Table 4.
Mean values and standard deviation of the phenolic compound content for the four specimens of olive oil samples during storage.
| Storage Time (Months) | FIL-HPP | FIL | HHP | CON | p F | p HP | p T | p F × T | p F × HP | p HP × T | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.5 | 1 | 6 | 0.5 | 1 | 6 | 0.5 | 1 | 6 | 0.5 | 1 | 6 | |||||||
| Sum of oleuropein and its derivatives | 333 ± 22 a | 306 ± 40 a | 309 ± 29 a | 346 ± 9 a | 317 ± 26 a | 290 ± 25 a | 218 ± 42 b | 228 ± 37 b | 248 ± 56 b | 229 ± 45 b | 229 ± 44 b | 241 ± 58 b | *** | ns | ns | ns | ns | ns |
| 3,4-DHPEA-EDA | 122 ± 14 a | 135 ± 16 a | 126 ± 25 a | 123 ± 7 a | 112 ± 17 a | 131 ± 15 a | 65 ± 22 b | 71 ± 23 b | 64 ± 21 b | 67 ± 24 b | 68 ± 11 b | 60 ± 22 b | *** | ns | ns | ns | ns | ns |
| Hydroxytyrosol | 1 ± 0 | 2 ± 0 | 3 ± 0 | 1 ± 0 | 1 ± 0 | 3 ± 0 | 6 ± 1 | 6 ± 2 | 15 ± 3 | 8 ± 3 | 7 ± 4 | 17 ± 3 | *** | ns | *** | *** | ns | ns |
| Sum of ligstroside and its derivatives | 106 ± 15 | 109 ± 15 | 128 ± 23 | 118 ± 22 | 109 ± 17 | 116 ± 13 | 124 ± 23 | 113 ± 22 | 135 ± 25 | 125 ± 26 | 115 ± 29 | 126 ± 28 | ns | ns | ns | ns | ns | ns |
| p-HPEA-EDA | 71 ± 6 | 68 ± 8 | 73 ± 14 | 73 ± 5 | 67 ± 12 | 75 ± 9 | 70 ± 12 | 65 ± 13 | 70 ± 14 | 74 ± 14 | 68 ± 21 | 64 ± 17 | ns | ns | ns | ns | ns | ns |
| Tyrosol | 2 ± 0 | 2 ± 0 | 3 ± 0 | 2 ± 0 | 2 ± 0 | 3 ± 0 | 2 ± 1 | 3 ± 0 | 6 ± 1 | 3 ± 1 | 4 ± 2 | 9 ± 6 | *** | ns | *** | *** | ns | ns |
| Total phenolic compounds | 448 ± 20 | 474 ± 42 | 484 ± 46 | 479 ± 19 | 468 ± 48 | 469 ± 37 | 418 ± 66 | 429 ± 52 | 481 ± 81 | 434 ± 68 | 420 ± 61 | 472 ± 72 | ns | ns | ns | ns | ns | ns |
| R-Index (10−2) | 1 ± 0 | 1 ± 0 | 2 ± 0 | 1 ± 0 | 1 ± 0 | 1 ± 0 | 3 ± 1 | 3 ± 2 | 6 ± 1 | 4 ± 2 | 4 ± 3 | 8 ± 5 | *** | ns | *** | *** | ns | ns |
*, ** and *** indicate significant differences by 3-way ANOVA at p < 0.05, p < 0.01 and p < 0.001, respectively, for the treatments (F = filtration; HP = high pressure), the storage time (T) and their interaction; different letters (i.e., a, b, c for the three storage times; x, y for filtered and unfiltered samples) indicate a statistically significant difference of the main effects with the Tukey HSD post hoc test (p < 0.05), while the significant interactions are discussed in the main text. ns = not significant; nd = not detected. CON = veiled and not HHP-treated oil samples; HHP = veiled and HHP-treated oil samples; FIL = filtered and not HHP-treated oil samples; F-HHP = filtered and HHP-treated oil samples; 3,4-DHPEA-EDA = dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol; p-HPEA-EDA = dialdehydic form of decarboxymethyl ligstroside aglycones. All concentrations are expressed in mg/kg. Number of replicates = 4.