A Visual Method of Determining Maturity of Shelled Peanuts¹

To assess maturity distributions of shelled-stock peanut lots, a method was developed to characterize peanut kernels into one of three possible maturity classes based on testa texture and color and kernel shape. Kernels having testa with longitudinal wrinkles, a raisin-like texture, light color and slightly elongated shape were classed Immature and predominately were shelled from pods in the Hull-Scrape categories White, Yellow I, and early-Yellow II. Kernels with a smooth testa, pink to dark pink and with a more rounded appearance were classed Mid-mature and predominately were shelled from pods in the late-Yellow II, Orange, and early-Brown Hull-Scrape classes. Kernels with a waffle-like surface texture, dark pink to brown testa, and a more rounded appearance were classed as Mature, and predominately were shelled from pods in the mid-and late-Brown and the Black Hull-Scrape categories. Attempts to automate the system using color alone were unsuccessful; to be a reliable maturity sorting technique, both testa texture and color pattern had to be considered.