Tests were carried out in a Q-50 analyser
(TA Instruments, USA), on 5–10 mg samples which were heatedfrom 30 to 250 _C at 10 _C/min, in N2 atmosphere. The Kirby–Bauer test (Boyle et al., 1973) was used in order to determine the antimicrobial activity of the two biocides proposed (formic acid and oregano essential oil).