Purification and partial biochemical characterization of polyphenol oxidase from mango (Mangifera indica cv. Manila)

Polyphenol oxidase inactivation from apple juice by Al-based metal-organic frameworks: New anti-browning strategy in fruits and vegetables

Polyphenol oxidase (PPO) is critical due to enzymatic browning in fruits and vegetables, developing economic impact in fruits industry. Metal-Organic Frameworks (MOF) have shown interesting characteristics such as water stability, low toxicity, and good adsorption yield, making them good candidates for PPO inactivation. Al-based-MOFs, MIL-53(Al), DUT-5, and MIL-110 were tested as PPO inactivators in apple juice by enzyme-MOF interactions at r.t. through two possible mechanisms, i) substrate scavengers (substrates:catechol and 4-methylcatechol) or ii) enzyme activity modifiers. The scavenging behavior of Al-based-MOFs was moderate, in the same magnitude, being catechol adsorption better than 4-methylcatechol. PPO activity was reduced by at least 70% by MIL-53(Al)/DUT-5 in 10/30 min respectively, and MIL-110 inactivated PPO in 50 min with some structural modifications. Enzyme-MOF interactions are major responsible for PPO inactivation. This could be a new applicability of MOFs, as an alternate PPO inactivation process, easily included in juice processing, retaining sensorial/nutritional properties, developed at r.t thus energy-cost-effective.

Extraction, Purification, and Characterization of Olive (Olea europaea L., cv. Chemlal) Polyphenol Oxidase

Among fruits susceptible to enzymatic browning, olive polyphenol oxidase (OePPO) stood out as being unisolated from a natural source until this study, wherein we successfully purified and characterized the enzyme. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of heated and nonheated OePPO revealed distinct molecular weights of 35 and 54 kDa, respectively, indicative of its oligomeric nature comprising active and C-terminal subunits. OePPO displayed latency, fully activating with 5 mM SDS under optimal conditions of pH 7.5 and 15 °C. The enzyme demonstrated monophenolase activity and showcased the highest efficiency toward hydroxytyrosol. Despite its low optimal temperature, OePPO exhibited high thermal resistance, maintaining stability up to 90 °C. However, beyond this threshold, the oligomeric enzyme disassociated, yielding a denatured main subunit and C-terminal fragments. Six OePPO genes were found in the fruits. Tryptic digestion identified the enzyme as mature OePPO1 (INSDC OY733096), while mass spectrometry detected the active form mass alongside several C-terminal fragments, revealing potential cleavage sites (Gly407, Tyr408).

Mangosteen vinegar from Garcinia mangostana: quality improvement and antioxidant properties

Mangosteen (Garcinia mangostana Linn.) fruit is rich in phenolic compounds which function as antioxidants and play a role in anti-inflammation, anti-hyperlipidemia, and anti-diabetic nephropathy. To investigate mangosteen vinegar (MV) by steaming under high pressure, explore the effects of fermentation, antioxidant activity, and sensory evaluation acceptable using the 9 -point Hedonic scale. Steamed mangosteen was processed to produce 3 types of mangosteen vinegar: mangosteen rind vinegar (MRV), mangosteen flesh vinegar (MFV), and mangosteen rind plus flesh vinegar (MRFV). All 3 kinds of mangosteen vinegar were obtaining >4% acetic acid and significantly higher total phenolic content (TPC), total flavonoid content (TFC), and free radical scavenging ABTS+ and DPPH- antioxidant activity than apple cider vinegar (ACV) (p < 0. 05). The phenolic compounds analysis of mangosteen vinegar using HPLC were found Gallic acid, Catechin, Epicatechin, Vanillic acid, Trans-ferulic acid, Rutin, Gamma-mongostin, and Alpha-mangostin which showed almost higher than that found in ACV. Therefore, MVs produced from streamed mangosteen have higher antioxidants and were more acceptable using the 9-point Hedonic scale, a significantly higher statistical analysis of sensory evaluation than ACV, especially MFV. Taken together, steamed MVs should be further studied to prove the health benefits as a dietary supplement.

Flash vacuum expansion: an alternative with potential for Ataulfo and Manila mango processing

Mangoes of the Manila and Ataulfo varieties are characterized by having a pleasant flavor and an attractive color of both the peel and pulp. However, due to their post-harvest physiology, they are highly perishable and very susceptible to physical damage, which greatly limits marketing these fruits. Therefore, it is necessary to evaluate technologies that preserve their organoleptic and nutritional properties. There is also an increasing demand of products that are as natural as possible where only physical processes are used in their preparation to reduce the use of chemical compounds. A technology that satisfies these demands is the flash vacuum-expansion (FVE) process. In Ataulfo mango, the FVE process increased soluble solids by approximately 9% and total phenolic content from 100.9 to 122.8 mg GAE/100 g of puree, which led to an increase in antioxidant capacity of the puree, as well as slightly improving color stability. However, further optimization of this method of processing mango is required.

Purification and Characterization of a Dark Red Skin Related Dimeric Polyphenol Oxidase from Huaniu Apples

The distinct dark-red skin of Huaniu apples renders them attractive to customers. However, the mechanism that leads to the development of the color of the fruit is unclear. In this study, we found that compared with red Fuji (a bright-red apple cultivar), Huaniu apples had higher contents of (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-gallocatechin gallate (GCG), and procyanidins (PCs) B2 and C1 in the peel, which implies that the polymerization of the flavanols and PCs may be correlated with the dark-red skin of the fruit. Using EC as a substrate, we purified an enzyme from Huaniu peel. We performed protein sequencing and discovered that the enzyme was a polyphenol oxidase (PPO). The molecular weight of the enzyme was approximately 140 kDa, which we estimated by native-PAGE and SDS-PAGE, while it was 61 kDa by urea-SDS-PAGE, from which we discovered that the PPO was a dimer. We observed the lowest K_m value for catechol (0.60 mM), and the best substrate was 4-methylcatechol, with a V_max of 526.32 U mg⁻¹ protein. EC is a suitable natural substrate, with a K_m value of 1.17 mM, and 55.27% of the V_max/K_m of 4-methylcatechol. When we used EC as a substrate, the optimum temperature and pH of the PPO were 25 °C and 5.0, respectively. In summary, we purified a dimeric PPO from Huaniu apples that showed high activity to EC, which might catalyze the polymerization of flavanols and PCs and lead to the dark-red color development of the fruit.

Comparison of the Effect of Hydrostatic and Dynamic High Pressure Processing on the Enzymatic Activity and Physicochemical Quality Attributes of 'Ataulfo' Mango Nectar

The effects of hydrostatic (HHP) and dynamic (HPH) high-pressure treatments on the activity of pectin methylesterase (PME) and polyphenol oxidase (PPO) as well as the physicochemical quality attributes of ‘Ataulfo’ mango nectar were assessed. HHP reduced PME relative activity by 28% at 100 MPa for 5 min but increased PPO activity almost five-fold. Contrarily, HPH did not affect PME activity, but PPO was effectively reduced to 10% of residual activity at 300 MPa and at three passes. Color parameters (CIEL*a*b*), °hue, and chroma were differently affected by each type of high-pressure processing technology. The viscosity and fluid behavior were not affected by HHP, however, HPH changed the apparent viscosity at low dynamic pressure levels (100 MPa with one and three passes). The viscosity decreased at high shear rates in nectar samples, showing a shear-thinning effect. The results highlight how different effects can be achieved with each high-pressure technology; thus, selecting the most appropriate system for processing and preserving liquid foods like fruit beverages is recommended.

Osmotic Dehydration, Drying Kinetics, and Quality Attributes of Osmotic Hot Air-Dried Mango as Affected by Initial Frozen Storage

Using frozen mango for osmotic hot air drying is still uncommon due to a lack of knowledge on the effect of the freezing process on the final product's quality attributes. This study aimed to investigate the effect of the freezing method (slow and quick freezing) and frozen storage time at -18 °C (0, 1, and 2 months) on mass transfer kinetics during osmotic dehydration, drying kinetics during hot air drying, and final quality attributes of the dried mango. The results indicated that Peleg's model could describe the water loss and solid gain during the osmotic dehydration in a 38° Brix sugar solution. Freezing before osmotic dehydration reduced the water loss rate while increasing the solid uptake content. Frozen mangoes showed slightly higher drying rates at 50 and 60 °C than the fresh ones. Freezing and frozen storage also retarded the browning reaction and polyphenol oxidase activities. The osmotic-dried mango obtained from frozen mangoes showed a chewy and gummy texture, which could be considered a distinctive texture characteristic for dried mango.

Biochemical studies of enzyme-induced browning of African bush mango (Irvingia gabonensis) fruit pulp

The purpose of this study was to examine the biochemical properties of African bush mango (Irvingia gabonensis) pulp PPO. PPO was purified from I. gabonensis fruit pulp in three steps and characterized. A purification fold of 343 with specific activity of 216 U/mg and 13% recovery were obtained as well as molecular weight of 32.67 kDa was observed. The optimum pH and temperature were found to be pH 7.0 and 50 °C respectively while the enzyme showed instability at low pH 2-4 with total inactivation at pH 2 but maximal at pH 5-9 with remaining residual activity of 60-90%, whereas, total enzyme activity inactivation was observed at 90 °C. However, Cu²⁺, Fe²⁺ and Mg²⁺ enhanced the PPO activity but inhibited by Ca²⁺, Ba²⁺, K⁺ and Na⁺. Notably, purified PPO was inactivated completely by urea at concentration above 10 mM while K_m and V_max values were estimated to be 7.34 mM and 0.36 U/min for catechol, 10.76 mM and 0.30 U/min for _L-DOPA, and 14.90 mM and 0.26 U/min for tyrosine, respectively. The activity of PPO in I. gabonensis fruit and its juicy product could be controlled at high temperature in acidified medium.

Effects of Extraction Conditions on Banana Peel Polyphenol Oxidase Activity and Insights into Inactivation Kinetics Using Thermal and Cold Plasma Treatment

The objective of this work was to characterize banana peel polyphenol oxidase (PPO) and to study the inactivation kinetics during thermal and cold atmospheric pressure plasma treatment. Since varietal differences in enzyme characteristics are a well-known phenomenon, 'Prata' banana peel PPO was characterized, and PPO activity and thermal stability of the peel PPO of the two dessert banana cultivars 'Cavendish' and 'Prata' were compared to identify the cultivar better suited for industrial food applications. A crude extract obtained from the peels of the Brazilian banana variety 'Prata' revealed highest PPO activities (46.0-55.2 nkat/mL) at 30-40 °C in a range of pH 6.0-6.5 after addition of 0.5 g/g_sample polyvinylpyrrolidone and 0.5% (v/v) Triton X-100 during extraction. 'Cavendish' PPO activity was four times higher. Banana peel PPO exhibited the highest affinity towards dopamine (K_M = 0.94 mM). Thermal inactivation of 'Prata' and 'Cavendish' PPO was achieved at 90 °C after 5 and 15 min, respectively, whereas cold plasma treatment did not decrease PPO activity below 46% of the initial enzyme activity. The inactivation behavior of PPO could successfully be described by a two-fraction model indicating at least two types of isoenzymes with different thermal stability. The overall high thermal stability was mainly attributed to membrane-bound PPO. The results may help to prevent enzymatic browning of banana peels and thereby facilitate their valorization as food ingredients.

Extraction of ingredients from tea leaves using oxidative enzymatic reaction and optimization of extraction conditions

Peroxidase (POD) and polyphenol oxidase (PPO) are used as biocatalyst in many processes such as oxidization reactions, wastewater treatment, phenol synthesis and so on. The purpose of current study is enzymes extraction from biomass (tea leaves) as well as evaluation of their activation. Different parameters including temperature, buffer concentration, buffer type, buffer/tea leaves ratio, addition of high molecular weight polymers and emulsifiers, and pH were optimized in order to obtain the highest enzymes activity. Response Surface Methodology (RSM) procedure is employed for statistical analysis of enzymes extraction. It is understood from the result that PPO and POD possess the highest activity at temperatures of 25 °C and 50 °C, pH 7 and 5, buffer molarity of 0.1, and 0.05, buffer/tea leaves ratio = 5 for both, contact time = 20 min and 10 min, and presence of 6% and 3% PVP, 5% and 0% Tween 80 for PPO and POD, respectively. Amounts of highest activity for PPO and POD biocatalysts were calculated 0.42 U/mL and 0.025493 U/mL, respectively. Moreover, the entire inactivation of PPO took place after 30 min at 40 °C and 60 °C and 20 min at 80 °C. However, POD lost 35% of its activity after 30 min at 40 °C and 60 °C. The amount of 6% POD activity was kept after 45 min at 80 °C. Generally, it was indicated that POD was more resistant to thermal treatment than PPO.

Comparison of the biochemical properties and thermal inactivation of polyphenol oxidase from three lily bulb cultivars

The biochemical properties and thermal inactivation of polyphenol oxidase (PPO) from three main planted lily cultivars in China, namely, Lilium lancifolium Thunb, Lilium brownie var. viridulum, and Lilium davidii var. unicolor cotton were evaluated. Data indicate that the PPO from three cultivars showed two optimum pH levels of 4.0 and 6.5-7.0 and temperature of 15°C and exhibited the highest affinity toward 4-methylcatechol. However, this enzyme did not exhibit monophenolase activity. Thiourea and L-cysteine were more effective than other inhibitors. The enzymatic activity of L. lancifolium Thunb PPO crude extract was higher than that of L. brownie var. viridulum and L. davidii var. unicolor cotton. For thermal inactivation, L. davidii var. unicolor cotton PPO showed the best thermal resistance at 65-75°C, and L. lancifolium Thunb showed stability at 45°C. The deactivation of the three types of PPO followed the first-order reaction kinetics, and the activation energy (Ea) was 144.28, 138.00, and 107.12 kJ/mol for L. lancifolium Thunb PPO, L. brownie var. viridulum PPO, and L. davidii var. unicolor cotton PPO, respectively. PRACTICAL APPLICATIONS: Lilium is an ornamental and edible plant typically used for food and traditional Chinese medicine. Its flowers are used for decoration, and its underground bulbs are rich in various bioactive substances. Fresh lily bulbs easily turn brown and lose economic value during storage and processing. Polyphenol oxidase (PPO) is a crucial molecule involved in the enzymatic browning of fruit and vegetables. In this study, PPO was extracted from three main planted lily cultivars in China. Namely, Lilium lancifolium Thunb, Lilium brownie var. viridulum, Lilium davidii var. unicolor cotton and was partially characterized. The results are of considerable importance to further understand the PPO of lily bulbs and provide guidance for the inactivation of enzymes and the processing of lily bulb juice.

Purification, kinetic parameters, and isoforms of polyphenol oxidase from "Xushu 22" sweet potato skin

We purified and compared the polyphenol oxidase (PPO) isoenzymes present in "Xushu 22," a sweet potato. A membrane-bound form (mPPO) and two soluble forms (sPPO1 and sPPO2) were identified and purified using ammonium sulphate precipitation, ion exchange chromatography, gel filtration chromatography, and mass spectrometer. The three PPO isoforms were characterized enzymatically. The specific activity of mPPO was significantly higher than that of the two sPPO isoforms, being 24.55- and 13.89-fold higher than sPPO1 and sPPO2. The preferred substrates for mPPO and the two sPPOs were catechol and chlorogenic acid, respectively. They can be efficiently and safely applied to phenolic wastewater treatment after being immobilized. Both mPPO and the two sPPOs were rapidly inactivated under acid or base conditions and were unstable at 65°C. The most effective inhibitors of mPPO, sPPO1, and sPPO2 were glutathione, ascorbic acid, and L-cysteine, respectively. PRACTICAL APPLICATIONS: According to incomplete statistics, about 5% of sweet potatoes in china are wasted due to enzymatic browning every year. PPO was regarded as a key molecule contributing to enzymatic browning in fruits and vegetables during ripening, processing, and storage and responsible for economic and industrial loss. It's great importance to characterize the PPO from "Xushu 22" sweet potato and provide data on its inactivation. The three PPO isoforms were purified and identified by chromatography and mass spectrometer. This study will provide useful informations to have a better command of PPO from "Xushu 22" sweet potato and give ideals to solve the browning of sweet potato.

Purification and characterization of a thaumatin-like protein-1 with polyphenol oxidase activity found in Prunus mume

Thaumatin-like protein-1 (TLP-1), a protein displaying high polyphenol oxidase (PPO) action and a member of the pathogenesis-related (PR) protein family, has a considerable influence on the enzymatic browning of Prunus mume (Chinese plum). In this assay, TLP-1 was identified and extracted from Prunus mume to investigate the protein's properties and better understand its contribution to the fruit's browning during storage or processing. The extracted TLP-1 was purified to apparent homogeneity using a procedure involving citrate phosphate buffer solution (CPBS) extraction, (NH₄)₂SO₄ precipitation, dialysis in a cellulose bag, and ion exchange chromatography using a DEAE Sepharose Fast Flow column, while a Sephadex G-75 column was employed to facilitate gel filtration chromatography. Moreover, the enzyme was characterized in terms of its optimal pH and stability, isoelectric point (pI), molecular weight, optimal temperature and stability, enzyme kinetic parameters and substrate specificity, as well as inhibitor stability. This study indicated that the pI and molecular weight of TLP-1 was approximately 4.4 and 28 kDa, respectively, while 30 °C and 7.5 represented the respective optimal temperature and pH level for PPO catalysis. TLP-1 showed high affinity to catechol and pyrogallol, with K_m values of 24.40 mM and 26.23 mM, respectively. Sodium bisulfite significantly inhibited TLP-1 activity. These findings on the properties of TLP-1 can contribute significantly to the search for ways to minimize the losses caused by fruit browning during the storage and processing of Prunus mume.

Thaumatin-like protein-1 (TLP-1), a protein displaying high polyphenol oxidase (PPO) action and a member of the pathogenesis-related (PR) protein family, has a considerable influence on the enzymatic browning of Prunus mume (Chinese plum).

Inhibitory effects of organic acids on polyphenol oxidase: From model systems to food systems

Organic acids are widely utilized in the food industry for inhibiting the activity of polyphenol oxidase (PPO) and enzymatic browning. This review discusses the mechanisms of inhibition of PPO and enzymatic browning by various organic acids based on studies in model systems, critically evaluates the relevance of such studies to real food systems and assesses the implication of the synergistic inhibitory effects of organic acids with other physicochemical processing techniques on product quality and safety. Organic acids inhibit the activity of PPO and enzymatic browning via different mechanisms and therefore the suitability of a particular organic acid depends on the structure and the catalytic properties of PPO and the physicochemical properties of the food matrix. Studies in model systems provide an invaluable insight into the inhibitory mechanisms of various organics acids. However, the difference in the effectiveness of PPO inhibitors between model systems and food systems and the lack of correlation between the degree of PPO inhibition based on in vitro assays and enzymatic browning imply that the effectiveness of organic acids can be accurately evaluated only via direct assessment of browning inhibition in a particular food system. Combination of organic acids with physical processing techniques is one of the most viable approaches for PPO inhibition since the observed synergistic effect helps to reduce the undesirable organoleptic quality changes from the use of excessive concentration of organic acids or intense physical processing.

Chemical Composition of Mango (Mangifera indica L.) Fruit: Nutritional and Phytochemical Compounds

Mango fruit has a high nutritional value and health benefits due to important components. The present manuscript is a comprehensive update on the composition of mango fruit, including nutritional and phytochemical compounds, and the changes of these during development and postharvest. Mango components can be grouped into macronutrients (carbohydrates, proteins, amino acids, lipids, fatty, and organic acids), micronutrients (vitamins and minerals), and phytochemicals (phenolic, polyphenol, pigments, and volatile constituents). Mango fruit also contains structural carbohydrates such as pectins and cellulose. The major amino acids include lysine, leucine, cysteine, valine, arginine, phenylalanine, and methionine. The lipid composition increases during ripening, particularly the omega-3 and omega-6 fatty acids. The most important pigments of mango fruit include chlorophylls (a and b) and carotenoids. The most important organic acids include malic and citric acids, and they confer the fruit acidity. The volatile constituents are a heterogeneous group with different chemical functions that contribute to the aromatic profile of the fruit. During development and maturity stages occur important biochemical, physiological, and structural changes affecting mainly the nutritional and phytochemical composition, producing softening, and modifying aroma, flavor, and antioxidant capacity. In addition, postharvest handling practices influence total content of carotenoids, phenolic compounds, vitamin C, antioxidant capacity, and organoleptic properties.

Purification and biochemical characterization of polyphenol oxidase from soursop (Annona muricata L.) and its inactivation by microwave and ultrasound treatments

The soursop (Annona muricata L.) is a climacteric fruit that may undergo enzymatic browning during ripening, mainly by the activity of polyphenol oxidase (PPO). Soursop PPO was purified 160-fold by hydrophobic interaction and ion-exchange chromatography. The native structure has a molecular weight of 112 kDa corresponding to a dimeric structure. The protein has an optimum pH and temperature of 6.5 and 25°C, respectively; and activation energy of 40.97 kJ·mol^-1 . The lowest K_m value was observed for caffeic acid (0.47 mM); the best substrate was 4-methyl-catechol (1,067 U·mM^-1  min^-1 ). Inactivation assays showed that PPO was completely inactivated by tropolone, Na₂ S₂ O₅ and ascorbic acid, and thermally at 55°C for <5 min, microwave exposure reduced activity to 57% at 70 W in 30 s and ultrasound treatment diminished activity to 43% at 120 W in 220 s. This study allows a better understanding of soursop PPO behavior and provides inactivation information. PRACTICAL APPLICATIONS: The conservation of fresh fruits is complicated due to the enzymatic reactions that are present in fruits, such as enzymatic browning. The enzymes responsible for these reactions can be inactivated by, different chemical compounds as well as by the use of emerging technologies, such as microwaves and sonication, which seek to satisfy the consumer needs to obtain fresh products with good nutritional characteristics and adequate safety.

Purification and Characterization of Latent Polyphenol Oxidase from Apricot (Prunus armeniaca L.)

Polyphenol oxidase from apricot (Prunus armeniaca) (PaPPO) was purified in its latent form (L-PaPPO), and the molecular weight was determined to be 63 kDa by SDS-PAGE. L-PaPPO was activated in the presence of substrate at low pH. The activity was enhanced by CuSO₄ and low concentrations (≤ 2 mM) of SDS. PaPPO has its pH and temperature optimum at pH 4.5 and 45 °C for catechol as substrate. It showed diphenolase activity and highest affinity toward 4-methylcatechol (K_M = 2.0 mM) and chlorogenic acid (K_M = 2.7 mM). L-PaPPO was found to be spontaneously activated during storage at 4 °C, creating a new band at 38 kDa representing the activated form (A-PaPPO). The mass of A-PaPPO was determined by mass spectrometry as 37 455.6 Da (Asp102 → Leu429). Both L-PaPPO and A-PaPPO were identified as polyphenol oxidase corresponding to the known PaPPO sequence (UniProt O81103 ) by means of peptide mass fingerprinting.