Type II collagen derived from chicken cartilage has been extensively characterized and documented in literature. Recently, salmon cartilage has gained attention as a potential substitute for chicken cartilage (1). However, salmon type II collagen exhibits a lower denaturation temperature (lower than 35°C) compared with chicken type II collagen (42°C), resulting in a higher proportion of denatured type II collagen in salmon cartilage. Therefore, native type II collagen content in salmon cartilage may vary in samples depending on cartilage preparation, transportation, and storage conditions. Recently, Chondrex, Inc. analyzed some salmon cartilage samples obtained in Japan to determine their native type II collagen content.
1. Native type II collagen ELISA analysis using Cat # 6018
Samples were prepared and analyzed according to the standard protocol for undenatured type II collagen (UC-II) as provided by Chondrex, Inc.
Table 1. Quantification of Native Type II Collagen in Salmon Samples by ELISA
Sample Wet Weight (mg) | 1657 |
Sample Dried Weight (mg) *Note 1 | 124.2 |
Dried sample used (mg) | 14.2 |
Final extracted volume (ml) | 8 |
Native Collagen II (μg/ml extract) * Note 2 | 102.6 |
Total Native Collagen II in extract (μg) | 820.8 |
Native Collagen II Ratio (μg/mg dried sample) | 57.8 (5.8%) |
Note 1. The dry weight of salmon cartilage corresponds to 7.5% of its wet weight (124.2 mg per 1657 mg), indicating a higher moisture content compared with chicken cartilage, which typically contains 25–35% moisture.
Note 2. The type II collagen ELISA (Cat # 6018) demonstrated 65.5% cross-reactivity with salmon type II collagen relative to the chicken type II collagen standard. Accordingly, the ELISA-derived concentrations of salmon type II collagen were corrected using a conversion factor of 100/65.5.
2. Hydroxyproline (HP) total collagen analysis using Cat # 6017
Table 2. Quantification of Total Collagen in Salmon Samples by HP Assay
Dried Sample (mg) | HP (μg/ml) | Volume (ml) | HP (ug/mg sample) | Total Collagen (μg/mg sample) | % of collagen |
5.4 | 1230.1 | 0.1 | 22.8 | 169 | 16.9 |
Note: 13.5% hydroxyproline (HP) in collagen
3. Conclusion
Salmon cartilage contains approximately 16.9% (w/w) total collagen, of which 5.8% is present as native type II collagen. The remaining 11.1% (16.9 − 5.8%) likely comprises denatured type II collagen and other collagen types, such as type XI collagen. Chondrex, Inc. recommends that preparations of salmon-derived type II collagen be validated throughout collection, storage, and manufacturing processes to ensure a higher content of undenatured type II collagen (UC-II) in final products.
Reference