Grethe Hyldig

Quality Index Method (QIM) scheme developed for farmed Atlantic salmon (Salmo salar)

Abstract The aim of the study was to develop a Quality Index Method (QIM) scheme for raw, farmed Atlantic salmon ( Salmo salar ) and to evaluate the scheme in a shelf life study. QIM is based on the evaluation of key parameters in the deterioration of seafoods. Demerit points are assigned to selected parameters according to their importance and a Quality Index (QI) is established by cumulating the resulting scores. The maximum storage time in ice was determined with Quantitative Descriptive Analysis (QDA) of the salmon after cooking and found to be 20–21 days. This was used as a reference to enable prediction of the remaining storage time of raw salmon in ice with QIM. The calculated QI evolved linearly with storage time in ice (QI=0.82x (days in ice)+0.18, R 2 =0.97). Individual salmon varied in QI within each storage day. However, the multivariate analysis (PLS1) demonstrated that storage time could be predicted with an accuracy of±1. 5 days, assuming that five salmon from each batch were included in the QIM assessment.

Quality Index Method—An Objective Tool for Determination of Sensory Quality

Abstract Sensory evaluation is one of the most important methods for assessing freshness and quality in the fish sector and in fish-inspection services. Sensory methods performed in a proper way are a rapid and accurate tool providing unique information about food. Traditionally, sensory methods have been seen as a subjective assessment of quality. However, sensory methods can be turned into an objective tool. European fisheries research institutes have developed such a tool, by which sensory assessment is performed in a systematic way with an objective quality assessment method called the Quality Index Method (QIM). It is foreseen that the QIM will be useful to give feedback to fishermen concerning the quality of their catch, which may in turn influence better handling on board. The QIM is a promising method for quick and reliable assessment of the freshness of fish. It is expected to become the leading reference method for the assessment of fresh fish within the European community. It could also become a part of labelling and identification of the catch, particularly in electronic auctioning of catch.

Does feed composition affect oxidation of rainbow trout (Oncorhynchus mykiss) during frozen storage

Rainbow trout ( Oncorhynchus mykiss ) were fed a diet containing either fish oil or rapeseed oil and with or without 200 mg/kg carotenoid (either astaxanthin or canthaxanthin). A total of six diets were obtained: (1) fish oil/astaxanthin; (2) vegetable oil/astaxanthin; (3) fish oil/canthaxanthin; (4) vegetable oil/canthaxanthin; (5) fish oil/no pigment; and (6) vegetable oil/no pigment. The fish were slaughtered and stored in polyethylene bags individually as butterfly fillets for up to 22 months at -20 °C. The composition of the fish muscle at slaughter and during frozen storage was evaluated by sampling after 4, 8, 13, 18, and 22 months. The carotenoid content in the muscle was found to be approximately 9-10 mg/kg of fish for both carotenoids. Primary oxidation lipid products (peroxides) as well as secondary oxidation products (volatiles) were measured. In addition, the level of protein carbonyl groups and the content of tocopherols and carotenoids in the muscle were also measured. To estimate the overall changes in sensory properties of the different samples during storage, a trained sensory panel also evaluated the samples. Both the sensory panel and the chemical analysis revealed that in this investigation fish fed fish oil were slightly more oxidized than fish fed vegetable oil. Results showed that canthaxanthin effectively protected both protein and lipid against oxidation during frozen storage. In contrast, astaxanthin did not seem to have a clear and systematic effect. Results indicated that the feed composition influenced the fish muscle composition and subsequently the oxidative stability of the fish during frozen storage. Besides, other constituents in the feed might influence deposition of antioxidants in the tissue and consequently affect the oxidative stability of the muscle.

'Eating Quality' of Fish- A Review

Abstract The quality of fish is a very complex concept. Quality is frequently described using terms related to nutritional, microbiological, biochemical and physiochemical characteristics alone, but none of these terms serve as adequate indices of quality-sensory perception and consumer acceptability must be included. This paper discusses some of the sensory methods that can be used for fish as objective markers of quality in the chain from catch to consumer with focus on methods used for evaluation of whole raw fish and suggest methods and systems that can build a bridge between research and development, industry, marketing and consumer.

Consumers’ view on determinants to food satisfaction. A qualitative approach

The objective of this study was to gain a better understanding of the multiple determinants to food satisfaction from a consumer perspective. The study includes two focus groups with a total of 20 consumers varying in gender, age, employment and food interest. The results were divided into sections based on the main themes that arose from analysing the focus groups; i) sensory properties, ii) physical wellbeing, iii) expectations and desires, iv) the food context and v) comparison of the importance of the various determinants to satisfaction. Factors important for food satisfaction appear before as well as during and after intake. Before intake, the important factors are; expectations and desires based on memories about previous food experiences and the context in which the food is perceived. Physical wellbeing was mentioned important for the feeling of satisfaction, included in physical wellbeing is the experience of an appropriate energy level after intake. In general the sensory experience seems to be the primary determinant to satisfaction. The hedonic experience of eating could be enhanced by the social company and knowledge about the food inclusive health value and origin. Findings from the study will prospectively be used to develop a questionnaire. The questionnaire will be applied in case studies to measure factors influential in food satisfaction.

Chemical and sensory quantification of geosmin and 2-methylisoborneol in rainbow trout (Oncorhynchus mykiss) from recirculated aquacultures in relation to concentrations in basin water.

Globally, aquaculture systems with water recirculation experience increasing problems with microbial taste and odor compounds (TOCs) such as geosmin and 2-methylisoborneol (MIB). This study investigated the content of geosmin and MIB in water and the flesh of 200 rainbow trouts from eight recirculated aquaculture systems in Denmark. TOC content in the fish flesh was measured by a dynamic headspace extraction method and was evaluated by a sensory panel. The results showed significant correlations between TOC content in water and fish and between chemical analysis and sensory perception. When geosmin exceeded 20 ng/L in the water, 96% of the fish had an intense muddy flavor, but below 10 ng geosmin/L, 18% of the fish (only 3% in special depuration ponds) had an intense muddy flavor. The results indicate that TOC levels <10 ng/L will ensure that a negligible portion of the fish obtains an unpalatable taste and flavor due to TOCs.

Changes in liquid-holding capacity, water distribution and microstructure during chill storage of smoked salmon.

BACKGROUND During recent years, increases in liquid loss and soft texture in cold smoked salmon have been reported, possibly due to increased lipid content and a change in muscle structure. These problems can lead to downgrading of the product. This study aimed to investigate the influence of raw material composition and chill storage on quality parameters of cold smoked salmon. RESULTS Initial smoked fish had a higher liquid-holding capacity (LHC) than samples stored for 20 days. Large fish lost more liquid than small fish. The difference in LHC was consistent with a change in water distribution, which could indicate denaturation of muscle protein. Studies of the microstructure showed the influence of both processing and chill storage. An indication of lipid released from the cells was seen after 20 days of chill storage, which could be related to the reduced LHC at that time. CONCLUSION Both raw material composition and chill storage affected the quality parameters of smoked salmon. This study has improved knowledge about the relationships between muscle structure, liquid-holding properties and water distribution in smoked salmon. Copyright

Sensory properties of marinated herring ( Clupea harengus ) - influence of fishing ground and season

ABSTRACT The sensory properties of marinated herring produced immediately post mortem of raw material from different fishing ground and seasons were described and related to biological, biochemical and functional properties. Subtle variation was encountered in the appearance of whole marinated herring fillets. Fishing ground did not influence the odor, flavor or texture, but there was an apparent effect of season on the sensory profile. The sensory properties were influenced by body weight, but not by age, sex and gonad maturity. The influence of varying lipid content, water content and liquid holding capacity resulted in similar effects showing the high correlation between these properties. The results indicated that variation in sensory quality observed by the industry is not primarily due to the parameters fishing ground and season.

Variation in sensory profile of individual rainbow trout (Oncorhynchus mykiss) from the same production batch.

The variation in sensory profile of rainbow trout (Oncorhynchus mykiss), belonging to the same aquaculture production batch and handled the same way, was explored by using objective sensory profiling on heat-treated minced fillets. In addition, quality index, mechanical texture, pH, fat, and water content were measured. Different groups of fish were sampled 3 different times during a production day. The results showed significant differences in the sensory profiles of individual fish within all 3 groups as well as significant differences between the groups. Differences in mechanical texture were found between individuals in 2 of the 3 groups and between the groups. No differences were found in quality index neither between individuals nor groups. A significant negative correlation between lipid content and firm texture was observed, but in general, the chemical and physical measurements could not explain the differences in the sensory profiling or in the mechanical texture measurements. The results showed that significant differences in the sensory profiles of individual fish from the same aquaculture production batch may occur. Furthermore, the results also showed sensory differences between groups of samples taken at different times during a production day.

Predicting sensory properties from rheological measurements of low-fat spreads

Abstract Ten commercial low-fat spreads were evaluated by a sensory panel, with respect to 13 properties, and by oscillatory measurements on the Bohlin VOR Rheometer. A calibration function was developed to predict the sensory properties from features of the temperature sweeps of the products obtained from the rheological analysis. Not all the properties could be predicted by the rheological measurements, but the two important properties meltability and graininess were successfully predicted. This study shows that meltability of a low-fat spread can be predicted from the steepness of the sweep and that graininess can be predicted from the level of the sweep. The temperature sweep of a low-fat spread together with the calibration function is sufficient to characterise the texture properties and thereby spare some time by reducing the sensory evaluation.