Characterization of polyphenoloxidase (PPO) extracted from ‘Jonagored’ apple

Abstract

Polyphenoloxidase (PPO) was extracted from apple (cv. Jonagored) with addition of 2% PVP and 0.25% Triton X100 to the extraction buer containing phenolic adsorbents. Experiments were performed to evaluate the anity and speci®city towards several substrates. ÔJonagoredÕ apple PPO was found to have higher speci®city (lower K m) towards L-dopa, 4-methylcatechol and (+) catechin than other phenols tested, but the highest activity level was obtained with p-cresol. The ratio V max /K m indicates that p-cresol followed by L-dopa and 4-methylcatechol are the best substrates for ÔJonagoredÕ apple PPO. The enzyme activity showed two pH optima, at 5.0 and 7.5, at room temperature, with the main peak at pH 7.5 and the secondary one at pH 5.0 when catechol was the substrate.

Polyphenol oxidase activity and antioxidant properties of Yomra apple (Malus communisL.) from Turkey

“…It appears that crude PPO is sensitive to increases in temperature. Yomra apple PPO was almost inactivated 430 C in the presence of monophenol substrates, while diphenolic substrates were more activated 430 C. The optimal temperature values for PPO from persimmon fruits using 4-MCT, catechol and L-DOPA were 40 C, 20 C and 10 C, respectively 42 , 25 C from medlar with catechol as substrate 39 and 60 C from leaves of Cleome gynandra L. 47 . Polyphenol oxidase activities for Yomra apple were assayed using catechol, 4-MCT and L-DOPA as diphenolic substrates and L-tyrosine, HPPA as monophenolic substrates in this study.…”

“…Liquidliquid extractions with diethyl ether and ethyl acetate were then performed three times consecutively. Organic phases were picked up and evaporated until dry under reduced pressure in a rotary evaporator at 40 C. The residues were weighed and dissolved in methanol until used for HPLC analysis and antioxidant tests.…”

Effect of essential oils incorporated into an alginate-based edible coating on fresh-cut apple quality during storage

“…PPO activity was determined according to the method of Rocha and Morais (2001) and Soliva-Fortuny et al (2002). Enzyme activity was assayed spectrophotometrically by adding 3 ml of 0.6 M catechol (Sigma-Aldrich) and 75 μl of extract to a 4.5 ml quartz cuvette of 1 cm path length.…”

Efecto del tratamiento de escaldado sobre la actividad enzimática de la polifenoloxidasa en dos variedades de batata (Ipomoea batatas Lam.)

“…Entre los tratamientos para inactivar esta enzima están el uso de aditivos químicos, antioxidantes como vitaminas, agentes reductores como la cisteína, remoción de algún catalizador, irradiación y el escaldado que consiste en un tratamiento térmi-co medio aplicado a los vegetables por contacto con vapor o agua caliente en diferentes periodos. Se han llevado a cabo estudios para obtener las condiciones para inactivar la PPO en manzanas (Rocha y Morais 2001), pitaya amarilla (Castro et al, 2006), clavel (Mayorga e Higuera, 2007), aguacate (Amaya et al, 2008), gel de sábila (Cob et al, 2010), pera (Gasull y Becerra, 2010), papa amarilla (Trujillo et al, 2011), guacamole (Orozco et al, 2012), naranjilla (Samaniego et al, 2014, Montenegro, 2015, chicozapote (Vargas et al, 2015), entre otras.…”