Characterization of Emulsion-Filled Confectionery Gels: The Effect of Medium-Chain Triglyceride Content and Lecithin

Abstract

The expansion of gummy and jelly confections into new markets has resulted in the creation of unique products containing vitamins, THC/CBD extracts, fish oils, and other bioactive compounds. Often times, these ingredients are extracted in oil or are oils themselves. The addition of these lipid-based ingredients into a gel matrix creates an emulsion-filled gel, with the lipid phase acting as either active or inactive fillers in a continuous polymeric gel phase. While the addition of active and inactive fillers to various plain hydrogel systems has been well studied, further research on the effect of active/inactive fillers in confectionery gels is needed. To better understand the effect of lipid fillers on the characteristics of confectionery gels, medium-chain triglycerides (MCTs) were added to three different confectionery gel systems (gelatin, starch, and pectin) at three different levels with and without lecithin. Each gel system was formulated to have a consistent water content of the fat-free gel phase, which was verified using Karl Fischer titration. The fat globule distributions of all gummies and jellies were measured using microscopy and image analysis. While there were some differences between the fat globule distributions of gelatin and starch gummies and jellies, they were small enough to have minimal impact on the characteristics of the gels. Characterization of all gels was done to determine the textural, rheological, and surface active properties. The surface activity of gels was determined via measurement of the contact angle of water and diiodomethane formed at gel surfaces, which allowed changes in polar, dispersive, and total surface energies to be monitored. Gelatin gels were determined to have hydrophobic surfaces, while starch and pectin gels were hydrophilic. As MCT was added to gummies and jellies, a general trend of increased water contact angle and decreased diiodomethane contact angle occurred. This was due to the presence of oil droplets at the surface of the gel. Lecithin did not

have a large impact on surface properties, except in control pectin gels (p<0.05). The presence of oil at the surface of gels decreased the overall surface energy, which was reflected in the adhesive properties measured via texture analysis. Both gelatin and pectin gels saw a decrease in adhesiveness and tack force upon addition of MCTs, aligning with the decrease in surface energy. Starch systems did not show a large change in adhesiveness, which was due to the presence of a starch crust. Lecithin did not largely impact the adhesiveness or tack force. The hardness of gels was also measured with texture analysis. Pectin gels were the hardest, and gelatin gels were the weakest. Gels all showed different changes in hardness upon MCT and lecithin addition, with insignificant decreases in gelatin and starch gel hardness. Pectin jellies displayed a possible concentration-dependent effect on gel hardness upon MCT and lecithin addition. In the presence of lecithin, gels were strengthened at low levels, and weakened at moderate levels, whereas the opposite trend occurred without lecithin. The viscoelastic moduli of gels were also determined by small-angle oscillatory shear rheology, which did not always agree with texture results. In gelatin and starch systems, MCTs appeared to act as inactive fillers, weakening the gel structure, with little effect from the addition of lecithin. Despite the weakening of gelatin systems with MCT addition, there was an increase in the melting point of gelatin gels. This could suggest an interaction between gelatin and MCT globules. In pectin systems, fat globules possibly acted as active fillers, increasing viscoelastic moduli. These findings could be beneficial for scientists in research and development of functional gummy or jelly products containing oil-based ingredients. Understanding the changes in gel structure upon addition of oil can allow for greater optimization of hydrocolloid use, while the decrease in adhesives properties could be beneficial for reducing product sticking in packaging.