Mortensen Margit, Thybo Anette K, Bertram Hanne C, Andersen Henrik J, Engelsen Søren B
Department of Food Science, Danish Institute of Agricultural Sciences, P.O. Box 102, DK-5792 Aarslev, Denmark.
J Agric Food Chem. 2005 Jul 27;53(15):5976-81. doi: 10.1021/jf0479214.
Continuous low-field (LF) (1)H NMR relaxometry was used to monitor the structural changes during cooking of potatoes with two different dry matter (DM) contents. A principal component analysis of the relaxation decay curves revealed major events related to water mobility during cooking, which occur at 53 and 60 degrees C for potatoes with medium and low DM contents, respectively. Exponential analysis of the relaxation decays reveals two major water populations in the potato: a slow-relaxing (assigned to water in cytoplasm and extracellular cavities) water component, T(22) ( approximately 350-550 ms), and a fast-relaxing component (primarily assigned to water associated with starch and cell walls), T(21) ( approximately 45-65 ms). Significant DM dependent shifts in both the T(21) and T(22) relaxation time constants were observed during cooking, indicating that starch gelatinizes between 53 and 70 degrees C with water exchanging with the hydroxyls of starch (transition in T(21)) and cells start to disrupt with an increase in diffusion volumes at approximately 60 degrees C (transition in T(22)). The study reveals that continuous LF NMR measurement is an excellent and highly sensitive method to study changes in water mobility and water populations during the cooking of potatoes.
采用连续低场（LF）（1）H核磁共振弛豫测量法监测两种不同干物质（DM）含量土豆烹饪过程中的结构变化。对弛豫衰减曲线进行主成分分析，揭示了烹饪过程中与水分流动性相关的主要事件，中等DM含量的土豆在53℃时出现，低DM含量的土豆在60℃时出现。对弛豫衰减进行指数分析，发现土豆中有两种主要的水分群体：一种弛豫缓慢的（归因于细胞质和细胞外腔中的水）水分成分，T（22）（约350 - 550毫秒），以及一种弛豫快速的成分（主要归因于与淀粉和细胞壁结合的水），T（21）（约45 - 65毫秒）。在烹饪过程中观察到T（21）和T（22）弛豫时间常数均有显著的DM依赖性变化，表明淀粉在53至70℃之间发生糊化，水与淀粉的羟基发生交换（T（21）转变），细胞在约60℃时开始破裂，扩散体积增加（T（22）转变）。该研究表明，连续低场核磁共振测量是研究土豆烹饪过程中水分流动性和水分群体变化的一种优秀且高度灵敏的方法。
