Analysis of the physical and mechanical properties of the pine nut as criteria in the design of a pine nut shelter

Abstract

Among the hundred species of pines, a third are classified as soft pines, Largely on the basis of wood and leaf anatomy. Eleven species of soft pine make up the group known variously as the pinon, pinyon, or North American nut pines. Pinus cembroides Zucc belongs to this category and is the species used in this study. The seeds of this species form an important part in the diet for humans. Most pine seeds are presently shelled by hand. Mechanical. shelling has been attempted, but the shelters damage the nuts and reduce value of the product. Improved mechanical shelling techniques are needed to provide a quality product at reasonable prices. The overall goal of this work was to develop information to establish design criteria for applying engineering principles for shelling pine nuts. The scope of the work included measurement of physical and mechanical properties of pine nuts and evaluation of one engineering principle for rupturing the seed shell. Based on the study of the physical and mechanical properties, design criteria for applying engineering principles for shelling pine nuts were developed. These summarized criteria are: 1) cracking unsoaked seeds with about 8.9% moisture content enhances shattering of shells at rupture, 2) deformations ranging from 0.82 mm to 1. 14 mm is required to fracture seeds of different sizes, 3) void spaces differ according to seed size allowing deformation of shell without contacting the nut, grouping seeds in size classifications is needed to minimize nut damage, 4) compression forces to crack seeds of different size range from 159.76 N to 304.69 N, 5) a continuous feed process to crack seeds is needed to obtain adequate shelling, and 6) pine nut shells ruptured and shattered at low loading rates, so impact loading is not necessary for the shelling process. The engineering principles for cracking nuts were analyzed and a mechanical shelling device using counter rotating rollers for cracking nuts was constructed and tested. Results of the tests showed that the counter rotating roller principle can adequately crack 70% in a continuous shelling method for shelling pine nuts.