| Summary: | Heat treatment of cold water species is challenging due to quality changes occurring at low temperatures relative to most other foodstuffs. One of the characteristic challenges is the melting of connective tissue already below 40°C, causing disruption of the myotoma i.e. flaking of the fish muscle. One of the most heat sensitive fish species is Atlantic cod. Due to the relatively low fat content compared to other fish species, Atlantic cod easily loses its juiciness when the heat load causes cook loss or loss of ability to bind the inherent water (water holding capacity). In addition a tough texture is experienced after heat treatment at high temperatures. Farmed cod is known to lose its water holding capacity (WHC) earlier than wild cod during storage in raw condition. On the other hand, the market demand for Atlantic cod is high and farming is promising for regularity in delivery of cod and makes further processing profitable. The combination of the potentials for farmed cod and the challenges in heat processing has made the farmed Atlantic cod an interesting object to study. In this work, the quality of vacuum packaged, heat processed cod loins has been studied in order to find optimal combinations of processing time and temperature. A sample cup has been developed for rapid and homogenous heating and cooling of a fish sample with the possibility to measure cook loss, water holding capacity and texture without removing the sample from the cup. The sample cup and associated method have been used to characterise water holding capacity of the fish muscle at 156 combinations of temperature and processing time. The water holding capacity showed to decrease rapidly as soon as reaching the denaturation temperature of the proteins, but the correlation to temperature and processing time was complex and non-linear. The stepwise and partially overlapping denaturation of protein groups during heating is the major explanation for this behaviour and therefore the enthalpy changes during protein denaturation was ...
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