Fungi Food Microbiology PDF

Fungi (Practical Food Microbiology ) By Nermeen Elshabat  General characteristics of Fungi Kingdom fungi (Mycota) Eukaryotic Achlorophyllous Heterotrophic( Parasitic or Saprophytic or symbiotic ) Cell wall of cellulose or chitin Found in Air , Soil or water…… Mult...

Fungi (Practical Food Microbiology ) By Nermeen Elshabat  General characteristics of Fungi Kingdom fungi (Mycota) Eukaryotic Achlorophyllous Heterotrophic( Parasitic or Saprophytic or symbiotic ) Cell wall of cellulose or chitin Found in Air , Soil or water…… Multicellular ( Aspergillus sp.) or Unicellular (Saccharomyces sp.) Fungal body consists of tiny microscopic filaments called ( Hyphae ). Mycelium is a root like structure of a fungus consisting of a mass of branchinig , thread like hyphae.  Preparation of Fungal media: Media is the nutrient-rich material that provides food to the microbes. ( Ex ) : Potato Dextrose Agar (PDA);Sabouraud Dextrose Agar (SDA). PDA for Litre of distilled water : ( 200 g of Potato \ 20 g Agar \ 20 g Dextrose \ Choramphenicol 0.1 g\L ). Sterilization is carried out with the autoclave at 121⁰C at >15 psi for 15 minutes. Isolation & Inoculation :From different samples Air ,water ,soil or leaves in laminar flow. Incubation : For one week in 28 ⁰C in incubator. Examination & Identification : By Light Microscope by 10X lense then rotate to 40X lens.  Kingdom : Fungi ( Mycota ) Division :Eumycotae Sub-Division Mastigomycotinae Zygomycotinae Ascomycotinae Basidiomycotinae Deuteromycotinae  Penicillium cause citrus fruit rot such as Orange.  Penicillium often spoil refrigerated foods , espicially cheese.  Aspiragillus species often occur in grains , nuts,oil seeds and in certain types of cured meat.  Aspiragillus species are common contaminants of starchy foods such as bred and potatoes.  Microbial Food analysis  Reasons for microbial food analysis: to meet certain set standards to estimate the shelf-life of the product to determine quality of the food for public health purposes  Kinds of Microorganisms 1- The Good (or helpful): Add them to foods or they are there naturally. They ferment foods to unique flavors and textures. Examples: cheese, yogurt, bread, sauerkraut and pickles.  Kinds of Microorganisms 2-The Bad (or spoilage) Change foods and cause them to spoil. Affect the quality of the food product, not the safety of the food. Examples: Discolored, mushy, or fuzzy vegetables; sour milk; and slimy, putrid meat. 3- The Ugly (disease-causing, pathogenic): Cause illnesses that can range from mild to lifethreatening. Examples include foods contaminated with Salmonella or E. coli. Common signs and symptoms include nausea, vomiting, and diarrhea.  Intrinsic and Extrinsic Factors  Intrinsic PH Moisture Content Oxidation-reduction Potential Nutrient Content Antimicrobial Constituents Biological Structures  Extrinsic Factors Temperature Relative Humidity Gases in the Environment Presence of Other Microorganisms  Method for the Microbiological Examination of Foods  Traditional method Plate counts Membrane filtration Most probable number Direct microscopic count Dye reduction tests Indicator  Rapid Method Direct epifluorescent filter technique (DEFT) Electrical impedance Enzyme-linked immunosorbent assay(ELISA)  Controlling Food Spoilage 1- Removal of Microorganisms by filtration. commonly used for water, beer, wine, juices, and other liquids. 2- Low Temperature refrigeration at 5°C retards but does not stop microbial growth. microorganisms can still cause spoilage with extended spoilage. growth at temperatures below 10°C has been observed. 3- Pasteurization kills pathogens and substantially reduces number of spoilage organisms. different pasteurization procedures heat for different lengths of time. 4- Water Availability Dehydration freeze-dried foods is commonly used to eliminate bacterial growth. food preservation occurs as a result of free-water loss and an increase in solute concentration.  Prevention of Foodborne Disease Destroy or remove foodborne disease agents Prevent multiplication of foodborne disease agents Microbiological criteria for raw materials Preservative factors (pH, aw, etc.) Time / temperature (cooking, freezing, etc.) Prevention of cross contamination Food handling / employee hygiene Equipment / environmental sanitation Packaging integrity / storage, distribution Consumer directions for use