Table 1.
Characteristics of Ishikunibu and ‘Kugani’ harvested in December and February
| Harvesting date | Variety | Fruit weight (g) | Fruit diameter (cm) | Moisture content (%) |
|---|---|---|---|---|
| December 13, 2018 | Ishikunibu | 29.7 | 4.27 | 85.6 |
| Kugani | 43.6 | 4.66 | 87.0 | |
| February 18, 2019 | Ishikunibu | 33.6 | 4.95 | 85.5 |
| Kugani | 42.6 | 5.15 | 84.6 |
Figure 1.
Photos of the Ishikunibu (left) and ‘Kugani’ (right) fruit harvested in December (upper row) and February (bottom row)
Table 2.
Chemical components of Ishikunibu and ‘Kugani’ harvested in December and February
| Harvest month | December | February | ||
|---|---|---|---|---|
| Variety | Ishikunibu | Kugani | Ishikunibu | Kugani |
| PMFs (mg per g of DW) | 1.97±0.02aA | 4.20±0.18bA | 1.34±0.02aB | 3.70±0.05bB |
| Sinensetin | 0.19±0.00aA | 0.28±0.1bA | 0.14±0.01aB | 0.26±0.01bB |
| Nobiletin | 1.16±0.01aA | 2.49±0.11bA | 0.75±0.02aB | 2.33±0.03bA |
| Tangeretin | 0.61±0.01aA | 1.43±0.06bA | 0.45±0.01aB | 1.11±0.02bB |
| Limonin (mg per g of DW) | 1.48±0.01aA | 1.32±0.02bB | 1.21±0.01aB | 1.41±0.02bB |
[i] Data represent mean ± SE, n = 3; Small letters among the same harvest date indicate significant differences between varieties by Tukey–Kramer's Test (P < 0.05); Capital letters indicate significance by Tukey–Kramer's test (P < 0.05), compared with the same variety in the other month; PMFs represent the sum of sinensetin, nobiletin, and tangeretin; DW – dry weight
Table 3.
Characteristics of vinegar extract from Ishikunibu and ‘Kugani’ harvested in December and February
| Harvest month | December | February | ||
|---|---|---|---|---|
| Variety | Ishikunibu | Kugani | Ishikunibu | Kugani |
| Vinegar volume (mL) | 33.2±0.4aA | 35.5±1.5aA | 36.7±1.4aA | 33.5±0.7aA |
| Titratable acidity (%) | 4.70±0.1aA | 4.56±0.1aA | 4.83±0.1aA | 4.56±0.0bA |
| Ascorbic acid (μg per mL) | 69.4±15.1aA | 41.0±1.3aA | 115.2±5.2aA | 38.9±2.2bA |
| Polyphenols (μg per mL) | 185.1±2.0aA | 163.9±7.8aA | 191.7±8.9aA | 158.1±7.4aA |
| ORAC (μmol TEx per mL) | 7.1±0.1aA | 4.9±0.8aA | 5.7±0.4aA | 5.1±0.4aA |
| PMFs (mg per 100 mL) | 14.7±1.8aA | 33.4±0.2bA | 12.5±1.8aA | 29.0±0.7bB |
| Sinensetin | 1.5±0.2aA | 2.5±0.1bA | 1.2±0.2aA | 2.0±0.1bB |
| Nobiletin | 8.9±1.4aA | 20.8±0.6bA | 7.3±1.1aA | 19.2±0.8bA |
| Tangeretin | 4.3±0.5aA | 10.0±0.6bA | 4.0±0.6aA | 7.8±0.3bB |
| Limonin (mg per 100 mL) | 17.9±5.4aA | 46.4±7.4aA | 8.7±3.9aA | 28.3±5.1aA |
| Monoterpenes (IS%)y | 9.1±3.3aA | 6.5±1.1aA | 5.1±1.4aA | 7.8±1.6aA |
| β-myrcene | 0.3±0.2aA | 0.2±0.1aA | 0.1±0.1aA | 0.2±0.1aA |
| Limonene | 3.8±1.5aA | 2.2±0.5aA | 2.2±0.6aA | 2.9±0.6aA |
| γ-terpinen | 3.5±1.3aA | 2.7±0.4aA | 2.1±0.6aA | 3.3±0.7aA |
| p-cymene | 1.4±0.7aA | 1.4±0.3aA | 0.7±0.3aA | 1.5±0.4aA |
| Monoterpene alcohols (IS%)y | 1.3±0.1aA | 0.5±0.1bA | 0.6±0.2aB | 0.1±0.1bB |
| Linalool | 0.6±0.1aA | 0.1±0.1bA | 0.1±0.1aB | 0.0±0.0bA |
| Terpinen-4-ol | 0.5±0.1aA | 0.3±0.1bA | 0.3±0.1aA | 0.1±0.1aB |
| α-Terpineol | 0.3±0.1aA | 0.1±0.1bA | 0.1±0.1aB | 0.0±0.0bB |
| Sensory evaluation | ||||
| Shikuwasa aroma | 2.67±0.32a | 3.00±0.28a | 3.00±0.23a | 2.44±0.28a |
| Green smell | 4.56±0.23a | 3.67±0.39a | 3.67±0.39a | 3.44±0.23a |
| Bitterness | 4.00±0.36ab | 3.44±0.32ab | 4.33±0.28a | 3.33±0.28b |
| General flavor | 3.44±0.28a | 3.78±0.21a | 3.78±0.27a | 3.67±0.23a |
| CIELAB color space | ||||
| L* | 45.6±0.3aA | 51.6±1.1bA | 44.6±0.8aA | 48.9±0.9bA |
| a* | 0.3±0.4aA | −3.0±0.2bA | 5.9±1.3aB | −1.0±0.4bB |
| b* | 23.4±0.9aA | 26.1±1.3aA | 29.9±1.6aB | 28.4±0.3aA |
[i] Data represent mean ± SE, n = 3 (except sensory evaluation); Small letters among the same harvest date indicate significant differences between varieties (except sensory evaluation) by Tukey–Kramer's Test (P < 0.05); Capital letters indicate significance by Tukey–Kramer's test (P < 0.05), compared with the same variety in the other month (except sensory evaluation); For sensory evaluation, small letters indicate significant differences between all vinegar samples within column; x represents Trolox equivalent; PMFs represent the sum of sinensetin, nobiletin and tangeretin; y represents the peak area ratio to the internal standard of 1-hexanol; Monoterpenes represent the sum of β-myrcene, limonene, γ-terpinen, and p-cymene; Monoterpene alcohols represent the sum of linalool, terpinen-4-ol, and α-terpineol
Figure 2.
Photographs of the vinegar extracts diluted 10 times with distilled water (from left to right, the shikuwasa vinegar extracts made from Ishikunibu and ‘Kugani’ in December, Ishikunibu and ‘Kugani’ in February)