Characterization of preservation solutions of Spanish black olives and potential for acrylamide formation in processed products

The aim of this study was to characterize olive preservation solutions and establish a relationship between their composition and the potential formation of acrylamide in processed olives. The chemical and microbial profile of 37 preservation solutions from 4 different Spanish factories were analyzed along with acrylamide formation in the sterilized solutions. Amino acids, sugars, organic acids, phenolic and oleosidic compounds and acrylamide were monitored by HPLC, and yeasts and bacteria were analyzed by using metagenomic approach. Great variability was found among samples and factories, not only in chemical parameters but also in microbial predominance. While individual amino acids, phenolic and oleosidic compounds, sugars and organic acids did not show significant correlation with the acrylamide formed, a multivariate model accounted for ∼90 % of the variation in acrylamide content using the NIPALS model with 7-fold cross validation. Glucose, asparagine and hydroxytyrosol had high positive coefficients. Moreover, it must be noted that the acrylamide level depended on the pH during sterilization, with a maximum at pH 7 and lesser amounts formed at pH 4 and 9, which is in accordance with Maillard reactions behavior. Likewise, ultrafiltration assays revealed that the precursors of acrylamide formation in the preservation solutions must possess low molecular weight (<1000 Da). Sterilization of these solutions prior to the darkening stage could be a reliable method to estimate acrylamide formation in the final product. Therefore, processors could change the elaboration method of black ripe olives for some batches of olives expected to have a potential high final acrylamide content. • Great chemical and microbiological variability in preservation solutions of Spanish factories. • Acrylamide formation was higher at pH 7 in black ripe olives. • Asparagine and sugars were ruled out as limiting factors for acrylamide formation in black ripe olives. • Unidentified molecules under 1000 Da may be influencing acrylamide formation. • Preservation solutions can be used for estimating acrylamide formation in black olives.