Journal of Agriculture and Food Research (Jun 2024)
Investigating the surfactant-to-oil ratio, type of ripening inhibitor, and modified starch on the stability of Carum copticum essential oil nanoemulsions: Application in yoghurt drink
Abstract
Carum copticum essential oil (EO) was spontaneously emulsified into the aqueous solution of octenyl succinate anhydride-modified starch by titrating a mixture of EO, corn oil, or medium-chain triglycerides (MCT) as ripening inhibitors (EO: oil, 30:70), along with Tween 80 as surfactant. This study aimed to prepare highly stable nanoemulsions using the lowest possible surfactant-to-oil ratios and modified starch percentages. Results revealed that for a surfactant-to-oil ratio of 0.5, to prepare stable nanoemulsions (O/W, 20:80) with corn oil (nano-corn) and MCT (nano-MCT) ripening inhibitors, a minimum content of 1.5 % and 1 % starch, respectively, was required. Both nano-corn and nano-MCT nanoemulsions showed no obvious phase separation after one month of storage or thermal stresses, attributed to electrostatic and steric stabilization created by starch addition. However, lower particle size growth was observed for nano-MCT compared to nano-corn. The antimicrobial activity of the EO nanoemulsions was investigated against challenging bacteria (Proteus mirabilis and Staphylococcus aureus) in vitro and yeasts (Rhodotorula mucilaginosa and Kluyveromyces lactis) in yoghurt drink. Scanning electron microscopy revealed different and severe damage to the morphology of bacteria compared to pure EO. Spoilage yeasts in yoghurt drink containing 4 % nano-corn reached undetectable levels during 28 days of storage at 4 °C. Yoghurt drink samples containing 4 % nano-corn received the highest sensory acceptance. All results indicate the feasibility of stabilizing EO nanoemulsions using modified starch while minimizing the use of synthetic surfactants. These prepared nanoemulsions exhibit strong anti-yeast activity and can serve as a pleasant flavor enhancer in the yoghurt drink industry.
