Microencapsulation of fish oil using spray drying for fortification of bakery products

Introduction

According to the International Society for the Study of Fatty Acids and Lipids, most Western diets provide less than one-third of the recommended daily intake of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) the two long-chain omega-3 fatty acids most strongly linked to cardiovascular protection [1] . Fortifying staple bakery products with fish oil is one of the most direct strategies for closing this gap, but the extreme susceptibility of omega-3 fatty acids to oxidation creates both flavour and shelf-life problems that have limited commercial adoption [2] . Spray drying is the most widely used industrial technique for microencapsulating heatsensitive food oils because it is fast, scalable, and relatively inexpensive compared to freeze drying or coacervation [3] . The choice of wall material determines how well the dried powder protects the core oil from oxygen, light, and moisture [4] . Maltodextrin is the default carrier in many spray-drying applications because of its low cost and good solubility, but used alone it forms a porous matrix with limited emulsifying capacity [5] . Combining maltodextrin with surface-active biopolymers such as whey protein isolate, gum arabic, or modified starch can create denser, less permeable shells that slow lipid oxidation [6,7] . While several reports have compared wall materials for fish oil encapsulation at the powder level, fewer have followed through to measure the sensory and nutritional outcomes when the resulting powder is baked into bread [8] . This research aimed to compare four wall material systems for spray-dried fish oil, assess their oxidative stability over 30 days, and evaluate the sensory acceptability and omega-3 delivery of fortified wheat bread.

Material and Methods

Reagents and material

Refined menhaden fish oil (EPA 18.2%, DHA 12.4%) was purchased from Sigma-Aldrich (Taufkirchen, Germany). Maltodextrin DE 18 was obtained from Cargill (Krefeld, Germany). Whey protein isolate (90% protein) was supplied by Fonterra (Auckland, New

Methods

Four emulsions were prepared at a core-to-wall ratio of 1:3 (w/w) and total solids of 30%. Each wall material combination was dissolved in distilled water, fish oil was added, and the mixture was homogenised. The emulsions were spray-dried in triplicate. Encapsulation efficiency was calculated as (total oil -surface oil) / total oil × 100 [9] . Powders were stored in sealed amber vials at 25°C for 30 days, and peroxide values were measured at days 0, 10, 20, and 30. For bread fortification, the best-performing powder (MD+WPI) was incorporated into a standard wheat bread recipe at 1%, 3%, and 5% flour substitution. Sensory evaluation was conducted by 20 untrained panellists using a 9-point hedonic scale. Data were analysed by one-way ANOVA with Tukey's HSD (p<0.05) in SPSS 28.0.

Results

The four wall material systems differed markedly in encapsulation efficiency and oxidative stability. MD+WPI consistently delivered the highest protection for the core fish oil, both as a powder and when baked into bread. Interpretation MD+WPI microcapsules offered the best combination of high encapsulation efficiency, low oxidative degradation, and acceptable sensory performance in bread. At 3% flour substitution, the fortified bread delivered 142 mg EPA+DHA per 50 g serving roughly 10% of the daily recommended intake without a detectable fishy off-flavour. Increasing substitution to 5% pushed aroma and taste scores below acceptability thresholds, confirming that 3% is the practical upper limit for this wall material system.

Discussion

The encapsulation efficiency of MD+WPI (84.6%) exceeded that of MD alone (72.4%) by 12 percentage points. This gap is consistent with findings by Jafari et al. [6] , who attributed the superior performance of whey protein to its ability to form a viscoelastic film at the oil-water interface during atomisation, producing denser and smaller particles that trap more oil inside the matrix [10] . The smaller particle size of MD+WPI capsules (8.3 µm vs. 14.7 µm for MD) supports this interpretation, as smaller droplets generally experience faster shell formation during drying [11] . The peroxide value of MD+WPI capsules after 30 days (1.4 meq/kg) remained well below the 5 meq/kg threshold commonly used as a quality limit for edible oils [12] . MD alone reached 3.8 meq/kg at the same time point, suggesting that without a protein barrier, oxygen diffuses readily through the maltodextrin matrix. And because peroxide value is the most reliable early indicator of lipid rancidity, the threefold difference between these two treatments translates directly into shelf-life advantage for the whey protein formulation. The sensory data confirmed that 3% microcapsule substitution is the sweet spot for bread fortification. At this level, aroma and taste scores remained above 7.0, which is generally regarded as the threshold of commercial acceptability. The 5% level, however, produced a faint but detectable off-note that several panellists described as slightly oily, indicating that the wall material's flavourmasking capacity has limits even in the best formulation [13,14] .

Conclusion

This research set out to identify the best wall material for spray-dried fish oil microcapsules intended for bakery fortification. Maltodextrin combined with whey protein isolate delivered the highest encapsulation efficiency (84.6%), the lowest oxidative deterioration over 30 days (1.4 meq/kg peroxide value), and the best sensory performance when baked into wheat bread at 3% substitution. The fortified bread provided 142 mg EPA+DHA per serving without off-flavours, demonstrating a practical pathway for omega-3 enrichment of everyday bakery products. Future research should examine the stability of these microcapsules under accelerated shelf-life conditions and test their performance in other bakery matrices such as biscuits and muffins.

Acknowledgement

Acknowledgements Contributions: Ms. Katrin Brandt assisted with spray drying operations and sensory panel coordination. Funding sources: This work was supported by the Holstein College of Dairy Sciences applied research fund. Institutional support: The Microencapsulation Laboratory provided all equipment and analytical facilities.

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