Pomon Benjamin, Zhao Yu, Lai Alex L, Lin Tiantian, Freed Jack H, Abbaspourrad Alireza
Department of Food Science, College of Agriculture and Life sciences, Cornell University, Stocking Hall, Ithaca, NY, 14853.
Department of Chemistry, College of Arts and Sciences, Cornell University, Ithaca, NY 14853.
Food Hydrocoll. 2023 May;139. doi: 10.1016/j.foodhyd.2023.108544. Epub 2023 Feb 1.
Thaumatin, a potent sweet tasting protein extracted from the Katemfe Plant, is emerging as a natural alternative to synthetic non-nutritive sweeteners and flavor enhancer. As a food additive, its stability within the food matrix during thermal processing is of great interest to the food industry. When heated under neutral or basic conditions, thaumatin was found to lose its sweetness due to protein aggregation caused by sulfhydryl catalyzed disulfide bond interchange. At lower pH, while thaumatin was also found to lose sweetness after heating, it does so at a slower rate and shows more resistance to sweetness loss. SDS-PAGE indicated that thaumatin fragmented into multiple smaller pieces under heating in acidic pH. Using BEMPO-3, a lipophilic spin trap, we were able to detect the presence of a free-radical within the hydrophobic region of the protein during heating. Protein carbonyl content, a byproduct of protein oxidation, also increased upon heating, providing additional evidence for protein cleavage by a radical pathway. Hexyl gallate successfully inhibited the radical generation as well as protein carbonyl formation of thaumatin during heating.
索马甜是一种从非洲竹芋植物中提取的强效甜味蛋白，正逐渐成为合成非营养性甜味剂和风味增强剂的天然替代品。作为一种食品添加剂，其在热加工过程中在食品基质中的稳定性是食品工业非常感兴趣的。在中性或碱性条件下加热时，发现索马甜由于巯基催化的二硫键互换导致蛋白质聚集而失去甜味。在较低的pH值下，虽然索马甜在加热后也会失去甜味，但失甜速度较慢，且对甜味损失的抵抗力更强。SDS-PAGE表明，在酸性pH值下加热时，索马甜会分解成多个较小的片段。使用亲脂性自旋捕获剂BEMPO-3，我们能够在加热过程中检测到蛋白质疏水区域内自由基的存在。蛋白质羰基含量是蛋白质氧化的副产物，加热时也会增加，为自由基途径导致的蛋白质裂解提供了额外证据。没食子酸己酯成功抑制了索马甜在加热过程中的自由基生成以及蛋白质羰基的形成。
