Changes in the EPA and DHA content and lipids quality parameters of rainbow trout (Oncorhynchus mykiss, Walbaum) and carp (Cyprinus carpio, L.) at individual stages of hot smoking

Abstract

The aim of this study was to evaluate qualitative changes in lipids of two most popular freshwater farmed fish (rainbow trout and carp) at particular stages of hot smoking process (brining, drying, smoking and heating). In order to characterize qualitative changes, the amount of peroxides (PV), secondary oxidation products (AsV) and the degree of hydrolysis of lipids (AV) was determined during the smoking process. The studies were carried out both in the fraction of lipids extracted using chloroform-based method (free lipids), as well as the fraction extracted by Bligh and Dyer method of the 1:1 chloroform: methanol ratio (bound lipids). Heat smoking results in loss of fat, especially at the last two stages of the process and the final contents of lipids were about 18% lower in the carp samples and about 10% lower in the trout samples. The dynamics of free lipid oxidation (Ch-lipids) was much smaller than the lipids extracted using B-D method, but the trend of lipid changes was similar. There was no significant difference in the anisidine value between two species, both for free lipids (Ch-lipids) and bound lipids (B-D-lipids), except for the last stage of smoking. No statistically significant differences between the studied species were found also in the case of lipid hydrolysis level, but after the smoking process an amount of free fatty acids increased. Subsequent stages of smoking process resulted in statistically significant losses of EPA and DHA in both fish species and in both types of lipids, i.e. B-D-lipids and Ch-lipids.

La trucha (Oncorhynchus mykiss): Potenciales productos alimenticios derivados del principal recurso acuícola en regiones altoandinas

“…El aumento de L* pudo atribuirse a la pérdida de agua de las muestras durante su refrigeración. Bienkiewicz et al (2019) estudiaron los cambios en la cantidad de ácidos grasos omega 3 (mg/1 g de lípido) de la fracción de lípidos extraída (relación cloroformo:metanol de 1:1) en las etapas de ahumado en caliente: salado, secado, ahumado y calentado, que reportaron valores de 109, 107, 82 y 81 mg/1 g de lípido, respectivamente; los factores físicos como la temperatura y los procesos oxidativos en los lípidos ocasionaron pérdidas de ácidos grasos omega 3, adicionalmente, durante las etapas de salado, secado, ahumado y calentado, los valores de TVB-N (mg/100 g) fueron de 7, 7,4, 8,1 y 9 mg/100 g, respectivamente; mientras que los valores de actividad de agua variaron de 0,911 a 0,958. Por otro lado, el uso de tecnologías de barreras en filetes de trucha, que involucran el ahumado en caliente y congelación como operaciones previas al uso de alta presión hidrostática, demostró un efecto sinérgico.…”

Improvement of Sensorial, Physicochemical, Microbiological, Nutritional and Fatty Acid Attributes and Shelf Life Extension of Hot Smoked Half-Dried Pacific Saury (Cololabis saira)

“…Nowadays, smoked fish and fishery products have shown greater appeal to the consumer due to their delicacy in taste, aroma, and color [ 9 ]. Smoking treatment preserves food mainly because of the synergistic effects of temperature, table salt, and other chemical substances released from sawdust with a reduced water activity [ 10 ]. Moreover, smoking treatment prevents the growth of microbes and delays the oxidative changes in food materials [ 11 ].…”

“…Currently, the two types of smoking methods have been practiced for processing and preservation of fishery products; cold smoking (30 °C), smoking without thermal breakdown [ 14 ], and hot smoking (70–80 °C), with a thermal breakdown [ 15 ]. Among these, the hot smoked processing products are considered to be more acceptable by the consumer over cold-smoked ones, because of delicacy in color and attractive appearance [ 10 ].…”

“…Despite the popularity of using hot smoking in the preservation of fish and fishery products, the underlying mechanism of interactions between wood-derived chemicals and the food matrix which achieve its sensorial, physicochemical, microbiological, nutritional, and fatty acid profiling attributes is rudimentary. The hot smoke method has been employed for 70–80 °C heat treatment and results in the cooking of fish with considerable palatability, thus making it suitable for direct consumption [ 10 ]. The quality of smoked fishery product was assessed using (1) sensory evaluation based on color, texture, odor, flavor, and overall preference; (2) physicochemical parameters such as textural properties and levels of pH, VBN, TBARS, Trimethylamine-N-oxide (TMAO), and fatty acid profile; (3) nutritional value, including calories, protein, lipid, and minerals; and (4) microbial-growth estimation [ 16 , 17 ].…”

Effect of Technological Process on True Retention Rate of Eicosapentaenoic and Docosahexaenoic Acids, Lipid Oxidation and Physical Properties of Canned Smoked Sprat (Sprattus sprattus)

“…The different effects of smoking on the percentage and content of EPA and DHA in fish observed in the literature may depend on the species of fish, different degree of lipids extraction, and smoking parameters [19,25,31,32].…”