Turbidity characterization as a decision-making tool for extra virgin olive oil stability treatments

Abstract

The extra virgin olive oil (EVOO) commercialized by olive oil companies usually has highly variable turbidity characteristics. Ten veiled EVOOs with different water content, insoluble solid content, water activity, degree of turbidity, and microbial cell count, and their respective filtered samples, were studied both to assess the risk of degradation phenomena and to suggest a rapid method to measure oil quality stability. The EVOO samples were analyzed for legal parameters, phenolic compounds, volatile organic compounds, and sensory attributes, immediately after purchase and after 45 and 180 days of storage at room temperature in dark conditions. A statistically significant relationship was found between water content and oil degradation during storage; hydrolytic phenomena and microbial spoilage occurred, causing variations in the oil quality in terms of phenolic compound hydrolysis, fusty and fruity sensory attributes, and volatile compound content. A > 0.2 %w/w water content value was measured as predicting a high risk of oil degradation. Moreover, since the research determined an original relationship between water content and NTU, we proposed that olive oil companies should adopt the following decision-making approach: EVOO with NTU values > 100–200 should be subjected to a schedule of treatments that reduce water content in a short time.