The amount of oil recoverable as a function of postextraction
storage time for each method of stabilization was
determined and shown in Fig. 6(b). Unstabilized bran was
also used for extraction for comparison. Reduction in oil yield
was observed for all the stabilization methods. However, the
change in oil yield was significant for unstabilized bran and
solar dried bran. This is due to the fact that when the bran
was not stabilized or poorly stabilized FFA content increases
due to the lipase activation. FFA gets saponified at high pH (12)
used in aqueous extraction. Saponified FFA is water soluble
and will enter the aqueous phase. When the oil layer and the
water layer are separated by centrifugation FFA free oil layer is
obtained. Therefore, aqueous extracted oil is free from FFA or The above results were compared with previously published
data (Amarasinghe and Gangodavilage, 2004) for rice
bran oil extraction in Sri Lanka using hexane as the solvent
and presented in Table 3. Results are listed in two columns
for each stabilization method. The first column shows % of oil
extracted by aqueous extraction method (this work), whereas
the second column shows the FFA% in oil extracted using
hexane as the solvent (results extracted from Amarasinghe
and Gangodavilage, 2004). Variation of the FFA% for aqueous
extracted oil as a function of bran storage time was negligible
and not presented in the table. Further, Amarasinghe
and Gangodavilage (2004), have observed that the amount
of total oil (oil + FFA) extracted using hexane remains similar
for a given method for all storage times. Therefore, the
reduction in oil% observed in this work is comparable with
the increase in FFA (%) for hexane extracted oil reported by
Amarasinghe and Gangodavilage (2004). Therefore it can be
concluded that the decrease in the % of oil extracted by aqueous
extraction with the storage time is due to the FFA growth
in rice bran. This can be minimized by applying a suitable
method for stabilization of rice bran. Steaming is observed as
the most effective and applicable method of stabilization rice
bran.
The amount of oil recoverable as a function of postextractionstorage time for each method of stabilization wasdetermined and shown in Fig. 6(b). Unstabilized bran wasalso used for extraction for comparison. Reduction in oil yieldwas observed for all the stabilization methods. However, thechange in oil yield was significant for unstabilized bran andsolar dried bran. This is due to the fact that when the branwas not stabilized or poorly stabilized FFA content increasesdue to the lipase activation. FFA gets saponified at high pH (12)used in aqueous extraction. Saponified FFA is water solubleand will enter the aqueous phase. When the oil layer and thewater layer are separated by centrifugation FFA free oil layer isobtained. Therefore, aqueous extracted oil is free from FFA or The above results were compared with previously publisheddata (Amarasinghe and Gangodavilage, 2004) for ricebran oil extraction in Sri Lanka using hexane as the solventand presented in Table 3. Results are listed in two columnsfor each stabilization method. The first column shows % of oilextracted by aqueous extraction method (this work), whereasthe second column shows the FFA% in oil extracted usinghexane as the solvent (results extracted from Amarasingheand Gangodavilage, 2004). Variation of the FFA% for aqueousextracted oil as a function of bran storage time was negligibleand not presented in the table. Further, Amarasingheand Gangodavilage (2004), have observed that the amount
of total oil (oil + FFA) extracted using hexane remains similar
for a given method for all storage times. Therefore, the
reduction in oil% observed in this work is comparable with
the increase in FFA (%) for hexane extracted oil reported by
Amarasinghe and Gangodavilage (2004). Therefore it can be
concluded that the decrease in the % of oil extracted by aqueous
extraction with the storage time is due to the FFA growth
in rice bran. This can be minimized by applying a suitable
method for stabilization of rice bran. Steaming is observed as
the most effective and applicable method of stabilization rice
bran.
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