The effect of low temperature blanching on the texture of whole processed new potatoes

Improving the textural quality of whole new potatoes with respect to firmness was investigated through the application of low temperature blanching at 60, 65, 70, 75, 80, 90 and 100 degrees C for times up to 1 h. Rate of firmness degradation upon blanching, as measured using a 7 mm diameter probe attached to an Instron (4464) Universal Testing Machine, was significantly lower at 60-75 degrees C than at 80-100 degrees C over the investigated blanching times (P < 0.05). The activity of pectin methyl esterase (PME) was determined for whole new potatoes with an optimum activity of 2.92 mu mol/min/g at 65 degrees C for 15 min. The enzyme was rapidly inactivated after 15 min at 75 degrees C and after 5 min at both 80 and 90 degrees C. Processing was by immersion in a thermostatically controlled water bath at 90 or 100 degrees C for times up to 25 min and with and without blanching at 65 degrees C or 75 degrees C for 15 min. Shear force as an indicator of firmness was measured by shearing through the whole potato with a single blade (I min thickness) at a cross-head speed of 50 mm/min. Firmness was significantly higher (P < 0.05) for processed potatoes blanched at 65 degrees C than those cooked at 95 or 100 degrees C without blanching. Low temperature blanching offers the potential for improving texture of processed whole new potatoes. (c) 2005 Published by Elsevier Ltd.