Abstract:

The mechanism of protein denaturation during frozen storage can be revealed by the interaction between muscle
protein and water. In this study, the effect of storage temperature on protein denaturation in whiteleg shrimp (Litopenaeus
vannamei) muscle was examined in terms of protein structure and surface water molecules. The secondary structure and
deuteration kinetics of whiteleg shrimp muscle protein stored at −18 and −40 ℃ were analyzed by Raman spectroscopy and
H/D exchange method. The results showed that the secondary structure of protein molecules changed from tight to loose,
suggesting protein unfolding. Furthermore, the structure of protein stored at −18 ℃ was more loose than at −40 ℃. With
the unfolding of the protein secondary structure, the surface hydrophobicity of the protein increased, while the interaction
between protein and bound water was weakened. The higher the storage temperature was, the more intensely the interaction
was weakened, the less stable protein structure was and the more easily moisture loss occurred. In contrast, the lower the
frozen temperature was, the stronger the interaction between protein and water was. Consequently, protein structure was
more stable. The results showed that lower frozen storage temperature was more effective to maintain protein properties.

Key words: whiteleg shrimp (Litopenaeus vannamei), protein secondary structure, water, frozeng storage, Raman spectroscopy, deuterium