Table 1: Total Polyphenol Index (TPI), DPPH, FRAP, and ABTS assays mean values and standard deviation (SD) of untreated, oven-dried, and freeze-dried grapefruit peel extracts.

TPIDPPHFRAPABTS
Mean ± SDMean ± SDMean ± SDMean ± SD

Fresh white grapefruit49.14a  ±  7.9132.46a  ±  0.8060.30a  ±  3.25122.34a  ±  6.22
Fresh pink grapefruit27.95b  ±  0.8325.18a  ±  8.5244.82b  ±  5.3599.46a  ±  12.09
White grapefruit dried at 45°C52.95a  ±  4.8348.05b  ±  3.7571.57a  ±  0.60194.81b  ±  3.80
Pink grapefruit dried at 45°C42.29a  ±  3.3035.26a  ±  3.6265.86a  ±  5.28175.87b  ±  5.64
White grapefruit dried at 60°C63.35c  ±  0.8486.76c  ±  8.40105.86c  ±  22.39339.66c  ±  33.61
Pink grapefruit dried at 60°C49.36ac  ±  3.5750.07b  ±  2.2679.43ac  ±  5.16210.78b  ±  2.19
Freeze-dried white grapefruit84.60d  ±  10.80122.83d  ±  15.95181.80d  ±  25.97537.48d  ±  36.10
Freeze-dried pink grapefruit66.70  ±  1.54110.98d  ±  13.76207.74d  ±  14.65455.38  ±  1.95

TPI are expressed as mg gallic acid equivalents per gram of dry weight.
DPPH, FRAP, and ABTS assays are expressed as mg trolox per gram of dry weight.
Different letters in the same column denote a significant difference according to the Student-Newman-Keuls test, at .