Abstract
Effect of ultrasound treatment on the physicochemical properties and structure of β‐lactoglobulin were investigated. β‐Lactoglobulin was treated with ultrasound at different amplitudes, temperatures, and durations. The surface hydrophobicity and free sulfhydryl group of β‐lactoglobulin were significantly increased after ultrasound treatment (p < .05). The maximal surface hydrophobicity and free sulfhydryl group were 5,812.08 and 5.97 μmol/g, respectively. Ultrasound treatment changed the physicochemical properties of β‐lactoglobulin including particle size (from 1.21 ± 0.05 nm to 1.66 ± 0.03 nm), absolute zeta potential (from 15.47 ± 1.60 mV to 27.63 ± 3.30 mV), and solubility (from 84.66% to 95.17%). Ultrasound treatment increased α‐helix and β‐sheet structures of β‐lactoglobulin. Intrinsic fluorescence intensity of ultrasound‐treated β‐lactoglobulin was increased with shift of λmax from 334 to 329 nm. UV absorption of β‐lactoglobulin was decreased with shift of λmax from 288 to 285 nm after ultrasound treatment. There were no significant changes in high‐performance liquid chromatography and protein electrophoretic patterns. These findings indicated that ultrasound treatment had high potential in modifying the physiochemical and structural properties of β‐lactoglobulin for industrial applications.
Highlights
Bovine β-lactoglobulin (~50%–55%) is the main fraction in whey proteins (Çelebioğlu, Gudjónsdóttir, Chronakis, & Seunghwan, 2016)
The maximum free sulfhydryl group content was 4.52 μmol/g at 45°C. β-Lactoglobulin may be denatured when the temperature was above 50°C
With the extension of ultrasonic time, ultrasound treatment changed the structural conformation of β-lactoglobulin and induced changes in surface hydrophobicity and free sulfhydryl group
Summary
Bovine β-lactoglobulin (~50%–55%) is the main fraction in whey proteins (Çelebioğlu, Gudjónsdóttir, Chronakis, & Seunghwan, 2016). It is a globular protein with 162 amino acids and a single polypeptide chain, including two disulfide bonds and one free sulfhydryl group at Cys121 (Papiz et al, 1986). Β-Lactoglobulin is a valuable ingredient in food manufacturing due to its high content of essential amino acids and versatility in terms of functional properties, such as gelling ability, emulsifying ability, and foaming ability (Bals & Kulozik, 2003). Dombrowski, Johler, Warncke, and Kulozik (2016) reported that β- lactoglobulin is widely applied to provide stability of foam structures for its pronounced surface activity.
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