Food Safety Training Course Co-financiado:. Microorganisms and food.

Food SafetyTraining Course

Co-financiado:

Microorganisms and food

5| 25 Microorganisms and food

• What are they?• Main characteristics of living

beings?• Functions and applications?

Microorganisms


• What do you understand by microbial growth?

• What factors affect microbial growth?

• How can we control the growth?

Microbial Growth


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


TemperatureTemperature is one of the most relevant factors for microbial growth .


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);


Microbial growth factors - Temperature

Adapted from: Adams, M.R. and Moss, M.O., 1995


Microbial growth factors – Hurdle effect

• Main groups with importance for FS:– Bacteria

• Main characteristics

– Fungi (Molds and yeasts)• Main characteristics

Microorganisms


• Unicellular;• Various forms (cocci, bacilli, spirilla);• Some develop resistant structures

(spores);• Main cause of food intoxications of

biological origin.

Bacteria


Bacteria

Photos: www.denniskunkel.com


Fungi(molds and yeasts)


• 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.


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.


Molds and yeasts

Mold on food


• 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


• Soil- Source of spore forming bacteria, fungi

and yeasts;- Addition of manure – faecal

microorganisms;- Dissemination of microorganisms:

wind, rain, animals, fertilization…

Main sources


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


• Water- May contain various types of

microorganisms (origin and level of pollution);

- Utilization of potable water!

How to avoid contamination?

Main sources


•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


• Food

Diverse and proper flora :

– Vegetables– Animals

Main sources

Soil Water

Animals

Intestines


• 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


• 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


• Difference between “Hazard” and “Risk”

- What is the origin of hazards?

- Examples

Risks and hazards

Riscos e Perigos


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

Food Safety Training Course Co-financiado:. Microorganisms and food.

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