Effects of micro- and nano-sized emulsions on physicochemical properties of emulsion–gelatin composite gels

Abstract

In this study, we aimed to investigate the effects of emulsion droplet size on the physicochemical and rheological properties of emulsion–gelatin composite gels. Gelatin or lecithin solutions (1–4%) as emulsifiers were homogenized with canola oil using a high-speed and/or high-pressure homogenizer to obtain micro- and nano-sized emulsions. Gelatin (8%) was mixed with an equal amount of the prepared emulsion and subsequently cooled at 4 °C for cold-set gelation. Gel strength of the emulsion–gelatin composite gels was higher when the concentration of gelation was increased, regardless of the droplet size of the emulsion. In terms of droplet size, gel strength, G′, and water-holding capacity of emulsion–gelatin composite gels with nano-sized emulsions were significantly higher than those of gels with micro-sized emulsions, except for lecithin. Fourier-transform infrared and differential scanning calorimetry analyses of emulsion–gelatin composite gels revealed that the emulsion size had a significant effect on the physicochemical properties of the gels, except for lecithin. Conformationally, droplet size influenced the gel strength of the emulsion–gelatin composite gels owing to the high specific surface area of the nano-sized droplets, which formed a relatively high number of junctions of gelatin random coils during cold-set gelation.