Abstract:
Dehydrated organic fruits have gained high demand in the export market. The
objective of this study was to evaluate the effect of cabinet drying (CD) and
microwave assisted vacuum drying (MW-VD) techniques on the quality
attributes of osmotically pretreated pineapple. Fruit slices
(50±5mm×30±5mm×5±1mm) were blanched for three minutes before dipping
into the 50 °Brix sugar solution for four hours. Osmotically pretreated fruit slices
were placed into the driers at different time temperature combinations. Several
trials were carried out to both CD (50 °C/ 22 h, 65 °C/20 h, 60 °C/24 h) and MW VDA (40 °C /40min, 45 °C /20min, 40 °C / 50 min, 40 °C/ 1h). Physical
appearance, moisture content and water activity measurements were used to
select the optimum conditions of driers for drying process. Half set of
osmotically pretreated fruit slices were dried at 60 oC for 24 h using CD and
remaining set of fruit slices dehydrated at 40 oC for one hour using MW-VD.
Physicochemical analysis such as moisture content, titratable acidity, water
activity, total soluble solid, vitamin C, pH, porosity, rehydration ratio, color and
microbiological (Total Plate Count) analysis were carried out for dehydrated
pineapple slices. Pineapple slices dehydrated by MW-VD were significantly low
(p<0.05) in moisture content (2.34±0.10% - dry basis) and total plate count
(4.55±4.55 CFU/g), while high in acidity (3.54±0.35 mol/L), vitamin C
(0.04±0.0024%), porosity (51.30±2.25%), rehydration ratio (1.37±0.07) and
total color difference ΔE (26.63±4.53) than pineapple slices dehydrated by CD.
Other parameters of pineapple fruit slices dehydrated by two techniques did not
vary significantly (p>0.05). Results of this study proved that MW-VD technology
can be used to produce better quality dried fruit products of pineapple than that
of CD technology. Further studies are necessary to address the suitability of
commercial level/large scale production.
