Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 1998
Publication Date: N/A
Interpretive Summary: An instrumental technique for classifying peanuts based on their physiological maturity is described. The method is an extension of the hull scrape method of Williams and Drexler, where the outer layer of the hull is removed and the maturity of the peanut is visually determined based upon the color of the exposed middle layer of the peanut hull. The technique is based on the use of reflected visible light for determining maturity. The instrumental process is objective and has the potential to be automated. This process would aid in assessing crop quality and setting the economic value of a given peanut lot.
Technical Abstract: Peanut maturity has previously been correlated with the color of the mesocarp of the peanut hull going from light to dark as the peanut matures. The color of the mesocarp of freshly harvested peanuts was determined using a Hunter colorimeter. Hunter L*, a*, and b* values on individual peanuts, representative of each class, with wet and dry hulls were reproducibly determined with standard deviations of less than 0.8%. Peanuts were sorted into maturity classes of yellow, orange A, orange B, brown and black based on the hull scrape method of Williams and Drexler. The Hunter L*, a*, and b* values were then measured on the dry pods for each class. Yellow peanut pods had a median Hunter L* value of 70.0, while mature black peanut pods had a median Hunter L* value of 51.7 and median values for orange A, orange B and brown pods were 68.0, 63.7, 57.0, respectively. A similar inverse relationship was observed for the Hunter b* value and maturity, while the Hunter a* value reached a maximum at orange A. No correlation was observed between the peanut maturity and Hunter L*, a*, and b* values acquired with the exocarp intact.