Enzyme inactivation of tomato juice by ohmic heating and its effects on physico-chemical characteristics of concentrated tomato paste.

Fresh juice of fully ripe tomato was subjected to ohmic heat (OH) treatment (908C for 1 min) and
the effectiveness of treatment was compared with conventional hot break (CT) treatment (908C
for 5 min). PG (Polygalacturonase) and PME (Pectin methyl esterase) enzyme inactivation achieved
by the OH (1 min.) was similar as compared to CT of 5 min. During the kinetic analysis it was
observed that the inactivation of PME & PG enzyme and degradation of ascorbic acid followed
first order trend in ohmic as well as conventional treatment of tomato juice, however total color
change (DE) was found to follow least-squares non-linear parameter algorithm behavior. Thermal
treatments leads to the increased release of phyto-chemicals from the matrix which results in a
significant (p<0.01) increase in lycopene content during the early phases of the treatments. The
Paste (2860.5 8Brix) obtained after pre-treatment was analyzed for lycopene, ascorbic acid content
and apparent viscosity and color. OH Paste was found more viscous than CT treatment with
maximum viscosity of 2.333103 mPa-s. The color of OH treated paste was bright red as compared
to CT treatment, however the lycopene and ascorbic acid content of paste were found
similar in OH and CT. Based on results of present study it is concluded that the ohmic treatment
may be applied as an efficient alternative to the conventional method of enzyme inactivation in
tomato juice.