Effect of Thermal Treatment on Enzymatic Activity and Rheological and Sensory Properties of Strawberry Purees

The behavior of strawberry purees submitted to processes of mild pasteurization (75 °C — 15 s) and severe pasteurization (90 °C — 20 s), using as references fresh and hot-filled purees, was studied. Purees thermally treated were stored at +3 °C during 2 months. Pectin methylesterase activity, rheological behavior, and taste quality were analyzed. The results showed how the pectin methylesterase activity of strawberry puree (0.385nanokatal/mL) was reduced to 25.5% by the mild heat treatment, to 5.4% by the severe one and to undetectable levels in the hot-filled puree. A significant increase in the viscosity was detected as a consequence of the severe thermal treatments, although in any case it decreased with storage time. Taste quality, evaluated by simple ranking tests of samples, was superior in the fresh puree, without significant differences among the three samples thermally treated. The assessors pointed out the greater aromatic intensity of the fresh puree and the lack of cooked flavors in all sample...