Effects of pan-frying on PUFA, MUFA and individual lipid content in Spicara smaris

0239–3006/$ 20.00 © 2012 Akadémiai Kiadó, Budapest

Acta Alimentaria, Vol. 41 (1), pp. 33–44 (2012) DOI: 10.1556/AAlim.41.2012.1.5

EffEcts Of pan-frying On pUfa, MUfa and indiVidUaL Lipid cOntEnt in SpIcArA SmArIS

A. Zervoua, v.J. SinAnogloub, g. PAPAdASa, Ν.S. ThomaidiSc, d-m. meimarogloua and S. miniadiS-meimarogloua*

afood chemistry Laboratory, department of chemistry, University of athens, panepistimioupolis Zographou, 15701 athens. greece

binstrumental food analysis Laboratory, department of food technology, technological Educational institution of athens, ag. spyridonos, 12210 Egaleo. greece

cLaboratory of analytical chemistry, department of chemistry, University of athens, panepistimioupolis Zographou, 15701 athens. greece.

(received: 6 april 2010; accepted: 6 april 2011)

The effects of different frying methods (oil free, extra virgin olive oil and sunflower oil pan-fried) on proximate, neutral and polar lipid composition as well as the fatty acid content of Spicara smaris, a fish species commonly consumed by Mediterranean people, were determined. Pan-frying caused insignificant changes in proteins and polar lipids, whereas a significant (P<0.05) decrease in moisture and ash content, and a significant (P<0.05) increase in the neutral lipids and total sterol content could be detected after pan frying in extra virgin olive oil (EVOO) and sunflower oil. The loss of the individual phospholipid content was not significant during the pan-frying process, but its proportion was influenced by the uptake of the culinary fat. The absorption of oil medium in pan-fried, in EVOO, and in sunflower oil samples resulted in an alteration of their fatty acid profiles including a significant (P<0.05) increase of C18:1ω-9 and C18:2ω-6 ratios and a decrease of EPA, DHA percentages as well as of the ω-3/ω-6 ratio. all frying methods affected (p<0.05) lipid quality indices but their values could be considered satisfactory in terms of healthiness. among the fried samples, the oil free fried samples also presented the poorest triglyceride and cholesterol content, and the greatest ω-3/ω-6 ratio, thus, they were found to present the most appropriate frying method for healthy eating.

Keywords: Spicara smaris, pUfa, MUfa, cholesterol, minerals

The beneficial effects of fish consumption are related to the presence of proteins, unsaturated fatty acids, vitamins and minerals. Omega-3 PUFAs, in particular EPA and DHA, are known to diminish heart attack rates, are thought to reduce circulating levels of blood triglycerides, they are beneficial for pregnant women and premature babies, they control rheumatoid arthritics and are also considered to retard some types of cancer and decrease incidents of diabetes mellitus (sidhu, 2003), while reduced levels of these fatty acids have been associated with neurological conditions (arTS et al., 2001). cholesterol also contained in fish is a vital substance for the human body, but it is considered to be detrimental to heart health in high quantities.

Fried foods have become worldwide popular, because frying is a convenient food preparation technique with typical organoleptic characteristics such as colour, flavour and texture (sioen et al., 2006). Oil-free pan-frying is an alternative way of cooking for either people with health problems (high cholesterol levels, high blood pressure, etc.) or for those who desire a healthier diet. Cooking processes increase the susceptibility of ω-3 polyunsaturated fatty acids towards lipid oxidation (al-Saghir et al., 2004) and may modify

* To whom correspondence should be addressed. phone: (30210) 7274486, (30210) 3624870; fax: (30210) 3624870; e-mail: [email protected]

34 ZErVOU et al.: EffEct Of frying On Lipids Of SpIcArA SmArIS

Acta Alimentaria 41, 2012

the cholesterol content as well as the mineral concentrations. Consumers, however, have very little knowledge about nutritive values of fried fish. As fish is a major source of essential fatty acids, proteins and vitamins, its nutritive value can be affected by processing or cooking methods (gladyShev et al., 2006).

picarel (Spicara smaris) is the fifth most consumed fish in Greece. It is a small, inexpensive fish, abundant in the Greek market, which is consumed as whole and it is considered to be among the best sources of ω-3 fatty acids (ZlaTanoS & LASkAridiS, 2007). In order to evaluate the beneficial effects on human health by the consumption of oil free or extra virgin olive oil as well as sunflower oil pan-fried Spicara smaris, the changes on the nutritional quality parameters (proximate composition, neutral and polar lipid content as well as the fatty acid profile and concentrations) were investigated. One of the most important quality parameters of fried food is the amount of fat absorbed during the process. the more amount of fat absorbed is the less compatible with recent consumer trends towards healthier food and low-fat products. Since fish is considered as a major ω-3 fatty acid source in food, the determination of the effects of different frying methods on the fatty acid composition of picarel will provide useful information to consumers, the dieticians, and the food industry, as well as to academic studies concerning nutrient and healthy foods.

1. Materials and methods

1.1. reagents and standards

The lipid standards used as Iatroscan (TLC-FID) standards were: cholesteryl oleate, cholesterol, tristearoyl-glycerol, lauric acid, oleic acid, linoleic acid, 1,2-distearoyl-glycerol, 1-monostearoyl-rac-glycerol, phosphatidylcholine, phosphatidylethanolamine, lyso-phos-phatidylcholine, lyso-phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and sphingomyeline standards of the sigma chemical co (sigma-aldrich company, dorset, great Britain and st. Louis, MO).

Fatty acid methyl esters used as GC standards were: lauric acid M-E, cis-5,8,11,14,17-eicosapentaenoic acid M-E, and cis-4,7,10,13,16,19-docosahexaenoic acid M-E, (purity≥98%) purchased from Sigma Chemical Co (sigma-aldrich company, UK); Matreya Bacterial acid Methyl Esters cptM Mix, catalog no: 1114; supelcotM 37 component faME Mix c4-c24, 100 mg neat, catalog no: 18919-1aMp; supelco pUfa no. 1, Marine source, 100 mg neat, catalog no: 47033.

All solvents used for sample preparation were of analytical grade and the solvents used for Iatroscan (TLC-FID) and GC-FID analyses were of HPLC grade from Merck (Darmstadt, Germany). All reagents used were of analytical grade and they were purchased from Mallinckrodt Chemical Works (St. Louis, MO) and from Sigma Chemical Co (Sigma-Aldrich company, UK).

1.2. Experimental animals – Sampling and sample preparation

Two hundred and forty (240) adult specimens of picarel (Spicara smaris) were collected from the central market of Athens in December. Fish had been caught in the Central Aegean Sea (near Paros Island) and were stored in ice. They were brought to the laboratory, where they were washed with cold water, weighted, measured and immediately processed. The average length and weight were 8.6±1.4 cm/fish and 6.2±3.1 g/fish, respectively.

https://www.researchgate.net/publication/229201379_Seasonal_variation_in_the_fatty_acid_compsition_of_three_Mediterranean_fish-_sardine_Sardina_pilchardus_anchovy_Engraulis_encrasicholus_and_picarel_Spicara_smaris?el=1_x_8&enrichId=rgreq-1ef21209-add7-4c88-842a-606f16035d87&enrichSource=Y292ZXJQYWdlOzIzNDE2ODU3OTtBUzoyMDg2Nzg3NzE3OTM5MjBAMTQyNjc2NDMwNDQ2OA==

ZErVOU et al.: EffEct Of frying On Lipids Of SpIcArA SmArIS


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Picarel (the whole body – muscle tissue, innards, head and bones included – was used) samples were divided into four groups with similar weight. The first group included picarel in the raw state. The other three groups (three repetitions) were pan-fried (85 oc for 5 min) without oil, in extra virgin olive oil and in sunflower oil, respectively. The samples fried in extra virgin olive oil and in sunflower oil were placed on a clean dry grill for 4–5 min, allowing for the excess oil to drain. The used oil was replaced with fresh one after each frying session.

A part of each one of the above-mentioned sample groups was weighed, homogenized in a blender separately for the determination of proximate composition, cholesterol level and fatty acid composition.

1.3. proximate analysis

Moisture content was determined by oven drying at 105±2 ºC to constant weight. Crude protein (N×6.25) was determined according to the Kjeldahl method (A.O.A.C., 1998) and ash was determined by heating in a muffle furnace at 550 ºC to constant weight.

Total lipids (TL) were extracted according to the Bligh and Dyer method (Bligh & dyer, 1959). After phase equilibration, the lower chloroform layer (Total Lipids, TL) was removed and dried in a rotary vacuum evaporator at 32 oC. The extracted lipids were redissolved in chloroform/methanol (9:1, v/v), containing t-butyl-hydroquinone (0.1%) as an antioxidant and finally stored at 0 oC until used. Afterwards, representative aliquots of all of the above-mentioned samples were evaporated in pre-weighed vials to constant weight to determine the lipid content.

1.4. Iatroscan analysis of neutral and polar lipids

Neutral and polar lipids were determined according to the procedure described by sinAnoglou and co-workers (2011).

1.5. cholesterol determination

Cholesterol was determined according to the procedure described by naeemi and co-workers (1995), modified by andrikoPouloS and co-workers (2003).

1.6. Gas chromatography analysis of fatty acid methyl esters

Fatty acid methyl esters (FAME) of total lipids were prepared according to the procedure described by sinAnoglou and MiniAdiS-Meimaroglou (1998). Both quantitative and qualitative analyses were performed according to the procedure described by sinAnoglou and co-workers (2011).

1.7. Indices calculations

The atherogenic index (AI) and thrombogenic index (TI) were calculated according to the formulas proposed by UlbrichT and souThgaTe (1991):

AI = (12:0+14:0+16:0)/(ω-3PUFA+ω-6PUFA+MUFA) and TI = (14:0+16:0+18:0)/(0.5MUFA+0.5ω-6PUFA+3ω-3PUFA+ω-3PUFA/ω-6 PUFA).

The cholesterol index (CI) was calculated according to the ZilverSmiT (1979) formula: ci = 1.01 (g of sfa 100 g–1 of fresh matter - 0.5 × g of pUfa 100 g–1 of fresh matter) + (0.06 × mg of cholesterol 100 g–1 of fresh matter), while the cholesterol-saturated fat index (CSI) was



calculated according to the formula proposed by connor and co-workers (1986): CSI = (1.01 × g of sfa 100 g–1 of fresh matter) + (0.05 × mg of cholesterol 100 g–1 of fresh matter).

1.8. Statistical analysis

Measurements were obtained in triplicate and values were averaged and reported along with the standard deviation (SD). All data concerning lipid and fatty acid composition were analysed with one-way ANOVA post hoc tests and pairwise multiple comparisons were conducted with the Tukey’s honestly significant difference test. Possibilities less than 0.05 were considered as statistically significant (P<0.05). All statistical calculations were performed with the SPSS 10.0 (Chicago, IL, USA) statistical software for Windows.

2. Results and discussion

2.1. proximate analysis

Proximate composition of the raw and pan-fried (without oil and in two different oils) picarel is given in Table 1. The frying procedure has modified the proximate composition of the examined fish. Moisture and ash content did not appear to have changed significantly (p>0.05) after pan-frying without oil, while they were found to decrease considerably (p<0.05) after pan-frying in either extra virgin olive oil or sunflower oil. In comparison with other fish species from the literature (MiniAdiS-Meimaroglou et al., 2007, tZikAS et al., 2007), raw picarel had a higher ash content since the whole body was used for the ash determination.

Table 1. Proximate composition (g/100 g wet matter and g/100 g dry matter) for raw and pan-fried Spicara smaris

Raw Pan-fried without oil

pan-fried in EVOO pan-fried in sunflower oil

Moisture g/100 g wet matter

72.71±0.64a 71.53±0.69a 63.62±0.75b 61.98±0.67c

Protein g/100 g wet matter 17.01±0.58a 18.17±0.41a 18.52±0.62a 17.37±0.74a

Ash g/100 g wet matter 4.19±0.19a 4.15±0.14a 3.25±0.21b 3.29±0.18b

Fat g/100 g wet matter 1.61±0.03a 1.42±0.03b 10.57±0.08c 11.79±0.07d

protein g/100 g dry matter 62.33±0.76a 63.82±0.83a 50.91±0.73b 45.69±0.56c

ash g/100 g dry matter 15.35±0.45a 14.58±0.39b 8.93±0.28c 8.65±0.32c

fat g/100 g dry matter 5.90±0.19a 4.99±0.21b 29.05±0.87c 31.01±0.75d

Means in the same row with different letters differ significantly (P<0.05).

the oil-free pan-fried Spicara smaris compared to the raw one had a similarly high protein to fat ratio, while the same ratio was very low after frying in two different kinds of oil. This was due to the fact that pan-frying with or without oil had no significant impact (p>0.05) on the protein content (expressed on a wet weight basis), as opposed to the lipid content. The latter has slightly decreased after pan-frying without oil, but significantly (p<0.05) increased after frying in extra virgin olive or sunflower oil, due to oil migration from the frying medium to the fish. Pan-frying with sunflower oil seemed to increase the mass transfer between the picarel and frying medium more than the samples cooked with



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extra virgin olive oil did. When the data were expressed on a dry matter basis, the fat content of oil pan-fried picarel was significantly higher (fivefold) than that of the raw one (Table 1). The results suggest that the balance of the exchange between the picarel-fat and the bath oil was positive, with more fat being absorbed from the picarel than being released by them. Similar results were found for silver catfish (rhamdia quelen) fillets fried in soybean, canola and hydrogenated vegetable oil (Weber et al., 2008) and for sardines fried in sunflower oil (cAndelA et al., 1998). This is explained by the fact that lean fish, such as picarel, tend to absorb higher quantities of oil while frying than the more fatty ones (KAlogeroPouloS et al., 2004; gArcíA-ariAS et al., 2003). gokoglu and co-workers (2004) reported that the absorption of fat through frying also caused an increase of dry matter. fat increase can be due to the oil penetration into the food after water has been partially lost by evaporation (sAguy & dAnA, 2003).

2.2. Neutral and polar lipids in raw and fried picarel

Neutral lipids (NL) and polar lipids (PL) of raw and pan-fried picarel whole body were identified and quantified in the TL extract using TLC-FID (Table 2). The raw picarel NL fraction mainly consisted of triglycerides (TG) followed by sterols, free fatty acids (FFA), diglycerides (DG) and monoglycerides (MG). TG content decreased significantly (P<0.05) after pan-frying without oil, compared to the raw picarel, due to their partial loss during pan-frying. TG content increased significantly (P<0.05) in the pan-fried in extra virgin olive and sunflower oil picarel NL, compared to the raw picarel NL due to the oil absorption during frying.

Concerning the raw picarel PL, phosphatidylcholine (PC) seemed to have the highest content followed by phosphatidylethanolamine (PE), sphingomyelin (Sphm), phos phat-idylserine – phosphatidylinositol (ps-pi) and lyso-phosphatidylcholine (l-pc). pc and pE content increased significantly (P<0.05) in oil-free pan-fried and decreased in pan-fried in EVOO and sunflower oil picarel PL.

from a nutritional perspective, the quantitative neutral and polar lipid composition, expressed as mg/100 g of edible portion, was determined in raw and pan-fried picarel (Table 3). Pan-frying with EVOO and sunflower oil picarel had significantly (P<0.05) higher tg, FFA, DG and MG concentrations than the raw and oil free pan-fried fish. Pan-frying of picarel without oil caused a decrease of the total sterol and cholesterol contents, which was insignificant (P>0.05) according to the statistical analysis (table 3). total sterol content significantly (P<0.05) increased in pan-fried in EVOO and sunflower oil picarel, whereas the cholesterol content increase was insignificant. This result suggested that the frying procedure in two different oils increased significantly (P<0.05) the phytosterol content due to vegetable oil absorption from the bath. Nevertheless, there are cases where, according to other authors, frying resulted in either an increase or decrease of the cholesterol content (KAlogeroPouloS et al., 2004) which can be due either to the sort of fat used or the fat content of the fish itself. After having taken into consideration the cholesterol values (Table 3), their contribution to the recommended maximum cholesterol intake can be calculated through the consumption of 100 g pan-fried with or without oil picarel. Their contribution represented the 36.3%, 46.0% and the 45.5%, respectively, of the recommended maximum cholesterol intake (300 mg per day) by the European Olive Oil Medical Information and the World Health Organization (WHO), (Jiménez-colmenero et al., 2001) or the 50.5%, 64.4% and 63.8%, respectively, of the dietary cholesterol intake (214 mg per day) for Greeks (KAlogeroPouloS et al., 2004).



Table 2. Neutral and polar lipid profile (% of TL) of the raw and pan-fried whole body picarel

Lipid classes Raw Oil-free pan fried pan fried in EVOO

pan-fried in sunflower oil

neutral lipids

tg 26.75±1.04a 17.15±0.70b 86.44±0.66c 87.40±0.64c

ffa 0.81±0.02a 1.22±0.03b 1.24±0.01b 1.25±0.01b

total sterol 7.57±0.29a 8.12±0.38a 1.41±0.02b 1.37±0.03b

cholesterol 7.38±0.26a 7.67±0.34a 1.30±0.02b 1.16±0.02c

dg 0.46±0.02a 0.58±0.03b 0.56±0.02b 0.54±0.03b

Mg 0.21±0.01a 0.32±0.01b 0.34±0.01bc 0.36±0.01c

polar lipids

pE 14.07±0.29a 15.88±0.28b 2.18±0.24c 1.94±0.31c

pi + ps 1.49±0.03a 1.73±0.03b 0.23±0.03c 0.21±0.02c

pc 44.41±0.95a 50.29±0.78b 6.94±0.23c 6.33±0.27d

sphm 3.18±0.07a 3.56±0.06a 0.49±0.02b 0.45±0.03b

l-pc 1.05±0.02a 1.15±0.02a 0.17±0.01b 0.15±0.01b


Table 3. Neutral and polar lipids composition (mg/100 g edible portion) of the raw and pan-fried whole body picarel

Lipid classes Raw Oil-free pan fried pan fried in EVOO


neutral lipids

tg 430.68±22.10a 243.53±10.11b 9136.71±36.95c 10304.46±41.27d

ffa 13.04±0.57a 17.32±0.40b 131.07±6.65c 147.38±5.88d

total sterol 121.88±8.03a 115.30±5.78a 149.04±7.62b 161.52±6.29b

cholesterol 118.90±8.21ab 108.91±5.33a 137.93±12.90b 136.48±10.42b

dg 7.41±0.82a 8.24±0.79a 59.19±2.61b 63.67±2.24b

Mg 3.36±0.27a 4.54±0.38b 35.94±1.13c 42.44±1.57d

polar lipids

pE 226.53±10.76a 225.50±12.59a 230.43±14.16a 228.73±13.62a

pi + ps 24.00±0.47a 24.56±0.63a 24.31±0.54a 24.76±0.42a

pc 715.00±31.67a 714.12±28.51a 733.56±33.26a 746.31±35.32a

sphm 51.20±1.20a 50.55±1.13a 51.79±1.54a 53.06±1.33a

l-pc 16.91±0.84ab 16.33±0.56a 17.97±0.71b 17.68±0.62b


in spite of the different (p<0.05) percentages of individual PL (% of TL) in all picarel samples, their concentrations were found quite similar (Tables 2 and 3). This result suggested that the frying procedure (without oil and in two different oils) did not affect the individual PL content in the edible portion of the fish. Moreover it seems that the picarel phospholipids remained unchanged after frying, due to the fact that these lipids make up the cell membrane structure. PC was established as an essential nutrient with recommended daily intake (RDI) of 550 mg for men and 450 mg for women (Mcnamara & theSmar, 2005). from the above



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results it seems that pan-frying picarel is an excellent source of dietary pc, providing more than 700 mg of PC per 100 g of edible portion covering the 100% percentage of the PC-RDI in the human diet.

2.3. changes in the fatty acid pattern

The fatty acid profiles of total lipids in the whole body of raw and pan-fried without oil and in different oils picarel are shown in Table 4. Thirty-eight saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids were identified in all studied samples. The main saturated fatty acids of raw picarel were found to be palmitic acid (C16:0) and stearic acid (C18:0), the main monounsaturated was oleic acid (C18:1 ω-9) and the main polyunsaturated fatty acids were EPA (C20:5 ω-3) and DHA (C22:6 ω-3). Concerning the sums of the fatty acids ΣPUFA occurred in the highest percentage followed by ΣSFA, while ΣMUFA seemed to have a lower percentage (Table 4).

in the oil-free pan-fried picarel the percentages of c16:0 and c18:0 appear to have increased significantly (P<0.05) whereas the C18:1ω-9 percentage has only slightly increased (Table 4). On the contrary, the percentages of EPA and DHA decreased significantly (P<0.05) resulting in no significant changes in the ΣMUFA while the ΣSFA increased in a percentage similar to the one by which ΣPUFA had decreased after oil-free pan-frying. The above results are comparable to the ones from the literature, concerning different fish species after various thermal treatments, such as grilling, boiling, baking and microwaving (yAnAr et al., 2007).

The fatty acid composition of picarel was greatly affected by pan-frying in extra virgin olive oil. In particular, the major change was the increase in the percentage of oleic acid, since this is the major fatty acid of olive oil (Table 4). The great increase in the percentage of C18:1ω-9 led to lower C16:0, C18:0, EPA and DHA percentages. These changes brought along differences in the sums of fatty acids. Contrary to raw and oil free pan-fried picarel, ΣMUFA seemed to prevail in the fatty acid profile of the pan-fried in extra virgin olive oil fish, while the ΣPUFA appeared to have a lower percentage than ΣSFA. Similar changes in the oleic acid percentage were observed in various fish species from the Mediterranean Sea after-frying in virgin olive oil (KAlogeroPouloS et al., 2004), while marginally significant changes were observed in salmon after frying in olive oil (al-saghir et al., 2004).

Pan-frying in sunflower oil also brought along changes in the fatty acid profile of picarel, the greatest change was the increase of ΣPUFA, due to C18:2ω-6 absorption from the frying medium (Table 4). A significant increase in the linoleic acid content after frying in sunflower oil of sea bass fillets was also reported in the literature (yAnAr et al., 2007). furthermore, an increase was observed in the percentage of C18:1ω-9 – the second most abundant fatty acid in sunflower oil – which caused an increase in the sum of ΣMUFA. These changes led to a reduction of the C16:0, C18:0, EPA and DHA percentages as well as in the sum of SFA.

In agreement with gArcíA-ariAS and co-workers (2003), the changes were not homogeneous for the different fatty acids and were dependent on the composition of the frying oil. Specifically, the samples fried in EVOO had significantly (P<0.05) higher MUfa percentage and lower SFA and PUFA percentage than the raw picarel while the samples fried in sunflower oil had significantly (P<0.05) higher MUFA and PUFA percentage and lower SFA than the raw one. The above results are in agreement with literature data, which support the view that during frying the fatty acid composition of relatively lean fish tends to become similar to the one of the frying oil (KAlogeroPouloS et al., 2004; sioen et al., 2006). agren and HAnninen (1993) reported that the additional oil mainly determines the fa composition



Table 4. Fatty acids composition (% w/w) in total fatty acids of the raw and pan-fried whole body Spicara smaris

fatty acids Raw Oil-free pan fried

pan-fried in EVOO pan-fried in sunflower oil

c14:0 2.84±0.03a 2.61±0.01b 0.23±0.01c 1.45±0.01dc14:1 0.18±0.01a 0.16±0.01a 0.01±0.00b 0.07±0.00ciso-c15:0 0.12±0.01a 0.07±0.01b 0.01±0.00c 0.04±0.00dc15:0 0.88±0.01a 0.89±0.01a 0.05±0.00b 0.29±0.01cC15:1 ω-5 0.11±0.01a 0.11±0.01a 0.01±0.00b 0.05±0.00cc16:0 19.13±0.16a 23.11±0.07b 11.76±0.04c 12.04±0.03ciso-c16:0 0.85±0.01a 0.52±0.01b 0.10±0.00c 0.43±0.01dC16:1 ω-9 cis 1.72±0.03a 1.77±0.03a 0.17±0.01b 1.73±0.02aiso-c17:0 1.56±0.01a 1.04±0.01b 0.06±0.00c 0.45±0.03dcyclo-c17:0 0.17±0.01a 0.09±0.01b 0.02±0.00c 0.06±0.00dc17:0 1.69±0.01a 1.93±0.02b 0.13±0.01c 0.57±0.01dC17:1 ω-7 cis 0.83±0.01a 0.36±0.01b 0.10±0.01c 0.23±0.01dc18:0 6.56±0.01a 8.22±0.09b 0.67±0.01c 5.74±0.06dC18:1 ω-9 cis 7.48±0.01a 8.33±0.08b 65.04±0.65c 19.60±0.20dC18:1 ω-7 cis 1.72±0.01a 1.16±0.01b 10.31±0.06c 0.57±0.01dC18:2 ω-6 cis 1.90±0.01a 1.91±0.02a 5.92±0.06b 38.86±0.36cC18:3 ω-6 cis 0.33±0.01a 0.37±0.01b 0.15±0.01c 0.13±0.00cC18:3 ω-3 cis 0.61±0.01a 0.55±0.01b 0.05±0.00c 0.20±0.00dC18:4 ω-3 cis 1.32±0.01a 0.69±0.01b 0.07±0.00c 0.40±0.00dc19:0 0.41±0.01a 0.20±0.01b 0.02±0.00c 0.10±0.00dc20:0 0.12±0.01a 0.10±0.01a 0.52±0.01b 0.31±0.01aC20:1 ω-9 cis 0.82±0.01a 0.97±0.01b 0.33±0.01c 0.50±0.01dC20:2 ω-6 cis 0.35±0.01a 0.30±0.01b 0.03±0.00c 0.12±0.01dC20:3 ω-6 cis 0.13±0.01a 0.13±0.01a 0.02±0.00b 0.08±0.00cC20:4 ω-6 cis 1.33±0.01a 1.49±0.03b 0.12±0.01c 0.38±0.01dC20:3 ω-3 cis 0.11±0.01a 0.09±0.01a 0.01±0.00b 0.04±0.00dc21:0 0.46±0.03a 0.42±0.02a 0.03±0.00b 0.12±0.01cC20:5 ω-3 cis 7.06±0.02a 6.73±0.09b 0.65±0.01c 2.36±0.05dc22:0 0.22±0.01a 0.18±0.01b 0.20±0.01ab 0.55±0.01cC22:1 ω-9 cis 0.10±0.01a 0.10±0.01a 0.01±0.00b 0.05±0.00cC22:2 ω-6 cis 0.16±0.01a 0.14±0.01a 0.01±0.00b 0.01±0.00bc23:0 0.46±0.01a 0.32±0.01b 0.04±0.00c 0.13±0.00dC22:4 ω-6 cis 0.17±0.01a 0.09±0.01b 0.02±0.00c 0.04±0.00dC22:5 ω-6 cis 0.37±0.01a 0.15±0.01b 0.04±0.00c 0.13±0.00dC22:5 ω-3 cis 1.37±0.01a 0.81±0.01b 0.08±0.00c 0.40±0.01dc24:0 0.16±0.01a 0.36±0.01b 0.03±0.00c 0.32±0.01dC22:6 ω-3 cis 35.43±0.24a 32.79±0.59b 2.91±0.03c 11.26±0.19dC24:1 ω-9 cis 0.77±0.03a 0.74±0.02a 0.07±0.00b 0.19±0.00cΣω:0 (SFA) 35.63±0.06a 40.06±0.05b 13.87±0.02c 22.61±0.03dΣω:1 (MUFA) 13.73±0.02a 13.70±0.03a 76.05±0.38b 22.98±0.16cΣω:n (PUFA) 50.64±0.13a 46.24±0.16b 10.08±0.01c 54.41±0.28dΣω:3 45.90±0.18a 41.66±0.23b 3.77±0.01c 14.66±0.16dΣω:6 4.74±0.12a 4.58±0.09a 6.31±0.03b 39.75±0.31cω-3/ω-6 9.68±0.03a 9.10±0.05b 0.60±0.01c 0.37±0.06dUfa/sfa 1.80±0.07a 1.49±0.03b 6.20±0.11c 3.42±0.02d

Different letters within a row denote significant differences (P<0.05)



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of small and lean fish and that its effect decreases with the increasing lipid content of the fish. As the fish fat content increase, an exchange of fat between the fish and the frying oil takes place, which results in the decrease of SFA and PUFA content and the increase of MUFA (gArcíA-ariAS et al., 2003).

The UFA/SFA ratio was significantly (P<0.05) different among the samples pan-fried without oil and in the two types of oil (Table 4). Thus, UFA/SFA ratio showed a significant (p<0.05) decrease after pan-frying without oil while a significant increase was observed after pan frying in extra virgin olive as well as sunflower oil, since there was an increase in the percentage of unsaturated fatty acids due to oleic and linoleic acid absorption from the frying medium, respectively. The above results are in agreement with Weber and co-workers (2008) who reported that silver catfish fillets fried in canola and soybean oil had an increase in the UFA/SFA ratio when compared to other samples.

The ω-3/ω-6 ratio is considered to be an important nutritional index since a lack of balance of the polyunsaturated fatty acids in the diet is responsible for hypertension, disorders of the immune system, inflammation, depression and certain disturbances of neurological functions. In the present study the ω-3/ω-6 ratio was found to decrease slightly but significantly (p<0.05) in oil free pan-fried and dramatically in pan-fried in the two different oils picarel (Table 4). The addition of frying oil did negatively affect the ω-3/ω-6 ratio due to the presence of ω-6 fatty acids in EVOO and sunflower oil. Other authors also reported a significant (p<0.05) decrease of ω-3/ω-6 ratio in humpback salmon during frying in sunflower oil from about 16 to 2.2 (gladyShev et al., 2006) as well as in salmon during frying from about 8.3 to 1.4, in mackerel from 8.3 to 0.2 and in sardines from 14.4 to 0.2 (cAndelA et al., 1998).

the decrease in the amount of individual Ufa expressed as mg/100 g of edible portion after pan-frying without oil can be explained by a fat loss from the picarel (Table 5). The increase in the amount of individual sfa, MUfa and pUfa after pan-frying in EVOO and in sunflower oil can be explained on the one hand by a water loss and on the other hand as the result of absorption of the fatty acids from the oil used for frying. yAnAr and co-workers (2007) reported that changes occur from the loss of fish lipids into the frying oil, although, not all of the fatty acid exchanges occur in equal proportions. comparison of per cent levels of essential pUfas may result in a misleading notion concerning the nutritive value. the reduction in the percentage of EPA and DHA may have a great impact on human health. These fatty acids play an important role in the human diet since the role of ω-3 in the amelioration of cardiovascular disease is widely known. Further on, there is a consensus that EPA and DHA must be considered as essential fatty acids since the degree of conversion of α-linolenic acid to EPA and DHA in the body is unreliable and restricted (arTS et al., 2001). In the present study, raw picarel had the highest levels of EPA+DHA (42.49%, calculated from Table 4), while pan-fried in EVOO picarel had only 3.56%. On a weight basis, it was observed that raw and pan-fried samples presented equal quantities of these two acids (Table 5). In accordance with our results al-saghir and co-workers (2004) reported that no change was found in the omega-3 fatty acid content with cooking methods and no difference between frying with or without oil. Therefore, a comparison of EPA+DHA contents in raw fish species, especially when expressed as per cent levels only, may not provide explicit information about the nutritive value of these species after cooking (gladyShev et al., 2007).



Table 5. Main fatty acids content expressed as mg/100 g edible portion of the examined raw and pan-fried Spicara smaris whole body

fatty acids Raw Oil-freepan-fried

pan-fried inEVOO


c16:0 158.7±0.5a 176.4±0.5b 996.5±3.0c 296.6±1.6d

c18:0 54.442±0.575a 63.21±0.67b 57.04±0.60c 141.4±1.5d

C18:1 ω-9 cis 62.09±0.62a 63.28±0.63a 5511±55b 482.8±3.9c

C18:1 ω-7 cis 14.29±0.13a 8.815±0.023a 874.6±5.3b 14.04±0.13a

C18:2 ω-6 cis 15.80±0.15a 14.54±0.14a 501.6±4.8b 957.2±6.8d

C20:5 ω-3 cis 58.60±0.82a 51.89±0.73b 55.25±0.35c 58.13±0.45a

Σω:0 (SFA) 295.6±0.3a 304.4±0.2b 1169±3c 556.9±1.1d

Σω:1 (MUFA) 113.9±0.5a 104.1±0.4b 6413±31c 566.1±2.1d

Σω:n (PUFA) 420.1±3.1a 351.4±2.5b 850.1±3.7c 1340±13d

Σω-3 (PUFA) 380.8±6.4a 318.1±5.4b 318.0±3.0b 361.1±5.4c

ΣFA 829.6±9.5a 759.9±8.3b 8433±74c 2463±22d

Different letters within a row denote significant differences (P<0.05).

After having combined the values for ω-3 PUFA in the pan-fried fish (Table 5) and calculated the covering percentage of the recommended daily allowance/intake (RDA/RDI) for adolescents and adults proposed by Health and Welfare Canada (1.1–1.8 g per day) as well as the one proposed by the U.K. Department of Health (250 mg marine ω-3 PUFA per day), it appears, that the consumption of 100 g of the oil-free pan-fried, pan-fried in extra virgin olive oil or in sunflower oil fish, covers a satisfactory percentage (17.7–28.9%, 17.6–28.8% and 20.0–32.8%, respectively and 127%, 127% and 144%, respectively) of the ω-3 pUfa rda/rdi in the human diet.

2.4. Indices

The atherogenic (AI) and thrombogenic (TI) indices (Table 6) were calculated in order to evaluate the atherogenic and thrombogenic potential of raw and pan-fried picarel, while their hypercholesterolemic-atherogenic potential, which depends on cholesterol content and fatty acid composition, was assessed via the TI, cholesterol (CI) and cholesterol-saturated fat (CSI) indices calculation (Table 6). The CI was developed (ZilverSmiT, 1979) in order to show the absolute effect of individual food servings on serum cholesterol (low cholesterol content has beneficial effects on the human health), while the CSI (connor et al., 1986) may be used to compare different foods and recipes and to evaluate daily intake quickly and easily (KAlogeroPouloS et al., 2004). The AI of raw picarel (0.34±0.01) seemed to increase significantly (P<0.05) in oil-free pan-fried picarel (0.43±0.01), while an almost twofold decrease was observed after pan-frying in extra virgin olive oil and in sunflower oil. The TI was also found in low levels in raw picarel (0.18±0.01), while it increased significantly (p<0.05) in pan-fried samples (ranged between 0.24±0.01–0.25±0.01). However, both AI and TI remained lower than one (which is the appropriate value for a healthy diet) in all fried samples. The CI and CSI indices did not change significantly (P>0.05) in oil-free pan fried picarel (6.66±0.32), compared to the raw one, while they seemed to increase significantly (p<0.05) in pan-fried in extra virgin olive oil and in sunflower oil picarel (9.03±0.77 and



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8.16±0.74, respectively). These values for CI and CSI of pan-fried with or without oil fish are comparable with those reported in the literature (connor et al., 1986; sanchez-MuniZ et al., 1992).

Table 6. atherogenic (ai), thrombogenic (ti), cholesterol (ci) and cholesterol-saturated fat (csi) indices in the raw and pan-fried Spicara smaris

treatment ai ti csi ci

Raw 0.34±0.01a 0.18±0.01a 6.24±0.41a 7.22±0.49ac

Pan-fried without oil 0.43±0.01b 0.24±0.01b 5.75±0.27b 6.66±0.32a

pan-fried in extra virgin olive oil 0.14±0.01c 0.24±0.01b 8.07±0.65c 9.03±0.77b

Pan-fried in sunflower oil 0.17±0.01d 0.25±0.01b 7.47±0.64c 8.16±0.74bc

Different letters within a row column denote significant differences (P<0.05)

3. Conclusions

all frying methods evaluated caused a charge in the proximate composition, individual neutral lipid content and fatty acid profile of picarel. Changes in proximate composition were more prominent in pan-fried in EVOO and sunflower oil. Oil-free pan-fried picarel presents a healthier lipid profile in terms of the ω-3/ω-6 ratio, PUFA and MUFA, preserving the differences in the initial FA profile of the picarel.

The fatty acid compositions of pan-fried in EVOO and sunflower oil picarel tended to become similar to those of the frying oil used, suggesting that the influence of oil is more important to the final composition of the fish than lipid composition in the raw state. Thus, the frying process in oil reduced the proportion of sfa and increased the proportion of MUfa when olive oil was used, whereas it increased the proportion of PUFA in picarel fried in sunflower oil. From a nutritional point of view, frying in virgin olive oil had more beneficial properties than in sunflower oil due to the lower level of TG and total sterol content as well as the higher ω-3/ω-6 ratio.

*This research was supported in part by the Special Research Account of National and Kapodistrian University

of Athens under the project with number 70/4/3343.

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Documents

Effects of pan-frying on PUFA, MUFA and individual lipid content in Spicara smaris