Effect of the Drying Conditions in a Pulsed Fluidized Bed Dryer on the Sulforaphane Content of Broccoli [Efecto de Las Condiciones de Secado en Lecho Fluidizado Pulsante Sobre el Contenido de Sulforafano de Brócoli]

The effect of the drying conditions of sulforaphane-rich broccoli in a pulsed fluidized bed dryer, on the sulforaphane content and drying kinetics was studied, with the aim of identifying the operating conditions that minimize the loss of sulforaphane in the dehydrated product. A central composite design was used, in which drying air temperature and plate rotational speed were the variables considered. The drying curves were fitted to empirical models and it was found that Page s model showed the best fit (R2≥99%). The drying time decreased with the increase of drying air temperature and the increase of the plate rotational speed. The regression model predicted that 29°C and 108 rpm were the optimal conditions, resulting in a sulforaphane content equal to 1.5 μmol/g in dry basis, giving a value that is 1.36-fold the sulforaphane content in fresh broccoli. This value was experimentally confirmed.