2. Materials and methods
2.1. Freeze-dried mango powder preparation
Ripe mangoes (cultivar ‘Nam Dok Mai’) were purchased from a
local market in Bangkok and were selected by homogeneity in size,
weight, and peel color. The total soluble solid content of mangoes
was determined to be in the range 16–20 Brix. The fruits were
peeled, cut into 1 cm cubes, and freeze-dried using a freeze dryer
(Freeze dryer Dura-Top/Dura Stop MP, Dura Dry MP, FTS Systems
™, Stone Ridge, NY, USA). The mango pieces were frozen at
35 C and held for 2 h to achieve ice crystallization and subsequently
dried at a shelf temperature of 40 C. Then, all samples
were stored in evacuated desiccators for 3 d, which contained silica
gel to remove residual water. After that, the samples were considered
to have ‘‘zero’’ water content (as adapted from Burin et al.,
2004). Subsequently, the freeze-dried mango pieces were packed
in aluminum foil in a partial vacuum and crushed into powder
using a mortar. The particle size of mango powder was determined
to be in the range of 200–27,000 lm2. Mango powder was used for
the following analyses.
2.2. Water sorption behavior of freeze-dried mangoes