Method performance study for total solids and total fat in coconut milk and products

Abstract

Many analytical methods are available for total solids and total fat in various kinds of food. However, none is specific for coconut milk and products. The aim of this study was to establish methods and to conduct the method performance study on determination of total solids and total fat in coconut milk and products. In the single laboratory study, three methods for total solids determination were conducted: drying in hot air oven at 102±2°C and at 130±3°C and drying in vacuum oven at 70°C, 70mmHg, as well as three methods for total fat determination: direct extraction method, acid hydrolysis method and alkaline hydrolysis method. Sixteen samples of aqueous coconut milk and coconut milk powder were selected as test materials. Total solids and total fat contents were analyzed in 10 individual samples of each test material (N=10). The statistical analysis (one-way ANOVA) showed no significant difference for total solids and no difference for total fat content by the used methods (p>0.05). Since the drying method by hot air oven at 102±2°C is the most commonly used for total solids in food laboratories, it was selected for further inter-laboratory study. For total fat determination, the alkaline hydrolysis method (Roese–Gottlieb) was selected for further inter-laboratory study since it is less time-consuming and involves fewer steps than the acid hydrolysis method. Seventeen laboratories participated in the inter-laboratory study and seven representative test materials with varying levels of total solids and fat were used. The method performance characteristics are presented. These methods were proposed to CODEX and endorsed as the CODEX standard methods (type I) for aqueous coconut milk and coconut cream analyses.