Microencapsulation of fish oil by spray-drying using two different wall materials: a comparison

Abstract

Oils and fats have a wide range of health benefits, especially those that have a high concentration of polyunsaturated fatty acids, like fish oils. Unfortunately, oils are highly susceptible to heat, light, and oxygen degradation, causing them to lose the qualities that would make them interesting for the public. With this in mind, this study compared two methods of spray-drying, a technique that helps preserve the stability of oils in storage for longer periods of time. Emulsions made with skimmed milk powder and with maltodextrin and whey protein hydrolysate were spray-dried, resulting in 2 different microencapsulated fish oils. They were compared regarding encapsulation efficiency, water activity, moisture content, and peroxide index. The skimmed milk showed better results, with a 28.17% lower peroxide index than the non-encapsulated oil and lower water activity and moisture content compared to the emulsion using maltodextrin (2.690±0.19% vs 6.747±0.29% moisture content and 0.376±0.013 vs 0.554±0.006 water activity). Since skimmed milk powder is rather cheap, it is ideal for spray-drying, a simple and fast technique. In this way, fish oil can be safely microencapsulated in powder form, lasting longer than the oil capsules currently available, since the oil is protected from light, temperature, moisture, and oxidation. In addition, the oily odor is masked, making it more appealing to the consumer, and it may be combined with other powders, like vitamins and minerals, which opens up new possibilities for the production of supplements.

Figure 1. Microcapsules obtained after spray-drying emulsions E1 and E2. E1 presented hard clumps of maltodextrin and E2 was a smoother powder. Whey protein hydrolysate and skimmed milk powder were used as emulsifying agents in E1 and E2, respectively.

Figure 2. Microcapsules observed using scanning electron microscopy at 500× magnification (scale bar=50 μm). The capsules serve as a barrier, enveloping the oil inside. E1 (left side) had larger capsules, some of them with cracks on the capsule wall and many capsules clumped together. E2 (right side) had smaller capsules that were better spread throughout the area, with little or no cracks on the capsule wall.