IN VITRO STUDIES TO CONTROL THE GROWTH OF MICROORGANISMS OF SPOILAGE AND SAFETY CONCERN IN HIGH‐MOISTURE, HIGH‐pH BAKERY PRODUCTS

Abstract

ABSTRACT Initial agar plate studies were done to determine the effects of various levels (0 to 2,000 ppm) of potassium sorbate (KS) and sorbic hydroxamic acid (SHA) over a wide pH range (5 to 9) on the growth of microorganisms of spoilage and safety concern in high‐moisture, high‐pH bakery products. While growth of most microorganisms was inhibited for > 28 days on agar plates containing ∼1,000 ppm of KS at pH 5 and incubated at 30C, growth of all microorganisms occurred in plates at pH 7 and 9, regardless of the concentration of KS. SHA was equally effective at pH 5, however, it proved to be a more effective inhibitor against most microorganisms at higher pH (9). Subsequent agar plate studies were done with water‐ethanol (WE) and mastic oil‐ethanol (ME) emitters. While WE emitters failed to control the growth of all microorganisms under investigation, ME emitters controlled the growth of most microorganisms, with the exception of Listeria monocytogenes, for ∼12 to 28 days on agar plates packaged in high‐gas‐barrier Cryovac or metallized bags, respectively. Inhibition was not simply due to the levels of ethanol, which ranged from ∼1.2 to 2.8% v/v, but rather, the mastic volatiles in the package headspace. This study has demonstrated the potential of SHA and ME emitters to control the growth of several microorganisms of spoilage and safety concern in high‐moisture, high‐pH bakery products. However, the type of packaging material influenced the antimicrobial efficacy of this vapor‐phase inhibitor.