The study, published in Food Chemistry, found fish oil added to an invisible "food wrap" made from citosan -- a substance found in crustacean shells that keeps out bacteria and fungi -- not only kept lingcod fillets fresh in the refrigerator for three weeks and in the freezer three months but also tripled the amount the omega-3 fatty acids normally found in lingcod.
The coating, which does not affect the color of the fish, also reduced rancidity both refrigerated and frozen samples when compared with the uncoated fillets and also kept the frozen fish moister. It delayed the growth of microorganisms in the fresh fillets, and it prevented their growth in the frozen ones.
"With this coating, you can easily keep the fillets in the display case for two to three more days," study leader Yanyun Zhao of Oregon State University, in Corvallis, Ore., said in a statement.
Zhao said research indicates many health benefits including lowered heart disease risk linked to increased omega-3 fatty acids in the diet. While oily fish like salmon, mackerel and sardines are rich in omega-3 fatty acids, leaner fish such as cod, grouper and swordfish contain much less.