• 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.

• The Plant Pathology Journal
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• v.39 no.2
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• pp.159-170
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• 2023

Spot blotch disease of wheat caused by Bipolaris sorokiniana (Sacc.) Shoem is considered as an economically important disease which affects all the growing stages of wheat crop. Therefore, it is important to search some effective management strategies against the spot blotch pathogen. Some synthetic elicitor compounds (salicylic acid, isonicotinic acid, and chitosan) and nano-particles (silver and aluminum) were tested against the pathogen to observe the change in biochemical activity and defense action of wheat plant against spot blotch disease. All the tested elicitor compounds and nano-particles showed a significant increase in activity of peroxidase, polyphenol oxidase (PPO), and total phenol over control. The highest increase in activity of peroxidase was recorded at 72 h from chitosan at 2 mM and 96 h from silver nano-particle at 100 ppm. Maximum PPO and total phenol activity were recorded from chitosan at 2 mM and silver nano-particle at 100 ppm as compared to pathogen-treated and healthy control. The lowest percent disease index, lowest no. of spots/leaf, and no. of infected leaves/plant were found in silver nano-particle at 100 ppm and chitosan at 2 mM, respectively. The use of defense inducer compounds results in significantly up-regulated enzymatic activity and reduced spot blotch disease. Therefore, chitosan and silver nano-particle could be used as alternative methods for the management of spot blotch disease.

• The Korean Journal of Food And Nutrition
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• v.24 no.3
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• pp.406-413
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• 2011

This study was carried out to investigate antioxidative properties of various extracts and antibrowning effects of extracts in apple slices were investigated by ${\Delta}E$ value and PPO relative activity. Apples were cut into 1.5 cm thickness and they were dipped in 1% extract solutions(OW: water extracts of onion, OE: 80% EtOH extracts of onion, AW: water extracts of apple, AE: 80% EtOH extracts of apple, MW: water extracts of mandarin orange peel, ME: 80% EtOH extracts of mandarin orange peel) for 1 min. OW showed higher than the other treatments for total phenolic contents(94.35 mg/g), PPO inhibition(74.00%). And the highest DPPH free radical scavenging activity(40.27%) measured in ME. ${\Delta}E$ value of apple slices dipped in MW was 2.37 whereas ${\Delta}E$ value of apple slices dipped in AW was 12.12. These results suggest that onion and mandarin orange peel extracts should be a potential source for controlling browning during storage of apple slices.

• The Korean Journal of Food And Nutrition
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• v.31 no.5
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• pp.689-695
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• 2018

This study was carried out to select apple cultivars suited for the fresh cutting or minimal processing as investigating correlation between total phenol and ascorbic acid as browning factors and the enzymatic browning degree. In soluble solid-acid ratio, 'Gamhong' and 'Arisoo' were highest value of 71.69 and 71.52 compared with other cultivars. And the change of lightness (${\Delta}L$) and color (${\Delta}E$) in 'Gamhong' and 'Arisoo' showed lower than other cultivars while 'Arkansas black' was highest change of lightness and color as ${\Delta}L$ 8.27, ${\Delta}E$ 13.86 respectively. Total phenol and ascorbic acid contents in 'Arkansas black' were highest such as 334.3 mg GAE/100 g and 9.22 mg/100 g, respectively. And polyphenol oxidase (PPO) activity also was the highest such as 14.43unit in 'Arkansas black'. The correlation test showed browning of apple was significantly dependent on ${\Delta}L$, ${\Delta}E$, total phenol, ascorbic acid contents and PPO activity (p<0.01). On the contrary, no significant correlation had been determined between the browning and ascorbic acid oxidase (AAO) activity. Thus, it seemed that the browning of apple was not only due to oxidation of ascorbic acid but also total phenol. It was suggested that 'Gamhong' and 'Arisoo' were suitable for fresh cutting or minimal processing.

• Korean journal of food and cookery science
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• v.28 no.3
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• pp.319-326
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• 2012

This study was designed to investigate the properties related to browning of hot water and 80% ethanol extracts of green tea (Camellia sinensis) and propolis. The extracts were assessed for polyphenol oxidase (PPO) inhibitory activity and total phenolic and flavonoid contents. In addition, apples were cut into 15 mm thick slices and dipped for 1 min in 0.5% of the green tea extracts and the propolis solutions and stored at room temperature for 24 h. The PPO inhibitory activity of the green tea extracts was better than that of the propolis. The highest DPPH free radical scavenging activity (90.81%), total phenol contents (170.42 mg/mL) and the metal chelating effects (45.93%) were measured in the green tea hot water extracts. The mineral content of the green tea water extracts was 69,328.44 ppm potassium and 2,409.42 ppm magnesium. After 24 h, the ${\Delta}E$ value of the apple slices treated with the green tea water extracts was the lowest (1.35). The antibrowning effects of the green tea extracts were higher than those of propolis in the apple slices.

• Korean Journal of Food Science and Technology
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• v.38 no.2
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• pp.183-187
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• 2006

Surface browning, caused by cutting and other wound during minimal processing, is very important quality criterion to consumers. Shelf-life of fresh-cut potatoes was extended using natural antibrowning treatments. Fresh-cut potatoes dipped with licorice and green tea extracts were packed with LDPE film and stored at $4^{\circ}C$ for 14 days. Quality characteristics of fresh-cut potatoes were investigated during storage. During storage, L value decreased and PPO activity increased. PPO showed the lowest activity at around 7 days storage, during which browning was effectively inhibited in licorice- and green tea extract-treated potatoes. Total phenol and chlorogenic acid contents increased for 7 days. Results suggest natural licorice extracts with ascorbic acids are effective antibrowning agents for maintaining quality of fresh-cut potatoes.

• The Korean Journal of Food And Nutrition
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• v.30 no.5
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• pp.853-859
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• 2017

This study was conducted in an effort to investigate the effect of Maillard reaction products (MRPs) on enzymatic browning of burdock and their anti-oxidant activity. The MRPs were prepared by heating glucose and amino acids at $90^{\circ}C$, which served to produce a strong inhibitory effect on burdock polyphenol oxidase. As the reaction time of the solution containing glucose and amino acid increased at $90^{\circ}C$, the production of MRPs increased and intensity of the brown color deepened. When MRPs were prepared by heating at $90^{\circ}C$ for five hours, the absorbance of MRPs from glucose and lysine was 6.44, while those of glucose and glycine was 1.95. The MRPs synthesized from the glucose and lysine also reduced the pH of MRPs from 5.60 to 4.51, but those from glucose and glycine decreased slightly from 5.57 to 5.33. The Michealis-Menten constant value ($K_m$) of burdock PPO with pyrocatechol as a substrate was 16.0 mM, and MRPs were a non-competitive inhibitor against burdock PPO. The anti-oxidant activity of MRPs was measured by evaluating its radical scavenging activities of DPPH radicals, ABTS radicals and reducing power. The color intensity of MRPs produced by lysine and glucose were deeper than that produced by glucose and glycine. It was also found that MRPs produced from glucose and lysine exhibited stronger anti-oxidant properties than those produced by glucose and glycine.

• 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.

• Current Research on Agriculture and Life Sciences
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• v.33 no.2
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• pp.65-68
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• 2015

Hunter's color value "a" in dried-persimmon of table and full ripe fruit was higher than that in unripe fruit. In case of soluble solid content, full ripe fruit was $50^{\circ}Brix$, the highest degree, while unripe fruit was $40^{\circ}Brix$, the lowest degree. PPO activation of unripe fruit was 4.7, which was higher than table-ripe fruit (0.7) and full ripe (1.0). Polyphenol oxidase activation remained even while drying, but there was no difference in PPO activation degree as drying period increased. Total phenol content of unripe fruit was 101.4, which was higher than table-ripe fruit (57.5) and full ripe fruit (67.4). Total phenol content level increased as drying period increased, which was based on fresh weight. Hardness of unripe and table ripe fruit continued to decrease until three weeks during softening. After that, hardness was high and it started drying. However, in full ripe fruit, hardness increased after two weeks and softening was fast during the drying period, and its weight reduction rate was lower than that of unripe and table ripe fruit.

• The Korean Journal of Food And Nutrition
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• v.33 no.4
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• pp.419-427
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• 2020

The purpose of this study was to investigate the qualitative changes of the citron by identifying the type of solution and addition of the solution to prevent the browning reaction of the citron in a way that inhibits the browning of the citron. The browning inhibitor solution was investigated using the individual and mixture, and the results of the degree of browning and chromaticity showed that vitamin C+NaCl+cyclodextrin (CD) had the lowest browning of 0.52. In chromaticity, the ΔE values indicate that the higher the value, the greater the change in color, and the lowest value of the vitamin C+NaCl+CD mixture was 47.0, indicating that there was minimal browning compared to other treatment. The active change of the polyphenol oxidase (PPO) in the citron increased enzyme activity as the browning progressed, and the vitamin C+NaCl+CD solution was the lowest at 68.40 μ/g among the anti-browning solution. Based on these research results, it seems that the CD mixing solution can be used as a citron browning inhibitor.