The effect of pulsed electric field on ascorbic acid content in tomato juice

Tomato based products have high nutritional value , amazing color , desirable flavor and high stability . Application of an appropriate processing method is needed to preserve the quality of these kinds of products . Todays , to produce the high - quality food products , novel thermal and non - thermal treatments are applied . In this study , a continuous pulsed electric field system equipped with infrared irradiation ( IR) was designed and constructed . Effect of this novel tomato juice processing method on ascorbic acid content was investigated . Some mathematical and kinetic models were also used to describe the ascorbic acid degradation .

The square-bipolar wave with 1 ms width at a constant frequency ( 32 Hz ) was applied during pulsed electric field treatment . Two stainless steel electrodes , 10 mm in length and 0.5 mm in width were used in the pulsed electric field chamber . At first, tomato juice ( 30℃ ) was preheated up to 40 , 45 and 50 ℃ ; the sample was then pulsed electric field processed at 22.73 , 27.27 , 31.82 and 36.36 kV/cm for 1173 to 3520 μs . ascorbic acid content was measured using the iodine titration method .

infrared irradiation preheating up to 40 , 45 and 50 ℃ resulted in 11.41 %, 16.39 % and 19.01 % decrease in ascorbic acid content. Higher vitamin degradation was observed when higher pulsed electric field strength and longer processing time . Models such as first - order semi – logarithmic , simplified Hulsheger , Fermi and Hulsheger were applied to study the effect of process conditions on ascorbic acid degradation .

ascorbic acid content significantly reduced during infrared irradiation pre-heating . First - order semi - logarithmic model was useful in studying the effect of pulsed electric field treatment time on ascorbic acid degradation . Considering the high correlation coefficient and low standard error , simplified Hulsheger was selected as the best one in describing the reduction in this vitamin content in relation to changes in pulsed electric field strength . Hulsheger model was also effective in predicting the vitamin degradation at different pulsed electric field strength and process time . It can be concluded that the applied pulsed electric field strength and processing timed should be controlled to prevent from more heating up the juice by considering the ohmic heating effect .