STUDY OF THE ANTIOXIDANT ACTIVITY CHANGES OF COFFEE BEVERAGES DURING ITS SHELF LIFE USING IN-VITRO AND EX-VIVO METHODS

Background: Antioxidants have been one of the commercial concepts with highest impact in functional food market; however, their statement turns out a controversial topic among regulatory agencies worldwide, due to the complexity involved in demonstrating the presence and bioactivity of these antioxidants in the food. In this context, recent researches have attributed antioxidant properties to coffee beverages. Objectives: The aim of this work was to determine by in-vitro methods that coffee beverages contain phenolic substances, which may act as antioxidants, as well as evaluate how this activity can vary over time. Methods: 48 Coffee products were evaluated at two storage time conditions, namely, at the beginning and the end of their shelf life, determining the total phenolic content and their antioxidant activity by ABTS (radical capture of 2,2'-azino-bis-(3-ethyl benzotiazolin -6 - ammonium sulfonate) and DPPH (Capture the radical 2,2-diphenyl-1-picrilhidracilo); FRAP was also determined to know the ferric iron reducing activity. The objective of the above was to establish the content of phenolic antioxidant to be declared on the label. Results: The content of antioxidant polyphenols was different depending on the coffee type; the content was 328.61 +/- 31.35 and 297.17 +/- 68.48 mg gallic acid equivalents per 100 mL of beverage in roasted and soluble coffees respectively. The results obtained by the methods of ABTS, DPPH and FRAP showed through a principal components analysis that they are correlated with each other and that the storage time has an effect on the antioxidant activity of the products. Additionally, the ex-vivo antioxidant capacity was evaluated on two samples, roasted and soluble coffee beverages by the lipid peroxidation assay of the Low Density Lipoprotein (LDL); it was found that coffee beverages prevent the LDL oxidation, according to the results of polyphenols contents. Conclusions: The results allowed establishing the specifications of the content of antioxidants in coffee products to be declared on the label. This study shows that with these analysis methods the bioactivity of coffee products and its stability over time can be demonstrated.