Thermal degradation of thaumatin at low pH and its prevention using alkyl gallates

• Published in: Food hydrocolloids 2023-05, Vol.139, p.108544, Article 108544
• Main Authors: Pomon, Benjamin, Zhao, Yu, Lai, Alex L., Lin, Tiantian, Freed, Jack H., Abbaspourrad, Alireza
• Format: Article
• Language: English
• Subjects: Antioxidants; BEMPO-3; EPR; Radical organic species; Spin probes; Thaumatin
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2023.108544

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. [Display omitted] •A lipophilic spin trap detected a free-radical upon heating of thaumatin at pH 2.0•Thaumatin solution can oxidize C11-BODIPY dye.•Alkyl gallates inhibits the protein the production of carbonyl species.•Free radicals generated heating were inhibited by alkyl gallates.