Residual biomass from the oil sector as animal feed: preliminary data on chemical and microbiological contamination

In recent years, the design of ‘zero waste’ supply chains has taken on incredible importance. In the past, residual biomass has been treated as a waste product. However, the perspective has changed: residual biomass is now considered a useful service for the ecosystem. The olive oil supply chain is certainly one of the most promising supply chains. In addition to oil for human consumption, there are numerous by-products, usually real waste, whose disposal is very expensive. Hence, it is necessary to identify a possible reuse of these by-products. Among these, the olive pomace, rich in antioxidant substances such as carotenes, anthocyanins, tocopherols and polyphenols, can be used in various contexts, including the food industry and the zootechnical sector. A significant aspect in this context is related to the safety of by-products. This study aims at evaluating residues of chemical and biological contaminants in samples of the totally pitted dried olive cake characterized by 16% (dry matter 93.85%) of olive oil content, for animal feed use. The samples were collected from 3 big bags containing 1500 kg of olive cake each. The content of 28 mineral elements, including the potentially toxic ones, was assessed via ICP-MS. The concentration of 142 organic contaminants (PCBs, IPA, pesticides) was assessed via GC-MS. In addition, hygiene indicators were determined. The concentrations of Pb, Hg and As (0.01 mg/kg for each element) in the olive cake samples were lower than the maximum levels set by the UE 2015/186 Regulation. Among the organic contaminants, residues of very few contaminants were found, some of which not even mentioned in the current regulations. From the preliminary microbiological data, no value index of a possible contamination of this matrix emerged. To conclude, given the reassuring results obtained from the preliminary analysis and the almost total absence of chemical and microbiological contaminants, optimal use of dried olive cake as animal feed would be desirable. However, in the future, we will try to deepen, improve and optimize the quality of this matrix for the intended purpose.