History of Microbes in Food

All food items contain one or more types of microbes except for few sterile foods. (Canned foods) Some microbes have a specific role in food such as in the production of naturally fermented foods. Whereas other cause food spoilage and food born disease.

            To study the role of microbes in food and to control them, it is a important to isolate them in pure culture and study there morphological, physiological and bio-chemical and genetic characteristics.

Discovery of micro-organism:-

The discovery and research of micro-organism started with the invention and improvement of the microscope. In 1658 Athanasius Kircher reported that using a microscope he had seen minute living worms in putrid milk and meat. The magnification power of this microscope was so low that could not have seen bacteria.

In 1664, Robert Hooke, described the structure of mould. However, the first person to see different types of microbes specially bacteria was Antony Van Leeuwen Hook. He observed bacteria in saliva, rainwater and other materials. He classified the bacteria into three morphological groups.

1) Cocci (spherical shaped)

2) Bacilli (rod shaped)

3) Spirilla (spiral)

He also described that same bacteria are motile. (called as animalcules).

            Since good microscopes are not available at that time not much work was done about the bacteria, till the 19^th  century. However viruses where observed only after the invention of an electron microscope in the 1940.

            Ehrenberg introduce the term bacteria in 1838.

Where are these bacteria coming from?

            The theory of spontaneous generation i.e. generation of some form of life from non living objects, many powerful follower. Since the time of Greeks, the emergence of maggots from dead bodies and spoiled was thought to be spontaneous generation. However in 1861 Louis Pasteur demonstrated bacteria grow only if the product very contaminated with bacteria carrying by dust particle in air. This careful and controlled study help that bacteria will able to reproduces (biogenesis) and life could not originate by spontaneous generation.

 What are their functions?  

1.      Microbes are responsible for many diseases in human being, animal and plants.

2.      Many human diseases can be transmitted for person to person from small creature.

3.      Microbes are responsible for fermentation.

4.      Wine fermentation for grapes, spoilage of meat, milks other food items associated with growth of micro organism.

5.      Microbes play an important role in this recycling of nutrients.       

The internal tissue of healthy plants, (foods and vegetable) and animals (meat) are sterile but raw and processed food contains different type moulds, yeast, bacteria and viruses. Microbes can get in to foods from both natural and external sources to which food come in to contact during production until the time of consumption.

Natural sources for foods of plant origin include the surfaces of fruits, vegetable etc.

      Natural sources of fruits and animal origin include hair, skin, feathers, intestinal track, primogenital track, respiratory track. The type and level of these microbes vary greatly with types of plant and animal as well as their geographical location and environmental conditions. Decides natural microbes a food can be contaminated with different types of microbes coming from outside source such as air, soil, sewage, water, feeds, human food ingredient, packages , insects etc. equipments.

      Microbial types and their level from these sources getting in to source vary widely & depend on degree of sanitation used during holding of foods.

1.      Air

Microbes are present in dust and moisture droplet in the air. There level is control byte the degree of humidity, size and level of dust particles, temperature and air velocity generally dry air with low dust contain has a low microbial level spores of bacillus species, clostridium species, moulds, yeasts and cells of some of gram positive bacteria can be predominantly present in the air. Microbe’s contamination of food from air can be reduced by controlling dust particles in the air reduce in the humidity level and installing UV light.

2.      Soil

Soil contain of several verity of microbes because microbes can multiply with soil, there number can be billions per gram many types of moulds, yeasts and bacterial genre (Entarobacter, pseudomonas, proetus, micrococcus, Entrococcus, Bacillus, Clostridium) can inter in to foods from the soil. Soil contaminated with fecal material can be the sources of enteric pathogenic bacteria (intestine) and viruses in food. Sediment where marine foods and fish are harvested can also d a sources of microbes including pathogen in those foods. Different type parasites can also get in to food from soil. Removal of soil and sediments by washing and avoiding soil contamination can reduce microbes in foods from these sources.

3.      Sewage

Sewage can contaminate foods with microbes and most significant of with are different anthropogenic bacteria and viruses

4.      Water

Water is use to produce processed and under certain condition to store the food. It is used for irrigation of crop, drinking by animals and birds raising marine and fishery products, washing, processing (pasteurization, canning and cooling of heated food) and storage of foods (i.e.)washing and sanitation of equipment and processing etc. water is also used as an ingredient in many processed foods. Thus water quality greatly influenced microbial quality of food. Contamination of food with pathogenic bacteria, viruses, parasites has been recorded. Chlorine heated potable water should be used in processing sanitation and as an ingredient.  Although potable water does not contain coli form and other enteric pathogen it can contain some bacteria capable of causing food spoilage such as pseudomonas, Alkaligens and flavobactrium. Improperly treated water can contain pathogenic and spoilage microorganism.

5.      Humans

Foods coming in contact with different people handling the food, they include not only people working in the farm and food processing plant but also those handling food at restaurants, catering services, retail stores and at home.  Human carrier has been the source of pathogenic microbes in food that later cause food bound disease especially ready to it foods.

In properly clean hand lack of personal hygiene and dirty cloths can be major sources of microbial contamination in food. The presence of minor cuts and infection in hands and face and mild generalize diseases can possibly cause contamination in foods.  In addition to spoilage bacteria pathogen such as Staphylococcus aureus, Salmonella, Shigella, E.coli can be introduced into the food from human sources.  Proper training of the people in personal hygiene regular checking of health and maintaining efficient sanitary standard are necessary to reduce contamination from these source.

6.      Food ingredients

Many ingredients or additives are included in the preparation of different types of food products.  Many of these ingredient source of both spoilage and pathogenic microbes. Various spices generally have very high population of bacterial spores starch, sugar flour might have spore of thermophillic bacteria.  Pathogen has been isolated from dried coconut, chocolate.  The ingredient should be prepared under sanitary condition and should be given antimicrobial treatments.

7.      Equipments

Wide variety of equipments used in harvesting, transportation, processing and storing foods.  Many types of microbes, from air raw food, water and human beings can get into the equipment and contaminate foods. Microbes can multiply and contaminated large volume of foods when processing equipment is used continuously for long period of time microbes initially present can multiply and act as a continues source of cross contamination.

Microbes associated with fish.

Pseudomonas, Vibrio .native

Protein -            18 to 23%                                                      Tuna Maximum 23%

Fat          -          1- 25%

Minerals -         3%

Moisture-        60-90%

NPN – Non Protein Nitrogenous compounds

            TMAO, Urea, Free amino acid.