Stability of fish lipids during microwave heating

The mince from fresh fish (Baltic herring), frozen mince, mince + oat flakes, and lipids from fresh fish and from frozen mince, were heated in microwave oven for 0, 4, 8, 20, 30, and 40 min. Lipids were extracted using the Bligh-Dyer technique. Peroxide value, anisidine value, fluorescence, absorbance in UV, and sensory profile of odour and flavour were determined. Fatty acid composition was determined with a GC/MS method. The achieved results point to the lack of a catalysing effect of microwaves on the oxidation of fish lipids contained in heated fresh fish meat, as well as during heating of lipids extracted from fresh meat. After 40 minutes of heating of mince, the amount n-3 polyunsaturated fatty acids (EPA + DHA) dropped by 18%, and in the mince with oat flakes by 10%

Comparative analysis of the quality parameters and the fatty acid composition of two economically important Baltic fish: cod, Gadus morhua and flounder, Platichthys flesus (Actinopterygii) subjected to iced storage

Background. During ice storage of fish a series of biochemical changes occur at a relatively rapid pace. The changes involve both nitrogen compounds and the lipid fraction. Lipid damage, through hydrolysis and oxidation reactions, can lead to important losses in nutritive value and quality during chilled storage. Oxidised lipids are a source of free radical compounds and highly reactive peroxides. The aim of this study was to assess the quality of two economically valuable species of Baltic fish, especially the quality of lipids, during storage in ice. Materials and methods. The analysis involved two Baltic fish: cod, Gadus morhua Linnaeus, 1758—a lean fish (about 1% of fat in flesh) and flounder, Platichthys flesus  (Linnaeus, 1758)—an average-fat fish (about 4% of fat in flesh). Descriptive testing was used for quality determination of fish and the chemical changes of nitrogen compounds (TVB-N)(Total volatile bases nitrogen) and lipids (PV—peroxide value and AsV—anisidine value) were analysed. Changes of FA (fatty acids) were based on the qualitative interpretation of chromatograms. Results. In cod, peroxide value reached after 10 days a value of 45.47 mg O* ∙ 100 g–1 of lipids. In flounder peroxide value reached the maximum of 26.98 mg O* ∙ 100 g–1 after 12 days. The initial anisidine values did not differ significantly and remained at a similar level during storage. It was found that the most significant changes involved loss of EPA. After fifteen days flounder lost approximately 6.81 mg of EPA ∙ g–1 of fat (about 10% of initial amount), whereas cod about 9 mg EPA ∙ g–1 of fat (about 26.5% of initial amount). The observed loss of DHA was much lower, in particular in flounder. Conclusion. Different dynamics of oxidative changes were observed. In cod primary oxidation products increased linearly but in flounder such dynamic growth occurred after 12 days of storage still being almost twice as low as that of cod. No significant differences were observed in the secondary oxidation products between the fish. The level of PUFA and especially the level of EPA and DHA decreased. The loss of PUFA were higher in the lipid fraction of cod than flounder and were respectively about 2 pp and about 0.4 pp for each day of storage. Moreover, the dynamics of loss of EPA was greater than DHA

Distribution of lipids and oxidative changes therein in particularized parts of rainbow trout fillets

Lipidy ryb ze względu na swój charakter są bardzo podatne na utlenianie, szczególnie na procesy autooksydacji. Stopień utlenienia lipidów zależy od wielu czynników, w tym od ich rozmieszczenia w tkance mięśniowej. Celem pracy było wykazanie, że poszczególne części fileta z pstrąga tęczowego hodowlanego różnią się nie tylko zawartością lipidów, ale również przydatnością technologiczną, której wyróżnikiem mogą być: szybkość i stopień zmian oksydacyjnych lipidów. Wykazano, że pod względem zawartości tłuszczu część brzuszna filetów pstrągów tęczowych różniła się statystycznie istotnie od pozostałych badanych części ryb. Wykazano także różnice między częścią brzuszną fileta pstrąga a pozostałymi badanymi częściami fileta, dotyczące: dynamiki przebiegu procesu fotooksydacji lipidów, katalizowanego promieniami UV, składu kwasów tłuszczowych, a szczególnie ilości kwasu dokozaheksaenowego (DHA). Nie stwierdzono natomiast statystycznie istotnych różnic w wyjściowym całkowitym poziomie utlenienia (Totox) lipidów poszczególnych części fileta pstrąga.Owing to their nature, fish lipids are highly susceptible to oxidation, especially to auto-oxidative processes. The degree of oxidation depends on many factors including the distribution of lipids in a muscle tissue. The objective of this study was to prove that various parts of farmed rainbow trout fillet differ not only in the content of lipids, but, also, in their technological usefulness, which may be characterized by the rate and extent of oxidative changes in lipids. It was evidenced that, as regards the fat content, the ventral part of rainbow trout fillet differed significantly from the other fish parts analyzed. Also, the differences were proved to exist between this ventral part of the trout fillet and the other fillet parts; those differences referred to: the dynamics of UV rayscatalyzed photo-oxidation of lipids, the composition of fatty acids, in particular the amount of docosahexaenoic acid (DHA). On the other hand, no statistically significant differences were reported in the initial total oxidation value (Totox) of lipids contained in the particularized parts of the rainbow trout fillet

Assessing usefulness of low-value fish in producing snack foods

Płoć (Rutilus rutilus) jest marginalnie wykorzystywana w przemyśle rybnym. Gospodarczo zaliczana jest do ryb małocennych pomimo wartości odżywczej jaką charakteryzuje się jej mięso. Celem niniejszej pracy było określenie wpływu dodatku 10 i 20 % mięsa z płoci odkostnionego mechanicznie (MOM), surowego i przemywanego, do ciasta pszennego, na jego przydatność do produkcji przekąski przypominającej tradycyjne solone paluszki. W paluszkach oznaczono zawartość białka i tłuszczu, profil kwasów tłuszczowych, zawartość błonnika pokarmowego rozpuszczalnego (SDF) i nierozpuszczalnego (IDF) oraz skrobi opornej. Oznaczono również twardość i kruchość paluszków po wypieku. Dodatek MOM z płoci do ciasta wpłynął na zwiększenie zawartości białka ogólnego w paluszkach od około 15 do 30 % (w zależności od wariantu doświadczenia) w porównaniu z próbą kontrolną. Spowodował on również zwiększenie zawartości tłuszczu w produkcie przekąskowym, przy czym najwięcej tłuszczu było w wariantach paluszków z udziałem surowego MOM (odpowiednio: 16,7 i 16,4 %). Zarówno dodatek surowego, jak i przemywanego MOM wpłynął na wzbogacenie paluszków w kwasy tłuszczowe z rodziny n-3 i n-6. We frakcji lipidowej paluszków dominowały głównie kwasy: oleinowy (C 18:1 n-9) – średnio 56 %, linolowy (C 18:2 n-6) – średnio 20 % oraz -linolenowy (C 18:3 n-3) – średnio 10 %. Podczas wypieku paluszków nastąpił przyrost zawartości skrobi opornej od 7,7 do 17,0 % (w zależności od wariantu doświadczenia). Paluszki o wyższej jakości (zwłaszcza pod względem tekstury) uzyskano z przemywanego MOM, jednak zarówno surowe, jak i przemywane mięso odkostnione mechanicznie z płoci stanowi dobry surowiec do produkcji wyrobów przekąskowych o dużej zawartości białka i korzystnym profilu kwasów tłuszczowych.Roach (Rutilus rutilus) is marginally utilized in the fish industry. Despite its nutritional value, from the economic point of view, it is classified into a low-value fish group. The objective of the research study was to determine the effect of a 10 and 20 % addition of mechanically separated roach (MSR), both raw and washed and added to the wheat flour dough, on the usefulness of that dough when manufacturing snacks resembling traditional salty sticks. In the fish sticks produced, the following was determined: contents of protein and fat, profile of fatty acids, content of soluble dietary fibre (SDF) and insoluble dietary fibre (IDF), and resistant starch. The hardness and crispness of the sticks baked were also determined. The addition of MSR to the dough caused the content of total protein in the sticks to increase by ca. 15 to 30 % (depending of the experiment variant) compared to the control sample. Furthermore, it caused the content of fat in the snack product to increase; the highest amount of fat was determined in the stick variants produced using the raw MSR ( 16.7 and 16.4, respectively). The addition of both the raw and the washed MSR enriched the sticks with n-3 and n-6 fatty acids. In the lipid fraction of the sticks, the mainly prevailing acids were: oleic acid (C18:1 n-9), 56 % on average; linoleic acid (C18:2, n-6), 20 % on average; and α-linoleic acid (C18:3 n-3), 10 % on average. While the sticks were baked, the content of resistant starch increased from 7.7 to 17.0 % (depending on the experiment variant). The quality of the sticks produced from the washed MSR was higher (especially as regards their texture); however, both the raw and the deboned roach fish constitutes a good raw material for manufacturing snack foods with a high content of protein and a beneficial profile of fatty acids

Some of fish species as a source of n-3 polyunsaturated fatty acids

Muscle lipids of ten fish species (freshwater: zander, whitefish, roach, burbot and crucian carp; farmed: rainbow trout and carp; and Baltic species: garfish, flounder and sprat) were analysed for fatty acids composition (GC/MS), lipid fractions (HPLC) and susceptibility to oxidation. 100 g of meat of lean freshwater and Baltic fish (roach, flounder, burbot and zander) can provide 50% less n-3 PUFAs than the meat of rainbow trout or whitefish and 4-6 times less than sprat. The susceptibility to oxidation of freshwater fish lipids was higher than in the Baltic species of similar PUFAs content

Lipid changes and sensory quality of whole- and gutted rainbow trout during storage in ice

Background. The aquaculture rainbow trout may be a valuable source of long chain n-3 polyunsaturated fatty acid (LC n-3 PUFA). In the retail these fish are mainly present as a whole or gutted. The present study was aimed at comparing changes occurring in lipids of whole and gutted rainbow trout stored in ice. Materials and methods. The analysis were performed after 0, 3, 7, and 14 days of storage in ice at 2°C and the following assays were carried out: proximate composition; lipid composition high pressure liquid chromatography (HPLC); fatty acid composition gas chromatography /mass spectrometry (GC/MS) by direct tissue saponification; contents of lipids extracted, using the Bligh-Dyer technique; UV-VIS, IR, and fluorescence lipid spectra; peroxide value (PV); anisidine value (AsV); and acid value (AC). Results. Gutting prior to storage made it possible to extend the sensory shelf-life by about 2-3 days and affected the quantitative fatty acid composition and oxidation level during storage in ice. The rainbow trout lipids are resistant to oxidation; oxidation product decomposition rather than lipid oxidation proceeds during storage, the decomposition being more intensive in whole than in gutted fish. It is only when the fish lose their eating quality (2 weeks) that a small increase in the level of oxidation occurs, accompanied by an about 15% loss of n-3 PUFA and a 20% loss of DHA, but only in the whole fish. Conclusion. Gutting rainbow trout prior to storage in ice is appropriate by the extending the shelf-life by about 2-3 days and keeping stable amount of n-3 PUFA during 2 weeks of storage

Content of n-3 long-chain poly-unsaturated fatty acids in fish sticks

Długołańcuchowe polienowe kwasy tłuszczowe z rodziny n-3 (LC n-3 PUFA) są szczególnie cenne ze względów żywieniowych. Głównym ich źródłem są lipidy ryb. Paluszki rybne będące przedmiotem badań łączą w sobie zarówno lipidy mięśniowe ryb (rdzeń), jak również lipidy roślinne (panier). Celem pracy była ocena paluszków rybnych dostępnych na rynku krajowym jako źródła LC n-3 PUFA. Badaniom poddano siedem sortymentów pochodzących od różnych producentów i wyprodukowanych z różnych surowców. Oznaczano udział panieru, zawartość lipidów i skład kwasów tłuszczowych w panierze, rdzeniu i całym produkcie. Wykazano, że badane paluszki rybne są ubogim źródłem istotnych żywieniowo kwasów LC n-3 PUFA. Zawierały one w składzie od 0,09 do 0,16 g LC n-3 PUFA/100 g produktu przy zawartości tłuszczu przed ostateczną obróbką cieplną (smażenie) na poziomie od 6 do 8 %. Wyjątek stanowił sortyment D, wyprodukowany z ryby tłustej, który zawierał nawet dziesięciokrotnie więcej LC n-3 PUFA, przy dwukrotnie większej zawartości tłuszczu, w odniesieniu do pozostałych badanych paluszków rybnych.Long-chain poly-unsaturated fatty acids from n-3 (LC-n-3 PUFA) are especially important owing to their nutrition value. Their main sources are fish lipids. Fish sticks, constituting the research material searched into in this paper, have both the fish lipids (core) and the plant lipids (batter). The objective of this study was to assess fish fingers available on the Polish market as a source of LC n-3 PUFA. Seven products from different manufacturers and made from different ingredients were investigated. The per cent contents of batter and lipids were determined along with the fatty acid composition in batter, core, and in the whole product. It was found that the fish sticks investigated were a poor source of nutritionally significant LC n-3 PUFA. They contained from 0.09 to 0.16 g LC n-3 PUFA/100 g of the product and had a fat content ranging from 6 to 8 % prior to the final heat treatment (frying). The exception was a D assortment manufactured from fat fish with a content of LC n-3 PUFA being ten times higher and a fat content twice as high compared with other fish fingers assessed