Effect of Time and Temperature of Baking on Oil Recovery
The effect of time of baking on OR is shown in Fig. 2. The OR was only
77% without baking. It gradually increased as the baking time was
increased from 0.0 to 8 minutes. However, it dramatically decreased when
the baking time was further increased to 10 minutes. Among the baking
time studied, baking for 8 minutes was the most suitable for recovering
oil from the pecan kernel slurry. Therefore, proper baking time will
increase the OR though baking for too long adversely affected the OR.
The effect of temperature of baking on OR is also shown in Fig. 2. The
OR was only 77% without baking. It gradually increased as the baking
temperature was increased from 24 to 95 ℃. However, it decreased when
the baking temperature was further increased to 120 ℃. Among all the
baking temperature investigated, baking at 95 ℃ resulted in the highest
OR.
Baking the pecan kernels ahead of grinding is necessary for deactivating
lipase and removing water. Lipase deactivation is able to prevent
neutral oils from hydrolysis during grinding and extraction by water.
Undesirable losses of neutral oil can be reduced if its hydrolysis is
prevented so that di- or mono-glycerides, glycerols and free fatty acids
formation can be decreased. This step may also be important for avoiding
emulsion during aqueous extraction or grinding. This should also be a
critical factor of obtaining the best OR. Furthermore, proper baking may
facilitate the disruption of cell wall by grinding. However, increases
in baking time or temperature might elevate the extent of protein
denaturation, which might decrease OR because of an increase in oil
absorption.