Visualization of food hydration structure and analysis of molecular mobility to elucidate the hydration state implied by water activity

2019 Fiscal Year Final Research Report

• Project/Area Number: 16H04928
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Food science
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: Nakagawa Hiroshi 国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 原子力科学研究所 物質科学研究センター, 研究副主幹 (20379598)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 水分活性 / 食品物理学 / ガラス転移 / 中性子散乱 / 水和

Outline of Final Research Achievements

By analyzing the molecular mobility of water molecule and visualizing the hydration structure using quasi-elastic neutron scattering, we investigated the physicochemical state of water in food and the interaction between food and water, and elucidated a part of the hydration state implied by water activity. Specifically, although water activity has been described in qualitative terms such as free water and bound water, it was shown that each state can be distinguished as a difference in the network structure of hydration water via hydrogen bonding. Each state was also quantitatively explained by the diffusion coefficient of water and the hydrogen bonding lifetime. Furthermore, we found that the change in hydration state was closely related to the presence or absence of a glass transition in the food molecules. On the other hand, the relationship with the food microstructure was also found to be important for a unified understanding of the water activity of foods.

Free Research Field

食品物理学

Academic Significance and Societal Importance of the Research Achievements

水分活性は食品の保存性や品質を評価する実用的な指標であり、その有効性は広く認められており、食品加工などの現場で既に利活用されている。しかしながら、水分活性がなぜそのように食品の状態をうまく指標化できているのかなどについての学術的な観点からの研究は不十分な点が多い。本研究で解明した水分活性が意味する食品の水和状態を参照することによって、これまでと違った観点から水分活性の利用ができたり、食品の品質についてこれまで以上情報が引き出せたりできるようになる可能性を秘めている。