Oils, pigments, and antioxidants obtained from food by-products

In the Southern European countries (Spain, Italy, Greece, France), olive and grape cultivation and processing are some of the main agri-food businesses. However, the industrial processes of these products generate millions of tons of waste that are either discarded or have limited applications (e.g., fertilizers or animal feed). Nevertheless, these by-products, far from being useless waste, are a rich source of high-value bioactive compounds for health, as they contain fibers, vitamins, or food additives. The question posed by the managers of these industries is whether it is possible to obtain added value or new marketable products from what are currently waste products from grape and olive processing. In both cases, it is not only possible but can even lead to business diversification, growth drivers, and penetration into other sectors such as additives and ingredients, pharmaceuticals, cosmetics, and parapharmaceuticals.

The waste from olive processing contains beneficial health bioactive compounds and presents an opportunity for industrial reuse

Olive pulp and the wastewater from olive milling contain antioxidant compounds and fiber with applications and interest for various uses (enriched foods, cosmetics, dietary supplements, additives, etc.). Their recovery through supercritical CO2 extraction represents a sustainable and clean industrial extraction process, with high levels of purity and the possibility of significant industrial scaling, supported by rigorous profitability and cost studies tailored to each case.

From an environmental management problem to a new commercially valuable product, thanks to the application of supercritical CO2 extraction

Currently, the European Union (with Spain as the world’s leading producer) processes millions of tons of olives for oil production. The residues obtained after the milling process mainly consist of wastewater, olive pomace, and pulp. These residues generally face management challenges in most small oil processing mills located throughout the rural areas of these European countries. To recover essential oils, fiber, and antioxidants from the milling wastewater and olive pulp, processes specially adapted to the characteristics of each secondary raw material must be established. The processing stages may include:

• Pre-treatment of the residues.
• Extraction of the processed residues, dried, and homogenized.
• Purification of the extracts.
• Drying of the purified extracts.

Among the extraction technologies, solvent extraction and supercritical CO2 extraction can be highlighted. The advantages of the latter technology, verified and validated at AINIA in numerous applied research projects, are noteworthy for:

• High purity of the obtained extract, with the absence of toxic solvents in the final products, significantly increasing their quality and value in the market.
• Suitability for recovering thermolabile substances soluble in CO2.
• Configuration of safe processes without the use of toxic substances and with a moderate cost of the extraction agent.
• Industrial scaling adapted to each process with cost-profitability studies tailored to each extraction.

Supercritical CO2 for extracting value from grape pomace residues used in winemaking, including fiber, tannins, polyphenols, lipids, sugars, tartaric acid, and more

The case of grapes presents another example and a great business diversification opportunity for winemaking industries. During grape processing, a significant amount of solid waste is generated. These residues represent approximately 20 percent of the dry matter of the harvested grape. Quantifying this, we see that processing 100 kilograms of grapes produces about 25 kilograms of pomace: 50 percent consists of grape skins, 25 percent of stems, and the remaining 25 percent of seeds. Typically, wineries take the residues from their production processes (pomace and general waste) to distilleries, where alcohol recovery via distillation takes place, along with the extraction of grape seed oil, recovery of tartaric acid, and incineration of the final solid residue. Also, these processing residues are managed by small wine producers by spreading them on the land as fertilizer to take advantage of their mineral content, using them as fodder, or destroying them. The commercial value of grape residues depends on their moisture content, the presence of grape stems, and the amount of sugars and alcohol they contain. However, grape pulp contains valuable bioactive compounds that have beneficial effects on health, such as:

• Fiber (17-21%)
• Tannins (16-27%)
• Polyphenolic compounds (2-6.5%)
• Lipids (7-12%)
• Sugars (3%)

Of all of them, polyphenols (mainly ellagic acid and quercetin) and resveratrol are exceptionally important due to their antioxidant properties. With a supercritical CO2 extraction process similar to the one described in the case of olives, pigments, antioxidants, and fiber can be obtained on an interesting industrial scale based on economic viability studies tailored to the by-product to be processed, the purity level of the extract to be obtained, the extraction process to be developed, and the volume of tonnage to be managed. With a supercritical CO2 extraction process similar to the one described in the case of olives, pigments, antioxidants, and fiber can be obtained on an interesting industrial scale based on economic viability studies tailored to the by-product to be processed, the purity level of the extract to be obtained, the extraction process to be developed, and the volume of tonnage to be managed.