Abstract
Total phenolic compounds (TPC) and the chlorogenic acids content of potato by-product extracts of two hydro alcoholic solvents (methanol, ethanol) and two extraction methods (maceration and heating-assisted extraction) were studied. The content of TPC in the extracts was determined spectrometrically according to the Folin–Ciocalteu procedure and calculated as chlorogenic acid equivalents. Soluble phenolic acids, especially the chlorogenic acids, were performed by HPLC. The antioxidant activity of potato by-product extracts was determined by using the total oxygen radical absorbance capacity (ORAC) method. The highest content of TPC was found in raw and lyophilized red waters when using ethanol as a solvent around 57 mg/g fresh weight. Heating-assisted extraction enhances this quantitative increasing. At the given operating conditions, unpeeled potato samples exhibit a higher TPC than peeled ones, showing that TPC are accumulated in skin tissue. The greatest amount of chlorogenic acid (Caffeoyl-Quinic Acids, 3, 4, 5 CQA), mainly the 5-CQA (870 ± 39.66 µg/g WM for wet matter versus DM dry matter), was obtained in the pellets and lyophilized fresh peels (skin vs. flesh). In addition, the greatest amounts of chlorogenic acids were found when potato peels were extracted with methanol. Heating-assisted extraction improved the chlorogenic acid concentration of the potato peel extracts. The total ORAC amounts recorded in the different potato fractions varied between 1500 and 1650 µM TE/g. They were higher than those of some fruits, vegetables, nuts, cereals, and sweet potato cultivar. The good correlation coefficient found between TPC, chlorogenic acids determination, and the ORAC capacity indicates that the TPC can be used as a good indicator of the antioxidant capacity of potato by-products.
Highlights
Vegetal raw material processing generates large quantities of co-products, which are affordable, and valuable starting material for the extraction of valueadded compounds such as dietary fibers, natural antioxidants, biopolymers, and natural food additives [1,2,3]
1568.02, 1546.82, and 1593.10 μM Trolox equivalents (TE)/g for 3-CQA, 4-CQA, and 5-CQA, respectively. These results indicate that the different potato fractions follow the same trends and contain a large amount of chlorogenic acids
The authors showed a different trend for oxygen radical absorbance capacity (ORAC) and DPPH radical scavenging activity, which could be attributed to the solubility of caretonoid that depends on the solvent used
Summary
Vegetal raw material processing generates large quantities of co-products (or byproducts), which are affordable, and valuable starting material for the extraction of valueadded compounds such as dietary fibers, natural antioxidants, biopolymers, and natural food additives [1,2,3]. By-products derived from potato processing can be divided into two major categories: cull or discarded potatoes (whole or cut potatoes not destined for human consumption), and potato processing wastes (derived from the manufacture of potato ingredients or potato-based food products) [5] Both discarded tubers and potato by-products represent a disposal problem to the potato industry, since the wet wastes constitute a source of plant spoilage and pathogenic infections [6]. The authors reported that chlorogenic (50.31%), gallic (41.67%), protocatechuic (7.815%), and caffeic (0.21%) acids were the major phenolic compounds detected in their study This aqueous freeze-dried extract proved to be stable during 2 weeks of storage and was as effective as butylated hydroxyanisole (BHA) in inhibiting the lipid oxidation of sunflower oil. Molecules 2021, 26, 177 ing steps: (i) Study the extraction of phenolics (total phenolic content) and more specially (ii) the chlorogenic acids from starch potato peel, potato flesh, liquid pulp, lyophilized one and red waters using alcohol solvents and different extraction methods and (iii) Evaluate the antioxidant activity using the oxygen radical absorbance capacity (ORAC) test
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