Food 2420 Midterm Review Class PDF

FOOD*2420 Midterm Review Class Midterm details The Midterm Exam is on Oct 11, from 4:00 PM to 5:00 PM The Midterm Exam will cover the first 3 Units of the course The Midterm exam will be delivered online via the Quizzes tool The exam is 1 hour in length (89 multiple choice questions and 2...

FOOD*2420 Midterm Review Class Midterm details The Midterm Exam is on Oct 11, from 4:00 PM to 5:00 PM The Midterm Exam will cover the first 3 Units of the course The Midterm exam will be delivered online via the Quizzes tool The exam is 1 hour in length (89 multiple choice questions and 2 short answer) Before you take the online final exam for this course, you MUST complete the Practice Test (found by going to Tools>Quizzes) You may use a calculator during the exam Microbiology: History (Chapter 1) 1676-1683: Antony van Leeuwenhoek observed bacteria in saliva, rainwater, vinegar, and other materials Sketched the three morphological groups (spheroids or cocci, cylindrical rods or bacilli and spiral or spirilla) He also described some bacteria as being motile Microbiology: History 1861: Louis Pasteur demonstrated that, in a boiled infusion, bacteria could grow only if the infusions were contaminated with bacteria carried by dust particles in the air He proved that bacteria were able to reproduce (biogenesis), and life could not originate by spontaneous generation Microbiology: History WHILE WORKING AT A UNIVERSITY IN LILLE, FRANCE, HE SPOKE WITH A BREWER, WHO WANTED TO KNOW MORE ABOUT WHY THE DRINKS HE MADE SOMETIMES WENT SOUR PASTEUR USED MICROSCOPES AND THE SWAN NECK FLASK IN HIS WORK WHEN AIR ENTERED THE LONG NECK, TINY PARTICLES (BACTERIA) WERE TRAPPED IN THE LONG TUBE IF THEY COULD NOT REACH THE LIQUID, NO SOURING TOOK PLACE WHEN THE FLASK WAS TIPPED AND THE PARTICLES WERE ABLE TO REACH THE LIQUID, IT WOULD TURN SOUR Microbiology: History Between 8000 and 1000 b.c., many food preservation methods were developed including: Drying, cooking, baking, smoking, salting, Sugaring, low-temperature storage (in ice), storage without air (in pits), fermentation Pickling, and spicing These approaches were likely developed to delay food spoilage Types of Microorganisms (Chapter 2) Yeasts and Molds: Yeasts and molds are eukaryotic Eukaryotic cells are much larger (20–100 μm) than prokaryotic cells (1–10 μm) Yeasts are unicellular, molds are multicellular Eukaryotic cells have rigid cell walls and thin plasma membranes The cell wall does not have peptidoglycan, is rigid, and is composed of carbohydrates. The plasma membrane contains sterol The cytoplasm contains organelles (mitochondria, vacuoles) Types of Microorganisms (Chapter 2) Molds are nonmotile, filamentous, and branched The cell wall is composed of cellulose, chitin, or both A mold is composed of large numbers of filaments called hyphae Types of Microorganisms (Chapter 2) Bacteria are unicellular, 0.5–1.0 × 2.0–10 μm in size There are 3 forms: spherical (cocci), rod shaped (bacilli), and curved (spiral) The don’t have organelles in their cytoplasm Types of Microorganisms (Chapter 2) Gram positive vs Gram negative Types of Microorganisms (Chapter 2) Viruses are regarded as noncellular entities or particles Bacterial viruses are called bacteriophages Very important in food microbiology are widely distributed in nature They are composed of nucleic acids (DNA or RNA) surrounded by several proteins that form a capsid Some bacteriophages have another layer surrounding the capsid called an envelope These bacteriophages are called enveloped viruses Types of Microorganisms (Chapter 2) Several viruses have been identified as causing foodborne diseases in humans The two most important viruses that cause foodborne outbreaks are hepatitis A and norovirus Both have single-stranded RNA encased in a capsid Protozoan parasites are eukaryotic cells Some are associated with water and foodborne outbreaks linked to fresh produce especially Wild animals, livestock, pets, and humans carry these parasites and serve as a source Contaminated soil and irrigation water are environmental sources contamination Types of Microorganisms (Chapter 2) Know some examples of molds, yeasts, bacteria, viruses and parasites that are important in food microbiology Know important bacterial groups in foods Microbial Sporulation and Germination (Chapter 9) Molds, some yeasts, and some bacteria form spores Molds form spores by both asexual and sexual reproduction Yeasts that form spores (sexual ascospores) are known as Ascomycetes (true yeasts) Ascospores form by the conjugation of two yeast cells Only a few bacterial genera form spores Foodborne sporeformers include Bacillus, Alicyclobacillus, Clostridium, and Desulfotomaculum Microbial Sporulation and Germination (Chapter 9) Bacterial cells produce endospores (inside a cell and one spore per cell) Spores are much more resistant to physical and chemical antimicrobial treatments than vegetative cells The spores are metabolically inactive or dormant and can remain in dormant form for years but are capable of emerging as vegetative cells (one cell per spore) in a suitable environment  Microbial Sporulation and Germination (Chapter 9) Cell multiplication (1–4) and endospore formation, germination, and outgrowth of spore-forming bacteria (5– 13) Different steps are (5) formation of axil filament, (6) septation, (7) prespore formation, (8) cortex formation,(9) coat formation, (10) free spore, (11) germination following activation, (12) swelling of spore, (13) outgrowing cell Microbial Sporulation and Germination (Chapter 9) Foods can be contaminated by their spores rather easily from various sources In a suitable food environment, spores will germinate, grow, and produce undesirable (or desirable) effects Mold and yeast spores are sensitive to heat, and their growth can also be prevented by storing foods in the absence of air Microbial Sporulation and Germination (Chapter 9) Bacillus, Clostridium, and Desulfotomaculum are associated with food spoilage and foodborne diseases As a result of high heat resistance, these spores are of special interest and importance in food processing In the canning of low-acid foods, very high heat treatment is employed to achieve commercial sterility that kills spores of all pathogenic bacteria Nitrites (in processed meat), low pH (acid products), low AW, or high salt are used individually or in combination to prevent spore germination Sources of Microorganisms in Foods (Chapter 3) Sources of Microorganisms in Foods (Chapter 3) Animals, Birds, Fish, and Shellfish Air Soil Sewage and manure Water Humans Food ingredients Food processing or harvesting equipment Microbial Growth Characteristics (Chapter 5) The time that a single cell takes to divide into two is called generation time or doubling time G is generation time (with time unit in minutes) 0.3 is a constant value t is the duration of study (minutes) log10 x is initial, and log10 z is the final cell numbers per milliliter or colony-forming units (CFUs), per milliliter Microbial Growth Characteristics (Chapter 5) If a pure culture of a bacterial population during incubation at 35°C in a nutritionally rich broth increases to 5 × 106 CFU/mL from an initial population of 2.5 × 102 CFU/mL in 300 minutes, what is the generation time of the strain? Microbial Growth Characteristics (Chapter 5) G = 0.3 x 300 (minutes) log10 (5 × 106) - log10 (2.5 × 102) G = 90 (minutes) 6.70 - 2.40 G = 20.9 minutes Microbial Growth Characteristics (Chapter 5) Factors Influencing Microbial Growth in Food (Chapter 6) The intrinsic factors of a food include nutrients, growth factors, inhibitors (or antimicrobials), water activity, pH, and oxidation– reduction potential (Eh) Extrinsic factors important in microbial growth in a food include the environmental conditions in which it is stored These are temperature, relative humidity, and gaseous environment The relative humidity and gaseous condition of storage, respectively, influence the AW and Eh of the food Microbial Metabolism of Food Components (Chapter 8) Metabolism of Food Carbohydrates including Degradation of Polysaccharides Degradation of Disaccharides Degradation of Monosaccharides Fermentable monosaccharides are metabolized by five major pathways including The Embden-Meyerhoff-Parnas (EMP) pathway The hexose monophosphate shunt (HMP) pathway The Entner-Doudroff (ED) pathway Two phosphoketolase (PK) pathways (pentose phosphoketolase and hexose phosphoketolase) Microbial Metabolism of Food Components (Chapter 8) End Products of Carbohydrate Metabolism by Some Microorganisms Food Biopreservatives of Microbial Origin, Bacteriocin, and Nanotechnology (Chapter 17) Antimicrobial Compounds of Food-Grade Bacteria Food Biopreservatives of Microbial Origin, Bacteriocin, and Nanotechnology (Chapter 17) Organic Acids, Diacetyl, Hydrogen Peroxide, and Reuterine as Food Preservatives What bacteria are they active against? Bacteriocins of Lactic Acid Bacteria as Food Preservatives Which bacteria produce them and how are they used in foods? Food Ingredients and Enzymes of Microbial Origin (Chapter 18) Microbial Proteins and Food Additives (Amino acids) Organic Acids Microbial Enzymes in Food Processing Questions?