Post on 02-Jan-2016
5| 25 Microorganisms and food
• What are they?• Main characteristics of living
beings?• Functions and applications?
Microorganisms
4| 25 Microorganisms and food
• What do you understand by microbial growth?
• What factors affect microbial growth?
• How can we control the growth?
Microbial Growth
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Microbial growing stages in a liquid environment. A – Lag stage; B- log stage; C- stationary stage and D- death stage
Log10células/mL
Tempo
crescimento em condiçõesóptimas
crescimento em outrascondições
Microbial Growth
Time
Growth in other situations
Growth in optimum conditions
• Intrinsic factors- Nutrients
- pH- Water activity- Available oxygen
• Extrinsic factors- Temperature
- Relative humidity - Atmospheric oxygen
• Other factors:- Biological structures
- Natural antimicrobial substances
Microbial growth factors
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TemperatureTemperature is one of the most relevant factors for microbial growth .
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Microbial growth factors - Temperature
Main cause that lead to Intoxications :
• Utilization of risk temperatures while conserving food/meals;
• Utilization of inadequate temperatures while preparing/processing those foods (under processing);
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Microbial growth factors - Temperature
Adapted from: Adams, M.R. and Moss, M.O., 1995
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Microbial growth factors – Hurdle effect
• Main groups with importance for FS:– Bacteria
• Main characteristics
– Fungi (Molds and yeasts)• Main characteristics
Microorganisms
10| 25 Microorganisms and food
• Unicellular;• Various forms (cocci, bacilli, spirilla);• Some develop resistant structures
(spores);• Main cause of food intoxications of
biological origin.
Bacteria
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Fungi(molds and yeasts)
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• Unicellular (yeasts);• Multicellular (molds or filamentous
fungi);• Great decomposers of organic matter;• Widely used for making food and
beverages;• Some are eatable (mushrooms);• Responsible for deteriorating most
fruits and vegetables.
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Molds and yeasts
Some utilizations of fungi: a) Some eatable mushrooms. b) beer ; c) bread; d) Roquefort cheese with blue mold; e) e f) Camembert an brie cheeses (respectively) with white mold.
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• What are the sources of microorganisms that are present on foods?
– Soil;– Water; – Air;– Handlers;– Utensils and equipments;– Products themselves or raw
materials used in their fabrication.
Main sources
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• Soil- Source of spore forming bacteria, fungi
and yeasts;- Addition of manure – faecal
microorganisms;- Dissemination of microorganisms:
wind, rain, animals, fertilization…
Main sources
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Main sources What measures should be taken to avoid/reduce contamination?
Data: Jay, J.M., 1996 e Lacasse, D.. 1995.
Type of product Num. of microorganisms
TomatoNot washed > 1 000 000/ cm2
Washed 400-700/cm2
Collards
External leaves not washed 1 000 000 – 2 000 000/g
Internal leaves washed 200 000 – 500 000/g
Internal leaves 100 – 10 000/g
Table I – Effect of washing on the flora of vegetable products
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• Water- May contain various types of
microorganisms (origin and level of pollution);
- Utilization of potable water!
How to avoid contamination?
Main sources
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•Air
- Non favourable environment for microbial growth;- Excellent conveyer of microorganisms from other sources: sneezing, coughing, agricultural activities …
How to reduce contamination caused by microorganisms transmitted by air?
Main sources
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• Food
Diverse and proper flora :
– Vegetables– Animals
Main sources
Soil Water
Animals
Intestines
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• Handlers- Diverse and own flora (faecal matter
and skin);- Main problems?
• Utensils and Equipments- Do not have own microflora;- Main cause of
CROSS CONTAMINATIONS!!!
Main sources
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• What is “cross contamination”?Microorganisms present in raw foods, utensils and contaminated surfaces are transferred to prepared or washed foods or to clean surfaces..
- What are the main conveyers?- How to prevent/avoid?- Examples
Cross contamination
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• Difference between “Hazard” and “Risk”
- What is the origin of hazards?
- Examples
Risks and hazards
Riscos e Perigos
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Types of hazards
Examples of hazards
Examples of associated foods
Potential illnesses
Salmonella Eggs, poultry, raw milk and milk products
Salmonellosis
Hepatitis A virus Fish, seafood, vegetables, water, fruit, milk
Hepatitis A
Bones, fish bones, glass, metal, stones
Lesions
Aflotoxins Nuts, corn, milk and milk products
Cancer, malformations, alterations of the nervous system diseases; hormonal alterations…
Dioxins Fish, animal fat
Table II – Classification of hazards related to food safety