Jaradat Sarah, Amr Ayed, Hamadneh Imad, AlKhatib Hatim, Alqaraleh Salameh, Al-Omari Rima, Tarawneh Haneen
Department of Nutrition and Food Science, The University of Jordan, Amman 11941, Jordan.
Department of Chemistry, The University of Jordan, Amman 11941, Jordan.
Prev Nutr Food Sci. 2024 Dec 31;29(4):495-503. doi: 10.3746/pnf.2024.29.4.495.
Anthocyanins (ANCs) are water-soluble pigments with antioxidant properties, offering potential as alternatives to synthetic food colorants. However, their stability is compromised by factors such as pH, temperature, and light exposure. Previous research demonstrated improved pH stability in black grape ANCs through cobalt ion (Co) complexation. This study investigates the effects of Co complexation on the thermal and light stability of black grape ANCs extracted from pomace. These ANCs were purified, complexed with Co (ANC-Co), and diluted in a pH 4.5 buffer solution. Purified ANCs were also diluted in a pH 3.5 buffer solution. Both ANCs and ANC-Co were heated to 40°C, 60°C, and 80°C for 7 h to assess thermal stability. To evaluate light stability, ANCs and ANC-Co were stored separately under ultraviolet (UV) light and daylight for one week. Thermal stability results revealed that complexation could significantly (≤0.05) extend ANC half-life by more than threefold and reduce temperature sensitivity by approximately 50%. Thermal degradation of ANCs was endothermic, nonspontaneous, and more structured in the transition state, as indicated by thermodynamic parameters (activation enthalpy (ΔH)>0, free energy of inactivation (ΔG)>0, and activation entropy (ΔS)<0). Light stability tests revealed that complexation significantly (≤0.05) extended ANC half-life by over tenfold and twentyfold under UV and daylight exposure, respectively. Therefore, Co complexation represents an effective technique to enhance the thermal and light stability of grape ANCs, making them more suitable for use as food colorants.
花青素（ANCs）是具有抗氧化特性的水溶性色素，有望成为合成食用色素的替代品。然而，它们的稳定性会受到pH值、温度和光照等因素的影响。先前的研究表明，通过钴离子（Co）络合可提高黑葡萄花青素的pH稳定性。本研究调查了Co络合对从果渣中提取的黑葡萄花青素的热稳定性和光稳定性的影响。这些花青素经过纯化，与Co络合（ANC-Co），并在pH 4.5的缓冲溶液中稀释。纯化后的花青素也在pH 3.5的缓冲溶液中稀释。将花青素和ANC-Co都加热到40°C、60°C和80°C，持续7小时，以评估热稳定性。为了评估光稳定性，将花青素和ANC-Co分别在紫外光和日光下储存一周。热稳定性结果表明，络合可显著（≤0.05）将花青素的半衰期延长三倍以上，并将温度敏感性降低约50%。热力学参数（活化焓（ΔH）>0、失活自由能（ΔG）>0和活化熵（ΔS）<0）表明，花青素的热降解是吸热的、非自发的，且在过渡态时结构更有序。光稳定性测试表明，络合在紫外光和日光照射下分别将花青素的半衰期显著（≤0.05）延长了十倍以上和二十倍以上。因此，Co络合是一种提高葡萄花青素热稳定性和光稳定性的有效技术，使其更适合用作食用色素。
