Degree of unsaturation and polarity of fatty acids

LCSFAs (C16 : 0, C18 : 0) are more non-polar than unsaturated long-chain fatty acids of the C18 family and among these fatty acids the polarity increases as the number of double bonds increases. Among the saturated fatty acids (C8 : 0 . . . C18 : 0), the polarity increases as the chain length decreases. The more non-polar a fatty acid is, the more it relies on an adequate presence of bile salts and phospholipids for adequate emulsification. It has been shown that medium-chain saturated fatty acids (MCSFA) and long-chain unsaturated fatty acids (LCUSFA) can be absorbed in large quantities even in the absence of bile salts (Garret and Young, 1975; Westergaard and Dietschy, 1976). The differences in polarity of fatty acids are reflected by differences in their absorbability. In general figures, absorbability increases in the following order: C18 : 0 < C16 : 0 < C14 : 0 < C18 : 1, C18 : 2, C18 : 3 (Renner and Hill, 1961; Young, 1961; Garret and Young, 1975; Ketels et al, 1987; Blanch et al, 1995; Vila and Esteve-Garcia, 1996a,b; Danicke et al, 1997b). This order is generally at a higher level for fatty acids derived from soybean oil than for beef tallow, and differences in absorbability between particular fatty acids are more pronounced for the latter. Palmitic and stearic acid from soya oil are found to be better absorbable than those originating from beef tallow. It is thought that this is due to the synergistic effects of LCUSFAs, which support the micellar solubilization of LCSFAs. In this respect, monoglycerides or glycerol seem to be necessary for optimized micellar dissolution (Garret and Young, 1975; Sklan, 1979). The synergistic effects of the ratio of unsaturated to saturated fatty acids in relation to fatty acid absorption and ME values of the fats have been described by several regression approaches (e.g. Wiseman and Lessire, 1987; Ketels and De Groote, 1987, 1989; Wiseman and Salvador, 1991). It should be noted, however, that the order of digestibility of fats in addition to the absolute digestibility value might be modified by other factors, such as dietary fat inclusion level (Ketels et al., 1987; Wiseman and Lessire, 1987), age of the birds (Wiseman and Lessire, 1987) and free fatty

Table 9.1. Fatty acid composition of some dietary fat types (%).

Fatty acid

(C-atoms : double bonds)

Lard

Soybean oil

Beef tallow

Linseed

Palm

Maize oil

Coconut oil

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

8

0

2.6

7.5

10

0

3.0

7.0

12

0

0.1

0.1

0.0

0.2

28.4

49.5

14

0

1.3

1.7

0.1

0.1

2.0

4.9

0.8

1.0

12.1

19.5

16

0

21.2

26.6

0.7

13.5

23.7

35.4

5.0

10.0

40.7

48.8

9.4

13.6

8.5

12.8

16

1

2.1

5.3

0.0

0.1

0.1

6.1

0.1

0.1

0.1

0.3

0.1

0.1

18

0

11.1

17.7

1.8

7.4

13.5

36.5

3.1

7.8

3.9

5.2

1.7

6.7

2.0

8.1

18

1

40.3

51.8

19.1

27.3

24.5

46.4

18.2

21.4

36.7

41.6

25.8

30.1

6.0

13.7

18

2

8.0

10.4

44.0

59.4

0.9

5.4

13.9

17.9

7.9

12.7

42.0

58.6

1.5

23.1

18

3

0.1

2.1

3.3

8.2

0.1

1.1

49.4

66.2

0.5

0.5

1.0

1.0

No. of references

7

9

11

4

3

3

5

References used: Young (1961), Veen etal. (1974), Sickinger (1975), Sibbald and Kramer (1978), Wiseman etal. (1986), Ketels etal. (1987), Huyghebaert etal. (1988), Fritsche etal. (1991), Satchithanandam etal. (1993), Blanch etal. (1995,1996), Halle (1996), Vila and Esteve-Garcia (1996a,b), Danicke etal. (1999a).

acid content (Young, 1961; Wiseman et al., 1991; Blanch et al., 1995; Vila and Esteve-Garcia, 1996c).

+1 0

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  • alanna
    What is the degree polarity of fatty acids?
    6 years ago

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