Effects of controlled-frequency moderate electric fields on pectin methylesterase and polygalacturonase activities in tomato homogenate

• Published in: Food chemistry 2016-05, Vol.199, p.265-272
• Main Authors: Samaranayake, Chaminda P., Sastry, Sudhir K.
• Format: Article
• Language: English
• Subjects: Carboxylic Ester Hydrolases - metabolism; Electric field frequency; Electricity; Food matrix; Lycopersicon esculentum; Lycopersicon esculentum - enzymology; Moderate electric fields; Pectin methylesterase; Polygalacturonase - metabolism; Polygalcturonase; Temperature
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2015.12.010

•Oscillating electric fields show nonthermal effects on enzyme activity.•Activity of some enzymes can be significantly reduced by moderate electric fields.•The effective frequencies for activity correspond to displacements of the enzymes.•In the homogenate, the pectic enzymes co-locate with the solid matter. The effect of controlled-frequency moderate electric field treatments on pectin methylesterase and polygalcturonase activities in tomato homogenate was investigated by subjecting identically treated control and electrically-treated samples to the same temperature history. Additionally, a model was developed for the motion of the enzyme molecules subjected to an electric field. Results show that the application of electric fields at a low field strength (0.4V/cm) constant temperature (65°C) has a statistically significant effect on pectin methylesterase activity, typically at or lower than 60Hz. At higher frequencies, the effects are negligible. Molecular motion simulations suggest that the efficacy at low frequencies may be due to the amplitude of motion being of the order of the intermolecular distance for water. Higher frequencies result in small overall displacements due to rapid reversals in the direction of motion.