Introduction to food hygiene Flashcards
is a subject that has a considerable scope. Food should be nourishing and attractive. It must be visibly clean and free of contaminating substances. The aim of food hygiene is the production and service of food that is safe, clean, sound and
fit for consumption.
food hygiene
These are microscopic plants composed of filaments (long threads or hyphae) and
masses of hyphae make up the body of the “plant”, known as the mycelium.
Molds
The growth of molds on food is usually readily recognized by its
“fuzzy” or cottony
appearance.
Most molds grow best at temperatures in the range of
20-30°C
Black spot, due to the growth of
Cladosporium
microscopic plants, but unlike the molds, are singlecelled living organisms. They are slightly bigger than bacteria.
Yeasts
The most common means of yeast production is by
budding
are very small, single-celled living organisms. They are smaller than yeast
cells, varying in size from 0.2-5 microns, with an average size of 1.5 microns.
Bacteria
Bacteria reproduce by
binary fission
4 Phases in Growth Pattern
- Lag
- log
- stationary
- death
period of adjustment for bacteria in their new environment, when cell damage is repaired and the bacteria adapt to utilise the nutrients now available; there is no growth or even a decline in numbers.
Lag phase
(logarithmic or exponential phase) is the period of growth when bacterial cells begin to divide by binary fission; the rate of multiplication is most rapid and is constant.
Log phase
period when as many cells are dying off as they are being
formed, thus numbers remain constant.
Stationary phase
period when bacterial numbers decrease as they eventually start
to slowly die off in excess of multiplication.
death phase
The most relevant phases are the
lag and log phases
FACTORS AFFECTING THE NUMBERS OF BACTERIA:
- Initial numbers
- Temperature
- Moisture
- pH
- Gaseous environment
One of the most important factors governing growth of microorganisms is
Temperature
are the largest group and include most of the pathogenic bacteria
mesophilic bacteria
Mesophilic bacteria are:
Salmonella, Staphylococcus, Shigella, the coliforms etc. (S.S.T.C)
The psychrotrophic bacteria are commonly found in
soil, water, and vegetation
A term that is now widely used in the context of water relationships between food and spoilage organisms is
water activity
4 Gaseous environment:
- Aerobic
- Anaerobic
- Facultative anaerobic
- Microaerophilic
those either preferring to grow or needing to grow in an atmosphere containing oxygen.
Aerobic
those requiring an atmosphere devoid of oxygen for growth. These are, in fact, inhibited by oxygen
Anaerobic
those preferring an atmosphere devoid of oxygen, but able to grow, at a reduced rate, in the presence of oxygen
facultative anaerobic
those preferring a reduced oxygen concentration, but not necessarily an absence thereof. Oxygen at the partial pressure of the normal atmosphere inhibits them
Microaerophilic
Common Method of food preservation:
Acidifying or Pickling
Yeasts generally are inhibited at temperatures
above 37°C
The psychrotrophic species which form the major component of meat spoilage floras include:
Pseudomonas, Moraxella, Acinetobacter, Lactobacillus, Microbacterium thermosphactrum
