# Effect of Mollusca shell extracts on inhibition of kimchi over-acidification

## TL;DR

This study explores how oyster and snail shell extracts can be reused as natural calcium sources to reduce kimchi over-acidification and environmental waste.

## Contribution

The study demonstrates that mollusca shell extracts can serve as ionized calcium supplements to slow kimchi acidification.

## Key findings

- Oyster and snail shell extracts contain high levels of calcium compared to other minerals.
- Ionized calcium from the shell extracts is more stable under simulated digestion conditions than CaCO3.
- Shell extracts can delay kimchi acidification by neutralizing fermentation acids.

## Abstract

Mollusca species shell such as oyster shell (OS) and snail shell (SS), are discarded after taking the meat, and the discarded shell causes the environmental problems. Therefore, recycling shell waste could potentially eliminate the environmental problems. This study aimed to evaluate the potential of OS and SS as natural calcium resources. The minerals, calcium, magnesium, potassium, phosphorus and sodium were analyzed in OS and SS extracts. Among them, the calcium content was the highest: 36.87 (%) and 33.42 (%) in the OS and SS extracts, respectively. Further, the content of ionized bioavailable form of calcium in OS and SS was higher than that of CaCO3 under simulated gastrointestinal digestion conditions. Additionally, OS and SS were added to kimchi, and their inhibitory effect on kimchi acidification was evaluated by assessing pH, titratable acidity and microbial analysis. As the results indicated that the addition of OS and SS had little effect on inhibiting the growth of lactic acid bacteria. However, it was confirmed that calcium neutralizes the organic acids produced during fermentation. Overall, the results of this study provide preliminary information on the re-use of OS and SS extracts as ionized natural calcium supplements and fermentation retardants.

•Oyster and snail shell extracts contain the highest calcium in various minerals.•Ionized calcium from oyster and snail shell was more stable under simulated gastrointestinal conditions than CaCO3.•Ionized bioavailable form calcium was stable under simulated intestinal conditions.•Oyster and snail shell extracts had the effect of delaying acidification of kimchi.

Oyster and snail shell extracts contain the highest calcium in various minerals.

Ionized calcium from oyster and snail shell was more stable under simulated gastrointestinal conditions than CaCO3.

Ionized bioavailable form calcium was stable under simulated intestinal conditions.

Oyster and snail shell extracts had the effect of delaying acidification of kimchi.