不同盐水注射量下西式火腿真空预冷过程中水分存在形式及孔隙结构变化规律

Effect of Vacuum Precooling on Water Mobility and Pore Structure of Cooked Pork Ham Injected with Different Levels of Brine Solution

真空预冷技术在低温熟肉制品的降温方面扮演着极其重要的角色。本实验以真空预冷前后不同盐水注射量(质量分数10%、20%、30%、40%)下的西式火腿水分存在形式和孔隙结构参数为研究对象,并利用偏最小二乘回归分析探讨真空预冷的降温机理。结果表明,10%盐水注射量样品整体平均降温速率(0.94℃/min)显著高于20%(0.76℃/min)、40%(0.68℃/min)和30%(0.56℃/min)盐水注射量样品(P<0.05)。真空预冷过程中不同盐水注射量样品的结合水、束缚水和自由水弛豫峰面积均呈下降趋势,但束缚水驰豫时间却始终维持不变。真空预冷可使不同盐水注射量的样品均获得更宽范围的孔径分布、更大的孔隙率和平均孔径等。载荷图分析结果显示,真空预冷过程中各降温段平均速率与孔隙结构和水分存在形式中的部分参数(束缚水弛豫时间和弛豫面积、累计孔隙体积和累计孔面积、平均孔径及孔曲率和渗透率等)存在着极强的相关性。变量重要性投影值分析结果表明,束缚水较自由水、结合水对降温速率的影响更大。此外,平均孔径、渗透率和孔曲率等孔隙结构指标要比单纯的孔隙率指标对降温速率影响更明显。

Vacuum precooling technology can play an important role in the cooling of low-temperature cooked meat by virtue of its fast cooling rate.In this study,the effect of vacuum precooling on the water mobility and pore structure of cooked pork ham injected with different levels(10%,20%,30%and 40%)of brine solution was evaluated,and in turn the effects of the water mobility and pore structure on the cooling rate were discussed using partial least squares regression(PLSR).The results showed that samples injected with 10%brine solution had a higher average cooling rate(0.94℃/min)compared to those injected with 20%(0.76℃/min),30%(0.56℃/min)and 40%(0.68℃/min)brine solution during vacuum precooling(P<0.05).The nuclear magnetic resonance(NMR)results showed that the relaxation peak areas of bound water(A_(21) and A_(22)),immobile water(A_(23))and free water(A_(24) and A_(25))in all samples exhibited a decrease during vacuum cooling while the relaxation time of immobile water(T_(23))remained unchanged.In addition,vacuum precooling produced a wider range of pore size distribution,higher porosity and larger apertures than did the conventional precooling method.The loading plot showed that the average cooling rate exhibited a significant correlation with the transverse relaxation time and peak area of immobile water,cumulative pore volume and area,average pore diameter,tortuosity and permeability.The variable importance in projection(VIP)results revealed that immobile water exhibited a more significant effect on the average cooling rate compared to bound water and free water.In addition,the pore structure parameters average pore diameter,permeability and tortuosity more significantly affected the average cooling rate compared to the porosity determined by mercury porosimetry.