GROWTH MODULATING PROPERTIES OF POLYPHENOLIC APPLE POMACE EXTRACT ON FOOD ASSOCIATED MICROORGANISMS

Abstract

Bacteriostatic effects of plant derived polyphenols are generally proposed for food protection against microbial spoiling. This study aimed at characterizing distinct growth modification and cell-lytic properties of an apple pomace extract (APE) containing short-chain and long-chain PP on food spoiling and fermenting starter bacteria.
APE contained 6.76 wt % PP, 0.46 wt % glucose, 1.69 wt % fructose, 1.26 wt % starch, 3.8 wt % sorbitol, and 0.64 wt % nitrogen with a pH-value of 4.1. APE caused growth modification of prominent bacterial food spoilers, yeasts, moulds and food fermenting starter bacteria was analyzed turbidometry (180° light absorption measurement at 600 nm wavelength). Cell-lytic activity of APE was measured by a SYTOX® Green fluorescence cell viability assay.
APE 1.5 w/w % reduced the growth of gram-positive and gram-negative food spoiling bacteria in dose-dependent manner up to 35.00%. Bacillus subtilis growth was reduced up to 10.53% comparable to 1.01 µg/ mL ampicillin or 0.144 mg/ mL sulfamethoxazol. In contrast, the growth of several fermenting starter bacteria increased at 1.5 w/w % APE up to 167.65% whereas expansion of yeasts and moulds were unaffected.
Neither specific cell-lytic activities of APE could be examined on gram-positive and gram-negative food spoiler nor food fermenting starter bacteria.
This study indicates that APE is a bacteriostatic but not a cell-lytic agent against food spoiling bacteria. Instead, the growth of specific lactic acid bacteria was supported by APE. Therefore, APE might stabilize explicit food fermentation processes.