides were identified from enzymatic hydrolysates of coconut cake albumin in the current study.

Quality changes in high hydrostatic pressure and thermal pasteurized grapefruit juice during cold storage

This study evaluated the effects of high hydrostatic pressure (HHP) and thermal pasteurization (TP) on microbial counts, physicochemical properties, antioxidant characteristics, naringin and naringenin contents, and naringinase activity of grapefruit juice during 21 days cold storage period. Results showed that HHP and TP significantly decreased the total microbial, coliform, and yeast counts. No significant differences between HHP-treated grapefruit juice (600 MPa/5 min) and untreated fruit juice with respect to physicochemical properties such as total titratable acidity, pH, and total soluble solids was observed after 21 days of storage. Although HHP affected the colour and antioxidant characteristics of grapefruit juice, the extent of effect was significantly lower than that for TP-treated fruit juice. This demonstrated that HHP could better maintain the original flavour and quality of grapefruit juice compared to TP. In addition, 92% naringinase activity was maintained in HHP-600 group on Day 21, which increased the degradation of bitter naringin into non-bitter naringenin during the cold storage of grapefruit juice. In summary, HHP can simultaneously maintain the microbiological safety of grapefruit juice along with its original quality characteristics. HHP can effectively extend the storage period and safety during cold chain transport, and hence highly applicable in the grapefruit juice industry.

Emerging technologies for the pretreatment of lignocellulosic biomass

Pretreatment of lignocellulosic biomass to overcome its intrinsic recalcitrant nature prior to the production of valuable chemicals has been studied for nearly 200 years. Research has targeted eco-friendly, economical and time-effective solutions, together with a simplified large-scale operational approach. Commonly used pretreatment methods, such as chemical, physico-chemical and biological techniques are still insufficient to meet optimal industrial production requirements in a sustainable way. Recently, advances in applied chemistry approaches conducted under extreme and non-classical conditions has led to possible commercial solutions in the marketplace (e.g. High hydrostatic pressure, High pressure homogenizer, Microwave, Ultrasound technologies). These new industrial technologies are promising candidates as sustainable green pretreatment solutions for lignocellulosic biomass utilization in a large scale biorefinery. This article reviews the application of selected emerging technologies such as ionizing and non-ionizing radiation, pulsed electrical field, ultrasound and high pressure as promising technologies in the valorization of lignocellulosic biomass.

Lactobacillus reuteri growth and fermentation under high pressure towards the production of 1,3-propanediol

Lactobacillus reuteri is a lactic acid bacterium able to produce several relevant bio-based compounds, including 1,3-propanediol (1,3-PDO), a compound used in food industry for a wide range of purposes. The performance of fermentations under high pressure (HP) is a novel strategy for stimulation of microbial growth and possible improvement of fermentation processes. Therefore, the present work intended to evaluate the effects of HP (10-35 MPa) on L. reuteri growth and glycerol/glucose co-fermentation, particularly on 1,3-PDO production. Two different types of samples were used: with or without acetate added in the culture medium. The production of 1,3-PDO was stimulated at 10 MPa, resulting in enhanced final titers, yields and productivities, compared to 0.1 MPa. The highest 1,3-PDO titer (4.21 g L^-1) was obtained in the presence of acetate at 10 MPa, representing yield and productivity improvements of ≈ 11 and 12%, respectively, relatively to the same samples at 0.1 MPa. In the absence of acetate, 1,3-PDO titer and productivity were similar to 0.1 MPa, but the yield increased ≈ 26%. High pressure also affected the formation of by-products (lactate, acetate and ethanol) and, as a consequence, higher molar ratios 1,3-PDO:by-products were achieved at 10 MPa, regardless of the presence/absence of acetate. This indicates a metabolic shift, with modification of product selectivity towards production of 1,3-PDO. Overall, this work suggests that HP can be a useful tool to improve of 1,3-PDO production from glycerol by L. reuteri, even if proper process optimization and scale-up are still needed to allow its industrial application. It also opens the possibility of using this technology to stimulate other glycerol fermentations processes that are relevant for food science and biotechnology.

Modification of enzymes by use of high-pressure homogenization

High-pressure is an emerging and relatively new technology that can modify various molecules. High-pressure homogenization (HPH) has been used in several studies on protein modification, especially in enzymes used or found in food, from animal, plant or microbial resources. According to the literature, the enzymatic activity can be modulated under pressure causing inactivation, stabilization or activation of the enzymes, which, depending on the point of view could be very useful. Homogenization can generate changes in the structure of the enzyme modifying various chemical bonds (mainly weak bonds) causing different denaturation levels and, consequently, affecting the catalytic activity. This review aims to describe the various alterations due to HPH treatment in enzymes, to show the influence of high-pressure on proteins and to report the HPH effects on the enzymatic activity of different enzymes employed in the food industry and research.

A Chimeric Styrene Monooxygenase with Increased Efficiency in Asymmetric Biocatalytic Epoxidation

The styrene monooxygenase (SMO) system from Pseudomonas sp. consists of two enzymes (StyA and StyB). StyB catalyses the reduction of FAD at the expense of NADH. After the transfer of FADH2 from StyB to StyA, reaction with O2 generates FAD-OOH, which is the epoxidising agent. The wastage of redox equivalents due to partial diffusive transfer of FADH2 , the insolubility of recombinant StyB and the impossibility of expressing StyA and StyB in a 1:1 molar ratio reduce the catalytic efficiency of the natural system. Herein we present a chimeric SMO (Fus-SMO) that was obtained by genetic fusion of StyA and StyB through a flexible linker. Thanks to a combination of: 1) balanced and improved expression levels of reductase and epoxidase units, and 2) intrinsically higher specific epoxidation activity of Fus-SMO in some cases, Escherichia coli cells expressing Fus-SMO possess about 50 % higher activity for the epoxidation of styrene derivatives than E. coli cells coexpressing StyA and StyB as discrete enzymes. The epoxidation activity of purified Fus-SMO was up to three times higher than that of the two-component StyA/StyB (1:1, molar ratio) system and up to 110 times higher than that of the natural fused SMO. Determination of coupling efficiency and study of the influence of O2 pressure were also performed. Finally, Fus-SMO and formate dehydrogenase were coexpressed in E. coli and applied as a self-sufficient biocatalytic system for epoxidation on greater than 500 mg scale.

Inactivation kinetics, structural, and morphological modification of mango soluble acid invertase by high pressure processing combined with mild temperatures

The activity, structure and morphology of mango soluble acid invertase (SAI) were investigated after high pressure processing (HPP) combined with mild temperature at 50-600MPa and 40-50°C. The activity of mango SAI was efficiently reduced by HPP at 50MPa/45 and 50°C, or 600MPa/40, 45 and 50°C, while it was increased by 10-30% after HPP at 50-200MPa/40°C. Significant antagonistic effect of pressure and temperature on the activity of SAI was observed at 50-400MPa/50°C. The secondary structure of SAI was not influenced by HPP. However, its tertiary structure was modified by HPP, and severer modification occurred with higher pressure, higher temperature, and longer treatment time. Results of atomic force microscope suggested that HPP at 400MPa/50°C for 2.5min induced dissociation of SAI, and HPP at 600MPa/50°C for 30min resulted aggregation of SAI.

Impact of High Hydrostatic Pressure on the Shelling Efficacy, Physicochemical Properties, and Microstructure of Fresh Razor Clam (Sinonovacula constricta)

The effects of high hydrostatic pressure (HHP) treatments (200, 300, and 400 MPa for 1, 3, 5 and 10 min) on the shelling efficacy (the rate of shelling, the rate of integrity and yield of razor clam meat) and the physicochemical (drip loss, water-holding capacity, pH, conductivity, lipid oxidation, Ca²⁺ -ATPase activity, myofibrillar protein content), microbiological (total viable counts) and microstructural properties of fresh razor clam (Sinonovacula constricta) were investigated. HHP treatments significantly (P < 0.05) increased shelling efficiency, water-holding capacity, pH, conductivity, and lipid oxidation, and HHP-treated razor clam showed lower levels of microorganisms and drip loss than untreated razor clam. Levels of thiobarbituric acid reacting substances (TBA) in HHP-treated razor clam were greatly increased (up to 0.93 ± 0.09 mg MDA/kg at 400 MPa for 10 min) which was caused by the formation of hydroperoxides during HHP treatment. All HHP treatments were found to have adverse effects on the activity of Ca²⁺ -ATPase and the content of myofibrillar protein (MP), which might be due to the substantial damage to the tertiary structure of proteins at high pressure. Moreover, scanning electron microscopy (SEM) revealed the compaction of the muscle fibers and a decrease in the extracellular space with increasing pressure and holding time. This phenomenon was mainly correlated with the compaction of muscle fibers and denaturation, aggregation, and gelation of muscle protein triggered by high pressure. In general, HHP could be applied as a safe and effective nonthermal technology to produce high-quality shelled razor clam.

PRACTICAL APPLICATION

High hydrostatic pressure (HHP) is now well known as a nonthermal processing technology and becoming increasingly acknowledged. However, it has not been widely applied to shell seafood due to its uncertain influence on its quality and shelling property. This study could provide valuable information regarding the shelling efficacy, physicochemical properties, and microstructure of razor clam treated by HHP. And it demonstrated that HHP showed a positive impact on quality of razor clam treated by HHP.

High hydrostatic pressure processing affects the phenolic profile, preserves sensory attributes and ensures microbial quality of jabuticaba (Myrciaria jaboticaba) juice

BACKGROUND

Jabuticaba (Myrciaria jaboticaba) is a Brazilian fruit rich in phenolic compounds and much appreciated for its sweet and slightly tangy taste. However, the high perishability of this fruit impairs its economic exploitation, creating an opportunity for the development of innovative products, such as high hydrostatic pressure (HHP) processed juices. We investigated the effect of HHP (200, 350 and 500 MPa for 5, 7.5 and 10 min) on phenolic compounds, antioxidant activity and microbiological quality of jabuticaba juice and the effect of the most effective HHP condition on its sensory acceptance.

RESULTS

Pressurization increased total phenolic compound content (up to 38%) and antioxidant activity by FRAP assay (up to 46%), probably by increasing phenolic compound extractability due to tissue damage. Pressurization progressively decreased microbial counts, and colony growth was undetectable at pressures of 350 MPa or 500 MPa. With the exception of aroma, which was 10% lower in pressurized juice at 350 MPa for 7.5 min in relation to unprocessed juice, HHP did not affect sensory acceptance scores.

CONCLUSION

Our results show that HHP was effective in ensuring microbiological quality, increasing bioactive potential and maintaining overall acceptance of jabuticaba juice, reinforcing the potential application of this processing technology in bioactive-rich foods. © 2017 Society of Chemical Industry.

The effects of glycine, TMAO and osmolyte mixtures on the pressure dependent enzymatic activity of α-chymotrypsin

Different natural osmolytes modulate the pressure dependent enzyme kinetics in different ways.

High isostatic pressure and thermal processing of açaí fruit (Euterpe oleracea Martius): Effect on pulp color and inactivation of peroxidase and polyphenol oxidase

The present study evaluated the effect of high isostatic pressure (HIP) on the activity of peroxidase (POD) and polyphenol oxidase (PPO) from açaí. Açaí pulp was submitted to several combinations of pressure (400, 500, 600MPa), temperature (25 and 65°C) for 5 and 15min. The combined effect of HIP technology and high temperatures (690MPa by 2 and 5min at 80°C) was also investigated and compared to the conventional thermal treatment (85°C/1min). POD and PPO enzyme activity and instrumental color were examined after processing and after 24h of refrigerated storage. Results showed stability of POD for all pressures at 25°C, which proved to be heat-resistant and baro-resistant at 65°C. For PPO, the inactivation at 65°C was 71.7% for 600MPa after 15min. In general, the increase in temperature from 25°C to 65°C reduced the PPO relative activity with no changes in color. Although the thermal treatment and the HIP (690MPa) along with high temperature (80°C) reduced the PPO relative activity, and relevant darkening was observed in the processed samples. Thus, it can be concluded that POD is more baro-resistant than PPO in açaí pulp subjected to the same HIP processing conditions and processing at 600MPa/65°C for 5min may be an effective alternative for thermal pasteurization treatments.

Effect of high-pressure treatment on taste and metabolite profiles of ducks with two different vinasse-curing processes

The effect of high-pressure (HP) (0.1, 150 and 300MPa, 15min) on taste profiles of vinasse-cured ducks was investigated; the metabolite profiles were determined using ¹H NMR. HP at 150MPa increased the taste intensity of products compared with the controls, while HP at 300MPa did not further improve their taste compared with 150MPa treated samples. The metabonome of vinasse-cured ducks was dominated by 27 metabolites. HP increased amino acids, glucose, alkaloids and organic acids, but decreased inosine monophosphate and its derivatives, compared with the controls. The increments of metabolites in vinasse-dry-cured duck were higher than those in vinasse-wet-cured duck. The change of metabolites could be related to the enzyme activity, the degradations of proteins, sugars and nucleotides, and the permeation from vinasse-curing agents to duck meat. These findings suggest that 150MPa treatment was effective to improve the taste of vinasse-cured duck.

Coupled effects of salt and pressure on catalytic ability of Rhizopus chinensis lipase

BACKGROUND

Both high pressure and environmental factors could influence the catalytic abilities of enzymes. This work investigated coupled effects of pressure and salts on Rhizopus chinensis lipase (RCL) to provide significant information for its further applications.

RESULTS

The maximum activity of RCL was observed under 200 MPa at 40 °C. The highest activity was achieved at concentrations of 0.06-0.1 mol L^-1 for tested salts. The effect of monovalent cations on RCL activity followed the Hofmeister series (K⁺ > Na⁺ > Li⁺ ) at 0.1 MPa but the order of Na⁺ and K⁺ was changed under 200 MPa. Meanwhile, the effects of anions did not follow the Hofmeister series. KCl slightly improved the thermostability of RCL at moderate concentration. At 60 °C, LiCl only stabilised RCL at 0.1 mol L^-1 . The pre-transition unfolding point was shifted from 4.5 to 3.5 mol L^-1 with pressure increasing from 0.1 to 600 MPa. In addition, KCl could not change the lipase's extrinsic fluorescence evolution versus pressure.

CONCLUSION

Pressure and salts could improve catalytic ability and stability of RCL under appropriate conditions. The effect of high pressure on RCL was influenced by salts. Meanwhile salts cannot prevent high pressure-induced damage to RCL. © 2017 Society of Chemical Industry.

Effect of High-Pressure Treatment on Catalytic and Physicochemical Properties of Pepsin

For a long time, high-pressure treatment has been used to destroy the compact structures of natural proteins in order to promote subsequent enzymatic hydrolysis. However, there are few reports evaluating the feasibility of directly improving the catalytic capability of proteases by using high-pressure treatments. In this study, the effects of high-pressure treatment on the catalytic capacity and structure of pepsin were investigated, and the relationship between its catalytic properties and changes in its physicochemical properties was explored. It was found that high-pressure treatment could lead to changes of the sulfhydryl group/disulfide bond content, hydrophobicity, hydrodynamic radius, intrinsic viscosity, and subunit composition of pepsin, and the conformational change of pepsin resulted in improvement to its enzymatic activity and hydrolysis efficiency, which had an obvious relationship with the high-pressure treatment conditions.

Application and possible benefits of high hydrostatic pressure or high-pressure homogenization on beer processing: A review

Beer is the most consumed beverage in the world, especially in countries such as USA, China and Brazil.It is an alcoholic beverage made from malted cereals, and the barley malt is the main ingredient, added with water, hops and yeast. High-pressure processing is a non-traditional method to preserve food and beverages. This technology has become more interesting compared to heat pasteurization, due to the minimal changes it brings to the original nutritional and sensory characteristics of the product, and it comprises two processes: high hydrostatic pressure, which is the most industrially used process, and high-pressure homogenization. The use of high pressure almost does not affect the molecules that are responsible for the aroma and taste, pigments and vitamins compared to the conventional thermal processes. Thus, the products processed by high-pressure processing have similar characteristics compared to fresh products, including beer. The aim of this paper was to review what has been investigated about beer processing using this technology regarding the effects on physicochemical, microbiology and sensory characteristics and related issues. It is organized by processing steps, since high pressure can be applied to malting, mashing, boiling, filtration and pasteurization. Therefore, the beer processed with high-pressure processing may have an extended shelf-life because this process can inactivate beer spoilage microorganisms and result in a superior sensory quality related to freshness and preservation of flavors as it does to juices that are already commercialized. However, beyond this application, high-pressure processing can modify protein structures, such as enzymes that are present in the malt, like α- and β-amylases. This process can activate enzymes to promote, for example, saccharification, or instead inactivate at the end of mashing, depending on the pressure the product is submitted, besides being capable of isomerizing hops to raise beer bitterness. As a consequence, the process may reduce steam demand and residue generation. Therefore, the use of high-pressure processing can potentially replace or be combined with heat processes usually applied to beer, thus bringing benefits to the sensory quality of the product and to the environment.

Biophysical evaluation of milk-clotting enzymes processed by high pressure

High pressure processing (HPP) is able to promote changes in enzymes structure. This study evaluated the effect of HP on the structural changes in milk-clotting enzymes processed under activation conditions for recombinant camel chymosin (212MPa/5min/10°C), calf rennet (280MPa/20min/25°C), bovine rennet (222MPa/5min/23°C), and porcine pepsin (50MPa/5min/20°C) and under inactivation conditions for all enzymes (600MPa/10min/25°C) including the protease from Rhizomucor miehei. In general, it was found that the HPP at activation conditions was able to increase the intrinsic fluorescence of samples with high pepsin concentration (porcine pepsin and bovine rennet), increase significantly the surface hydrophobicity and induce changes in secondary structure of all enzymes. Under inactivation conditions, increases in surface hydrophobicity and a reduction of intrinsic fluorescence were observed, suggesting a higher exposure of hydrophobic sites followed by water quenching of Trp residues. Moreover, changes in secondary structure were observed (with minor changes seen in Rhizomucor miehei protease). In conclusion, HPP was able to unfold milk-clotting enzymes even under activation conditions, and the porcine pepsin and bovine rennet were more sensitive to HPP.

Characterization of a thermostable glycoside hydrolase (CMbg0408) from the hyperthermophilic archaeon Caldivirga maquilingensis IC-167

BACKGROUND

Hyperthermophilic archaea capable of functioning optimally at very high temperatures are a good source of unique and industrially important thermostable enzymes.

RESULTS

A glycoside hydrolase family 1 β-galactosidase gene (BglB) from a hyperthermophilic archaeon Caldivirga maquilingensis IC-167 was cloned and expressed in Escherichia coli. The recombinant enzyme (CMbg0408) displayed optimum activity at 110 °C and pH 5.0. It also retained 92% and 70% of its maximal activity at 115 and 120 °C, respectively. The enzyme was completely thermostable and active after 120 min of incubation at 80 and 90 °C. It also showed broad substrate specificity with activities of 8876 ± 185 U mg^-1 for p-nitrophenyl-β-d-galactopyranoside, 4464 ± 172 U mg^-1 for p-nitrophenyl-β-d-glucopyranoside, 1486 ± 68 U mg^-1 for o-nitrophenyl-β-d-galactopyranoside, 2250 ± 86 U mg^-1 for o-nitrophenyl-β-d-xylopyranoside and 175 ± 4 U mg^-1 for lactose. A catalytic efficiency (k_cat /K_m ) of 3059 ± 122 mmol L^-1  s^-1 and K_m value of 8.1 ± 0.08 mmol L^-1 were displayed towards p-nitrophenyl-β-d-galactopyranoside.

CONCLUSION

As a result of its remarkable thermostability and high activity at high temperatures, this novel β-galactosidase may be useful for food and pharmaceutical applications. © 2016 Society of Chemical Industry.

Influence of High Hydrostatic Pressure Technology on Wine Chemical and Sensorial Characteristics: Potentialities and Drawbacks

During last years, scientific research on high hydrostatic pressure (HHP) as a nonthermal processing technology for preservation or aging of wine has increased substantially. HHP between 200 and 500MPa is able to inactivate bacteria and yeasts in red and white wines, suggesting that it may be used for wine preservation. However, these treatments have been shown to promote changes on sensorial and physicochemical characteristics in both red and white wines, not immediately in the first month, but along storage. The changes are observed in wine color, aroma, and taste due mainly to reactions of phenolic compounds, sugars, and proteins. These reactions have been associated with those observed during wine aging, leading to aged-like wine characteristics perceived by sensorial analysis. This chapter will present the influence of HHP technology on wine chemical and sensorial characteristics, criticaly discussing its potentialities and drawbacks. The appropriate use of HHP, based on the scientific knowledge of the reactions occuring in wine promoted by HHP, will allow to exploit this technology for wine production achieving distinct characteristics to address particular market and consumer demands.

Pressure modulates the self-cleavage step of the hairpin ribozyme

The ability of certain RNAs, denoted as ribozymes, to not only store genetic information but also catalyse chemical reactions gave support to the RNA world hypothesis as a putative step in the development of early life on Earth. This, however, might have evolved under extreme environmental conditions, including the deep sea with pressures in the kbar regime. Here we study pressure-induced effects on the self-cleavage of hairpin ribozyme by following structural changes in real-time. Our results suggest that compression of the ribozyme leads to an accelerated transesterification reaction, being the self-cleavage step, although the overall process is retarded in the high-pressure regime. The results reveal that favourable interactions between the reaction site and neighbouring nucleobases are strengthened under pressure, resulting therefore in an accelerated self-cleavage step upon compression. These results suggest that properly engineered ribozymes may also act as piezophilic biocatalysts in addition to their hitherto known properties.

Impact of high hydrostatic pressure on bacterial proteostasis

High hydrostatic pressure (HHP) is an important factor that limits microbial growth in deep-sea ecosystems to specifically adapted piezophiles. Furthermore, HHP treatment is used as a novel food preservation technique because of its ability to inactivate pathogenic and spoilage bacteria while minimizing the loss of food quality. Disruption of protein homeostasis (i.e. proteostasis) as a result of HHP-induced conformational changes in ribosomes and proteins has been considered as one of the limiting factors for both microbial growth and survival under HHP conditions. This work therefore reviews the effects of sublethal (≤100MPa) and lethal (>100MPa) pressures on protein synthesis, structure, and functionality in bacteria. Furthermore, current understanding on the mechanisms adopted by piezophiles to maintain proteostasis in HHP environments and responses developed by atmospheric-adapted bacteria to protect or restore proteostasis after HHP exposure are discussed.

Using high hydrostatic pressures to retain the antioxidant compounds and to reduce the enzymatic activity of a pitaya-pineapple (Stenocereus sp.-Fragaria ananassa) beverage

Pitaya (Stenocereus sp.) is a fruit native to arid and semiarid areas of Mexico. It has high antioxidant activity mainly due to its contents of betalains and phenolics, but its consumption is limited due to very short shelf-life and not very recognized flavor. A beverage of pitaya and pineapple was formulated to improve sensory properties. A high hydrostatic pressure (HHP) study at 400-600 MPa and 25 °C for 2-10 min was applied in the beverage and the effect on the contents of vitamin C, total phenolics and betalains, and the pectin methylesterase (PME) activity of pitaya-pineapple beverages, was evaluated. The effect of the come up time (CUT) was also studied. Vitamin C contents increased from 5% at 600 MPa-CUT to 64% at 400 MPa/CUT. Total phenolic concentrations decreased (20-48%) at all processing conditions tested at 400 MPa/CUT, total betacyanins were retained. At 500 MPa/10 min losses of betaxanthins of up to 6% occurred. The maximum PME activity decrease was 23% at 600 MPa 5 min, but an increase of PME activity 7% was observed at 400 MPa/10 min. HHP seem to be a good option to retain most of the antioxidant compounds in pitaya-pineapple beverage, but more studies are necessary to inactivate PME.

The Effect of High Pressure Techniques on the Stability of Anthocyanins in Fruit and Vegetables

Anthocyanins are a group of phenolic compounds responsible for red, blue and violet colouration of many fruits, vegetables and flowers. The high content of these pigments is important as it influences directly their health promoting properties as well as the sensory quality of the product; however they are prone to degradation by, inter alia, elevated temperature and tissue enzymes. The traditional thermal methods of food preservation cause significant losses of these pigments. Thus, novel non-thermal techniques such as high pressure processing, high pressure carbon dioxide and high pressure homogenization are under consideration. In this review, the authors attempted to summarize the current knowledge of the impact of high pressure techniques on the stability of anthocyanins during processing and storage of fruit and vegetable products. Furthermore, the effect of the activity of enzymes involved in the degradation of these compounds has been described. The conclusions including comparisons of pressure-based methods with high temperature preservation techniques were presented.