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ARS Home » Research » Publications at this Location » Publication #60675
Title: FOURIER TRANSFORM INFRARED SPECTROSCOPY OF ZUCCHINI SQUASH STORED AT LOW TEMPERATURES

Author
item Buta, Joseph - George
item QI, LING - TIANJIN ACADEMY, CHINA
item Wang, Chien

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Many fruits and vegetables develop damage symptoms when stored at low temperatures after harvest or during transport to market. Understanding the complex biochemical changes in the commodities that resulted in the appearance of damage after chilling has been difficult. Methods of alleviation of chilling injury can be developed as a result of having a better understanding of the cellular changes that occur during chilling. We have used Fourier Transform infrared spectroscopy to monitor the changes in the types of protein structures found in the pericarp tissue of zucchini squash stored at either chilling temperatures or low but nonchilling temperatures. If the squash were stored at low but nonchilling temperatures, cellular protein structures were changed as an adjustment to the low temperature in just 2 days. Return of the nonchilled squash to room temperature caused adjustment of the protein structures to resemble the original ones. However if the squash were stored at chilling temperatures for only 2 days, no changes in protein structure occurred indicating that the ability to adjust to chilling had been destroyed. These findings demonstrate the importance of proper storage temperature for fruits and vegetables to allow adjustment of the plant tissue to new conditions and to prevent irreversible onset of cellular damage before symptoms become visible.

Technical Abstract: Fourier Transform infrared spectroscopy (FTIR) was used to investigate spectral changes in pericarp tissue of zucchini squash tissue resulting from low temperature storage - chilling (5 degrees C) or nonchilling (15 degrees C). The Amide I spectral region (1660-1620 cm-1) was the only region showing temperature-related patterns of change when frozen tissue samples dispersed in potassium bromide were studied. These spectral changes were attributed to major changes in protein conformation resulting from the differences in temperature during storage. The absorption bands assignable to protein conformation in the pericarp tissue from freshly-harvested squash indicated the presence of a-helix forms. Storage at 15 degrees C resulted in spectral shifts resulting in the presence of multiple a-helix and B sheet protein forms. No shifts were found in the spectra of tissue from squash stored at the chilling temperature, (5 degrees C). If squash stored at 15 degrees C were then warmed to room temperature, spectral shifts occurred such that only absorption bands were found for the a-helix forms of protein in the pericarp tissue. No spectral shifts were found for the protein absorption bands of tissue from squash stored at 5 degrees C and then warmed to room temperature. Spectral shifts of protein absorption bands of tissue from temperature preconditioned squash stored at 15 degrees C prior to storage at 5 degrees C indicated transition from multiple a-helix and B sheet forms to a-helix forms occurred related to the length of time in 5 degrees C storage.