Sensory and Objective Measurement of Sandiness in Dulce de Leche, a Typical Argentine Dairy Product

Abstract

Lactose crystallization in Dulce de Leche can produce a sandiness defect. The objective measurement and sensory evaluation of this defect were the thrusts of this study. The technique for the microscopic measurement of the number and size of crystals is described in detail. Sensory panel members found that lactose crystals added to Dulce de Leche produced a sandiness defect equivalent to added sand crystals. The latter are far easier to define by size so they were used for magnitude estimation, where the exponent of Steven's law was approximately 1. Based on this, seven-point a sensory scale for sandiness was developed using Dulce de Leche mixed with sand of crystal sizes varying between 0 and 1500 µm. A double entry table is presented whereby the sensory sandiness threshold can be read as a function of size and number of crystals. With crystal size below 6 µm sandiness is not detected, even if all lactose in Dulce de Leche is crystallized. Above this size, the detection threshold depends on number of crystals.