The moisture content of fresh A. nodosum was 2.83 ±0.07 kg water/kg dry matter.
Distilled water was selected as the medium for transferring ultrasound energy to A. nodosum.
A significant change was observed in the weight of the seaweed after ultrasonic pre treatment.
For example at the lowest ultrasound intensity (7.00W cm2) a gain of 19.63% in weight gain was observed whereas for 35.61 and 75.78 W cm2 pre-treatments weight gains of 9.80% and 0.84%, respectively were observed (Fig. 2).
The observed change was mainly due to moisture uptake from transferring medium i.e.
distilled water. Similarly in previous studies moisture gains of 12% and 8% were observed for Malay apple [14]and melon after ultrasound pre treatment priortodrying.
Fig. 3 shows solids loss as a function of the ultrasound pre-treatment intensity.
The loss of solids from seaweed to water increased at higher power levels. Maximum solid losses observed at 75.78W cm2 were 5.01%, whereas at the lowest power level (7.00W cm2) solid losses were 1.11%. It was observed that solid losses were significantly (P < 0.05) higher compared to control at all power levels investigated. Oliveira et al. also observed higher solid losses for ultrasound treated samples compared to control samples during ultrasound assisted drying of Malay apple.
Ultrasound enhanced the mass transfer of solids from A. nodosum.
The concentration gradient of soluble solids between the seaweed and the liquid resulted in water gain after the pre treatment