Table 1. Fracture forces of different seed coats, nut shells and hard inner drupe shells (endocarp, “fruit stone”); all specimens were tested in compression in the as-received state without additional drying with a cross-head speed of 5 mm/min.

species	shell moisturecontent (wt%)	n	Diameter(mm)	length(mm)	mean shellthickness t (mm)	fracture forceF frac (N)	maximum fractureforce F frac, max (N)	Ffrac/t (N/mm)
peanut	2.0±0.5	10	15.9±0.9	47.9±1.9	1.2	76±20	117	63±17
pecan	5.5±0.9	10	23.3±1.1	44.7±3.5	1.2	323±114	433	269±95
walnut	5.1±0.3	10	28.2±0.5	35.9±1.8	1.6	378±165	72	236±103
hazelnut	5.5±0.1	10	21.7±0.3	23.4±1.3	1.5	431±127	729	288±85
almond	4.9±0.1	10	21.0±1.3	35.2±1.7	3.2	895±181	1221	280±57
Macadamia seed	10.1±0.7	34	23.7±1.3	23.8±1.3	2.3	2364±645	3926	1016±179

They were oriented with their sutures vertical to the loading direction and their shorter dimension parallel to the loading direction ( fig. 1 ). “n” denotes the number of specimens tested. All values are mean values plus/minus standard deviations, if not denoted otherwise.