Various factors can be grouped into a determinant of freshness: the type and size of the fish, the environment and how to catch or harvest. Thus, to get fresh fish, three of these factors need to be considered. Affect the freshness of fish, both during harvesting or catching or during storage. By the time the fish are harvested or caught it difficult to distinguish freshness.
Another case when the fish have died or saved a few moments later. This type of fish, size and gender will affect the quality of the fish. Pelagic fish which have high activity relatively easy to experience the process of degradation of quality compared to the low activity of demersal fish. Similarly, fish stress, marriage or a new activity being attempted. Fish activity associated with glycogen content available at the time the fish are harvested or captured. The dead fish containing low glokogen not able to lower the pH of the meat so kesegaranya rapidly declined.
Fish with high fat content are also more prone to the process of degradation of quality compared to fish with a low fat content. Fatty fish are no long-chain saturated and thus susceptible to oxidation during storage. As a result of the oxidation of fats, fish become rancid. Thus, fish with high fat content is decreased freshness. The size of fish plays an important role in
determining the freshness of fishery products. Large fish are better able to maintain the freshness of the fish compared to similar size smaller. This is understandable because in the same weight, the big fish have body surface area relatively smaller than the fish that small body size. Thus, the contact area between the small fish with freshness reduction factor (such as temperature and microbial) becomes larger.
Microbial penetration into the meat of a big fish takes longer than the penetration of the small fish. Fish size also affects the speed of the process of weeding fish. Big fish more easily weeded out while the time and labor required for weeding small fish more, so that small fish are generally not weeded but only washed with clean water. The pH value of big fish mortality is relatively lower than the small fish.
Gender affects the chemical composition of the flesh of the fish. Female fish freshness is often decreased faster than the male fish. Condition new female fish mating activity is relatively weak because so many expend energy during storage will decrease the freshness faster than females who do not perform activities of marriage.
Red-fleshed fish species including tuna, is usually a process of bleaching the color of the skin caused by polyphosphatase enzyme activity in the skin is also influenced sunlight and oxygen from the air. During storage the yellow fin meat is usually quickly turns brown due to oxidation enzyme system having more robust than other tuna species. This can be overcome by freezing tuna quickly after the fish are caught at a temperature of -60 ° C and store at temperatures below -40 ° C. In addition, the meat is frozen yellow fin tuna usually show a dark or brownish color caused by the change of the original properties of blood.