EXTRUSION PROCESS FOR ENCAPSULATION OF ESSENTIAL OILS: A SUSTAINABLE TECHNOLOGY FOR DEVELOPING NATURAL PRESERVATIVES FOR BAKERY APPLICATIONS

The demand for clean-label and sustainable foods has encouraged the replacement of synthetic preservatives in bakery products by natural alternatives. Essential oils represent promising natural preservatives due to their antimicrobial compounds. However, their direct application in bread is limited by volatility, degradation, flavor and interference in yeast fermentation. Thermoplastic extrusion emerges as a sustainable, solvent-free, and scalable technique for encapsulating hydrophobic bioactives in starch-based systems, enabling their protection and controlled release. This study aimed to develop and characterize starch particles containing an optimized mixture of oregano and thyme essential oils through two extrusion techniques: free addition and pre-emulsified mixture extrusion. In the free addition technique, the essential oil mix was directly injected into the extruder along with the starch matrix, while in the pre-emulsified process the oils were previously dispersed in a stable and optimized emulsion before injection into the same type of starch matrix. The starchy matrices were prepared by mixing high-amylose and waxy starches to obtain systems with 50% and 70% amylose, allowing the evaluation of the influence of amylose content on the structural organization and retention capacity of the oils. The particles were analyzed for moisture, particle size, and morphology. The encapsulated systems were incorporated into bread dough to assess their technological functionality, and dough rheology was evaluated through farinograph analysis. Microscopy revealed distinct morphologies between the two extrusion techniques: in the free addition process, oil droplets showed heterogeneous distribution and localized agglomeration, particularly in high-amylose systems, whereas the pre-emulsified process produced a more homogeneous dispersion of oil throughout the starch matrix. Farinograph results indicated variations in dough development time, with a stronger interaction on the gluten network. Visual assessment of fungal growth during storage showed that bread containing encapsulated particles exhibited delayed spoilage and extended shelf life compared to those with the free, non-encapsulated essential oil mixture. The sustainable extrusion process proved efficient for producing stable starch-based systems capable of functioning as natural preservatives, contributing to clean-label bakery products.