Estructura del cotiledón de la semilla de almendra (Prunus amygdalus L.) cruda,remoj ada y tostada / Cotyledon structure of raw,soaked and roasted almond (Prunus amygdalus L.)

The microstructure of the sweet almond (variety Marcona) and the most important microstruc tural changes caused after roasting (150 °C, 45 min) and soaking (H₂O and NaCl 5%, 24 h) were studied by scanning electron microscopy (SEM). The majority of the cotyledon tissue is made up of rather large, nearly isodiametric parenchyma cells with a thick cell wall; the cell-to-cell junc tions are characterized by a distinct middle lamella. The cytoplasmatic membrane delimits the cellular content, protein bodies and lipid bodies being the major components. A cytoplasmic network consisting of the membranous system structured as hexagonal cells extends throughout each parenchyma cell, and surrounds the major components. The parenchymatic tissue is surrounded by a layer of epidermic cells and tegument. After roasting, the cellular organization is lost and the cytoplasmic network surrounding the lipid bodies and protein bodies is altered; the heat destroys some middle lamellae of cell-to-cell junctions; the cytoplasmic compartimental ization of the oil is lost in most cells and the oil drops coalesce; protein bodies are distended and aggregated; other thermal modifications of roasting included pitting and pock-marking of the epidermis and protein bodies, caused by the escape of steam and oil. Soaking in water did not cause drastic changes in the structure; the most significant modification was an alteration of the cytoplasmic network and membrane; soaking in 5% NaCl also produced a partial disolution of protein bodies.