Chapter 9 Flashcards
(218 cards)
Green patches on potatoes indicate increased levels of solanine, which is a
glycoalkaloid poison that might pose a risk to human health. Solanine is an
example of a …… present in food.
a. Environmental contaminant b. Natural toxin c. Harmful additive
A
In solutions with high concentration of salt, bacteria lose water due
to high …… pressure in the solution. (one word, small letters)
Osmotic
What is the major means of food preservation
Thermal (heat) processing
What is the utility of heat processing
Heat can denature proteins , inactivate enzymes , and gelatinize
starches.
Heat kills microorganisms by denaturing their proteins and
inactivating their enzymes
3 basic levels of heat treatment
Sterilization (hospital) Commercial sterility (food) Pasteurization/blanching
definition of sterility
: No living forms are alive or biologically
No spores, no vegetative cells
When sterility is achieved
Sterility can only be considered achieved when all parts of a product
have been heated to 121 C (reached by using steam) and held at that
temperature for 15 min
Why sterilization is used only in labs and hospitals
Under these very harsh conditions, foods would effectively become
inedible and of very poor nutritional quality
Commercial sterility refers to
Canning processing
Definition of commercial sterility
Definition of commercial sterility: all pathogenic and toxin forming
vegetative organisms are killed and their spores are inactivated, to
the extent that they cannot reproduce.
Commercial sterility is a practical level of sterility that ensures safety
while maintaining the food’s quality attributes (flavor, color, texture,
nutritional value) to a reasonable extent and gives a shelf life of >2
years.
Who is more resistant to heat: spores or vegetative cells
Vegetative cells
For low acid foods, canning refers to
), canning processes specifically target
heat resistant spores of Clostridium botulinum
Where C.botulinum can grow and what dies it produce
C. botulinum is ubiquitous and capable of growing in the anaerobic
environment of canned food (hermetically sealed) and producing
botulinum toxin, a deadly neurotoxin that kills if ingested in
microgram quantities.
In high acid foods ( pH ≤ 4.6 ), spores of C. botulinum are incapable
of germinating (i.e., of being reactivated to the toxin producing
vegetative state).
What temperatures are required for low-acid foods to be commercial sterile
temperatures higher than the boiling
point of water are required to achieve commercial sterility (spores can
survive for > 5 hours at 100 C).
High temperatures required to inactivate spores are provided by
steam under pressure
What temperature can water vapour reach under pressure
10 psi = 116 C 15 psi = 121 C 20 psi = 127 C
Pasteurization: what temperature, target and the result of this treatment requires
Pasteurization is a less severe heat treatment, usually below the
boiling point of water
Pasteurization of milk targets vegetative cells of pathogenic
microorganisms such as Mycobacterium tuberculosis that are relatively
thermally resistant
Pasteurization results in a limited shelf life extension on its own as
some food spoilage organisms, particularly spores , survive the
process and are the source of new vegetative outgrowths.
Refrigeration is usually required to extend the benefits associated
with pasteurization.
What is blanching and when it is used
Blanching is a short heat process similar to pasteurization but its intent
is to denature (knock out) deleterious enzymes in fruits and
vegetables, such as:
polyphenol oxidase (enzyme responsible for enzymatic browning
lipoxygenases (produce off flavors by catalyzing lipid oxidation )
Blanching is commonly carried out prior to freezing, high pressure, or
other non thermal processes to minimize enzymatic deterioration
during processing and storage.
Thermal processing is a balance of ___
destruction of
microorganisms/enzymes and maintenance of product quality
attributes (flavor, nutritional value, color, texture, etc.).
Cardinal rule in thermal processing
Safety takes precedence over all else
Thermal processing is based on the following scientific approach:
understanding time/temperature combinations and their effects on
microorganisms of concern
understanding the heat penetration characteristics of a product
calculating appropriate thermal processes for the food product based on (1)
and (2)
validating the efficacy of thermal processes
What is done to check if the method kills C.botulinum
C. botulinum is too dangerous to use in step ( 4 ) so a less dangerous
but even more temperature resistant spore former is used instead,
such as:
Clostridium sporogenes PA 3679 (PA = putrefactive anaerobe), or
Bacillus stearothermophilus
Concept: If the spores of these organisms are adequately destroyed
by a thermal process, then we should also be safe from C. botulinum ,
which is thermally less resistant.
Sterility is achieved by holding a sample at ……
C for 15
minutes. (answer with a number)
121
In terms of cell number commercial sterility is
1 million ( 10 6 ) spores in a can, a thermal
process that results in the reduction of the spore population by 12
logarithmic cycles to 10 6 spores represents
Interpretation of 10 6 surviving spores:
Statistically, there is only one
living spore in 10 6 cans.