| Liquid
sweeteners such as sucrose and high-fructose
corn syrup are commonly used as ingredients in many foods
especially in beverages. Sucrose is extracted and
purified from cane and beets. High-fructose corn
syrup is derived from the enzymatic and acid hydrolysis
of corn starch. Other
sweeteners are maple syrup, honey, and molasses.
 The
low water activity of starches and dry sweeteners is largely
responsible for their microbial stability. However, liquid
sweeteners may spoil due to their higher water content. Industrial
prepared syrups range from 42 to 86ºBrix.
Microorganisms in starches and
sweeteners come from the raw source materials or from the manufacturing
environment. Organisms that are likely to survive the
process are sporeforming mesophilic aerobic and anaerobic bacteria
such as Bacillus sp. and Clostridium sp. Other
mesophilic bcteria may be present but will not grow in these
products. Osmotolerant yeasts present the greater risk
for spoilage. Molds can also be present. In our
experience, heat-resistant mold spores (ascospores) can be
present in liquid sucrose and high fructose corn syrup and
can contribute to the spoilage of beverages where these sweeteners
are used.
Microbial spoilage of liquid sweeteners
may be prevented by destruction of contaminating microorganisms,
use of sanitizing agents on processing and storage equipment,
and prevention of water vapor condensation in storage vessels. To
prevent condensation, filtered air treated by ultraviolet irradiation
is forced over the surface of the liquid. Prompt use
of the sweeteners also helps to reduce the incidence of spoilage.
With the exception of honey, commercially
produced sweeteners are not involved in outbreaks of foodborne
illnesses. Honey has been implicated as the source of
spores of Clostridium botulinum causing infant botulism. The
sporeforming pathogen Bacillus cereus may be present
in starches used as ingredients in food such as puddings and
sauces. Foodborne illness could then result from consumption
of such temperature-abused foods.
Recommended tests:
Aerobic Plate Count
Osmophilic/Xelotolerant yeasts and molds
Aerobic sporeformers
Anaerobic sporeformers
Additional tests:
Heat-resistant mold spores.
Bacillus cereus.
Clostridium botulinum spores (in honey).
Adapted from:
Smittle, R. B. and Erickson, J.
P. 2001. Sweeteners and Starches, p. 545. In
F. P. Downes and K. Ito (eds.), Compendium of Methods for the
Microbiological Examination of Foods. American Public
Health Association, Washington, DC.
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