Two-year comparison of the biochemical properties of polyphenol oxidase from Turkish Alyanak apricot ( Prunus armenica L.)

Comparison of biochemical properties and thermal inactivation of membrane‐bound polyphenol oxidase from three apple cultivars (Malus domestica Borkh)

“…For example, the optimum pH for PPO from strawberry, mango, banana and jackfruit has been reported to be 4.5, 5.4–5.6, 6.5 and 7.0, respectively (obtained using catechol as substrate; Jia et al ., ; Cheema & Sommerhalter, ; Tao et al ., ). Factors such as cultivar, substrate, prototropic groups at the enzyme active site and isoenzyme form have been shown to lead to the variation of the pH optimum of PPO from different sources (Ünal & Şener, ).…”

Biochemical Properties of Emir Grape Polyphenol Oxidase as Affected by Harvest Year

“…This procedure was repeated until a white powder was obtained. The residue from the repeated extractions was called acetone powder, which was dried overnight at room temperature and stored at -25 o C [1]. In order to obtain enzyme extract, 0.5 g of acetone powder was suspended in 37.5 ml of prechilled 0.1 M phosphate buffer (pH 6.…”

“…Unless otherwise stated, the standard reaction mixture consisted of 0.1 mL of enzyme solution and 0.9 mL of catechol in 0.2 M citric acid buffer (pH 5.49) for PPO 2006 and PPO 2007 . One unit of enzyme activity was defined as the amount of enzyme that caused an increase of 0.001 in the absorbance value per min under the assay conditions [1].…”

“…PPO 2006 retained more than 40% of the maximum activity at 80°C whereas that for PPO 2007 was more than 80%. The optimum temperature of PPO shows great variability depending on the enzyme source and the substrate used in the assay [1]. The reported optimum temperature values were 30 °C for banana PPO [7], 40 °C for honeydew peach [13], 45 °C for grape PPO [9], 55 °C for persimmon PPO [14].…”

“…The o-quinones formed by the action PPO interact with other molecules resulting in the formation of brown pigments. The reaction is detrimental to food quality and causes economic losses due to impairment in color, taste, flavor, and nutritional value [1]. The levels of PPO are linked to species, cultivar, maturity and age [2].…”