Formation and stability of chia oil nanoemulsions

CENSI, NICOLÁS; JULIO, LUCIANA M.; TOMÁS, MABEL C.

Congreso; XVIII CONGRESO ARGENTINO DE CIENCIA Y TECNOLOGÍA DE ALIMENTOSIX SIMPOSIO INTERNACIONAL DE NUEVAS TECNOLOGÍAS VII SIMPOSIO LATINOAMERICANO SOBRE HIGIENE Y CALIDAD DE ALIMENTOS, V SIMPOSIO DE INNOVACIÓN EN INDUSTRIAS ALIMENTARIAS 2023; 2023

Asociación Argentina de Tecnólogos Alimentarios - AATA

Chia oil is an excellent source of omega-3 fatty acids and natural antioxidants. Therefore, its incorporation into food is desirable as well as challenging due to its oxidative instability. Delivery systems based on emulsions have proved to be a strategy to overcome the sensitivity of such compounds. Among them, nano-emulsions may be effective systems to protect and deliver chia oil into functional foods and present advantages over conventional emulsions. Likewise, heat-treatments like pasteurization employed to preserve a wide range of food products concerning microbial safety can affect nano-emulsions stability. Thus, this study aimed to develop chia oil nano-emulsions and to evaluate their physicochemical and thermal stability. Oil-in-water (O/W) nano-emulsions containing 10%w/w of chia oil and 2%w/w of sodium caseinate (CAS) were formed using a high-energy emulsification process, which included a former step in a laboratory scale disperser (10000 rpm, 2 min) and a latter using a microfluidizer at three pressure levels (600, 1000, and 1200 bar). The obtained emulsions were stored at 4 °C for 50 days. Initial characterization of emulsions was performed through the evaluation of droplet size, zeta-potential, rheological properties, and confocal laser scanning microscopy. In addition, the long-term stability of nano-systems was monitored through BS profiles, primary oxidative products, and omega-3 content. Finally, their droplet sizes and hydroperoxide values were measured after thermal processing (72°C, 15s) application to evaluate the thermal stability of systems.The droplet sizes of systems expressed as D4.3 ranged from 151.3 to 206.3 nm being significantly higher for emulsions obtained at 600 bar. According to this, emulsions obtained at 1000 and 1200 bars can be classified as O/W nano-emulsions. Droplet size results were in concordance with microscopy images; it was also observed the absence of flocs or aggregates. The superficial charge of droplets at pH ~6.5 resulted in negative values (-35 to -44 mV) for all systems which could be associated with the charge of CAS above its pI. Regarding rheological properties evaluated at 25°C, all nano-systems presented Newtonian behaviour (n=1) and similar apparent viscosities at a shear rate of 100 s-1 of ~0.002 Pa.s. Systems prepared at 1000 and 1200 bar remained stable throughout the entire refrigerated storage while those obtained at 600 bars recorded some signs of the creaming process after 9 days of storage. Additionally, the primary oxidative products determined by PV values resulted in low levels during the 50 days of storage. Similarly, the omega-3 content of systems (65-68 %) remained unchanged during the studied period.Concerning the thermal stability of nano-emulsions, both the droplet sizes and the hydroperoxides values were unaffected after the heat-treatment application. Based on these results nano-emulsions obtained by microfluidization at 1000-1200 bar could be suitable delivery systems for chia oil.