2.4. Coating of pineapple samples
Four application techniques were used for coating the pineapple
samples, method I, sample drying until aw = 0.75 and afterwards
dipping at atmospheric pressure in the film-forming solutions for
5 min, with the subsequent coating drying at room temperature;
method II, sample dipping at atmospheric pressure in the filmforming
solutions for 5 min before drying until aw = 0.75; method
III, sample dipping at atmospheric pressure in the film-forming
solutions two times (5 min and 5 min, respectively), before drying
until aw = 0.75; and method IV, sample dipping in the film-forming
solutions applying a vacuum impregnation operation before drying
until aw = 0.75. The vacuum impregnation operation consisted of
applying a vacuum pulse (50 mbar for 3 min) to the immersed
sample, afterwards restoring the atmospheric pressure while the
sample remains immersed for 2 min more. In all cases, the experiments
were carried out at 25 C and the ratio of the weight of coating
solution:sample was 20:1. As controls, uncoated pineapple
samples submitted to the same drying process and becoming from
the same fruit, were considered.