Microbiology and Processing of Milk

A comprehensive set of vocabulary flashcards covering milk microbiology, bacterial growth kinetics, preservation methods, heat treatment, and mechanical processing steps like centrifugation and homogenization.

Microbial hygiene

The control of microorganisms in milk to ensure good hygienic quality.

Protists

A term suggested for single-celled organisms that do not fit into plant, animal, or fungi categories.

Eukaryotes (Higher Protists)

Cells similar to animals and plants that possess a real nucleus surrounded by a membrane and contain organelles like mitochondria or chloroplasts.

Prokaryotes (Lower Protists)

Organisms such as bacteria and cyanobacteria where the DNA lies free in the cytoplasm without a nucleus or organelles.

Staphylococcus

A bacterial form characterized by clusters of spherical cells (cocci).

Binary Fission

A form of asexual reproduction where one bacterial cell divides into two identical daughter cells.

Endospores

A highly resistant dormant stage formed by some bacteria, such as $Bacillus$ and $Clostridium$, to survive harsh conditions.

Gram-positive bacteria

Bacteria characterized by a thick peptidoglycan layer in the cell wall that retains violet stain during Gram staining.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer that are decolorized by alcohol and take a red stain ($\text{safranin}$) during Gram staining.

Glycocalyx

Extracellular slime material covering many bacteria.

Yeasts

Eukaryotic microorganisms that are ovoid or elliptical in shape and can grow in both aerobic and anaerobic conditions.

Molds

Strictly aerobic microorganisms that form elongated, branched filaments called hyphae.

Mycelium

Tangled masses of mold hyphae that often appear cottony or powdery.

BactoScan

A rapid method for bacterial enumeration that uses fluorescent staining to ensure only live bacterial cells are counted.

Generation time ($g$)

The time required for a bacterial population to double, calculated as $g = t/n$.

Lag phase

The first phase of the bacterial growth curve where the population adapts to the environment.

Psychrophiles

Cold-loving bacteria that grow in the temperature range of $0\text{--}20\text{ }^{\text{o}}\text{C}$.

Mesophiles

Moderate-temperature bacteria growing between $20\text{--}45\text{ }^{\text{o}}\text{C}$, which includes most human pathogens.

Thermophiles

Heat-loving bacteria that grow in the temperature range of $45\text{--}60\text{ }^{\text{o}}\text{C}$.

Lactoferrin

A natural inhibitor in milk that binds iron to inhibit bacterial growth.

Food infection

An illness where the food acts as a carrier for a microorganism, such as $Salmonella$.

Food poisoning

An illness caused by a microorganism forming a toxin in the food, such as $Staphylococcus\text{ }aureus$.

Thermalization

A mild heat treatment at $60\text{--}69\text{ }^{\text{o}}\text{C}$ used primarily to kill psychrotrophs.

Quality Assurance (QA)

A coherent system of activities that guarantees products meet defined quality marks, often defined as "fitness for use."

HACCP

Hazard Analysis and Critical Control Points; a systematic method to ensure product safety by identifying and controlling potential hazards.

Low Pasteurization

Heat treatment for $30\text{ min}$ at $63\text{ }^{\text{o}}\text{C}$ or $15\text{ s}$ at $72\text{ }^{\text{o}}\text{C}$ to inactivate alkaline phosphatase and kill pathogens.

High Pasteurization

Heat treatment for $20\text{ s}$ at $85\text{ }^{\text{o}}\text{C}$ (up to $100\text{ }^{\text{o}}\text{C}$) used to destroy lactoperoxidase and kill vegetative microorganisms.

Heat Coagulation Time (HCT)

The time required for visible coagulation to occur in milk during heat treatment.

D value

The decimal reduction time; the time needed to reduce a bacterial population by 90\text{%} (one log cycle).

Z value

The temperature rise needed to increase a reaction rate by a factor of $10$.

$$Q_{10}$$

The factor by which a reaction rate increases when the temperature is raised by $10\text{ }^{\text{o}}\text{C}$.

Heat regeneration ($R$)

The process of regaining heat and saving cooling energy, calculated as $R = \frac{T_{reg} - T_{inl}}{T_{max} - T_{inl}}$.

Bactofugation

A process using a centrifugal separator to remove bacteria and spores from milk.

Homogenization

The process of disrupting milk fat globules into smaller ones to counteract creaming and improve stability.

Homogenization clusters

Structures where fat globules are connected by casein micelles due to insufficient surface coverage and collisions during homogenization.