在这项工作中,使用微波辅助工艺优化了从柠檬皮废料中获得不同有价值的馏分的级联方法。首先使用带有 Clevenger 装置的微波辅助加氢蒸馏 (MAHD) 来获得柠檬精油 (LEO)。然后将剩余的残留物送入微波辅助提取 (MAE) 以提取柠檬色素 (LP)。使用 Box-Behnken 设计来评估 LP 萃取中乙醇浓度、温度和时间对萃取产量和颜色强度的影响。LP 的最佳提取条件为 80% (v/v) 乙醇、80 °C 和 50 min,液固比为 1:10。LEO 和 LP 的产量分别为 2 wt.% 和 6 wt.% 左右。采用气相色谱-火焰离子化检测 (GC-FID) 分析低离子体的组成,主要鉴定出柠檬烯 (65.082 wt.%) 、β-蒎烯 (14.517 wt.%) 和 γ-萜品烯 (9.743 wt.%)。使用不同的 Amberlite 吸附树脂 (XAD4、XAD7HP 和 XAD16N) 纯化 LP,显示 XAD16N 具有最佳吸附能力。超高效液相色谱-二极管阵列检测器-串联质谱(UPLC-DAD-MS)分析检测LP中主要成分的蓈虫素、地奥司明和橙皮苷富集因子分别为4.3、4.5和5.0,终浓度分别为4.728 wt.%、7.368 wt.%和2.658 wt.%。LEO 成功获得了对大肠杆菌和金黄色葡萄球菌的抗菌能力。 这项工作的结果表明,应用基于微波辅助过程的级联方法对柠檬废料进行价值化,获得天然色素和抗菌剂以应用于食品、化妆品和聚合物行业的潜力。
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Optimisation of Sequential Microwave-Assisted Extraction of Essential Oil and Pigment from Lemon Peels Waste
In this work, a cascade approach to obtain different valuable fractions from lemon peels waste was optimised using microwave-assisted processes. Microwave-assisted hydrodistillation (MAHD) with a Clevenger apparatus was firstly used to obtain the lemon essential oil (LEO). The remaining residue was then submitted to microwave-assisted extraction (MAE) to extract the lemon pigment (LP). A Box–Behnken design was used to evaluate the influence of ethanol concentration, temperature and time in LP extraction in terms of extraction yield and colour intensity. Optimal extraction conditions for LP were 80% (v/v) ethanol, 80 °C and 50 min, with a liquid-to-solid ratio of 1:10. The obtained yields for LEO and LP were around 2 wt.% and 6 wt.%, respectively. The composition of LEO was analysed by gas chromatography with flame ionisation detection (GC-FID), and limonene (65.082 wt.%), β-pinene (14.517 wt.%) and γ-terpinene (9.743 wt.%) were mainly identified. LP was purified by using different Amberlite adsorption resins (XAD4, XAD7HP and XAD16N), showing XAD16N the best adsorption capacity. Enrichment factors of 4.3, 4.5 and 5.0 were found for eriocitrin, diosmin and hesperidin, respectively, which were detected as the main components in LP by ultra-high-performance liquid chromatography–diode array detector–tandem mass spectrometry (UPLC-DAD-MS) analysis, with final concentrations of 4.728 wt.%, 7.368 wt.% and 2.658 wt.%, respectively. Successful antimicrobial capacity against Escherichia coli and Staphylococcus aureus was obtained for LEO. The results from this work showed the potential of applying a cascading approach based on microwave-assisted processes to valorise lemon wastes, obtaining natural pigments and antimicrobials to be applied in food, cosmetic and polymer industries.