Nutritional Assessment of Oil Extracted from Doughnuts Prepared Using Locally Processed Vegetable Oil and Industrially Processed Butter

Abstract

This study assessed the physicochemical characteristics, fatty-acid composition and elemental profiles of lipid materials associated with doughnuts prepared using locally processed vegetable oil and industrially processed butter. Four samples were analysed: locally processed oil (K₁), industrially processed butter (P₁), used oil collected after frying (D), and oil extracted from the fried doughnut (H). Physicochemical indices were determined using standard methods, fatty-acid methyl esters were analysed by gas chromatography–mass spectrometry, and elemental concentrations were measured by inductively coupled plasma–optical emission spectrometry. One-way analysis of variance and Tukey’s HSD were used to examine sample differences, and nutritional contributions were estimated for 100 g of the analysed lipid material. K₁ recorded the highest acid value (7.01 mg KOH/g), free fatty-acid content (3.51%) and saponification value (428.44 mg KOH/g), whereas H had the highest peroxide value (53.00 meq/kg). P₁ exhibited the highest iodine value (34.28 g I₂/100 g). Twenty-three fatty-acid methyl esters were identified. Lauric, myristoleic and myristic acids were prominent in K₁, D and H, while P₁ contained higher concentrations of palmitic acid and the reported linoleic/oleic acid methyl ester. Differences among fatty-acid classes were not statistically significant; polyunsaturated fatty acids had the largest effect size (η² = 0.270). Potassium was the most abundant measured element, while sodium was highest in P₁. These results provide a comparative characterisation of the analysed lipid fractions without attributing all observed differences exclusively to frying.