Enhancement of antimicrobial activity of a lactoperoxidase system by carrot extract and β-carotene

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. β-Carotene, a major pigment of carrot, also induced the increase in the activity, indicating that β-carotene is one of the major enhancers of LPOS antimicrobial activity. Discolouration of β-carotene was observed by the co-localisation of LPOS with β-carotene. The discolouration was mainly caused by the oxidation of β-carotene through hypothiocyanate ion (OSCN−), which is produced by LPOS. The storage test of LPOS in the presence of β-carotene indicated that oxidised β-carotene leads to the sustainable OSCN− generation through an oxidised β-carotene/SCN− redox cycling reaction. Concomitant use of LPOS and β-carotene or β-carotene-rich food components raises the possibility of development of an effective disinfectant.