Oxidative rancidity was measured by estimating
thiobarbituric acid reactive substances (TBARS) by
the method of Alasnier, Meynier, Viau, and Gandmer
(2000). To 4 g of shrimp samples, 16 ml of trichloroacetic
acid (TCA) (5 g per 100 ml) was added, followed by
10 ml of butylated hydroxy toluene (BHT) in ethanol (1 g
per 100 ml). Samples were homogenized in a polytron
homogenizer and filtered through Whatman filter paper
(No. 4). Two milliliters of 0.02 mol/l thiobarbituric acid
(TBA) was added to 2ml of the above filtrate and heated
in a boiling water-bath for 30 min. The samples were
cooled and the pink colored complex with absorption
maxima at 532nm was measured. The intensity of the
colored complex is a measure of the malonaldehyde
concentration. The TBARS content was expressed as
mg malonaldehyde per kg of sample.