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Sustained release of antimicrobials may be a viable solution to enhance the bioavailability during the shelf life of food products. In this work, spray-drying was used to encapsulate a model antimicrobial of lysozyme in corn zein. The effects of zein/lysozyme (20:1 to 4:1) and zein/thymol (1:0 to 4:1) ratios on the microstructures of microcapsules and in vitro release profiles of the encapsulated lysozyme were investigated. In all cases, less lysozyme was released at higher pH, resulting from stronger molecular attraction between zein and lysozyme. Nanoscalar matrix structures of microcapsules were correlated with release characteristics of the encapsulated lysozyme. At intermediate zein/lysozyme (10:1) and zein/thymol (50:1) ratios, microcapsules had a continuous matrix structure and showed sustained release (11.1-65.3%) of lysozyme at pH 6 over 49 days. This work may be developed into practical food grade delivery systems of antimicrobials.

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To develop edible delivery systems suitable for food applications, regulations require that solvents and ingredients are either generally recognized as safe or listed by the Food and Drug Administration as processing aids. In this work, we studied a food grade polymer-corn zein, a category of alcohol-soluble proteins, as the carrier material for microencapsulating bioactives. Zein is insoluble in aqueous solutions; zein-based delivery systems may thus maintain the integrity in aqueous food products during processing and storage. Three alcohols, i.e., ethanol, methanol, and isopropanol, with an appropriate amount of water were used to dissolve zein. A supercritical anti-solvent process was applied to synthesize micro-and nanoparticles of zein for edible delivery systems of bioactive compounds. We studied critical variables during the particle formation: polymer concentration, CO 2 flow rate, and co-solvent chemistry. Particles were produced only when mass transfer was fast enough that the co-solvent in the atomized droplets could be extracted by the reservoir CO 2 and polymers could nucleate and grow into particles. Manipulation of the above variables enabled the production of micro-and nanoparticles, which can be used as bases for microencapsulating bioactives. Our results demonstrated promising applications of the supercritical antisolvent technology to synthesize food grade delivery systems of bioactive food ingredients that can enhance the healthfulness, safety, and quality of food products.

The functionality of whey proteins can be modified by many approaches; for example, via complexation with carbohydrates, enzymatic cross-linking, or hydrolysis, and the objective of this work was to research the effects of supercritical carbon dioxide (scCO(2)) treatments on the functionalities of commercial whey protein products including whey protein isolates (WPI) and whey protein concentrates (WPC). The WPI and WPC powders and a 10% (wt/vol) WPI solution were treated with scCO(2). The WPI solution was treated at 40 degrees C and 10 MPa for 1 h, whereas WPI and WPC powders were treated with scCO(2) at 65 degrees C and 10 or 30 MPa for 1 h. Dynamic rheological tests were used to characterize gelation properties before and after processing. Compared with the unprocessed samples and samples processed with N(2) under similar conditions, scCO(2)-treated WPI, whether dispersed in water or in the powder form during treatments, formed a gel with increased strength. The improvement in gelling properties was more significant for the scCO(2)-treated WPC. In addition, the scCO(2)-processed WPI and WPC powders appeared to be fine and free-flowing, in contrast to the clumps in the unprocessed samples. Proximate compositional and surface hydrophobicity analyses indicated that both compositional and structural changes may have contributed to enhanced whey protein functionalities. The results suggest that functionalities of whey proteins can be improved by scCO(2) treatment to produce novel ingredients.