Salmon quality: Methods to determine the quality parameters

Abstract

The objective of this paper is to review the important quality parameters, standards, and simple tools or methods to determine the quality of fresh Atlantic salmon (Saltno salar). Based on a literature review and interviews conducted in several companies throughout Europe, the following quality parameters are of particular importance: fat content, composition and distribution of the fat in the fillet; color intensity and distribution of the color in the fillet; and texture, where firmness (hardness and elasticity) and gaping are the main parameters for fresh salmon. Other parameters cited are white stripes (connective tissue), bleeding, blood stains, marbles, and melanin. Fat, pigments, and collagen are distributed differently over the salmon fillets. Consequently, the numerical values of the quality parameters are different depending on where the sample is collected from the fillet. Sampling is the most important factor in the evaluation of salmon fillet quality. Many sampling procedures are available and the technique differs widely and samples are collected from the head to the gut opening, depending on the country, research institute, or company. Fat content can be measured by both destructive and non‐destructive methods. Several destructive chemical extraction methods are commonly used, but the non‐destructive methods available are, for example, the Tony Fish Fat meter and near infrared technology, but they are used to a limited extent in the industry. The elite image and high market value of salmonids are due in part to the characteristic color of their flesh. The color of the flesh is an important criterion for the quality of salmon and hence crucial for marketing. It is not only important that the fish have satisfactory flesh color, but the pigmentation must be uniform and stable during storage. Methods to determine the degree of pigmentation of salmon fillets can be divided into two main groups; destructive chemical analysis for quantification of the pigments astaxanthin/ canthaxanthin in the flesh and non‐destructive methods based on estimating the color appearance. Color of salmon fillets is determined by using the Roche color card or a chroma meter reflectance instrument. Texture is commonly examined by the so‐called finger method in the industry. A finger is pressed on the skin or the fillet and the firmness is evaluated. Texture of salmon fillets is measured by different tests using “Instron‐like”; instruments. However, the results depend on the location where the fish/fillet is pressed and how firmly it is pressed. To select one method and recommend it depends on the application purposes. These methods have to be tested further and comparisons made between different methods before it is possible to recommend the best available method for each application.