|MadSci Network: Botany|
Hi, 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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