Table 2.
Major differences in concentration (μM) among phospholipid (PC, SM, PE, PS, PI, and PA) and lysophospholipid (LPC, LPE, LPS, and LPI) species present in bovine raw milk samples (M1, M2, and M3) that were either cold-stored at 6° C for 7 days (C7) or additionally flushed with N2 (N7).
| Phospholipid classes and species | C7 (n = 3) μM | N7 (n = 3) μM | C7-N7 μMa | PROPOSED PLases or SMases | |
|---|---|---|---|---|---|
| Lipidomics data | Microbiological data | ||||
| PC class | |||||
| Major LPCs | |||||
| 14:0 | 0.23 | 0.04 | +0.18 | PLA, PLB | |
| 16:0 | 0.76 | 0.27 | +0.49 | PLA, PLB | |
| 18:1 | 1.98 | 0.18 | +1.80 | PLA, PLB | |
| 18:2 | 0.40 | 0.04 | +0.36 | PLA, PLB | |
| Major PCs | 27.21 | 55.60 | |||
| 30:0 | 4.77 | 6.34 | -1.57 | PLA, PLB | PLCd |
| 32:0 | 4.63 | 6.57 | -1.93 | PLA, PLB | PLC |
| 34:1 | 8.82 | 17.59 | -8.77 | PLA, PLB | PLC |
| 34:2 | 2.20 | 5.44 | -3.24 | PLA, PLB | PLC |
| 36:1 | 1.71 | 4.32 | -2.61 | PLA, PLB | PLC |
| 36:2 | 3.73 | 10.75 | -7.02 | PLA, PLB | PLC |
| 36:3 | 1.35 | 4.59 | -3.24 | PLA, PLB | PLC |
| All LPCs+PCsb | 36.13 | 70.06 | -33.93 (-48%c) | PLA, PLB | PLC |
| SM class | |||||
| LSMs | N.D.e | N.D. | – | ||
| Cer-1-P | N.D.e | N.D. | – | ||
| Major SMs | 26.67 | 35.85 | |||
| 16:0 | 5.13 | 7.69 | -2.56 | SMase C | |
| 20:0 | 2.61 | 2.70 | -0.09 | SMase C | |
| 21:0 | 3.82 | 4.68 | -0.86 | SMase C | |
| 22:0 | 6.61 | 9.22 | -2.61 | SMase C | |
| 23:0 | 4.81 | 6.79 | -1.98 | SMase C | |
| 24:0 | 3.69 | 4.77 | -1.08 | SMase C | |
| All SMsb | 34.42 | 47.02 | -12.60 (-27%c) | SMase C | |
| PE class | |||||
| Major LPEs | |||||
| 18:1 | 7.74 | 1.17 | +6.57 | PLA, PLB | |
| 18:2 | 2.34 | 0.40 | +1.93 | PLA, PLB | |
| Major PEs | 34.59 | 53.97 | |||
| 34:1 | 4.41 | 4.07 | +0.34 | PLA, PLB | PLC |
| 34:2 | 10.03 | 4.59 | +5.44 | PLA, PLB | PLC |
| 36:1 | 3.01 | 4.77 | -1.75 | PLA, PLB | PLC |
| 36:2 | 13.05 | 29.79 | -16.74 | PLA, PLB | PLC |
| 36:3 | 4.09 | 10.75 | -6.66 | PLA, PLB | PLC |
| All LPEs+PEsb | 55.26 | 67.27 | -12.01 (-18%c) | PLA, PLB | PLC |
| PS class | |||||
| Major LPSs | |||||
| 18:1 | 2.02 | 0.40 | +1.62 | PLA, PLB | |
| 18:2 | 0.63 | 0.22 | +0.40 | PLA, PLB | |
| Major PSs | 9.94 | 18.80 | |||
| 36:1 | 5.89 | 10.21 | -4.32 | PLA, PLB | |
| 36:2 | 4.05 | 8.59 | -4.54 | PLA, PLB | |
| All LPSs+PSsb | 17.77 | 27.18 | -9.40 (-35%c) | PLA, PLB | |
| PI class | |||||
| Major LPIs | |||||
| 16:0 | 0.54 | 0.54 | +0.00 | PLA, PLB | |
| 18:0 | 0.67 | 0.27 | +0.40 | PLA, PLB | |
| Major PIs | 8.59 | 12.82 | |||
| 34:1 | 2.84 | 2.11 | +0.72 | PLA, PLB | |
| 36:1 | 3.01 | 7.02 | -4.00 | PLA, PLB | |
| 36:2 | 2.74 | 3.69 | -0.94 | PLA, PLB | |
| All LPIs+PIsb | 21.69 | 21.87 | -0.18 (-1%c) | PLA, PLB | |
| PA class | |||||
| LPAs | N.D.e | N.D. | – | ||
| Major PAs | 6.74 | 2.27 | |||
| 32:0 | 1.53 | 0.31 | +1.21 | PLD | |
| 32:1 | 1.21 | 0.85 | +0.36 | PLD | |
| 34:0 | 0.72 | 0.22 | +0.49 | PLD | |
| 36:1 | 0.13 | 0.40 | -0.27 | PLD | |
| 36:2 | 3.15 | 0.49 | +2.65 | PLD | |
| All PAsb | 6.79 | 2.29 | +4.50 | PLD | |
| Summary: | |||||
| LPLs | 17.31 | 3.53 | +13.78 | PLA, PLB | |
| PLs | 154.75 | 232.16 | -77.41 | SMase C | PLCd |
| LPLs + PLs | 172.06 | 235.69 | -63.63 (-27%)c | PLA, PLB, PLD, SMase C | PLC |
| PAs | 6.79 | 2.29 | +4.50 | PLD | |
aNegative versus positive values correspond to decrease versus increase of phospholipid concentrations in μM. b“All” refers to the total phospholipids and lysophospholipids recorded for the considered phospholipid class. cThe difference between C7 and N7 is expressed as %. dA PLC activity is proposed for PCs and PEs considering that the PC and PE classes are dominant among egg yolk phospholipids (Zhao et al., 2011); egg yolk agar was used to enumerate PLa+ colonies (see Table 1). eN.D., not detected; LSMs, lysosphingomyelins; Cer-1-P, Ceramide-1-Phosphate; LPA, lysophosphatidic acid. The PLases (PLA, PLB, PLC, and PLD) and SMases (SMase C) activities, which could explain the recorded concentration differences, based on the lipidomics and microbiological data, are also indicated.