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Grape pips
8 De Smet plants are processing grape pips.
Origin
Grape pips are firstly a by-product of the wine industry. Around the Mediterranean sea, people try to take some benefit out of the huge amounts of marc available after each grape crop.
Grape pips may contain from 5 to 18% of oil according to climatic conditions and maturity of the grape. After a severe decorticating, the oil content may rise to 30%.
The marc, in which the grape pips are glued, is firstly water washed, which results in a low quality wine amounting to 5° alcohol, which after distillation gives a fine alcohol of 70°.
The separated stalks are used as combustible and the separation of the grape pips from the earth is done before decorticating which gives 40% of almonds with 30% of oil and 40% of shells with 8-10% of oil.
The oil extracted by cold pressing is used in diet while the solvent extracted one gives a current-quality oil.
Process
For solvent extraction, the grape pips are cracked, humidified and heated to 50°C before flaking. A temperature of 50°C is a maximum to avoid melting of the waxes contained in the shells.
The extracted meal has a 1-2% residual oil content
The crude oil is dark and with a poor appearance; but the refined oil is of a light yellow, with a fruity taste like olive oil. It contains a high percentage of Vitamin E (120 mg/100 gr. of oil) and it thus requires storage in tins (in no light).
Composition
It is a semi-siccative oil with variable composition depending on climate, grape maturity, time between process and grape crop. It contains :
- 15-20% of oleic acid
- 64-74% of linoleic acid
- 7-9% of palmitic acid
- 3-5% of stearic acid
- iodine value : 130-145
- saponification value : 188-196
- melting point : -13/-18°C
- titer : 15-18°C
- viscosity at 20°C : 0.7° Engler
End uses
The oil has an important role in diet thanks to its vitamin E content and its unsaturated fatty acids content (cholesterol).
As technical oil, it is used in the manufacture of resins, paints and varnishes.
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