2.2.2. Microwave assisted extraction of native & alkali-treated
agar
Microwave-assisted extractions (MAE) were performed in a
Ethos 1 (Microwave Accelerated Reaction System for Extraction and
Digestion, Milestone, USA) configured with a 24 position carousel.
One-gram of dried sample (not treated or alkali-treated) was transferred
to a teflon extraction vessel containing 40 mL distilled water;
then the vessel was closed upon introduction of a fibre optic
probe to measure the temperature in the systems. The operational
parameters employed in the MAE apparatus were the following:
magnetron power 100%, ramp temperature time, 10 min. During
operation, both temperature and pressure were monitored in a single
vessel (control vessel). Three temperature programmes were
found to be the optimum for extractions: 140 ◦C for 15 min; 110 ◦C
for 20 min; and 100 ◦C for 10 min. After the extraction, the vessels
were opened still warm because of the agar gelling properties.
The mixture was filtered using paper filter under vacuum at 70 ◦C.
Agar gel was then worked as above described. The extractions were
repeated three times.