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United States Department of Agriculture

Agricultural Research Service

Title: Degradation of Almond Pellicle Color Coordinates at Different Storage Temperatures.

Authors
item Ledbetter, Craig
item Palmquist, Debra

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 2006
Publication Date: June 1, 2006
Citation: Ledbetter, C.A., Palmquist, D.E. 2006. Degradation of almond pellicle color coordinates at different storage temperatures. Postharvest Biology and Technology. 40(3):295-300.

Interpretive Summary: California’s annual 1 billion pound almond crop creates a problem with storage space during cracking and before the almonds are marketed. The optimal storage environment for almonds calls for cold and moderately humid conditions so that the almond kernels will retain quality for a 12 month period. Cold storage is not possible for the entire almond crop, and sub-optimal storage conditions lead to general product deterioration and kernel rancidity. We examined kernels of several almond varieties and advanced selections from an almond breeding program for their ability to withstand sub-optimal storage conditions during a simulated one-year storage period. We found that some types of almonds are much better suited to sub-optimal storage conditions and retain kernel quality better during long term storage. Since cold storage of almonds is expensive compared to storage at ambient environmental conditions, our results demonstrate that with the use of certain almond varieties, kernel quality can be retained in long term storage without using expensive cold storage facilities. The results also provide additional evaluation criteria for selection of parental almonds in the breeding program.

Technical Abstract: The pellicle or seed coat of almond kernels is subject to darkening during long term storage and may affect the marketability of the stored product. Environmental conditions during storage and genetic factors both affect the extent of darkening during the storage period. The degree of pellicle color change of five distinct almond accessions was examined during long term storage at 2 degrees C, 22 degees C and 32 degree C. Pellicle luminosity, chroma and hue were measured on 12 dates throughout an 11 month storage period. An ANCOVA was used, with storage temperature being a covariate, to examine the relative differences in luminosity, chroma and hue values during the storage progression. A comparison of weighted simple linear regression equations was used to distinguish between different rates of pellicle color coordinate degradation during the storage period. When averaged across the three storage temperatures, almond accession Padre consistently had significantly lower pellicle luminosity and chroma values throughout the storage period as compared with the other four almond accessions (p<0.05). While pellicle hue values of Padre were significantly lower than those of Nonpareil at the start of the test (p<0.05), Nonpareil’s pellicle hue values were significantly lower than those of Padre at the end of the storage period (p<0.05). Almond accession Nonpareil had the largest percentage decrease of the five almond accessions for pellicle luminosity (36.9 %) and hue (12.5 %). Regression analysis revealed significant differences in degradation rates of pellicle luminosity and chroma at all three storage temperatures (p<0.05), but significant differences in pellicle hue degradation were only evident at the lowest storage temperature (p<0.05).

Last Modified: 7/24/2014
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