Determination of rate constant, order reaction model and shelf life of crude hoki (Macruronus novaezelandiae) oil

Abstract

This study was aimed to determine the rate constant, order reaction model and shelf life of crude hoki oil. Fish oil was kept in dark rooms at 2, 20, 30 and 40oC respectively. After 0, 2, 5, 10, 15 and 20 weeks of storage, samples were taken out. The samples were analysed for chemical parameters (peroxide value), physical parameters (refractive index, and colour absorbance) and sensory parameters (odour and taste). Order reaction model was determined by revealing the mode of deterioration involved and employing order reaction equations, i.e. C = C0 ± k0t and In C = In C0 ± k1t for a zero order reaction and a first order reaction respectively. The results showed that the rate of peroxide value changes as well as odour and taste scores changes tended to follow zero order reaction. Meanwhile, the colour loss in crude hoki oil followed both zero- and first order reaction. It was suggested that odour from cold samples was to be employed in generating a shelf life prediction equation. The linear equations ln k = 5.15 – 2077 1/T (r2 = 95.61%) and ln = 3.93 + + 2102 1/T (r2 = 99.98%) were used to estimate the rate constant and predict the shelf life of crude hoki oil, respectively. The estimated shelf life of crude hoki oil stored at 2°C was up to 41 weeks.