Pickering emulsions stabilized by soybean protein isolate/chitosan hydrochloride complex and their applications in essential oil delivery

In this work, fabrication of soybean protein isolate (SPI)/chitosan hydrochloride (CHC) composite particles stabilized O/W Pickering emulsions using soybean oil as an oil phase was optimized by examining the effects of pH, SPI/CHC mass ratio, SPI/CHC composite particle concentration and oil phase fraction on the stability of the emulsions. The results showed that under the conditions of SPI/CHC mass ratio 1:1, pH 4 and particle concentration 2 %, the SPI/CHC composite particles could stabilize the emulsions with oil phase fraction up to 80 %. At an oil phase fraction of 60 %, the emulsions had a minimum particle size. The microstructure, storage and oxidation stabilities and rheological properties of the emulsions were determined. Using this SPI/CHC composite particle-stabilized Pickering emulsion template, citrus essential oil (CEO) Pickering emulsion (CEOP) was prepared. CEOP was found to markedly inhibit two food-related microorganisms, Staphylococcus aureus and Escherichia coli. In addition, the CEOP emulsion dilution (containing 4500 μL CEO/L) not only improved the water solubility of CEO, but also effectively retarded the browning and bacterial growth of fresh-cut apple. The SPI/CHC-stabilized Pickering emulsion template constructed in this work provides a promising alternative for the delivery of antimicrobial essential oils in the food industry.

Esterified Soy Proteins with Enhanced Antibacterial Properties for the Stabilization of Nano-Emulsions under Acidic Conditions

Soy protein isolate (SPI), including β-conglycinin (7S) and glycinin (11S), generally have low solubility under weakly acidic conditions due to the pH closed to their isoelectric points (pIs), which has limited their application in acidic emulsions. Changing protein pI through modification by esterification could be a feasible way to solve this problem. This study aimed to obtain stable nano-emulsion with antibacterial properties under weakly acidic conditions by changing the pI of soy protein emulsifiers. Herein, the esterified soy protein isolate (MSPI), esterified β-conglycinin (M7S), and esterified glycinin (M11S) proteins were prepared. Then, pI, turbidimetric titration, Fourier transform infrared (FTIR) spectra, intrinsic fluorescence spectra, and emulsifying capacity of esterified protein were discussed. The droplet size, the ζ-potential, the stability, and the antibacterial properties of the esterified protein nano-emulsion were analyzed. The results revealed that the esterified proteins MSPI, M7S, and M11S had pIs, which were measured by ζ-potentials, as pH 10.4, 10.3, and 9.0, respectively, as compared to native proteins. All esterified-protein nano-emulsion samples showed a small mean particle size and good stability under weakly acidic conditions (pH 5.0), which was near the original pI of the soy protein. Moreover, the antibacterial experiments showed that the esterified protein-based nano-emulsion had an inhibitory effect on bacteria at pH 5.0.

Effect of carbon dots in combination with aqueous chitosan solution on shelf life and stability of soy milk

Use of carbon dots (CDs) in combination with aqueous chitosan solution to extend shelf life and improve stability of soy milk was investigated. Soy milk samples with chitosan solution (0.00%, 0.08%, 0.12%, 0.16% and 0.20%) and banana-based CDs (4%, 6% and 8%) were prepared and stored at room temperature (25-30 °C) for shelf life evaluation. Soy milk with 0.16% chitosan solution exhibited improved stability as evident by increased viscosity, stability coefficient, zeta potential and decreased centrifugation rate compared with soy milk without chitosan. The suitable amount of carbon dots could effectively inhibit the growth of Escherichia coli, Staphylococcus aureus and Bacillus subtilis. Soy milk with 0.16% chitosan and 8% CDs exhibited longer shelf life and significantly lower total bacterial count after storage at room temperature for up to 4 days. Electronic nose-based flavor characteristics of all treated soy milk samples were not far from that of the control sample.

Plant protein-based delivery systems for bioactive ingredients in foods

The application of food-grade delivery systems for the encapsulation, protection and controlled release of bioactive food ingredients have recently gained increasing interest in the research fields of functional foods and pharmaceutics. The preparation and application of bifunctional particles provide a novel perspective for the design of plant protein-based delivery system.