Structural and functional properties of whey protein isolate–inulin conjugates prepared with ultrasound or wet heating method

• Published in: Journal of the science of food and agriculture 2024-09, Vol.104 (12), p.7281-7290
• Main Authors: Qin, Yu‐Qing, Fan, Yan‐Ge, Ren, Jing‐Nan, Wang, Liu‐Yan, Han, Nan‐Feng, Fan, Gang
• Format: Article
• Language: English
• Subjects: agriculture; Amino acids; antioxidant activity; Antioxidants; Antioxidants - chemistry; Banded structure; Chemical activity; Circular dichroism; circular dichroism spectroscopy; conjugate; Conjugates; Dichroism; Electrophoresis; emulsions; Emulsions - chemistry; fluorescence; Food industry; Fourier transforms; free amino acids; functional properties; Heat treatment; Heating; High temperature; Hot Temperature; Infrared spectroscopy; Inulin; isoelectric point; Maillard Reaction; Polyacrylamide; polyacrylamide gel electrophoresis; Polysaccharides; Protein structure; Proteins; Secondary structure; Sodium dodecyl sulfate; Sodium lauryl sulfate; Spectroscopy; Spectrum analysis; Structure-function relationships; Thermal stability; Ultrasonic imaging; Ultrasonic methods; Ultrasonic processing; Ultrasonic testing; ultrasonic treatment; ultrasonics; Ultrasound; wet heating; Whey; Whey protein; whey protein isolate; Whey Proteins - chemistry
• ISSN: 0022-5142; 1097-0010; 1097-0010
• DOI: 10.1002/jsfa.13549

BACKGROUND Whey protein isolate (WPI) generally represents poor functional properties such as thermal stability, emulsifying activity and antioxidant activity near its isoelectric point or high temperatures, which limit its application in the food industry. The preparation of WPI–polysaccharide covalent conjugates based on Maillard reaction is a promising method to improve the physical and chemical stability and functional properties of WPI. In this research, WPI–inulin conjugates were prepared through wet heating method and ultrasound method and their structural and functional properties were examined. RESULTS In conjugates, the free amino acid content was reduced, the high molecular bands were emerged at sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), new C–N bonds were formed in Fourier‐transform infrared (FTIR) spectroscopy, and fluorescence intensity was reduced compared with WPI. Furthermore, the result of circular dichroism (CD) spectroscopy also showed that the secondary structure of conjugates was changed. Conjugates with ultrasound treatment had better structural properties compared with those prepared by wet heating treatment. The functional properties such as thermal stability, emulsifying activity index (EAI), emulsion stability (ES) and antioxidant activity of conjugates with wet heating treatment were significantly improved compared with WPI. The EAI and ES of conjugates with ultrasound treatment were the highest, but the thermal stability and antioxidant activity were only close to that of the conjugates with wet heating treatment for 2 h. CONCLUSION This study revealed that WPI–inulin conjugates prepared with ultrasound or wet heating method not only changed the structural characteristics of WPI but also could promote its functional properties including thermal stability, EAI, ES and antioxidant activity. © 2024 Society of Chemical Industry.