• Food Science and Biotechnology
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• 제16권3호
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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.

• Food Science and Biotechnology
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• 제18권4호
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• pp.878-883
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• 2009

In Brazil canned 'Biuti' peach is a very popular form of this sub-tropical fruit. This production represents an important economic agro-activity in Minas Gerais, Brazil during the summer period, in preparation for the Christmas celebrations. The aim of this work was to characterize the 'Biuti' peach polyphenoloxidase (PPO), since peach products show enzymatic oxidation of the polyphenols by oxidative enzymes, which affects the products during their shelf life. Two different hypothesis for the browning problem in processed peaches were studied: the inadequacy of the blanching treatment and the presence of a latent phenolase in the peaches. The PPO was characterized: pH optimum (5.5) and stability (5.5-6.5); optimum temperature at $20^{\circ}C$ and 80% of the activity retained after 30 min at $15-40^{\circ}C$. The test for the presence of latent PPO in the processed and canned peaches was negative. Ascorbic acid, ${\beta}$-mercaptoethanol, sodium metabisulfite, and cysteine were efficient in inhibiting the PPO.

• Applied Biological Chemistry
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• 제35권2호
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• pp.82-86
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• 1992

복숭아로부터 polyphenoloxidase를 추출하여 polyphenol 화합물인 caffeic acid, hydroxyhydroquinone, homocatechol 그리고 pyrogallol과 반응시켜 얻어진 4종류의 효소적 갈변반응 생성물의 생리작용을 검토한 결과 rec-assay와 돌연변이원성시험에서 돌연변이원성을 나타내지 않았다. 4종류의 시료모두 S-9Mix를 첨가한 돌연변이원성 억제활성 실험에서 B(a)p, Trp-P-1의 변이물질에 대한 Ca-PEBRP와 HCa-PEBRP가 80% 이상의 강한 돌연변이원성 억제활성을 나타내었음을 알 수 있었다. 또한 rec-assay에서도 강한 대조구인 MMC와 MNNG에 대해 Py-PEBRP경우 생육저지대차를 17 mm에서 5 mm로 감소시켜 돌연변이 억제활성이 있는 것으로 나타났고, Hca-PEBRP, HHQ-PEBRP 그리고 Py-PEBRP에 $Zn^{2+}$의 첨가로 생육저지대의 차가 5 mm로써 DNA 손상에 영향을 미치는 것으로 나타났다.

• 한국식품저장유통학회지
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• 제7권1호
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• pp.103-107
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• 2000

Previously , the methanolic extract of peach sees was found to have a strong tyrosinase inhibitory activity in an in vitro assay. Several phenolic compunds were isolated from the seeds by solvent fractionation , Sephadex LH-20 chromatography, and preparative HPLC , and one of them showing strong tyrosinase inhibition was identified as benzoic acid by UV, IR, $^1$H/$^1$$^3$C-NMR, and EI-MS spectrsopy. Benzoic acid (IC50= 250$\mu\textrm{g}$/ml) and L-ascorbic acid (IC50=28$\mu\textrm{g}$/ml), well-known tyrosinase inhibitors. In particular , benzoic acid inhibited markedly the enzymatic browing (melanosis) of apple juices at low concentration of 0.01% and 0.05, comparable to that of L-ascorbic acid (P<0.05). these results suggest that benzoic acid, one of an effective food preservatives, may be potentially useful as a functional alternative to sulfites for the control of melanosis in fruit juices.