Effect of different drying temperature on the antioxidant properties of the apple cultivars ‘Idared’ and ‘Golden Delicious’

Abstract

The apple (Malus × domestica Borkh.) is the most consumed in the fresh form fruits but can also been used as an important raw materials in the food industry for the production of juices, nectars, baby foods, refreshing soft drinks, spreads (marmalade, jam), compote, apple vinegar, brandy and dried fruits. In this paper, the apple cultivars ‘Idared’ and ‘Golden Delicious’ were dried in the laboratory dehydrator (air temperature of 60 °C for a period of 4 h and air temperature of 70 °C for a period of 3 h) in order to determine whether elevated temperature has an effect on the antioxidant properties of the processed apple. The total phenolic content as well as antioxidant activity were evaluated by three compatible UV-VIS spectrophotometric methods. The results showed that the total phenolic content as well as antioxidant activity significantly increased after drying calculated in relation with unprocessed samples, for both apple cultivars. These results indicate the assumption that an increase of the investigated properties could occur due to the non-selective methods for the determination of total phenolics, and also because of the potential formation of Maillard reactions products, which have been confirmed to increase the antioxidant activity of various food products.

Plodovi jabuke (Malus × domestica Borkh.) se najviše koriste kao stono voće, a značajna su sirovina i u prehrambenoj industriji za proizvodnju sokova, nektara, dečije hrane, osvežavajućih bezalkoholnih pića, namaza (marmelada, džemova), kompota, jabukovog sirćeta, rakija i sušenih plodova. U ovom radu, plodovi jabuke sorte Idared i Golden Delicious sušeni su u laboratorijskom dehidratoru na različitim temperaturama (temperatura vazduha od 60 °C u trajanju od 4 h i temperatura vazduha od 70 °C u trajanju od 3 h) radi utvrđivanja uticaja primenjenih temperatura sušenja na antioksidativna svojstva osušenog proizvoda. Sadržaj ukupnih fenola, kao i antioksidativna aktivnost određeni su trima kompatibilnim UV-VIS spektrofotometrijskim metodama. Rezultati su pokazali da su u osušenim uzorcima jabuke sadržaj ukupnih fenola i antioksidativna aktivnost bili značajno veći u odnosu na sveže uzorke kod obe ispitivane sorte. Ovakvi rezultati ukazuju na pretpostavku da je do povećanja ispitivanih svojstava moglo doći kako zbog neselektivnosti metode za određivanje ukupnih fenola, tako i zbog potencijalnog stvaranja produkata Maillard-ovih reakcija, za koje je potvrđeno da povećavaju antioksidativnu aktivnost različitih prehrambenih proizvoda.