Application of experimental design and response surface methodology to optimize the procedure to obtain a bactericide and highly antioxidant aqueous extract from orange peels

In recent years there is a growing demand for healthy and safe food, without added preservatives or synthetic antioxidants. In this regard, plant extracts have promising future due to their high contents of bioactive compounds, especially in phenolic and polyphenolic compounds that exhibit antimicrobial and antioxidant activities. For this reason, the plant extracts could form the basis of many applications, including the preservation of fresh and processed foods. In this work, the methodology to obtain orange peel extracts with high bioactive properties is presented. To adjust the extraction conditions, experimental design and response surface methodology were applied to establish the optimum value of all the experimental variables that have influence in the extraction system. Total phenolic contents and antioxidant activity values were used as response parameter. The peel extracts, obtained with the proposed methodology, exhibited a high content of phenolic compounds, high antioxidant and antimicrobial activity, against Escherichia coli and Listeria innocua (in-vitro experiments). Finally, to demonstrate the feasibility of the peel extracts, they were used as natural additive in apple juice reducing significantly juice browning and the microbial load for both bacteria.