1.1 Oil Rapeseed summary

1.1.1 Definition of rapeseed

Rapeseed is a kind of small spherical seeds with black, yellow, brown and red seed coats, which are cultivated by cruciferous herbs.

1.1.2 Morphology of rape and rapeseed

Rape belongs to the cruciferous family, and is an annual or perennial herb. The general plant height is about 30-90 cm, and the height of some varieties can reach 150 cm. The stem is cylindrical, strong and multi branched; The leaves are alternate, and the basal leaves are long elliptic or spoon shaped, while the stem leaves are lanceolate or long triangular, with bristles and wax layers on the leaves. The raceme has yellow or light yellow petals, which intersect in a cross shape.

There are many long horned fruits on the stem of rape. There are spherical, nearly spherical or ovoid seeds, that is, rapeseed. Each horned fruit generally has 10-20 seeds, and more than 30 seeds. The seeds are planted on the edge of the diaphragm, divided into left and right rows. The diameter of rapeseed is about 1.5 mm, and there are yellow, brown and black seeds.

1.1.3 Types of rape and rapeseed

According to the type of rape, rapeseed can be divided into three types: mustard type, cabbage type and cabbage type. Brassica juncea is also called high rape, bitter rape, hot rape or large rape. The seeds of mustard type rapeseed are small, the seed coat is mostly yellow or brownish red, with a strong spicy taste, and the oil content is about 30%,

The oil tastes bad.

Brassica napus is also called short rape, sweet rape and small rape. The seed size of Chinese cabbage type rapeseed is different. The seed coat is mostly brownish red, brown or black, and the oil content is 35-45%. Brassica napus, also known as Shengli rape, has the largest planting area in China at present. Brassica oleracea has high yield, large seeds, mostly dark brown seed coat and 40-45% oil content.

1.1.4 Structure of rapeseed

Rapeseed consists of seed coat and embryo, and endosperm has degenerated. The seed coat of rapeseed is very thin. If you look carefully, you can see the umbilicus on the seed coat. Different types of rapeseed have different seed coat colors. The maturity of rapeseed is related to the color of seed coat. The color of mature rapeseed seed coat is darker, while the color of non fully mature rapeseed seed coat is lighter. The embryo is the main component of rapeseed. There are two developed cotyledons in the embryo. The oil and protein of rapeseed mainly exist in the cotyledons. The endosperm vestiges can be seen outside the cotyledons.

1.2 Composition of rapeseed

1.2.1 Chemical composition of rapeseed

Rapeseed is mainly composed of oil, protein, sugar, water, ash (minerals), etc. The content of each component varies greatly due to different varieties, growth environment conditions and agricultural technical measures. The following table shows the main chemical components of rapeseed.

Table 1-1 Chemical Composition of Rapeseed (% on dry basis)

Component content

Grease 37-48 Ash 3-8

Protein 19-31 phospholipid 1-1.5

Carbohydrates 17-39 Moisture 6-10

Coarse fiber 5-11

1.2.2 Nutrients in rapeseed

1. Grease

Oil is the main nutritional component in rapeseed, Rapeseed oil It is generally dark yellow or brown. Erucic acid is the characteristic fatty acid in rapeseed oil. Because it is generally believed that high erucic acid is harmful to human body, breeding experts at home and abroad have been cultivating low erucic acid rapeseed oil in recent years. The low erucic acid rapeseed oil contains not only erucic acid, but also oleic acid, linoleic acid and linolenic acid. In addition, it also contains some palmitic acid, eicosenoic acid and tetracosanic acid. From the perspective of nutritional value, the human body can digest and absorb rapeseed oil up to 99%, and it has cholagogic function. When the liver is in a pathological state, rapeseed oil can also be metabolized by the human body.

2. Protein

Protein is also the main nutritional component of rapeseed. The amino acid composition of rapeseed protein is relatively balanced, and there is almost no restrictive amino acid. Rapeseed protein titer is 3-5, ratio soybean The protein is still high. Compared with other oilseed meal, rapeseed meal has the highest content of sulfur-containing amino acids, followed by methionine and lysine.

3. Carbohydrates

Rapeseed contains a lot of compounds, which can be used as a source of energy. However, due to the high content of crude fiber, its effective energy value is relatively low.

4. Minerals

Rapeseed contains a variety of minerals, especially high content of calcium, phosphorus, selenium and manganese, and high content of iron and zinc, but 60-70% of phosphorus content belongs to phytate phosphorus, and the utilization rate is relatively low.

5. Vitamins

Rapeseed contains many vitamins, especially nicotinic acid, choline, folic acid, riboflavin and thiamine.

1.2.3 Anti nutritional factors of rapeseed and their harm

The main anti nutritional factor in rapeseed is glucosinolate. In addition, it also contains phytic acid, tannin, sinapine, saponin and other anti nutritional factors. Most of these harmful ingredients are left in rapeseed meal during rapeseed processing.

Common rapeseed contains high glucosinolates, commonly known as glucosinolates, which are complex alkyl thioglycols with more than 70 organic ligands, and various glucosinolates exist in the form of mixtures. Mustard glucoside is soluble in water and has no toxicity. However, under wet and hot conditions, due to the action of natural mustard enzyme in rapeseed, it hydrolyzes nitrile, oxazolidinethione, isothiocyanate and thiocyanate. These sulfur compounds are toxic and have unpleasant odor. During the preparation of rapeseed oil, most of them remain in the cake, and some will enter into the crude rapeseed oil, thus affecting the use value of rapeseed cake and the quality of rapeseed oil. In the past 10 years, China has vigorously promoted the breeding and planting of "double low" rapeseed (low erucic acid, low glucosinolate), and the planting area of double low rapeseed has been expanding. At present, the planting area of double low rapeseed in China has exceeded 80%. With the widespread planting of "double low" rapeseed, the quality of rapeseed oil and rapeseed meal has been significantly improved. As a strong chelate, phytic acid can form complexes with calcium, magnesium, zinc and other metals, which greatly reduces the bioavailability of these elements. Because phytic acid is rich in phosphorus, the utilization rate of animal phosphorus phytate is very low.

Tannin is a kind of polyphenol compound, which has a bitter taste and affects palatability. It is oxidized and polymerized under neutral and alkaline conditions, thus making the color of rapeseed meal black and producing bad odor. Polyphenols can also combine with protein to significantly reduce their nutritional value. Sinapine is soluble in water, unstable, and prone to non enzymatic hydrolysis reaction to produce erucic acid and choline. Mustard alkali has a bitter taste, which is the main factor causing poor palatability of rapeseed meal. The sinapine is related to the production of fishy eggs. This is because sinapine is decomposed into sinapic acid and choline in the chicken stomach and intestines, and choline is further converted into trimethylamine, which makes the eggs produce fishy taste.

1.3 Use of rapeseed

Rapeseed is mainly used to produce rapeseed oil and rapeseed meal, and a small amount is used for food or animal feed. Rapeseed oil is the third largest vegetable oil in the world. In addition to being used as edible vegetable oil, it can also be used to produce biodiesel, and can also be used in many industrial fields such as chemical industry and light industry; Rapeseed meal is an important raw material of plant protein, which is widely used in feed breeding industry.