## 4 Discussion
Weak spoilage, as well as acidic and amine off-odors and flavors, increased a bit during storage of the SG and VP CSS, as well as fatty droplets at the products' surfaces, while the perception of the freshness-related odor, flavor and color, such as fresh fish, dill, smoke and orange, decreased slightly over time. Such spoilage sensory characteristics are commonly described for lightly preserved salmon products [5; 6; 10; 69]. They can be induced by the presence of specific spoiling bacteria, such as _B. thermosphacta_, _P. phosphoreum_ and _S. liquefaciens_[65]. The fact that spoilage was classified in the following order: SG > VP CSS > MAP CSS might be explained by the microbial diversity and higher presence of Gram-negative bacteria, such as _P. phosphoreum_ and Enterobacteriaceaeae. Resulting from enzymatic reactions and microbial degradation, the TVBN [4; 10; 70] and biogenic amines [51; 71; 72] can be indicators of spoilage in seafood. In the SG and VP CSS, the TVBN, tyramine, cadaverine and histamine production started when the TVC count reached 6 log CFU/g after 14 and 28 days for the SG and VP CSS, respectively. Although not known to be a fish with a high histidine content, some replicates of each product exceeded 100 mg/kg of histamine, which is the EU regulatory tolerated concentration in some fish species (not including salmon) [73]. This may have been related to the presence of _Photobacterium_ sp. Some authors have found equivalent or even higher concentrations for cadaverine, tyramine and histamine in spoiled CSS [51; 69]. No production of biogenic amines was found in MAP CSS, despite a microbial load of 8.2 \(\pm\) 0.1 log CFU/g. In this product, the microbial ecosystem was mainly dominated by _Lactobacillus_, which are not strong biogenic amine producers in seafood [74; 75]. In the same way, no TVBN production was found in the MAP CSS. In the SG and VP CSS, the TVBN increased slightly over time but did not exceed the European regulatory limit of 35 mg-N/100g for unprocessed salmon [73]. The VOCs composition of the three products, especially the MAP CSS, did not change much over time. However, increases in the concentrations of alcohols (ethanol, 3-methyl-1-butanol, 2,3-butanediol, 1-octen-3-ol, phenylethyl alcohol), aldehydes (nonanal, (E,E)-2,4-decadienal, hexadecanal benzaldehyde, benzeneacetaldehyde), ketones (2-butanone, 1-octen-3-one) and dimethylamine (VP CSS only) were observed. Aldehydes, amines, ketones, alcohols and organic acids production result mostly from microbial activity and their concentration increased concomitantly with the deterioration of the seafood organoleptic properties [8; 76; 77; 78; 79]. For instance, aldehydes resulting from lipids oxidation by microorganisms are good indicators for food degradation and actively participate in the characteristic rancid, cooked potatoes, fatty, floral, fruity and grassy odors of spoiled fish [8; 78; 79]. _P. phosphoreum_, _B. thermosphacta_ and _S. liquefaciens_, which are common seafood spoilers, induced the production of many spoilage-related volatile compounds, such as benzene ethanol, 2-methylpropanol, 3-methyl-2-butanol, 2,3-methyl-1-butanol, 1-propanol, 1-penten-3-ol, acetaldehyde, 2,3-methyl-1-butanol, pentanal, 2-methyl-1-propanol, benzaldehyde, benzeneacetaldehyde, 2,3-butanedione, 2-propananone, 3-pentanone, 3-methyl-2-butanone, 3-hydroxybutanone (acetoin), acetic acid and ethyl acetate, when added in cooked and peeled shrimp and raw and cold-smoked salmon [36; 80; 81]. Interestingly, an important decrease in furanic aldehydes (furfural, 3-methylfurfural, 5-methylfurfural and 3-furaldehyde) was observed during the storage of the two smoked products. Many furanic aldehydes are found in smoked fish [8; 77; 79; 82; 83]. Most of them are found in the smoke but can also be generated through Maillard and Strecker reactions between the wood smoke and the fish flesh during the smoking process [78].