Analysis of lipid classes and the fatty acid composition of fresh and the salted fish, Alburnus tarichi

Abstract This study was carried out to determine the distribution of total, phospholipid and triacylglycerol fatty acid composition in salted and fresh fish of pearl mullet. Fatty acid analyses were performed in muscle tissues of the fish samples. Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA), Omega-3 (n-3), Omega-6 (n-6) which are important for health, were determined in the analyses. The distribution of total and TAG fatty acids in males and females was similar. It was determined that the changes were in the Phospholipid. N-3/n-6 ratio showed a similar distribution in both female and male individuals. In particular, the results obtained may benefit the fisheries industry, nutritionists and researchers, as the nutritional value of the fish is high.


Introduction
It is accepted that the consumption of seafood has advantages for humans in terms of nutrition and health. Fish and other seafood are considered good sources of essential amino acids, vitamins, minerals and polyunsaturated fatty acids (Corapci & Guneri, 2020). Since the nutritional composition of the fish affects both its quality and technological properties, it is important to process the fish correctly, and as a result of the process, the content of the fish must be preserved throughout the year. In general, different processing methods such as freezing, frying, boiling, and salting are used to provide a longer shelf life by giving the fish a fresh and attractive form for consumers.

Veysi Kizmaz
ABOUT THE AUTHOR Veysi Kizmaz I am a teaching fellow at Mardin Artuklu University in Turkey. As a field of study, I am working on Lipid Biochemistry and Lipid Physiology. I am one of the international authors specifically on fatty acids analysis. I wrote articles and reports on fatty acids in journals, congresses, and symposiums. I have articles and reports in terms of experimental and ecophysiology in different living groups. Our aim in our research projects is to determine the fatty acids that are especially important for health and to inform the society in terms of health. It is aimed to determine the fatty acids in the products consumed for a healthier life.

PUBLIC INTEREST STATEMENT
Local people consume pearl mullet both salty and fresh. In particular, this study reveals the changes of fatty acids, which is necessary for living systems, in fresh and salted fish. The importance of fatty acids in terms of health is known. With this study, it is ensured that fish that are important for health are consumed. From the data obtained in the study, it was determined that fish is important for health and should be consumed regularly. The study contains important findings especially in terms of omega 3, EPA, and DHA. Furthermore, the fact that this fish, which is an endemic species, is important for health is crucial in terms of culturing and spreading this fish.
These methods have significant effects on the chemical, physical, and nutritional composition of the fish. These effects cause physical and chemical changes (Aberoumand, 2020).
Salting has been used in human history long before other processes such as fumigation, drying, canning, and marinating. In particular, it is one of the oldest techniques known to man for the preservation and increase shelf life of fish (Hafez et al., 2019). Salted fish products have been shown to be safe for millennia, even in developed countries. Salting techniques are simple and are made with salt crystals or brine. Generally, dry salting, wet salting and a combination of the two methods are used. The length of the salting time and the salt concentration depend on the expected end product. Salt intake depends on many factors such as the quality and chemical composition of the raw material, type, muscle type, fish size, fillet thickness, weight, physiological condition, salting method, brine concentration, duration of the salting process, and fish/salt ratio (Hafez et al., 2019). Generally, sodium chloride (NaCl) is used in fish processing due to its protective feature. Salting in traditional fish products is carried out with 1.0-11.6% NaCl (w/w) or high sodium content (Guo et al., 2019). Salted fish is one of the most consumed fish products in the world and is considered a traditional food in many countries (Nikiforova et al., 2019). Fish is one of the most potential sources of animal protein and contains 66-84% water, 15-24% proteins, 0.1-22% lipids and is very close to animal foods in terms of basic components (El Bassir Arha et al., 2015). Omega-3, highly unsaturated fatty acids (HUFA), eicosapentaenoic (EPA), docosahexaenoic (DHA) acids and amino acids in fish help consumers to protect themselves from various diseases such as blood pressure, coronary heart disease, and cancer (Abraha et al., 2018). Recent epidemiological, clinical, and nutritional studies in animals and humans have shown that marine fish oils rich in polyunsaturated fatty acids of the omega-3 series are beneficial in preventing certain forms as well as reducing the risk of coronary heart disease and atherosclerosis (El Bassir Arha et al., 2015).
Pearl mullet (Alburnus tarichi), which is the only fish species that can live in Lake Van, accounts for 1/3 of the fish production in the region and inland waters of Turkey (Yellow, 1997), and consumed as an economically important food source in the Eastern Anatolia Region. Thus, in our study, total, PL, and TAG fatty acid analysis in muscle tissue of salt-dried and fresh fish of pearl mullet was carried out to give information about its fatty acid composition and nutritional quality. Considering the information about food composition and quality of the fish, which has an important place in our diet, these data will provide useful information about health and nutritional values.

Material and method
Fresh fish samples were caught by local fishermen using blind (towing) nets on Lake Van, which is located between Yeşilsu Village (38°46' 51.30"N, 43°17' 36.78"E, 1684 m) close to Van province. Salted fish samples were analyzed after they were taken from local markets in the region. The genders of fresh and salted fish were determined by dissection and examining the gonads under a light microscope.
The lipid extraction in muscle tissue was performed according to chloroform-methanol (2:1 v/v) method of Folch et al. (1957). Fatty acid analysis of oil samples converted to methyl esters was analyzed using a SHIMADZU GC 2010 PLUS model Gas Chromatography device, flame ionization detector (FID) and DB-23 (Bonded 50 % cyanopropyl) (J & W Scientific, Folsom, CA, USA) capillary column (30 m x 0.25 mm inner diameter x 0.25 μm film thickness). Detector temperature: 250 °C; injector temperature: 250 °C; injection: Split-model 1/20. Gas flow rates: Carrier gas: helium 0.5 ml/min; hydrogen: 30 ml/min; dry air: 400 ml/min for 30 m column. Column (oven) temperature: standby time, 2 min at 170 °C; 2 °C/min until 210 °C, standby time 20 min; total analysis time: 42 min. Chromatograms of fatty acids methyl esters and total fatty acids amounts were obtained on the computer with GC Solution (Version 2.4) computer program. Fatty acid percentages were analyzed by one-way analysis of variance (ANOVA). Differences were determined by the TUKEY HSD test. As a result of the statistics, it was accepted that the differences were significant when the data were at the P < 0.05 level.
In our study, when the distribution of total and TAG fatty acids in male individuals was considered, it was found that 18:3 n-3 was 923.53% lower in total fatty acid and 830% lower in TAG in salted fish compared to fresh one. While high or low levels of other fatty acids were detected in previous studies, the distribution of other fatty acids was similar in our study. When the total fatty acid distribution in the female individual was considered, 18:3 n-3 was 875% lower and 20:4 n-6 was 60,62% lower in salted fish compared to fresh one. Other fatty acid distributions were similar.
Order of fatty acids was ΣPUFA>ΣMUFA>ΣSFA in fresh P. polyactis and in fresh Laker, while the order was ΣMUFA>ΣPUFA>ΣSFA in salted Lakerda fish and in fresh and salted A. fallax lacustris, it was ΣPUFA>ΣSFA>ΣMUFA in P. polyactis, fresh and salted Thunnus thynnus L., Baikal omul in Bottarga (Cai et al., 2017;Garaffo et al., 2011;Guizani et al., 2011;Moretti et al., 2016;Nikiforova et al., 2019;Ormanci et al., 2015). The order was found to be ΣPUFA>ΣSFA>ΣMUFA in Mullet in both fresh and salted fish, while the order was ΣSFA = ΣMUFA>ΣPUFA in fresh sardine and ΣSFA>ΣPUFA>ΣMUFA in salted one (Elshehawy et al., 2015). The order was ΣMUFA>ΣSFA>ΣPUFA in both fresh and salted Golden Mullet (Hedayatifard & Yousefian, 2010). In Grass carp fish, ΣSFA was similar in dorsal and ventral of fresh and salted fish, MUFA was similar in ventral, while it was 8.89% higher in dorsal of the salted fish. Total PUFA in both dorsal (25.69%) and ventral (30.71%) was lower in salted fish. In fresh and salted fish, the order was ΣSFA>ΣMUFA>ΣPUFA in the dorsal, while ΣSFA = ΣMUFA>ΣPUFA in the ventral (Guo et al., 2019). Total SFA in muscle phospholipids of the five carp species in India ranged from 31.1% to 35.7% in four species. It was detected at a rate of 63.5% due to 16:0 found around 50% in only Catla catla. The rate of ΣMUFA in four species was found to be 15.1-21.3%, and ΣPUFA was between 33-56% (Ackman 2002). In our study, when the fatty acid distribution as total and TAG in both salted and fresh fish in male individuals was considered, it was ΣSFA<ΣPUFA<ΣMUFA; in fresh fish, it was ΣPUFA>ΣSFA>ΣMUFA for PL, in salted fish, it was ΣMUFA>ΣSFA>ΣPUFA (Table 1). The highest percentage of ΣSFA was found in PL, ΣMUFA in TAG, and ΣPUFA in PL in fresh fish and in total in salted fish. In terms of ΣMUFA, while the percentage of phospholipids in fresh fish (20.38%) was the lowest, it showed a similar percentage distribution in salted fish as in total and triacylglycerol. It showed a distribution as ΣPUFA>ΣMUFA>ΣSFA in fresh fish and as ΣMUFA>ΣPUFA>ΣSFA in salted fish in female individuals. When the triacylglycerol distribution was considered, the percentage of 18:3 n-3 was found to be 700% lower in salted fish than that in fresh fish. The other distributions were similar. Distribution was in the order of ΣMUFA<ΣPUFA<ΣSFA in fresh and salted fish. When the fatty acid distributions in the phospholipid were considered, it was observed that 14:0 was 189.14%, 16:1 n-7 was 116.99%, 18:1 n-9 was 54.28%, and ΣMUFA was 66.89% higher in the salted fish than those in the fresh fish. In the case of polyunsaturated fatty acids, 20:4 n-6 (116.91%), 22:5 n-3 (52,39%), 22:6 n-3 (74.01%), ΣPUFA (54,96%), n-3 (54,42%), and n-6 (57,17%) were found to be lower as a percentage in salted fish compared to fresh one. The distribution was ΣMUFA<ΣSFA<ΣPUFA in fresh fish, while it was ΣPUFA<ΣSFA<ΣMUFA in salted one (Table 2).
DHA and AA are precursors of many bioactive lipid mediators which are actively involved in the regulatory responses and resolution of inflammation. Especially in the brain, DHA is involved in neuronal growth, neuronal migration, synaptogenesis, synaptic plasticity and gene expression. Regarding synaptic function, studies on mice indicate that dietary AA has positive impacts on cognition and synaptic plasticity in aging animals. Especially in recent years, important studies have been carried out in understanding the cellular and molecular mechanisms underlying the neuroprotective effect of DHA and AA in the extreme stages of life (Sambra et al., 2021). In another study, it was reported that EPA and DHA have beneficial effects in many diseases, including cardiovascular disease, metabolic syndrome and chronic inflammatory diseases, as well as brain and liver protection. Especially in studies on respiratory diseases, it was reported that n-3 PUFA in fish oil alleviates allergic asthma. It was stated that this effect is due to the higher content of n-3 PUFA in erythrocytes. From the point of view of N-3 PUFA, it was shown that it is an interesting approach in terms of chronic obstructive pulmonary disease (COPD) and Asthma treatments (Zúñiga-Hernández et al., 2022). It is rich in AA, EPA, and DHA values in our study, indicating the importance of this fish.
It has been shown that the n-6/n-3 ratio in the foods should be 3/1. However, in modern diets, this ratio is expressed as 15/1. A study on biopsy specimens, especially in fatty liver patients (NAFLD), indicated that the n-6/n-3 ratio was significantly correlated with the TAG content of the liver. In a study on rats, it was reported that liver damage was prevented as a result of feeding a diet rich in fish oil (Valenzuela et al., 2020). In our research data, it can be seen that it should be consumed in terms of health, since n-6/n-3 is parallel to the rate that should be taken with the diet.

Conclusions
Consumption of fish and fish derivatives is recommended by health authorities, not only because of its high-quality protein content, but also because it is a source of fatty acids that are considered extremely beneficial for human health (Garaffo et al., 2011). It has been shown that especially the n-3/n-6 fatty acid distributions in fish are useful for comparing nutritional values. World Health Organization (WHO) states that the daily n-3/n-6 ratio should not be less than 1:5 in a balanced diet (Ormanci et al., 2015). The n-3/n-6 ratio in pearl mullet is within the recommended values, which is important in terms of nutrition. In addition to this value, it is stated that EPA + DHA in a balanced diet is 0.65 g/100 g for daily nutrition. In our study, this value was determined at a similar rate. In this regard, pearl mullet seems to be a valuable food in terms of EPA+DHA intake. Hence, the results obtained in this study can benefit researchers who study the nutritional value of fish, the fishing industry, nutritionists.

Funding
The author received no direct funding for this research.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Citation information
Cite this article as: Analysis of lipid classes and the fatty acid composition of fresh and the salted fish, Alburnus tarichi, Veysi Kizmaz, Cogent Food & Agriculture (2022), 8: 2126052.