Sunflower oil production has the following manufacturing processes: cleaning of the seeds, grinding of the seeds, pressing and extraction of crude oil from these seeds and then further refining the oil obtained before packaging. A volatile hydrocarbon like hexane is used as a solvent to extract the oil.
- Solvent extraction
CLEANING THE SEEDS:
The harvested sunflower oil seeds are passed over magnets to subtraction any metal traces, and other impurities are getting rid of by cleaning sieve and destoners. Then the outer covering (hulls) of the seeds are removed to get pure seeds.
Sunflower seeds from the oil-type contain about 20% to 30% hulls that are sometimes removed before oil extraction to ensure the quality of both oil and sunflower meal. De-hulling is completed when the seed has a moisture content of 5% after cleaning. The usual procedure consists of cracking the seeds by the mechanical action of centrifugal or pneumatic sheller, which can also be completed by abrasion. Then the resultant mixture is winnowed to separate the hulls from the kernels. Some oil sunflower seeds have thin hulls that are hard to remove, so they can be free from de-hulling to avoid oil loss.
GRINDING THE SEEDS:
The de-hulled seeds are ground into coarse meal to give a larger surface area to be pressed. Hammer mills or grooved rollers are mainly used to crush the coarse meal into uniform fine particles. Then the meal is heated to enable oil extraction, though impurities are released with oil during this procedure and such impurities should be removed before the oil is declared edible.
The heated meal is fed into a screw press which progressively increases the pressure from 60 kps to 950kps, to 850kps as the meal is passed through a slotted barrel. At the same time, the oil is squeezed out during the slots in the barrel and recovered.
EXTRACTION OF THE ADDITIONAL OIL:
Volatile hydrocarbon solvents are used to procedure the remaining oil cake through solvent extraction so as to achieve maximum yields. The most normally used solvent is hexane which dissolves the oil out of remaining oil cake. The solvent is then distilled out of the oil, passed during the matter and then collected at the bottom.
REMOVAL OF SOLVENT TRACES:
Around 90% of the volatile solvent left in the extracted oil, evaporates and it’s composed for reuse. Then a stripping column is used to recover the remaining solvent. In this procedure, the oil is boiled by steam and the solvent evaporates, condenses and is collected separately.
OIL REFINING AND PROCESSING:
Extracted and desolventized sunflower oil should be further processed to create an edible product. Edible oils are refined to develop the flavour, odour, colour and solidity using processes that degum, neutralize, bleach and deodorize the oil. These oil refining processes eliminate contaminants such as phosphatides, free fatty acids, and pro-oxidants.
Further processing of sunflower oil and fats is sometimes de4sired. Some oils are winterized or dewaxed and some are modified to differ melting characteristics. By-products can be more processed to create value-added products or reduce costs.
The final stage involves deodorizing the oil bypassing the steam over hot oil placed in a vacuum at temperatures between 225 C and 250 C. This allows the volatile components steady for the taste and odour to evaporate from the oil. One percent citric acid is added to the oil to inactivate some trace metals present, thus preventing oxidation within the oil, thereby prolonging the shelf life of the oil.
PACKING THE OIL:
Pure oil is measured or packed in clean containers, and the usual ones are bottles for domestic sales in specialty stores, or cans for exports.