The shelf life of lingcod fillets has been extended by Oregon State University researchers who have also made them more nutritious by dipping them into an edible, protective coating enriched with fish oil.
The research may give consumers a chance to eat longer-lasting, potentially healthier fish fillets.
"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, the lead researcher in the study.
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.
The study, which has been accepted for publication in the journal Food Chemistry, found that the coating tripled the omega-3 fatty acids in the refrigerated and frozen fish when compared against the uncoated fish.
Omega-3 fatty acids are found in oily fish like salmon, mackerel and sardines, but lean fish such as cod, grouper, catfish and swordfish have lower amounts.
In addition to increasing the omega-3 levels in the lingcod, the OSU 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.