Inhibitory effect of microwaved thinned nectarine extracts on polyphenol oxidase activity

• Thinned nectarines treated with microwave radiation generate Maillard products.
• Maillard reaction products generated are mixed type inhibitors.
• The inactivation of polyphenoloxidase enzyme was irreversible.
• Thinned nectarine extracts could be used as natural antibrowning agents.

By-products from agricultural practices or from the fruit processing industry are a source of bioactive compounds that could be used in the food industry. Such by-products include thinned fruits, which are expected to contain high quantities of interesting compounds. One possible application of this fruits is the prevention of the enzymatic browning suffered by fruits and vegetables after minimal processing. The aim of this study is to determine the in vitro and in vivo activity of microwaved extracts obtained from thinned nectarines. It has been observed that in vitro the extracts obtained after the application of high microwave power levels (500, 1000 and 1500 W) are mixed type inhibitors of polyphenoloxidase enzyme, showing an irreversible inactivation. This inhibition could be attributed to the Maillard reaction products formed during the microwave treatment. In vivo, a solution of 2% of the extract obtained at 1500 W inhibited the enzymatic browning in minimally processed peaches for 8 days of storage.