25-08-2017, 09:32 PM
The present work was undertaken to study the PPO activity, its extraction, downstream processing and characterization in cereals such as wheat (Triticum aestivum) and fruits like amla (Emblica officinalis) and banana (Musa acuminata). The PPO activity was measured using catechol as a substrate by spectrophotometric method. The increase in absorbance was measured as a function of time at 420nm.
Polyphenol oxidase (PPO) is believed to be ubiquitous in the plant kingdom. It has been detected in most known plants and vegetables. Enzymatic browning occurs as a result of the oxidation by PPO and is a limiting factor in the handling and technological processing of crops as peeled, sliced, bruised or diseased tissues rapidly undergo browning causing deterioration in food quality by changing the nutritional and organoleptic properties. These reactions significantly diminish consumer acceptance, storage life and value of the plant products. Owing to its tremendous economic importance in food industry, inhibition of PPO has been widely studied.
The present work was undertaken to study the PPO activity, its extraction, downstream processing and characterization in cereals such as wheat (Triticum aestivum) and fruits like amla (Emblica officinalis) and banana (Musa acuminata). The PPO activity was measured using catechol as a substrate by spectrophotometric method. The increase in absorbance was measured as a function of time at 420nm.
Characterization of PPO was undertaken to determine its action on selected polyphenolic substrates as well as to determine optimum-pH, optimum temperature of activity as well as the kinetic constants Km and Vmax. The khandwa wheat variety showed an activity of 380 U/g, Lokvaan showed an activity of 220U/g and the Punjab Pissi variety showed an activity of 200U/g. Banana showed an activity of 447.4U/g and amla had an activity of 190U/g. The optimum pH for wheat varieties was found to be in the range of pH 5.5 – 6.5 and of banana was pH 6.8. The optimum temperature of activity for banana PPO was 35°C. The Km value for wheat was 0.9mmol/ml and for banana was found to be 1.6mmol/ml.
The inhibition of PPO activity was studied using various inhibitors like ascorbic acid, EDTA, L-Cysteine, -cyclodextrins, citric acid and oxalic acid. Their individual as well as their combinatorial effect was also studied. Oxalic acid, ascorbic acid and citric acid gave maximum inhibitory effect on banana, wheat and amla PPO activity. The effect of PPO activity on the quality and the extent of browning in the products prepared from them viz. chapatti dough, osmotically dehydrated amla and banana puree was also studied.