MadSci Network: Botany

Re: how does the UV light or vacuum makes the fruits last longer and why?

Date: Tue Apr 6 14:01:16 2004
Posted By: Alfred Bushway, Professor of Food Science
Area of science: Botany
ID: 1081061571.Bt


I can answer your questions as to how UV or a vacuum make fruits last
longer, but won't be able to design a lab for you. You should work with
your science teacher using the following information to design a lab
experiment.Fruit spoilage is caused by two major factors. One being caused
by micororganism on the surface or inside (they may enter through breaks in
the skin, through the calyx on washing, etc.) of the fruit. The second
cause are naturally occuring enzymes in the fruit that lead to softening
and quality loss. UV and a vacuum work by different mechanisms. 

UV light is a bactericicdal agent particularly UV light at a wavelength of
about 2,600 Angstroms. The UV light is absorbed by proteins and nucelic
acids, in which photochemical changes occur that can lead to cell death. In
bacteria the UV light acts on the nucleic acids causing lethal mutations.
Because of UV lights limited penetrating power, it is most affective in
killing microorganisms on the surface of the fruit.

By putting fruit in a vacuum, you have removed one of the catalysts
necesary for many enzymatic reactions, oxygen. Without oxygen many of the
naturally occuring enzymes in the fruit are inhibited. In addition, many of
the spoilage bacteria associated with food are aerobes. This means that
they must have oxygen to be able to multiply. 

Thus, although UV and vacuum operate by different mechanisms they both
could be used to extend the shelflife of fruit.

Al Bushway
Professor of Food Sciecne

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