Nutritional Analysis and Stability Studies of Some Natural and Synthetic Food Colourants

摘要

The pH, titratable acidities, proximate and mineral compositions of two natural colourants and three synthetic colourants were determined. The pH and titratable acidity were determined over a period of 14 days at 24 h intervals. The natural colourants were the calyxes of Hibiscus sabdariffa (SL) and the stem of Sorghum bicolour (KD), while the synthetic colourants were Egg Yellow (EY), Chocolate Brown (CB) and Dark Orange (DO). The pH of all samples increased as the number of days increased. The pH of SL was considerable lower than that of other colourants in this study (from 1.6 on day 1 to 2.7 on day 14) thus suggesting high acidity while the other colourants had basic pH (5.6-6.2 on day 1 to 7.4-8.4 on day 14). The natural colourants had higher moisture, lipid, carbohydrate and fibre contents while the synthetic colourants were very high in ash content. The protein contents of the colourants were fairly uniform irrespective of their sources. The synthetic colourants were particularly high in K and Mg while the natural colourants were rich in Ca.