• Current Research on Agriculture and Life Sciences
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• v.1
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• pp.141-150
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• 1983

This report decribes the changes of internal browning and PPO in apples, when the method of storage was changed in the condition of low temperature. Internal browning was found more Fuji harvested in November than Fuji in October. The degree of internal browning was the highest during the storage of 0.09mm 2% and 0.06mm 2%, 0.06mm 20% was followed. In the subatmospheric storage with complete remove of $CO_2$ internal browning was not observed. During the storage of P.E. film bag, Fuji havested in November was higher than in October, and Fuji on 0.09mm 2% was higher than in 0.06mm, and Fuji during the storage of P.E. film bag was increased in PPO activity and PPO specific activity. During the subatmospheric storage with complete remove of $CO_2$, PPO activity of Fuji was little changed, but it's PPO specific activity was continuously decreased. PPO activity of Ralls was more higher than PPO activity of Fuji. PPO activity and PPO specific activity during the early stage of storage and the end stage of storage were little changed. Internal browning of Fuji was more effected $CO_2$ injury than chilling injury. There is no relation between internal browning and degree of PPO activity was effected by $CO_2$ and slightly related with internal browning.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.2
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• pp.187-195
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• 2008

Polyphenol oxidase (PPO) is implicated in discoloration of white salted noodles and other wheat based foods. PPO activity was evaluated to determine the effect on discoloration of noodle dough sheets prepared from 25 Korean wheat flours during storage and to screen experimental lines with low PPO activity in 52 Korean wheats. PPO activity was assayed with whole-seed and performed with L-dihydroxyphenylalanine (L-DOPA) as substrates. Absorbance by L-DOPA assay of 25 Korean wheats was from 0.285 to 1.368 at 475 nm. PPO activity was significantly related with grain characteristics, including 1000-kernel weight and grain colors. In flour characteristics, PPO activity positively correlated with ash and protein content (r = 0.658, P < 0.001 and r = 0.424, P < 0.05, respectively) and negatively correlated with $L^*$ value of flour (r = 0.412, P < 0.05). In the changes of color of noodle dough sheet, $L^*$ and $b^*$ values consistently decreased and $a^*$ value increased during storage. PPO activity negatively correlated with $L^*$ value of noodle dough sheet during storage (r = 0.566, P < 0.01 at 2 hr, r = 0.547, P < 0.01 at 24 hr, and r = 0.509, P < 0.01 at 48 hr). But, no significant relationship was found in between PPO activity, $a^*$ and $b^*$ values during storage. The 52 Korean wheat lines examined in this study were divided into 3 different groups, low (< 0.500), medium (0.501-0.999) and high level (> 1.000), on the basis of the level of PPO activity. Twenty two Korean wheat lines showed low level of PPO activity and Suwon 252, 277 and 280 showed lower PPO activity (< 0.200) than others.

• YAKHAK HOEJI
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• v.40 no.1
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• pp.65-71
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• 1996

Characterization of Polyphenol oxidase (PPO) in Perillae Folium, particullarly inhibitor studies were investigated. This enzyme was stable at pH 5.0 and the residual activity of PPO at ${\geq}$ ph 5.5 was estimated to be very low. PPO activity was decreased slightly by adding amino acid with catechol as a substrate, particullary PPO activity was inhibited markedly by cystein, histidine, lysine and arginine. In the absorption spectra of the product formed when catechol was oxidized by PPO, with a ${\lambda}_{max}$ at 410nm, the peak shifted toward ${\lambda}_{max}$ 520nm by addition of L-proline. At relatively low concentrations($10^{-3}M$), sulfite and dithiothreithol completely inhibited PPO activity. Inhibition of PPO activity by amino acids and inhibitors increased or decreased depending on the pH used to measure it.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.669-676
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• 1999

The effects of wounding and jasmonic acid(JA) on polyphenol oxidase(PPO) in tomato(Lycopersicon esculentum Mill.) seedlings were investigated. PPO was strongly induced by wounding or JA, and the response was also shown to be systemically induced by wounding. Mechanical wounding in cotyledon or leaf produced a signal that caused the concentration of PPO to increase in the unwounded cotyledon, in the first leaves but not in the second leaves. Severity of wounding and light intensity also affected wound induced change in PPO activity, JA showed a stimulatory effect on the loss of chlorophyll and the rapid increase in PPO activity. The PPO was clearly more active in the wounded leaves than in controls. The potency and specificity of the JA indicate a close relationship between JA and wound-induced changes in PPO in tomato species. JA and abscisic acid(ABA) acted similarly on both unwounded and wounded leaves, but the amount of PPO in the wounded leaves was always more than the respective controls. The highest increase in PPO activity occurred in woundand JA-induced leaves of seedlings kept under bright lighting. Benzyladenine(BA) completely abolished JA- and ABA-induced PPO activity. The results suggest that JA-induced PPO activity is due to de novo PPO synthesis. Histochemical tests for PPO in stems of wound- and JA -treated tomato plants indicate that PPO was localized primarily, in the. outer .cortex . and xylem parenchyma. It is concluded that exogenously applied JA acts as stress agents and PPO may be a component of the inducible anti-hervivore defense response.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.4
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• pp.231-240
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• 2000

Effects of Jasmonic Acid and Wounding on Polyphenol Oxidase Activity in Senescing Tomato Leaves The effects of jasmonic acid(JA) and wounding on polyphenol oxidase(PPO) during leaf senescence was investigated by measuring the PPO activity in detached tomato(Lycopersicon esculentum Mill.) leaves of two-week-old seedlings. The PPO activity in the detached senescing leaves increased significantly in the dark. The leaf segments responded to the application of JA with accelerated senescence, as indicated by the loss of chlorophyll and rapid increase in the PPO activity. The senescence-promoting action of JA differed in the light and dark. Wounding the detached senescing leaves by scraping surface segments or making punctures with needles considerably delayed the loss of chlorophyll and had a significant effect on the PPO activity, the amounts of which were roughly proportional to the intensity of the wounding. In the dark, the combination of wounding plus JA resulted in stable levels of chlorophyll and PPO. JA and ABA acted similarly in both unwounded and wounded leaves, however, the amount of chlorophyll and PPO in the wounded segments was always higher than in the respective controls. JA was found to eliminate the senescence-retarding action of benzyladenine. In a histochemical localization test, the PPO activity was found to be localized in the cell walls of the parenchyma tissue, thereby indicating moderate cytoplasmic reactions. In the JA-treated plants, the PPO activity was intense in the cells of the cortex and phloem parenchyma. Accordingly, based on these observations it would appear that PPO is a component of a defense response maker, whereas JA plays an integral role in the intracellular signal transduction involved in inducible defense mechanisms.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.142.3-143
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• 2003

Time-dependent PPO activity was determined at $4^\times$C and $30^\times$C. The result of activity determination, PPO extracted by phosphate buffer containing triton x-1l4(tPPO) was more stable than PPO by phosphate buffer(bPPO). The result of electrophoresis, at first a band was appeared at 48kd. After 1-3days a partial degrade band was appeared in bPPO and three partial degrade bands in tPPO. No activity band was appeared in PPOs at $30^\times$C and bPPO at $4^\times$C after 4 days. (omitted)

• 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.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.6
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• pp.1013-1016
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• 2004

The inhibitory effect of MRPs (Maillard reaction products) on enzymatic browning of taro was investigated. The MRPs prepared by heating glycine and glucose at 9$0^{\circ}C$ for 7 hr exhibited a strong inhibitory effect on taro polyphenol oxidase (PPO). The maximum inhibitory activity of MRPs against taro PPO was detected toward (＋)-catechin, catechol, 4-methylcatechol followed by L-$\beta$-3,4-dihydroxyphenylalanine (L-DOPA) and pyragallol as a substrate. The MRPs synthesized from fructose and glucose with glycine as a amino acid significantly reduced the taro PPO activity. MRPs prepared by higher glycine or glucose concentration showed stronger inhibition against taro PPO. Increasing reaction time of the glycine and glucose promoted the inhibitory effect of MRPs against the PPO activity of taro, whereas the color formation was gradually increased.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.6
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• pp.1301-1304
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• 2001

Deodorizing activity of polyphenol cxidase (PPO) extracted from apples was investigated by measuring the changes of methyl mercaptan as an indicator of halitosis in human mouths. In the studies of apple extracts on deodorizing activity, the deodorizing activity was increased with the amount of apple extracts. In the cases of adding PPO to the low molecular fraction of apple extracts, the deodorizing activities were increased with the amount of the law molecular fraction of apple extracts and the reaction time of the extracts with PPO. Deodorizing activities of PPO is thought that o-quinone as an intermidiate produced by an oxidative reaction of PPO during enzymatic browning reactions may react with methyl mercaptan to form a non-volatile and sulfur-containing compound .

• Journal of the Korean Society of Food Culture
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• v.10 no.2
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• pp.89-95
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• 1995

Three potato cultivars, Sumi,Daejima and Namjak, were prepared as slices. They were dipped in distilled water for 20 seconds. The potato slices were packed in polyethylene bags and stored at $5^{\circ}C$. Browning degree, total phenol and chlorogenic acid contents and polyphenol oxidase (PPO) activity were measured. And the correlation analysis of browning parameters were conducted. The results were as follows. There were increase in browning degree, phenolic content and PPO activity during cold storage of potato slices with different cultivars. Among three cultivars, Sumi showed the highest browning degree, phenolic content and PPO activity and also showed the highest % increse of browning and PPO activity during cold storage. On the contrary, Daejima was the lowest. But Daejima showed the highest % increase in phenolic contents during cold storage. With Sumi, browning degree was significantly correlated with PPO activity and phenolic contents (p<0.05). With Daejima and Namjak, a significant correlation was found between browning degree and PPO activity (p<0.05). From the above results, enzymatic browning reactions of potato slices and factors affecting them were dependent on cultivar. Among the tested three cultivars, Daejima showed the lowest browning degree during cold storage and thus seems to be desirable for minimal processing.