Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2011
Volume 14
Issue 1
Topic:
Food Science and Technology
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Domiszewski Z. , Bienkiewicz G. , Plust D. , Kulasa M. 2011. QUALITY OF LIPIDS IN MARINATED HERRING, EJPAU 14(1), #09.
Available Online: http://www.ejpau.media.pl/volume14/issue1/art-09.html

QUALITY OF LIPIDS IN MARINATED HERRING

Zdzisław Domiszewski1, Grzegorz Bienkiewicz1, Dominika Plust2, Marta Kulasa2
1 Food Quality Department, West Pomeranian University of Technology, Szczecin, Poland
2 Food Quality Department, West Pomeranian University of Technology in Szczecin, Poland

 

ABSTRACT

Marinated herring is one of the popular fish preparations all over Europe and particularly in Poland. The aim of this paper is to asses the commercially available herring marinades as a source of LC n-3 PUFA and to analyse the level of lipid oxidation in these products. 16 assortments of oil marinades available in the domestic market, delivered by five major producers, were examined. In both meat lipids, extracted using the Bligh and Dyer method, and in marinating liquid the following qualities were measured: the composition of fatty acids and the level of oxidation (PV, AV and TOTOX). The prevalent group of fatty acids were MUFA, averaging 48% of the total, followed by PUFA, with an average of 28%, and  SFA, 24% on the average. An analysis of lipid oxidation revealed: PV of 8–17 meq O2/kg,  AV of 4–19, and TOTOX value between 24–53. The level of lipid oxidation showed good reservoir quality, as in any of the samples did not exceed TOTOX index value 10. A 100g portion of product (meat) contains, depending on the sort, 2.7–3.8 g of n-3 PUFA and 2–2.7g/100g of EPA + DHA. Despite the fact that many factors, such as hauling season, method of storing raw material, differences in technology can affect lipid composition of fillets, it is not arguable that oil marinades available in the domestic market are a rich source of essential long-chain unsaturated fatty acids (LC n-3 PUFA). Nonetheless, when consuming fish products of this kind one should bear in mind that they may contain high amounts of oxidation products leading to a rancid taste of the products.

Key words: marinated fish, vegetable oils, fatty acid composition, omega 3, EPA&DHA, lipid oxidation, food quality.

INTRODUCTION

Tests of merchantable quality of foodstuffs, conducted in Poland by the Trading Standards Association, prove that, in many cases, fish preparations such as marinades are products, whose quality is challenged most frequently. Polish retail fish market is characterised by a decreasing number of  low-processed (salted, smoked, frozen) fish products, and an increasing number of high-processed products, that are easy to use, such as marinated fish, fish convenience food, fish fingers or canned fish [45]. Polish standard PN-A-86780:1998 defines fish marinades as preparations for direct consumption, made by marinating fish in a marinating liquid, with an optional addition of vegetables or other foodstuffs. A similar definition is given by Meyer [52] and Kołakowski [47]. Depending on the manner of preparation and processing technology there are three kinds of marinades: cold, cooked and fried. Cold marinades are typical (real) marinades that can be made from fresh, salted or frozen fish [47]. Standard marinating liquid consists of synthetic vinegar, water and salt; other kinds of liquids can be oil, mayonnaise or tomato-based [47]. High-fat fish, such as herring, [42, 50], sardine [24, 35] and saury [64] are used for production of marinades.  The Sea Fisheries Institute, basing on the data of the Central Statistical Office of Poland, estimates that in the last decade the yearly output of marinades in Poland was about 50 000 tonnes and was only about 15% lower than the yearly output of canned fish.

Marinades are popular and traditional fish products in Poland, with an about 9% share in the overall fish food market. Baltic herring and Atlantic herring, both being high-fat fish, rich in valuable long-chain polyunsaturated n-3 fatty acids (LC n-3 PUFA) [36,42,68,74], are the main material used for production of marinades. Clinical and epidemiological research proved that n-3 PUFA acids  present in fish are beneficial in treatment of various illnesses, including circulatory system, nervous system [21,48,56] and immune system diseases [19]. Characteristic composition of high-fat fish lipids (high amount of unsaturated fatty acid and low amount of natural antioxidants) makes these fish particularly susceptible to oxidation processes [2,38]. Because of this there is a danger that primary and secondary oxidation products accumulated during lipid peroxidation may not only contribute to the deterioration of the biological properties of fat, but also, as it is believed, can be the main agent responsible for cell damage and, in many cases, primary cause of cell death [10,13]. Because of the fact that fish are an essential source of LC n-3 PUFA in Polish diet, it is necessary to monitor the quality of lipids in fish products with regard to the level of LC n-3 PUFA and the level of oxidation, in order to guarantee the highest nutritional value of fish products.

Popularity of oil marinades in the Polish market continues to rise at the expense of traditional vinegar-based marinades. According to the Nielsen Company (that monitors, among others, fish products market) in the february-march 2008 december-january 2009 period oil marinades hold the highest share of the cold herring products market (47%), followed by herring marinades in dressings (22%), vinegar-based marinades (18%) and matjas herrings (13%) [51]. Despite the fact that the oil marinades market is rapidly growing no publication on this kind of fish product was found. This product has two sources of lipids: fish muscle tissue and oil. All available data applies only to vinegar-based marinades or dressing marinades and is obtained by analysing a controlled marinating process of a well-characterised high quality raw material.

The main criterion for selection of samples was the particular assortment producer's share of the domestic fish marinades market, what helped to present a broad picture of LC n-3 PUFA content and lipid oxidation level of oil marinades available for the consumers.

The aim of the work is to assess the quality of lipids in oil marinated fish. The quality of lipids was determined by a compositional analysis of fatty acids, measuring the level of oxidation and by sensory analysis.

MATERIALS AND METHODS

Samples
Research material consisted of 16 assortments cold oil marinades, obtained from five producers. The marinades have been coded as: 1–16.  Every examined marinade was within the expiry date, as stated on the packets. After opening the marinades solid and liquid parts were separated and the proportions of meat (marinated herring fillet), oil and supplements in the product were determined. Oil, after draining, was filtered, fillets and skin were shredded with an electric tool.

Analytical Procedures
Lipids were extracted with a chloroform:methanol mixture (1:2 v/v) according to Bligh Dyer [11], extraction was performed twice. 20 g of sample was homogenized with a chloroform-methanol (1:2 v/v) solution for 2 min, followed by the addition of chloroform and deionized water mixed for 30 s. The chloroform layer was separated from the methanol-water layer. Lipid content was determined gravimetrically and expressed as g/100g wet weight.

Quality of both fish lipids and lipids from oil was determined by an analysis of the following factors: peroxide value (PV), anisidine value (AV), TOTOX value, along with an analysis of the composition of fatty acid (FA) via gas chromatography. PV of lipids were determined with the thiocyanate technique [59], based on oxidation of ferrous salt with hydroperoxides and the reaction of ferric salts with potassium isothiocyanate. The red ferric complexes formed were determined spectrophotometrically. PV expressed as meq O2/kg lipids. Anisidine value and total oxidation value (Totox) were determined according to the International Norm [27]. Totox values were calculated from the relationship TOTOX = 2PV + AV. Fatty Acid Methyl Esters (FAME) were prepared according to AOCS [6] and then separated by gas chromatography (Agilent 7890A) coupled with mass spectrometry. FA analysis parameters: SPTM column – 2560, 100 x 0.25 mm ID, 0,20 ľm film, catalog number 24056, carrier gas helium: constant flow rate of 1.2 cm3/min, split ratio 1:50, injector temperature 220°C; detector temperature 220°C; oven temperature: 140°C (5 min) increase to 240°C in 4°C/min., total time of analysis 45 min. Interpretation of chromatograms was made by comparing the retention times and the mass spectra of individual FAME of the examined sample with the retention times and mass spectra of the respective Sigma FAME standards (Lipid Standard).

Sensory analyses
For the sensory assessment of marinade quality Quantitative Description Analysis (QDA), performed according to the procedure in the ISO [28] was used. The evaluation was made on the basis of previously defined lists of quality indicators: aroma, colour, texture and flavour. Profile characteristics of the examined products were compiled by a team of 6 subjects trained in sensory profiling. Sensory quality of marinades was also measured in terms of consumer desirability (hedonistic score), using a scaling method. The scale was a 10 cm long line segment consisting of 10 standard units (s.u.) with the extremes being: "it does not satisfy me at all" and "it satisfies me a lot".

Statistical analysis
Numbers presented in the tables and pictures are the mean values of three concurrent iterations. Statistical analysis was based on the one-way analysis of variance, homogeneous groups were formed according to the Duncan test for p < 0.05. The data were statistically analysed using STATISTICA (data analysis software system) by StatSoft, Inc. (2005), version 7.1. www.statsoft.com.

RESULTS

Marinades provided by different producers are described in Table 1. Compositional analysis of individual assortments of marinades revealed significant differences between the examined assortments in terms of the amount of main ingredient: marinated herring fillet, oil and supplements. Fillet content was between 50% and 60%, oil content between 11.5% and 32%, and vegetable content from 11% to as much as 30%.

Table 1. Body length, trunk length and body weight in American mink
 

proportions (%)

additives

vegetables

meat

oil

vegetables

1

45.1

31.2

23.7

E 954, E 211, E 202

onion, cucumber, carrot, dill, spices

2

38.0

33.0

29

E 211, E 202

onion, spices

3

60.0

28.9

11.1

E 954, E 211, E 202

pickled onion, spices

4

60.0

23.7c

16.3

E 954. E 211, E 202

pickled cucumber and pepper, spices

5

41.3

28.9

29.8

E 954, E 211, E 202

onion, pickled cucumber and pepper, spices

6

60.0

26.6

13.4

E 954, E 211, E 202

onion, pepper, spices

7

51.9

32.0f

16.1

E 954, E 270

onion, spices

8

53.7

26.4

19.9

-

pickled onion and cucumber, spices

9

53.7

27.3

19

E 954

pickled onion, dried tomatoes, spices

10

58.5

22.1

19.4

E 954, E 211, E 260

pickled cucumber, spices

11

51.2

30.6

18.2

E 954

onion, spices

12

57.3

15.7

27

E 954, E 211, E 260

pickled onion, spices

13

60.0

11.5

28.5

E 954, E 211, E 260

pickled onion, spices

14

47.9

28.1

24

E 954, E 211, E 260

onion spices

15

60.0

24.3

15.7

E 954

onion, spices

16

49.2

28.6

22.2

E 954, E 211, E 260

onion, pickled cucumber. spices

1. 2. 3 ...code of marinades

Apart from vegetables and seasoning, the examined assortments, assortment 8 being an exception, contained also food additives, mainly saccharin and sodium benzoate.

Lipid content and composition of fatty acids
Lipid content in meat and the composition of fatty acids of the examined marinades are presented in Tables 2 and 3.

Table 2. Lipid content (g/100g wet weight) and fatty acids composition (% of total fatty acid) in the fish meat (assortments 1–9)
 

1

2

3

4

5

6

7

8

9

                   

lipid

17.99

16.68

15.38

12.46

16.47

16.61

17.29

18.55

16.82

                   

C 14:0

13.65

10.86

6.53

6.35

10.86

6.51

5.27

4.79

5.89

C 15:0

0.39

0.26

0.27

0.33

0.26

0.34

0.12

0.11

0.10

C 15:0

0.65

0.59

0.37

0.40

0.59

0.38

0.30

0.27

0.27

C 16:0

16.93

16.97

19.21

20.33

16.97

19.62

12.79

12.41

14.87

C 17:0

0.12

0.11

0.10

0.12

0.11

0.12

0.09

0.07

0.07

C 16:1

4.66

5.01

3.34

3.42

5.01

3.51

3.20

3.32

3.75

C 17:0

0.23

0.22

0.18

0.18

0.22

0.19

0.12

0.10

0.12

C 17:1

0.26

0.18

0.36

0.29

0.18

0.31

0.18

0.19

0.17

C 18:0

1.16

1.56

1.92

1.63

1.56

1.73

1.10

1.14

1.26

C 18:1

13.74

20.56

31.16

29.86

20.56

30.44

25.65

32.22

20.02

C 18:2 (n-6)

4.01

6.31

7.82

7.48

6.31

7.96

4.67

6.48

4.30

C 20:0

0.29

0.28

0.22

0.21

0.28

0.21

0.21

0.23

0.23

C 20:1

9.55

7.16

2.02

2.22

7.16

1.29

10.13

3.44

2.68

C 18:3 (n-3)

0.46

1.61

3.24

3.02

1.61

3.43

2.91

7.63

10.13

C 18:4 (n-3)

3.42

2.48

1.74

2.15

2.48

1.96

1.40

1.31

1.66

C 20:2 (n-6)

0.32

0.35

0.47

0.43

0.35

0.47

0.17

0.14

0.17

C 22:1

13.47

8.67

2.26

2.31

8.67

2.35

18.29

13.06

19.62

C 20:3 (n-3)

0.31

0.36

0.20

0.24

0.36

0.28

0.30

0.26

0.36

C 20:4 (n-6)

0.17

0.14

0.30

0.24

0.14

0.26

0.03

0.03

0.01

C 20:4 (n-3)

0.64

0.57

0.56

0.73

0.57

0.63

0.26

0.24

0.33

C 20:5 (n-3)

6.59

5.88

5.69

5.82

5.88

5.67

4.73

4.98

5.23

C 24:1

0.60

0.66

0.89

0.93

0.66

0.96

0.65

0.51

0.59

C 22:5 (n-3)

0.92

0.87

0.37

0.45

0.87

0.39

0.33

0.28

0.37

C 22:6 (n-3)

7.46

8.33

10.79

10.88

8.33

11.01

7.11

6.80

7.79

                   

Σ SFA

33.42

30.85

28.80

29.56

30.85

29.10

20.00

19.11

22.82

Σ MUFA

42.28

42.24

40.02

39.02

42.24

38.86

58.11

52.75

46.83

Σ  PUFA

24.30

26.91

31.18

31.43

26.91

32.05

21.90

28.15

30.35

Σ n-3 PUFA

19.80

20.10

22.59

23.28

20.10

23.37

17.04

21.50

25.87

Σ n-6 PUFA

4.50

6.80

8.59

8.15

6.80

8.68

4.86

6.64

4.48

Σ n-6/ Σ n-3

0.23

0.34

0.38

0.35

0.34

0.37

0.29

0.31

0.17

C20:1+C22:1

23.02

15.83

4.28

4.53

15.83

3.64

28.42

16.51

22.30

EPA + DHA

14.05

14.22

16.49

16.70

14.22

16.68

11.84

11.79

13.02

Σ  LC n-3

15.92

16.02

17.61

18.12

16.02

17.98

12.73

12.56

14.08

Σ  LC n-6

0.49

0.49

0.76

0.66

0.49

0.73

0.19

0.16

0.18

1. 2. 3 ...code of marinades

Table 3. Lipid content (g/100g wet weight) and fatty acids composition (% of total fatty acid) in the fish meat (assortments 9–16)
 

9

10

11

12

13

14

15

16

lipid

16.82

16.18

19.88

18.90

19.43

20.50

17.72

16.78

                 

C 14:0

5.89

4.67

5.16

4.68

4.91

3.00

5.83

5.26

C 15:0

0.10

0.11

0.11

0.10

0.11

0.06

0.25

0.14

C 15:0

0.27

0.27

0.31

0.27

0.27

0.16

0.34

0.29

C 16:0

14.87

12.75

11.98

12.63

12.06

11.25

16.99

13.85

C 17:0

0.07

0.06

0.05

0.04

0.07

0.03

0.10

0.07

C 16:1

3.75

3.52

2.48

2.57

3.12

1.63

3.36

3.24

C 17:0

0.12

0.10

0.12

0.11

0.10

0.08

0.15

0.12

C 17:1

0.17

0.20

0.09

0.07

0.18

0.05

0.25

0.19

C 18:0

1.26

1.17

1.28

1.46

1.10

1.35

1.54

1.28

C 18:1

20.02

32.51

30.49

33.08

31.94

36.37

30.82

29.54

C 18:2 (n-6)

4.30

6.53

6.48

7.52

6.43

8.43

7.44

6.41

C 20:0

0.23

0.22

0.26

0.28

0.24

0.32

0.22

0.24

C 20:1

2.68

3.45

3.13

3.79

3.44

4.76

2.13

4.20

C 18:3 (n-3)

10.13

7.35

8.15

7.00

7.91

7.25

5.05

6.48

C 18:4 (n-3)

1.66

1.22

1.17

1.30

1.40

0.54

1.69

1.41

C 20:2 (n-6)

0.17

0.13

0.15

0.13

0.15

0.12

0.35

0.20

C 22:1

19.62

12.14

17.04

13.09

13.99

13.35

6.62

12.95

C 20:3 (n-3)

0.36

0.27

0.23

0.17

0.26

0.18

0.27

0.28

C 20:4 (n-6)

0.01

0.02

0.01

0.01

0.03

0.01

0.17

0.06

C 20:4 (n-3)

0.33

0.22

0.23

0.21

0.25

0.12

0.48

0.31

C 20:5 (n-3)

5.23

5.31

4.11

4.13

4.65

4.45

5.38

5.05

C 24:1

0.59

0.48

0.44

0.32

0.53

0.32

0.78

0.58

C 22:5 (n-3)

0.37

0.26

0.22

0.19

0.30

0.13

0.34

0.32

C 22:6 (n-3)

7.79

7.04

6.32

6.86

6.56

6.04

9.45

7.54

                 

Σ SFA

22.82

19.36

19.26

19.57

18.86

16.24

25.42

21.26

Σ MUFA

46.83

52.29

53.67

52.92

53.20

56.49

43.96

50.70

Σ  PUFA

30.35

28.35

27.07

27.52

27.94

27.27

30.62

28.05

Σ n-3 PUFA

25.87

21.67

20.43

19.86

21.34

18.71

22.67

21.38

Σ n-6 PUFA

4.48

6.68

6.64

7.66

6.60

8.56

7.95

6.67

Σ n-6/ Σ n-3

0.17

0.31

0.33

0.39

0.31

0.46

0.35

0.31

C20:1+C22:1

22.30

15.59

20.17

16.88

17.43

18.11

8.75

17.15

EPA + DHA

13.02

12.35

10.43

10.99

11.22

10.49

14.83

12.59

Σ  LC n-3

14.08

13.10

11.11

11.56

12.03

10.92

15.92

13.49

Σ  LC n-6

0.18

0.15

0.16

0.14

0.17

0.13

0.51

0.26

1. 2. 3 ...code of marinades

Lipid content in fish meat was within a relatively wide range between 12.4 g and 20.5 g  in 100g. The prevalent group of fatty acids in meat lipids of all examined assortments of marinades were monounsaturated fatty acids (MUFA), which constituted from 40% to as much as 60% of the total number of analysed fatty acids (FA). This FA group was dominated mostly by 18:1 acids, which, except for the assortment 1, most often constituted between 40 – 70% of the total MUFA. As far as MUFA are concerned, it is worth noticing that the proportion of a sum of C 20:1 and C 22:1 acids, was, depending on the assortment examined, within a very wide range from 4% to as much as 30% of the total amount of FA. Variability of these acids was three times lower that variability of the rest of the MUFA group (Tables 2 and 3). Only in three assortments (numbers 1, 2 and 5) the percentage of saturated fatty acids (SFA) in the total amount of FA was higher than the percentage of polyunsaturated fatty acids (PUFA). Among the main groups of fatty acids it were SFA that were marked by the highest coefficient of variation (CV) of 25% and their percentage in the total amount of FA of meat lipids was between 16% and 33%. In every examined marinades this acid group was dominated by two acids: C 14:0 i 16:0, which constituted on average 90% of the total SFA. PUFA were characterised by the lowest CV of about 10%; their percentage in meat lipids was between  25 and 32% of the total amount of FA (Tables 2 and 3). Among PUFA, n-3 acids were the prevalent group (75% of the total PUFA on average); their amount was 3 to 4 times higher than the amount of n-6 family PUFA. Among n-3 PUFA the prevalent group consisted mainly of two LC n-3 PUFA: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), that amounted to 60-70% of the total n-3; while 90% of n-6 family composed of C 18:2 acid. The amount of n-3 PUFA in fish meat was between 2.7g and 3.8g in 100g and the amount of  both EPA and DHA from 2g to 2.7g in 100g of meat (Tables 4).

Table 4. The contents of n-3 PUFA and EPA + DHA (g/100g wet weight) in the fish meat
 

n-3 PUFA

EPA + DHA

recommended amount*
(EPA + DHA)

0.5 (g/day)

1 (g/day)

1

3.49g

2.48h

20.2

40.3

2

3.80h

2.71j

18.5

36.9

3

3.40f

2.14f

23.4

46.7

4

2.84bc

2.04bcd

24.5

49.0

5

3.24e

2.30g

21.7

43.5

6

3.80h

2.70j

18.5

37.0

7

2.88c

2.00ab

25.0

50.0

8

2.80abc

2.06cde

24.3

48.5

9

3.03d

2.14f

23.4

46.7

10

2.82bc

1.96a

25.5

51.0

11

2.80abc

2.02bc

24.8

49.5

12

2.81abc

2.08de

24.0

48.1

13

2.77ab

2.11ef

23.7

47.4

14

2.73a

2.07cde

24.2

48.3

15

2.98d

2.62i

19.1

38.2

16

3.05d

1.99ab

25.1

50.3

*amounts of meat (g) that contain the recommended amount of EPA + DHA
a. b – values represented by the same letters in column are not significantly different from each other with p< 0.05;
1. 2. 3 ...code of marinades

A compositional analysis of fatty acids present in the oil revealed that the prevalent group of acids in all of the assortments were MUFA, whose percentage in the total amount of FA was at a constant level of 66-68% (CV of about 2%) (Tables 5 and 6). C 18:1 acids represented 95–98% of this group. In the oil part, PUFA displayed the highest variability, with their percentage in the total amount of FA being between 20% and 27%. Two acids were prevalent in this group: C18:2, representing on average 70% and C18:3, representing 25% of the total PUFA, which constituted respectively 17% and 6% of the total FA (Tables 5 and 6). In PUFA group marginal (0.23% on average) amounts of EPA + DHA were observed. C 16:0 was the prevalent acid in SFA, constituting on average 70% of the total SFA; percentage of SFA in the total amount of FA was on average 7.5% (Tables 5 and 6).

Table 5. Fatty acids composition (% of total fatty acid) of oil (assortments 1–8)
 

1

2

3

4

5

6

7

8

C 14:0

0.52

0.47

0.33

0.47

0.35

0.38

0.25

0.05

C 16:0

8.85

8.17

7.15

8.45

7.66

7.55

3.68

3.80

C 16:1

0.60

0.51

0.43

0.55

0.52

0.47

0.15

0.16

C 18:0

2.43

2.12

2.57

2.22

2.39

2.17

1.11

1.10

C 18:1

64.94

65.24

62.51

65.35

64.79

64.51

67.30

66.81

C 18:2 (n-6)

15.00

15.36

16.82

14.76

15.37

15.82

18.75

19.15

C 20:0

0.33

0.37

0.56

0.42

0.38

0.47

0.40

0.40

C 20:1

1.50

1.41

1.87

1.33

1.64

1.45

0.66

0.82

C 18:3 (n-3)

4.71

5.22

6.05

4.83

5.45

5.57

6.91

6.93

C 18:4 (n-3)

0.07

0.08

0.07

0.09

0.08

0.08

0.11

0.12

C 20:2 (n-6)

0.11

0.11

0.09

0.10

0.11

0.10

0.45

0.41

C 22:1

0.60

0.73

1.23

1.12

0.98

1.11

0.10

0.12

C 20:5 (n-3)

0.12

0.09

0.13

0.12

0.12

0.13

0.07

0.08

C 22:6 (n-3)

0.21

0.12

0.19

0.18

0.18

0.19

0.06

0.05

                 

Σ SFA

12.13

11.13

10.61

11.56

10.78

10.56

5.45

5.35

Σ MUFA

67.64

67.89

66.04

68.35

67.92

67.54

68.21

67.91

Σ PUFA

20.22

20.98

23.35

20.08

21.30

21.89

26.34

26.74

Σ n-3 PUFA

5.11

5.51

6.44

5.22

5.82

5.97

7.14

7.18

Σ n-6 PUFA

15.11

15.47

16.91

14.86

15.48

15.92

19.20

19.56

Σ n-6/ Σ n-3

2.96

2.81

2.63

2.84

2.66

2.67

2.69

2.73

C20:1+C22:1

2.10

2.14

3.10

2.45

2.62

2.56

0.76

0.94

EPA + DHA

0.33

0.21

0.32

0.31

0.29

0.32

0.13

0.12

Σ LC n-3

0.33

0.21

0.32

0.31

0.29

0.32

0.13

0.12

Σ LC n-6

0.11

0.11

0.09

0.10

0.11

0.10

0.45

0.41

1. 2. 3 ...code of marinades

Table 6. Fatty acids composition (% of total fatty acid) of oil (assortments 9–16)
 

9

10

11

12

13

14

15

16

C 14:0

0.09

0.20

0.19

0.26

0.12

0.17

0.16

0.12

C 16:0

3.99

3.91

3.93

3.79

3.74

3.80

3.78

3.71

C 16:1

0.22

0.22

0.22

0.21

0.17

0.20

0.20

0.18

C 18:0

1.11

1.11

1.13

1.12

1.18

1.12

1.10

1.10

C 18:1

66.18

66.94

67.45

67.53

68.37

67.47

67.68

67.94

C 18:2 (n-6)

18.95

18.51

17.91

18.13

18.24

18.23

18.30

18.39

C 20:0

0.40

0.39

0.38

0.38

0.38

0.39

0.38

0.39

C 20:1

0.89

0.86

1.20

1.12

0.74

1.02

0.95

0.83

C 18:3 (n-3)

6.86

6.72

6.24

6.18

6.33

6.45

6.37

6.50

C 18:4 (n-3)

0.40

0.30

0.55

0.46

0.09

0.38

0.32

0.19

C 20:2 (n-6)

0.45

0.42

0.41

0.41

0.35

0.41

0.40

0.38

C 22:1

0.21

0.20

0.16

0.17

0.08

0.15

0.15

0.11

C 20:5 (n-3)

0.09

0.08

0.06

0.07

0.08

0.09

0.07

0.07

C 22:6 (n-3)

0.14

0.14

0.17

0.16

0.13

0.14

0.14

0.10

                 

Σ SFA

5.59

5.61

5.62

5.54

5.42

5.48

5.43

5.31

Σ MUFA

67.50

68.23

69.04

69.04

69.35

68.83

68.98

69.06

Σ PUFA

26.90

26.16

25.33

25.42

25.22

25.69

25.60

25.63

Σ n-3 PUFA

7.50

7.23

7.02

6.87

6.63

7.05

6.90

6.86

Σ n-6 PUFA

19.40

18.93

18.31

18.54

18.60

18.64

18.70

18.77

Σ n-6/ Σ n-3

2.59

2.62

2.61

2.70

2.81

2.64

2.71

2.74

C20:1+C22:1

1.10

1.07

1.37

1.30

0.81

1.17

1.10

0.94

EPA + DHA

0.23

0.22

0.23

0.23

0.21

0.23

0.21

0.17

Σ LC n-3

0.23

0.22

0.23

0.23

0.21

0.23

0.21

0.17

Σ LC n-6

0.45

0.42

0.41

0.41

0.35

0.41

0.40

0.38

1. 2. 3 ...code of marinades

Oxidation level
Peroxide value (PV), anisidine value (AV) and Totox value of meat lipids of analysed assortments were significantly higher than those of marinating oil (Table 7).

Peroxide content in meat was from 8.5 to as much as 17 meq O2/kg, whereas in oil it was relatively low – between 1–2 meq O2/kg. Greater discrepancies were observed in the level of secondary oxidation products. AV of meat lipids was in range between 6 and 19, whereas AV of oil was between 1.4 and 4.6. In oil lipids AV was in every case greater than PV, whereas meat lipids displayed no such correspondence. PV was higher than AV in 10 assortments (Table 7). Measurement of PV and AV made also possible calculation of Totox value that can serve as a conventional measure of fat oxidation. Totox value of meat lipids was, depending on the examined assortment, between 24 and 52, and in oil lipids it never exceeded 10, ranging between 3.5 and 8.5 (Table 7).

Table 7. Oxidation level of meat and oil lipids
 

days

fillet meat

oil

PV

AV

TOTOX

PV

AV

TOTOX

1

15

12.19f

7.28d

31.65c

0.61a

2.58d

3.80a

2

17

13.42g

8.59ef

35.43de

1.38def

1.88b

4.64ab

3

19

10.75e

6.46bcd

27.96b

2.12g

2.87d

7.11d

4

31

15.99h

6.57cd

38.55f

0.52a

4.53g

5.56bc

5

26

16.85h

19.00k

52.70h

1.99g

4.59g

8.57e

6

25

8.45ab

9.00fg

25.90ab

1.11bc

4.14f

6.36cd

7

24

10.40de

6.00bc

26.80ab

1.23c

1.43a

3.89a

8

53

10.98e

4.44a

26.40ab

0.86ab

2.20c

3.91a

9

52

9.37bc

5.30ab

24.04a

1.34cd

1.40a

4.08a

10

52

12.00f

8.95fg

32.95cd

0.94ab

1.70ab

3.58a

11

52

8.00a

19.22k

35.22de

1.86efg

3.52e

7.24d

12

52

9.38bc

17.50j

36.25ef

1.61def

3.31e

6.53cd

13

50

9.16bc

13.30i

31.62c

1.80def

3.93f

7.53de

14

51

9.70cd

7.56de

26.96ab

1.97fg

2.82d

6.76cd

15

28

16.80h

9.87gh

43.47g

0.86ab

2.20c

3.91a

16

30

16.40h

10.50h

43.30g

0.94ab

1.70ab

3.58a

a. b – values represented by the same letters in column are not significantly different from each other with p< 0.05 days – days to the end of product shelf-life
1. 2. 3 ...code of marinades

In general, no correlation between the expiry date of marinades and the level of oxidation of meat lipids was observed. Not every examined assortments relatively near the expiry date displayed a relatively higher level of oxidation.

Sensory quality
Taking consumer desirability into account, it was observed that all of the herring fillets scored at least 5 s.u. in a 10-unit scale (Fig. 1). Assortments 1, 7, 8, 9 and 14 were the most desired, whereas the least desired assortments were 2, 4, 5 and 12. In general all of the examined marinade fillets possessed a characteristic flavor and aroma, typical for the raw material (Fig. 2). In  assortments (2, 4, 5, 11, 12) higher notes of rancid and bitter flavor were observed. (Fig. 3). No correlation between muscle tissue lipids' PV and consumer desirability, characteristic aroma, and rancid and bitter taste descriptors of herring fillets was found. (Table 8). In case of AV and TOTOX a substantial but weak correlation, between 0.61 and 0.75 was observed between these values and rancid and bitter taste descriptors. A relatively high correlation was found between bitter and rancid taste descriptors and consumer desirability (Table 8).

Fig. 1. Consumers desirability for marinades
a, b – values represented by the same letters are not significantly different from each other with p < 0.05

Fig. 2. Intensity of characteristic flavor in marinades
a, b – values represented by the same letters are not significantly different from each other with p < 0.05

Fig. 3. Intensity of bitter and rancid flavor in marinades

Table 8. Correlation as described by Pearsons correlation coefficient (r) between the different measures

measure

PV

AV

Totox

desirability

bitter

rancid

AV

0.02

         

Totox

0.80*

0.62*

       

desirability

-0.42

-0.51

-0.64*

     

bitter

0.46

0.66*

0.76*

-0.76*

   

rancid

0.27

0.67*

0.62*

-0.94*

0.83*

 

typowy

-0.25

-0.60*

-0.55

0.95*

-0.68*

-0.92*

correlation coefficient marked with *are statistically significant (p<0,05)

DISCUSSION

More and more buyers pay greater attention to the quality of consumed products than to their quantity. An accurate interpretation of the results obtained during the research is difficult without the knowledge of geographical origin and the degree of processing of the raw material used for marinating. The only certain fact, as evidenced by product labels, is that the main ingredient of every examined sample is marinated herring fillet, obtained either from the Atlantic herring or its subspecies Baltic herring. Although the profile of Baltic herring lipids is similar to to the profile of sea fish lipids [2,73] muscle tissue of Atlantic herring is richer in lipids (with fat content as high as 30%) [74]. High diversity of fat content in meat, demonstrated in this paper, is probably a result of typical seasonal changes in the amount of meat lipids observed in pelagic fish, which both Atlantic herring and Baltic herring are representatives of [1,4,7,9,42,55,75]. Marinating oil absorbed by meat could have some influence on higher fat content of the latter. Similar high diversity of lipid content in meat part of fish products was observed by Kołakowska et al. [41] and Usydus et al. [78]. Significant differences were observed not only in fat content, but mainly in composition of fatty acids. Composition and FA content of raw material (herring fillets) used for marinating can account for high diversity observed among the examined assortments. Significant discrepancy observed in the percentage of EPA + DHA of meat lipids (10.5–16.7 of the total FA) support this claim, because seasonal changes in LC n-3 PUFA resemble the overall changes of lipid content in muscles [2, 42, 62, 75]. According to Kołakowska et al. [40] changes in n-3 PUFA throughout the year are a result of interaction between the growth cycle of a fish (metabolism of lipids) and its food (availability, competition, and composition). High diversity in the percentage of the sum of C 20:1 and C22:1 acids (4.3–28.4 of the total FA) also indicates that fish used as raw material for fillets consumed varied food, which leads to the conclusion that areas and times of catch were different. According to Lee and Patron [49] and Sargent [66] presence of C 20:1 and C 22:1 acids in lipids of certain sea fish species results from the properties food they consume, which is rich in waxes that contain long-chain alcohols, which in turn are a source of these two acids. It seems unlikely that the observed significant discrepancies in the composition of FA are a result of technological processes. It cannot be definitely ruled out, because of lack of raw material for comparison, however, as Kołakowska et al. [40] states, marinating or even brining processes (assuming that the material for marinating were cured fish) does not involve the risk of reducing the amount of LC n-3 PUFA. Nutritional value of lipids is determined not only by the composition of fatty acids, but also by their ratio [67,70]. Imbalance in the ratio of n-6 and n-3 acids (which should be about 4-5:1) can contribute to the development of cancer and the development of various kinds of inflammation [16]. The ratio of n-6/n-3 acids in the meat of every examined sample was typical for high-fat sea fish products and amounted to 0.4 on average.

FA profile of marinating oil fatty acids was typical for vegetable oils. The proper ratio of n-6/n-3 acids of  2.7 on average was reached, due to the high amount of α-linolenic acid (C 18:3) of n-3 family, which indicates the usage of rapeseed oil. Significant discrepancies observed between various marinating liquids are regular and can be easily explained by the differences in various kinds of rapeseed oil available on the Polish market [63]. Presence in marinating oil of LC n-3 PUFA, fatty acids typical for fish lipids, along with relatively high content of linoleic acid (C18:2) and α-linolenic acid C 18:3 (n-3) in fish meat, indicates that there was an exchange of FA between marinating oil and meat. Such reciprocal exchange of lipids between marinating liquid and fish meat was observed in canned fish by Aubourg et al. [8]. As Tarley et al. [76] state, the rate of lipid migration depend, among other things, on the liquid used in the product. It is commonly known that fish meat has unique nutritional properties; it is worth stressing that these properties arise from the fact that fish meat contains lipids rich in LC n-3 PUFA, which are beneficial in the treatment of ischemic heart disease. According to the International Society for the Study of Fatty Acids and Lipids [29], the minimum daily consumption of EPA and DHA by healthy persons that reduces the risk of developing cardiovascular diseases is at least 500 mg. Additionally, the American Heart Association (AHA), in its 2003 recommendations, suggests that people with known coronary heart disease (CHD) should consume approximately 1 g of EPA and DHA each day [3]. Research done for the purposes of this paper shows that consumption of 18–50g of fish marinade meat meets these recommendations. Some of the literature does not confirm or even denies the positive role of C n-3 PUFA in preventing heart diseases [14], however the estimation of the amount of consumed fish presented in these papers was based on a survey, and, more importantly, lipid oxidation level in consumed fish was ignored, what might have affected the results. Products of lipid peroxidation, mostly aldehydes, can induce changes in blood lipoproteins (LDL), causing development of atherosclerotic plaques and, in turn, development of atherosclerosis and coronary heart disease [17,20,46].

Autoxidation rate of fat in high-fat fish is much higher than that of other fats, because of high amount of unsaturated fatty acids and low amount of natural antioxidants [15,18,38]. The effects of autoxidation most often include deterioration of sensory qualities, decreased nutritional value and increased health hazard connected with consumption of such foodstuffs. These changes affect not only fatty acids, but also other organic compounds such as vitamins or sterols [25,58,79]. An analysis of the oxidation level of lipids confirmed their good quality – Totox value of every sample was lower than 10, which is the widely accepted threshold for good quality of edible oils [33]. Components of Totox value can also serve as indicators of marinade quality. PV of the marinades never exceeded 5 meq O2/kg and AV values never exceeded 8, thus complying with quality requirements of Polish standard [60] and with those of Codex Alimentarius [33]. The oxidation level of meat lipids, several times higher than the oxidation level of oil, and high diversity of the oxidation values were caused by many different factors. As in the case of the composition of fatty acids one of the causes was the quality of lipids in raw material used to produce the intermediate product: marinated fillets. Relatively, for fish lipids, low PV in assortments [6,9,11,12,13,14] suggests that the raw material for marinating was fresh (oxidation level was low) or that primary oxidation products have already decomposed. As it was demonstrated by Kołakowska et al. [41] even lipids of fresh fish contained peroxides and secondary oxidation products. Antioxidative system in fresh fish tissue is still functioning. This system consists of antioxidative enzymes, glutathione, tocopherols, some amino acids and peptides along with a range of other hydrophobic and hydrophilic compounds [26,38]. However, the Totox value of 24 and higher, observed in all marinades, confirms the usual progress of oxidation processes, where initially peroxides form, and later their decomposition gives rise to secondary products of oxidation [22,38]. Oxidation products must have accumulated as early as in the raw material, because assortments 7-12 were analysed 3-5 days after production. Despite the fact that no straightforward correlation was observed between the oxidation level of lipids and the number of days of shelf life left, assortments (5, 15, 16), still with 30 days left until the expiry date, displayed the highest Totox value. It may suggest that secondary oxidation products can, to some degree, form during storage. Therefore, it seems that forming of secondary oxidation products during storage is more of an issue than the process of oxidation that takes place during marinating.

No correlation between consumer desirability, rancid taste descriptor and PV observed during the research is a result of the properties of peroxides and hydroperoxides, compounds that are believed to have no influence on sensory qualities of fat [22,38]. Despite high correlation between PV and rancid taste or total odor, ie. during storage, observed by some researchers [17,22], rancidification was observed with AV both low [77] and high [39]. According to Kołakowska et al. [39], the fishing season has a strong influence on the level of oxidation products required to make the rancid smell evident. In turn according to Sohn et al. [71] there is a correlation between hydroperoxide content in dark fish muscle and a rancid aroma, which is a result of catalytic activity of myoglobin in lipid oxidation.

Peroxides and hydroperoxides are highly volatile compounds, quickly decomposing to secondary oxidation products, mostly aldehydes, ketones and alcohols. It is believed that the resulting low compounds, aldehydes and ketones in particular, are resposible for the characteristic odor and taste of rancid fat [30,47,53,54]. Despite a common correlation between the presence of rancid taste in lipids and their aldehyde content [32,53,54,80] in this research only a weak correlation between these two parameters was found.

No correlation between a relatively high level of secondary oxidation product observed in some marinades and prevalence of a rancid flavor, can be a proof that the analysed  system is relatively complex and that occurrence of such correlations is not necessary [31]. It is possible that if the selected volatile compounds responsible for fish rancidification, such as 1-penten-3-ol, 2,3-pentanedione or 1-octen-3-ol [30] were also examined, using the SPME method, it would confirmation the sensory analysis more accurately than determining the only AV, the value that represents an overall amount of aldehydes and ketones. As Klensporf and Jeleń [37] demonstrate even products with low fat content carbonyl compounds contribute to the development of an unpleasant taste. Interactions between lipid oxidation products and proteins could to some extent affect the perception of rancid taste [61]. Rancid taste can be a result of changes in both lipids or proteins. Acording to Kilara [34] the hydrolysis of protein is often accompanied with flavor defects such as bitterness and off-flavor. Aminoacids, such as valine, isoleucine, phenylalanine, tryptophane, leucines and tyrosines [57] and nucleotide changes that generate hipoxantine [69] can cause rancid taste. Rancid and bitter flavor caused a probably high decrease in quality and in turn in consumer desirability of fillets. Rancidity developed from the autoxidation of lipids leads to unacceptability of the product by the consumers depending on the oxidation level occurred [30]. As Stampanoni [72] points out sensory quality of the product determines  its consumer acceptability.

As Kołakowska et al. [41] point out, marinating processes do not result in an increased amount of oxidation products, even in presence of NaCl, which accelerates this process [5,44,81]. Reduced prooxidative effect of NaCl during marinating  of Pacific saury is explained by Sallam et al. [64] by the influence of  ethanoic acid. It is worth noting that during the research conducted by Kołakowska et al. [42] for each marinating fresh material was used. No significant increase in an oxidation level, basing on TBA, was observed by Kilinc and Cakli [35] during marinating of pilchard, even though the material for marinating was previously in frozen storage. Increased amounts of malonaldehyde were observed by Salam et al. [64] in vacuum-stored marinated Pacific saury and by Kilinc and Cakli [36] in sardine marinated in tomato. It is plausible that presence of additives, such as vegetables and fruits rich in antioxidants, affected the level of oxidation and contributed to discrepancies in oxidation levels of the samples [23,65]. Although assortments 7, 8, 9 and 10 contained onion and were analysed at almost exactly the same time since production, assortment 9, which also contained dried tomatoes, displayed the lowest Totox value. It is possible that simultaneous presence of quercetin from onion and lycopene from tomatoes, after heat treatment, augmented the antioxidative system.

CONCLUSIONS

Despite the fact that many factors, such as: hauling season, method of storing raw material, salting can affect the properties of fillet lipids, it is safe to state that oil marinades available in the domestic market are a rich source of LC n-3 PUFA. Although there were significant differences between examined assortments  in the amount of these acids, PUFA content of every examined product it was high enough to meet the requirements of the Commission Regulation (EU) No 116/2010 for being labeled as a "high omega-3 content" product. When consuming fish products of this kind it is worth bearing in mind that its oxidation level can be relatively high, what can be manifested by a noticeable rancid taste. Nevertheless, consuming the fish itself is recommended, as it is a source of necessary LC n-3 PUFA, what cannot be said of the oil, 70% of which is MUFA.

ACKNOWLEDGEMENTS

Research conducted within the project: "Estimating the amount of essential fatty acids EFA in fish, fish products and seafood available in the domestic market". co-financed by the European Union under the Financial Instrument for Fisheries Guidance within the Sectoral Operational Programme "Fisheries and Fish Processing 2004–2006". Contract number 00057-61535-OR1600019/07.

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Accepted for print: 1.03.2011


Zdzisław Domiszewski
Food Quality Department,
West Pomeranian University of Technology, Szczecin, Poland
Papieża Pawła VI St. 3, 71-459 Szczecin, Poland
Phone: + 48 (091) 449 65 64
email: zdzislaw.domiszewski@zut.edu.pl

Grzegorz Bienkiewicz
Food Quality Department,
West Pomeranian University of Technology, Szczecin, Poland
Papieża Pawła VI St. 3, 71-459 Szczecin, Poland

Dominika Plust
Food Quality Department,
West Pomeranian University of Technology in Szczecin, Poland
Papieża Pawła VI St. 3, 71-459 Szczecin, Poland

Marta Kulasa
Food Quality Department,
West Pomeranian University of Technology in Szczecin, Poland
Papieża Pawła VI St. 3, 71-459 Szczecin, Poland

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