Using NMR technology to study the moisture changes of surimi products during storage

Using NMR technology to study the moisture changes of surimi products during storage

China is a large aquaculture country with abundant aquatic resources. The processing of fish into fish products is a way to effectively use marine resources. Surimi products are rich in protein, carbohydrates and high moisture. Poor storage conditions can lead to reduced quality and shorter shelf life.

NMR technology is a non-destructive and rapid monitoring method. It can study the water distribution and its state of fish gills storage process at the molecular level, and visually display the moisture and migration state of food. Nuclear magnetic resonance technology has been applied to many aspects of food processing and storage.

In the field of meat research, foreign countries have also used nuclear magnetic resonance technology to study the moisture in muscles in the early days.

The role of water and water migration during food storage is not only an important reason for the quality of products, but also important for the study of the mechanism of food preservation. One of the most important steps in the formation of surimi products is gelation. Through the unfolding of the α-helical structure of the tail of the myosin molecule and the interaction of the hydrophobic region, a bridge is formed inside the molecule to form a three-dimensional network structure, and the myosin has a very strong hydrophilicity and thus forms a network. The structure contains a large amount of free water, and due to the action of heat, the free water in the network structure is blocked from flowing in the mesh, thereby forming a gelatinous body having elasticity. This part of the water wrapped in the gel network structure undergoes great changes during storage.

Nuclear magnetic resonance test of different surimi products

The moisture at relaxation time T21 represents a single layer of water combined with an amino group such as a protein and a carbonyl group by hydrogen bonding. This water is very tightly combined and has poor fluidity.

This part of the water has the same moisture characteristics as the relaxation time T21, and the water has strong binding force and is tightly combined in the surimi product. However, the binding strength of T22 is slightly weaker than that of T21, which forms a small hydrogen bond with the amide group in the protein and the hydroxyl group in the starch cellulose. Its bonding strength is slightly worse than monolayer water.

Changes in relaxation time of different surimi products with storage time

References: “Using Nuclear Magnetic Resonance to Study Changes in Moisture in Fish Products During Storage”, Food Science 2011, Vol. 32, No. 19