3.1. Heavy Metals Content of Canned Fish Samples
The total concentration of the analyzed metals in the samples is presented in
Table 2. The lowest Zn contents were found in canned Atlantic bonito (0.93 ± 0.14 mg/kg ww), while the highest Zn contents were observed in canned European sprat (4.37 ± 0.39 mg/kg ww), although none of the samples exceeded the permissible limit (50 mg/kg) according to Bulgarian Food Codex for marine fishes [
26]. The data in the literature show values between 11.605 mg/kg (canned rainbow trout) and 22.467 mg/kg (canned anchovies) for Turkey [
12], with similar results reported by Tuzen and Soylak [
27]; the average zinc content in canned tuna collected from supermarkets in the region of Vojvodina, Serbia was 21.96 mg kg
−1, while in canned sardines it was 18.21 mg kg
−1 and in canned smoked sprouts it was 21.53 mg kg
−1 [
28].
Copper is essential in promoting a good health condition, but very high intake can cause negative health problems such as kidney damage and liver failure [
29,
30]. Therefore, the Bulgarian Food Codex [
26] recommended a limit for Cu in marine fishes of 10 mg/kg; FAO (1983) [
31] and Maff (1995) [
32] recommended a limit of 30 mg/kg. In our study, the average Cu concentration was as high as 0.48 mg/kg for the canned sample of bluefish in a metal can. In the literature, the mean Cu concentrations were reported to be 1.77 mg/kg in canned anchovy [
33], 0.32 mg/kg in canned pink salmon, and 0.47 mg/kg in canned red salmon [
34], 1.145 mg/kg in canned anchovies and 0.541 mg/kg in rainbow trout [
12], 2.50 μg/g in canned tuna fish and 1.10 μg/g in canned
Trachurus trachurus obtained from supermarkets in Turkey in 2005 [
27].
The iron level in our canned fish samples are similar to the values reported by other authors [
9,
12,
27,
28,
35]. European Union legislation [
36] has not established maximum values for Fe, but Serbian regulations have set a maximum limit for Fe in canned fishery products as 30 mg/kg, while in Turkey, the recommended maximum limit for Fe in canned foods (including fish and fishery products) is 15 mg/kg [
12]. The higher value of Fe in the samples may be caused by pollution of the raw material, the environment itself or other contamination sources (containers, poor handling practices of raw materials, or processing steps on land and/or at sea) [
12,
37].
Among the samples, those with the highest Mn content are those from the European sprat (0.23 mg/kg ww). The minimum and maximum manganese values in the literature were found to be 0.90 μg/g in canned tuna fish and 2.50 μg/g in canned anchovy fish samples produced and marketed in Turkey in 2005 [
27], and 0.012 mg/kg for canned tuna fish, 0.115 mg/kg for canned chub mackerel and 0.524 mg/kg for canned whelk in commonly consumed canned marine products in South Korea [
38]. According to FAO/WHO, the recommended maximum concentration of Mn in food should not exceed 3.00 mg/kg [
39].
The canned fish product with the highest Cr values was Atlantic bonito in vegetable oil (0.54 ± 0.01 mg/kg). The values of Cr values found by other authors vary significantly: from 0.06 to 4.08 mg/kg ww in 34 canned fish samples from seven companies obtained from local markets in Turkey in 2021 [
9]; from 0.97 μg/g in canned sardine to 1.70 μg/g in canned anchovy fish samples in a Turkish study by Tuzen and Soylak (2007) [
27]; and between 0.020 μg/g and 0.038 μg/g in canned tuna and sardine commercially available in the Latin American market [
35]. The Bulgarian Food Codex [
26] reported maximum limits for Cr in marine fishes of 0.3 mg/kg f.w. Additionally, Cr treatment is usually employed to make the Sn layer of cans less vulnerable to environmental impurities and increase the coating adherence [
35,
40].
Ni is of great importance to be determined in foods, since it has a potential to migrate during food processing or packaging [
35,
41]. Usually, canned fish fillets are boiled in Ni-containing vessels, from which contamination could appear [
42]. The content of Ni in the canned fish samples collected in our study varied between 0.011 and 0.065 mg/kg ww. The content of Ni has been reported to be between 0.045 μg/g ww. for canned tuna and 0.056 μg/g ww. for canned sardines available commercially on the markets of Latin America [
35]; between 0.42 μg/g in canned Black Sea bonito and 0.85 μg/g in canned tuna fish [
27]; and between 0.0 and 0.78 μg/g in canned fish samples [
34].
Metals such as Cd, Al and Pb, which may pose certain risks to consumers’ health, were also analyzed. Cd and Pb are among the most dangerous toxic substances and are a part of the Priority List of Hazardous Substances according to ATSDR [
43].
The concentration of Pb in all 32 samples of various canned fish products presented values below the allowed limit (0.30 mg kg
−1 of f.w.) and was in accordance with European Commission Regulation No. 1881/2006 [
36]. The highest value (0.14 mg/kg ww.) was found in the fillets of Atlantic bonito and bluefish with olive oil. Pb values were reported in the literature as 0.0128 ± 0.014 and 0.0183 ± 0.024 in canned tuna and in fresh
Thunnus albacares, respectively, during a six-year study in Italy [
11]; 0.188 mg/kg in canned anchovy and 0.167 mg/kg in canned rainbow trout purchased in Turkey [
12]; and between 0.013 and 1.97 μg/g in canned sardines from Saudi Arabia [
42].
The Cd contamination level of the samples was within the EU Commission Regulation No. 1881/2006 [
36], with a maximum limit of 0.1 mg/kg f.w. Miedico et al. [
11] found a Cd content of 0.0295 ± 0.0415 mg/kg f.w for canned tuna, 0.0132 ± 0.0119 mg/kg f.w for fresh
Thunnus albacare, and 0.0247 ± 0.0108 mg/kg f.w for fresh
Katsuwonus pelamis, while one sample of unspecified fresh tuna showed a concentration of 0.114 mg/kg, which is over the allowed limit. Winiarska-Mieczan et al. [
44] examined several canned fish products available on the Polish market with values of Cd between 0.2 μg/100 g (sprat in tomato sauce) and 1.7 μg/100 g (tuna in olive oil). The average content of Cd in canned rainbow trout on the Turkish market was determined as 0.001 mg/kg, and it was determined as 0.019 mg/kg in canned anchovies [
12].
Al was detected in only one sample, with a value of 0.79 mg/kg ww., and this is below the permissible limits set by FAO/WHO (2017) [
45] at 60 mg/day. This value is similar to or lower than the aluminum concentration found in 102 canned tuna samples in Lebanon (4.756 μg/g) [
8]; in canned tuna commercialized in Canada (3.161 μg/g) [
46]; and those obtained by Korfali and Hamdan [
47] (0.81 mg/kg for eight canned tuna samples collected from the Lebanese market).
3.2. Fatty Acids Composition of Canned Fish Samples
The fatty acid composition (expressed as a percentage of the total fatty acid methyl esters) of canned fish products is shown in
Table 3. Twenty-five fatty acids (C12:0 to C22:6n-3) were identified. The main fatty acids found in the analyzed canned fish products were oleic (C18:1n-9c, from 15.42 ± 0.63 to 31.05 ± 0.62%), palmitic (C16:0, from 12.85 ± 0.17 to 21.49 ± 0.54%), linoleic (C18:2n-6, from 3.48 ± 0.38 to 20.83 ± 0.85%) and docosahexaenoic acid (C22:6n-3, from 7.61 ± 0.40 to 18.13 ± 0.55%).
Regarding the groups of fatty acids, the sum of the fatty acid levels decreased in the order of saturated (SFA) > monounsaturated (MUFA) > polyunsaturated (PUFA) in Atlantic bonito in brine (S1) and in bluefish in extra virgin olive oil (S4) and in vegetable oil (S7). PUFAs were the most abundant group only in Atlantic bonito canned in bio extra virgin olive oil (S2), while MUFAs were the most abundant group in bluefish with honey and sunflower oil (S3). In S5 (Atlantic bonito in vegetable oil), the sum of the fatty acid levels followed the pattern SFA > MUFA = PUFA, and in S6 (European sprat in vegetable oil), SFA = MUFA > PUFA. According to previous studies [
48], the packing medium had no effect on the content of SFA in canned mackerel samples. However, differences were observed in the total MUFA and total PUFA contents.
The potential health benefits of canned fish products could be evaluated through lipid quality ratios and indices like n-6/n-3, PUFA/SFA, AI, TI, and h/H (
Table 4). In our study, PUFA/SFA ratios ranged from 0.58 in bluefish in vegetable oil to 1.26 in Atlantic bonito in bio extra virgin olive oil. Regarding the n-6/n-3 ratios, the analysis showed the lowest value (0.25) in Atlantic bonito in brine and the highest value (1.7) in Atlantic bonito in bio extra virgin olive oil.
Concerning the three nutritional indices, the results for AI and TI were below 1.00 and those for h/H were > 1.00 in all of the studied samples. The lowest AI and TI values and the highest h/H value were detected in Atlantic bonito preserved in bio extra virgin olive oil.
The sum of eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) varied from 11.31 ± 0.57% in bluefish with honey and sunflower oil to 23.13 ± 0.71% in Atlantic bonito preserved in brine, with DHA being the more prominent contributor. According to the European Food Safety Authority (EFSA, 2012), the dietary recommendations for EPA + DHA intake among adults are between 250 and 500 mg/day. Among the studied canned fish products, only bluefish packed in extra virgin olive oil presented an EPA + DHA content (125.39 ± 6.53 mg per 100 g edible portion) lower than the recommended levels. The highest values for EPA + DHA presence (990.27 ± 30.52 mg per 100 g) were detected in the product without any oily filling medium, Atlantic bonito in brine.
3.3. Fat-Soluble Vitamins, Antioxidant Pigments and Cholesterol Content
All analyzed canned fish contained significant amounts of fat-soluble vitamins and cholesterol and low levels of astaxanthin and β-carotene. The results are presented in
Table 5. The fat-soluble vitamin, antioxidant pigment and cholesterol contents are expressed as an average and standard deviation (mean ± SD). The data are shown as micrograms per 100 g wet weight (μg/100 g ww) for vitamin A and D
3, astaxanthin and β-carotene, and as milligrams per 100 g wet weight (mg/100 g ww) for cholesterol and vitamin E.
The comparison of the obtained results with those of our previous studies on the raw tissue of the investigated fish species show convergence in the case of bluefish, but differences in the cases of bonito and sprat. This convergence is attributed to the fact that canning in vegetable oil is considered one of the milder techniques for preparing foods for consumption [
51].
The results presented in
Table 5 show differences in the amounts of all analytes in the same fish species tissues but with different types of preservation (sunflower or olive oil, brine and olive oil with lemon and honey). The highest and lowest values for vitamin A were reported in the samples of Atlantic bonito in olive oil (S2) and sunflower oil (S5), as well as for bluefish in honey and lemon (S3), at about 200 μg/100 g ww. The Spanish database [
52] presented a vitamin A content in bluefish fillets of about 161 μg per 117 g, which is lower compared to our results. On the other hand, the food composition databank (Germany) [
53] indicates a higher amount of vitamins A, D3 and E in canned sprat (390 μg·100
−1 g ww, 14 μg·100
−1 g ww, 2.31 mg·100
−1 g ww). These differences are considered as natural, as commented on in our and other authors’ scientific publications. The content of vitamins in fish tissues depends on many factors, such as the biometric characteristics of specimens, the season of the catch, the cooking techniques used, etc. [
2,
5,
54].
Astaxanthin and beta-carotene (β-carotene) are natural antioxidants. Astaxanthin was found to be better at protecting lipid components and phospholipid’s membranes from peroxidation [
55]. The literature data regarding the vitamins and antioxidant pigment content of canned fish are very scarce and incomplete. Cholesterol is a component of lipids, and in the body is a precursor of a number of important compounds, including vitamin D
3 and some hormones, as well as being included in the structure of cell membranes. Its antioxidative activity is 10 and 100 times greater than that of β-carotene and vitamin E, respectively [
55].
The quantitative analysis of antioxidant pigments in the samples showed that β-carotene was quantified in all of them, while astaxanthin in bluefish (S7) was below the limit of detection. The data for both pigments (
Table 5) varied considerably among the canned fish products, as astaxanthin levels are the highest in Atlantic bonito (S2, 27.3 μg·100
−1 g ww), sprat (S6, 27.1 μg·100
−1 g ww) and bluefish (S3, 20.2 μg·100
−1 g ww), while β-carotene levels are the highest in Atlantic bonito (S1, 7.2 μg·100
−1 g ww). Data on similar analyses were not found in the scientific literature.
The American Heart Association (AHA) stated a maximum daily cholesterol intake of up to 300 mg, and for individuals at high risk of heart disease, the amount should not be higher than 200 mg [
56]. The amounts of cholesterol in canned fish in this study vary within a much narrower range than the other analyzed components (82.7–195.3 mg·100
−1 g ww). These quantities are consistent with those indicated by other authors in the scientific literature. Romero et al. [
57] demonstrated that the range of cholesterol content in canned jurel, sardine, salmon and tuna is between 41 and 86 mg·100
−1 g ww; Manthey-Karl et al. [
58] showed similar data for bonito fillets in brine—51.6 mg·100
−1 g ww. Additionally, the United States Department of Agriculture (USDA) reports in its database a cholesterol content of sprats in oil samples of 107 mg, which is very close to the value presented in
Table 5 (106.7 mg·100
−1 g ww) [
59].
The Bulgarian Ministry of Health, in its Ordinance No. 1/22.01.2018 [
60], sets the recommended daily intakes (RDI) for various nutrients, including fat-soluble vitamins. Based on these recommendations, the amounts of vitamins A, D
3 and E found in the analyzed samples were recalculated as a percentage of the RDI, presented in
Table 5. The indicated results show that most of the analyzed canned fish supply significant amounts of the three vitamins, with the highest contribution being for vitamin D
3. The samples that provide the highest percentage of vitamin A per 100 g serving are S2, S3 and S5 (RDI about 27%); for vitamin D
3, these are sample S5 (142% RDI) and sample S1 (56% RDI); and for vitamin E, these are samples S1 and S2 with 31.8% and 35.8% RDI, respectively.
3.4. Human Health and Food Safety
Besides the numerous benefits of consuming fish and fish products [
1,
6,
7,
61], humans are exposed to certain toxic elements via consumption of them. Fishes may accumulate non-essential metals (Pb, Cd and Ni), and therefore can be considered as a public health threat [
20,
29,
33,
62,
63]. When the risk of toxicity is resolved, analysis of the concentration of the metal in the muscle tissue and the amount of consumed fish is undertaken.
The results of this study indicate that the EWI values of all the elements measured in the canned fish products were lower than the PTWI limits set by various health organizations (
Table 6).
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 2013 adopted an updated PTWI value for Cd of 0.025 mg/kg body weight per week [
64]. If we assume an average consumption of 190 g of canned fish per week, the exposure to Cd is in the range of 1.9 μg to 5.7 μg for canned bluefish. Herrera-Herrera et al. (2019) [
63] reported that EDI/EWI for Cd values in canned tuna and sardine were similar to results of the current study.
Pb is another toxic element related to serious health concerns. The EFSA [
65] set a maximum permissible consumption level of Pb of 1.75 (provisionally) mg/kg of body weight per week. It should be noted that in this study, a maximum value of 0.4 μg was calculated (0.2–0.4 μg). Miedico et al. [
11] reported a value of 2.6 μg for canned tuna and 3.7 μg for fresh yellowfin tuna for exposure to Pb at an average consumption of 200 mg of canned fish per week.
Ni contamination in the body may be responsible for negative health issues such as lung fibrosis, kidney and cardiovascular diseases, and may lead to respiratory tract cancer [
66]. In 2005, EFSA’s Scientific Panel on Contaminants in the Food Chain (CONTAM) adopted an opinion on the risks to public health associated with Ni in food and drinking water, in which it established a tolerable daily intake (TDI) of 2.8 μg/kg Ni/kg bw per day (0.0028 mg/kg Ni/kg b.w or 0.0196 mg/kg Ni/kg b.w tolerable weekly intake) [
67]. In this study, the values of Ni were between 0.0021 mg/kg for canned Atlantic Bonito and 0.0124 mg/kg for marinated bluefish.
The calculated values for the EWI and PTWI showed that the consumption of the canned fish samples was considered safe with regard to Cu, Fe, Zn, Cr, Mn and Al. In addition, many studies have reported that the EDI/EWI values in canned fish are acceptable [
8,
9,
11,
62,
63,
68]. Additionally, there are few studies on EDI or EWI in various canned fish in the literature, which stated that the EDI/EWI values for Fe, Cu, Zn, Al, Cr, Cd, Mn, Pb and Ni are under the PTWI levels stated by health organizations [
69], so these fish samples do not pose risks to consumers’ health.
Table 6.
Estimated weekly intake (EWI; mg/kg BW) values for each element analyzed in various canned fish species.
Table 6.
Estimated weekly intake (EWI; mg/kg BW) values for each element analyzed in various canned fish species.
| | Cu | Fe | Zn | Cr | Mn | Pb | Cd | Ni | Al |
---|
Estimated weekly intake (mg/week/70 kg body weight) | S1 | nd | 0.0586 | 0.0062 | nd | nd | nd | 0.0000 | 0.0000 | 0.1501 |
S2 | 0.00043 | 0.0524 | 0.0055 | nd | nd | nd | 0.0057 | 0.0021 | 0.0000 |
S3 | 0.00027 | 0.0537 | 0.0074 | 0.0014 | 0.0005 | 0.0005 | 0.0019 | 0.0084 | 0.0000 |
S4 | 0.00041 | 0.0679 | 0.0092 | 0.0010 | 0.0005 | 0.0005 | 0.0048 | 0.0072 | 0.0000 |
S5 | nd | 0.0603 | 0.0064 | 0.0015 | 0.0002 | 0.0002 | 0.0048 | 0.0000 | 0.0000 |
S6 | 0.00043 | 0.1186 | 0.0208 | 0.0008 | 0.0006 | 0.0006 | 0.0048 | 0.0086 | 0.0000 |
S7 | 0.00130 | 0.0556 | 0.0059 | nd | 0.0004 | 0.0004 | 0.0029 | 0.0124 | 0.0000 |
PTWI (mg/kg body weight) | | 3.5 [70] | 0.0056 [70] | 7 [70] | 0.7 [71] | - | 0.025 [72] | 0.007 [64] | 0.0028 (TDI) [73] | 2 [70] |
PTWI (70 kg body weight) | | 245 | 0.392 | 490 | 49 | - | 1.75 | 0.49 | - | 140 |
The values of the hazard quotient for the benefit–risk ratio, HQEFA, are presented in
Table 7. The calculated values ranged from 0.001 (Al) for Atlantic bonito in brine to 1.405 (Cr) for bluefish in extra virgin olive oil. In most canned fish, the HQ
EFA values were below 1, therefore posing no risk to people when consuming these products. However, in bluefish preserved in extra virgin olive oil, HQ
EFA for Cr > 1, which means that the risk of consumption of this product may outweigh the benefits of PUFA intake.