Table 1 FTIR peak assignment for okra seed flours, protein isolate and enzymatic hydrolysates

Intermolecular bonded O-H stretching; N-C stretching

3419.90

3419.90

3419.98

3419.98

3417.98

3417.98

3416.05

Protein and poly-hydroxyl compounds

3029–3639 (3334)

CH2 Stretching asymmetric

N.D.

N.D.

N.D.

N.D.

2962.76

2964.69

2917.46

Alkane compounds

2960

O-H stretching; CH2 stretching symmetric

2887.53

2892.36

2890.425

2892.36

N.D.

N.D.

N.D.

Methoxy methyl ether compound

2890

N-H stretching

2359.02

2359.02

2360.95

2360.95

2359.02

2359.02

2362.88

Amino acid component

2332–2359 (2344)

C=O stretching of esters

1745.64

1740.64

N.D.

N.D.

N.D.

N.D.

N.D.

Triglycerides

1763–1712 (1737.5)

C=O stretching, C=N stretching

N.D.

1637.62

1637.62

1647.62

N.D.

N.D.

1647.62

Protein amide I band

1620–1650 (1635)

N-H bending; C-N, stretching

1541.18

1541.18

1541.18

1541.18

1541.18

1541.18

1541.18

Protein amide II band

1481–1585 (1533)

CH2 bending asymmetric; CH3 bending asymmetric

1456.30

1456.3

1458.23

1456.3

N.D.

N.D.

N.D.

Protein and fats

1425–1477 (1451)

C-O stretching symmetric of COO- groups of carboxylates

1379.22

1384.94

1484.15

1384.94

1404.22

1402.3

1406.15

Carboxylic acid

1357–1423 (1390)

P=O stretching asymmetric; C-N stretching amine

1277.88

1277.88

1278.85

1279.81

1276.92

1286.57

1286.57

Nucleic acid

1191–1356 (1273.5)

C=N stretch (amide III),

N.D.

N.D.

1159.26

N.D.

1153.47

N.D.

N.D.

Tertiary amine

1210–1150 (1170)

C=N stretch (amide I),

1066.67

1076.32

1037.74

1065.701

1074.39

1078.24

1056.07

Primary amine

1090–1020 (1055)

C-Cl stretch,

719.47

N.D.

719.47

N.D.

N.D.

773.48

N.D.

Aliphatic Chloro-compound

800–700 (750)

C-Br stretch

643.28

643.28

643.28

643.28

623.03

613.38

609.53

Aliphatic bromo compounds

700–600 (750)