UV-C Treatment Impact on the Availability of Water-Soluble Carbohydrates, Polyphenols, and Antioxidant Capacity of an Algerian Underutilized Date Fruit (Phoenix dactylifera L.)

Abstract

Underutilized dates are considered as a socioeconomically important fruit for local and global communities, such as Degla-Beida, a common date fruit variety. The aim of this research was to elucidate, for the first time, the efficiency of UV-C light treatment (over different irradiation durations 5, 10, 20, and 40 min) in the enhancement of soluble carbohydrates and phenolic compounds, and to evaluate its effect on the antioxidant capacity. Furthermore, the content of dietary fiber was analyzed: insoluble dietary fiber (11.89 g/100 g); soluble dietary fiber (5.15 g/100 g); and total dietary fiber (17.06 g/100 g). The techno-functional properties were also determined: swelling capacity (3.94 mL/g); oil holding capacity (7.38 g/g); water holding capacity (9.30 g/g); and bulk density (1.81 g/mL). All were carried out to study the potential of exploiting this underutilized fruit for other applications as for feed or food. The results suggest that UV-C technology changes minimally the total water-soluble carbohydrate content; however, this preservation technology can affect the availability of different soluble carbohydrates depending on the irradiation time (IT), increasing the high molecular weight polysaccharides with IT up to 20 min, and some oligosaccharides with IT up to 5 min. The polyphenolic content determined by HPLC-QTOF was increased when the samples were submitted to UV-C reaching the maximum at 20 min (111.62 mg/100 g) and then to decrease in those submitted to IT of 40 min (12.05 mg/100 g). Regarding antioxidant capacity in the UV-C treated samples, FRAP decreased and EC50 on DPPH increased when IT was increased, while ORAC was hardly maintained. In addition, considering UV-C radiation associated with preservation and the studied date fruit as a rich source of dietary fiber with adequate techno-functional properties, this study presents valuable information for its potential use as a new food ingredient.