Optical properties of raw and processed fish roes from six commercial New Zealand species

This study characterized colour parameters [lightness (L∗), redness (a∗), yellowness (b∗), chroma (C∗) and hue (h∗)] and spectral surface reflectance of raw and processed roes from the following species: chinook salmon, hoki, southern blue whiting (SBW), hake, blue warehou and barracouta. The roes were processed as karasumi-like at room temperature and as karashi mentaiko at room temperature and at 5 °C. Salmon roe had the highest a∗-values (P < 0.01). Karasumi-like products had lower (P < 0.01) L∗-values compared with raw roes. Apart from hake, roes with intense pigments (e.g. salmon and warehou) had lower a∗-values after karasumi-like processing. Karashi mentaiko processing increased (P < 0.01) a∗-values of roes that had white or translucent background (e.g. barracouta, hoki, and SBW) to a greater extent than those that had yellow/orange background (hake and warehou). Redness (a∗-value) was the major contributor in the separation of different products by canonical analysis. Spectral reflectance of the surface echoed the differences found among the raw roes from different fish species and the impact of processing on the colour of the final products. It is important to determine what influence these colours have on consumer preference.