Study on different chilling factors influencing water-holding capacity of pork based on low-field nuclear magnetic resonance (LF-NMR)

Obtaining water distribution information can help explain the water-holding capacity of pork. This study investigated water distribution and mobility of M. longissimus dorsi from 32 Duroc×Landrace×Large white pigs under different chilling methods by using low-field nuclear magnetic resonance (LF-NMR). Multi-exponential fitting of the bulk NMR T2 transverse relaxation time data demonstrated that four distinct water populations were T20 (150-500 μs), T21 (1-3 ms), T22(40-50 ms) and T23(150-400 ms). Significant correlation was found between T22, T23 time constant and drip loss, and between T22, T23 time constant and cooking loss (P<0.01), respectively. The strongest correlation was found between pT23 and drip loss (r=0.858). Initial increase and following decrease were observed in the immobilized water (pT22) during the chilling period, but free water (pT23) showed minor decrease followed by moderate increase. Compared with conventional chilling, rapid chilling method resulted in reducing weight loss by 0.3%, and treatment of increasing humidity reduced weight loss by 0.5%. The NMR images showed more free water on the surface of muscle samples in the treatment of relative humidity 95% than the treatment of relative humidity 80%. The results are instructive and meaningful to optimizing chilling parameters in slaughter industry.