2.11. Hydrolysis of orange peel
Orange (Citrus sinensis) processing residues (peel and attached membranes)
were thoroughly washed with double-distilled water and ground to 5mm particles.
Total dry matter content was determined by drying at 50 ◦C for 24 h. Orange
peelwas suspended in 250mL flasks to a concentration of 1% (w/v) with 50mMTris
buffer at pH 8.0, which was shown to be the optimal for pectin lyase activity, and
30gmL−1 chloramphenicol to avoid contamination. Hydrolysis using various concentrations
of enzyme was carried out at 50 ◦C for 48 h, with constant agitation at
200 rpm. Production of soluble reducing sugars was estimated by the DNS method
[21], using galacturonic acid as standard. Insoluble dry matter was determined by
vacuum filtering hydrolysate through a 10mOmnipore filter followed by washing
the filters with deionized water. Filters were dried to constant weight in an oven at
70 ◦C. The difference between insoluble dry matter on the filter from a control flask
without enzyme and insoluble drymatter on filters from flasks containing different
concentrations of enzyme was determined to be the dissolved dry matter.