Dairy Ingredients for Food Processing

Enzyme-modifi ed Dairy Ingredients 327

(f61 to 68) disulfi de bound to f75 to 80

(Chatterton et al., 2006 ). These peptides were

mostly active against Gram - positive bacteria;

however, weaker effects were observed with

Gram - negative bacteria. Although pepsin did

not release any antibacterial peptides in one

study, a different study indicated that both

pepsin and trypsin released peptides from

α - la, which inhibited the growth of E. coli

JM103. The peptide concentration was

25 mgmL _ 1, whereas unhydrolyzed α - la did

not inhibit the growth at a concentration of

100 mgmL _ 1. Peptides released from whey

proteins and their bioactivities are shown in

Table 12.3 and commercially available whey

peptide products are shown in Table 12.4.

Ingredients Derived from Lipolysis

A majority of the fl avor compounds are

derived from lipids or are a result of interac-

tions of lipolysis and proteolysis products.

Most fl avor - impact compounds are also lipid

soluble. Recent trends in healthy foods have

created markets for low - and nonfat products

in the United States. Nonfat products do not

have enough lipids to act as effective fl avor

carriers. The time of onset of fl avor release

and the duration of fl avor perception are

potential as a natural antihypertensive agent
for inclusion in foods.
Peptide fragments of β - lg, generated
through the action of alcalase, pepsin, or
trypsin, have been shown to be bacteriostatic
against E. coli and against pathogenic strains
of E. coli, Bacillus subtilis , and Staphylococcus
aureus (Meisel, 1998 ).
Alphalactalbumin ( α - la) is the next most
predominant protein in whey. The peptide
with the amino acids sequence Tyr - Gly - Leu -
Thr (f50 to 53), released from α - la by pepsin
treatment, was shown to inhibit ACE; the
accuracy of the last amino acid (Thr) is
uncertain. This peptide has been termed α -
lactophorin. Interestingly, proteolytic frag-
ments of this peptide, i.e., the dipeptides
Tyr - Gly (f18 to 19 and f50 to 51) and Leu -
Phe (f52 to 53), were also observed to have
an inhibitory effect. Trypsin treatment of α - la
has been shown to release two antibacterial
peptides, Glu - Gln - Leu - Thr - Lys (f1 to 5) and
Gly - Tyr - Gly - Gly - Val - Ser - Leu - Pro - Glu - Trp -
Val - Cys - Thr - Thr - Phe (f17 to 31) disulphide -
bonded to Ala - Leu - Cys - Ser - Glu - Lys (f109
to 114). Treatment using another intestinal
enzyme, chymotrypsin, resulted in one anti-
bacterial peptide, namely, Cys - Lys - Asp - Asp -
Gln - Asn - Pro - His - Ile - Ser - Cys - Asp - Lys - Phe

Table 12.3. Peptides derived from whey proteins and their bioactivity.

Precursor protein Fragment Peptide sequence Name Function

α - lactalbumin 50 – 53 Tyr - Gly - Leu - Phe α - lactorphin Opioid agonist, ACE

inhibition

β - lactoglobulin 102 – 105 Tyr - Leu - Leu - Phe β - lactorphin Non - opioid stimulatory

effect on ileum,

ACE inhibition

142 – 148 Ala - Leu - Pro - Met - His - Ile - Arg ACE inhibition

146 – 149 His - Ile - Arg - Leu β - lactotensin Ileum contraction

Bovine serum

albumin

399 – 404 Tyr - Gly - Phe - Gln - Asn - Ala Serorphin Opioid

208 – 216 Ala - Leu - Lys - Ala - Trp - Ser -

Val - Ala - Arg

Albutensin A Ileum contraction,

ACE inhibition

Lactoferrin 17 – 41 Lys - Cys - Arg - Arg - Trp - Glu -

Trp - Arg - Met - Lys - Lys - Leu -

Gly - Ala - Pro - Ser - Ile - Pro -

Ser - Ile - Thr - Cys - Val - Arg -

Arg - Ala - Phe

Lactoferricin Antimicrobial