Table 4.
Volatile compounds produced by the L. lactis isolates during growth at 30 °C for 24 h in ultra-high temperature (UHT) skimmed milk (HS/GC/MS analysis). Values represent the mean ± the standard deviation of three independent experiments.
| Strains | ||||||
|---|---|---|---|---|---|---|
| Volatile Compound † | LEY6 | LEY7 | LEY8 | LEY11 | LEY12 | LEY13 |
| Acetaldehyde | 76.9 ± 7.5 a | 25.7 ± 44.5 a | 57.7 ± 52.4 a | 23.9 ± 4.3 a | 21.9 ± 3.6 a | 26.2 ± 8.6 a |
| 2-Methyl propanal | 179.1 ± 15.5 a | 123.5 ± 43.2 a | 180.0 ± 35.3 a | 121.3 ± 22.3 a | 99.8 ± 30.9 a | 131.8 ± 21.9 a |
| Methyl acetate | − b | − b | − b | 26.1 ± 7.5 a | 25.2 ± 9.4 a | 26.9 ± 2.3 a |
| 2-Methyl butanal | 72.6 ± 12.9 a | 80.1 ± 10.6 a | 61.8 ± 16.9 a | − b | − b | − b |
| 3-Methyl butanal | 877.7 ± 70.3 a | 796.1 ± 197.7 a | 797.0 ± 50.3 a | 852.8 ± 244.5 a | 588.8 ± 248.1 a | 897.9 ± 154.6 a |
| Ethanol | 396.5 ± 32.5 a | 353.5 ± 107.6 a | 340.5 ± 18.8 a | 351.5 ± 59.8 a | 315.3 ± 32.7 a | 362.6 ± 58.5 a |
| 2,2,4,6,6 PMH ‡ | − b | 95.0 ± 164.6 a | 66.4 ± 115.1 a | − b | 51.1 ± 88.5 a | 83.6 ± 144.9 a |
| Methyl butanoate | − b | − b | − b | 2.3 ± 4.0 a | 9.1 ± 8.0 a | − b |
| 2-Methyl-1-propanol | 55.6 ± 2.2 a | 51.4 ± 48.6 a | 41.4 ± 7.6 b | 30.7 ± 1.8 b | 35.7 ± 6.4 b | 31.7 ± 7.6 b |
| Methyl hexanoate | 23.9 ± 1.3 a | − b | − b | 3.6 ± 6.3 a | 2.8 ± 4.8 a | 9.6 ± 8.3 a |
| 2 or 3-Methyl-1-butanol | 322.9 ± 8.5 a | 367.6 ± 28.1 a | 298.7 ± 22.8 a | 198.4 ± 36.2 b | 213.2 ± 42.2 b | 205.0 ± 21.5 b |
| Acetoin | − b | − b | − b | − b | 2.6 ± 4.6 a | − b |
| Acetic acid | − b | − b | − b | 21.9 ± 5.7 a | 22.1 ± 3.0 a | 17.7 ± 2.0 a |
† Concentration refers to the internal standard (cyclohexanone 3.6 µg/mL), to which a value of 100 was given; ‡ 2,2,4,6,6 Pentamethyl heptane; − Not detected; different superscript letters indicate mean differences among strains, for each compound (p < 0.05).