2025

abstract

english

EN Emulsions are thermodynamically unstable systems that consist of two immiscible liquids: a dispersed phase and a continuous phase. To obtain kinetically stable emulsions, it is necessary to add substances known as emulsifiers and stabilisers [1]. Such compounds include surfactants or hydrocolloids, among others. Lecithin (LS) is a complex mixture of acetone-insoluble plant phospholipids [2]. Due to its emulsifying properties, it is commonly used in the food, pharmaceutical and cosmetic industries [3]. HPMC, due to its thickening ability, dimensional stability and anti-dispersibility, is widely used polymer, mostly as a flocculant in the construction industry [4]. The combination of lecithin and hydrocolloid may be an interesting strategy for designing fat replacements in food matrices. The aim of this study is to investigate the rheological properties and stability of oil-in-water emulsions containing hydroxypropylmethylcellulose (HPMC) and lecithin (LS). The dispersed phase was rapeseed oil, linseed oil and corn oil at 30% vol. (the viscosities of the oils at 20 ̊C are: rapeseed oil: 0.072 (Pa∙s), linseed oil: 0.047 (Pa∙s) and corn oil: 0.0325 (Pa∙s). HPMC concentration was 1% and lecithin concentrations were 1, 3 and 5%. An Anton Paar Physica MCR 501 rheometer and a LAMY RM-100 plus rheometer were used to plot the viscosity and flow curves of the emulsions. A T18 digital ULTRA TURRAX homogeniser was used to disperse rapeseed oil, linseed oil and corn oil in the test samples, while a Nikon Eclipse 50i Polarising Microscope was used to take images of the droplets after homogenisation. The aqueous solutions of lecithin used are Newtonian fluids, whereas HPMC exhibits the properties of a shear-thinning fluid, as viscosity decreases with increasing shear rate. The addition of LS to HPMC results in a significant increase in viscosity, especially at low shear rates. The highest viscosity was obtained for emulsions with corn oil. The emulsions obtained are viscoelastic fluids with fairly good stability.The emulsions with higher lecithin concentrations of 3% and 5% show the greatest stability. Based on the analysis of the results obtained, it can be concluded that the addition of lecithin to the HPMC solution significantly increases its viscosity and that raising emulsions are stable systems with viscoelastic properties. Moreover, emulsions with the addition of HPMC and lecithin are also characterised by greater stability.

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1st International Conference PUT STEM Day 2025: book of abstracts

1st International Conference PUT STEM Day 2025 : Science Technology Engineering Mathematics, 10.01.2025, Poznań, Polska