Because of the composition and structural
complexity of crustacean
shells, their color change mechanism during thermal processing remains
unclear. This study identified and characterized two intrinsic protein
components, hemocyanin (Lv-Hc) and β-1,3-glucan-binding protein
(Lv-BGBP) from Litopenaeus vannamei shrimp shells by a combination of ion-exchange chromatography, gel
filtration, and mass spectrometry. It was found that a mixture of
Lv-Hc, a gray protein, and Lv-BGBP (which is a natural astaxanthin-binding
protein with a red color) is responsible for the brown color of fresh
shrimp shells. Upon heating to 100 °C, the mixture of these proteins
turned red, mimicking the color change observed in cooked shrimp shells.
This transition is attributed to the extremely high thermal stability
of Lv-BGBP, which has the ability to protect astaxanthin from thermal
induced degradation. These findings provide significant insights into
the molecular mechanism governing shrimp shell coloration, advancing
our understanding of crustacean biochemistry.