Impact of different processing technologies in the development of effective and innovative natural antioxidant from onion

Abstract: Leveraging on natural raw materials to provide innovative ingredients for food and beverages, pet food and aquafeed is key to fulfilling the increasing needs of the Food industry, while ensuring food quality. The development of natural antioxidants is therefore a major challenge since consumers are looking for minimally processed and eco-friendly products.

The creation of innovative antioxidants from a wide range of plants was investigated thanks to various technologies such as maceration, hydrodistillation, ultrasounds, microwaves, purification and subcritical water. The antioxidant performance of the different extracts was evaluated using DPPH scavenging test and ferric reducing antioxidant power (FRAP). The Folin-Ciocalteu method and UPLC-DAD or GC-MS were used to analyze their compositions.

Among the huge number of plant raw materials listed in the literature, Onion (Allium cepa L.) is known to provide a good antioxidant activity thanks to three main bioactive compounds from the polyphenolic flavonoid family. The challenge is to extract active molecules from entire onions to maximize antioxidant activities.

Total polyphenols content and antioxidant activity of onion extracts obtained by maceration, hydro distillation, ultrasounds, microwaves, subcritical and resin purification were studied. The IC50 value of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical in microwaves samples extracted with 100% water was the highest, followed by maceration with 100% water. The other extracts showed IC50 ranging from 2.5mg/mL to 0.08mg/mL on dry matter. FRAP value was comprised between 800 and 30µmol Trolox/g in dry matter. Total polyphenols content was low for conventional water extraction compared to other extractions with ethanol with approximatively 3 % on dry matter of total polyphenols in gallic acid equivalent.

The composition and the partition of each molecule vary from one extract to the other according to the extraction method and explain these different antioxidant capacities.