Encapsulation of olive leaf extract by different hydrocolloids and potential use in tomato sauce formulations

Olive leaves are a byproduct of the olive industry. They contain valuable phenolic compounds sensitive to heat, light, and oxidizing agents. These phenolics offer numerous health benefits, and they can be effectively preserved by encapsulation. Olive leaf extract (OLE) is rich in antioxidants, antimicrobials, anti-inflammatory, and antihypertensive properties. Due to these properties, OLE holds great promise as a valuable ingredient in the food industry. This study aims to encapsulate and evaluate the potential use of olive leaf phenolic-antioxidant extract to enrich tomato sauce formulation. The OLE was encapsulated with different encapsulating agents like maltodextrin (MD), arabic gum (AG), and whey protein isolate (WPI) by freeze-drying. After encapsulation, tomato sauces were enriched with encapsulated OLE (1, 2, and 3%). Then, the panellist assessed the sensory attributes of enriched tomato sauces. Quality properties such as total soluble solids (TSS), pH, titratable acidity, colour, viscosity, total phenolic content, antioxidant activity, and microbiological analysis of tomato sauce samples were evaluated during the storage of 28 days at 4 °C. Panellists preferred tomato sauces enriched with 1% OLE. Encapsulated OLE with MD, AG, and WPI had an average particle size (D50) of 36.2, 32.6, and 86 nm, respectively. The total phenolic content of tomato sauces enriched with encapsulated OLE with WPI decreased by 30% during 28 days of storage. However, the stability of total phenolics improved in tomato sauces enriched with encapsulated OLE with AG and MD. The antioxidant activity of all samples tended to decrease during the storage at 4 °C. The results obtained from the study indicate that the incorporation of encapsulated OLE in the tomato sauce is an effective and natural approach to enhance the quality, as well as prolong its shelf life. Nevertheless, it is essential to conduct further research to determine the bioaccessibility of encapsulated OLE in tomato sauces. This will provide a better understanding of the extent to which the beneficial compounds are released, and made available for human consumption. Keywords: Olive leaf extract, encapsulation, tomato sauce, enrichment, quality.