Supercritical Carbon Dioxide Extraction Of Citrus Peel Residue And Its Potential Utilization Value Of D-limonene

Citrus peel residue is a by-product of citrus fruit processing in Rutaceae.There are more than 10 million tons of citrus peel residue in China every year,but the comprehensive utilization rate is not high,which leads to serious environmental pollution and resource waste.The main utilization ways of citrus peel residue are bioactive ingredient extraction,feed production,egradable packaging materials and so on.Citrus peel residue is rich in d-limonene,flavonoids,carotenoids,limonoids and other bioactive substances.Among them,d-limonene has been widely concerned because it has expectorant,anti-tussive,anti-bacterial,anti-tumor,anti-oxidant,anti-inflammatory,anti-fatigue.The common extraction methods are distillation and organic solvent extraction.There are problems such as low extraction rate,low purity,toxic reagent residues and so on.Supercritical CO₂ extraction is a kind of natural green extraction method with good separation effect,high purity and non-toxicity.At present,researchs on citrus bioactive substances extracted by supercritical CO₂ at home and abroad mostly focus on citrus flavonoids and remain in the substance extraction stage,and the resulting extracts have not been further developed and utilized.Therefore,the study of supercritical CO₂extraction and d-limonene potential utilization value of citrus peel residue was a promising direction of citrus resource utilization,aiming to propose and develop a new industrialized way to promote the deep comprehensive utilization of citrus peel residue.In this study,the citrus peel residue after juice extraction was used as the material.The essential oil of citrus peel residue was obtained by supercritical CO₂ extraction,ultrasonic-assisted steam distillation extraction and ultrasonic-assisted organic solvent extraction.The extraction efficiency and d-limonene extraction were compared by these three methods.The supercritical CO₂ extraction of supercritical citrus peel oil was used to enrich d-limonene by molecular distillation.The supercritical citrus peel oil was added to the skin care emulsion to determine the physical and chemical properties,moisture retention,antioxidant and bacteriostatic properties of the emulsion.The main results are as follows:?1?Optimization of extraction technology of essential oil from citrus peel residue.The best extraction process of supercritical CO₂ extraction:extraction pressure 25 MPa,extraction temperature 35?,extraction time 150 min.Ultrasonic-assisted steam distillation extraction method:ultrasonic power 350 W,material liquid ratio 1:12 g/ml,ultrasonic time 60 min,distillation time 150 min.Ultrasonic-assisted organic solvent extraction:90%ethanol,1:14 g/ml material liquid ratio,400 W ultrasonic power,25min ultrasonic time.?2?Comparison of extraction efficiency and d-limonene content of three extraction methods of citrus peel residue essential oil.Extraction rate:ultrasonic-assisted organic solvent extraction?4.63%?>supercritical CO₂ extraction?2.21%?>ultrasonic-assisted steam distillation extraction?0.79%?;the relative content of d-limonene in the essential oil of citrus peel residue obtained by three different extraction methods:supercritical CO₂ extraction?57.89±0.73%?>ultrasonic-assisted organic solvent extraction?1.36±0.05?%ultrasonic-assisted steam distillation?0.43±0.13%?.?3?D-limonene in essential oil of supercritical citrus peel residue was enriched by molecular distillation.The optimum process conditions were vacuum degree 100 Pa,distillation temperature 55?,membrane scraping speed 300 r/min,feed flow rate 5.0ml/min,d-limonene yield 8.53%,relative content of d-limonene in essential oil after molecular distillation was 76.17±0.63%,the enrichment effect was obvious.?4?Functional determination of supercritical citrus peels essential oil skin care emulsion.The emulsion had good physical stability and was easy for skin to absorb,;and could keep skin moisture content at 45%⁴7%within 3 hours;the comprehensive antioxidant capacity increased with the increase of supercritical citrus peel oil content in skin care emulsion,and a relative content of 2%supercritical citrus dregs essential oils skincare emulsion could significantly inhibit the growth of Penicillium and Escherichia coli.