Za odpiranje dokumenta
kliknite tukaj …
Polymeric compounds are found in all foods, either as natural
constituents or as additives to improve taste, texture or appearance.
Other polymers are used extensively in food processing and packaging.
Food analysts are also concerned with compounds that should not
be found in foods, such as pesticides and adulterants, and with
the breakdown of foods as they are used in other processes. The
composition of frying fat is a case in point.
One of the largest uses of polymers is in packaging. Polyolefins such
as polyethylene are employed to make films and molded containers.
Properties such as mechanical strength and toughness are vital in
such end-use applications.
Gel permeation chromatography (GPC) is a versatile and valuable
technique for all types of food analysis. What’s more, although
most GPC food analysis is carried out using water eluents, organic
methods are also useful for more complex compounds, such as
starch polysaccharides, and packaging polymers like polypropylene
that are derived from crude oil. The purity of frying fats can also be
assessed by GPC in organic eluents.
Pesticide levels must be closely monitored to ensure food is safe to
eat. GPC can be used to separate and isolate individual components
of a sample based on size exclusion, and can isolate toxic pesticides
from contaminated food oils. By scaling up these analytical
separations to preparative GPC, it is possible to isolate pesticide
residues in sufficient quantity for further analysis or identification.
Many GPC food analyses benefit from the use of triple detection,
because it combines concentration, viscometry, and light scattering
detectors to assess the molecular weight distribution and molecular
structure of polymers, without having to rely on column calibrations.
This can be important when analyzing complex food polymers for
which no structurally similar standards are available.
This compendium draws together many GPC techniques for the
broader analysis of foods, including investigations of raw food
materials, food additives, breakdown products, pesticide residues,
and characterization of polymers used for food packaging. The
versatility of gel permeation chromatography is ably demonstrated
in food analysis.