FDSCI 600: The good

What is food microbiology?

The study of microorganisms that inhabit, create, or contaminate food.

Why is food microbiology important for food safety?

It helps prevent foodborne illness.

Why is food microbiology important for food quality?

It helps prevent food spoilage.

Why is food microbiology important for food production?

Microorganisms can be used in processes such as fermentation.

Why is food microbiology important for public health?

It helps protect consumers from harmful microorganisms.

What are the 3 major concepts in food microbiology?

Foodborne disease, spoilage, and fermentation.

What types of microorganisms are associated with food?

Bacteria, yeasts, molds, viruses, and parasites.

What are examples of beneficial and harmful microorganisms in food?

Mold can be harmful on bread but beneficial in cheese; yeast can be beneficial in bread but cause spoilage; bacteria can be beneficial or pathogenic.

What is a bacteriophage?

A virus that infects bacteria and can be used to remove harmful bacteria.

How can microorganisms get into food?

They can come from animals, soil, air, ingredients, equipment, or cross-contamination.

What type of microorganism provides gas, volume, and cell structure in donuts?

Yeast.

What type of bacteria can be found in milk-based frosting?

Lactic acid bacteria.

How can mold spores contaminate food?

Mold spores can come from sources such as air or ingredients like sugar.

What is an example of a pathogen that can contaminate cooked grains?

Bacillus cereus.

What are examples of foodborne pathogens mentioned in the notes?

Salmonella, E. coli, Staphylococcus aureus, Bacillus cereus, Listeria, Campylobacter, and Clostridium.

What type of cells are bacteria?

Prokaryotic cells.

What type of cells are fungi?

Eukaryotic cells.

What are viruses?

Acellular infectious agents.

What is a prokaryote?

A cell that lacks a nucleus and membrane-bound organelles.

What structures are found in a typical prokaryotic cell?

Nucleoid, capsule, cell wall, plasma membrane, pili, plasmids, and cytoplasm.

Do prokaryotes have mitochondria?

No.

Do prokaryotes have a nucleus?

No.

How do bacteria reproduce?

Through binary fission.

What is a eukaryote?

A cell that contains a nucleus and membrane-bound organelles.

What structures are characteristic of eukaryotic cells?

Plasma membrane, nucleus, mitochondria, and other membrane-bound organelles.

How do eukaryotic cells divide?

Through mitosis.

What is the function of a bacterial capsule?

Protection and adhesion.

What is the bacterial cell wall primarily made of?

Peptidoglycan.

What is the function of the bacterial plasma membrane?

It forms the boundary of the cell and is involved in cellular processes.

What is the nucleoid?

The region of a bacterial cell containing its DNA.

What is the function of a bacterial flagellum?

Motility.

What is the function of pili and fimbriae?

Attachment.

What is a plasmid?

An extra-chromosomal piece of DNA found in bacteria.

What is an inclusion in a bacterial cell?

A storage structure.

What are the steps of binary fission?

Cell growth → DNA replication → chromosome separation → septum formation → cell division → two daughter cells.

What type of growth results from binary fission?

Exponential growth.

What are the four major bacterial shapes?

Cocci, bacilli, coccobacilli, and spiral.

What are cocci?

Spherical bacteria.

What are bacilli?

Rod-shaped bacteria.

What are coccobacilli?

Short rod-shaped bacteria.

What are spiral bacteria?

Bacteria with a spiral shape.

What are diplococci?

Cocci arranged in pairs.

What are streptococci?

Cocci arranged in chains.

What are staphylococci?

Cocci arranged in clusters.

What are tetrads?

Groups of four cocci.

What are sarcinae?

Cubes of eight cocci.

What are bacterial appendages?

Structures such as flagella, fimbriae/pili, and capsules/glycocalyces that help with motility, attachment, or protection.

What does pleomorphic mean?

Having variable shapes.

What does filamentous mean?

Thread-like in shape.

What are the characteristics of Gram-positive bacteria?

They stain purple and have a thick peptidoglycan cell wall with no outer membrane.

What are the characteristics of Gram-negative bacteria?

They stain pink, have a thin peptidoglycan layer in the periplasm, and have an outer membrane containing LPS.

What are yeasts?

Single-celled fungi.

What are molds?

Filamentous fungi composed of hyphae.

What are hyphae?

Filamentous structures that make up molds.

What is a mycelium?

A network of hyphae.

What is the typical appearance of molds?

Fuzzy or cotton-like.

How do yeasts commonly reproduce asexually?

By budding or binary fission.

What is budding in yeast?

A new cell, or bud, forms from a parent cell, grows, and separates.

What are the steps of yeast budding?

Parent cell → bud forms → bud grows → bud separates → chains may form.

What are the steps of sexual reproduction in yeast?

Two haploid mating cells → plasmogamy → karyogamy → meiosis → haploid spores.

What are the steps of mold growth?

Spore lands → germination → hyphal growth → mycelium formation → sporulation.

What are the phases of the bacterial growth curve listed in the notes?

Lag, stationary, and death.

What is generation time?

The time required for one cell to divide and produce daughter cells; for a population, the time required for the entire population to double.

What does a short generation time indicate?

Fast growth.

What does a long generation time indicate?

Slow growth.

What is the specific growth rate (μ)?

The increase in biomass or cell number per unit time during exponential growth.

What does N1 represent in population growth calculations?

The concentration at time 1.

What does N2 represent in population growth calculations?

The concentration at time 2.

What does t represent in population growth calculations?

Time.

What factors determine whether microorganisms can survive and grow in food?

A combination of intrinsic and extrinsic factors.

What are intrinsic factors?

Factors inherent to the food, including pH, water activity, natural antimicrobials, nutrient requirements, and redox potential.

What are extrinsic factors?

Factors outside the food, including gaseous environment/packaging, relative humidity, temperature, and the presence of other bacteria.

What are the major intrinsic factors affecting microbial growth?

pH, water activity, natural antimicrobials, nutrient requirements, and redox potential.

What is pH?

A logarithmic measure expressing acidity or alkalinity.

What pH do most microorganisms prefer?

Approximately pH 6–7.

Below what pH can most foodborne pathogens not grow?

Below pH 4.4.

Above what pH can most foodborne pathogens not grow?

Above approximately pH 8–9.

What microorganisms can grow in more acidic foods?

Lactic acid bacteria and spoilage fungi.

What is water activity (aw)?

The energy of water in foods and a measure related to the relative humidity of the surrounding air.

What is the scale for water activity?

0.00–1.00.

What water activity supports growth of most microorganisms?

Approximately 0.91–0.98.

What water activity supports growth of most yeasts?

Approximately 0.88.

What water activity supports growth of molds?

Approximately 0.80.

What determines which microorganisms can grow in a food?

The nutrients available in the food and the microorganisms' unique nutrient requirements.

What nutrients are important for microbial growth?

Carbon, nitrogen, lipids, water, vitamins, and minerals.

What is catabolism?

The breakdown of molecules to release energy.

What is anabolism?

The building of cellular components using energy.

How do prokaryotes make ATP?

Through the electron transport chain.

What is redox potential?

The tendency of a substance or system to gain or lose electrons.

What happens during oxidation?

A substance loses electrons.

What happens when another species gains electrons?

It undergoes reduction.

What are obligate aerobes?

Microorganisms that require oxygen.

What are facultative anaerobes?

Microorganisms that prefer oxygen but can grow without it.

What are microaerophiles?

Microorganisms that require low levels of oxygen.

What are aerotolerant microorganisms?

Microorganisms that do not use oxygen but can tolerate it.

What are obligate or strict anaerobes?

Microorganisms for which oxygen is toxic.

What temperature range is listed for thermophiles?

55–65°C.

What temperature range is listed for mesophiles?

30–40°C.

What temperature range is listed for cold-tolerant psychrophiles?

20–30°C.

What temperature range is listed for cold-loving psychrophiles?

10–15°C.