Kinetics of almond skin separation as a function of blanching time and temperature

This study was undertaken to better characterize the process of almond seed coat (a.k.a. skin) separation via hot water submersion, a process often referred to as 'blanching'. The degree of skin separation on individual almonds was measured after varying treatment times and temperatures, and modeled empirically. At all tested temperatures (100-70 degrees C), separation progressed along a sigmoidal logistic curve. Applying the concepts of microbial lethality kinetics to seed coat separation, D-separation values were 24 s at 90 degrees C (194 degrees F), 118 s at 80 degrees C (176 degrees F), and 443 s at 70 degrees C (158 degrees F). From these, the Z(separation) value between 70 degrees C and 90 degrees C was 15.85 degrees C. The skin separation rate decreased quickly below 90 degrees C (194 degrees F). By comparing the rate of seed coat separation, almond varieties, as well as growing, harvesting, and processing conditions could be quantitatively evaluated for their impact on skin separation. (C) 2014 Elsevier Ltd. All rights reserved.