Food Chemistry

1.4 Proteins 87

Fig. 1.58.Production of plasteins with high tyrosine
and low phenylalanine contents. (according to Ya-
mashitaet al., 1976)

Table 1.44.Amino acid composition (weight-%) of
plasteins with high tyrosine and low phenylalanine con-
tents from fish protein concentrate (FPC) and soya pro-
tein isolate (SPI)

Amino FPC FPC- SPI SPI-
acid Plastein Plastein

Arg 7. 05 4. 22 7. 45 4. 21
His 2. 31 1. 76 2. 66 1. 41
Ile 5. 44 2. 81 5. 20 3. 83
Leu 8. 79 3. 69 6. 73 2. 43
Lys 10. 68 10. 11 5. 81 3. 83
Thr 4. 94 4. 20 3. 58 4. 39
Trp 1. 01 2. 98 1. 34 2. 80
Val 5. 88 3. 81 4. 97 3. 24
Met 2. 80 1. 90 1. 25 0. 94
Cys 0. 91 1. 41 1. 78 1. 82
Phe 4. 30 0. 05 4. 29 0. 23
Tyr 3. 94 7. 82 3. 34 7. 96
Ala 6. 27 4. 82 4. 08 2. 56
Asp 11. 13 13. 67 11. 51 18. 00
Glu 17. 14 27. 17 16. 94 33. 56
Gly 4. 42 3. 94 4. 88 3. 89
Pro 3. 80 4. 25 6. 27 2. 11
Ser 4. 59 3. 58 5. 45 4. 67

Fig. 1.59.An outline for two- and single-step plastein

reactions. (according toYamashitaet al., 1979)

Incubation of protein with peroxidase/H 2 O 2 /cate-

chol also results in cross-linking. The reactions in

this case are the oxidative deamination of lysine

residues, followed by aldol and aldimine conden-

sations, i. e. reactions analogous to those cata-

lyzed by lysyl oxidase in connective tissue:

(1.164)

Table 1.45 presents some of the proteins modified

by peroxidase/H 2 O 2 treatment and includes their

ditryrosine contents.

1.4.7 TexturizedProteins......................................

1.4.7.1 Foreword

The protein produced for nutrition in the world

is currently about 20% from animal sources

and 80% from plant sources. The plant proteins

are primarily from cereals (57%) and oilseed

meal (16%). Some nonconventional sources of

protein (single cell proteins, leaves) have also

acquired some importance.