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The effects of lecithin addition at different concentrations (0-2.0%) on the physicochemical and emulsifying properties of mussel water-soluble proteins (MWP) were investigated. In solution system, low lecithin concentration (0.5%-1.0%) induced the aggregation and increased turbidity of composite particles. Lecithin addition caused changes in secondary structure and induced partial unfolding of MWP. Hydrophobic interactions between MWP and lecithin may contribute to the exposure of chromophores and hydrophobic groups of MWP. The interfacial tension decreased with lecithin addition. However, at a high lecithin concentration (1.5%-2.0%), the degree of aggregation and state of unfolding alleviated due to competitive adsorption. In emulsion system, with the low concentration of lecithin addition (0.5%-1.0%), droplet size and surface charge of emulsion decreased. The emulsion activity index, emulsion stability index, percentage of adsorbed protein increased. Both creaming stability and viscoelastic properties improved. At an intermediate lecithin concentration (1.0%), the emulsion showed the highest physical stability, while further addition of lecithin caused a slight deterioration in emulsifying properties. Overall, these results indicated the possibility that the lecithin-MWP mixed emulsifiers can be used to obtain emulsions with desirable properties.

Emulsifiers are usually incorporated in emulsion preparation to make kinetically stable emulsions. HPH is often used to prepare food emulsions, producing stable emulsion with fine texture. The purpose of this study is to investigate the effect of high-pressure homogenization (HPH) at 40, 80 and 120 MPa on oil-in-water (O/W) emulsion stabilized with mussel myofibrillar proteins (MMP) and lecithin. Emulsifying properties, creaming index, microstructure, particle size and zeta-potential, apparent viscosity of HPH treated emulsions, together with protein solubility and surface hydrophobicity were analyzed. HPH treatment resulted in increase in emulsifying activity index (from 56.93 to 87.68 m2/g), emulsifying stability index (from 59.33 to 154.62 min), apparent viscosity and absolute zeta-potential (from 10.67 to 37.03 mV) of MMP and lecithin stabilized O/W emulsion. Droplets size (from 3.95 to 0.46 μm) and creaming index of high-pressure homogenized emulsion reduced. These changes may resulte from the improved solubility (from 16.5% to 75.1%) and exposed hydrophobic groups (from 196.37 to 258.50) of MMP. The most suitable processing pressure to produce fine and stable emulsions was 80 MPa. These results will contribute for improving the formulation of emulsions and their properties and provide new understanding into MMP as a natural emulsifier in the food production.

Structural and functional changes in ultrasonicated oyster protein isolates (OPI) were investigated. Ultrasound treatments were carried out with probe (20 kHz) at 200, 400 and 600 W for 15 and 30 min. The results showed that functional properties of OPI significantly improved after sonication. Absolute zeta potential and protein solubility increased by 18.40 mV and 82.5 % at 600 W for 15 min. Oil holding capacity, emulsifying activity index, emulsion stability index, foaming ability and foaming stability increased by 300 %, 15.23 m2/g, 9.24 min, 23.9 % and 14.8 % at 600 W for 30 min. However, ultrasound treatment significantly (P< 0.05) decreased particle size and water holding capacity. The conformation of OPI became stretched and unfolded after sonication. Functional improvements resulted from stretched and unfolded conformation and reduction of particle size. Controlled condition of ultrasound can produce OPI with distinct structural and functional properties, which could meet the complex needs of manufactured food products in food industry, but further study is needed to understand the specific mechanism.

This study investigated the effects of high-intensity ultrasonication (HIUS) treatment (0, 5, 10, 20, 30 min) on the physicochemical and functional properties of mussel sarcoplasmic proteins (MSP). MSP dispersion was treated by HIUS (20 kHz) at 600 W for 5, 10, 20 and 30 min. The results showed that HIUS treatment changed the physicochemical properties of MSP, thereby increasing the stability of the emulsion stabilized by ultrasonicated MSP. HIUS treatment improved the functional properties of MSP, including solubility, foaming ability, foaming stability, emulsifying activity index, emulsifying stability index, percentage of adsorbed proteins. More uniform emulsions with smaller droplets and higher stability were observed. There was a decrease in particle size, zeta-potential and turbidity of ultrasonicated MSP. Proteins partially unfolded as a result of HIUS treatment. Associations between conformation structure, physicochemical properties and functional properties were also found. It can be speculated that improvements in functional properties were caused by the changes in conformation structure and physicochemical properties. The results suggested that HIUS treatment has great potential in modifying the foaming and emulsifying properties of shellfish proteins, and ultrasonication treatment at 20 kHz, 600 W for 20 min was the optimum condition for modification.

High‐pressure homogenization (HPH) under 0–100 MPa was performed to treat clam protein isolate (CPI) for three cycles. Results indicated that HPH treatment resulted in significant improvements of CPI functional properties. Absolute zeta potential, emulsifying activity index, and emulsion stability index significantly increased by 19.37 mV, 33.26 m²/g, and 14.00 min after HPH under 100 MPa. Solubility of CPI dramatically increased by 70.8% under 80 MPa. Foaming ability and foaming stability increased by 33.8% and 14.4% under 60 MPa. HPH resulted in significant decrease in percentage of both α‐helix and β‐turn, but percentage of β‐sheet greatly improved as the pressure increased. Free sulfhydryl and surface hydrophobicity increased but fluorescence intensity decreased significantly after HPH treatment. Improvements of these functionalities were due to protein structure changes and particle size reduction. This study demonstrated that HPH has the potential to improve functional properties of shellfish protein through modifying protein structure. PRACTICAL APPLICATIONS: A nonthermal processing technique using HPH can improve functional properties of CPI, including solubility, emulsifying properties, and foaming properties. Therefore, HPH can be potentially used to process shellfish proteins to improve their functional properties.