Department of Agricultural Technology, Processing Technology of Plantation Product Study Program, Pontianak State Polytechnic, Pontianak, Indonesia.
Department of General Lecture, Petra Christian University, Surabaya, Indonesia.
J Food Sci. 2024 May;89(5):2761-2773. doi: 10.1111/1750-3841.17046. Epub 2024 Mar 29.
Betalain is a water-soluble pigment contained in Caryophyllales plants. It not only holds potential as a natural food colorant but also offers various health benefits, acting as an antioxidant. This study focused on analyzing the pH-dependent stability of encapsulated betalain pigments extracted from red beetroot (Beta vulgaris L.) using methods such as absorption spectroscopy, HPLC, and LC-MS. The major pigments identified were vulgaxanthin I, betanin, isobetanin, and neobetanin, alongside minor components, including three betaxanthin species and a degradation product known as betalamic acid. Spectrophotometric analyses revealed that above pH 8, the betalain peak at 435 nm decreased and red-shifted to a peak at 549 nm, a shift that could be reversed through neutral pH treatment. At pH 11, a new broad peak appeared at 410 nm and was identified as betalamic acid. To assess the pH-dependency of each betalain, the targeted betalains were separated and quantified through HPLC after incubation across a wide pH range of 2-11 and during storage. After 3 days of storage in highly alkaline conditions (pH 10-11), major betalains, with the exception of neobetanin, underwent significant degradation. Conversely, these pigments displayed relative stability in acidic conditions. In contrast, neobetanin showed vulnerability to acidic conditions but exhibited tolerance to alkaline pH levels of 10-11. The degradation product, betalamic acid, demonstrated a similar susceptibility to alkaline pH as betanins. In conclusion, the significant stability decrease under highly alkaline conditions results not only from the hydrolytic reaction of betalains but also from the degradation of betalamic acid itself. PRACTICAL APPLICATION: Encapsulation methods are used to enhance the stability of betalains against temperature variations; however, the effects of pH, especially when considering individual betalain species, are not well understood. Despite betalains exhibiting similar features and being suitable for a wide pH range from acid to alkaline conditions, they are significantly affected by alkaline pH levels exceeding 10, as well as by storage duration. This study demonstrated the application of encapsulation to pH-dependent stability, and the findings offer valuable insights and a fresh perspective on betalains as red biocolorants, extending their potential application to a wide range of pH-controlled food products.
甜菜红是石竹目植物中含有的一种水溶性色素。它不仅具有作为天然食用色素的潜力，还具有多种健康益处，作为一种抗氧化剂。本研究集中于分析用吸收光谱法、高效液相色谱法和液相色谱-质谱法等方法从红甜菜根（Beta vulgaris L.）中提取的包封甜菜红素色素的 pH 值依赖性稳定性。鉴定出的主要色素为 vulgaxanthin I、betanin、isobetanin 和 neobetanin，以及三种甜菜黄质和一种已知为 betalamic acid 的降解产物等次要成分。分光光度分析表明，在 pH 值高于 8 时，435nm 处的甜菜红素峰减少并红移至 549nm 处的峰，通过中性 pH 值处理可逆转这种红移。在 pH 值 11 时，在 410nm 处出现一个新的宽峰，被鉴定为 betalamic acid。为了评估每种甜菜红素的 pH 值依赖性，在 2-11 的宽 pH 范围内孵育并在储存期间，通过高效液相色谱法分离和定量目标甜菜红素。在高度碱性条件（pH 10-11）下储存 3 天后，除了 neobetanin 之外，主要的甜菜红素经历了显著的降解。相反，这些色素在酸性条件下相对稳定。相比之下，neobetanin 对酸性条件敏感，但对碱性 pH 值 10-11 耐受。降解产物 betalamic acid 对碱性 pH 值的敏感性与 betanins 相似。总之，在高碱性条件下显著的稳定性降低不仅源于甜菜红素的水解反应，还源于 betalamic acid 本身的降解。实际应用：使用封装方法来提高甜菜红素对温度变化的稳定性；然而，pH 值的影响，特别是考虑到个别甜菜红素种类时，并不为人所熟知。尽管甜菜红素具有相似的特征，并且适合从酸性到碱性的宽 pH 值范围，但它们受到 pH 值超过 10 的碱性条件以及储存时间的显著影响。本研究证明了封装在 pH 值依赖性稳定性中的应用，并为甜菜红素作为红色生物色素提供了有价值的见解和新视角，将其潜在应用扩展到广泛的 pH 控制食品产品中。
