HIGHLIGHTS:

In the drying curves of jambu leaves there is a period of constant rate.

Solubility and cohesiveness, free flow, and good wettability are characteristics that add value to the raw material.

The critical moisture content of jambu ranges from 1.17 to 4.18 kg kg^-1 solid.

ABSTRACT

The objective of this study was to describe the constant drying flux stage, as well as obtaining the critical moisture content during the convective drying of jambu leaf paste crushed under different conditions and characterizing the physical properties of the material after drying. Drying was carried out in an air circulation oven at a speed of 1.0 m s^-1 and temperatures of 60, 70 and 80 ºC and layer thicknesses of 0.005 and 0.01 m. To determine the constant rate stage, the mass fluxes and the drying rate were calculated. Segmented polynomials were used to estimate the critical moisture content. Under the analyzed conditions, a typical drying behavior was found, demonstrating the existence of a significant period of constant drying rate for the mass of ground jambu leaves. Critical moisture content as a function of thickness and temperature did not show a trend. The material showed favorable physical characteristics, such as high solubility and cohesiveness, free flow, and good wettability, characteristics that add value to the raw material and for the availability of a new product to the market in the condition of packaging.

Key words:
Acmella oleracea L.; convective drying; critical moisture content; drying rate