Wong Yue Ling, Boulos Samy, Nyström Laura
Institute of Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.
Front Nutr. 2025 Apr 25;12:1532087. doi: 10.3389/fnut.2025.1532087. eCollection 2025.
Olive pomace is a by-product of the olive oil industry rich in biophenols such as hydroxytyrosol, with potential to be valorized as a functional ingredient. To investigate the stability of hydroxytyrosol in neutral aqueous solutions, the oxidative transformation of 50 ppm hydroxytyrosol in real and simulated tap waters over 5 days was studied with UV/Vis spectroscopy and UPLC-MS/MS. Simulated tap water systems consisted of 241 mg/L NaHCO with or without 139 mg/L CaCl, and a pH range of 6.5-8.0. Hydroxytyrosol in real tap water was completely transformed to various oxidation products after 1 day, exhibiting a marked red color (λ = 490 nm). Similarly, the simulated tap water system with a chemical composition closest to that of real tap water was largely able to reproduce this behavior with 85% hydroxytyrosol oxidation. A number of hydroxytyrosol oxidation products were annotated, including the red chromophore 2-(2-hydroxyethyl)-5-hydroxy-benzoquinone, which was formed through hydroxytyrosol autoxidation in the presence of bicarbonate ions. The chromophore's formation without addition of transition metals, enzymes or HO is presented for the first time. The results have implications for the stability and color behavior of olive pomace-derived biophenols applied to neutral or mildly alkaline environments.
橄榄果渣是橄榄油工业的副产品，富含羟基酪醇等生物酚，有潜力作为功能性成分加以利用。为研究羟基酪醇在中性水溶液中的稳定性，采用紫外可见光谱法和超高效液相色谱-串联质谱法，对实际和模拟自来水中50 ppm羟基酪醇在5天内的氧化转化情况进行了研究。模拟自来水体系由241 mg/L NaHCO₃（含或不含139 mg/L CaCl₂）组成，pH范围为6.5 - 8.0。实际自来水中的羟基酪醇在1天后完全转化为各种氧化产物，呈现出明显的红色（λ = 490 nm）。同样，化学成分与实际自来水最接近的模拟自来水体系在很大程度上能够重现这种行为，羟基酪醇氧化率达85%。对多种羟基酪醇氧化产物进行了鉴定，包括红色发色团2-(2-羟乙基)-5-羟基苯醌，它是在碳酸氢根离子存在下通过羟基酪醇自氧化形成的。首次报道了在不添加过渡金属、酶或羟基自由基的情况下该发色团的形成。这些结果对应用于中性或弱碱性环境的橄榄果渣衍生生物酚的稳定性和颜色行为具有重要意义。
