Edible Coating Extends Fish Shelf Life

CORVALLIS, Ore.—Oregon State University scientists have extended the shelf life of lingcod fillets and possibly made them more nutritious by dipping them into an edible, protective coating enriched with fish oil. Researchers found that the coating tripled the omega-3 fatty acids in the refrigerated and frozen fish when compared against the uncoated fish.

The liquid coating contained chitosan, which comes from crustacean shells and can be made into film for food wrapping to keep out bacteria and fungi and prolong storage life. What's unusual about the OSU study is that fish oil was added to the chitosan coating, which wasn't visible once it dried. After the coating was applied, some fillets were refrigerated for three weeks while others were frozen for three months.

"With this coating, you can easily keep the fillets in the display case for two to three more days," said OSU food science professor Yanyun Zhao, lead researcher in the study.

The study also found that the coating reduced lipid oxidation, which causes rancidity, in the refrigerated and frozen samples when compared with the uncoated fillets. The coating also kept the fish moister than the uncoated samples as the frozen ones were thawing. Additionally, the coating delayed the growth of microorganisms in the fresh fillets, and it prevented their growth in the frozen ones. The coating did not affect the color of the fillets.