Towards valorization of herring filleting by-products to silage 2.0: Effect of temperature and time on lipid oxidation and non-enzymatic browning reactions

The objective of this study was to investigate the effect of temperature and time on lipid oxidation and non-enzymatic browning reactions during ensilaging of herring by-products. Ensilaging for 0-7 days between 7 and 47 degrees C revealed an increasing development rate for peroxide value (PV) and 2-thiobarbituric acid reactive substances (TBARS) from 7 degrees C to 22 degrees C followed by a decreasing trend until 47 degrees C. Similarly, specific oxidation markers, e.g. malondialdehyde (MDA), 4-hydroxy-hexenal (HHE), and 2,4-heptadienal had equal development rate at 7 and 22 degrees C; but, substantially lower development rate at 47 degrees C. At 47 degrees C, there was on the other hand a more pronounced formation of saturated aldehydes and non-enzymatic browning products. This study thus showed that the degree of oxidation in silages was higher at elevated temperatures, although not visible in the classic oxidation analyses PV and TBARS. Therefore, addition of e.g. 2-pentylfuran as an oxidation marker is suggested when targeting the production of high-quality silage 2.0.