Changes on enzymatic activity and on sarcoplasmic and myofibrillar proteins of frozen-stored hake (Merluccius merluccius) pre-treated by high pressure

High-pressure (HP) pre-treatments were applied on European hake (Merluccius merluccius) followed by a frozen accelerated experiment (-10 degrees C). A central composite design ranging pressure levels (150-450 MPa) and frozen storage time (0-150 days) was used, being evaluated the enzymatic activities and muscle proteins. Acid phosphatase and calpain activities decreased after 150 days of frozen storage (58%/56% and 38%/56% for non-/HP-treated samples, respectively). Cathepsin B showed higher reductions (98%) for longer storage times. Furthermore, HP and frozen storage did not affect significantly cathepsin D activity, only slightly decreasing at 169 MPa. Furthermore, HP seemed to not affect myofibrillar proteins, while sarcoplasmic proteins were clearly affected by HP and frozen storage time, resulting in a reduction of about 53% or 23% for 431 or 450 MPa, respectively. Thus, HP could be used to lowering the deleterious effect of proteases on frozen European hake.