Sensory characteristics of cold-smoked Atlantic salmon (Salmo salar) from European market and relationships with chemical, physical and microbiological measurements

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Abstract

Samples of different brand names of cold-smoked salmon products were purchased in supermarkets in six different European countries (Belgium, Denmark, France, Germany, Italy and United Kingdom), to classify and select products of smoked salmon for preference establishment. From the 117 products obtained, 60 were selected to characterise the qualities of products available to European consumers. These 60 products of smoked salmon were then ordered directly from the producers in each country. Altogether 57 products were received and analysed. All samples were stored at 4 °C and then examined 2 and 3 weeks after production. For all samples, sensory evaluation, chemical (lipid, salt, phenol, TVB-N and trimethylamine content) and physical (texture, colour) analyses and microbiological measurements (total psychrotrophic count, total lactic acid bacteria, lactobacilli, Brochothrix thermosphacta, yeasts, Enterobacteriaceae) were performed at the same time.

The results show that the samples could be classified into 11 groups according to specific sensory properties evaluated by a trained panel. The main discriminating factors were found to be colour, intensity and characteristic of smoke note, amine note and salty perception.

Some of the chemical and physical measurements were found to be rather good indicators of sensory properties. Polynomial models were tested to find relationships between sensory properties and chemical/physical parameters.

Introduction

Vacuum packed cold-smoked salmon is a product with wide range of consumption in Europe and thus of considerable economic importance for the seafood market. Among countries that produce smoked salmon, France is in the lead with 19000t, followed by Denmark (15660t), Germany (15100t) and United Kingdom (10250t) (FAO, 2000). Consumption is mainly distributed among France, Germany, United Kingdom, Italy and Belgium.

Smoked salmon is now a product of general consumption and has lost its luxury image. The development of aquaculture in Northern countries is one of the main reasons contributing to this new status of the product and its wide distribution on the market.

Many studies have been carried out in aquaculture to understand, to control and to optimise salmon growth parameters as well as the main factors involved in the quality of the flesh. A lot of works has been conducted on the onset of the rigor (Berg, Erikson, & Nordtvedt, 1997), the gaping phenomenon (Andersen, Stromsnes, Steinsholt, & Thomassen, 1994; Skjervold, Fjaera, Ostby, & Einen, 2001), the flesh colour (Sheehan, O’Connor, Sheehy, Buckley, & FitzGerald, 1998), the fish lipid content (Aursand, Bleivik, Rainuzzo, Jorgensen, & Morhr, 1994; Hillestad, Austreng, & Johnsen, 1995; Lie, 2001; Robb, Kestin, Warris, & Nute, 2002), the slaughtering techniques (Roth, Moeller, Veland, Imsland, & Slinde, 2002) as well as the processing conditions of the raw material as pre or post rigor filleting effect (Einen, Guerin, Fjaera, & Skjervold, 2002; Skjervold, Fjaera, Ostby, Isaksson, Einen, & Taylor, 2001; Skjervold, Rora, Fjaera, Vegusdal, Vorre, & Einen, 2001). Among these factors, the tailoring of fish fat content is of considerable interest and various studies have followed the effect of a modification of the fish diet on flesh quality (Arzel et al., 1994; Nordgarden, Hemre, & Hansen, 2002, Regost, Arzel, Cardinal, Laroche, & Kaushik, 2001, Rora, Regost, & Lampe, 2003, Sérot, Régost, & Arzel, 2002; Sheehan, O’Connor, Sheehy, Buckley, & FitzGerald, 1996; Turchini et al., 2003). Replacement of fish oils by vegetable oils during the growth has been tested in order to identify how to maintain a good growth rate while controlling the lipid content of the flesh and managing the available lipid sources (Grisdale-Helland et al., 2002).

At the same time, processors of smoked salmon have made efforts to adapt their production parameters to this raw material in order to respect the market demand and to satisfy their requirement for profit. The choice of the processes used (salting techniques, drying and smoking procedures, type of equipment) is large and for each step of the process, the choice of control parameters such as time of salting, concentration of brine or smoking temperature allows specific finished product characteristics to be reached (Cardinal, Berdagué, Dinel, Knockaert, & Vallet, 1997; Chan, Toledo, & Deng, 1975; Indrasena, Hansen, & Gill, 2000). The knowledge of raw material characteristics is an important factor to control in order to obtain the required product quality and many studies have shown their effect on final characteristics and yield (Beltran & Moral, 1991; Cardinal et al., 2001; Rora et al., 1998).

The wide range of raw salmon characteristics as well as the many salting and smoking techniques used by different processors gives rise to a wide range of smoked salmon characteristics available on the market. All year round there is a wide selection of products available to consumers. However, consumers have great difficulties in identifying criteria in order to be able to choose a product according to their preference. Often, the only information available which can help consumers to make their selection are the appearance (e.g., the colour) of the product, the brand name, processing references, e.g., dry salting, the shelf life of the product and of course the price. Recent French market surveys on smoked salmon products, published by consumer review point out a general decrease of quality of smoked salmon on the market (Anon., 2002; Maleysson & Bonneff, 2001). The main criticisms on the quality of the product refer to the appearance, the texture related to fat content, the level of salt and the taste. A study performed on the Italian market reveals that the hygienic quality of the smoked salmon is poor at the expiry date (Vergara, Di Pinto, Losito, & Tantillo, 2001).

The purpose of the present study was to describe the smoked salmon characteristics sold on the European market by sensory evaluation, physical measurements (colour, expressible liquid), chemical analyses (lipid content, salt and phenol level, total volatile basic nitrogen (TVB-N) and trimethylamine (TMA) content) and microbiological analyses (total flora, lactic flora or other specific groups) in order to get an objective overview of the quality of the smoked salmon. The aim of the study was also to evaluate whether it was possible to classify the products according to their sensory properties and to identify whether there was any relationship between sensory characteristics and the chemical/physical parameters.

Section snippets

Sampling in supermarkets

Samples of commercial smoked salmon products were collected in six countries, France, Germany, United Kingdom, Italy, Belgium and Denmark. In the first five countries, large quantities of smoked salmon are consumed, while Denmark is on the forefront of smoked salmon production. It was decided to collect all products available in supermarkets in one or two towns in each country. Supermarkets were chosen as source of sampling because consumers generally purchase cold-smoked salmon there.

Samples

Samples shelf life

Samples of smoked salmon were ordered directly from the producers in each country with a request of manufacturing the product on a predetermined date. It was not always possible for the producers to manage the date of production according to the chosen experimental design and in many cases the exact date of smoking was unknown. The only information available was the declared expiry date (use by date) on the package. Therefore the number of days between the date of analysis and the use by date

Conclusion

This study has shown that cold-smoked salmon available on the European market presents a wide range of sensory characteristics. Consequently, consumers can buy products with a wide range of colour, salt level, texture characteristics, smoke note and smoke intensity. This is a positive aspect for the consumer, as it means that there is a large selection of different products available on the market. Nevertheless, the study shows that 21% of the 57 cold-smoked salmon products evaluated had a

Acknowledgements

This research was performed with the financial support of the European Union in the context of QLK1-2000-01575 project (Improved quality of smoked salmon for the European consumer). The sampling was possible thanks to the logistic support of ADRIANT, partner of the project and its sub-contractors ASAP (Gesellschaft für Sensorische Analyse und Produktentwicklung mbH, Munich), INN (Instituto Nazionale della Nutrizione, Rome), CCFRA (Campden Chorleywood Food Research Association), INSTITUT MEURICE

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