Treating Purees

March 25/Journal of Technology & Science -- According to a study from Valencia, Spain, "The behavior of strawberry purees submitted to processes of mild pasteurization (75 degrees C - 15s) and severe pasteurization (90 degrees C - 20s), using as references fresh and hot-filled purees, was studied. Purees thermally treated were stored at +3 degrees C during two months."

"Pectin methylesterase activity, rheological behavior, and taste quality were analyzed. The results showed how the pectin methylesterase activity of strawberry puree (0.385 nanokatal/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 samples. All treated samples maintained their sensory quality during two months of storage at 3 degrees C. The taste quality of hot-filled purees stored one or two months at room temperature (21 degrees C) was significantly lower than the respective chilled samples," wrote O. Osorio and colleagues.

The researchers concluded, "From this point of view, the hot-Filled treatment and chilling storage will be recommended for this product."

Osorio and colleagues published their study in Food Science and Technology International ("Effect of Thermal Treatment on Enzymatic Activity and Rheological and Sensory Properties of Strawberry Purees." Food Science and Technology International, 2008;14(Suppl. 5):103-108).

For more information, contact J.V. Carbonell, CSIC, Institute Agroquim & Tecnol Alimentos, POB 73, Valencia 46100, Spain.

From the March 30, 2009, Prepared Foods E-dition