2.3.2 Carbohydrates
Carbohydrates constitute relatively small portion of canola seed and are mainly
present in hull and cotyledons. As discussed above, carbohydrates range 14–15%
(on dry basis) in canola seed. Low-molecular-weight carbohydrates such as sugars
(glucose, fructose, and sucrose), stachyose, raffinose, etc. are majorly present in
cotyledons; while high-molecular-weight carbohydrates such as cellulose, hemicellulose, and pectin are majorly present in hulls.
Carbohydrates and its fractions in canola/rapeseed have been comprehensively
studied and reviewed by Siddiqui and Wood (1972, 1974, 1977) and Shahidi (1990).
It is reported that dehulled and oil-free canola meal contained approximately 52%
proteins and 48% carbohydrates (Siddiqui and Wood 1977). There are several
glycosides of sugars particularly raffinose and stachyose, present in hull of the
seed, which cause the flatulence in human and animals. Due to presence of high
amount of hull and indigestible carbohydrates, canola meal is limited to be used as
animal feed. However, removing of hull by processing techniques could improve the
nutritional value of canola meal for human use.
2.3.3 Proteins
Like other members of the Brassica genus, whole canola seed contains approximately 17–26% proteins. However, de-oiled canola meal contains up to 50% protein
content (on dry basis). Canola protein consists of majorly storage proteins, namely,
cruciferin and napin, which constitute approximately 60% and 20% of the total
proteins, respectively (Ghodsvali et al. 2005). Another canola protein is oleosin,
which is a structural protein associated with oil bodies in the seed (Wu and Muir
2008). There are several studies indicating the superior quality and well-balanced
amino acid profile of canola protein as compared to other oilseeds’ protein such as
soybean, sunflower, safflower, etc. (Sosulski and Sarwar 1973; Ohlson and Anjou
1979; Ghodsvali et al. 2005; Yoshie-Stark et al. 2006; Wanasundara et al. 2016). In
terms of essential amino acids, canola protein has a very high amount of sulfurcontaining amino acids, i.e., lysine, cysteine, and methionine (3.0–4.0% of total
protein), which is closer to FAO requirements for humans than any other quality
vegetable protein available (Ohlson and Anjou 1979; FAO/WHO/UNU 1985).
Canola protein has high content of essential amino acids (>400 mg/g protein),
particularly sulfur-containing amino acids (>40–49 mg/g protein) (Grala et al.
1997). Earlier, Sosulski and Sarwar (1973) evaluated amino acid profile of various
oilseed meals and protein isolates and concluded that canola (rapeseed) and soybean
contained high proportions of essential amino acids, while sunflower, safflower, and
flaxseed contained high amount of nonessential amino acids. The protein scores
were found to be higher for rapeseed meal (70) and flax meal (82) than that of casein
(57), soybean (67), sunflower (63), and safflower (63) meal (Sosulski and Sarwar
52
A. Goyal et al.
Carbohydrates constitute relatively small portion of canola seed and are mainly
present in hull and cotyledons. As discussed above, carbohydrates range 14–15%
(on dry basis) in canola seed. Low-molecular-weight carbohydrates such as sugars
(glucose, fructose, and sucrose), stachyose, raffinose, etc. are majorly present in
cotyledons; while high-molecular-weight carbohydrates such as cellulose, hemicellulose, and pectin are majorly present in hulls.
Carbohydrates and its fractions in canola/rapeseed have been comprehensively
studied and reviewed by Siddiqui and Wood (1972, 1974, 1977) and Shahidi (1990).
It is reported that dehulled and oil-free canola meal contained approximately 52%
proteins and 48% carbohydrates (Siddiqui and Wood 1977). There are several
glycosides of sugars particularly raffinose and stachyose, present in hull of the
seed, which cause the flatulence in human and animals. Due to presence of high
amount of hull and indigestible carbohydrates, canola meal is limited to be used as
animal feed. However, removing of hull by processing techniques could improve the
nutritional value of canola meal for human use.
2.3.3 Proteins
Like other members of the Brassica genus, whole canola seed contains approximately 17–26% proteins. However, de-oiled canola meal contains up to 50% protein
content (on dry basis). Canola protein consists of majorly storage proteins, namely,
cruciferin and napin, which constitute approximately 60% and 20% of the total
proteins, respectively (Ghodsvali et al. 2005). Another canola protein is oleosin,
which is a structural protein associated with oil bodies in the seed (Wu and Muir
2008). There are several studies indicating the superior quality and well-balanced
amino acid profile of canola protein as compared to other oilseeds’ protein such as
soybean, sunflower, safflower, etc. (Sosulski and Sarwar 1973; Ohlson and Anjou
1979; Ghodsvali et al. 2005; Yoshie-Stark et al. 2006; Wanasundara et al. 2016). In
terms of essential amino acids, canola protein has a very high amount of sulfurcontaining amino acids, i.e., lysine, cysteine, and methionine (3.0–4.0% of total
protein), which is closer to FAO requirements for humans than any other quality
vegetable protein available (Ohlson and Anjou 1979; FAO/WHO/UNU 1985).
Canola protein has high content of essential amino acids (>400 mg/g protein),
particularly sulfur-containing amino acids (>40–49 mg/g protein) (Grala et al.
1997). Earlier, Sosulski and Sarwar (1973) evaluated amino acid profile of various
oilseed meals and protein isolates and concluded that canola (rapeseed) and soybean
contained high proportions of essential amino acids, while sunflower, safflower, and
flaxseed contained high amount of nonessential amino acids. The protein scores
were found to be higher for rapeseed meal (70) and flax meal (82) than that of casein
(57), soybean (67), sunflower (63), and safflower (63) meal (Sosulski and Sarwar
52
A. Goyal et al.