Oxytetracycline residues from spiked ovine milk to cheese: technological implications

Antibiotics are used in livestock, in order to ensure the health of producing-food animals. Their wide use can cause an undesirable presence of residues in milk and milk products, representing a risk for human health. To guarantee the safety of consumers, the Commission Regulation (EU) 37/2010 states the Maximum Residue Limit (MRL) of pharmacologically active substances in foodstuffs of animal origin, included milk, but no limits are specified for cheese. In addition, residues in milk can have negative technological effects during the manufacturing of dairy products. Oxytetracycline (OTC) is one of the most used veterinary antibiotics in Sardinia, due to its effectiveness and low cost. The aim of this PhD thesis was to study the distribution, between cheese and whey, of OTC added in ovine milk at MRL level, and to verify technological effects during the cheese-making process. The first part of thesis was a preliminary investigation conducted by lab cheese-making method. In the second part were conducted experimental cheese-makings from whole raw milk spiked at MRL level, to understand the partition of molecule and to evaluate technological effects during the manufacturing and ripening. In the third and fourth parts were performed experimental cheese-makings from whole thermised milk spiked at half and MRL levels, to assess the influence of the thermisation on the recovery and partition of OTC, and to understand the effect of residues on the starter culture development.