Effects of different extraction methods on the extraction yield, degradation of bixin and formation of harmful volatile compounds in the extracts from annatto seeds

Abstract

Annatto is one of the most common natural colorants used in the food industry. However, the degradation of bixin (principle colour component) during the manufacturing and storage of annatto leads to the formation of undesirable volatile compounds which are harmful to human health. The aim of this study was to reduce the amount of undesirable volatile compounds while remain a sufficient extraction yield of bixin in annatto extracts. Bixin from annatto seeds was extracted using soybean oil at 120°C, sodium hydroxide solution at 50°C and acetone with a Soxhlet extractor. The extraction yield and the degradation of bixin in annatto extracts during the extraction processes were investigated and the formation of harmful volatile compounds including toluene and m-xylene in the extracts was analysed using a gas chromatography (GC) system equipped with a flame ionization detector (FID). The extraction with acetone resulted in the highest bixin yield, followed by extraction with sodium hydroxide. Bixin extraction yield of the extraction with soybean oil was the lowest and decreased gradually after 40 mins of the extraction. Losses of bixin by the extractions with acetone and sodium hydroxide were low while the extraction with soybean oil caused significant degradation of bixin. All three methods produced negligible amounts of toluene. However, the concentration of m-xylene in the acetone extracts was very high and remained unchanged during the extraction while sodium hydroxide extract contained a low level of this compound. Thus, the extraction method using sodium hydroxide solution is recommended for recovering pigment from annatto seeds to minimize the risk of harmful volatile compounds in annatto products.