ASABE Technical Library - Abstract

Abstract. Custard is a semisolid dairy dessert, common in Europe and recently introduced in America. A consumer´s important issue of growing interest is the sector of lactose intolerant patients, who require foods without lactose in order to avoid gastro-intestinal illness. However, changes in formulation may affect the structure of the food, and in custards, a firm gel is expected. Thus, the objective of this study was to determine the rheological properties of lactose-free custards during storage at refrigeration conditions. Custard was formulated with lactose-free milk, 4.5% of corn starch, 6.5% of stevia as sweetener and vanilla. Also, a commercial formulation was analyzed. Three cooking times were studied: 7.5, 8 and 10 min. Custards were cooled and stored at 4ºC during 4 weeks. The torque of the different custards was measured at several velocities (rpm) with a viscometer Brookfield DV-I+, using the disc spindle #5. Shear rate and shear strain were calculated from velocity and torque using the Mitshka equations, and the rheograms were built. Custards exhibited a dilatant behavior. The absence of lactose affected the rheological behavior, with low viscosity in lactose-free custards (p<0.05). Cooking time also had effect on the rheology of the dairy dessert (p<0.05), a cooking time of 8 min resulted in properties closer to the commercial formulation. Addition of a hydrocolloid is recommended in order to get better properties in lactose-free custards and to avoid syneresis during storage.