Enhancing Set-Type Yoghurt With Olive Leaf Extract: A Comparison of Powdered Addition and Surface Spraying on...

Area of Science:

• Food Science
• Food Technology
• Nutritional Science

Background:

• Olive leaf extract (Olea europaea L.) is a cost-free byproduct of the olive industry.
• There is growing interest in utilizing natural compounds as functional and antimicrobial agents in food products.

Purpose of the Study:

• To investigate the impact of powdered olive leaf extract (POLE) on the physicochemical, textural, functional, microbiological, and sensory properties of yoghurt.
• To evaluate different application methods (pre-fermentation addition vs. post-fermentation surface spraying) and concentrations of POLE.

Main Methods:

• Yoghurt was enriched with POLE via two methods: addition before fermentation (0.4%, 0.6% w/v) and spraying aqueous solutions post-fermentation (0.4%, 0.6%).
• Analysis included physicochemical composition, color, texture, total phenolic content, antioxidant activity, microbial counts, and sensory evaluation over 28 days of storage.

Main Results:

• POLE addition did not alter basic yogurt composition (solids, fat, protein, ash) or texture/color when sprayed.
• Yoghurt enriched with POLE before fermentation showed increased total phenolic content and antioxidant capacity.
• POLE exhibited antimicrobial effects without negatively impacting viable yoghurt bacteria counts.
• Surface spraying of POLE prevented the bitter taste associated with pre-fermentation addition.

Conclusions:

• Powdered olive leaf extract (POLE) is a viable functional and antimicrobial agent for yoghurt.
• Post-fermentation surface spraying of POLE offers a method to improve yoghurt's functional properties while maintaining desirable sensory characteristics.
• Olive leaf waste presents a sustainable source for developing novel food ingredients.