Role of pectin methylesterase in tomato fruit ripening and quality attributes of processed tomato juice

Abstract We have created transgenic tomato fruits with over a 10-fold reduction in pectin methylesterase (PME) activity by expressing a PME antisense gene. Reduction in PME activity does not interfere with the fruit ripening and vegetative growth of plants, but is associated with increases in soluble and total solids, mol. wt. and methyl esterification of pectins, and modifies accumulation and partitioning of cations between soluble and bound forms. The processed juice from transgenic fruits shows increases in serum and efflux viscosity and precipitate weight ratio. Ketchup prepared from transgenic fruits has a significant lower Botswick value, reduced serum separation and higher serum viscosity than control. Collectively, a marked improvement in fruit processing attributes results from lower PME activity in fruits.