Antibacterial activity of a polyphenol-rich haskap (Lonicera caerulea L.) extract and tannic acid against Cronobacter spp.

Abstract

The antibacterial properties of methanolic haskap (Lonicera caerulea L.) berry extracts and tannic acid were examined against Cronobacter spp. with a view to determine their potential for the control of this human pathogen in powdered infant formula. The total phenolic content (TPC) and composition of methanolic extracts from three different cultivars were determined. Fruit from cultivar Indigo Gem had the highest TPC (3.67 +/- 0.28 g/100 g dw) and was found to contain polyphenolic compounds, including anthocyanins, hydroxycinnamic acids and flavonols, as well as citric, malic, quinic and oxalic acids. Haskap extracts and tannic acid showed bacteriostatic and bactericidal activity against all Cronobacter species tested. Supplementation of powdered infant formula reduced the thermal resistance of C. sakazakii during heating at 55 degrees C and inactivated the species in reconstituted product during storage. The D-values were reduced from 16.47 +/- 0.47 min to 0.94 +/- 0.04, 2.03 +/- 0.06, and 0.54 +/- 0.02 min for haskap extract, tannic acid, and haskap extract + tannic acid, respectively. Haskap berry extracts and tannic acid could improve the safety of powdered infant formula.