冻藏对馒头水分状态以及品质影响研究

Effect of Frozen Storage on Moisture Status and Quality of Steamed Bread

馒头在冻藏过程中出现硬度增大、比容变小等品质劣变现象,通过研究其在冻藏过程中的水分变化,可以为改善速冻馒头品质提供理论基础。通过差示扫描量热仪(differential scanning calorimeter,DSC)、低场核磁共振(low field-nuclear magnetic resonance,LF-NMR)及质构仪等研究冻藏以及复蒸过程中馒头可冻结水含量、水分状态、质构和比容等品质特性的变化,并对馒头水分变化与质构特性之间的关系进行了相关性分析。结果表明,冻藏以及复蒸过程中馒头的水分含量均显著降低;冻藏60 d时,馒头的失水率达1.19%,可冻结水的融化焓△H增加了6.32 J/g;冻藏过程中半结合水变得更易流动且含量有所降低。并且,冻藏馒头以及复蒸馒头的比容显著降低(P<0.05),硬度与咀嚼性显著增大(P<0.05)。失水率与冻藏馒头的硬度和咀嚼性呈显著正相关,可冻结水含量与复蒸馒头的硬度和咀嚼性呈显著正相关。

In the process of frozen storage,the quality of steamed bread was deteriorated,such as the increased hardness and the decreased specific volume. Through investigation of the bread moisture change during freezing process,it can provide the theoretical basis for improving the quality of fast-frozen steamed bread. The changes of freezable water content,moisture status,texture and specific volume of steamed bread during freezing and re-steaming were studied by differential scanning calorimeter (DSC),low field-nuclear magnetic resonance (LF-NMR)and texture analyzer,and the correlation between moisture change and texture characteristics of steamed bread was analyzed. These results showed that the moisture content of steamed bread was significantly reduced during freezing and re-steaming. After 60 days of freezing,the water loss rate of steamed bread reached 1.19 %,and the melting enthalpy of the freezable water increased by 6.32 J/g. During the process of frozen storage,the semi-bound water became much easier to flow and its content slightly decreased. In addition,the specific volume of frozen and steamed bread were significantly reduced (P <0.05)and the hardness and chewiness were significantly increased(P<0.05). The water loss rate was positively correlated with the hardness and chewiness of frozen steamed bread,and the content of freezable water was positively correlated with the hardness and chewiness of re-steamed bread.