مدلی برای ارتباط کیفیت حسی در زنجیره فرآوری غذای دریایی A Model for Communication of Sensory Quality in the Seafood Processing Chain

INTRODUCTION Quality is a multidimensional and complex concept since many different parameters have effects on product quality (Bremner, 2000). The quality of food can be defined as the degree to which a product meets certain needs under specified conditions. The definition depends on the particular context where it is applied, and with differences in the concept of quality confusion can arise mostly due to the combined qualitative and quantitative dimension of quality (Grunert, 2005). Consumer perception of food is in its nature subjective, but in the communication in the food chain between researchers, industry, and retailers a common view of an objective definition is necessary. The correlation and translation between the subjective and the objective understanding of quality is at the core of the economical importance in the production chain (Grunert, 2005). The product is competitive only when the producers have an understanding of the consumer perception. Many factors influence the perception of food quality as described in the Total Food Quality Model, introduced by Grunert et al. (1996). The model includes the importance of health, convenience, and processing but the importance of sensory quality is also emphasized. However, managing sensory quality of food products is complex, since it is affected by various factors. In the following fish is used as a food model (Fig. 1). In relation to fish some factors are connected to the living fish for example, genetics, age, seasons, and growing conditions. On top of that catching methods, handling after catch, method of slaughtering, processing, storage, and transport are important. The steps from catching or slaughtering until consumption are referred to as the seafood processing chain. In all the steps in the chain, time and temperature are very important for sensory quality. Time and temperature correlate to the loss of freshness, which is of major importance for the sensory quality (Nielsen et al., 1997; Olafsdottir et al., 1997; Peary et al., 1994). The different steps take place in different locations as fishing vessels, aquaculture ponds and pens, slaughterhouses, different means of transport, processing industry, fishmongers, supermarkets, catering businesses, and homes of consumers (Hyldig et al. 2007; Hyldig 2007). All these steps might have a different concept of sensory quality. The importance of a good management practice of sensory quality increases with increasing number of steps and partners in the seafood processing chain. Sensory analyses are already used in many of the steps in the chain. The partners in the chain generally believe that they deliver a quality, which satisfies the next partner in the chain; but the terms of sensory quality are seldom used in a systematic way. Additionally, the results from the evaluations are normally not recorded or shared between the different steps. Furthermore, most of the participants only have little knowledge about the sensory quality demands of the consumers (Martinsdottir et al., ´ ۲۰۰۸). This paper outlines how sensory analysis can be used in the seafood processing chain, and suggests a Seafood Sensory Quality Model (SSQM) to be used for communication between the partners in the chain. The vision of SSQM is as a general tool that can be used to manage quality in the total chain. SENSORY EVALUATIONS IN THE SEAFOOD PROCESSING CHAIN To understand the SSQM it is necessary to understand which sensory methods are relevant to be used in the seafood processing chain; and to go into details of where and how the methods can be used in the different steps in the chain. The choice of method depends on a number of different factors including the reason of performing the sensory evaluations. An overview of important factors of relevance for the sensory evaluations in the seafood processing chain can be seen in Table 1. The table includes references to Fig. 2 which shows an example for a typical seafood processing chain, including suggestions for where it can be relevant to perform sensory evaluations (test points). The value of the SSQM depends on the reliability of the sensory evaluation performed in each step of the seafood processing chain. Demands to sensory quality need to be defined, the most appropriate methods must be used in evaluations, and sensory evaluations should be performed according to standards as for example, the guidelines for sensory test (NMKL Procedure No 21, 2008; ISO standards 8586-1, 1993; ISO standards 8589, 1988). The sensory evaluations can be performed as visual inspection, measurement of odor, texture, and taste. Visual inspection can be performed on whole fish and raw or heat treated fillets. Chance in freshness influence the appearance of fish and visual inspection can therefore be part of freshness evaluation. Visual inspection can also be used to detect other characteristics as fish species, physical damage, and the presence of some diseases in the fish. Physical damage can cause a fast reduction in shelflife. Furthermore, it can influence the appearance of the final product (Hyldig et al., 2007). Another purpose of visual inspection can be to check the product for foreign matter not wanted in the product. This can be sand, seaweed, packing material, bones, or parasites. Also, the quality of washing, packing, gutting, bleeding, and filleting as well as the amount of ice packed with fish can be inspected with visual tests. Additionally, flesh color, gaping, and homogeneity of the flesh can be tested with visual inspection of both raw and cooked fish. In total there are many different objects of visual testing that are relevant for inspection in the seafood processing chain. Visual inspection can be relevant to perform in all the showed test points in relation to Fig. 2. Another type of sensory assessment is evaluation of odor, which again can be performed on both raw and heat treated samples, while evaluation of taste is done on heat treated products or products preserved in another way, like sushi and marinated fish. In the seafood industry, sensory tests of the taste are normally performed on a company’s final product (Martinsdottir ´ et al., 2008). Odor and taste evaluation of seafood can be made as part of a freshness evaluation, for instance by checking for the presence of rancid odor and flavor. Odor and taste evaluations can also be performed to check off-odors, for example, muddy or earthy odors (Howgate, 2004) or spices in manufactured products. Texture can also be measured on both raw and cooked samples, and texture evaluations can be part of a freshness evaluation since for example, firmness of the fish flesh is reduced during storage in ice (Sveinsdottir et. al, 2002). Other aspects of texture which can be of interest are juiciness and toughness of the cooked fillets. Different sensory methods can be used in the sensory evaluations. It is important that the methods used have sufficient precision in measuring a given characteristic (Costell, 2002). Additionally, the methods usually need to be fast both to perform and in the subsequent data analysis. The most suitable methods are generally descriptive tests and quality ratings, which make it possible to measure the degree of the variation between the product and the demands to sensory quality. In some cases in/out methods can be recommended (Munoz et al., 1992). In descriptive tests the intensity of a single sensory parameter is evaluated on a scale (Lawless and Heymann, 1998). The result from the descriptive tests needs to be translated into different quality levels. The main advantages of using descriptive tests in a production chain are that the result gives a complete picture of the characteristics and their intensity. The disadvantages of descriptive tests are that they are relatively time demanding in training of the assessors and in data treatment (Munoz et al., 1992). In quality rating, characteristics are also evaluated on scales. However, these scales are quality scales with end points such as “very poor quality” and “excellent quality.” Quality rating has some disadvantages compared to descriptive tests as descriptive tests give the intensity of every single attribute. This means that more detailed data can be established from descriptive tests. Additionally, quality rating also demands a longer training program for the assessors compared to the descriptive test (Munoz et al., 1992), since it is important that the assessors understand the different quality levels. Descriptive test and quality rating can both be used for many different purposes in relation to the seafood processing chain. This includes determination of freshness, appearance (including color and homogeneity), odor (including off-odors), taste, and texture (Table 1). Descriptive test and quality rating are therefore relevant methods in most of the test point shown in Fig. 2 (test point 2 to 4 and 6 to 10). In in/out methods the assessors decide whether the product is within or outside a given standard. Assessors also need to be trained in using the standards; however, the training is not as extensive as for descriptive methods. Another advantage is that the results are known instantly. In/out methods can be used if a simple classification of the samples is satisfactory (Munoz et al., 1992). The in/out method is especially relevant in relation to on-line evaluations (test points 1 and 5 in Fig. 2). For instance in/out methods can be used in evaluation of appearance, physical damage, fish diseases, unwanted substances, parasites, bones, amount of ice in the box, gaping, and quality of gutting, washing, packing, and filleting. As described, the measurement of fish freshness is important in the seafood processing chain. In the example from Fig. 2, it is relevant to measure freshness in test point 3, 4, 7, 9, and 10. Specific sensory methods including the EU scheme (Anon., 1996), Quality Index Method (QIM) (Bremner, 1985; Hyldig and Green-Petersen 2004), and the Torry scale (Howgate et al., 1992) have been developed for the evaluation of freshness of fish.