ABSTRACT
Superchilling is an emerging technology for meat preservation; however, the temperature changes during the process have been commonly ignored. Thus, the effects of temperature fluctuations on meat quality during superchilling are yet to be evaluated. In our study, pork loins and salmon fillets were stored for several days (0, 8, 15, 23, and 30 d) under different temperature fluctuations based on -3.5 ℃ as the target temperature. The results showed that after 15 d of superchilling storage, the values of total volatile basic nitrogen, total viable count, and lipid oxidation were significantly (P<0.05) altered in the ±2.0 ℃ fluctuation group compared with the constant temperature group. On the contrary, there was no significant difference in these parameters between the ±1.0 ℃ fluctuation group and the constant temperature group after 30 d of storage. In addition, irregular temperature changes significantly accelerated the modulation of various indicators. In brief, temperature fluctuations and irregular temperature changes accelerated the destruction of muscle structural integrity, increased the water loss, gradually widened the water loss channels, and thereby reduced the edibility by accelerating the spoilage of meat.
Subject(s)
Animals , Lipid Metabolism , Pork Meat , Red Meat , Salmon , Swine , TemperatureABSTRACT
OBJECTIVE To study the cytotoxicity of polyamide amine dendrimers (PAMAM)-hyaluronic acid(HA)as a non-viral gene delivery vector in vitro. METHODS PAMAM-HA was synthesized by our laboratory. Cytotoxicities of various polymers on HeLa cells,Bel-7402 cells and HepG2 cells were evaluated by MTT assay. Apoptotic rates were determined by flow cytometry. RESULTS The cytotoxicity of PAMAM-HA polymer increased with the concentration of polymer(50-800 mg · L-1),the time of action(24-72 h), the number of generations of PAMAM(G4,G5) and decrease in the molecular mass(3850,17 200)and the graft density(5%-25%)of HA. After incubation with PAMAM G4-HA3850-5%or PAMAM G5-HA3850-5%for 24 h,the apoptotic rate of hepatoma cells—Bel-7402 cells was 4.5%and 9.9%,respectively. After incubation with complexes of PAMAM G4-HA3850-5%/DNA or PAMAM G5-HA3850-5%/DNA for 24 h,the viability of HeLa cells was more than 80%,which was lower than that of PAMAM G4/DNA和PAMAM G5/DNA. CONCLUSION Cytotoxicity of PAMAM modified by HA of different grafting density and quantity can be reduced ,suggesting the PAMAM is a promising non-viral gene vector.