Food Biochemistry and Food Processing (2 edition)

BLBS102-c31 BLBS102-Simpson March 21, 2012 14:0 Trim: 276mm X 219mm Printer Name: Yet to Come

31 Bakery and Cereal Products 609

ways by influencing the balance of the host’s intestinal flora

(Fuller 1989). Most probiotic bacteria have been isolated from

the healthy human intestine and are members of the genusLac-

tobacillus, but some products may containBifidobacteriumspp.

or the yeastSaccharomyces boulardii. While the potential bene-

fits of probiotic bacteria have been generally accepted for many

decades, it is only in comparatively recent years that research

has been able to scientifically document the beneficial medical

effect due to some specific strains (Gorbach 2002). There is

now strong scientific evidence that specific strains of probiotic

microorganisms are able to:

 show a prophylactic action against and alleviate diarrhea

caused by bacterial and viral infections, radiation therapy or

the use of antibiotics;


 suppress undesirable bacteria in the gut with beneficial

results for patients with conditions such as irritable bowel

syndrome and ulcerative colitis;


 influence the immune system, showing positive results for

infant atopic eczema and other allergies.

Indeed, in addition to the list above, other effects have been

proposed: the lowering of blood cholesterol; the prevention of

acute respiratory infections,Helicobacter pyloriinfections, and

colonization by potential pathogens in intensive care units in

hospitals; relief of constipation; and a protection against the

development of various forms of cancer. However, so far, con-

vincing proof for the efficacy of probiotics against these prob-

lems has not been obtained. The positive effects that have been

documented have led to a great interest from food manufactur-

ers and consumers alike. The main motivation for consuming

probiotic products is said to be the developing consumer trend

towards healthy living though natural foods and medicines and

a trend away from the use of antibiotics and the incorporation of

chemical additives in food. As the beneficial effects of probiotic

foods become scientifically accepted, there will be increasing

pressure from food manufacturers on the authorities to allow

health claims to be used in product advertising. Probiotic fer-

mented milks were the first probiotic products to be produced

commercially and are available in many countries (Tamime and

Marshall 1997).

Some fermented probiotic cereal products are now being pre-

pared and marketed (Table 31.4) and may have an appeal for

those who do not consume dairy products.

Oats are a popular basis for probiotic cereal foods. This choice

is due to the healthy image of oats with respect to soluble and

insoluble fiber content and the potential to reduce blood choles-

terol due toβ-glucans. A prebiotic is a compound, usually an

oligosaccharide, that reaches the colon undigested by the host’s

enzymes and selectively favors the growth of probiotic bacte-

ria. Such compounds include lactulose, fructooligosaccharides,

and inulin. It has been suggested that the best probiotic results

may be obtained by using a combination of a prebiotic (such as

oats) and a probiotic organism (Charalampopoulos et al. 2002).

In this way, the total physiological effect of the food could be

increased.

In order for a probiotic product to have a physiological effect,

it has been suggested that it should contain at least 10^6 cfu/g

product, and that daily intake should be at least 100 g (Sanders

and Huis in’t Veld 1999). The final acidity in the product has

been shown to be of critical importance for the survival of probi-

otic bacteria during storage (Martensson, ̊ Oste and Holst 2002). ̈

Many probiotic bacteria do not tolerate a pH below 4.0, and fer-

mented cereals frequently reach this pH due to the poor buffering

capacity of the substrate. In addition, the physiological state of

the probiotic organisms at the time of storage also determines

their survival. Organisms that show poor growth during a fer-

mentation period are more likely to die out during cold storage.

This necessitates careful formulation of the product as well as

selection of the right probiotic culture.

The choice of a substrate for a probiotic food is partially gov-

erned by the tolerance of the food towards heat pasteurization

or even sterilization before fermentation, and cereal mixtures

lend themselves well to this treatment. Probiotic products re-

quire fermentation at around 37◦C for 8–18 hours, depending

on substrate. The suitability of such conditions for the growth

of pathogenic organisms necessitates strict adherence to hy-

giene both before and during fermentation. A fast lactic acid

Table 31.4.Fermented Probiotic Cereal Foods

Type of Product

(Commercial Name) Cereal Constituent Probiotic Constituent Reference

Fermented fruit flavored

cereal drink (Pro Viva)

Oat+malted barley

flour

Lb. plantarum299v Molin 2001

Fermented cereal drink Oat “milk” LB. reuteri; lb.

acidophilus;

Martensson, ̊ Oste ̈

and Holst 2002

B. bifidus

Fruit flavored cereal

pudding (Yosa)

Oat flour Lb. acidophilus; B. bifidus Blandino et al. 2003

Cereal-based weaning

food

Maize+malted

barley flour

Lb. acidophilus Helland et al. 2004

Lb. rhamnosus ‘GG’

Lb. reuteri

Note: LB=Lactobacillus; B=Bifidobacterium.