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    Presentationgm3031 201207103010

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    Presentationgm3031 201207103010

    Uploaded by

    Bina Khan
    3 views26 pages

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    presentationgm3031-201207103010 (1)

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    3 views26 pages

    Presentationgm3031 201207103010

    Uploaded by

    Bina Khan

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    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 26

    Microorganisms in food

    ANJALI SHARMA
    M.Sc.

    DEPARTMENT OF MICROBIOLOGY
    MEERUT INSTITUTE OF ENGINEERING AND TECHNOLOGY
    WHAT IS FOOD MICROBIOLOGY ?

     “Food microbiology is the discipline that


    includes the microbiological aspects of food
    spoilage and food-borne diseases and their
    effective control and bioprocessing of foods for
    human and animal consumption , in addition to
    the basic information of microbial physiology ,
    metabolism and genetics”.
    DEFINITIONS …

     SPOILAGE : bad food microbiology

     undesirable changes to food; sour milk,


    moldy bread.

     preservatives and refrigeration inhibit the


    growth of microorganisms
     FERMENTATION : good food microbiology

     foodthat have been intentionally altered


    such as sour cream, cheese,beer.
     anydesirable change a microorganism makes
    to food.
     TOXINS : bad food microbiology

     Toxin [L. Toxicum = poison ] any substance


    that is poisonous to other organisms .

     Can induce the disease in the absence of the


    toxin – producing organisms .

     E.g. – 1) botulinum toxin causes botulism ,


     2) salmonella toxin causes salmonellosis
    .
    FOOD POISONING : bad food
    microbiology

    Or food intoxication is a food borne


    disease that results from ingestion of
    exotoxin secreted by bacterial species
    growing on food .
    For example : botulism , or
    staphylococcal food poisoning .
    Microorganisms in food .
     There are three main sort of microorganisms
    present in the food , they are as follows :-
    1. BACTERIA
    2. MOLDS
    3. YEAST {FUNGI}

     While other can be consideration as parasites ,


    protozoan , viruses as well as algae .
    BACTERIA
    • Rod, spiral, spherical, comma shaped with or
    without flagella.
     Covered with endospores that protect them from
    changess in temperature.
     They divide every 20 mts.
     Uses: converts ethyl alcohol to acetic acid. This
    helps in preparation of vinegar and also idli,
    dhokla, curing coffee and cocoa beans.
     Some are used in developing stabilizers for
    preparation of jelly and ice creams .
     Diseases caused are sore throat, cholera,
    syphilis,typhoid, dysentery and food poisoning.
    Figure : common bacteria infecting human
     Harmful effects

     Spoil food by producing acid .


     Slime or rope as in curd
     Putrefy food products leading to bad odour
    FUNGI ARE LOWER PLANTS THAT LACK
    CHLOROPHYLL .
    YEASTS :

     Unicellular(single cell).
     Grow in foods high jams, bread in sugar and
    salts
     Colour less,white in colour.
     Not harmful, mostly useful.
     Like A Phalloides
     MOULDS:

     Multi cellular (many cells)


     grow on pickles,cheese.
     red, pink, blue, yellow, black,
     produce toxins like alfa toxins, Parasitic
    ringworms.
    USES OF YEAST :

    Yeast ferments sugar to alcohol and carbon dioxide.


    It is rich in B complex.
     Yeast grown on industrial waste is used for
    making Beer and wine.
    ALGAE :
     Are both unicellular and multi cellular.
     Usually green in colour( red also) and found in water.
     Usually not pathogenic, but some of them have an
    unpleasant odours.
     Uses: important source of agar.Agar is used as a veg
    substitute for gelatin in preparation of desserts.
     In water purification and sewage treatment plants. They
    are a source of food to the aquatic animals.
     Blue green algae are used as fertilizers.
     Alginic acids and its salt are used in ice cream
    preparation to prevent crystallization and give it smooth
    texture.
     Also used in preparation of cheese.
    PARASITES /PROTOZOAN :
     Parasites are micro organisms dependent on living
    organisms for thei growth.

     Unicellular and parasitic in nature.


     Used as source of food by aquatic animals.
     Harmful protozoa cause amoebic dysentery and
    contaminated water or salad vegetable cause mlalarial
    fever.
     Contaminated meat of pigs (uncooked pork) can infect
    humans and cause gastrointestinal diseases.
     It causes cysts and also muscularspasms.
    FACTORS RESPONSIBLE FOR THE
    GROWTH OF MICROBES :
     Food and nutrients:
     They need protein andcarbohydrates to grow.

     pH level:
     Neutral pH is ideal for their growth .
     Moulds and yeast grow well in acidic medium 4 -4.5
     In general a majority of the microbes will not grow in high pH
    levels.
     Foods like pickles have a better keeping quality because of high pH.
     Moisture:
     water is the main constituent of the living cell.
    Salt and sugar are hygroscopic substances. They
    bind water, thus making it unavailable to
    microbes. Squashes stay longer for the same
    reason.

     Temperature:
     temp range of 5- 63 degrees is called danger zone.
    Above and below this a number of microbes die.

     Oxygen:
     Moulds and yeast grow best in the presence of
    oxygen. Only some bacteria are aerobic
     Time:

    Microbes multiply very fast in a very short time
    given favourable conditions.

     Osmotic pressure:
     Presence of sugar and salt has an osmotic effect on
    the food. Moulds and yeasts grow fast on pickles
    and jams also.

     Sunlight and UV rays:


     well lit and well ventilated areas inhibit the
    growth of microbes. UV rays sterilize food
    partially as their penetrating power is low.

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