Oxidation is a significant problem in processed foods affecting their physico-chemical, shelf life and health properties. Natural antioxidants could be viable alternatives to synthetic variants for safely improving antioxidation properties of processed foods. The aim of this study was to assess the singular and combined effects of beetroot and chocolate on the oxidative stability of a high fat and protein processed food (sponge cake) during storage and gastrointestinal digestion. Cakes were prepared and assessed for antioxidant potential, polyphenols, and oxidative stability, and macronutrient oxidation during simulated gastro-intestinal digestion. Beetroot significantly improved the antioxidant and polyphenol profiles of sponge cake which further improved with chocolate addition. Beetroot also significantly increased the oxidative stability and shelf-life of sponge cake, and these effects were enhanced when combined with chocolate. Chocolate significantly reduced lipid oxidation during the gastric phase of digestion. However, both chocolate and beetroot did not curtail lipid oxidation in the intestinal phase, nor protein oxidation at any of the phases. Promisingly, beetroot and chocolate addition did not affect textural parameters and delayed staling by up to 2 days. Overall, the benefits of beetroot and chocolate addition were manifested more in the food system than during its digestion. Beetroot improves the oxidative stability and shelf life of processed foods, and its effects could be enhanced through combining with other natural products.
Keywords: Antioxidants; Beetroot; Chocolate; Gastrointestinal digestion; Oxidation; Oxidative stability; Processed foods.