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Structural changes in squid ( Loligo japonica ) collagen after modification by formaldehyde
Author(s) -
Fu Xueyan,
Xue Changhu,
Jiang Lina,
Miao Benchun,
Li Zhaojie,
Xue Yong
Publication year - 2008
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.3387
Subject(s) - chemistry , differential scanning calorimetry , squid , hydroxyproline , alanine , proline , isoleucine , random coil , circular dichroism , leucine , biochemistry , amino acid , biology , ecology , physics , thermodynamics
BACKGROUND: Formaldehyde (FA) has been suggested to cause changes in texture and functional properties in some marine species. It was therefore hypothesised that FA may affect collagen, a fundamental constituent of the extracellular matrix in squid. RESULTS: Two types of collagen, I and V, were isolated by pepsin digestion and differential salt precipitation. Type V collagen contained higher proportions of isoleucine, leucine, and lysine and lower proportions of alanine and hydroxyproline. The effects of FA on pepsin‐solubilised squid collagen were examined by differential scanning calorimetry and Raman spectroscopy. The squid collagen showed a transition temperature ( T m1 ) of 37.2 ± 0.2 °C, which was significantly reduced in the presence of 2 and 10 mmol L −1 FA. In the presence of 1, 2 and 10 mmol L −1 FA an additional peak ( T m2 ) was also observed at 77.7 ± 0.1, 78.4 ± 0.1 and 62.7 ± 0.2 °C respectively, suggesting FA–collagen interactions. Treatment with 2 mmol L −1 FA increased the I 940 / I 1005 ratio from 1.09 to 1.66 and shifted the 990 and 1245 cm −1 bands. The tyrosine doublet ratio ( I 850 / I 830 ) was also increased about threefold, suggesting that α helix, β sheet type and random coil structures were changed by FA. CONCLUSION: The secondary structure of squid collagen can be affected by FA through hydrophobic interactions. Copyright © 2008 Society of Chemical Industry