Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing
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 (insolub...
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| Format: | Article |
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MDPI AG
2023-10-01
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| Series: | Foods |
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| Online Access: | https://www.mdpi.com/2304-8158/12/20/3759 |
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| author | Pedro A. V. Freitas Laia Martín-Pérez Irene Gil-Guillén Chelo González-Martínez Amparo Chiralt |
| author_facet | Pedro A. V. Freitas Laia Martín-Pérez Irene Gil-Guillén Chelo González-Martínez Amparo Chiralt |
| author_sort | Pedro A. V. Freitas |
| collection | DOAJ |
| description | 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<sup>−1</sup> defatted almond skin (DAS)), with greater antioxidant potential (1.063 vs. 1.490 mg DAS.mg<sup>−1</sup> DPPH) and showed greater antibacterial effect (lower MIC values) against <i>L. innocua</i> (34 vs. 90 mg·mL<sup>−1</sup>) and <i>E. coli</i> (48 vs. 90 mg·mL<sup>−1</sup>) 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 (H<sub>2</sub>O<sub>2</sub>), 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% H<sub>2</sub>O<sub>2</sub>. 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. |
| first_indexed | 2024-03-10T21:15:19Z |
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| institution | Directory Open Access Journal |
| issn | 2304-8158 |
| language | English |
| last_indexed | 2024-03-10T21:15:19Z |
| publishDate | 2023-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Foods |
| spelling | doaj.art-1383a05107a1474c86d0e02b2381e9b62023-11-19T16:29:22ZengMDPI AGFoods2304-81582023-10-011220375910.3390/foods12203759Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial ProcessingPedro A. V. Freitas0Laia Martín-Pérez1Irene Gil-Guillén2Chelo González-Martínez3Amparo Chiralt4Institute of Food Engineering FoodUPV, Universitat Poltècnica de València, 46022 Valencia, SpainInstitute of Food Engineering FoodUPV, Universitat Poltècnica de València, 46022 Valencia, SpainInstitute of Food Engineering FoodUPV, Universitat Poltècnica de València, 46022 Valencia, SpainInstitute of Food Engineering FoodUPV, Universitat Poltècnica de València, 46022 Valencia, SpainInstitute of Food Engineering FoodUPV, Universitat Poltècnica de València, 46022 Valencia, SpainAlmond 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<sup>−1</sup> defatted almond skin (DAS)), with greater antioxidant potential (1.063 vs. 1.490 mg DAS.mg<sup>−1</sup> DPPH) and showed greater antibacterial effect (lower MIC values) against <i>L. innocua</i> (34 vs. 90 mg·mL<sup>−1</sup>) and <i>E. coli</i> (48 vs. 90 mg·mL<sup>−1</sup>) 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 (H<sub>2</sub>O<sub>2</sub>), 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% H<sub>2</sub>O<sub>2</sub>. 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.https://www.mdpi.com/2304-8158/12/20/3759phenolic compoundscellulose fibresintegral fractionationactive compoundsbleaching optimisationbioactive properties |
| spellingShingle | Pedro A. V. Freitas Laia Martín-Pérez Irene Gil-Guillén Chelo González-Martínez Amparo Chiralt Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing Foods phenolic compounds cellulose fibres integral fractionation active compounds bleaching optimisation bioactive properties |
| title | Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing |
| title_full | Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing |
| title_fullStr | Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing |
| title_full_unstemmed | Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing |
| title_short | Subcritical Water Extraction for Valorisation of Almond Skin from Almond Industrial Processing |
| title_sort | subcritical water extraction for valorisation of almond skin from almond industrial processing |
| topic | phenolic compounds cellulose fibres integral fractionation active compounds bleaching optimisation bioactive properties |
| url | https://www.mdpi.com/2304-8158/12/20/3759 |
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