Effect And Mechanism Of Different Slaughter Methods To Change Of Biochemical Property Of Tilapia Muscle

The effects of different stunning/killing procedures on flesh quality of Tilapiamuscle were investigated:（Ⅰ）bleeding followed by immersion in ice/water slurry for20minutes,（Ⅱ） immersion in ice/water slurry for20minutes,（Ⅲ） percussivestunning,（Ⅳ） percussive stunning followed by bleeding and immersion in water for20minutes,（Ⅴ） bleeding followed by immersion in water for20minutes,（Ⅵ）asphyxia in air for30minutes,（Ⅶ） electrical stunning with150V,50Hz,（Ⅷ）asphyxia in sealed box full of CO₂for30minutes. This paper study the effect ofdifferent slaughter methods to quality of tilapia muscle and biochemical property ofprotein in tilapia muscle.1. TVB-N and K value of eight groups were significantly increased with theextension of storage period during iced storage. TVB-N and K value increase moreslowly from0day to6day. The speed of TVB-N and K value increased becomes.quickly than before. TVB-N value of Ⅱ andⅢ are significantly less than other groups.TVB-N value of Ⅵ, Ⅶ andⅧ are significantly grater than two groups of Ⅱa ndⅢ.And TVB-N value of Ⅶ group increase rapidly than other groups. There are nosignificant difference of K value within groups of Ⅴ, Ⅵ and Ⅶ. But the K value ofⅦ group is significantly higher than other five group. The groups of Ⅰ, Ⅱ, Ⅲgoing into the secondary frehness are later than other groups. Group of Ⅶ up to thestate of secondary phase and corruption is ealier than others.The content of ATP inGroups of Ⅲ and Ⅳ are the highest, secondly is Ⅶ group. ATP content in groupsof Ⅵ and Ⅷ is lowest.2. Through shtudy of physical indicators of tilapia quality during iced stor-age,followed conclutions were found.With the storage time extension, the whiteness values （L*-value） red degrees （a*）,yellow degree （value b*） of fish fillet gradually increase;Hardness, gumminess and chewiness of fillet decreased gradually. Change of cohesivenness and springiness wasnot significant during iced storage. The water holding capacity （WHC） of fish fillet isfalling, which increase water loss.L*-values are significantly higher and a*-values are significantly lower ingroups of Ⅰ, Ⅳ and Ⅴ than that in other groups. Effect of bleeding on Lightness andreddness of fillet is obvious. The fillets of groups of Ⅵ and Ⅷbecome more yellowthan other groups during iced storage.The hardness, chewiness and gumminess of fillet in group Ⅰ, Ⅱ, Ⅲ, Ⅳ andⅤhave a slightly increased at days2, then decreased. But hardness, chewiness andgumminess of fillet in groupⅥ,Ⅶ and Ⅷ decreased straight. This different may beassociated with the starting time of rigid. Hardness of fillet in group of Ⅵ,Ⅶ andⅧ decreased rapidly. We can concluted that these three slaugter methods make fishfillet more soft than other methods. In fresh fish fillets, WHC in Ⅶ groupis lowest,followed by group Ⅵ andⅧ. These three groups loss more water than other groupsduring iced storage.3. Glycogen content is significantly higher in groups of Ⅵa ndⅧ than othergroups. followed by groupsⅠ, Ⅱ and Ⅴ, glycogen content islowest in group of Ⅵand Ⅷ group. lactic acid content is significantly higher in Ⅵ andⅧ than other groupsbut lowest in groups of Ⅲ and Ⅳ in fresh fish fillets. Lactic acid accumulatesgradually after the death of fish, began to decline after reaching the maximum.Actomyosin salt-solubility of fillets is significantly reduced during iced storage.SH content of Tilapia fillet is declining straight. Actomyosin salt-solubility in groupsofⅡand Ⅲis highest. Actomyosin salt-solubility in groups of Ⅴand Ⅵ is obviouslylower than the other groups. SH content in groups of Ⅱ,Ⅲ andⅣis significantlyhigher than that in groupsⅤ, Ⅵ and Ⅷ.Ca²⁺-ATPase activity, Mg²⁺-ATPase activity and Ca²⁺-Mg²⁺-ATPaseactivity are decreased significantl the extension of storagetime. Ca²⁺-ATPaseactivity was significantly higher in groups of Ⅲ andⅣ than that in groups of Ⅵ andⅧ （P <0.05） from days0to days8. Mg²⁺-ATPase activity in group Ⅲissignificantly higher than that in other groups at days2and days4. Mg²⁺-ATPase activity in group Ⅶ is significantly lower than other groups at days6,8, and10. Ca2+-Mg²⁺-ATPase activity is significantly lower in groups of Ⅵ, Ⅶ andⅧ than thatin groups of Ⅱ, Ⅲ andⅣ （P <0.05）.UMP content begains to decrease after increasing in five groups of Ⅰ, Ⅱ, Ⅲ, Ⅳand Ⅴ. UMP content is up to maximum in groups of Ⅲ, Ⅳ and Ⅴ at days2. AndUMP content reaches the maximum in groups ofⅠand Ⅱat days4. But UMPcontent is decreased straight in groups of Ⅵ, Ⅶ and Ⅷ.GMP content of eight groupsis increased first then decresed during Iced storage time. CMP content is significantlyhigher in groups of Ⅴ andⅥ than other groups at days0. CMP content issignificantly lower in groups of Ⅰ, Ⅱ and Ⅲ than that in other groups. Change ofIMP content is similar with GMP, increased in two days and then declined. AMPcontent is significant decreased during iced storage.4. Eight kinds of slaughter methods are studied in this paper. Stress reaction offish in groups of Ⅱ and Ⅲ is not severe, but it is most severe in groups of Ⅵ and Ⅷ.Fierce struggle when slaughtered increased the extent of protein degeneration of fish.This change increase the chance of protein getting in touch with proteolytic enzymewhich makes the fish fresh getting soft quickly, salt soluble protein becoming cuttingdown, ATPase activity declining, protein degradation accelerated. These changes arebad for hardness, chewiness and gumminess such as structure parameters. And thesechanges are related to the increase of TVB-N value and K value. These change resultin the loss of water and effect many kinds of biochemical criterions. Thereforbiochemical properties and quality of fish fresh of group Ⅱ and group Ⅲ aresignificant superior to group Ⅵ and group Ⅷ. In group Ⅶ whit electrical stunningfish having less stress reaction, but electricity make fish muscle softer which resultingthe quality of fish fresh deteriorated.