Table 2.
Major aroma-related compounds (μg/kg of cheese) detected in Feta-type cheeses during refrigerated storage (30th day of storage at 4 °C) by solid-phase microextraction (SPME) GC-MS technique.
| Compound | Identification Methods α | KI β | C1 * | C2 * | C3 * | C4 * | C5 * |
|---|---|---|---|---|---|---|---|
| Esters | |||||||
| Ethyl butanoate | MS, KI | 1041 | 1.07 ± 0.03 a | 0.17 ± 0.02 b | 0.26 ± 0.02 c | 0.10 ± 0.03 b | 0.19 ± 0.05 bc |
| Ethyl hexanoate | MS, KI | 1251 | 0.00 ± 0.00 a | 0.14 ± 0.03 b | 0.11 ± 0.02 b | 2.60 ± 0.04 c | 2.16 ± 0.04 d |
| Hexyl acetate | MS, KI | 1284 | 0.00 ± 0.00 a | 0.00 ± 0.00 a | 0.00 ± 0.00 a | 0.44 ± 0.58 a | 0.08 ± 0.02 a |
| Methyl octanoate | MS, KI | 1380 | 0.00 ± 0.00 a | 1.14 ± 0.02 b | 1.36 ± 0.02 c | 1.26 ± 0.03 d | 1.04 ± 0.04 e |
| Ethyl octanoate | MS, KI | 1421 | 1.06 ± 0.01 a | 5.24 ± 0.05 b | 6.00 ± 0.05 c | 6.72 ± 0.02 d | 6.45 ± 0.04 e |
| Ethyl decanoate | MS, KI | 1634 | 8.84 ± 0.05 a | 16.70 ± 0.60 b | 12.54 ± 0.05 c | 26.15 ± 0.05 d | 20.25 ± 0.05 e |
| 2-Phenylethyl acetate | MS, KI | 1830 | 1.35 ± 0.03 a | 3.03 ± 0.02 b | 4.15 ± 0.05 c | 3.07 ± 0.07 b | 2.23 ± 0.04 d |
| Ethyl dodecanoate | MS, KI | 1848 | 7.15 ± 0.06 a | 11.15 ± 0.09 b | 10.48 ± 0.03 c | 0.00 ± 0.00 d | 0.00 ± 0.00 d |
| Free Fatty acids | |||||||
| Butanoic acid (C4:0) | MS, KI | 1642 | 76.16 ± 0.06 a | 87.14 ± 0.11 b | 79.08 ± 1.85 c | 68.74 ± 0.27 d | 87.46 ± 0.49 b |
| Hexanoic acid (C6:0) | MS, KI | 1851 | 121.33 ± 11.50 a | 385.73 ± 5.56 b | 273.63 ± 3.26 c | 391.97 ± 3.78 b | 385.83 ± 2.44 b |
| Octanoic acid (C8:0) | MS, KI | 2064 | 70.73 ± 5.40 a | 187.10 ± 6.16 b | 167.33 ± 3.58 c | 205.00 ± 6.52 d | 192.40 ± 3.12 bd |
| Decanoic acid (C10:0) | MS, KI | 2336 | 189.13 ± 3.65 a | 267.70 ± 2.72 b | 243.23 ± 1.36 c | 314.00 ± 4.33 d | 239.20 ± 8.86 c |
| Dodecanoic acid (C12:0) | MS, KI | 2485 | 67.57 ± 5.27 a | 79.54 ± 2.75 b | 78.93 ± 5.42 ab | 88.15 ± 5.51 b | 87.69 ± 2.01 b |
| Alcohols | |||||||
| ethanol | MS, KI | 932 | >10.000 | " | " | " | " |
| 3-Methyl-1-butanol | MS, KI | 1216 | 0.00 ± 0.00 a | 4.82 ± 0.30 b | 4.22 ± 0.06 c | 6.18 ± 0.03 d | 5.25 ± 0.10 e |
| 1-Hexanol | MS, KI | 1363 | 1.01 ± 0.04 a | 0.00 ± 0.00 b | 0.00 ± 0.00 b | 0.00 ± 0.00 b | 0.00 ± 0.00 b |
| 1-octen-3-ol | MS, KI | 1457 | 0.00 ± 0.00 a | 0.18 ± 0.07 a | 0.50 ± 0.57 b | 0.00 ± 0.00 a | 0.00 ± 0.00 a |
| 1-Octanol | MS, KI | 1555 | 0.00 ± 0.00 a | 1.25 ± 0.05 b | 1.11 ± 0.03 b | 3.17 ± 0.10 c | 3.11 ± 0.19 c |
| 2,3 butanediol | MS, KI | 1569 | 1.04 ± 0.04 a | 55.37 ± 93.21 a | 1.67 ± 0.05 a | 4.45 ± 2.92 a | 4.07 ± 0.05 a |
| Phenyl ethanol | MS, KI | 1932 | 18.40 ± 0.54 a | 7.16 ± 0.53 b | 10.03 ± 0.14 c | 8.07 ± 0.05 b | 12.29 ± 0.48 d |
| Carbonyl compou0s | |||||||
| propanal | MS | <800 | 0.11 ± 0.02 a | 0.00 ± 0.00 b | 0.00 ± 0.00 b | 0.00 ± 0.00 b | 0.00 ± 0.00 b |
| hexanal | MS, KI | 1088 | 0.00 ± 0.00 a | 0.00 ± 0.00 a | 0.00 ± 0.00 a | 0.12 ± 0.06 b | 0.00 ± 0.00 a |
| octanal | MS, KI | 1301 | 0.00 ± 0.00 a | 0.14 ± 0.01 b | 0.26 ± 0.05 c | 0.18 ± 0.01 b | 0.73 ± 0.04 d |
| 3-hydroxy,2-butanone | MS, KI | 1310 | 0.00 ± 0.00 a | 2.27 ± 0.06 b | 2.67 ± 0.04 c | 1.25 ± 0.04 d | 3.13 ± 0.09 e |
| Nonanal | MS, KI | 1395 | 1.75 ± 0.03 a | 6.15 ± 0.12 b | 6.77 ± 0.24 b | 8.56 ± 0.57 c | 7.57 ± 0.02 d |
| Benzaldehyde | MS, KI | 1528 | 2.15 ± 0.12 a | 0.81 ± 0.01 b | 1.22 ± 0.06 c | 0.15 ± 0.04 d | 2.14 ± 0.07 a |
| Lactones | |||||||
| δ-decalactone | MS, KI | 2209 | 1.05 ± 0.04 a | 12.16 ± 0.06 b | 12.84 ± 0.61 bc | 15.46 ± 1.53 c | 11.91 ± 1.88 b |
| γ- dodecalactone | MS, KI | 2388 | 0.00 ± 0.00 a | 0.00 ± 0.00 a | 0.00 ± 0.00 a | 3.15 ± 0.04 b | 2.82 ± 0.57 b |
| δ-dodecalactone | MS, KI | 2437 | 3.05 ± 0.05 a | 10.14 ± 0.12 b | 8.07 ± 0.65 c | 10.73 ± 1.17 b | 10.12 ± 0.06 b |
a Methods of identification: KI = tentative identification by Kovats retention index, MS = tentative identification by mass spectra obtained from NIST107, NIST21, and SZTERP libraries [CLASS 5000 software of GC-17A/QP-5050A (GC-MS); Shimadzu Corp., Kyoto, Japan]. β KI = Kovats retention index in accordance with the literature [9,10,12,39]. * C1–commercial Feta cheese manufactured with rennin enzyme, C2–Feta-type cheese manufacture with free starter culture added prior rennin enzyme, C3–Feta-type cheese manufacture with immobilized starter culture added prior rennin enzyme, C4–Feta-type cheese manufacture with free starter culture added after rennin enzyme, C5–Feta-type cheese manufacture with immobilized starter culture added after rennin enzyme. a–e Similar superscript letters in each row indicates no difference between the means of various compounds for samples C1 to C5 (ANOVA with Tukey’s HSD post hoc application at 95% confidence level).