| Summary: | The presence of mucilaginous material in the seed coat of
canola cv. Candle has been associated with
storage and mold infestation problems. This study examined
the yield of mucilage from canola cv. Candle and some of
its chemical and physical properties.
Canola seeds were extracted for 16 hours with
water using a seed:water ratio of 1:18 or heat-treated
prior to water extraction using a seed:water ratio of 1:7.
The mucilage was precipitated with 4 volumes of 95%
ethanol and recovered by centrifugation at 3500 x g and
23 C for 10 minutes. A twofold increase in the yield of
mucilage (1.33%) was obtained for the heat-treated seeds
compared to (0.69-0.72%) for the unheated canola seeds.
The heat-treated canola seeds were subjected to
different extraction times from 4 to 16 hours using a
seed:water ratio of 1:7. Approximately 63.8% of the total
extractable rnucilage was obtained after the first 4 hours.
No significant differences (P<0.05) were observed in the
yield of mucilage between 4 hour extraction intervals. A
significant difference (P<0.05) however, was evident in
the yield of mucilage between 8 and 12 hour extraction
intervals. The total yield of mucilage obtained at the end
of the 16 hour extraction period was 1.16%
Proximate analysis of canola mucilage showed it
contained moisture (8.2%), protein (18.2%), carbohydrate
(30.6%), ash (29.4%) with the remainder (13.6%)
unidentified. No significant differences (P<0.05) were
observed in either the protein or carbohydrate content of
mucilage throughout the 16 hour extraction period. This
suggested the mucilage was homogeneous with respect to
protein and carbohydrate content.
Analysis of the carbohydrate composition by gas
chromatography showed that with the exception of
rhamnose, no significant (P<0.05) differences between the
individual monosaccharides over the different extraction
intervals. The monosaccharide composition of canola
mucilage was galactose (31.7%) rarabinose (28.9%),
glucose (14.9%), mannose (9.7%), rhamnose (4.5%), xylose
(3.7%) with the remaining 7.1% unidentified .
Purification of mucilage was accompanied by a two and
threefold increase in rhamnose and unidentified fractions
respectively. A marked decrease in the other
monosaccharides was observed for the purified material.
The flow curve of a 0.5% solution of canola
mucilage exhibited a shear thickening property. Canola
mucilage was non-Newtonian in behaviour up to a shear rate
corresponding to 350 rpm while at higher rate of shear it
was Newtonian. The viscosity of a 0.5% solution of canola
mucilage within the Newtonian range was 4 cp. Canola
mucilage reduced surface tension and interfacial tension
of a corn oil:water system . The interfacial tension value
using canola mucilage was 9.5 dynes/crn which was similar
to mustard mucilage (8.5 dynes/cm). The ability of canola
mucilage to reduce interfacial tension was responsible for
the formation of a stable salad dressing incorporating
canola mucilage as emulsifier.
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