Effect of carrot extract (CE) on the bactericidal activity of a bovine lactoperoxidase system (LPOS) was
evaluated using Salmonella enteritidis (106 cfu/ml). LPOS antimicrobial activity increased from 1.4 to
3.8 log units by addition of 20-fold diluted CE. b-Carotene, a major pigment of carrot, also induced the
increase in the activity, indicating that b-carotene is one of the major enhancers of LPOS antimicrobial
activity. Discolouration of b-carotene was observed by the co-localisation of LPOS with b-carotene. The
discolouration was mainly caused by the oxidation of b-carotene through hypothiocyanate ion (OSCN),
which is produced by LPOS. The storage test of LPOS in the presence of b-carotene indicated that oxidised
b-carotene leads to the sustainable OSCN generation through an oxidised b-carotene/SCN redox cycling
reaction. Concomitant use of LPOS and b-carotene or b-carotene-rich food components raises the possibility
of development of an effective disinfectant.