Effects of raw materials and process variables on the heat penetration times, firmness, and pectic enzyme activity of diced tomatoes (Halley Bos 3155cv)

I;rte effects of raw materials and process variables on the heat penetratio n times into diced tomatoes (Halley Bos 3155 cv) were evaluated. Variables included dice size (1.27 and 2.54 cm), maturity at harvest (red and red+2 w eeks), and processing temperature (88 and 92C). Heat penetration times betw een dice sizes were significantly different, but not between maturities or processing temperatures. Tomatoes were also evaluated for firmness, pectin- methylesterase (PME) and polygalacturonase (PG) activities. Half-inch size diced tomatoes were processed at 88 and 92C, and evaluated for firmness usi ng the shear-compression method. Firmness decreased to 60% of the initial r aw firmness from 8.8 x 10(5) to 5.3 x 10(5) g-mm after 15 s at 88C, and to 50% from 8.8 x 10(5) to 4.4 x 10(5) g-mm after 15 s at 92C. Diced tomato fi rmness showed a slight firming trend after 150 s at both temperatures. PME was inactivated after 45 s, while 5% residual PG activity remained after 3 min.