Introduction- Definition, historical development in food microbiology and its significance

 




1.1) Introduction: The objective of the food microbiology is to develop ability to:

  • ·        Describe the nature of micro-organisms, their classification, identification, growth and cultivation.
  • ·         describe the importance of micro-organisms for food processing, fermentations, food spoilage and food poisoning;
  • ·         describe and evaluate both qualitatively and quantitatively the action of anti-microbial agents, chemical and physical;
  • ·         apply basic microbiological principles to the production, handling, processing and marketing of foods;
  • ·         perform basic laboratory techniques for studying micro-organisms;
  • ·         describe routine microbiological analyses for milk and other raw materials and for finished food products;
  • ·         select and evaluate analytical techniques for specific purposes and materials;
  • ·         identify appropriate techniques for use in quality control procedures;
  • ·         perform practical analyses of raw materials, food products, environmental samples and packaging materials; and
  • ·         understand the principles of test design.

 

The content includes microbiological diversity; fungi: yeasts and moulds; bacterial structure; bacterial growth and nutrient requirements; bacterial classification and identification; viruses: structure, replication and identification; methods for cultivation and identification of micro-organisms; control of micro-organisms; organisms of importance to dairy/food industry; microbiological quality of raw milk; rationale for microbiological testing; principles of test design; sample preparation; and microbiological testing of milk and dairy products and food.

 

 

1.2) Definition: Food microbiology is the study of the microorganisms which inhabit, create or contaminate food. Of major importance is the study of microorganisms causing food spoilage.

        However "good" bacteria such as probiotics are becoming increasingly important in food science. In addition, microorganisms are essential for the production of foods such as cheese, yoghurt, other fermented foods, bread, beer and wine.

 

1.3) Historical development in food microbiology:

It is not known exactly when our ancestors recognized the invisible creatures, now designated as microorganisms, in food.

        From the time of Greeks until the discovery of biogenesis, spoilage of food, especially of meat and fish, was thought to be due to spontaneous generation, such as the development of maggots. When the presence of different types of bacteria in many food was discovered, their appearance through spontaneous generation was explained to be the cause of food spoilage. Schawnn (1837) and Helmholtz (1843) associated the presence of microorganisms (bacteria) in food with both putrifactive and fermentative changes of foods. However, they did not believe in spontaneous generation, but they could not explain how microorganisms could bring about those changes. Finally, Pasteur resolved the mystery by explaining that contamination of food with microorganisms from the environment and their subsequent metabolic activities and growth were the causes of fermentation of grapes, souring of milk, and putrefaction of meat.

      Pasteur, in the 1860s, recognized yhe role of yeasts in alcohal fermentation. He also showed that souring of wine was due to growth of acetic acid-producing bacteria (Acetobacter aceti), and developed the pasteurization process to selectively eliminate these undesirable bacteria from wine. Like fermentation, cheese ripening was suggested by Martin in 1867 to be of microbial origin. John Lister, in 1873, was able to isolate milk-souring bacteria (Lactococcus lactis) by serial dilution procedure. Cienkowskii, in 1878, isolated the bacteria (Leuconostoc mesenteroides) associated with slime formation in sugar. In 1895, microbial enumeration of milk was developed by Von Geuns.

 

 

1.4) Significance: An individual who has completed courses in food technology (both lecture and laboratory) should gain knowledge in the following areas:

·         determination of microbial quality of foods and food ingredients using appropriate techniques;

·         determination of microbial type(s)involved in spoilage, health hazards and the identification of the sources;

·         design corrective procedures to control the spoilage and pathogenic microorganisms in food;

·         identify how new technologies in food processing can have specific microbiological problems and design methods to overcome the problem;

·         design effective sanitation procedure to control spoilage and pathogen problems in food processing facilities;

·         effective use of desirable micsoorganisms to produce fermented food;

·         design method to produce better starter cultures for use in fermented foods and probiotics;

·         food regulation(state, federal,international)

 

To be effective, in addition to the knowledge gained, one has to able to communicate with different groups of people about the subject (food microbiology and its relation to food science). An individual with good common sence is always in a better position to sense a problem and correct it quickly.

 

1.5) Importance of microorganisms in foods:

The importance of microorganisms in food has increased greatly. Their role in food can be either desirable or undesirable.

1.5. A) Undesirable role of microorganisms in foods:

i. Food borne diseases: Many pathogenic microorganisms (bacteria, molds and viruses) can contaminate food during various stages of their handling between production and consumption. Consumption of these foods can cause food borne diseases. Food borne diseases not only can be fatal, but they can cause large economic losses. Foods of animal origin are associated more with foodborne diseases than foods of plant origin.

 

Mass production of foods, introduction of new technologies in the processing and storage of foods, changes in food consumption pattern and the increase in imparts of food from other countries have increased the chances of large outbreaks as well as the introduction of new pathogens.

ii. Food spoilage: Except for sterile foods, all foods harbor microorganisms. Food spoilage stems from the growth of these microorganisms in food or is due to the action of microbial heat-stable enzymes. New marketing trends, the consumer desire for foods that are overly processed and preserved, extented shelf life and changed of temperature abuse between production and consumption of foods have greatly increased the chances of food spoilage and in some instances, with new type of microorganisms.  

 

1.5. B) Desirable role of microorganisms in foods:

i. Food bioprocessing: Many food grade microorganisms are used to produce different types of fermented foods using raw material from animal and plant sources. Consumption of these foods has increased greatly over the last 10 to 15 years and is expected to increase still more in future. There have been great changes in the production and availability of these microorganisms to meet the large demand.

ii. Food biopreservation: Antimicrobial metabolites of desirable microorganisms are being used in food in place of nonfood preservatives to control pathogenic and spoilage microorganisms in foods.

iii. Probiotics: Consumption of foods containing the live cells of bacteria that have apparent health benefits has generated interest among consumers. The efficiency of these bacteria to produce these benefits is being investigated.