PART III PROCESS SAFETY
6. Inventory of Microorganism with a Documented History of use in Food
6.3. Some fermentation products of high value added from bacteria
Polysaccharides are used commercially to produce gels and thicken and stabilize foods, medicines and industrial products. At list 20 different microbial polysac- charides with market potential have been described, but the largest part of the market is held by xanthan.
The microbial production of polysaccharides from microbial sources offers controllable polymer synthesis from materials in constant supply, yielding prod- ucts that possess unique physical and chemical properties, improved functional characteristics and low biological oxygen demand.
According to Lee (1996d), the microbial polysaccharides consist of three main types:
– Intracellular polysaccharides, which may provide mechanisms for storing car- bon or energy for cell,
– Structural polysaccharides, which are components of cell structures, e.g.
lipopolysaccharides and
– Extracellular or exopolysaccharides.
Table 6 presents the most important polysaccharides use by the food industries.
From all this data we can see that the selection of specific starter cultures for substrates such as meat, vegetables, cereals, indigenous crops or combinations of dairy products with cereals substrates and not only, provide good possibilities for the future development of healthy foods with high nutritional and sensorial prop- erties for people in many parts of the world. In the same time for the production of added value products, it seems evident that the microorganisms have become a very important economical asset.
7. References
Ananta, E., Volkert, M., and Knorr, D., 2005, Cellular injuries and storage stability of spray-dried Lactobacillus rhamnosus GG. International Dairy Journal (in press).
Baati, L., Fabre-Gea., Auriol, D., and Blanc, P.J., 2000, The cryotolerance of Lactobacillus acidophilus: effect freezing conditions on the viability and cellular Levels. International Journal of Food Microbiology 59:241-247.
TABLE 6. Microbial polysaccharides use by the Food Industry (Lee, 1996d). (Crueger et al., 1989a)
Polysaccharides Microorganisms Composition
Xanthan mannose Xanthomonas D-Glucose, D-mannose
Campestris D-glucuronate
Alginate Pseudomonas aeruginosa D-Mannuronic acid
L-Gucuronate Azotobacter
Vinelandii
Dextran Lactobacillus sp. D-Glucose
Leuconostoc mesenteroides Leuconostoc dextranicum Streptococcus mutans
Curdlan Alcaligenes D-Glucose
Agrobacterium
Pullulan Aurobasidium pullulans D-Glucose
Beresford, T.P., Fitzsimons, N.A., Brennan, N.L., and Cogan, T., 2001, Recent advances in cheese microbiology. International Dairy Journal 11:259-274.
Bosschaert, M.A.R. and Pot, B., 2001, Yakult Europe BV, Almer, the Nederlands Buckenhuskes H., 1993, Selection criteria for lactic acid bacteria to be used as starter cul-
tures for various food commodities. FEMS, Microbiology Reviews 12:253-272.
Carvalho, A.S., Silva, Joana, Ho, P., Teixeira, P., Malcata, F.X., and Gibbs, P., 2004, Relevant factors for the preparation of freeze-dried lactic acid bacteria. International Dairy Journal 14:835-847.
Crueger, W. and Crueger A., 1989, Organic feedstocks produced by fermentation.)in:
Biotechnology. Book. Thomas D. Brock ed, Sinuaer Associates Inc. Sunderland. USA. p. 331.
Crueger W. and Crueger A., 1989a, Organic feedstocks produced by fermentation.)in:
Biotechnology. Book. Thomas D. Brock ed, Sinuaer Associates Inc. Sunderland. USA.
pp. 124-129.
Dass, C.R., 1999, Starter cultures: importance of selected genera in: Encyclopaedia of Food Microbiology, Academic Press.
Davis, J.G., 1952, Food 21:249(July) 284 (August).
Demain, A.L., 2000, Small bugs, big business: the economic power of the microbe.
Biotechnology Advances 18:499-514.
Derieux, J., 1988, Histoire de la panification et de levure dans Levure et panification ..
Fould ed., Springer. Tecno-Nathant. pp.14-15
Gardner, N.J., Savard, T., Obermeier, T., Caldwell, G., and Champagne, C.P., 2001, Selection and characterization of mixed starter cultures for lactic acid fermentation of carrot, cabbage, beet and onion vegetable mixtures. International Journal of Food Microbiology 64:261-275.
Hansen, E.B., 2002, Commercial bacterial starter cultures for fermented foods of the future. International Journal of Food Microbiology 78:119-131.
Hough, J.S., Briggs, D.E., Stevens, R., and Young, T.W., 1982, Malting and Brewing Science 2nd.ed., Chapman & Hall, London.
Huis in’t Veld, J., Hose, H., Schaafsma, G., Silia. H., and Smith, J., 1989, Unpublished per- sonal data.
Lee, B., 1996a, Bacteria – Based processes and Products. p. 221. Fundamentals of Food Biotechnology. Book ed. VCH, USA.
Lee, B., 1996b, Bacteria – Based processes and Products.. Fundamentals of Food Biotechnology. VCH, USA p. 233.
Lee, B., 1996c, Bacteria – Based processes and Products.. Fundamentals of Food Biotechnology VCH, USA. pp. 183-184.
Lee, B., 1996d, Bacteria – Based processes and Products.. Fundamentals of Food Biotechnology VCH, USA. pp. 276-77.
Linko, Y-T., Javanainem, P., and Linko, S., 1997, Biotechnology of bread baking. Trends in Food Science 8:339-344.
Mogensen, G., Salminen, S., O’Brien, J., Ouwehand A., Holzapfel, W., Shortt, C., Fonden, R., Miller G.D., Olsson, L., and Hahn-Hagerdal, B., 1996, Fermentation of lignocellulic hydrolysates for ethanol production. Enzyme and Microbial Technology.18:312-331.
Pot, B., Ludwig, W., Kersters, K., and Schleifer, K.-H. 1994., Taxonomy of lactic acid bac- teria,. In: Bacteriocins of Lactic Acid Bacteria: microbiology, genetics and applications, L. De Vuyst and E.J. Vandamme ,eds., Chapman and Hall, London pp. 13-90.
Romano, P.v Fiore, P., Paraggio, M., Caruso, M., and Capece, A., 2003, Function of yeast species and strains in wine flavour. International Journal of Food Microbiology, 86:169-180.
Samelis, J., Metaxopoulos, John., Vlassi, M., and Pappa, M., 1998, Stability and Safety of traditional Greek salami — a microbiological. International Journal of Food Microbiology 44:69-82.
Wainwright, M., 1992, An Introduction in Fungal Biotechnology. John Wiley and Sons, Chichester,U.K.
Walker, G., 1998, Development in Yeast Technologies in: Yeast Physiology and Biotechnology. J.Wiley and Sons, England. pp. 283-309.
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9
Pathogenic, Commensal and Beneficial Microorganisms in Foods
ANAM.P. GOMES1, MANUELAE. PINTADO1, ANDF. XAVIERMALCATA1
177
1. Introduction
Moulds, yeasts, bacteria, viruses and minute parasites are microorganisms that virtually occur everywhere within the environment. Viruses are the smallest known living organisms (see Figure 1). They do not have a cell wall, a membrane or a nucleus and are defined as obligate intracellular parasites. When they repro- duce, they take over the life processes of host cells, which continue to live while producing viral copies. Most cells in food products are dead following process- ing and therefore simply function as carriers of viral material. Some viruses can be spread by people who handle food and do not follow careful personal hygiene habits. A person may indeed excrete viruses in faeces, urine or even through sneezing; so, if hands are not washed well after using toilet facilities as well as sneezing; any food handled after the event will be contaminated. Foods that are not usually processed thermally after handling – such as bakery products, uncooked oysters or clams, sandwiches, salads and desserts, may therefore carry and hence transmit viral illnesses. Bacteria are single-celled organisms, which multiply and increase in number through cell division given appropriate environ- mental conditions. Many pathogenic bacteria are facultative anaerobes, so they can grow in either aerobic or anaerobic conditions.
Yeasts are also single-celled organisms, which can convert nutrients into alco- hol and carbon dioxide via fermentation. Wild yeast spores are permanently float- ing in the atmosphere and may land on uncovered liquids and foods – hence resulting in contamination. In general, yeast contamination in food generates slime on the surface, bubbles in the bulk and an alcoholic smell or taste. Yeasts can be destroyed by heating to 121˚C for 15 min; nevertheless, in industrial food processing, carefully cultured yeasts are used in the production of beer, wine and bread.
1Escola Superior de Biotecnologia, Universidade Católica Portuguesa P-4200-072 Porto, Portugal
Moulds are multi-cellular forms of fungi, which can grow on almost any item used as or for food, given suitable conditions. Mould spore casings are present in the environment; when they break, thousands of microscopic mould spores are released, each one capable of germinating and originating a new mould.
This is a process that typically occurs in damp, dark environments. As spores on the surface of food ripen, the food develops unpleasant musty odours, which destroy the (normally sought) fresh flavours. Certain moulds may produce poi- sonous toxins – called mycotoxins. Aflatoxin is one such mycotoxin that is secreted on nuts, corn, wheat and other grains. Aflatoxins may also be found in products made from dry fruits and cereals, such as breads and peanut butter.
Ingestion of aflatoxin usually causes low grade fever in humans but can also produce cancer in trout, rats and ducks. Other illnesses thought to worsen via the presence of aflatoxins include Reyes syndrome, cirrhosis and kwashiorkor (Jones, 1992; Jay, 1986).
Parasites are organisms that live or feed off other organisms. In general, they are found in raw animal products or seafood. Parasites, which include Trichinella spiralis (a round worm found in wild game or pork) and Anisakis spiralis (com- monly referred to as “cod fish worm” or “seal worm” and found in fish), are destroyed by thorough cooking.
Most foods harbour a mixture of the aforementioned microorganisms, which play a role in several biological interrelationships ranging from (competitive) amensalism to antagonism and encompass specifically mutualism, commensal- ism and parasitism (or predation).
Mutualism may be understood as a mutual dependency between two microor- ganisms, in which each microorganism attains some benefit – trivial or vital, from the other. In a commensalism pattern, only one microorganism is able to obtain a benefit from the association, whereas the other is unaffected by it. Finally, in parasitism, pathogenic microorganisms (considered to be disease-causing agents) obtain support from the host at its expense. As previously mentioned, these harm- ful microorganisms can invade any food and may survive despite aggressive measures at the processing level and storage – or the food may become contami- nated during preparation, cooking or serving. When present in the food at or
Eucariotic
10 nm 1mm 10 mm 100 mm
Small virus Large virus Bacteria Archaebacteria Algae
Protozoa Fungi
Procariotic
FIGURE1. Relative size and cell-type of organisms involved in micro-ecology of food.
above their infective dose threshold, they will cause illness – sometimes severe and even life-threatening, especially in young children, older adults and persons with compromised immune systems. In pregnant women, foodborne illness may also endanger their unborn babies. The Centers for Disease Control and Prevention (CDC) in the USA, estimate that 76 million people suffer foodborne illnesses each year in that country, hence accounting for 325,000 hospitalizations and more than 5,000 deaths.
There are more than 250 known foodborne diseases. Bacteria cause most cases, followed by viruses and parasites. Some diseases are caused by toxins (poisons) from disease-causing organisms, others by host reactions to the organism itself.
The most common symptoms of foodborne illness are diarrhoea, abdominal cramps, vomiting, head- or muscle-aches and fever. Symptoms usually appear 12 to 72 hr after eating contaminated food but may occur as early as 30 min or as late as 4 weeks afterwards.