40 1 Amino Acids, Peptides, Proteins
Table 1.19.Occurrence of carnosine, anserine and balenine (%) in meata
Meat Carnosine Anserine Balenine Σb
Beef muscle 0 .2–0. 4
tissue 0 .15–0.35 0.01–0. 05
Beef meat 4 .4–6. 2
extract 3 .1–5. 70 .4–1. 0
Chicken meatc 0 .01–0. 10 .05–0. 25
Chicken meat
extract 0 .7–1. 22 .5–3. 5
Whale meat ca. 0. 3
Whale meat
extract ad 3 .1–5. 90 .2–0. 613 .5–23. 0 16–30
Whale meat
extract be 2 .5–4. 51 .2–3. 0 0–5. 23 .5–12
aThe results are expressed as % of the moist tissue weight, or of commercially
available extracts containing 20% moisture.
bβ-Alanine peptide sum.
cLean and deboned chiken meat.
dCommercial extract mixture of various whales.
eCommercial extract mixture, with sperm whale prevailing.
1.3.4.4 LysinePeptides.........................................
A number of peptides, such as:
(1.81)have been shown to be as good as lysine in rat
growth feeding tests. These peptides substan-
tially retard the browning reaction with glucose
(Fig. 1.9), hence they are suitable for lysine
fortification of sugar-containing foods which
must be heat treated.
1.3.4.5 OtherPeptides..........................................
Other peptides occur commonly and in variable
levels in protein rich food as degradation products
of proteolytic processes.
1.4 Proteins
Like peptides, proteins are formed from amino
acids through amide linkages. Covalently bound
Fig. 1.9. Browning of some lysine derivatives
(0.1 M lysine or lysine derivative, 0.1 M glucose
in 0.1 M phosphate buffer pH 6.5 at 100◦C in sealed
tubes, (according toFinotet al., 1978.) 1 Lys, 2 Ala-
Lys, 3 Gly–Lys, 4 Glu–Lys, 5 Lys)
Gly | Glu|hetero constituents can also be incorporated
into proteins. For example, phosphoproteins
such as milk casein (cf. 10.1.2.1.1) or phosvitin
of egg yolk (cf. 11.2.4.1.2) contain phos-
phoric acid esters of serine and threonine
residues.
The structure of a protein is dependent on the
amino acid sequence (the primary structure)