Food Biochemistry and Food Processing (2 edition)

BLBS102-c35 BLBS102-Simpson March 21, 2012 14:9 Trim: 276mm X 219mm Printer Name: Yet to Come

682 Part 6: Health/Functional Foods

Table 35.4.Some Enzymatic Activities Which May be Linked to the Functionality of Probiotic Bacteria

Enzyme Function Functionality Species

β-Galactosidase Lactose hydrolysis in food

matrix

Improved growth in milk Wide-ranging

Lactose hydrolysis in the GI

tract

Improved lactose hydrolysis in

GI tract for population

suffering of lactose

maldigestion

Yogurt startersStreptococcus

thermophilus L. delbrueckii ssp.

bulgaricus

NADH oxidase and

NADH peroxidase

Eliminate H 2 O 2 Improved stability in presence

on oxygen

Lactobacilli and

bifidobacteria—strain variable

ATPases Excretion of protons (H+)

from cells to outer

medium

Reduced intracellular drop in

pH and increased survival to

gastric transit

Many LAB (Streptococcus,

Lactococcus and Lactobacillus

spp)

Arginine deiminase

pathway

Production of NH 3 and ATP Reduced intracellular drop in

pH and increased survival to

gastric transit

Lactobacilli

Bile salt hydrolase Deconjugation of bile salts Lowers blood cholesterol level Bifidobacteriumssp. often show

high activity, but many

Lactobacillusssp. cultures are

also active

α-Galactosidase Hydrolysis of stachyose and

raffinose in GI tract

Reduces gas discomforts linked

to consumption of beans

L. plantarum, B. longum

Proteases Hydrolysis of caseins, or soy

proteins

Produces ACE inhibitory

peptides, which are

antihypertensive

L. helveticus

Glutamate

decarboxylase

Conversion of glutamate to

GABA

Lowering of blood pressure Lactococcus lactis, L. paracasei

Glucosidases Deconjugates isoflavones or

quercetin from

glycosylated forms

Higher levels of the more

bioactive forms of

antioxidants (cancer, bone

metabolism, etc.)

L. helveticus, L. acidophilus, B.

longum, L. plantarum

GI, gastro-intestinal; ACE, acetyl choline esterase;L., Lactobacillus; B., Bifidobacterium;LAB,lactic acid bacteria; GABA, gamma-amino

butyric acid.

value of other foods as well. For example, isoflavones are en-

countered in soy products. The native forms of the isoflavone

in soy are mainly daidzein, genistin, and glycitein that are the

glycosylated forms. Theseβ-glucosides, are not readily bioavail-

able in humans as they are unable to be absorbed through

the intestinal tract. Hydrolysis ofβ-glucosides by bacterialβ-

glucosidases, produces the active and more readily metabolized

aglycone forms (Setchell et al. 2002). Many lactobacilli and bi-

fidobacteria possess glucosidases. Thus, the data show that soy

fermentation with selected strains contributes to increasing the

levels of bioactive aglycons (Champagne et al. 2010).

In summary, many enzymatic activities of lactic cultures con-

tribute to the synthesis, or simply to the release, of probioactives

in foods (Table 35.4).

CONCLUSION

Many biochemical processes are critical in the functionality of

probiotic bacteria. From a technological perspective, it can be

foreseen that cells will be adapted to enhance a specific en-

zymatic activity that will promote their growth or their stabil-

ity during storage. Minor acid, osmotic, and thermal stresses

have been proposed for this purpose (De Angelis and Gobbetti

2004).

As knowledge of the enzymatic systems involved in health

functionality of probiotics increases, the requirement for viable

cells might gradually be reduced. Thus, the critical element for

the health effect may be limited to the enzymatic components,

for example, the quantity of the probioactive. The use of pure

enzymes might eventually be considered in substitution to pro-

biotics, but only if the enzymes are stable in the matrix and if

they survive passage to the GI conditions. Even if it is enzyme-

linked, functionality might still require that the enzymes be de-

livered through a cell, viable or not, in order to protect them

against inactivation in the adverse conditions, they will be ex-

posed to in the food or the GI tract. Therefore, more research

is needed not only on the biochemical processes involved in the

functionality of probiotic bacteria, but also on factors that will

enable the “delivery” of the biochemical activity at the proper

site.