A Rapid and Inexpensive Spectrophotometric Method for Tyramine Detection
Silvana Ledesma, Cristina Rubio, and Pedro Aredes-Fernández*
*Consejo Nacional de Investigaciones Científicas y Técnicas; Universidad Nacional de Tucumán, Ayacucho 471, San Miguel de Tucumán, Tucumán 4000, Argentina (firstname.lastname@example.org)
Lactic acid bacteria (LAB) are the primary microorganisms responsible for biogenic amine synthesis in wine, organic compounds that affect human health and the quality of the final product. The presence of tyramine was evaluated using an inexpensive and rapid method implemented in our laboratory. The assay was a modification of the method used by Undenfriend and Cooper to detect tyrosine in human urine. The samples consisted of the supernatants obtained after growing 30 LAB isolates from Tucuman wines in decarboxilating culture medium. The bacteria were previously screened in agar medium as in Maijala and in a commercial decarboxilating Moeller broth medium to detect tyrosine decarboxylase. The bacteria were adapted in MRS-Tyrosine medium for five to 10 days and then inoculated individually in the Moeller medium and incubated 96 hr at 28°C. Uninoculated Moeller medium was used as negative control. Several positive controls were performed by adding exact tyramine concentrations to uninoculated Moeller medium for calibration. All samples were filtered and clarified with polyvinylpyrrolidone or activated charcoal and then deproteinized with 10% trichloroacetic acid. The 20 selected LABs produced tyramine in different concentrations, with the highest concentrations in supernatant obtained from Lactobacillus sp. (23.24 mg/L). All experimental procedures were performed in triplicate. These results show that this assay is a fast, efficient and low-cost method to quantify tyramine in culture medium.
Funding Support: CONICET – Proyect PIP 2014-627