Walk into any spirits shop in Korea and Makegeolli is likely to be the beverage that many would point you to as indicative of the country’s heritage in alcoholic products. It is a yeasty fermented brew made from koji or nuruk, cooked rice and flour. The alcohol content is 6 or 7% which is marginally more than a high alcohol cider but contains various sugars, vitamins, the organic acids and interesting bioactives which are derived from the yeast and the substrates they grow on.

Makegeolli relies on its live yeast population for the special flavour qualities but this reduces its shelf-life to just over 1 week. Even though methods to extend shelf-life have been explored, they have proved to have changed the flavour too much, been too expensive or not really appropriate. One group of Korean researchers found grapefruit seed extract had antimicrobial activity against both yeasts and pathogens (Choi et al., 2014). They only needed a range of 0.1%  to 0.2%  of the grapeseed extract to create an impact on shelf-life without compromising the sensory characteristics of the Makegeolli and spoiling its quality. The extract extended the shelf-life by an extra week which is significant with this product. The seed extract is clearly an interesting natural preservative and deserves further attention.

Reference

Choi, J.-S., Lee, Y.-R., Ha, Y.-M., Seo, H. J., Kim, Y. H., Park, S.-M. and Sohn, J. H. (2014), Antibacterial Effect of Grapefruit Seed Extract (GSE) on Makgeolli-Brewing Microorganisms and Its Application in the Preservation of Fresh Makgeolli. J. Food Sci. 79 M1159–M1167. doi: 10.1111/1750-3841.12469