Application of fungal chitosan for clarification of apple juice

Absidia glauca var. paradoaxa IFO 4007 was cultured in liquid medium at 24 °C with agitation speed 100 and 200 rpm. The harvested mycelia were treated with hot 2% sodium hydroxide to isolate the alkali-insoluble materials. The extraction of chitosan from the alkali-insoluble materials was carried out with 2% acetic acid at room temperature. The maximum chitosan extracted was 0.6 and 1.28 g/l at 100 and 200 rpm, respectively. The degree of deacetylation of the extracted chitosan was 86%. The viscosity of 0.1% chitosan in 0.5% acetic acid was 4.0 cP. The use of fungal chitosan as fining agents for apple juice was compared to commercial chitosan prepared from shrimp shells. The reaction temperatures were investigated at 30, 35, and 40 °C with chitosan concentration at 0.1, 0.5, 0.7, and 1.0 g/l. Sample with chitosan treatment at 0.7 g/l and 40 °C reached maximum clarity. The clarity and color changes of the apple juice correlated closely for both fungal and shrimp chitosan treatment. The fungal chitosan proved highly effective in reducing the apple juice turbidity and gave lighter juices than the sample treated with shrimp chitosan.