Effect of microbial transglutaminase on thermal and electrophoretic properties of ground beef

The effect of the different types of microbial transglutaminase (MTGase) preparations on denaturation temperature and SDS-polyacrylamide gel electrophoresis (SDS-PAGE) characteristics of myofibrillar proteins in ground beef was investigated. SDS-PAGE results showed that both MTGase preparations created cross-linking between meat proteins. The results of differential scanning calorimetry (DSC) indicated that addition of MTGase with sodium caseinate (SC) led to a slight increase in peak temperature (T_max) values of myosin. MTGase treatment caused a slight decrease in T_max values of myosin. Both MTGase and MTGase with SC treatments decreased denaturation enthalpy ($\mathrm{\Delta }{H}_{\mathrm{D}}$) of myosin but did not affect $\mathrm{\Delta }{H}_{\mathrm{D}}$ of actin. Enzyme concentration had a significant effect on $\mathrm{\Delta }{H}_{\mathrm{D}}$ values of myosin ($P<0.05$).     

Cryoprotective effect of soybean oil on surimi gels and the mechanism based on molecular dynamics simulation

The effect of soybean oil (SO) on freeze-thaw (F-T)-treated surimi was investigated and its related mechanism was revealed by molecular dynamics (MD) simulations. The results displayed that SO has a disrupting effect on the structure of fresh samples. However, in the F-T-treated samples, surimi gels supplemented with SO had a more uniform microstructure. Simultaneously, when SO was added from 0% to 7% in the F-T-treated samples, the gel strength increased from $46.66\text{to}51.86\mathrm{N}·\mathrm{mm}$ (p < .05), the physically bound water was increased from 92.90% to 94.15% (p < .05), and storage modulus was increased from 5939 to 6523 Pa. Triglycerides of SO generated hydrophobic interactions with myosin mainly in carbon chains. Computational results from MD simulations illustrated that the structure of myosin combined with triglycerides was more stable than that of myosin alone during temperature fluctuations (−20 to 4°C). During ice crystal growth, triglycerides absorbed on the myosin surface inhibited the growth of surrounding ice crystals and mitigated the ice crystal growth rate (from 7.54 to 5.99 cm/s). The addition of SO during the F-T treatments allowed myosin to be less negatively affected by ice crystal formation and temperature fluctuations and ultimately contributed to the formation of a more uniform network gel structure.