Abstract: Glycine, as a non-essential amino acid in the human body, has the simplest structure among amino acid series. Glycine is widely used as a food additive with the maximum level of 1.0 g/kg in the food industry. Recent years, industrial grade glycine is illegally used in food products to substitute milk or improve protein content. In this paper, an HPLC method was established for the determination of glycine and compared with the amino acid analyzer method. Meanwhile, glycine contents in commercial milk, milk drink and plant protein products were determined by the HPLC method and the amino acid analyzer method. The results indicated that the amino acid analyzer method had advantages of stable and accurate results, low detection limit and simple operation procedures, while the HPLC method had the advantages of time saving and enough low detection limit compared with the routine fluorescence detection. Therefore, both methods can be applied for practical determination of glycine in food products as mutual authentication methods.

Key words: glycine, HPLC, amino acid analysis