Study on the preservation of agricultural products by means of hydrophobic hydration

抑制代谢在农产品保鲜中起着重要作用。代谢是基于细胞内的化学反应，这在很大程度上是酶介导的。由于底物的扩散调节酶反应速率，底物扩散速率的降低可能导致代谢的抑制。当细胞中的水变得“结构化”时，水的粘度增加，底物的扩散速率降低。因此，可以认为抑制代谢的方法是使细胞内水结构化。在此基础上，本研究设计了一种通过结构水的形成来控制细胞内水状态的保存方法，当非极性气体溶解在水中时，通过疏水水合作用产生氢键水分子的数量增加，水变得结构化。在产生疏水水合的许多非极性气体中，惰性气体是最合适的，因为它们预计不会引起细胞中的化学变化。选择氙气是因为与其他惰性气体相比，氙气形成结构水的程度更大。通过NMR实验证实了氙的溶解引起的氢键水分子数量的增加。质子化学位移表明，与不含氙的水相比，氙溶液的质子化学位移更大。在给定的氙气压力下保存过程中测得的西兰花和茄子的CO2的浓度和数量明显小于那些保存在气密条件下，在相同的温度。结果支持了所提出的保存方法的有效性。

The suppression of metabolism plays an important role in keeping agricultural products fresh. Metabolism is based on intracellular chemical reactions which are, for the most part, enzyme mediated. As the diffusion of substrate regulates the enzyme reaction rate, the decrease in the diffusion rate of substrate may lead to the suppression of metabolism. When the water in a cell becomes "structured", the viscosity of water increases and the diffusion rate of substrates desreases. Hence, a way for suppression of metabolism can be thought to make intracellular water structured. On this basis, the present study was designed to develop a preservation method that controls the state of intracellular water by means of the formation of structured water.When nonpolar gas dissolves in water, the number of hydrogen-bonded water molecules increases by creation of hydrophobic hydration and the water becomes structured. Among many nonpolar gases that create hydrophobic hydration, inert gases are most suitable since they are expected not to cause chemical changes in cells. Xenon was selected because of the greater degree of structured water formation with xenon compared to other inert gases. The increase of the number of hydrogen-bonded water molecules caused by the dissolution of xenon was confirmed by the NMR experiment. The proton chemical shift indicated the greater chemical shift for the xenon solution compared to the water without xenon.The method was applied to the preservation of broccoli and eggplant. The concentration and quantity of CO2 measured for the broccoli and eggplant during preservation under given pressure of xenon were distinctly smaller compared to those preserved in an air-tight condition at the same temperature. The results supported the validity of the proposed preservation method.