EFFECT OF GENETIC DOWN-REGULATION OF POLYGALACTURONASE AND PECTIN ESTERASE-ACTIVITY ON RHEOLOGY AND COMPOSITION OF TOMATO JUICE

Juices made from tomatoes containing antisense genes for the enzymes p olygalacturonase (PG(as)) and pectin esterase isoform 2 (PE(as)) were compared to those made from normal fruit. The juice from the PG(as) fr uit was thicker than that from the normal fruit. This increased viscos ity was shown to develop in a time-dependent manner and may involve th e continued action of PE in the juice post-homogenisation. The liquid phases of the juices did not differ greatly in viscosity and chemical composition indicating that it was the difference in the amount and na ture of the solids that was responsible for the differences in consist ency. Confocal microscopy and image analysis supported this hypothesis , showing that there were more intact cell-like structures present in the juice from genetically manipulated fruit. (C) 1998 SCI.