Evaluation of the Relationship between Freezing Rate and Quality Characteristics to Establish a New Standard for the Rapid Freezing of Pork.

This study evaluated the effect of freezing rate on the quality characteristics of pork loin to establish an objective standard for rapid freezing. To generate various freezing rates, three air flow rates (0, 1.5, and 3.0 m/s) were applied under three freezing temperatures (-20°C, -30°C, and -40°C). Based on the results, freezing rates ranged from 0.26-1.42 cm/h and were graded by three categories, i.e, slow (category I, >0.4 cm/h), intermediate (category II, 0.6-0.7 cm/h) and rapid freezing (category III, >0.96 cm/h). Both temperature and the air flow rate influenced the freezing rate, and the freezing rate affected the ice crystal size and shear force in pork loin. However, the air flow rate did not affect thawing loss, drip loss or the color of pork loins. In the comparison of freezing rates, pork belonging to category II did not show a clear difference in quality parameters from pork in category I. Furthermore, pork in category III showed fresh meat-like qualities, and the quality characteristics were clearly distinct from those of category I. Although the current standard for rapid freezing rate is 0.5 cm/h, this study suggested that 0.96 cm/h is the lowest freezing rate for achieving meat quality distinguishable from that achieved with conventional freezing, and further increasing the freezing rate did not provide advantages from an energy consumption perspective.

Advanced Tenderization of Brine Injected Pork Loin as Affected by Ionic Strength and High Pressure.

This study investigated the effects of brine injection and high hydrostatic pressure (HHP) on the quality characteristics of pork loin. Brine with ionic strength conditions (0.7% vs 1.5% NaCl, w/v) were injected into pork loins, and the meat was pressurized up to 500 MPa for 3 min. As a quality indicator, moisture content, color, cooking loss and texture profile analysis (TPA) of pork loins were estimated. Based on the results, brine with low ionic strength (0.7% NaCl) resulted in low injection efficiency and high cooking loss, although, it improved tenderness of pork loin at moderate pressure level (~200 MPa). While high ionic strength condition (1.5% NaCl injection) lowered the hardness of pork loins at relatively high HHP level (400-500 MPa), it also caused high cooking loss. To commercialize the brine injected pork loins, it was necessary to regulate brine compositions, which was not evaluated in this study. Nevertheless, the present study demonstrated that brine injection followed by moderate pressure (200 MPa) could improve the tenderness of pork loins without causing other major quality losses.

Reduced sirtuin 1/adenosine monophosphate-activated protein kinase in amyotrophic lateral sclerosis patient-derived mesenchymal stem cells can be restored by resveratrol.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting motor neuron system. Our previous study has shown that bone marrow-mesenchymal stem cells (BM-MSCs) from ALS patients have functional limitations in releasing neurotrophic factors and exhibit the senescence phenotype. In this study, we examined sirtuin 1/adenosine monophosphate-activated protein kinase (SIRT1/AMPK) activities and identified significant decreases in the ALS-MSCs compared with normal healthy control originated BM-MSCs. This decline was restored by pretreatment with resveratrol (RSV), measured using quantitative polymerase chain reaction, NAD/NADH assay, and immunoblot analysis. Neuroprogenitor markers were increased in RSV-treated ALS-MSCs (RSV/ALS-MSCs). The differentiated ALS-MSCs (ALS-dMSCs) exhibited a cell body and dendritic shape similar to neurons. RSV/ALS-MSCs showed significantly increased differentiation rate as compared with the untreated ALS-dMSCs. The neurite numbers and lengths were also significantly increased. This was confirmed with immunoblot analysis using neuron specific markers such as nestin, NF-M, Tuj-1, and Map-2 in RSV/ALS-dMSCs. Thus, this study shows that ALS-MSCs showed down-regulation of AMPK/SIRT1 signalling, which was recovered by treatment with RSV. This data suggest that RSV can be one of the candidate agents for improving therapeutic efficacy of ALS patients' originated MSCs.

Pressure Induced Structural Changes of Proteins Affecting the Ice Nucleation Temperature of Pork Loins.

This study investigated the effects of pressure-mediated protein changes on the ice nucleation temperature of pork loins. To variate chemical state of meat proteins, pork loin was pressurized at varying pressure levels (100-500 MPa) for 3 min, and moisture content, expressible moisture (EM) and differential scanning calorimetry (DSC) were analyzed. Although, all treatments showed similar moisture content, EM and degree of protein unfolding of pork loin showed different features as of 300 MPa. At moderate pressure treatments (100-200 MPa), all protein fractions were detected in DSC experiments, and pork loin had lower EM than control (p<0.05). Meanwhile, myosin and actin of pork loin treated at greater than 300 MPa were completely unfolded, and the treatments showed high EM compared to control (p<0.05). Unfolding of meat proteins was a factor suppressing ice nucleation, and the ice nucleation temperature tended to decrease with increasing applied pressure level. The ice nucleation characteristics of pressurized pork loin exhibited a potential application in freezing storage of pressurized meat with less tissue damage comparing to freeze fresh meat, and further exploration regarding the quality change after freezing of fresh and pressurized meat was warranted.