2.2. Freeze drying of whole fruit pulp
Powder obtained by freeze drying of fruit pulp was found to be very
hygroscopic and difficult to compact. To minimize this problem 10%
maltodextrin was added to fruit mash, mixed by homogenization at
10,000 rpm for 10 min before freeze drying. Suspension of both fruits
was then poured into a few rectangular plastic containers separately
and covered with lids. The contents in the rectangle containers were
frozen by storing in a freezer at −20 °C for two days. After freezing,
the samples were transferred to a vacuum freeze dryer (Ben Hay, United
Kingdom) and dried at −35 °C for 48 h at 0.25 MPa pressure. The
pitaya and guava powders were obtained by crushing the dried material
in the sealed plastic bags separately and stored in a refrigerator (4 °C)
until used in the experiments.