The current study aimed at developing an effective organosolv treatment, with the objective to obtain potato peel extracts highly enriched in polyphenols. To this end, two low-cost solvents were ...employed, 1- and 2-propanol, which are considered green, but they have been rather poorly studied compared to other conventional solvents, such as ethanol. Treatment development also embraced the use of sulfuric acid, a well-examined catalyst in organosolv processes. Treatment evaluation on the basis of response surface optimization and severity demonstrated that 1-propanol was a more effective solvent, providing a maximum yield in total polyphenols of 19.28 mg chlorogenic acid equivalents per g of dry potato peel weight, attained with 40% 1-propanol/1.5% (w/v) sulfuric acid at a treatment time of 60 min and a temperature of 90 °C. This treatment was of lower severity compared to the one with 2-propanol, and it also provided almost 24% higher total polyphenol yield. The extracts produced contained chlorogenic acid as the major constituent, accompanied by caffeic acid and minor amounts of p-coumaric acid. This is the first report on such an organosolv treatment of potato peels to recover polyphenolic compounds with high efficiency.
Oat bran (OB) may be regarded as food industry by-product, with a high perspective as a bioresource in the production of high-value polyphenolic substances. On this basis, the investigation presented ...herein aimed at (i) using 1- and 2-propanol organosolv treatment and studying the effect of an alkali (sodium hydroxide) catalyst on releasing bound polyphenols, (ii) establishing models of polyphenol recovery by employing severity and response surface methodology, and (iii) investigating the polyphenolic profile of the extracts produced. Yield in total polyphenols as a function of treatment severity was satisfactorily described by linear models, indicating that for both 1- and 2-propanol treatments, temperature and time could be used interchangeably to adjust severity. Furthermore, the 1-propanol process was found to be more efficient at lower severity compared to the 2-propanol process. The optimization using response surface methodology revealed that, under identical condition settings (t = 300 min, T = 90 °C), the 1-propanol treatment afforded a total polyphenol yield of 17.15 ± 0.51 mg ferulic acid equivalents per g−1 dry mass, whereas the 2-propanol treatment gave a yield of 14.78 ± 1.11 mg ferulic acid equivalents per g−1 dry mass. Liquid chromatography–tandem mass spectrometry analyses showed that the extract produced from the 1-propanol treatment was significantly more enriched in ferulic acid and p-coumaric acid compared to the extract generated with the 2-propanol treatment. Moreover, the antioxidant activity of the extracts was in concurrence with the polyphenolic composition. Based on the evidence, the alkali-catalyzed, 1-propanol organosolv treatment of OB is proposed as a sustainable and efficient methodology to recover multipurpose natural antioxidants.
