Food Microbiology L2 PDF

L2 FOOD MICROBIOLOGY Is a branch of microbiology that studies variety of microorganism involved in the spoilage of food, manufacture of food and transmission of disease via food. APPLICATION Study of MOS causing spoilage...

L2 FOOD MICROBIOLOGY Is a branch of microbiology that studies variety of microorganism involved in the spoilage of food, manufacture of food and transmission of disease via food. APPLICATION Study of MOS causing spoilage Study of pathogen that cause disease through food when it is not cooked properly Production of fermented products- cheese, yogurt, wine. Etc., Miscellaneous-like probiotics FOOD SAFTY Refers to handling, preparing and storing of food in a way to reduce the risk of individual becoming sick from food borne illnesses 4 steps: cleaning-separate-cook-chill FOOD SPOILAGE Defined as the change in quality of food that makes its unfit for consumption Only those with shortest generation time under storage condition attain the numbers rapidly and cause spoilage TYPES OF MICROORGANISMS ON FOOD Mainly 3 group 1) Molds Generally concerned with spoilage of food Food industry use is limited Eg: Molds ripened cheese 2) Yeast Most widely used MOS in food industry Ability to ferment sugars to ethanol and carbon dioxide Bakers yeast, protein source 3) Bacteria Generally associated with spoilage Beneficial: Lactobacillus, Leuconostoc BACTERIAL CELLS  Unicellular Prokaryotic Size: 0.5-1 to 2-10 micron 3 morphological forms (spherical ---cocci, rod---bacilli, curved---comma) Can be motile or non-motile Cytoplasmic material inside rigid wall and a membrane beneath Nutrients in molecular and ionic forms are transported from environment through membrane The intrusion in the cytoplasm- Mesosome Cytoplasmic material is immobile and doesn’t contain organelles enclosed in separate membrane 70 s ribosome – dispersed in cytoplasm Genetic material- circular, not enclosed in nuclear membrane and do not contain basic proteins such as Histones Cell division – binary fission Gene transfer and genetic recombination is there but there is no gamete or zygote formation Prokaryotic cells also have flagella, capsule, surface layer protein and pili for specific function Some produces endospores BACTERIA CAUSING FOOD SPOILAGE Spoilage bacteria- Leuconostoc spp., Lactobacillus spp. Produce ---- off-flavour, off-odour, slime production, discolorations, gas production, decrease in PH Due to ---rapid growth rate of bacteria, ability utilize the food nutrients, ability to grow under wide range of temperature, aerobiosis, PH and water activity IMPORTANT BACTERIAL GROUPS Sl. Group Name Eg: Characters No. 1 Lactic acid bacteria Lactococcus, Lactobacillus Carbohydrate----LA 2 Acetic acid bacteria Acetobacter aceti Form AA 3 Propionic acid Propionibacterium freudenreichii Propionic acid bacteria Used in diary fermentation 4 Butyric acid Clostridium butyricum Butyric acid bacteria 5 Proteolytic bacteria Pseudomonas, flavobacterium Hydrolyse protein Produce extracellular proteinases 6 Lipolytic bacteria Pseudomonas, flavobacterium Hydrolyse triglycerides Produce extracellular lipases 7 Saccharolytic Pseudomonas, Bacillus, Hydrolyse complex carbohydrates bacteria Clostridium 8 Thermophilic Bacillus, clostridium Grow @ 50 degree Celsius and above bacteria 9 Psychrotrophic Bacillus, clostridium Grow under refrigerated temp bacteria 10 Thermoduric Micrococcus, enterococcus Able to survive pasteurisation temp bacteria treatment 11 Halotolerant Bacillus, micrococcus Able to survive high salt bacteria concentration (≤10%) 12 Aciduric bacteria Lactococcus, enterococcus Able to survive under low pH, less than 4 13 Osmophilic Lactobacillus, Leuconostoc Grow relatively high osmophilic bacteria environment (less osmophilic than yeast and molds) 14 Gass producing Lactobacillus, Leuconostoc Produce gass-C02, H2, H2S bacteria 15 Slime producers Lactobacillus, Leuconostoc Produce slime- because of the production of polysaccharides 16 Spore formers Bacillus, clostridium, 4 type desulfotomaculum a) Aerobic spore formers b) Anaerobic ,, c) Flat sour ,, d) Thermophilic ,, e) Sulphide producing ,, 17 Aerobes Pseudomonas, flavobacterium, Require oxygen for growth and bacillus development 18 Anaerobes Clostridium Can’t grow in presence of oxygen 19 Facultative Lactobacillus, Leuconostoc Able to grow in both presence and anaerobes absence of oxygen 20 Coliforms Escherichia, enterococcus Used as index sanitation 21 Facal coliforms Escherichia coli Used as index sanitation 22 Enteric pathogen Salmonella, shigella, Escherichia, Cause gastrointestinal infection vibrio SPORE FORMERS Mainly 2 groups Aerobic – bacillus & anaerobic – clostridium Thermophilic acidophilic spore- forming bacteria---Alicyclobacillus –cause soilage of acidic beverages-----grow without producing gas and no change in the appearance--- this spoilage only when the consumer open and begins to consume the products Bakery products---spoiled by----Bacillus species Refrigerated vacuum- packed meat---Clostridium PATHOGENIC NON-SPORE FORMING BACTERIA Eg: Brucella spp. Eg: Salmonella spp. Eg: Escherichia Coli spp. PATHOGENIC SPORE FORMING BACTERIA Bacillus spp. -Bacillus cereus ---diarrheal & emetic type Clostridium spp. – rod shaped, gram + ve----Clostridium botulinum, clostridium tetani, clostridium butyricum YEAST AND MOLDS Eukaryotic Yeast—unicellular Molds---multicellular Larger (20-100mm) Have rigid cell wall and thin plasma membrane Cell wall does not have mucopeptide, is rigid and is composed of carbohydrates Plasma membrane contains sterol Cytoplasm mobile and contain organelles that are membrane bound Ribosome- 80 s – attached to endoplasmic reticulum DNA linear, contains histones and enclosed in nuclear membrane Cell division – mitosis (Asexual), Meiosis (Sexual)  YEAST Cells oval, spherical or elongated about 5-30 ¥ 2-10 mm in size Non motile Cell wall contain polysaccharides, proteins, and lipids Wall can have scars indicating the site of budding The membrane beneath the wall Cytoplasm –finely granular ribosomes and organelles Nucleus well defined with nuclear membrane Yeast – fungi , grow solitary , produces by Budding --- either Ascomycetes( SACCHARONYCES,CANDIDA) or Basidiomycetes(RHODOTORULA, FILOBASIDIELLA) MOLDS Multicellular Filamentous fungi Growth on food readily visible (pigmented mycelium) Non- motile, filamentous branched Cell wall- cellulose, chitin or both Large number of filaments—hyphae Aggregate of hyphae--- mycelium Hyphae can be non-septate, septate- uninucleate or septate- multinucleate Free- conidia, sack- sporangium MUCOR--- Cheese ripening Mucor indicus , Mucor racemosus--- benefits to food industry Aspergillus, Rhizopus --- spoilage of food VIRUSES Hepatitis A, E & Norovirus PARASITES Trichinosis Raw or undercooked meat infected with- Trichinella spiralis Helminths Taeniasis Result of ingesting tissue cyst of either T. saginata from cows, T. solium or T. asiatica from pork Anisakiasis Caused by Anisakid nematodes that can invade the stomach or intestine of humans The transmission occurs when infective larvae are ingested from fish or squid that humans eat raw or under cooked  Cryptosporidiosis Cause diarrheal disease—Cryptosporidium Epigastric cramping, nausea, and anorexia Cyclosporiasis Food or water contaminated with feces is consumed- cyclospora cayetanensis characterized by mild-to-severe nausea, anorexia, abdominal cramping, mild fever, and watery diarrohea. Toxoplasmosis y ingestion of food and water containing oocysts, ingestion of animal tissues containing cystic forms or transplacental Protozoa transmission-- Toxoplasma gondii Giardiasis ingestion of contaminated water or food or direct fecal-oral (Giardia) transmission. chronic diarrhea. Symptomatic patients present with loose, foul- smelling stools, and increased levels of fat and mucus in fecal samples. Flatulence, abdominal cramps, bloating, nausea, anorexia, and weight loss are common. Fever is occasionally present at the beginning of the infection--- (G. muris, G. lambia, G. agilis, G. ardeae, and G. psittaci)