Freitas Pedro A V, Martín-Pérez Laia, Gil-Guillén Irene, González-Martínez Chelo, Chiralt Amparo
Institute of Food Engineering FoodUPV, Universitat Poltècnica de València, 46022 Valencia, Spain.
Foods. 2023 Oct 13;12(20):3759. doi: 10.3390/foods12203759.
Almond skin (AS) is an agro-industrial residue from almond processing that has a high potential for valorisation. In this study, subcritical water extraction (SWE) was applied at two temperatures (160 and 180 °C) to obtain phenolic-rich extracts (water-soluble fraction) and cellulose fibres (insoluble fraction) from AS. The extraction conditions affected the composition and properties of both valorised fractions. The dry extracts obtained at 180 °C were richer in phenolics (161 vs. 101 mg GAE. g defatted almond skin (DAS)), with greater antioxidant potential (1.063 vs. 1.490 mg DAS.mg DPPH) and showed greater antibacterial effect (lower MIC values) against (34 vs. 90 mg·mL) and (48 vs. 90 mg·mL) than those obtained at 160 °C, despite the lower total solid yield (21 vs. 29%) obtained in the SWE process. The purification of cellulose from the SWE residues, using hydrogen peroxide (HO), revealed that AS is not a good source of cellulose material since the bleached fractions showed low yields (20-21%) and low cellulose purity (40-50%), even after four bleaching cycles (1 h) at pH 12 and 8% HO. Nevertheless, the application of a green, scalable, and toxic solvent-free SWE process was highly useful for obtaining AS bioactive extracts for different food, cosmetic, or pharmaceutical applications.
杏仁皮（AS）是杏仁加工过程中产生的一种农业工业废渣，具有很高的增值潜力。在本研究中，采用亚临界水萃取（SWE）在两个温度（160和180℃）下从杏仁皮中获得富含酚类的提取物（水溶性部分）和纤维素纤维（不溶性部分）。萃取条件影响了这两种增值部分的组成和性质。在180℃下获得的干提取物中酚类物质含量更高（161 vs. 101 mg GAE·g脱脂杏仁皮（DAS）），具有更高的抗氧化潜力（1.063 vs. 1.490 mg DAS·mg DPPH），并且对（34 vs. 90 mg·mL）和（48 vs. 90 mg·mL）的抗菌效果比在160℃下获得的提取物更好，尽管在SWE过程中获得的总固体产率较低（21 vs. 29%）。使用过氧化氢（HO）从SWE残渣中纯化纤维素表明，杏仁皮不是纤维素材料的良好来源，因为即使在pH 12和8% HO的条件下经过四个漂白循环（1小时）后，漂白部分的产率较低（20 - 21%）且纤维素纯度较低（40 - 50%）。然而，应用绿色、可扩展且无有毒溶剂的SWE工艺对于获得用于不同食品、化妆品或制药应用的杏仁皮生物活性提取物非常有用。
