Physical measurement of the quality of fresh scad (Trachurus trachurus) and rainbow trout (Oncorhynchus mykiss) during ice storage using the RT Freshmeter

The RT Freshmeter was used to obtain a quality index of two Portuguese fish, scad (Trachurus trachurus) and farmed rainbow trout (Oncorhynchus mykiss). The curves obtained were comparable to those previously published using the GR Torrymeter. However variations were lower during the first phase of storage and it was observed that the curves could be divided into two distinct regions. The slope of the linear regression was higher during the first 5 days of storage, representing the first region of the curve, in both fish studied. It is proposed that the two different rates of change of the quality index obtained with the meter reflect the two predominant spoilage mechanisms, enzymic and microbiological. The RT Freshmeter measurements are compared to organoleptic changes. Preliminary results obtained with the RT Freshmeter on rainbow trout fillets without skin indicate that this instrument is not suitable for use with this product due to large variations and curve slopes close to zero.