Fig. 1. The 600 MHz ¹³C NMR spectra (180–10 ppm) of lipids extracted from cod roe and milt before and after experimental storage at 4 °C for 1 week. The arrows indicate the regions showing the main changes due to formation of cholesteryl ester.

Fig. 2. The 600 MHz ¹³C NMR spectra of the regions between 75 and 71 ppm showing changes due to cholesterol deterioration in roe and milt before and after experimental storage at 4 °C for 1 week. These resonances originate from the carbon attached to the hydroxyl group of cholesterol (Chol) where the fatty acids are esterified to form cholesteryl esters (CholE).

Fig. 3. Excerpt of the low field region of the 600 MHz ¹H NMR spectra of lipids extracted from cod roe and milt showing resonances from cholesterol and cholesteryl ester before and after 1 week of experimental storage at 4 °C.

Fig. 4. The 600 MHz ¹³C NMR carbonyl region of lipids extracted from cod roe and milt before and after 1 week of experimental storage at 4 °C. (A) downfield region of the carbonyl region where free fatty acids are expected to occur and (B) shows the specific changes observed in the carbonyl region of the spectra. The corresponding chemical shift values are presented in Table 2.

Fig. 5. The 600 MHz ¹³C NMR glycerol and the 35–33 ppm region of lipids extracted from cod roe and milt before and after 1 week storage at 4 °C. The symbol (*) indicates new resonances that may originate from lysophospholipids. PC, phosphatidylcholine; PE, phosphatidylethanolamine; PL, phospholipids; TAG, triacylglycerols.

Lipid class composition (% of total lipids) of cod roe and milt before and after experimental storage at 4 °C for 1 week

Both neutral and polar solvent systems are used for the TLC separation. n.d.: not detected; PC: phosphatidylcholine, PE: phosphatidylethanolamine, PL: phospholipids.

Chemical shift values of the carbonyl region (and the region between 33 and 35 ppm) of the ¹³C NMR spectra of reference standards and lipids extracted from cod roe and milt before and after experimental storage at 4 °C for 1 week

PC: phosphatidylcholine, PE: phosphatidylethanolamine, PL: phospholipids; TAG: triacylglycerols; MUFA: monounsaturated fatty acids; SFA: saturated fatty acids.