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Lu H.,China Agricultural University | Liu X.,China Agricultural University | Zhang Y.,China Agricultural University | Wang H.,China Agricultural University | And 2 more authors.
Journal of food science | Year: 2015

To investigate the effects of chilling and partial freezing on rigor mortis changes in bighead carp (Aristichthys nobilis), pH, cathepsin B, cathepsin B+L activities, SDS-PAGE of sarcoplasmic and myofibrillar proteins, texture, and changes in microstructure of fillets at 4 °C and -3 °C were determined at 0, 2, 4, 8, 12, 24, 48, and 72 h after slaughter. The results indicated that pH of fillets (6.50 to 6.80) was appropriate for cathepsin function during the rigor mortis. For fillets that were chilled and partially frozen, the cathepsin activity in lysosome increased consistently during the first 12 h, followed by a decrease from the 12 to 24 h, which paralleled an increase in activity in heavy mitochondria, myofibrils and sarcoplasm. There was no significant difference in cathepsin activity in lysosomes between fillets at 4 °C and -3 °C (P > 0.05). Partially frozen fillets had greater cathepsin activity in heavy mitochondria than chilled samples from the 48 to 72 h. In addition, partially frozen fillets showed higher cathepsin activity in sarcoplasm and lower cathepsin activity in myofibrils compared with chilled fillets. Correspondingly, we observed degradation of α-actinin (105 kDa) by cathepsin L in chilled fillets and degradation of creatine kinase (41 kDa) by cathepsin B in partially frozen fillets during the rigor mortis. The decline of hardness for both fillets might be attributed to the accumulation of cathepsin in myofibrils from the 8 to 24 h. The lower cathepsin activity in myofibrils for fillets that were partially frozen might induce a more intact cytoskeletal structure than fillets that were chilled. © 2015 Institute of Food Technologists®


Du J.,China Agricutural University | Du J.,Bureau of Reclamation | Yang P.,China Agricutural University | Li Y.,China Agricutural University | And 4 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2011

Through the analysis of thet transport of N in the groundwater, ditch and soil profile during the period from the first-autumn irrigation to the second-autumn irrigation in Wulate irrigation region in Hetao Irrigation District Inner Mongolia, and the law of the agricultural non-point pollution production was analyzed so as to provide the corresponding theoretical guidance of the control of nitrogen pollution in Hetao Irrigation District. The study results shows that the accumulation of NO3 --N in the deeper soil profile (120-160 cm) was not significantly during the first-autumn irrigation period. The NO3 --N content were increased by 1.25, 2.72 and 2.89 mg/kg in the three farmland soil profiles (80~160 cm) respectively after the second-autumn irrigation period. The NH4 +-N distributions were relatively homogeneous from surface to deep of soil profile. The change law of the NO3 --N and NH4 +-N content in the three type soil profiles were increased or reduced seasonally. The content of NO3 --N and NH4 +-N in the groundwater in the second-autumn irrigation period were higher than that of the first-autumn irrigation period. The second-autumn irrigation period was the key stages which producted the agricultural non-point pollution in Hetao Irrigation District. The NO3 --N and NH4 +-N were accumulated in the soil profile of salt wasteland, which was helpful to reduced the amount of the agricultural non-point pollutant discharge.

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