189: Bacteriostatic Mechanisms of Spore-Forming Bacteria Inhibited by Sucrose Ester of Palmitic Acid in a Ready-to-Drink Beverage

Introduction

Sucrose ester of fatty acid (SEFA) is an emulsifier that has a wide range of functions such as emulsifying, solubilizing, dispersing etc. Among SEFAs, those with specific fatty acid chains and degrees of esterification (such as sucrose esters of palmitic acid; SEPAs) are known to specifically inhibit the growth of heat-resistant spore-forming bacteria. Our previous study using Clostridium perfringens spores revealed that SEPA does not affect dormant spores but inhibits their outgrowth rather than spore germination in nutrient broth. To examine applicability of SEPA to practical food processing, we analyzed the growth of spore forming bacteria (SFB), Moorella thermoacetica, in Ready-to-Drink (RTD) milk coffee.

Methods

Milk coffee (3.5% sugar, 23% raw milk, pH7.0, heat pasteurized at F0=30) containing SEPA “P-1670” (Mitsubishi Chemical Co.) prepared in our lab was used in this study. Moorella thermoacetica spores (103 spores/ml) were inoculated into the milk coffee in several small glass tubes (two to five replicates) and incubated at 55ºC for 30 days. Bacterial growth was assessed by the decrease of pH (pH difference between inoculated and non-inoculated milk coffee). After incubation, a glass tube was heated at 105ºC for 20 min and viable spore count (VSC) was determined using Modified Thioglycollate Agar (55ºC for 14 days).

Results

The pH of the bacteria-inoculated milk coffee decreased by 0.23-0.27 at day 30. In contrast, addition of SEPA at more than 600 ppm completely suppressed the decrease (0.01-0.00) at the same time point. The VSC of the bacteria-inoculated milk coffee containing 600 ppm SEPA was 1.7 x 103 spores/ml at starting point, but decreased to below detection limit in the one week sample.

Significance

The results indicate that SEPA inhibits the growth of SFB, not only in experimental conditions, but also in the practical food supply process. SEPA could be used to prevent food spoilage caused by SFB in cans and retortable pouches treated by these specific pasteurization procedures.

Authors: Satoshi Sekimoto, Keiko Naito, Masami Miyake, Tsutashi Matsuura