Bacteria

BACTERIA.  They are single-celled living beings of microscopic size that are present in soil, air, water, living beings, domestic animals and in people. Bacteria are classified into three groups:

• BENEFITIAL BACTERIA: Their presence in food does not cause any harmful effects, even sometimes it is necessary that they are present during the preparation as in the case of cheeses, kumis and yogurts.
• ALTERING BACTERIA: They are those that, at normally high levels, will cause changes in color, smell, taste and texture in food. They are the cause of most of the alterations and rots.
• PATHOGENIC BACTERIA They are those that are present in food, they will cause food poisonings and/or infections. Their presence in food will not cause them to change smell, taste and color so it will not make it possible to detect the potential danger due to their external appearance. Some of the pathogenic bacteria are: Escherichia Coli, Salmonella, Staphylococcus, Listeria monocytogenes, Clostridium, Bacillus Cereus among others. 

Bacteria, to cause their harmful effects, have to grow and multiply on food. If they find the conditions favorable, they begin to reproduce by dividing into two equal parts; a split occurs every 10 to 20 minutes approximately. It is proven that between seven to eight hours a single bacterium can give rise to millions of bacteria. Some bacteria can give rise to forms of resistance that are called spores, remaining in a dormant state. These can survive cooking temperatures below 100°C and if subsequently the food is kept at room temperature it can lead to normal forms that then multiply.

FACTORS THAT INFLUENCE BACTERIAL GROWTH:

1. Nutrients: Most of the raw material is converted into nutrients, especially those foods with high protein content, such as poultry, fish and beef.

2. Moisture: The amount of water available in food is called aqueous activity and can be reduced to safe levels by freezing, dehydration, adding sugar or salt or by cooking. Food is potentially dangerous when water is added to it.

3. Origin: Bacteria have a wide and variable response to free oxygen. They can be divided into: 

• Aerobic bacteria: which develop in the presence of free oxygen. 
• Anaerobic bacteria: which develop in the absence of free oxygen. 
• Facultative aerobics, bacteria that can grow both in the presence and absence of oxygen.

4. Acidity: Most bacteria the optimal pH of growth is between 6.5 and 7.5, although some bacteria can develop at extreme pH, in most species the minimum and maximum limits correspond to any point between pH 4 and 9. Potentially dangerous foods have a pH level of 4.6 to 7.0. However, foods high in acids such as citrus fruits rarely allow bacterial growth.

5. Time: When a bacterium is in suitable conditions, it begins to reproduce, in which a cell divides into two equal parts; method that is called «binary fission». Under conditions of environment and temperature a division occurs every 20 or 30 minutes, under favorable conditions a continuous proliferation, a single cell can be transformed into more than 17 million in a period of 8 hours and in a billion after 10 hours. The time it takes to prepare menus, or the time it takes to wait to be served, is an important factor for bacterial growth. Potentially dangerous foods should be exposed for the shortest possible time in the danger zone. (10° to 65°C). 

6. Temperature: It is probably the most important environmental factor that affects the growth and viability of bacteria. The temperature range in which most pathogenic bacteria multiply is between 5 ° and 65 ° C, with the optimal temperature of growth and multiplication being between 30 and 40 ° C. At temperatures above 65°C the bacteria die, with maximum destruction when the cooking temperature is higher. At refrigeration temperatures some bacteria begin their growth and, at freezing temperatures, they inactivate and remain in a state of dormancy; it is important to note that freezing destroys some bacteria, although most pathogens survive. During thawing they can multiply again.

*Source Rincón del Vago

BIBLIOGRAPHY
MINISTRY OF HEALTH. Implementación y Funcionamiento. Sistema de Análisis de Riesgos y Puntos Críticos de Control HACCP. Industria de Alimentos. Santa fe de Bogotá.1997. 

MINISTRY OF HEALTH. Implementación y Funcionamiento. Sistema de Análisis de Riesgos y Puntos Críticos de Control HACCP. Industria Pesquera y Acuícola. Santa fe de Bogotá.1997. 

PANAMERICAN HEALTH ORGANIZATION. Manejo Higiénico de Alimentos Catering Aéreo. Bogotá, 1994. PASCULLI HENAO LAURA, ANDREA VARÓN GARCÍA. Plan Genérico para la Implementación del Sistema HACPP en la Industria Avícola. Bogotá 2000. PELCZAR/ REID/ CHAN. Microbiología, Editorial McGRANW –HIL. México.1892 ROMERO JAIRO. Documentación del Sistema de Aseguramiento la Inocuidad de una empresa de Alimentos. Asecalidad. Bogotá. 199