Scientists from the Universidad Autonoma de Nuevo Leon report that slicing and then drying eggplant in an oven before being turned into flour had the highest value of polyphenols and antioxidants, compared to other ways of preparation.
Writing in the journal Molecules, the authors noted that this preparation method was better than mincing and then drying; or slicing, freezing and then drying. However, all treatments led to similar fiber, protein, and fat contents in the flour.
“In general terms, the [flour made from eggplant that was sliced and dried in an oven] is a potential ingredient for the preparation of foods with functional properties since it is rich in phenolic compounds and antioxidants,” they wrote.
Eggplant as a nutraceutical resource
Total global production of eggplant (aubergine) exceeded 52 million tonnes in 2017, according to the Food and Agricultural Organization of the United Nations.
China is responsible for 63% of all production, followed by India (24%) and Egypt (2.5%). Mexico ranks at number 11 on the list of producers, with the majority of this being exported to the US.
“Eggplant has a non-climacteric pattern of respiration, which leads to a short shelf life despite being harvested in immature stages of development,” explained the researchers. “Therefore, the use of eggplant is suggested as a flour with high nutritional value, which can also be used as an antioxidant of natural origin.
“Therefore, the objective of this work is to evaluate the physicochemical, functional, and nutraceutical properties of eggplant flour as a proposed functional ingredient.”
Flour production and characteristics
The Mexican researchers prepared eggplant flour using different techniques and found that the total phenolic content and total flavonoid content were highest for the flour prepared from eggplant that was sliced and dried in an oven, with values of 18,227 mgCAE/kg Flour DW and 15,753 mgCatE/kg Flour DW, respectively.
The total antioxidant capacity, as measured using the DPPH, ABTS, and FRAP methods, was consistently highest for the same flour, said the researchers.
“Eggplants generate a cellular disruption when being cut, with a loss of compartmentalization that allows contact between enzymes responsible for browning, such as polyphenoloxidase (PPO) and phenolic substrates. Treatments such as mincing and freezing, and the time of exposure to air and light contribute to the generation of the browning of the eggplant, thus affecting both its content and antioxidant capacity,” explained the researchers.
23(12), 3210; doi:10.3390/molecules23123210
“Physicochemical, Functional, and Nutraceutical Properties of Eggplant Flours Obtained by Different Drying Methods”
Authors: J.R. Rodriguez-Jimenez et al.