# Simultaneously Monitoring and Reducing Nε-Carboxymethyl-Lysine and 5-Hydroxymethylfurfural Contents During Soy Sauce Production and Consumption

## TL;DR

This study identifies harmful compounds in soy sauce and proposes methods to reduce them during production and consumption.

## Contribution

The study introduces practical methods to simultaneously reduce CML and 5-HMF in soy sauce.

## Key findings

- CML and 5-HMF primarily come from raw materials, fermentation reactions, and additives in soy sauce production.
- Thermal treatment increases CML and 5-HMF contents in soy sauce.
- Adding (−)-epicatechin and ascorbic acid can reduce these harmful compounds.

## Abstract

Soy sauce (SS) is one of the most popular condiments in the world. However, Nε-carboxymethyl-lysine (CML) and 5-hydroxymethylfurfural (5-HMF), harmful Maillard reaction products, are present in SS. Worse still, their primary sources in SS production remain unclear, and their contents increase during the consumption of heated SS. In this study, CML and 5-HMF were simultaneously monitored, and thermal treatment and the addition of natural product were used to simultaneously reduce their contents during SS production and consumption. During SS production, CML and 5-HMF primarily originated from the raw materials used in SS production, Maillard reactions during fermentation, and the addition of food additives. Also, CML and 5-HMF were simultaneously found in commercial light soy sauce, dark soy sauce, and infant SS, and thermal treatment could increase their contents. Fortunately, additional thermal treatment of semi-finished SS (especially raw sauce and rude light SS) and appropriate concentrations of (−)-epicatechin (100 μM) and ascorbic acid (5 μM), respectively, added to SS for direct and heated consumption, could simultaneously reduce the CML and 5-HMF contents. This study highlights the presence of CML and 5-HMF in SS and proposes practical methods to simultaneously minimize their contents during production and consumption.