Partial inhibition of cholesterol oxides formation in frozen fish pre‐treated with a plant extract

Summary The formation of cholesterol oxide products (COPs) in frozen horse mackerel (Trachurus trachurus) fillets was studied. The effect of pre‐treating the fish by soaking (45 min) in either of two concentrations of the aqueous solution of an antioxidant plant extract prior to the freezing step was determined. The fish fillets were sampled immediately after freezing and at intervals along 12 months of frozen storage (−20 °C). Two control groups consisting of untreated and water‐treated fish were stored and sampled under the same conditions. During the experiment, qualitative analysis revealed the formation of the following COPs: 7α‐hydroxy‐cholesterol, 7β‐hydroxy‐cholesterol and 7‐keto‐cholesterol. All treatment groups showed an increase (P < 0.05) in the content of all three COPs with storage time. As a result of pre‐freezing antioxidant treatment, COPs formation was reduced (P < 0.05) in comparison with both control samples. This partial inhibition was consistent with a longer shelf‐life time as revealed by sensory analysis.