I have summarized the contents of the feedback lecture, lecture notes and knowledge clips of module 5 into this document. This will help you prepare for the exam! Good luck studying.
Enzymes may both have negative and positive effects on food quality.
Amylase:
Enzyme that hydrolyzes/synthesizes carbohydrates, depending on the conditions.
o In bread, amylase breaks down starch to provide food to the yeast
successful fermentation, loaf volume & softness.
Proteases:
Enzymes that hydrolyze proteins into peptides. This results in improved digestibility.
o Protein hydrolysates are used in sports drink.
o Enzyme activity of proteases must be controlled extensive hydrolysis
makes the products unpleasant for the consumer (bitter taste).
Lipases:
Enzymes that hydrolyze oils = lipid oxidation.
o Occurs in nuts and oils.
o Activity must be controlled to minimize rancidity.
Trans-glutaminase:
Enzyme that is used in meat protein crosslinking.
Enzymes can affect different properties of food:
o Texture.
Formation of cheese from milk (+).
Wilting of vegetables (-).
o Taste.
Oil soapy taste (-).
o Color.
Fruit browning (-).
For the before-mentioned proteins, it is important to describe the kinetics, to control
the reactions!
Both temperature and pH influence enzymatic reactions.
In foods, enzymes and substrates are often stored in different compartments they
cannot react. However, upon cutting, the structure is altered cells break down
enzymes get in contact with substrate.
Enzyme activity is often undesired. Enzyme activity may be suppressed in various
ways:
Without treatment:
o Products with a low/high pH.
o Products that are stored at a low temperature.
o Products with low-intermediate water activity.
With treatment:
o Heat treatment for a short time (traditional method).
, o Ultra High Pressure (UHP) or Pulsed Electric Field (PEF) (alternative
methods).
Treatment does not only affect enzymes, but also bacteria and spores. Depending on
the most heat-sensitive organism, a heat treatment will be selected.
o However, there is a limit, as the structure of food cannot be affected too much
temperature and duration should be balanced properly.
Currently, enzymes are considered very mild tools for the food industry:
o They may be used to produce food components (e.g., prebiotics).
o They may be used to improve food products’ properties.
o Green chemistry.
Some reactions are convenient to use, as they are highly
selective in terms of substrate not many side reactions
reaction is performed efficiently (= green chemistry).
Temperature can be used as a tool to control enzyme activity.
o Low temperature reactions proceed slowly.
o High temperature faster reaction, but also inactivation of enzymes.
Generally, the Arrhenius equation is used to describe the effect of temperature on
enzyme activity. However, keep in mind that the exact behavior depends on the
specific reaction mechanism.
o The Arrhenius equation should thus be used with caution!
o Enzyme heating inactivation can be treated as microbial inactivation.
Upon applying a certain high temperature,
the reaction will proceed fast at the start.
However, as time proceeds, the situation
reverses the extent of the reaction is
stabilized at higher temperatures (i.e., the
enzyme is inactivated faster than that the
product is formed).
o Inactivation kinetics thus needs to
be desribed at increasing
temperatures.
The reaction rate strongly varies with time and temperature. It is thus important to
specify the exact conditions when referring to enzyme activity.
o To determine the enzymatic reaction rates, the initial slopes must be straight.
This is the case <10% conversion.
o When using higher conversions, a non-liner
approach is advisable.
At high values of water activity (aw), the reaction rate is
very high reaction rate depends on the hydration state
of the enzyme, which requires water molecules to react.
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