P1: SFK/UKS BLBS102-c31 P2: SFK BLBS102-Simpson March 21, 2012 14:0 Trim: 276mm X 219mm 608 Printer Name: Yet to Come 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 Togwa (Tanzania) Various Bushera (Uganda) Sorghum, millet Ogi (Nigeria) Maize Pozol (Mexico) Maize Borde (Ethiopia) Various Idli (India) Rice and blackgram beans Species of LAB Lb brevis, Lb cellobiosus, Lb Plantarum W confusa P pentosaceus Lb brevis; E faecium Ln mesenteroides subsp mesenteroides Lb reuteri, Lb Leichmanii, Lb plantarum, Lb casei, Lb fermentum, Lb brevis, Lb alimentarius, Lb buchneri, Lb jensenii Streptococcus spp., Lb plantarum, Lb fermentum Lb brevis Ln mesenteroides Lc lactis, Lc raffinolactis Lb brevis W confusa P pentosaceus Leuconostocs spp Enterococcus faecalis Species of Yeast Reference P orientalis S cerevisiae C pelliculosa C tropicalis NR Mugula et al 2003 S cereviseae and Candida mycoderma Ogunbanwo et al 2003 Muyanja et al 2003 Odunfa 1985 Omar and Ampe 2000 C mycoderma, S cerevisiae, Rhodotorula spp Nuraida and others 1995 NR Abegaz 2002 Saccharomyces spp Soni and Sandu 1990 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 hydrolyze 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 offflavors Some products are characterized by a foaming consistency, 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, organic 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 produced during grain malting Secondary aldehydes and alcohols are responsible for these flavors and may also originate from microbial 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 refrigeration 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 by β-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 P1: SFK/UKS BLBS102-c31 P2: SFK BLBS102-Simpson March 21, 2012 14:0 Trim: 276mm X 219mm Printer Name: Yet to Come 609 31 Bakery and Cereal Products 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 genus Lactobacillus, but some products may contain Bifidobacterium spp or the yeast Saccharomyces boulardii While the potential benefits 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: r show a prophylactic action against and alleviate diarrhea caused by bacterial and viral infections, radiation therapy or the use of antibiotics; r suppress undesirable bacteria in the gut with beneficial results for patients with conditions such as irritable bowel syndrome and ulcerative colitis; r 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 pylori infections, 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, convincing proof for the efficacy of probiotics against these problems has not been obtained The positive effects that have been documented have led to a great interest from food manufacturers 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 fermented 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 prepared and marketed (Table 31.4) and may have an appeal for those who 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 cholesterol due to β-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 bacteria 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 106 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 probiă otic bacteria during storage (Martensson, Oste and Holst 2002) Many probiotic bacteria not tolerate a pH below 4.0, and fermented 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 fermentation 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 governed 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 require 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 hygiene both before and during fermentation A fast lactic acid Table 31.4 Fermented Probiotic Cereal Foods Type of Product (Commercial Name) Cereal Constituent Fermented fruit flavored cereal drink (Pro Viva) Fermented cereal drink Oat + malted barley flour Oat “milk” Fruit flavored cereal pudding (Yosa) Cereal-based weaning food Oat flour Maize + malted barley flour Note: LB = Lactobacillus; B = Bifidobacterium Probiotic Constituent Reference Lb plantarum 299v Molin 2001 LB reuteri; lb acidophilus; B bifidus Lb acidophilus; B bidus ă Martensson, Oste and Holst 2002 Lb acidophilus Lb rhamnosus ‘GG’ Lb reuteri Blandino et al 2003 Helland et al 2004 P1: SFK/UKS BLBS102-c31 P2: SFK BLBS102-Simpson March 21, 2012 610 14:0 Trim: 276mm X 219mm Printer Name: Yet to Come Part 5: Fruits, Vegetables, and Cereals development in the product during fermentation is a critical step, and the growth of probiotic organisms in cereal products is greatly stimulated by the addition of malted flour (either of the same grain or of barley malt) or milk, due to the increased availability of fermentable sugars, peptides, and amino acids For probiotic weaning foods, the use of malt has a further advantage since at a given viscosity, the product has a higher nutritional den-sity Probiotic cereal foods are in their infancy, and the future will probably see further development in this type of product New strains with proven probiotic efficacy and good flavor-forming abilities will increase the range of probiotic products available REFERENCES Abegaz K 2002 Traditional and Improved Fermentation of Borde, a Cereal-Based Ethiopian Beverage [PhD thesis] Ås, Norway Agric Univ of Norway ISBN: 82-575-0508-0 Abegaz K et al 2002 Indigenous processing methods and raw materials of borde, an Ethiopian traditional fermented beverage J Food Technol Africa 7: 59–64 Adams MR 1998 Fermented weaning foods In: BJB Wood (ed.) 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Lebensmittel-Untersuchung und-Forschung 1 78: 389 –392 Spicher G, Nierle W 1 988 Proteolytic activity of sourdough bacteria Appl Microbiol Biotechnol 28: 487 –492 Stanton WR 19 98 Food fermentation in the tropics... 1 38 Food and Agriculture Organization of the United Nations, Rome, Italy Fenema OR 1996 Food Chemistry Marcel Dekker, New York Fuller R 1 989 Probiotics in man and animals J Appl Bact 66: 365378