Extractable oil in microcapsules prepared by spray-drying: Localisation, determination and impact on oxidative...

Area of Science:

• Food Science and Technology
• Materials Science
• Chemical Engineering

Background:

• Microencapsulation of fish oil aims to improve stability and delivery.
• Spray-drying is a common technique for microencapsulation, but process conditions affect oil localization and stability.
• Understanding oil distribution within microcapsules is crucial for predicting product shelf-life.

Purpose of the Study:

• To determine the location of extractable oil in spray-dried fish oil microcapsules.
• To assess the impact of spray-drying conditions on oil localization and lipid oxidation.
• To propose methods for quantifying different oil fractions and evaluate their relation to shelf-life.

Main Methods:

• Confocal laser scanning microscopy (CLSM) for visualizing oil distribution.
• Scanning electron microscopy (SEM) for surface morphology analysis.
• Various extraction procedures to differentiate oil fractions.
• Oxidation assessment using hydroperoxide content, anisidine value, and propanal content.

Main Results:

• Extractable oil was predominantly found on the surface and in superficial oil droplets within microcapsules.
• Microcapsules with 50% oil load spray-dried at 210/90°C exhibited higher lipid oxidation (hydroperoxide, anisidine value).
• Propanal content increased in samples with 30% oil load spray-dried at 210/90°C.
• The amount of extractable oil only partially explained observed differences in lipid stability.

Conclusions:

• Surface oil plays a protective role for other oil fractions within microcapsules.
• The total amount of extractable oil is not a reliable predictor of the shelf-life for microencapsulated fish oil.
• Optimizing spray-drying conditions is essential for controlling oil localization and enhancing fish oil stability.