Page 396 - Biosystems Engineering

Extraction, Refining, and Stabilization of Edible Oils 373

Supercritical Fluid Extraction An alternative technique to the organic
solvent–based extraction methods is supercritical fluid extraction
(SFE). Extraction with a solvent at temperatures and pressure above
its critical point is known as supercritical fluid extraction with carbon
dioxide as the extraction solvent. This has been tried as an alternative
deacidification process for high free fatty acid (FFA) containing oils.
The efficiency of this technique for extracting oil from a variety of
seeds has been demonstrated by different investigators. 2,3
However, the emphasis of these prior researches has been to
develop an alternative option for large-scale processing of oil seeds,
rather than to use SFE as an alternative analytical technique to deter-
6
mine oil content in seeds. King et al. performed the SFE experiment
in the following way.
In this experiment, 10,000 psig (680 bar) at 80°C was applied to the
soybeans seeds in a 316 stainless steel extraction cell measuring 6 in in
length with an internal diameter of 5.8 in. The flow rate and the
amount of CO used in each extraction were measured with a dry
2
test meter under ambient conditions. The flow rate was maintained at
5 L/min, and the amount of CO ranged from 200 to 600 L (expanded
2
volume) until no further oil was extracted. The collected oil was trans-
ferred to 250-mL round-bottom flasks. After SFE, the oil was subjected
to rotary evaporation for 75 min at 50°C to remove any residual CO
2
6
or water from collected oil. King et al. also found that results obtained
with SFE were in excellent agreement with those obtained by a con-
ventional soxhlet technique with organic solvent.
Rao has shown the percentage contents of oil and protein in the
7
seeds of Brachychiton rupestris, Brachychiton australis, Brachychiton acu-
minatus, and Brachychiton gregori were 28.7, 29.6, 32.5, and 29.8 percent
and 23.6, 23.5, 22.0, and 22.0 percent, respectively. The major fatty
acid was oleic acid in B. acuminatus and linoleic acid in the other three
seed oils. Cyclopropane fatty acids, malvalic and sterculic, were pres-
ent in appreciable concentrations (6.6 to 10.6 percent and 0.5 to 2.2
percent, respectively). Cyclopropane fatty acids were identified and
estimated using a combination of spectroscopic, chemical, and chro-
matographic analyses.
Pearl millet (Pennisetum typhodeum L.) grain is widely cultivated
and consumed throughout the world and is rated as the world’s sixth
most important crop. It can be grown in regions with comparatively
low rainfall (arid zone) and can also withstand the vagaries of nature
8
to a great extent. Nag et al. have discussed the processing oil from
pearl millet. Studies revealed that each layer of the grain contains oil.
Bran with 16 percent pearling contains about one-third of the total oil
available in the kernel. The oil cake is rich in protein and can be con-
verted to useful feed or fodder.
1
Nag et al. observed that Terminalia belerica Roxb (Combretaceae),
known as bahera, is found abundant in tropical Asia, is a source of
new edible oil (37 percent by dry weight of kernel), biofertilizer,