Chitosan of low molecular weight (MW; 340) in powder form from crab shells was purchased from Aldrich Company (Athens, Greece). Moisture content was less than 10% and chitosan had a deacetylation degree of 75–85%. A stock solution of chitosan was prepared by dissolving 1.5 g in 100 ml of 1% (w/v) glacial acetic acid and stirred overnight at room temperature (final chitosan concentration = 1.5% w/v). Pure rosemary oil (Kokkinakis S.A., Athens, Greece) was used (see below). The oil consisted of (major components): α-pinene: 46.1%; 1,8-cineole: 11.1%; camphene: 9.6%; camphor: 5.3%; sabinene: 4.6%; myrcene: 3.9%; borneol: 3.4%; bornyl acetates: 2.8%; verbenone: 2.3%; and linalool: 2.1%.