• Food Science and Biotechnology
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• v.16 no.3
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• pp.421-425
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• 2007

The inhibitory effect of onion extract on polyphenol oxidase (PPO) and browning of peach juice was investigated. Various reducing agents such as L-ascorbic acid, L-cysteine, dithiothreitol, glutathione, and sodium pyrosulfite strongly inhibited polyphenol oxidase extracted from peach. The enzyme was also inhibited by addition of water extract of onion. Regardless of substrates used, the addition of heated onion extract exhibited stronger inhibitory effect on peach polyphenol oxidase activity than that of the fresh one. The inhibitory effect of onion extract was dependent on heating temperature and time. The onion extract inhibited the peach polyphenol oxidase non-competitively. The heating of onion extract in the presence of glucose, glycine stimulated the inhibitory effect of the onion extract, which suggests non-enzymatic browning products produced during heating might be responsible for the stronger inhibitory action of the heated onion extract. The retardation of peach juice browning by onion extract seems to be caused by inhibition of peach PPO.

• Journal of Life Science
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• v.22 no.11
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• pp.1451-1455
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• 2012

The study was conducted to investigate the effect of Maillard reaction products (MRPs) on enzymatic browning of crown daisy (Chrysanthmum coronarium var. spatiosum). The MRPs prepared by heating various amino acid and sugar at $90^{\circ}C$ caused a strong inhibitory effect on crown daisy polyphenol oxidase (PPO, ${\sigma}$-diphenol oxygen oxidoreductase, EC 1.10.3.1). As the reaction time of the solution containing glycine and glucose increased at $90^{\circ}C$, the production of MRPs was increased, whereas the amounts of glycine and glucose were decreased. Accordingly, the inhibitory effect of crown daisy PPO activity by MRPs was increased as the amounts of synthesized MRPs were increased. The MRPs synthesized from the various amino acids and sugars significantly reduced the PPO activity, particularly MRPs prepared by glutamine and xylose. The Michealis-Menten constant value ($K_m$) of crown daisy PPO with catechol as a substrate was 22.0 mM, and MRPs were a noncompetitive inhibitor against crown daisy PPO.

• Journal of the Korean Society of Food Science and Nutrition
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• v.16 no.2
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• pp.110-117
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• 1987

Polyphenol oxidase in Prunus salicina(Red) was extracted, some properties and its partially purification were investigated as follows; Polyphenol oxidase was purified about 15 folds after ammonium sulfate saturation and about 64 folds after Sephadex G-100 column chromatography. Polyphenol oxidase showed optimum pH for activity at 6.5 and optimum temperature at at $35^{\circ}C$ and high affinity to catechol in o-diphenol compounds. Thermal stability were about 85% and 75% of initial polyphenol oxidase activity remained after heating at $50^{\circ}C$ for 5 minutes and 30 minutes respectively. The Michaelis constant of the enzyme was 2.58mM. L-cysteine, glutathione, ascorbic acid and potassium cyanide appeared to be most effective inhibitors. EDTA showed a slight inhibition.

• Journal of Life Science
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• v.16 no.5
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• pp.866-869
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• 2006

The inhibitory effect of pine needle (Pinus densiflora S.) on potato polyphenol oxidase (PPO) was investigated. The addition of the pine needle extract exhibited a higher inhibitory effect on the potato polyphenol oxidase activity than that of the citric acid or potassium sorbate. The enzyme activity was strongly inhibited in a pH range of 7.0-8.0. When the incubation time of reaction mixture was increased, the potato polyphenol oxidase activity was markedly inhibited. The pine needle extract inhibited the potato polyphenol oxidase non-competitively. And also the pine needle extract subjected to a heat treatment at $100^{\circ}C$ for 10 min or to an acid treatment at pH 2.0, 3.0, and 4.0 for 3 hours still retained inhibitory effect on potato polyphenol oxidase.

• Korean Journal of Breeding Science
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• v.43 no.5
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• pp.470-478
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• 2011

This study was carried out to find major factors affecting the color of wheat flour and noodles and develop simple analysis method for the breeding of wheat cultivars suitable for producing flour and noodles with bright color which are preferred by consumers. Customers who buy white noodle or flour prefer bright-colored food to dark-colored products. We evaluated grains of 25 Korean wheat cultivars for chemical composition, grain characteristics, and color change of noodle dough sheets during storage. Polyphenol oxidase (PPO) has been connected to discoloration of white salted noodles and other wheat end products. The grain PPO activity was reduced as the 1,000 grain weight, grain ash content, and protein content decreased. The grain PPO activity was positively correlated with the total polyphenol content ($r=0.609^{**}$) and iron content ($r=0.655^{**}$). Lightness, protein, polyphenol and Fe content of flour were positively correlated with PPO activity of grain. Cultivars with higher grain PPO activity showed darker noodles and were more easily discolored during the storage (from 2 hr to 48 hr). Thus, PPO activity can be used as a selection index in a breeding program for wheat cultivars of bright-colored flour.

• Current Research on Agriculture and Life Sciences
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• v.4
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• pp.55-64
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• 1986

Polyphenol oxidase in japanese pear (Pyrus communis var. mansamkil) was isolated, partially purified and its some properties were investigated. Polyacrylamide disc gel electrophoresis indicated two bands with polyphenol oxidase activity in the extract from acetone dry powder of par flesh. These two polyphenol oxidases (PPO A and PPO B) were purified through acetone precipitation and diethylaminoethyl cellulose column chromatography. PPO A and B were purified 7.8 fold and 8.7 fold by the present procedure, respectively. The Rm values of partially purified PPO A and B were estimated to be 0.58 and 0.68, respectively. The optimum temp, and pH of PPO A activity were $33^{\circ}C$ and pH 7.0, while those of PPO B were $30^{\circ}C$ and pH 4.2, respectively. Two PPO were unstable over the temperature of $60^{\circ}C$. The substrate specificity of pear PPO showed high affinity toward o-diphenolic compounds, especially catechol in PPO A and chlorogenic acid in PPO B, but inactive toward m-diphenol, p-diphenol and monophenols. PPO A showed affinity toward the trihydroxyphenolic compound. $Zn^{{+}{+}}$ activated the PPO A activity but $Fe^{{+}{+}}$ inhibited PPO B activity, while $Fe^{{+}{+}}$ and $Zn^{{+}{+}}$ activated the PPO B activity, while $Fe^{{+}{+}}$ and $Zn^{{+}{+}}$ activated the PPO B activity but $K^+$, $Mg^{{+}{+}}$, $Ca^{{+}{+}}$ and $Hg^{{+}{+}}$ inhibited at 10mM concentration. $Cu^{{+}{+}}$ activated the enzyme action at low concentrations but inhibited at high concentration. Inhibition studies indicated that L-ascorbic acid, L-cysteine and thiourea were most potent. The Km values of PPO A and PPO B for catechol were 20mM and 14.3mM, respectively.

• Korean journal of food and cookery science
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• v.10 no.1
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• pp.24-28
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• 1994

The effects of synthetic and carrot carotene on the browning of polyphenolics extracted from potato for eliminating the effects of other components in potato which inhibit the browning of potato juice and the potato polyphenol oxidase (PPO) activity were investigated. Total phenolics content in potato sample was 1.854mg/g D.W. and PPO activity was 100 unit. Delta 'L'value of polyphenolics extracted from potato decreased makedly, but that of potato with carrot decreased little by little. Potato with P-carotene showed a little decrease after 50 min. At the same time, polyphenolics extracted from potato were mixed with carotene extracted from carrot or with syntetic $\beta$-carotene. As the results, the delta 'L'value of the former increased but decreased similarly to the latter after 1 hour. The effects of enzyme and substrate concentration on the browning of PPO extracted from potato were investigated. Optimum enzyme concentration was 10% and optimum substrate concentration was 13.3% $\beta$-carotene concentration did not appear to influence significantly on PPO activity.

• YAKHAK HOEJI
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• v.30 no.5
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• pp.220-227
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• 1986

Polyphenol oxidase was purified from an extract of tea leaf by ammonium sulfate fractionation followed by Sephadex G-150 column chromatography, which resulted in a 67-fold increase in specific activity. The enzyme had optimum pH 6.5 and was relatively heat stable. The substrate specificity of the tea leaf PPO showed high affinity toward pyrogallol and catechol. Potassium cyanide, sodium diethyldithiocarbamate, L-cysteine, 2-mercaptoethanol and ascorbic acid were potent inhibitors.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.6
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• pp.1041-1046
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• 2001

Solutions of fructose, glucose and sucrose were heated without catalyst at various temperature for different length of time. Changes in the formation of early caramelization product and browning intensity as well as pH of heated sugar solutions were determined. Reducing powers of caramelization products (CP) and their inhibitory effects on polyphenol oxidase (PPO) were also determined and their correlations were discussed. The early CP and browning intensity increased with temperature and time, in the order of heated fructose>sucrose>glucose solutions (p<0.005), while pH decreased. pHs of sugar solutions heated at 20$0^{\circ}C$ showed in the range of 3.32 ~ 3.50. Reducing power of CP as well as their inhibitory effect on PPO also increased with temperature and time, respectively. Among sugar solutions, reducing power showed the same trends as above at both 15$0^{\circ}C$ and 17$0^{\circ}C$ (p<0.001). However, those of heated fructose solutions were the highest in the early stage, while those of heated sucrose solutions were the highest in the final stage at 20$0^{\circ}C$. This is due to the difference in CP formed. Sucrose solution heated at 20$0^{\circ}C$ showed the highest inhibitory effect, reducing PPO activity by 34.6%. From these results, it is considered that the inhibitory effect of CP on PPO is partly related to their reducing power.

• Food Science and Preservation
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• v.12 no.5
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• pp.489-495
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• 2005

Polyphenol oxidase (PPO) from Burdock (Arctium lappa L.) was purified and characterized. Purification of polyphenol oxidase was achieved by ammonium sulfate precipitation, Phenyl-sepharose CL-4B hydrophobic chromatography and Sephadex G-100 gel filtration chromatography. The molecular mass of the purified PPO was estimated to be 30 kDa by SDS polyacrylamide gel electrophoresis. In a substrate specificity, maximum activity was achieved with chlorogenic acid, followed by catechol and catechin. Whereas, there was low activity with hydroquinic acid, resorcinol or tyrosine. The optimum pH and temperature for enzyme activity were 7.0 and 35$\circC$ with catechol, respectively. The enzyme was most stable at pH 7.0 while unstable at acidic and alkaline pH. The enzyme was stable when heated to 40$\circC$. But heating at 50$\circC$ for more than 30 min caused 50% loss of activity. Ascorbic acid, L-cystein and $Cu^{2+}$ inhibited the activity of pholyphenol oxidase.