Comparison of the New Aqueous Method with Other Methods
Table 4 compares the performance of the NAM established, with other
methods and the quality of oils obtained with that of the first class
oil required by Chinese National Standard. The OR obtained by NAM was
obviously better than that obtained by traditional enzyme-assisted
aqueous method (EAAM) extraction. Although NAM had a significantly lower
OEE (P < 0.05), it had a slightly higher OR without
significant difference (P > 0.05) as compared to SE. NAM
also had higher OR as compared with cold pressing (Scapinello et al.,
2017). Since no national standard for pecan oil acid value (AV; mgKOH/g)
or peroxide value (PV; mmol/kg) was found, it was compared to the
national standard of walnut oil (GB/T 22327-2008). As can be seen from
the table, the pecan oil extracted by the aqueous solution method met
the national standard of walnut oil. The peroxide value and acid value
of the product were better than that of first class walnut oil required
by the national standard. The oils were transparent, clean and colored
favorably.
The de-oiled pecan meal had 27.09% of water content when 1.40 mL water
was added for extracting oil. The de-oiled meal was also colored
favorably (L*=55.67, a*=7.64, b*=10.67), which should be able to be
applied to food recipes or the food industry.
Although the NAM used a quite low centrifugation force, a satisfactory
OR was achieved. This largely decreases the purchasing or operating cost
of centrifuge machine although the improvement of OR by a further
increasing in centrifugation force as comparing with 1435 g employed in
this study may not be ruled out. It should be noted that other methods
also need centrifugation or filtration to clarify oils.
The method of extracting oils from pecan kernels by NAM produces no
waste water. Drying the de-oiled meal only discharges vapor of water to
the air. Therefore, the NAM is more environmental friendly as compared
to EAAM (using large quantities of water previously published in
literature) and SE (releasing harmful solvent to the air).
The NAM produces the de-oiled pecan kernel meal with low water content
whose drying cost is greatly reduced. This is currently not achieved
when the EAAM using large amounts of water .
The NAM produces oil with high quality so that it is safe for
consumption without refinement (Table 4). The quality of oil produced by
the NAM is far better as comparing to the crude oil obtained by SE.
Although the established NAM had a slightly lower OER as compared to SE,
crude oils obtained by SE was not edible without refinement. A
significant amount of neutral oil can be lost during refining process
(Stalker and Wilson, 2015). Therefore, the NAM had significant higher OR
as compared with SE.