The Reinartz cold-press machine used at VPO has a capacity to process between 300kg and 350kg of seed per hour.
“If we were to run it at full capacity, working every day of the year, we’d be able to process around 3 000t/ year through the plant,” says Homsek.
When the seed arrives on site, it is placed into a metal silo and then fed into machinery to be partially dehulled. Any foreign objects are removed before the oil is pressed out at very high pressure.
The process replicates that used to produce cold-pressed extra-virgin olive oil. The crude sunflower oil is piped into tanks and then into the factory for the next step in the process, known as winterising.
“Crude sunflower oil starts to whiten when the temperature drops below 14°C. We winterise it by taking it down to 6°C and then putting it through a cloth filter, after which it can be bottled.”
Oil yield is influenced both by growing conditions, such as drought, and the temperature during pressing. Homsek says the ideal is 23°C, and the press is therefore operated for 24 hours a day during the production season to prevent it from cooling.
A good return is about 28%, or 280kg of oil per ton of seed. The cold-press process yields lower oil volumes than chemical refining; however, the former is entirely mechanical and 100% natural, which research has shown is best for retaining healthy fats such as omega-9 fatty acids, according to Homsek.
“Refined oil is chemically extracted. This gives it a neutral taste but it destroys most of the nutritional value.”
In addition, although oil yield from the cold-press process is low, the by-product is a sunflower oilcake with high oil content and no added chemicals, which VPO sells to livestock owners and feed manufacturers.
According to Homsek, HO sunflower oil has almost the same fatty acid composition, and therefore health benefits, as olive oil. At the same time, it has the advantage of a higher smoking point: 238°C.
“This means you can use it for deep frying,” he says.
The reason for this lies in chemistry: the single bond (18:1) high-oleic acid structure results in a very stable oil, a fact verified by research conducted by the University of the Free State, which has given the oil its ‘seal of stability’.
“What is also very important for us is that we’ve been endorsed by the Heart and Stroke Foundation, as well as the Cancer Association of South Africa [since the end of 2018].”