不同冻结方式对冷冻熟面品质的影响

Effect of Different Freezing Methods on Quality of Frozen Cooked Noodles

为研究冻结方式对冷冻熟面品质的影响,采用冰箱冻结、螺旋隧道冻结和液氮喷淋冻结三种冻结方式对熟面进行冻结,利用质构仪、核磁共振成像仪、流变仪、扫描电子显微镜分别测定熟面的质构性能、水分分布、流变特性及微观结构。结果表明,随着冻结温度的降低,冷冻熟面复煮后,干物质损失率减小,吸水率增加,液氮喷淋冻结处理熟面的干物质损失率最小(0.26%),吸水率最大(34.72%),面条的硬度、弹性、咀嚼性和最大拉伸距离最高。核磁共振结果显示,三种冻结方式均导致冷冻熟面的强结合水向弱结合水、自由水方向转化,而液氮喷淋冻结处理的A21峰面积占比(4.48%)高于螺旋隧道冻结(4.20%)和冰箱冻结组(2.03%),说明液氮喷淋冻结面条持水能力更好。流变学检测显示,液氮喷淋冻结处理的面条解冻后的储能模量(G′)和损耗模量(G″)最高,说明面条的黏弹性最大,此时扫描电镜下的面条横截面面筋网络结构均匀、致密,表面粗糙度最低。液氮喷淋冻结减小了冷冻熟面因冰晶造成的损伤,改善了冷冻熟面的品质。

In order to study the effect of freezing methods on the quality of frozen cooked noodles,three types of freezing methods,namely,spiral tunnel freezing method(SF),cryogenic refrigerator freezing method(RF)and liquid nitrogen spray freezing method(LF),were applied to frozen cooked noodles.The textural properties,moisture distribution,rheological properties and the surface microstructure were determined by texture analyzer,nuclear magnetic resonance imaging machine,rheometer and scanning electron microscope.The results showed that dry matter loss rate decreased but water absorption rate increased with the decrease of freezing temperature.Dry matter loss rate was the lowest(0.26%)but water absorption rate was the highest(34.72%)in liquid nitrogen spray freezing method group.Among the three freezing methods,the hardness,elasticity,chewability and maximum stretching distance of noodles were the highest after frozen by liquid nitrogen spray freezing method,while quality deterioration of frozen cooked noodles is the least.Nuclear magnetic resonance results showed that the three freezing methods all resulted in the transformation of strong binding water to weak binding water and free water;the proportion of T21 peak area in the liquid nitrogen spray freezing group(4.48%)was higher than that in the spiral tunnel freezing group(by 4.20%)and the refrigerator freezing group(by 2.03%),indicating that the liquid nitrogen spray freezing group had better water holding capacity.The rheological results showed that the storage modulus(G’)and loss modulus(G")of the frozen noodles treated with liquid nitrogen spray were the highest,indicating that the viscoelasticity of the noodles was the greatest.Under the scanning electron microscope,the crosssection of noodle gluten network was uniform and compact,and the surface roughness was the lowest.Liquid nitrogen spray freezing can reduce the damage caused by ice crystals and improve the quality of frozen cooked noodles.