Effects of boiling, deep-frying, and microwave treatment on the proximate composition of rainbow trout fillets: changes in fatty acids, total protein, and minerals

Abstract

Summary This study was conducted to investigate the differences in the proximate composition (moisture, fat, protein and ash), cholesterol content, energy, mineral composition (Na, Ca, Mg, K, P, Fe and Zn) and fatty acid profile of rainbow trout, Oncorhynchus mykiss, after frying, boiling, or microwaving. Results showed that all cooking methods reduced moisture and increased total protein, fat and ash contents. Also all minerals increased significantly during the microwave and frying methods. Statistical results showed that the major fatty acids among the saturated and monounsaturated fatty acids in each fish were palmitic (C16:0) and oleic (C18:1) acids, respectively. In addition, linoleic acid (C18:2) was predominant in the n‐6 polyunsaturated fatty acids (PUFA) in both cooked and raw trout. The EPA (eicosapentaenoic acid; C20:5 ω3) and DHA (docosahexaenoic acid; C22:6 ω6) acids were the major fatty acids among total n‐3 acids in fish samples. The fatty acids profile of the cooked fish showed a saturated (SFA) and monounsaturated (MUFA) decrease and an increase in PUFA contents. However, the ω‐3 fatty acids content increased in microwaved samples but decreased in the fried samples. Moreover, the PUFA/SFA and Hypocholesterolaemic/Hypercholesterolaemic (HH) ratios increased in both fried and microwaved trout, whereas significant increases in ω3/ω6 as well as EPA + DHA/C16 content were observed only in microwaved samples. A significant increase in energy content was observed in all cooked samples, whereas the cholesterol decreased. Research results show that microwaving is recommended as the best cooking method for a healthy consumption of rainbow trout.

Comparative Study of Raw and Boiled Silver Pomfret Fish from Coastal Area and Retail Market in Relation to Trace Metals and Proximate Composition

“…Similar results have been found in boiled rainbow trout fillets [38]. On the other hand, some researchers disagree with our findings in case of three commonly consumed marine fishes in Nigeria [39].…”

“…This might be due to reduction of moisture content. Increased total protein was also found with reduced rate of moisture content in boiled rainbow trout fillets [38]. …”

Impact of Frying on Changes in Clam (Ruditapes philippinarum) Lipids and Frying Oils: Compositional Changes and Oxidative Deterioration

“…A similar observation was made in the content of protein and minerals upon frying of fish and shrimp by Musaiger and D'Souza (). Asghari et al () also reported that the protein and mineral elements (dry basis) decreased when rainbow trout fillets were subjected to deep‐fat frying. These observations indicate extensive absorption of the frying oil into clams.…”

“…Similar to the current study, several researchers observed the decline of FFA content in silver cat fish and anchovy after frying (Turhan et al, ; Weber et al, ). It was suggested that FFA leach out from fried meat and the dilution effects of frying oil accounts for the decrease in AV (Asghari et al, ; Turhan et al, ). Another reason is evaporation assisted by steam during frying.…”

Comparison of different combined processes of preservation on the nutritional and sensory changes of “ready to eat” mackerel fillets

“…However, according to the results, the use of MWB allowed a better retention of minerals in mackerel fillets. It is known in the literature that MWB, compared with the conventional heating methods, leads to less leaching of the nutrient, preserving the overall nutritional content of the processed food (Asghari, Zeynali, & Sahari, ; Gómez‐Guillén et al, ). However, different behaviors in the fractional decrease of lipids were observed among the treatments after marinating.…”