Higher Polyphenol Oxidase Activity Research Articles

Flesh browning development of ‘Empire’ apple during a shelf life period after 1-methylcyclopropene (1-MCP) treatment and controlled atmosphere storage

Little information is known about metabolism of flesh browning disorders in apples after removal of fruit from cold storage. ‘Empire’ apples develop a firm flesh browning, a physiological disorder that is assumed to be a chilling injury because it occurs usually at 0.5 °C; however, incidence is increased in fruit at warmer storage temperatures (2–3 °C) if fruit have been treated with 1-methylcyclopropene (1-MCP). In this study, fruit were untreated or treated with 1-MCP and stored in controlled atmospheres at 0.5 or 3 °C for 40 weeks, followed by a 10 d shelf life period at 20 °C. The greatest increase of internal ethylene concentration (IEC) and softening occurred in the fruit that had been stored at 3 °C without 1-MCP, and the lowest in fruit from 0.5 °C plus 1-MCP. Flesh browning was present in 1-MCP treated fruit and in fruit stored at 0.5 °C at the time of removal, and low in fruit stored at 3 °C. Incidence and severity of the disorder in 1-MCP treated fruit stored at 3 °C increased greatly during the shelf life period. Electrolyte leakage was higher in 1-MCP treated fruit stored at 0.5 °C than in the other treatments. Polyphenol oxidase (PPO) activity was higher in 1-MCP treated fruit regardless of storage temperature but peroxidase (POX) activity was higher in fruit that had been stored at 0.5 °C regardless of 1-MCP treatment. The highest POX activity was measured in the fruit that had been stored at 0.5 °C without 1-MCP treatment. Overall, browning development during the shelf life is associated with higher PPO activity in 1-MCP treated fruit and higher POX activity at the lower storage temperature.

Effect of exogenous ARA treatment for improving postharvest quality in cherry tomato (Solanum lycopersicum L.) fruits

The study aimed to characterize the effects of exogenous arachidonic acid (ARA) treatment on improving postharvest physiological quality in cherry tomato fruits stored at 20 ℃ (room temperature) for 14 days. Freshly harvested cherry tomato fruits were treated with ARA at the concentrations of 2.5 and 5.0 mg L−1. As compared with the control, ARA reduced the decay and weight loss of cherry tomato fruits, decreased malondialdehyde (MDA) accumulation, and maintained higher activities of polyphenol oxidase (PPO), peroxidase (POD), and catalase (CAT). In addition, the application of ARA in cherry tomato fruits delayed the increase of membrane permeability, kept the integrity of the cell membrane and reduced total soluble solids (TSS) and titratable acidity (TA) loss during the later stage of storage. Therefore, the concentration of 2.5 mg L−1 ARA was found to be an optimum ARA treatment for maintaining the storage quality of cherry tomato fruits. These findings may suggest that ARA treatment effectively improve the metabolism and storage quality of cherry tomato fruits stored at 20℃. The exogenous ARA is a kind of green, safe and non-polluting preservative in the postharvest fruits and vegetables, which has good application value and economic benefit.

Effect of blanching and drying temperatures on the browning‐related enzymes and physicochemical properties of lily bulb flours

The effects of blanching methods and different drying temperatures on the polyphenol oxidase (PPO), peroxidase (POD), and physicochemical properties of lily flours were investigated. PPO, POD, and color results showed that blanching with steam for 1 min effectively inhibited the enzymatic browning of the lily bulbs. L* of the samples blanched with steam combined with 50°C of air drying was higher than that of the rest air-dried samples. Blanching, especially employing steam, could significantly lower the loss of total phenolic contents and antioxidant activities of the samples dried at the same temperature. The starch granules of the air-dried samples with blanching were completely gelatinized, whereas the ones directly dried at 50°C or 70°C were partially gelatinized. Blanching and drying caused a significant increase in particle size. The protein and total starch contents of the samples decreased as drying temperature increased with or without blanching. Practical applications Fresh lily bulbs contain high moisture, high PPO and POD activities, and hence extremely susceptible to turn brown and perishable. The actual applications of this research are to evaluate the physicochemical properties of lily bulbs that underwent different blanching and drying methods. Blanching is an effective and commonly used pretreatment to control enzymatic browning, while over-blanching could cause undesired loss of nutrients, such as protein, phenolics, and starch. In addition, blanching and drying unit can affect the gelatinization of starch-based materials and consequently influence its functional behavior. Thus, this study aimed to find an efficient method and suitable parameters for inactivating endogenous browning enzymes, and also evaluate the effects of blanching and drying temperature on the physicochemical properties of lily bulbs. These findings might be used as a basis for modifying the properties of lily flours as food ingredients in other products, such as noodles, baked products, and mixed porridge.

Preparation of bio-electrodes via Langmuir-Blodgett technique for pharmaceutical and waste industries and their biosensor application

Langmuir films of cationic octadecylamine (ODA+) has been prepared by Langmuir-Blodgett (LB) film technique and is used as an immobilization matrix for polyphenol oxidase (PPO). The immobilization areas of PPO were demonstrated by an electrostatic surface potential map. PPO-ODA complexes were transferred onto ITO electrode which was then characterized for its catalytic and optical properties. Very high and maintained PPO activity of PPO-ODA/ITO bio-electrode was shown by UV–vis absorption studies. The highly sensitive and stability biosensor behavior of the bio-electrode was shown via cyclic voltammetry studies. The stability, sensitivity, LOD and, LOQ values of the prepared sensor were calculated as 94.83% (after two weeks), 1.839 μAmM−1 cm−2, 0.644 μM and, 0.214 μM, respectively for pyrocatechol in a wide linear range (10–100 mM). Successful prepare of the bio-electrode was confirmed from SEM and FT-IR techniques. This study revealed that the immobilization with LB film techniques contributes to the stability and recycling of PPO and its use in biological systems is superior to other film techniques mentioned in the literature. In this study, disadvantages that are observed in enzyme-based sensors were minimized. The first application of the bio-electrodes can be a promising tool towards enzymatic studies and opens a new path for industrial applications such as removing and transforming toxic compounds in industrial processes, decolorization, and drug industry such as biotechnological production of l-DOPA.

Efficacy of Yarrowia lipolytica in the biocontrol of green mold and blue mold in Citrus reticulata and the mechanisms involved

Green mold and blue mold caused by Penicillium digitatum and P. italicum respectively, are two main fungal diseases in Citrus reticulata (mandarin oranges) worldwide. They are difficult to prevent for the lack of effective antagonists. This study investigated the efficacy of Yarrowia lipolytica against these diseases in mandarins and the relative defense mechanisms. The results indicated that Y. lipolytica has a great potential to inhibit the infections by P. digitatum and P. italicum in mandarins, while both the decay incidence and lesion diameter decreased in Y. lipolytica treated mandarins, in a dose-dependent manner. Furthermore, Y. lipolytica treatment had no side effects on quality paraments of mandarins. In vitro tests demonstrated that, spore germination and germ tube length of P. digitatum and P. italicum were both inhibited by Y. lipolytica. In addition, Y. lipolytica had a better ability to adapt to the environment, occupy space and utilize nutrients than pathogens, which provided a favorable condition for Y. lipolytica to colonize wounds and surfaces of mandarins. This research also showed that, Y. lipolytica induced higher activities of polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT), phenylalanine ammonia lyase (PAL), and increased the contents of flavonoid compounds and total phenols, which activated the defense mechanisms of mandarins. These results suggested that Y. lipolytica is a promising antagonistic yeast to control green mold and blue mold in mandarins.

Salicylic acid and jasmonic acid can suppress green and blue moulds of citrus fruit and induce the activity of polyphenol oxidase and peroxidase

Abstract The ability of salicylic acid and jasmonic acid to suppress post-harvest infection with green mould Penicillium digitatum and blue mould P. italicum on three citrus species Citrus reticulata ‘Kinnow’, C. limon ‘Meyer Lemon’, and C. limetta ‘Mosambi’ was evaluated in a dose-response study. Salicylic acid (SA) and jasmonic acid (JA) were applied to the fruits as a post-harvest dip treatment followed by wound inoculation with the pathogens. Both resistance inducers caused a significantly lower disease severity compared with the infected but non-treated control, whereas disease incidence was not significantly lower than in the control. The efficacy of both SA and JA in reducing disease severity was concentration-dependent; the use of higher concentrations resulted in a greater degree of suppression. All the Citrus species tested in this study showed different responses in terms of disease development. C. limon ‘Meyer Lemon’ showed the highest disease development, and C. limetta ‘Mosambi’ the lowest. To get an insight into the mechanisms underlying the increase in resistance, the activity of defence-related enzymes – peroxidase (POD) and polyphenol oxidase (PPO) – was recorded in SA- and JA-treated fruit peelings. The activity of both enzymes was directly proportional to the concentration of the SA and JA applications. The highest activity of PPO and POD was observed in C. reticulata ‘Kinnow’ and the lowest in C. limon ‘Meyer Lemon’ fruits. This study is the first to document an increase in the activity of PPO and POD in SA- and JA-treated Citrus species in the presence of blue mould and green mould pathogens.

Ultrasonic Processing Induced Activity and Structural Changes of Polyphenol Oxidase in Orange (Citrus sinensis Osbeck).

Apart from non-enzymatic browning, polyphenol oxidase (PPO) also plays a role in the browning reaction of orange (Citrus sinensis Osbeck) juice, and needs to be inactivated during the processing. In this study, the protein with high PPO activity was purified from orange (Citrus sinensis Osbeck) and inactivated by ultrasonic processing. Fluorescence spectroscopy, circular dichroism (CD) and Dynamic light scattering (DLS) were used to investigate the ultrasonic effect on PPO activity and structural changes on purified PPO. DLS analysis illustrated that ultrasonic processing leads to initial dissociation and final aggregation of the protein. Fluorescence spectroscopy analysis showed the decrease in fluorescence intensity leading to the exposure of Trp residues to the polar environment, thereby causing the disruption of the tertiary structure after ultrasonic processing. Loss of α-helix conformation leading to the reorganization of secondary structure was triggered after the ultrasonic processing, according to CD analysis. Ultrasonic processing could induce aggregation and modification in the tertiary and secondary structure of a protein containing high PPO activity in orange (Citrus sinensis Osbeck), thereby causing inactivation of the enzyme.

The biocontrol of postharvest decay of table grape by the application of kombucha during cold storage

Grapes are susceptible to fungal infection and decay after harvest. The objective of this study was to investigate the effects of kombucha on postharvest fresh-keeping in table grape (Vitis vinifera cv. Fujiminori). Here, we studied the effects of kombucha on the fruit quality and antioxidant system of grape at 4 °C storage. The fruits of grape were dipped into water or kombucha for 15 min and then stored at 4 °C. The physical parameters of fruits, such as the good fruit rate, fruit hardness, contents of soluble solid, ascorbic acid (Vit C) and malodialdehyde (MDA), and activities of the antioxidant enzymes were measured during storage. The application of kombucha reduced deterioration of table fruit during cold storage. The kombucha treatment also delayed the decrease in fruit hardness, soluble solid and Vit C contents, and inhibited the MDA accumulation in grape during storage. Furthermore, fruit treated with kombucha showed significantly higher activities of polyphenol oxidase, peroxidase, catalase and superoxide dismutase with a significantly lower MDA accumulation at the late stage of storage compared the control. Our findings suggested that kombucha application was useful in inhibiting postharvest decay of table grape fruit and appeared to have potential for commercial application to store table grape at cold storage.

Morphogenetic, Physiological, and Biochemical Features of Lavandula angustifolia at Long-Term Micropropagation In Vitro

Data on morphogenesis and some physiological and biochemical parameters of explants of five cultivars of Lavandula angustifolia Mill. under long-term micropropagation in vitro during nine passages are represented. Introduction of meristems of the Stepnaya, Sineva, Vdala, Rannaya, and Record cultivars into the culture resulted in the formation of multiple shoots. Maximal number of shoots was observed in the Sineva cultivar (5.7), while minimal number was identified in the Rannaya cultivar (3.9). The experiments with micropropagation of lavender in nine subcultivations showed that the number of shoots increased in all cultivars up to the third subculture and decreased thereafter. The highest multiplication index (12.2) in this passage was observed for the Sineva cultivar. Further subculture were characterized by decrease of this parameter to 7.4–8.6. The lowest multiplication index in the fifth to ninth passages was observed for the Record cultivar (3.8–4.5). The analysis of the water regime of the microshoots obtained via in vitro multiplication showed that the total water content was 83–89%, while fractions of bound and colloid-consumed water made up to 40–57%. Record, Rannaya, and Vdala cultivars were shown to possess maximal water-retaining capacity. The obtained data indicate the active function of chlorenchyma. It was found that the Vdala and Sineva cultivars were characterized by maximal photosynthetic activity of their leaves and shoots and showed the highest viability index. The cultivars studied under the conditions of in vitro cultivation were characterized by a high level of proline, ascorbic acid, and phenolic compounds, especially flavanols. The highest level of proline was observed in the Vdala cultivar (372.87 µg/g), while the highest concentrations of ascorbic acid (31.28 mg/100 g) and phenolic compounds (1103 mg/100 g) were found in the Sineva and Rannaya cultivars, respectively. Shoots cultured in vitro were characterized by a high activity of catalase and low activity of superoxide dismutase and polyphenol oxidase. The highest catalase activity was observed in the Vdala and Sineva cultivars. The Sineva cultivar also demonstrated a high activity of polyphenol oxidase. The results obtained demonstrate the good ability of lavender to micropropagation in vitro, the efficiency of which depended on both the cultivar and the number of subcultures.

Effect of the application of inducers on soursop fruit (Annona muricata L.): postharvest disease control, physiological behaviour and activation of defense systems

The application of chitosan (Chi) alone or in combination with methyl jasmonate (MJ) and salicylic acid (SA) in soursop infected with C. gloeosporioides and R. stolonifer in vivo as well as quality parameters (pH, total soluble solids, firmness and titratable acidity), respiration rate, ethylene production and defense related enzyme activities were investigated. Diseases caused by phytopathogenic fungi at postharvest stage are a serious problem throughout the world. The pathogens evaluated in this study were isolated from orchards in Nayarit, Mexico. The coating application of 1.0% Chi - 0.1 mM MJ - 6 mM SA on fruit inoculated with C. gloeosporioides and 0.5% Chi- 0.1 mM MJ on fruit inoculated with R. stolonifer were more effective to reduce the disease incidence and the extension of the lesion on soursop rather than the application of Chi, MJ or SA alone. In order to maintain quality parameters Chi and inducers were applied on fruits. During the storage time quality parameters of fruit were maintained. The respiration rate and ethylene production decreased with the application of the treatments combination. Higher activities of PPO (polyphenol oxidase), and POD (peroxidase) were evidenced with the combination of treatments compare to control. The application of chitosan, methyl jasmonate and salicylic acid is a suitable method for postharvest disease control of soursop during storage time as well as to maintain the fruit quality.

Exometabolomic study of extracellular metabolites in tobacco plant induced by ethyl acetate extracts of Streptomyces diastatochromogenes KX852460

Streptomyces diastatochromogenes KX852460, produced induce systemic resistance against Rhizoctonia solani AG-3. SA from the strain was given as treatment to the tobacco plants. Activity of the defense enzymes was analyzed by spectrophotometer, while extracellular metabolites were analyzed by Liquid Chromatography Tandem Mass spectrometer (LCMS-MS). Defense-related enzymes glutathione peroxidase (GR), glutathione peroxide (GPX), and peroxidase (POD) had maximum activity after treated with extract. Same as was observed in inoculated with R. solani, and extract induced the high activity of glutathione reductase (GST), catalase (CAT), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO). While PPO had moderate activity even though with untreated samples (control). Metabolic profile of the treated sample was compared with control (untreated). Exometabolomic study reveal that in the treated sample amino acid (L-cysteine, N,S-di(trifluoroacetyl)-, trimethylsilyl ester), mammalian steroid 5α-Androstane-3α,17β-diol, bis(pentafluoropropionate), flavonoids (Rutin), amines and amides were identified. Current study determined that ethyl acetate extract could induce the resistance by activating the enzymes and by regulating the metabolism.

Formulation, Characterizations and Antibacterial Activity of some Nanoemulsions Incorporating Monoterpenes

In the current study, we formulated and characterized bio-based oil in water nanoemulsions incorporating monoterpenes; (R)-carvone, cinnamaldehyde, citral, geraniol and pulegone and tested their antimicrobial activity against two plant pathogenic bacteria, Pectobacterium carotovorum sub carotovorum and Ralstonia solanacearum in vitro and in vivo studies. Nanoemulsions (NEs) were prepared by adding dropwise monoterpenes at concentration of 5% in an aqueous solution containing 10% a surfactant (tween 80) with constant stirring and then ultrasonication. NEs were confirmed by dynamic light scattering and transmission electron microscopy. Physical stability and viscosity were, also, investigated. NEs monoterpenes had a poly dispersity index ranged from 0.130 to 0.630 and droplet size in the range of 56.64-176.00 nm. Results revealed that NE -cinnamaldehyde had great antibacterial activity against P. carotovorum and R. solanacearum (MIC = 60 and 100 mg/L, respectively). NE cinnamaldehyde was induced effective defense responses in vivo in potato plant and tubers against two tested bacteria at a rate 1000 and 3000 mg/kg. Higher activities of polyphenoloxidase (PPO), peroxidase (POD) activities and total phenolic content of tubers and leaves were significantly recorded compared to control at all tested times. This was evident from reduced soft and brown rot diseases symptoms of potato spunta cv treated with elicitors subsequently with tested bacteria. These results showed that the PPO, POD and total soluble phenols play a role in instructing resistance to potato soft and brown mold infections. The observed relationship between formulation and activity can lead to the rational design of nanoemulsion based systems for monoterpenes for applications in antimicrobial and agrochemical industries. Amalgamation of such economical treatments might lessen management costs and minimize the environmental pollution.

Variable polyphenol oxidase (PPO) activity indicates grain quality in bread wheat (Triticum aestivum L.)

Wheat (Triticum spp.) is one of the important cereals in the world. Discoloration of wheat grains and accumulation of by product due to polyphenol oxidase (PPO) activities is an important problem faced by food industries. In this study, seeds of 115 Indian bread wheat cultivars representing different six agroclimatic zones were screened for their PPO activities using different PPO substrates, like caffeic acid, catechol, tyrosine and L-DOPA. Among these substrates, L-DOPA was found as best substrate to detect PPO activity. Highest PPO activity with L-DOPA was found in wheat cultivar HS 207, while lowest was detected in HP 1633. Among different agroclimatic zones, seeds of 40% of the cultivars representing NWPZ showed low PPO activity (< 10 unit min−1 g−1) with an average value of 14.22 unit min−1 g−1 and 38% cultivars of NEPZ had low PPO activity with the mean of 13.56 unit min−1 g−1. Therefore, wheat cultivars form NWPZ and NEPZ can be used for producing wheat byproducts.

Enzyme activity and microbial biomass availability in artificial soils on rock-cut slopes restored with outside soil spray seeding (OSSS): Influence of topography and season

Large-scale railway construction has resulted in large areas of bare-cut-slope, and outside soil spray seeding (OSSS), a frequently used technique, has been adopted for slope restoration for many years. However, compared with natural slope soils, the quality of artificial soils on rock-cut slopes is low. Enzyme activity and microbial biomass are the main indices used for estimating soil quality; thus, our objective was to explore the influence of slope position, slope aspect, and season on two important factors that positively influence the plant growth capability in artificial soil. Further, we suggest modifications of the proportions of OSSS ingredients, not only to manage cut slopes more economically but also to provide a new framework for managing desertification.We chose a bare-cut-slope that had been restored five years ago near the Suiyu Railway (Chongqing-Suining), in Sichuan Province, China, as our study plot. Soil samples were collected at a depth of 10 cm. We conclude that natural slopes exhibited higher urease, sucrase, and catalase activity and higher microbial biomass than cut slopes. The protease and polyphenoloxidase enzyme activities and the microbial biomass were higher on the cut slopes in the months of October and January, with the highest protease activity in October, and the highest polyphenoloxidase activity in January. The enzyme activity and microbial biomass were always lower on lower slopes, with the exception of polyphenoloxidase activity. The slope aspect influenced soil enzyme activity, resulting in higher activity on north-facing slopes than on south-facing slopes. These results provided scientific support for artificial revegetation methods in an ecological context.

Effect of Ultrasonic Treatment Combined with Peracetic Acid Treatment Reduces Decay and Maintains Quality in Loquat Fruit

The effects of ultrasonic treatment (UT, 400 watts for 6 min) combined with peracetic acid (PA, 0.4% (W/W)) treatment on fruit decay, browning, and quality and physiological changes in loquat fruit stored at 20°C were investigated. The results showed that treatment with UT or PA alone significantly reduced both decay and browning index in loquat fruit compared with the control. The combined treatment was more effective in decreasing decay and browning index and maintaining higher quality parameters than UT or PA treatment alone. Loquat fruits treated with the combined treatment maintained higher activities of polyphenol oxidase (PPO) and peroxidase (POD) than those treated with other treatments. In addition, UT combined with PA treatment significantly reduced the increase of firmness and increased fruit extractable juice, total soluble solid (TSS), and ascorbic acid content in loquat fruit. Moreover, the contents of total phenolics and total flavonoids were enhanced by the combination of UT and PA treatment. The combination of UT and PA treatment could be a useful method to reduce decay and browning in loquat fruit stored at room temperature, which has potential for application in the loquat industry.

Comparative study of the banana pulp browning process of 'Giant Dwarf' and FHIA-23 during fruit ripening based on image analysis and the polyphenol oxidase and peroxidase biochemical properties.

This work presents a novel method to associate the polyphenol oxidase (PPO) and the peroxidase (POD) activities with the ripening-mediated color changes in banana peel and pulp by computational image analysis. The method was used to follow up the de-greening of peel and browning of homogenized pulp from 'Giant Dwarf' (GD: Musa AAA, subgroup Cavendish) and FHIA-23 (tetraploid hybrid, AAAA) banana cultivars. In both cultivars, the color changes of peel during the ripening process clearly showed four stages, which were used to group the fruit into ripening stages. The PPO and POD were extracted from pulp of fruit at these ripening stages, precipitated, and partially purified by gel filtration chromatography. Moreover, the pulp browning was digitally monitored after homogenization for a span time of up to 120min. The browning level was higher for GD than FHIA-23 tissues. This fact correlated with an 11.7-fold higher PPO activity in the GD cultivar, as compared with that of FHIA-23. POD activity was 8.1 times higher for GD as compared that that of FHIA-23.

Changes In Antioxidant Enzyme Activity In Turfgrass Cultivars Under Various Saline Water Irrigation Levels To Suit Landscapes Under Arid Regions

ABSTRACTTurfgrass cover is an inevitable component in the urban landscapes of the United Arab Emirates. Tolerance to abiotic stress like salt, drought, and high temperature is a potential factor to be considered in the selection of turfgrass for the landscapes in the arid regions. Three Seashore paspalum genotypes, four Bermudagrass cultivars along with tall fescue as a control were screened for enzymatic changes under four different saline irrigation levels of 5,000, 10,000, 15,000, and 20,000 mg L−1 of salinity. Irrigation with potable water served as the control. Turfgrasses were maintained in a field experiment under factorial randomized block design for a period of two years under sustained saline conditions by working out the leaching fraction to maintain the precise level of salinity in each treatment throughout the experimental period. The activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), polyphenol oxidase (PPO), and catalase (CAT) were assayed in each of the saline water treated turfgrass types. The SOD activity was found to be high in Yukon (bermudagrass) and Sea Dwarf paspalum. In the paspalum group, Salam and Sea Dwarf showed the highest SOD activity under saline condition. In Bermuda types, Yukon and SR 9554 showed the highest SOD activity compared to other bermuda types. Compared to other cultivars, Sea Isle 2000 (Paspalum type), SR 9554, and Yukon (Bermuda types) exhibited more APX activity without any significant differences among themselves. There was an elevated activity of POD initially, followed by gradual reduction upon increasing the salinity level. Salam cultivar maintained stable POD activity even at the elevated salinity levels. The paspalum types showed relatively high level of PPO activity compared to other types under salinity. Yukon cultivar showed a significantly higher activity of PPO when the salinity level was raised from 15,000 to 20,000 mg L−1. A significant increase with respect to CAT activity was exhibited in Sea Dwarf under elevated level of salinity. Saline water irrigation brought about a significant effect on the antioxidant enzyme systems to impart oxidative stress tolerance in turfgrass species.

Low accumulation of chlorogenic acids represses reddening during flesh browning in Japanese peach "Okayama PEH7".

In peaches, fruit flesh browns unattractively after peeling or cutting. A recently developed cultivar, Okayama PEH7, was distinct from other Japanese cultivars, including Okayama PEH8, with respect to its reduced browning potential. Homogenate prepared from Okayama PEH7 flesh had significantly less reddening during the browning reaction. Okayama PEH7 had less soluble phenolic compounds and higher polyphenol oxidase activity than Okayama PEH8. Reduced browning was observed even when phenols prepared from Okayama PEH7 were incubated with crude extract from Okayama PEH8, suggesting that phenols lower the browning potential of Okayama PEH7. In Okayama PEH7, contents of chlorogenic acid and its isomers were about one-tenth compared to Okayama PEH8. Exogenous addition of chlorogenic acid to Okayama PEH7 homogenate increased the browning potential and visibly enhanced reddening. These results indicate that the reduced browning of Okayama PEH7 flesh is due to a defect in chlorogenic acid accumulation.

Starch-enhanced degradation of HMW PAHs by Fusarium sp. in an aged polluted soil from a coal mining area

The present study used strain ZH-H2 (Fusarium sp.) isolated by our group as the PAH-degrading strain and 5-6-rings PAHs as degradation objects. The soil incubation experiment was carried out to investigate the starch-enhanced degradation effects of HMW PAHs by Fusarium sp. in an Aged Polluted Soil from a Coal Mining Area. The results showed that the removal rates of BaP, InP and BghiP increased with increasing inoculation rate of ZH-H2 in the unsterile aged polluted soil of coal mining area, with the exception of BbF degradation which increased in the H2 treatment and then decreased. Different addition dosage of starch apparently resulted in degradation of 4 PAHs in soil, with removal rates of 14.47% for BaP, 23.83% for DbA, 30.77% for BghiP and 31.00% for InP obtained with treatment D2, respectively higher than in treatment D1. So starch addition apparently enhanced the degradation of the 4 PAHs, especially InP and BghiP, by native microbes in the aged HMW PAH-polluted soil. By adding starch to these aged polluted soils with inoculated strain ZH-H2, HMW-PAHs degradation was further improved and addition of 0.5 g kg−1 starch to soils with 1.0 g kg−1 Fusarium ZH-H2 (D2 + H2) performed best to the 4 HMW-PAHs in all of these combination treatments by a factor of up to 3.09, depending on the PAH. We found that the highest polyphenol oxidase activities under D2 + H2 treatments are consistent with the results of removal rates of 4 PAHs. Our findings suggest that the combination of Fusarium sp. ZH-H2 and starch offers a suitable alternative for bioremediation of aged PAH-contaminated soil in coal mining areas, with a recommended inoculation size of 0.5 g Fusarium sp. ZH-H2 and addition of 0.5 g kg−1 starch per kg soil.

Changes in Polyphenol Oxidase Activity During Rooting of Hardwood Cuttings in Three Grape Rootstocks Under Indian Conditions

Polyphenol oxidase (PPO) activity was investigated during rooting in cuttings from the rootstocks Dog ridge, 110 R and St. George, belonging to different Vitis species. Enzyme activity and rooting ability were analysed. Significant differences were found in PPO activity among different rootstocks, with Dog ridge and 110 R having the highest PPO activity during the initial period of planting, followed by a decrease in enzyme activity. In St. George, the enzyme activity was least during the initial periods, but it increased throughout the experiment. The initiation of rooting primordia was observed until 60 to 90 days after planting in Dog ridge and 110 R rootstocks, while it was observed 120 days after planting in St. George, suggesting differences in the rooting behaviour of the rootstocks. The status of various biochemical components of the mother vines, such as total phenols, reducing sugars, carbohydrates, nitrogen, C:N ratio, etc. were analysed to investigate the influence of these constituents on the rooting ability of the rootstocks apart from PPO activity.