# Effects of gelatin type and concentration on the preparation and properties of freeze-dried fish oil powders

## TL;DR

This study examines how different types and concentrations of gelatin affect the preparation and properties of freeze-dried fish oil powders.

## Contribution

The study reveals that cold-water fish skin gelatin cannot form complex coacervates, which is crucial for oil powder preparation.

## Key findings

- Cold-water fish skin gelatin (CFG) could not form complex coacervates due to its unique properties.
- Gelatin type significantly influenced the peroxide values of the oil powders, with PSG showing the lowest values.
- SSOS improved coacervate stability and oil digestion during in vitro gastrointestinal simulation.

## Abstract

The effects of gelatin type (porcine skin gelatin, PSG; bovine skin gelatin, BSG; fish gelatin, FG; or cold-water fish skin gelatin, CFG) and concentration on the preparation and properties of fish oil powders were investigated in this work. The oil powders were prepared using the combination method of gelatin-sodium hexametaphosphate complex coacervation with starch sodium octenyl succinate (SSOS)-aided freeze-drying. Compared with the other gelatins, CFG—with an unobvious isoelectric point, a lower molecular weight, more hydrogen bonds, and longer gel formation time—could not form complex coacervates, which are necessary to prepare oil powders. For oil powders obtained from the other gelatins, gelatin type and concentration did not have obvious effects on microscale morphologies; they did, however, have significant effects on physicochemical properties. The highest peroxide values of the oil powders were mainly dependent on the gelatins, expressed in the following manner: PSG (153 ± 5 – 168 ± 3 meq/Kg oil) < BSG (176 ± 5 – 188 ± 1 meq/Kg oil) < FG (196 ± 11 – 201 ± 22 meq/Kg oil). Acidic and neutral pH could not dissolve the complex coacervates. However, the oil powders could be quickly dissolved to form emulsion droplets in the gastric phase, and that SSOS increased coacervate stability and promoted oil digestion during the in vitro gastrointestinal process. In sum, this study contributes fundamental information to understanding the development of fish oil solid encapsulation preparations.