# Natural food-derived antimicrobials against beer spoilage microorganisms

## TL;DR

This study explores natural food extracts, particularly clove, as safe antimicrobial agents to control beer spoilage microorganisms.

## Contribution

The study identifies clove extract and its compounds (eugenol and gallic acid) as effective natural antimicrobials against beer spoilage microbes.

## Key findings

- Clove hot-water extract inhibited the growth of four beer spoilage microorganisms in vitro.
- Eugenol and gallic acid from clove caused membrane perturbation in spoilage microorganisms.
- The antimicrobial effects of eugenol and gallic acid were comparable to commercial preservatives like potassium sorbate and sodium benzoate.

## Abstract

The spoilage of beer significantly threatens the quality and safety of products in the beverage industry. Certain natural foods contain beneficial bioactive components that are considered to be safer than chemical additives. This study aimed to identify extracts of natural foods as potential alternatives to chemical preservatives for controlling beer spoilage microorganisms. Among the two extraction methods applied to 176 natural foods, the extracts of clove alone effectively inhibited the growth of representative beer spoilage microorganisms, specifically Levilactobacillus brevis, Sporolactobacillus vineae, Pectinatus frisingensis, and Saccharomyces cerevisiae var. diastaticus. High-performance liquid chromatography and half-maximal inhibitory concentration analysis revealed that gallic acid and eugenol in cloves were active compounds with antimicrobial properties in vitro that were of a similar order of magnitude to those of commercial preservatives (potassium sorbate and sodium benzoate) under the tested conditions. Scanning electron microscopy observations and a fluorescence leakage assay using 3,3′-dipropylthiadicarbocyanine iodide indicated morphological alterations and membrane perturbation in treated microorganisms, except for the limited effect of gallic acid on S. cerevisiae var. diastaticus. These findings provide insight into the potential role of natural food-derived antimicrobials in controlling beer spoilage microorganisms, pending further validation in real beverage systems.

Key pointsOne hundred seventy-six natural foods were screened to identify inhibitors of beer spoilage microorganisms.Clove hot-water extract inhibited the growth of all four tested beer spoilage microorganisms in vitro.Eugenol and gallic acid exhibited effects suggestive of membrane perturbation.

One hundred seventy-six natural foods were screened to identify inhibitors of beer spoilage microorganisms.

Clove hot-water extract inhibited the growth of all four tested beer spoilage microorganisms in vitro.

Eugenol and gallic acid exhibited effects suggestive of membrane perturbation.

The online version contains supplementary material available at 10.1007/s00253-026-13787-0.