Muscle temperature at point of filleting-Subsequent effect on storage quality of pre 1 rigor filleted raw-and cold-smoked Atlantic salmon 2

14 The impact of increased muscle temperature at point of filleting on fillet quality of rawand 15 cold-smoked Atlantic salmon was investigated. Commercially reared fish (5.65 Kg, Kf: 1.23, 16 pH: 7.29, muscle temperature: 6.68 °C) were killed and immediately tempered in three 17 different containers. Muscle temperatures after filleting (< 3 hours post mortem) of the three 18 groups were 2.08 °C (herby named T-2); 9.07 °C (herby named T-9,) and 14.09 °C (herby 19 named T-14), respectively. The pH after filleting was significantly lowest for T-14 (6.93) 20 followed by T-9 (7.06) and T-2 (7.22). Raised temperature at point of filleting was found to 21 significantly alter development of rigor mortis, which subsequently affected muscle pH and 22 the reflective properties of the fillet surface during 14 days ice storage. Of cold-smoked fillets 23 however, a more distinct effect of raised temperature was observed on visual perception 24 resulting in lighter and more yellowish cold-smoked fillets after 14 days storage. In addition, 25 raised temperature also affects development of muscle pH in cold-smoked fillets during 26 refrigerated storage. No effects of raised muscle temperature were found regarding drip loss, 27 water holding capacity or fillet firmness neither for rawor cold smoked fillets throughout the 28 storage period. 29 30 Introduction 31 Preand post mortem muscle temperature are among several factors which affect the quality 32 of farmed Atlantic salmon. It is accepted that high sea water temperature at time of 33 slaughtering results in decreased shelf-life, poor fillet quality and increased gaping (LavÉTy 34 et al., 1988; Love et al., 1969; Sikorski, 1989; Kiessling et al., 2006). These findings resulted 35 in a considerably focus, in the late 90ties, to reduce muscle temperature before slaughtering of 36 Atlantic salmon (Skjervold et al., 2002; Skjervold et al., 2001a; Skjervold et al., 1996). 37 Today’s practice includes either live chilling and/or chilling during exsanguination to secure a 38 low muscle temperature during primary processing which is especially important during the 39 growth season where sea water temperatures can reach up to 16-18°C. Live-chilling of salmon 40 designated for pre rigor filleting is expensive due to a higher input of energy to reduce 41 temperature of a whole salmon as compared to only the fillets. It is therefore interesting to 42 show if a high muscle temperature at time of pre rigor filleting influences quality aspects, in 43 the same pattern, as it do to whole fish or post rigor fillets. 44 The onset and strength of rigor mortis is dependent on several preand post mortem factors 45 such as temperature and handling before harvest, metabolic activity of the fish, pre46 slaughtering stress, post mortem temperature and shows large individual variation (Azam et 47 al., 1989; Sigholt et al., 1997; Jerrett et al., 1998; Mørkøre et al., 2008; Skjervold et al., 1999; 48 Roth et al., 2012; Roth et al., 2006). These factors all results in accelerated autolysis and 49 provide a rapid drop of muscle pH, which is related to flesh softening and reduced water 50 holding capacity (Roth et al., 2002; Aursand et al., 2010). High temperature or short periods 51 of high temperature during processing and/or transport will in all likelihood influence the drip 52 loss. It has also been demonstrated that super chilling can have a negative effect on the water 53 holding capacities in salmon (Hansen et al., 2009). 54 Surface colour and appearance are important decision-makers for consumers when purchasing 55 rawand smoked salmon products (Gormley, 1992; Sylvia, 1996; Anderson, 2000). Colour of 56 salmon flesh is affected by many different parameters, among others; composition and 57 amounts of carotenoids in the feed (Bjerkeng, 2000; Bjerkeng, 2008), genetic background 58 (Torrissen and Naevdal, 1988), seasonal variations (Mørkøre and Rørvik, 2001), starvation 59 and stress prior to slaughtering (Robb et al., 2000; Einen and Thomassen, 1998; Erikson and 60 Misimi, 2008; Mørkøre et al., 2008), slaughtering procedures (Kiessling et al., 2004; Roth et 61 al., 2010), ice chilling and temperature during frozen storage (Espe et al., 2004), muscle fibre 62 density (Johnston et al., 2000), and salting and smoking procedures (Birkeland et al., 2004; 63 Lerfall et al., 2011). 64 The joint focus of mostly all research so far about effects of relatively high temperature has 65 been performed on whole salmon or post rigor fillets. Therefore; the aim of this study was to 66 investigate the effects of increased muscle temperature on rigor mortis, drip loss, textural and 67 reflective properties of raw pre-rigor filleted Atlantic salmon. In addition, subsequent effects 68 on quality of cold-smoked fillets were investigated. 69