IMPEDANCE MEASUREMENT OF GROWTH OF LACTIC-ACID BACTERIA IN DAIRY CULTURES WITH HONEY ADDITION

The effect of honey addition (0, 1, 3, 5 ol 10%, wt/vol) to skim milk on the growth of Lactobacillus acidophilus and a mesophilic starter culture (consisting of Lactococcus lactis, subsp. lactis, Lactococcus lactis, subsp, cremoris and Lactococcus lactis, subsp. lactis, biovar. diacetylactis) was investigated by monitoring impedance changes. The inhibitory effect of honey closes was evaluated from the course of impedance curves by determining the detection time (DT), the time of maximal difference in impedance change (IT) and the slope of the lineal part of the impedance curve (K). Lactobacillus acidophilus was sensitive to the honey concentrations over 5% regardless of the heat treatment of honey. The maximal inhibitory effect on the growth of the mesophilic starter was produced by unheated honey at 10%, wt/vol, while the addition of sterilized honey had only limited influence on this culture at any concentration studied.