Phenolic content, composition, antioxidant activity, and their changes during domestic cooking of potatoes.

Potatoes in the diet contribute significantly to antioxidant daily intake worldwide. The influence of different domestic cooking conditions, boiling, microwaving, and baking, on total phenolics (TP), antioxidant capacity, phenolic composition, and tryptophan content was studied using eight commercial potato varieties. The antioxidant capacity was detected by the methods of oxygen radical absorbance capacity assay (ORAC) and the 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH(*)) assay. The phenolic composition and tryptophan content were determined using high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD), whereas phenolics and tryptophan were identified by means of HPLC-mass spectrometry, HPLC-DAD, and authentic standards. Antioxidant capacity was influenced by potato variety and cooking conditions; however, cooked potatoes retained 68-97% ORAC value depending on cooking procedure and variety. Chlorogenic acid and its isomers dominated the phenolic composition of each variety involved in this study. ORAC and TP were highly and positively correlated (r = 0.9119). Norkotah ranked highest in chlorogenic acid content and antioxidant value. Principal component analysis showed different cooking processes did not influence the trend of the antioxidant profile of the eight potato varieties, but specific compounds exert influence on the antioxidant capacity. The results imply that the potato varieties rich in antioxidant components could be good antioxidant sources as activities are not greatly affected by different cooking conditions.

Proanthocyanidin profile and ORAC values of Manitoba berries, chokecherries, and seabuckthorn.

Six Manitoba fruits were analyzed for their phytochemical content and antioxidant activity in order to increase their production and marketability. The major proanthocyanidins (flavanols) present in whole fruit, juice, and pulp of strawberry, Saskatoon berry, raspberry, wild blueberry, chokecherry, and seabuckthorn were measured. The extraction and purification were facilitated using flash column chromatography, while separation and identification were accomplished by using HPLC and LC-MS techniques. The total proanthocyanidin contents varied from 275.55 to 504.77 mg/100 g in the whole fruit samples. Raspberry contained the highest content, and seabuckthorn showed the lowest content of total flavanols. The highest concentration of proanthocyanidin in juice was found in Saskatoon berry (1363.34 mg/100 mL) and the lowest value in strawberry (622.60 mg/100 mL). HPLC and LC-MS results indicated that epicatechin was the most abundant flavanol followed by B2 in the berry samples, while no catechin or B1 was detected in these fruits. A series of oligomers and polymers were detected in all samples. The recovery percentage was obtained from the ratio of the unspiked samples to the area of spiked samples. Monomers, dimers, oligomers, and polymers gave recovery ranges of 83-99%. The lipophilic and hydrophilic antioxidant capacities of whole fruit, juice, and pulp extracts were measured by the oxygen radical absorbance capacity (ORAC) procedure. In whole fruits, the ORAC values varied from 135 to 479 mg/100 g TE in the MeOH fraction. The corresponding ORAC values varied from 115.30 to 733.15 mg/100 g for the acetone fraction. In juice, all berries showed the same antioxidant capacity (P > 0.05) (133.0-312.0 mg/100 g) in the MeOH fraction, with the exception of raspberry (603.0 mg/100 g). Overall, MeOH fractions mainly contained monomers and dimers with smaller amounts of oligomers and polymers when compared to the acetone fractions. Acetone fractions mainly contained polymers and some oligomers. Although acetone fractions contained a higher quantity of total proanthocyanidins, their antioxidant capacities were lower than MeOH fractions.