Quantitative estimation of β-glutamylethylamide in commercially available made teas [<italic>Camellia sinensis</italic> (L.) O. Kuntze, Theaceae] in Kenya

Abstract

A study was carried out to quantitatively estimate the L-theanine content in 19 teas commercially available in the Kenyan market by High Performance Liquid Chromatography (HPLC). The test tea samples analyzed were green (&lt;italic&gt;n&lt;/italic&gt; = 4), black (&lt;italic&gt;n&lt;/italic&gt; = 8) and flavored (&lt;italic&gt;n&lt;/italic&gt; = 7) teas from different origins viz., Kenya (&lt;italic&gt;n&lt;/italic&gt; = 4), Uganda (&lt;italic&gt;n&lt;/italic&gt; = 2), Tanzania (&lt;italic&gt;n&lt;/italic&gt; = 5), Rwanda (&lt;italic&gt;n&lt;/italic&gt; = 4), Cameroon (&lt;italic&gt;n&lt;/italic&gt; = 1) and Sri-Lanka (&lt;italic&gt;n&lt;/italic&gt; = 2) commercially available in the Kenyan market. The estimated Limit of Detection (LOD) of the current method was 0.01 % L-theanine. The L-theanine content ranged from below the detection limit (&lt; 0.01 % L-theanine) to 1.60 % L-theanine on a dry weight (d.w) basis. Statistically significant differences (p &lt; 0.05) were observed in the L-theanine contents of black, green and flavoured teas. Rwandan green tea contained the highest L-theanine content with 1.60 % d.w. whereas six of the seven flavoured teas had very low theanine levels (&lt; 0.01 %) that could not be quantified by the current method.