pan-frying with olive oil, pan-frying with soya oil, and roasting. Roasting did not modify the fat content from that of raw samples. Frying increased the fat content 2-fold, with no difference between samples fried with different oils. Total cholesterol oxidized products (COPs) were 0.74, 2.98, 3.35, and 7.38 μg/g fat in raw, fried with olive oil, fried with soya oil, and roasted salmon, respectively, which represent 0.01, 0.08, 0.09, and 0.15% of cholesterol. A significant correlation (r = 0.902, ≤ 0.01) was found between acidity index and total COPs. The most abundant COPs were 7-ketocholesterol, which appeared in all the samples, and cholestanetriol (one of the most citotoxic COP), which appeared only in cooked samples (1.05−1.33 μg/g fat). All cooked samples supplied more ω-6 polyunsaturated fatty acids (PUFAs) than raw samples and showed higher ω-6/ω-3 ratios. Roasted salmon showed the lowest ω-3 content and the highest PUFAs/(SFAs)-C18:0 and MUFAs+PUFAs/(SFAs-C18:0) ratios.
Table 3. Cholesterol oxides levels (µg.g
-1
, dry basis) in raw and grilled
sardine and hake samples.
COPs Sardine Hake
Raw Grilled Raw Grilled
19-OH 15.18 ± 1.2
B
27.69 ± 1.3A
2.16 ± 0.1
b
3.84 ± 0.3
a
24(S)-OH 1.24 ± 0.2
B
3.45 ± 0.6A
0.37 ± 0.03
b
1.19 ± 0.1
a
22(S)-OH 1.37 ± 0.3
B
2.29 ± 0.6A
0.96 ± 0.05
b
1.53 ± 0.7
a
25-OH 1.17 ± 0.2
B
6.48 ± 0.1A
4.49 ± 0.2
b
10.84 ± 1.0
a
25(R)-OH 0.35 ± 0.04
B
0.69 ± 0.01A
0.81 ± 0.01
b
1.29 ± 0.3
a
7-keto 1.31 ± 0.6
B
2.68 ± 0.3A
- 0.66 ± 0.1
a
Tot al 20.62 ± 0.4
B
43.28 ± 0.4A
8.79 ± 0.1
b
19.35 ± 0.4
a
A,B
Mean and relative standard deviation (RSD) of the four analyses in sardine (two
batches in duplicate);
a,b
Mean and relative standard deviation (RSD) of the four analyses
in hake (two batches in duplicate); means in the same letter do not differ significantly
(p > 0.02)
Merlu/colin = hake
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