Structural Interaction between citrus fibre and fruit-based system for emulsion formulation

Aim: The citrus production is developed worldwide: not only fruits are used for fresh consumption, but also processed to extract juice, essential oils, and pectin. The insoluble residue at the end of the process is food-grade and commercialised as liquid pectin offering advantages in terms of cost and potential as innovative ingredient. Citrus fibre can stabilize low pH emulsions with high thermal resistance. It can enhance food mouthfeel and swallowing, making it suitable for elderly or people suffering from dysphagia. Method: In this work, rheological properties of citrus fibre emulsions were investigated, comparing their interaction with apricot puree against a water-based system. Both citrus fibre and apricot puree were characterized for particle size and chemical composition. Technological attributes of the fibre (oil binding, water binding, and emulsifying capacities) were evaluated. Emulsions at different concentrations of sunflower oil (20-25-30% w/w) and fibre (3-4-5% w/w) were evaluated via amplitude and frequency sweep tests to investigate the microstructure and assess interrelation among components. Results: Citrus fibre induced remarkable emulsion stability. Its effect varied significantly between water-based and fibre-based systems. Increasing fibre content in water-based systems led to a proportional reduction in oil release having the 4% and 5% samples no phase separation. Conversely, in apricot-based samples, high fibre content (4-5%) increased the resilience of the emulsion structure, but it enhanced the oil separation. In apricot puree, adding the apricot fibre to 3% citrus fibre yielded a total fibre percentage similar to the stability-conferring value in water-based samples. Rheological analysis identified the 4% fibre as creating the most stable structure. Conclusion: The research offered insights into citrus fibre interactions with other ingredients. Further study should delve deeper into fibre's interaction with lipophilic or hydrophilic micronutrients in emulsions.