Lactoperoxidase system?

Components of the Lactoperoxidase System

Lactoperoxidase

The thiocyanate ion

Hydrogen peroxide

Lactoperoxidase activity and thiocyanate concentration in different types of milk

Tape of milk Lactoperoxidase (Units/ml) Thiocyanate (ppm)

Cow 1.4 3.2-4.6

Ewe 0.14-2.38 10.3-20.6

Goat 1.55 4.03

4.45 10.29

SAIB 0.26 4.58

Saanen 0.79 2.78

Buffalo 0.9 5.4

Guinea pig 22

Human 0.06-0.97 2.6

Limit for bacterial activity 0.02 15

The structural damage of microbial cytoplasmic membranes by the oxidation of SH-groups results in leakage of potassium ions, amino acids and polypeptides into the medium. Subsequently uptake of glucose, amino acids, purines, pyrimidines in the cell and the synthesis of proteins,DNA and RNA is also inhibited.

Antimicrobial spectrum of the LP system

Bacteriostatic and/or bactericidal activity on

Depend on

bacteria

fungi

viruses

type of electron donor

test media

temperature

pH

Cell count

Effect of LP system on the activity of lactic starter cultures

Starter cultures Effect

Lactic acid bacteria Reduced rate of acid production

Thermophilic starters Delay in coagulation time by 4.5 h

when inuoculated 2h after activation

Yoghurt starter Reduced rate of acid production and

delay in curdling time by 1 ½ h

LF-40 Reduced rate of acid production

Lactobacilus acidophilus Reduced rate of acid production

Mesophilic cheese starter culture Inhibition of growth and acid production

LL 50C Insensitive to LP system

Sensitive generating H2O2, L.acidophilus, 3 strains of L.delbrueckii subs.bulgaricus(1373,1489,LBR)

Sensitive but do not have the ability to generate H2O2 and require an extraneous source, L.helveticus, S.thermophilus

Resistant, Enterococcus faecium, lactobacillus lactis,1 strain of L.delbrueckii subs.bulgaricus(1243)

Suseptibility of Thermophilic Starters

to the LP system

Suseptibility of Thermophilic Starters

to the LP system

Type of milk used Type and strain of starter cultures used Level of thiocyanate and H2O2 used Natural levels of thiocyanate and H2O2 in milk Temperature of heating LP-activated milk and antibacterial compounds formed Time and temperature of incubation Rate of inoculation of starters

LP treated milk for the manufacture of

fermented milk products

Effect of the LP system on the manufacture of fermented milk products

Cottage cheese: Taste and flavour of experimental cheese slightly different from the control,increased cheese yield

Acidophilus milk: Lower diacetyl and acetoin content and lower proteolytic activity

Gouda cheese (Goat): Improves microbiological quality and flavour

Manchego cheese (Ewe): Prevents excessive proteolysis and softening

Yoghurt (Cow): No difference in chemical composition and organoleptic qualities

Yoghurt (Buffalo):A delay in curdling time by 1 h 20 min, no effect on body and texture, lower flavour rating

Preservation of raw milk LP-low temperature thermal processes Functional foods Preservation of cosmetics As a preservative in foods and pharmaceutical

Application of the LP System

Fish farming Infant milk formula Thoothpaste & Mouth rinses Bacterial clearance from airways

As a protectant in ophthalmic fluids

In milk replacers for calves

As a possible index for mastitis

Degradation of various carcinogens

Synergy with other preservatives

CONCLUTIONCONCLUTION

The LP system can be utilized not only for milk preservation but olso for multiple application across the food industry both in developed and developing countries.

R.Fathi