Table 1.
Proximate composition and mineral content of roe protein isolates (RPIs) recovered from skipjack tuna roe (STR) by isoelectric solubilization and precipitation process
| FDSTR | RPI−1 | RPI−2 | RPI−3 | RPI−4 | Casein | Hb | ||
|---|---|---|---|---|---|---|---|---|
| Yield † , † (g) | 26.7 | 10.9 | 10.3 | 13.0 | 12.2 | |||
| Protein yield ‡ , ‡ (g) | 19.0 | 7.8 | 7.9 | 9.2 | 9.2 | |||
| Moisture (%) | 6.2 ± 0.9a | 5.7 ± 0.3a | 4.5 ± 0.1bc | 6.3 ± 0.1a | 4.9 ± 0.3b | 4.0 ± 0.2c | 2.0 ± 0.0d | |
| Protein (%) | 71.1 ± 0.7e | 71.4 ± 0.8e | 76.8 ± 0.3c | 70.8 ± 0.7e | 75.4 ± 0.4d | 85.5 ± 0.0b | 94.4 ± 0.4a | |
| Lipid (%) | 15.2 ± 1.3a | 15.6 ± 1.0a | 14.0 ± 2.7a | 14.7 ± 2.0a | 13.8 ± 2.5a | ND | ND | |
| Ash (%) | 7.2 ± 0.1a | 3.6 ± 0.1b | 1.8 ± 0.6c | 3.3 ± 0.4b | 2.0 ± 0.1c | ND | ND | |
| Minerals (mg/100 g) | K | 1,097.4 ± 9.0a | 18.4 ± 3.1e | 70.3 ± 0.6c | 25.8 ± 2.9e | 45.2 ± 2.1d | 912.0 ± 12.3b | 71.4 ± 3.0c |
| Na | 615.2 ± 1.4ab | 70.1 ± 0.6b | 113.9 ± 3.2b | 147.0 ± 2.1b | 166.9 ± 1.1b | 706.3 ± 10.9a | 212.6 ± 1.8b | |
| Mg | 66.9 ± 0.1a | 1.7 ± 0.1e | 7.1 ± 0.1c | 2.3 ± 0.1d | 7.6 ± 0.2b | ND | ND | |
| Zn | 39.3 ± 0.3c | 8.3 ± 0.0d | 46.5 ± 0.5b | 7.6 ± 0.1d | 51.4 ± 0.9a | ND | ND | |
| Ca | 36.3 ± 0.2b | 4.8 ± 0.1d | 15.6 ± 0.3cd | 7.8 ± 0.2d | 15.5 ± 0.2cd | 987.2 ± 17.3a | 21.2 ± 0.2c | |
| Fe | 9.2 ± 0.2de | 10.8 ± 0.2d | 16.4 ± 0.3b | 12.1 ± 0.2c | 16.4 ± 0.2b | 4.8 ± 0.0f | 250.1 ± 1.8a | |
| P | 247.9 ± 1.5a | 111.9 ± 0.6e | 115.5 ± 1.0d | 120.3 ± 1.0c | 131.5 ± 1.4b | 34.7 ± 0.4f | 29.1 ± 0.3g | |
| S | 974.3 ± 57.7b | 482.5 ± 89.5ef | 683.7 ± 83.6cd | 573.7 ± 72.1de | 782.1 ± 47.2c | 1984.1 ± 3.2a | 442.0 ± 46.2f | |
| Color values | L* | 59.2 ± 0.3a | 55.0 ± 0.2b | 52.2 ± 0.5c | 52.6 ± 0.5c | 51.9 ± 0.4c | ||
| a* | 6.8 ± 0.1a | 4.1 ± 0.0e | 5.3 ± 0.1b | 4.3 ± 0.1d | 5.1 ± 0.1c | |||
| b* | 21.2 ± 0.0a | 16.2 ± 0.2d | 17.2 ± 0.2b | 16.8 ± 0.2c | 17.3 ± 0.1b | |||
| ΔE | 43.5 ± 0.3d | 44.7 ± 0.3c | 48.0 ± 0.4a | 47.3 ± 0.4b | 48.3 ± 0.3a | |||
| Whiteness | 53.6 ± 0.3a | 52.0 ± 0.1b | 48.9 ± 0.4d | 49.6 ± 0.4c | 48.6 ± 0.3d | |||
Values are mean ± SD of triplicate determinations. Means with different letters within the same row are significantly different at p < .05 by Duncan's multiple range test.
FDSTR, freeze‐dried skipjack tuna roe; Hb, hemoglobin. ND: not determined; RPI‐1 and RPI‐2, roe protein isolate adjusted to pH 4.5 and 5.5, respectively, after alkaline solubilization at pH 11; RPI‐3 and RPI‐4, roe protein isolate adjusted to pH 4.5 and 5.5, respectively, after alkaline solubilization at pH 12.
Yield is weight (g) of each sample obtained from 100 g of raw STR.
Protein yield (g) = yield × protein (%).