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

608 Part 5: Fruits, Vegetables, and Cereals

Table 31.3.Lactic Acid Bacteria and Yeasts Isolated from Some Traditional Fermented Cereal Products

Most Prevalent

Product (Country

of Origin) Cereal Basis Species of LAB Species of Yeast Reference

Togwa (Tanzania) Various Lb. brevis, Lb. cellobiosus, P. orientalis Mugula et al. 2003

Lb. Plantarum S. cerevisiae

W. confusa C. pelliculosa

P. pentosaceus C. tropicalis

Bushera (Uganda) Sorghum, millet Lb. brevis; E. faecium NR Muyanja et al. 2003

Ln. mesenteroides

subsp. mesenteroides

Ogi (Nigeria) Maize Lb. reuteri, Lb. Leichmanii, S. cereviseae and Ogunbanwo et al. 2003

Lb. plantarum, Lb. casei, Candida mycoderma

Lb. fermentum,

Lb. brevis, Lb. alimentarius, Odunfa 1985

Lb. buchneri, Lb. jensenii.

Pozol (Mexico) Maize Streptococcusspp., Omar and Ampe 2000

Lb. plantarum,

Lb. fermentum

Lb. brevis C. mycoderma, Nuraida and others 1995

Ln. mesenteroides S. cerevisiae,

Lc. lactis, Lc. Rhodotorulaspp.

raffinolactis

Borde (Ethiopia) Various Lb. brevis NR Abegaz 2002

W. confusa

P. pentosaceus

Idli (India) Rice and blackgram

beans

Leuconostocs spp. Saccharomycesspp. Soni and Sandu 1990

Enterococcus faecalis

Note: Lb., Lactobacillus; Ln., Leuconostoc; L., Lactococcus; P., Pediococcus, E., Enterococcus; W., Weisella; S., Saccharomyces; I., Isa;NR, Not

recorded.

malted flour in a product. The starter should also be able to hy-

drolyze the cereal protein in order to obtain the amino acids

sufficient for rapid growth, and it should produce desirable

and product-typical aroma and flavor compounds, but not off-

flavors. Some products are characterized by a foaming consis-

tency, and heterofermentative organisms (LAB or yeasts) are

required for this property. Bacteriocin-producing strains have

also been sought (Holzapfel 2002) in an attempt to increase the

microbiological safety of the products. Starter cultures must also

be commercially propagable and be able to survive preservation

methods without loss of viability, activity, or metabolic traits.

Microbiological and Biochemical Changes

in Traditional Fermented Cereals

Few studies have been made on the biochemical changes that

take place in traditional fermented cereals. Mugula et al. (2003)

analyzed samples of naturally fermented togwa made from

sorghum and maize, to which togwa was backslopped and malt

was added. The development of groups of microorganisms, or-

ganic acids, soluble carbohydrates, and volatile components was

studied during the 24-hour fermentation. Maltose and glucose

increased during the first part of the fermentation due to the

action of cereal amylases, but later were reduced as the growth

of LAB and yeasts increased. The pH dropped from around 5.0

to 3.2 in 24 hours, and this was mirrored by a rise in lactic acid

to about 0.5%. Ethanol and secondary alcohols and aldehydes

increased during the secondary part of the fermentation. Malty

flavors are typical for fermented cereal products and may be pro-

duced during grain malting. Secondary aldehydes and alcohols

are responsible for these flavors and may also originate from mi-

crobial metabolism of the branched-chain amino acids leucine,

isoleucine, and valine. These compounds are produced by yeasts,

some LAB, and probably also by other microorganisms in

the product.

Many spontaneously fermented cereals also have a very short

shelf life, since fermentation continues in the absence of refrig-

eration. Off-flavors, in particular vinegary notes, are a common

problem. The very low pH in fermented cereal products may be

sensorially compensated for by saccharification byβ-amylase.

FERMENTED PROBIOTIC

CEREAL FOODS

A probiotic food is a live bacterial food supplement, which when

ingested, may improve the well-being of the host in a variety of