Reduced Polyphenol Oxidase Activity Research Articles

Polyphenol Oxidase Activity as a Potential Intrinsic Index of Adequate Thermal Pasteurization of Apple Cider

In response to increasing concerns about microbial safety of apple cider, the U.S. Food and Drug Administration has mandated treatment of cider sufficient for a 5-log reduction of the target pathogen. Pasteurization has been suggested as the treatment most likely to achieve a 5-log reduction, with Escherichia coli O157:H7 as the target pathogen. Regulators and processors need a reliable method for verifying pasteurization, and apple cider polyphenol oxidase (PPO) activity was studied as a potential intrinsic index for thermal pasteurization. The effect of pasteurization conditions and apple cider properties on PPO activity and survival of three pathogens (E. coli O157:H7, Salmonella, and Listeria monocytogenes) was studied using a Box-Behnken response surface design. Factors considered in the design were pasteurization conditions, i.e., hold temperature (60, 68, and 76° C), preheat time (10, 20, 30 s), and hold time (0, 15, 30 s), pH, and sugar content (° Brix) of apple cider. Response surface contour plots were constructed to illustrate the effect of these factors on PPO activity and pathogen survival. Reduction in PPO activity of at least 50% was equivalent to a 5-log reduction in E. coli O157:H7 or L. monocytogenes for cider at pH 3.7 and 12.5 ° Brix. Further studies, however, are needed to verify the relationship between PPO activity and pathogen reduction in cider with various pH and ° Brix values.

Effect of tuber storage and pre- and post-blanching treatments on the physicochemical and pasting properties of dry yam flour

In West Africa, yams are often processed into dry flour that is consumed as a thick paste (amala), the main quality attributes of which are colour, texture and taste. The traditional process consists of peeling, blanching and drying the fresh tubers. The fresh tubers may also be stored for several months before processing. This study was undertaken to test whether fresh tuber storage and pre- and post-blanching treatments (1-h storage of sliced fresh yam pieces in air or water and steeping in the blanching water, respectively) affect the physicochemical characteristics and pasting behaviour of dry yam flour produced from D. rotundata cultivars. Both pre-blanching treatments significantly reduced only peroxidase activity, while the post-blanching treatment significantly reduced polyphenoloxidase activity. Despite the effects on enzymatic activities, neither pre- nor post-blanching treatments had any significant effect on the amala brown index or the flour total phenol content. However, peak areas of three major cinnamic acid compounds, detected by HPLC, decreased continuously with steeping time after blanching, while fresh tuber storage led to a dramatic reduction in amala paste viscosity.

Enzymatic removal of phenols from aqueous solution by artichoke ( Cynara scolymus L.) extracts

The effects of extracts from artichoke ( Cynara scolymus L.) flower bracts on model wastewaters containing a range of phenolic contaminants have been studied. The extracts contained various isoenzymes of both peroxidase (POD) and polyphenol oxidase (PPO). HPLC measurements showed that the monophenol, 4-chlorophenol, was most effectively oxidized in the presence of both extract and hydrogen peroxide (H 2O 2), suggesting that this substrate was mainly being acted upon by POD. In similar experiments with l-dopa, an o-diphenol, the presence of H 2O 2 was not required for the efficient formation of insoluble melanins as PPO was more active in this case. Agitation of the reaction mixture favored oxidation by PPO by ensuring an adequate supply of oxygen to the enzyme. Conversely, bubbling with nitrogen greatly reduced PPO activity but did not affect POD. Some care was required to avoid the presence of large excesses of H 2O 2, which could lead to the inactivation of the enzymes. The results indicate that using a mixture of enzymes (and possibly also non-enzymic constituents) such as that found in artichoke extract, makes wastewater treatment with extract more effective and flexible than using either POD or PPO alone. Furthermore, artichoke extract was easy and simple to produce from a low value source making the method highly economical.

How blanching and drying affect the colour and functional characteristics of yam ( Dioscorea cayenensis-rotundata) flour

Colour and texture are important features of amala, a traditional thick paste obtained from dry yam flour. Tubers from eight yam cultivars were blanched at 65 °C for 20 min and dried at 40 °C for 5 days to test biochemical, thermal and pasting changes occurring during traditional yam flour processing. Blanching reduced peroxidase activity and drying reduced polyphenoloxidase activity, but total phenol content and the brown index of flour and of amala increased dramatically during the latter operations. The brown index of amala was significantly correlated with the total phenol content of the flour ( r=0.84) and the peroxidase activity of the fresh tubers ( r=0.75). Amylose content and starch gelatinization enthalpy remained stable. For all cultivars, drying significantly increased the onset gelatinization temperature, suggesting the occurrence of starch annealing. The latter leads to a reduction in swelling power and solubility during pasting, and hence to a lower paste viscosity.

Reduced Polyphenol Oxidase Activity in Transgenic Potato Plants Associated with Reduced Wound-Inducible Browning Phenotypes

ABSTRACTIn potato the polyphenol oxidase (PPO) mediated wound-inducible browning phenotypes is one of the major drawback for food industry. In order to investigate and reduce PPO's expression for browning we obtained the potato specific PPO cDNAs using Vicia faba L. specific (Locus VVU 83274) primers and cloned them under control of the cauliflower mosaic virus 35S promoter. Transgenic potato plants (Solanum tuberosum L.) that show down expression of PPOs were obtained using Agrobacterium mediated transformation. Wounded transgenic plants with reduced PPO activity exhibited a great amount of reduced browning when compared with their control plants. Our results confirm the importance of PPO mediated phenolic oxidation in browning discoloration of potato suggesting the possibility of manipulation of PPO expression

Aparência, compostos fenólicos e enzimas oxidativas em uva 'Itália' sob influência do cálcio e do armazenamento refrigerado

O objetivo deste trabalho foi determinar o efeito da aplicação pré-colheita de cálcio na aparência (secamento do engaço, danos mecânicos e podridões), teor de fenólicos e enzimas oxidativas (polifenoloxidase e peroxidase) em uva. Os cachos de uva 'Itália' de um cultivo comercial em Petrolina, Pernambuco, Brasil, foram marcados e imersos por 10 segundos, em soluções de Ca a 0 e 1,5%, na forma de cloreto de cálcio, aos 57 dias após o início da formação dos frutos (quando as bagas começaram a mudar de cor e amolecer). Após a colheita, os frutos foram armazenados a 3,5±0,2°C e 93±6% UR e avaliados aos 0; 14; 28; 42; 56 e 70 dias. Houve um incremento no secamento do engaço, no aparecimento de sintomas de danos mecânicos e de podridões nas bagas com o tempo de armazenamento. A aplicação de cálcio reduziu a atividade de polifenoloxidase e, conseqüentemente, os sintomas de danos mecânicos, resultando numa melhor aparência. A vida útil das uvas foi de aproximadamente 56 dias, quando sintomas de senescência, podridões e o nível dos sintomas de danos mecânicos começaram a aumentar de forma significativa.

A transgenic apple callus showing reduced polyphenol oxidase activity and lower browning potential.

Polyphenol oxidase (PPO) is responsible for enzymatic browning of apples. Apples lacking PPO activity might be useful not only for the food industry but also for studies of the metabolism of polyphenols and the function of PPO. Transgenic apple calli were prepared by using Agrobacterium tumefaciens carrying the kanamycin (KM) resistant gene and antisense PPO gene. Four KM-resistant callus lines were obtained from 356 leaf explants. Among these transgenic calli, three calli grew on the medium containing KM at the same rate as non-transgenic callus on the medium without KM. One callus line had an antisense PPO gene, in which the amount and activity of PPO were reduced to half the amount and activity in non-transgenic callus. The browning potential of this line, which was estimated by adding chlorogenic acid, was also half the browning potential of non-transgenic callus.

Combined effect of high pressure, temperature and holding time on polyphenoloxidase and peroxidase activity in banana (Musa acuminata).

Polyphenoloxidase and peroxidase enzyme activities were evaluated following combined pressure, temperature and holding time treatment in banana (Musa acuminata). Using pressures of up to 110 MPa, temperatures of up to 70 °C and holding times of up to 25 min, based on a 23 central composite design, the interactive effects were found to significantly influence the activity of both enzymes in prepared banana pulp. Temperature and pressure were found to influence the inactivation of polyphenoloxidase separately, while temperature, pressure and holding time were found to influence the loss of peroxidase in the banana, although no significant interactive effects were found. The reduction in polyphenoloxidase activity was found to be less influenced by the combined treatment than peroxidase activity, thought to be due to solubilisation of the enzyme and effects of the soluble solids content. © 2000 Society of Chemical Industry.

Age-Dependent Effects of Jasmonic Acid Treatment and Wind Exposure on Foliar Oxidase Activity and Insect Resistance in Tomato

Jasmonic acid (JA) treatment of tomato plants induces several defense-related oxidative enzymes and increases pest resistance in a manner thought to simulate natural insect wounding. In a full-factorial greenhouse experiment, we examined the independent and interactive effects of plant age and exposure to wind-induced mechanical stress (MS), on the ability of JA to induce defense in tomato. In general, treatment of 4-, 6-, and 8-week-old tomato plants with 1 mM JA resulted in the induction of peroxidase and polyphenol oxidase activity and reduced the relative growth rate of first-instar Manduca sexta larvae fed treated leaves, in accordance with other studies. Peroxidase activity increased with plant age and was induced by JA most strongly in older plants. In contrast, polyphenol oxidase activity did not change with plant age and was induced by JA most strongly in young plants. While relative growth rates of M. sexta were lower on older plants overall, JA reduced growth rates most strongly in young plants, in which JA treatment enhanced polyphenol oxidase activity by more than 70%. MS enhanced the activity of peroxidase, but substantially reduced the activity of polyphenol oxidase; the latter most intensely on older plants. M. sexta tended to grow more slowly on MS-treated plants, although this effect was not significant. Thus, reduced polyphenol oxidase activity in MS-treated plants did not lead to an increase in growth rate of M. sexta, possibly because peroxidase activity was still elevated in MS-treated plants. Significant interactions between JA and MS and three-way interactions were not detected for any variable, although the inductive effects of both JA and MS interacted in complex ways with plant age. Our results indicate that resistance traits in tomato are differentially affected by JA and wind exposure and differ in their relative contribution to defense as plants age.

Oxidative stress injury in tomato plants induced by supplemental UV-B radiation

Tomato (Lycopersicon esculentum Mill. cv. PKM 1) plants growing under field conditions were exposed for 15 d to solar radiation with UV-B component (280 - 320 nm) enhanced to 6.3 kJ m-2 d-1. This simulated a 15% stratospheric ozone depletion over Madurai (9° 50' N latitude). Lipid peroxidation in the leaves of UV-B treated plants was 32% higher compared to the control. Superoxide dismutase (SOD) and catalase activities registered parallel promotion by 126 and 50 %, respectively, in the UV-B treated plants. Further, the contents of total phenols and anthocyanins in the leaves have also been enhanced by 40 and 156%, respectively. On the contrary, polyphenol oxidase activity demonstrated a 58 % inhibition in the leaves of UV-B treated plants. While anthocyanins and phenols are proposed to act as antioxidants, the reduction in polyphenol oxidase activity may maintain the turnover of phenols in the UV-B treated plants.

Prediction of Polyphenol Oxidase Activity in Model Solutions Containing Various Combinations of Chlorogenic Acid, (−)-Epicatechin, O2, CO2, Temperature, and pH by Multiway Data Analysis

Controlled or modified packaging (CA/MA) of lettuce is simulated in model solutions containing lettuce polyphenol oxidase (PPO), chlorogenic acid (CG), and/or (−)-epicatechin (EPI) under various combinations of CO2, O2, N2, temperature, and pH conditions. Enzymatic browning is measured by PPO activity, color formation, substrate consumption, and development of products. Results were analyzed by multiway data analysis. CO2 minimized the chemical polymerization and reduced PPO activity slightly. CG was a better substrate for PPO than EPI. CG was, in particular, involved in the primary enzymatic catalyzed oxidation, whereas EPI was important for the subsequent chemical polymerization in mixtures of CG and EPI. A very descriptive five-parameter multiplicative model was obtained from the PPO data by the multivariate method PARAFAC. This model describes the importance of substrate, atmospheric composition, pH, and temperature for PPO activity. Low pH (3.0) reduced PPO activity strongly (89%), whereas low temper...

Characterisation of a Variegated Grapevine Mutant Showing Reduced Polyphenol Oxidase Activity

Fruit of the variegated grapevine mutant Bruce's Sport is known to dry to a lighter colour than other seedless varieties. The biochemical basis for this decreased browning capacity was investigated. Bruce's Sport grapes had similar levels of phenolic compounds to Sultana H5. Activity of the enzyme polyphenol oxidase (PPO EC 1.10.3.1) in mature berries of Bruce's Sport was only 20-30% of that in Sultana H5. No evidence of inhibitors or activators of PPO was found when berry extracts were mixed. PPO activity on a fresh weight basis was highest in the grape seed traces, intermediate in the skin, and lowest in the pulp in both varieties. In each tissue type, however, PPO activity in Bruce's Sport was less than 25% of that in Sultana H5. On a fresh weight basis, PPO activity in Sultana H5 berries was high at fruit set then declined as the berry developed. PPO activity per berry increased from fruit set until veraison, then remained constant. PPO activity showed similar changes during development of Bruce's Sport berries but was lower than in Sultana H5 at all stages. The Bruce's Sport grapes were variegated and the green regions of skin had similar PPO activity to Sultana H5 skin while the white regions had very low activity. Only the green regions of skin of Bruce's Sport grapes stained for PPO activity with endogenous or exogenously applied phenolic substrates. The decreased browning in this grapevine mutant apparently results from decreased levels of PPO activity in the white regions of the berry, possibly arising from a disruption in chloroplast development.

Promotion of adventitious root formation by 4-chlororesorcinol: A polyphenol oxidase inhibitor

The extent of rooting in cuttings of Phaseolus vulgaris L., and Vigna radiata Wilcz. was affected by 4-chlororesorcinol, a polyphenol oxidase inhibitor. More root primordia and more roots were formed after 4-chlororesorcinol treatment both with and without 10-5M Indole butyric acid. Promotion of rooting was observed also in cuttings of Elaeagnus pungens, Gypsophilia elegans and Kalanchoe blossfeldiana. The enhancement in bean and mung bean was accompanied by a concomitant wider spatial distribution of the primordia and the resulting adventitious roots. The formation of primordia in the treated cuttings was delayed by 12–24 hours, compared to untreated cuttings. The treatment was effective only when given during the first hours after the preparation of the cutting of bean and mung bean, suggesting involvement in the initiation stage. Hypocotyl extracts of mung bean cuttings, pretreated with 4-chlororesorcinol, exhibited reduced polyphenol oxidase activity. The inhibition was not reversed by washing of the treated extract in 50% acetone or by an overnight dialysis, suggesting tight or maybe even irreversible binding of the inhibitor to the enzyme.

Reduction of polyphenoloxidase activity in peaches sprayed with alar, ethrel or gibberellic acid

The failure of Early Amber peaches which had been field sprayed with Alar, Ethrel or gibberellic acid to darken as expected when cut is due to a 90 per cent reduction in the activity of polyphenoloxidase (EC 1.10.3.1) in the mature fruit. The possibilities that the reduced darkening might be due to the formation of a spray-induced reversible inhibitor or inactivator, to reduced substrate levels, or to elevated ascorbic acid levels were shown to be untrue.

The relation between polyphenoloxidase activity and ability to produce indoleacetic acid in Fusarium-infected tomato plants

Different protein fractions precipitated with ammonium sulphate from extracts of healthy andFusarium-infected tomato plants showed a linear relationship between polyphenoloxidase activity and ability to form indoleacetic acid (IAA) from tryptophan in the presence of chlorogenic acid. Dialysis slightly reduced polyphenoloxidase activity of as well as IAA formation by crude and purified extracts.