Extraction of carotenoids from Citrus unshiu press cake by supercritical carbon dioxide

Carotenoids focused on beta-cryptoxanthin were extracted using supercritical carbon dioxide(SC-CO2) from Citrus unshiu press cake. Extraction conditions such as extraction temperature, extraction pressure, flow rate of carbon dioxide, extraction time, and type and concentration of cosolvent were investigated. Most of the carotenoids including beta-cryptoxanthin were remained in the press cake after expression of Citrus fruits. The residual percentages of beta-cryptoxanthin were 81.3% in ethanol dehydration, 42.1% in hot air drying, and 55.5% in freeze drying. At lower extraction pressure, the extraction yields of total carotenoids and beta-cryptoxanthin decreased, while they increased as the increase of the extraction temperature at higher pressure. The extraction pressure had more significant effect on the extraction yields than the extraction temperature. Increasing temperature maximized the effect of pressure. The flow rate of carbon dioxide played a minor role in the extraction yields. The extraction yields increased as the increase of the extraction time. The use of ethanol and isopropanol as the cosolvents to the SC-CO2 had greater effects, while tetrahydrofuran showed the greatest effect on the extraction yields. The extraction yields increased greatly with the increase of the concentration of ethanol as a cosolvent. At 60 and 31.0 MPa, the extraction yields of total carotenoids and beta-cryptoxanthin were 38.0% and 73.0%, respectively with the addition of 20% ethanol to the SC-CO2 which were 1.5 and 1.7 times higher than those of the control. Extraction pressure, extraction time and concentration of cosolvent were the most important factors in increasing the extraction yield of beta-cryptoxanthin.