Avaliação do uso da radiação infravermelho na secagem em camada de espuma da polpa de jabuticaba (Plinia sp.)

Abstract

Jabuticaba is a fruit native to Brazil which is appreciated for its flavor, sweetness and slightly acidic taste. Fresh jabuticaba presents is highly perishable which implies a low shelf life. This way, drying is applied to reduce moisture, resulting in an increase in shelf life and enabling the off-season offer of periods of products derived from jabuticaba. The foam-mat drying (SCE) technique has been applied to various foods. In the present study, the SCE was proposed to dry jabuticaba pulp (PJ) in the form of foam by applying heated air (AQ), as one type of drying, and infrared radiation (IV) as another. The objective was to evaluate the drying kinetics of both drying processes, as well as the effects on the physical properties and on the total anthocyanins (Ant) content of the jabuticaba pulp powder (SJ) obtained. The parameters evaluated were temperature (T) (50; 60; and 70 °C), velocity (v) (0.5; 1.0; and 1.5 m s–1) for SCE AQ, and IV radiation power (90; 130; and 170 W) and air velocity (0.5; 1.0; and 1.5 m s–1) for SCE IV. The response surface methodology was used to evaluate the conditions in relation to drying time (ts), water activity (aw), Ant content and effective diffusivity (Def). Smaller ts were obtained using high temperatures and low velocities in the case of SCE AQ, and high powers of IV radiation and low velocities for SCE IV. Page's model was the best fit for both drying methods. The drying rate was higher for SCE IV compared to SCE AQ. There observed only the falling rate period for both drying methods. The simultaneous increase on T and v caused an increase in ts. The aw was reduced by raising T and lowering v. Elevating T favored the degradation of the anthocyanins content, while increasing T caused less degradation. Def was increased by raising T from 50 to 70 °C. For SCE IV, it was observed that increasing IV power caused a reduction in ts and favored the degradation of Ant content, while aw and Def increased. The increase of v led to an increase in ts, aw, which did not favor Ant degradation, but decreased Def. The overall desirability was 0,712 and 0,614 for SCE AQ and SCE IV, respectively. The SJ obtained by SCE AQ showed higher bulk density, tapped and total color difference (p  0.05) in relation to the SJ obtained by SCE IV which, in turn, showed higher particle density (p  0.05). Both drying methods conferred high porosity to the SJ, reasonable fluidity and cohesiveness, browning index above 90% and whiteness index approximately 21%.