Improvement of functional properties of Chlorella-inulin conjugates via Maillard reaction

Functionalities of proteins for the formulation of protein-fortified products are crucial, impacting the use of protein from sustainable sources such as algae. Glycation (the initial step of the Maillard browning reaction) is a standout modification technique explored to improve the functions of the protein in the food matrices. In this study, Chlorella powder was conjugated with inulin using a wet glycation method. It is a quick, scalable and easy method for improving the functionality of food proteins. In this study, conjugation was performed for three different Chlorella to inulin molar ratios (S1:1, S3:1 and S5:1). The solution of each molar ratio was heated at 90°C for 30 min under alkaline state (9.0 pH). Characterisation was conducted employing OPA assay, browning intensity and FTIR spectroscopy techniques. The results suggested glycation achieved the highest for the Chlorella-inulin ratio of 1:1. Glycation extent influenced the solubility of this conjugate significantly (P < 0.05) under an acidic medium. Other functional properties including hydration, moisture uptake, oil-binding and emulsifying activity were also significantly (P < 0.05) enhanced compared to unmodified Chlorella powder. Chlorella conjugate with molar ratio 1:1 also displayed higher antioxidant properties suggesting glycation's role in improving Chlorella powder free radical scavenging capabilities (1.25-fold increase) and reducing power (2.24-fold increase). The total scavenging activity and total reducing power of S1:1 were 2.526 × 10−3 and 1.872 × 10−3 mg mL−1 mg−1(Trolox Eq.), respectively. The results provide an understanding of different functionalities for glycated conjugates promising utilisation in the food and beverage industry.

用于制备蛋白强化食品的蛋白质功能特性至关重要，其直接影响藻类等可持续来源蛋白的应用前景。糖基化反应（Glycation，即美拉德褐变反应的起始步骤）是目前用于改善食品基质中蛋白质功能特性的热门改性手段。本研究采用湿法糖基化法，将小球藻（Chlorella）粉末与菊粉进行共价结合，该方法具备快速、可规模化且操作简便的优势，可有效改善食品蛋白的功能特性。本研究设置了三种不同的小球藻与菊粉摩尔比（S1:1、S3:1及S5:1）开展结合反应，各摩尔比对应的反应溶液均在pH 9.0的碱性条件下，于90℃加热30分钟。研究采用邻苯二甲醛（OPA）法、褐变强度测定及傅里叶变换红外光谱（FTIR）技术对产物进行表征。结果显示，当小球藻与菊粉摩尔比为1:1时，糖基化反应程度最高。糖基化反应程度可显著影响该共轭物在酸性介质中的溶解度（P<0.05）。与未改性的小球藻粉末相比，该共轭物的其他功能特性，包括水合能力、吸湿能力、油脂结合能力及乳化活性，均得到显著提升（P<0.05）。摩尔比为1:1的小球藻-菊粉共轭物还表现出更优的抗氧化性能，表明糖基化反应可有效提升小球藻粉末的自由基清除能力（提升1.25倍）与还原能力（提升2.24倍）。S1:1组的总自由基清除活性与总还原力分别为2.526×10^-3与1.872×10^-3 mg·mL^-1·mg^-1（以Trolox当量计）。本研究结果阐明了糖基化共轭物的各项功能特性，为其在食品及饮料工业中的应用提供了理论支撑。