Round table: Valorisation of by-products from the olive oil extraction process

The fruit of the olive tree has been known as a noble food for thousands of years. Considering the food application of the fruit, initially, more than 9000 years ago, the fruit was used exclusively as an edible fruit. Later as a source the use of the fruit as a foodstuff was limited to the oil or fermented edible olives for centuries.

In recent years, the food industry has been increasingly trying to produce by-products from the extraction of fats and oils, proteins or sugars to produce food or animal feed. On the one hand, this helps the more cost-efficient production of the main product itself through improved utilization of raw materials, on the other hand, the extraction and utilization of other ingredients is sustainable. This also applies to „alpeorujo” the wet pomace after the oil extraction.

The technologies for oil extraction developed from the improvement of pressing processes, through the introduction of the 3-phase technique in the 1960s and 1970s, to the application of the ecological 2-phase process in the Spanish campaign of 1992/93. Since then, the treatment of the moist 2-phase pomace has repeatedly been the focus of scientific and practical investigations. This is a dispersion of fruit water together with the pulp and pits fragments. The de-oiled fruit pulp consists of approx. 65% water, 1-2% polyphenols, up to 19% sugar and 3-5% proteins.

This pomace is currently collected and de-oiled and de-pitted again in the pomace processing plants, then dried and usually incinerated. Some of the separated pomace fragments are further processed into activated carbon and then used as such.

This is where the investigations began. GEA AG is not only a supplier of machines and systems, but also develops processes to offer customers process engineering solutions that can be implemented with the machines we sell. For this purpose, GEA has its own process engineering R&D departments, for decanters and separators both in Oelde and in cooperation with the Center of Competence for olive oil in Úbeda/Jaén.

This specific process development fits in with GEA's sustainability strategy. The value-adding upcycling of a by-product of olive oil processing improves the environmental balance of processing for our customers.

Diese  spezielle Verfahrensentwicklung ist im Hinblick auf Nachhaltigkeit und Ökonomie und  neben der ständigen Verbesserung unserer Maschinen und Anlagen die Aufbereitung der Nebenprodukte, speziell des Alpeorujos, um daraus Wertstoffe zu generieren. Diese Wertestoffe sind neben dem Tresteröl auch z.B. die kleineren, bisher nicht abgetrennten Kernbruchstücke. Diese abzutrennen ist zwar technisch möglich, doch verbleibt ein nur schwer verarbeitbares Mus ohne Struktur; mit 72 bis 75% Feuchte als Nebenprodukt. Eine weitere Schwierigkeit ist die schnell einsetzende, unkontrollierte Fermentation des Zuckers zu Alkoholen und infolge des Luftkontaktes auch zu Essig. Essig- und Milchsäure werden zusätzlich durch die vorhandenen Bakterien gebildet. Zusammen mit den enzymatisch freigesetzten Fettsäuren (FFA-Gehalte > 15% sind nicht ungewöhnlich), verestern die Alkohole und bilden Wachse. Die Phenole liegen in einer toxischen Konzentration vor.
Der Vortrag zeigt Möglichkeiten auf zur Trennung des feuchten Tresters in Öl, in Fruchtwasser mit Zuckern und Phenolen, ferner in Kerne (100% der Menge) sowie in phenolarmen Trester. Dieser ist aufgrund seines erhöhten Protein- und Kohlenhydratanteils ein potenzielles Lebens- oder Futtermittel. Die Nutzung dieser Rohstoffe hängt von deren Qualität ab und diese wiederum ist nicht zuletzt abhängig von den Konditionen zur Ölgewinnung und der Ausführung der nachfolgenden Trennstufen.

This special process development is aimed at sustainability and economy and, in addition to the continuous improvement of our machines and systems, the processing of by-products, especially the Alpeorujo, in order to generate valuable materials. In addition to the pomace oil, these valuable materials also include, for example, the smaller, previously unseparated pits fragments. Although it is technically possible to separate these, what remains is a pulp without structure that is difficult to process; with 72 to 75% moisture as a by-product. A further difficulty is the rapid, uncontrolled fermentation of the sugar into alcohols and, as a result of contact with air, also into vinegar. Acetic acid and lactic acid are also formed by the bacteria present. Together with the enzymatically released fatty acids (FFA contents > 15% are not unusual), the alcohols esterify and form waxes. The phenols are present in a toxic concentration.

The presentation shows possibilities for separating the moist pomace into oil, fruit water with sugars and phenols, as well as pits (100% of the quantity) and low-phenolic pomace. Due to its high protein and carbohydrate content, the latter is a potential food or animal feed. The use of these raw materials depends on their quality, which in turn depends not least on the conditions for native oil extraction and the design of the subsequent separation stages.

The by-products have potential for use in the food, animal feed or chemical industry, for cosmetics and also for agriculture, regardless of whether they are obtained from the fresh pomace in the oil mill or from the fermented pomace of an orujera, a pomace processing company. They thus contribute to the added value of the olive oil industry.