BIOLOGY 2250

MICROBIAL GROWTH and ITS CONTROL

BIOLOGY 2250

PART 1. MICROBIAL GROWTH

Requirements for Growth

Physical Requirements – Temperature, pH, Osmotic PressureChemical Requirements – Carbon, Nitrogen, Sulfur, Phosphorous, Trace Elements, Oxygen, Organic Growth Factors

Temperature Requirements

Mesophiles

Psychrophiles

Psychotrophs

Thermophiles

Hyperthermophiles

TEMPERATURE OF FOODS

OSMOTIC PRESSURE

OXYGEN REQUIREMENTS

BINARY FISSION

Little increase in sizeGrowth in numbers to form colonies on an agar plate

How about these numbers!

BACTERIAL GROWTH

GROWTH PHASES

BIOLOGY 2250

PART 2. CONTROL OF MICROBES

TERMINOLOGY

MICROBIAL DEATH

Types of Cell Damage

Alterations of Plasma Membrane

Damage to Proteins and Nucleic Acids

PHYSICAL METHODS OF CONTROL

Moist heat

Dry heat

Filtration

High pressure

Desiccation

Osmotic pressure

radiation

Moist Heat

Autoclave

Principle of Autoclave

Adjust your recipe to your altitude!

Dry Heat

Oven

Bunsen burner flame

FILTRATION

Membrane filters have different pore sizes, e.g. 0.45 µ’s

High Pressures

Fruit Juices

Desicattion

Freeze Dried Foods

Dried Meats

Dried Fruits

Osmotic Pressure

Salting –

Pickling -

RADIATION

Ionizing – cobalt, gamma rays

Nonionizing – UV light

Microwave

CHEMICAL CONTROL

CHEMICAL CONTROL