Acid liquefaction of potato (Solanum tuberosum) and sweet potato (Ipomoea batatas) cultivars peels – Pre-screening of antioxidant Aactivity total phenolic and sugar contents

In the present study, the liquefaction of both regular and sweet potato peels was conducted to investigate the bio-oil produced, the sugar and total phenolic content, and antioxidant activity. Initially, the bio-oil obtained after liquefaction was partitioned into two different fractions, a hydrophilic fraction and the other consisted of the portion that contained the apolar compounds. Afterward, the samples of the whole bio-oil, aqueous extract, and organic phase of both cultivars were analyzed by attenuated total reflection- Fourier Transform infrared (ATR-FTIR) spectroscopy, hydroxyl number, and acid value. This was done in combination with assessment of the sugar and total phenolic contents and antioxidant activity. The samples demonstrated a considerable content of phenolic moieties in their composition. The antioxidant activity, which was assessed by the 2,2-diphenyl-1-picrylhydrazyl radical method, revealed that the antioxidants of the liquefied products and its extracts were generally better than that of butylated hydroxytoluene. Glucose, sucrose, and maltose were identified and quantified within all of the samples.Rui Galhano dos Santos would like to acknowledge FCT-Fundação para a Ciência e Tecnologia for the Postdoctoral Grant SFRH/BPD/105662/2015 that supported this work.