Bacteria in food can be the result of:
- a (more or less sophisticated) processing of the raw material by man
- an unpleasant and unwanted contamination, potentially harmful to the health of the consumer.
What are bacteria?
Bacteria are single-celled organisms prokaryotes totally different from other more complex forms of life, instead defined as eukaryotes;
NB. It is a common belief that bacteria, as a prokaryotic life form, are a LESS evolved category compared to eukaryotes; in reality, despite having observed that a part of them has probably been integrated into the cytoplasm of eukaryotic cells, giving rise to the mitochondrion ( cytoplasmic organelle responsible for aerobic energy production), most bacteria did NOT have any need to evolve into more complex structures, thanks to the typical adaptability that the strains demonstrate towards the entire terrestrial biosphere.
Classification of bacteria
The kingdom of prokaryotes, synonymous with bacteria (but also with blue algae), is differentiated into Eubacteria (common bacteria) ed Archaebacteria. Trying not to wander into detailed classifications of microbiological interest, we report some classification criteria useful in the field of food hygiene and possible contamination. Bacteria can be classified on the basis of:
- Form: bacilli, cocci, vibrioni, spirilli, spirochetes
- Optimal survival temperature: psychrophilic (active at very low temperatures), mesophilic (active at medium temperatures), thermophilic (active at high temperatures)
- Energy metabolism: aerobes (living in the presence of oxygen), anaerobes (living in the absence of oxygen), facultative aerobes-anaerobes (living both in the presence and absence of oxygen)
- Spore production: spore-forming (which produce spores) and asporigens (which do not produce spores)
- Acid resistance: acidophils (active with acid pH), neutrophils (active with neutral pH), basophils (active with basic pH)
- Relationship and interaction with the tissue: commensals or symbionts (normally present on the tissue.without causing disease they can be useful to the tissue itself), obligate pathogens (which originate pathology or infection) and facultative pathogens (which in some favorable situations MAY give rise to pathology or infection)
- Staining determined by the recognition in the laboratory: gram positive (gram +) and gram negative (gram- possessing HEAT RESISTANT endotoxins).
- Production of exogenous toxins: which produce exotoxins through metabolism and which DO NOT produce exotoxins through metabolism
- etc...
Based on the ability to interact with tissue, bacteria can be considered harmful, NOT harmful or even useful. We remind you that on our organism, more precisely on the skin, in the oral cavity, in the digestive tract, in the respiratory tract and to a lesser extent on the genital mucosa, there are more or less large and different types of bacterial colonies. Some colonies can be defined commensals or symbionts, such as the intestinal bacterial flora (subjectively determined) which with its fermentation allows the release of many vitamins of group B, favors the maintenance of the integrity of the intestinal mucosa and OPPOSES the proliferation of other microorganisms Rotating pathogens and / or parasites. Other colonies play an ambiguous role, such as staphylococcus aureus present on the whole skin, this optionally pathogenic bacterium does NOT perform useful activities to the organism BUT at the same time it does NOT represent a harmful agent. However, in case of reduced immune defenses and / or skin lesion it can give rise to mild infections (acne, pharyngitis, etc.) but also serious (bronchopneumonia, urinary infections, sepsis, etc.).
In food, however, most bacterial strains represent a potential contaminant; food infections, intoxications and toxic infections are pathogenic forms due to the ingestion of foods containing a bacteriological load and / or their exo or endotoxins, such as to cause a gastro-intestinal and more rarely systemic complication.
Ultimately, the presence of bacteria in food can easily translate into food contamination such as to give rise to a food "infection," poisoning or cough infection. However, there are also some types of harmless bacteria USEFUL in technical-food processing processes and others whose ingestion can provide a valid help to the organism.
PATHOGENIC BACTERIA
The bacteria most responsible for food contamination, and therefore food poisoning, infection and / or poisoning, are: Escherichia Coli, Staphylococcus Aureus, Salmonella (tiphi and Paratiphi), Enterococcus, Pseudomonas, Clostridium Perfringens, Clostridium Botulinum, Bacillus Cereus, Shigella, Yersinia, Listeria, Lactococcus.
Sources of contamination
Soil and water:often the bacteria present in the soil reach the food due to the action of the wind or air currents, not to mention that from the earth they are easily transferred to the cultivated products; at the same time, the bacteria present in the rainwater, in the wells or in the irrigation systems they can be carried in food during plantation irrigation, during washing before processing or when liquid is used as an ingredient.
Raw vegetables: for the reasons listed above, often the contact between ready-to-eat food (therefore already cooked) and raw products (especially fruit and vegetables) can facilitate the transfer of bacteria from raw to cooked, causing excessive proliferation on the latter; this is a process called "cross contamination".
Faecal-oral contamination: caused by the direct or indirect transfer of fecal residues on food; it can be facilitated by the fertilization of the soil and by the insufficiency of primary washing, by incorrect animal slaughter with rupture of the digestive tract during evisceration, by irrigation with black or contaminated water, by the transport caused by insects or other animals, by reduced hygiene of the staff, etc.
Contamination of the farmed animal: presence of bacterial infections in live animals
Presence of bacteria on the skin of animals:typical contamination of milk during milking
USEFUL bacteria in food
The useful bacteria in food are all those prokaryotes inoculated or otherwise normally present in food processing that:
- They favor the transformation of food (eg leavening of baked products, alcoholic fermentation, rennet)
- They favor the constitution or reconstitution of the intestinal bacterial flora (eg probiotics)
are above all: Lactobacillus Acidophilus, Lactobacillus Bulgaricus and Bifidobacteria.
We also remind you that, even though they are normally harmless bacteria, their POSSIBLE septicemic action induced by serious immune pathologies or secondary immunosuppression can in any case increase the risk of death.
