Table 1.
(a) Proteolytic activity determined by Anson’s method and lactate, acetate, diacetyl and lactose concentrations after overnight growth of single strains of the lactic acid bacteria (LAB) consortium in skimmed milk. (b) pH values and lactic acid (g/L) of the culture supernatants of single strains of the LAB consortium at 0, 6, 24 and 48 h of cultivation in skimmed milk with or without NaCl addition in concentrations of 2, 4 and 6% (w/v), as well as LAB counts expressed as the difference of logarithmic values during cultivation (Δlog CFU/mL).
| (a) | |||||||||||
| LAB Strain | Proteolytic Activity (U/mL) | Acetate (mg/mL) | Lactate (mg/mL) | Diacetyl (mg/mL) | Lactose (mg/mL) | ||||||
| L. plantarum D13 | 1.03 ± 0.32 b | 2.795 ± 0.025 a | 4.9 ± 0 c | n.d. * | 51 ± 0 a | ||||||
| L. brevis D6 | 1.22 ± 0.18 b | 2.09 ± 0.16 c | 3.7 ± 0 d | n.d. | 51.0 ± 1.0 a | ||||||
| L. fermentum D12 | 0.79 ± 0.36 b | 2.310 ± 0.010 b | 5.850 ± 0.050 b | n.d. | 47.50 ± 0.50 b | ||||||
| E. faecium ZGZA7-10 ** | 3.52 ± 0.20 a | 1.420 ± 0.040 d | 7.150 ± 0.050 a | n.d. | 46.50 ± 0.50 b | ||||||
| (b) | |||||||||||
| Incubation Time | pH | Lactic Acid (g/L) | Δlog CFU/mL | ||||||||
| 0 h | 6 h | 24 h | 48 h | 0 h | 6 h | 24 h | 48 h | 6 h | 24 h | 48 h | |
| L. plantarum D13 | |||||||||||
| Skimmed milk | 6.58 ± 0.17 | 6.43 ± 0.20 | 5.43 ± 0.43 | 4.60 ± 0.67 | n.d. | 1.20 ± 1.04 | 3.30 ± 1.37 | 6.3 ± 3.1 | 0.04 ± 0.02 | 0.39 ± 0.35 | 0.080 ± 0.300 |
| 2% NaCl | 6.37 ± 0.16 | 6.25 ± 0.22 | 6.01 ± 0.31 | 5.11 ± 0.68 | n.d. | 1.20 ± 0.26 | 1.80 ± 0.90 | 4.2 ± 2.1 | 0.20 ± 0.06 | 0.28 ± 0.16 | −0.13 ± 0.24 |
| 4% NaCl | 6.36 ± 0.25 | 6.21 ± 0.24 | 6.01 ± 0.21 | 5.12 ± 0.48 | n.d. | 1.20 ± 0.26 | 1.65 ± 0.69 | 4.2 ± 2.1 | 0.31 ± 0.04 | 0.330 ± 0.090 | −0.10 ± 0.25 |
| 6% NaCl | 6.31 ± 0.28 | 6.15 ± 0.21 | 6.010 ± 0.070 | 5.61 ± 0.22 | n.d. | 1.05 ± 0.26 | 1.35 ± 0.45 | 3.0 ± 1.8 | 0.12 ± 0.12 | −0.86 ± 0.23 | −0.940 ± 0.040 |
| L. brevis D6 | |||||||||||
| Skimmed milk | 6.57 ± 0.12 | 6.35 ± 0.21 | 5.87 ± 0.57 | 4.48 ± 0.30 | n.d. | 1.2 ± 1.0 | 3.0 ± 2.8 | 5.7 ± 3.4 | 0.100 ± 0.070 | 0.14 ± 0.22 | 0.610 ± 0.050 |
| 2% NaCl | 6.42 ± 0.20 | 6.28 ± 0.25 | 5.99 ± 0.34 | 5.2 ± 1.1 | n.d. | 1.2 ± 1.0 | 1.6 ± 1.4 | 4.2 ± 2.9 | 0.020 ± 0.090 | −0.100 ± 0.020 | −0.610 ± 0.060 |
| 4% NaCl | 6.38 ± 0.24 | 6.27 ± 0.29 | 6.08 ± 0.27 | 5.38 ± 0.90 | n.d. | 1.05 ± 0.94 | 1.4 ± 1.2 | 3.9 ± 2.6 | 0.020 ± 0.030 | −0.37 ± 0.15 | −0.75 ± 0.24 |
| 6% NaCl | 6.31 ± 0.24 | 6.22 ± 0.29 | 6.04 ± 0.20 | 5.60 ± 0.55 | n.d. | 1.05 ± 0.94 | 1.4 ± 1.2 | 3.3 ± 2.1 | −0.09 ± 0.10 | −0.13 ± 0.06 | −0.81 ± 0.18 |
| L. fermentum D12 | |||||||||||
| Skimmed milk | 6.62 ± 0.12 | 6.450 ± 0.080 | 5.23 ± 0.67 | 4.32 ± 0.31 | n.d. | 0.75 ± 0.69 | 2.70 ± 0.90 | 5.0 ± 3.0 | 0.01 ± 0.12 | 0.200 ± 0.090 | 0.57 ± 0.19 |
| 2% NaCl | 6.44 ± 0.20 | 6.33 ± 0.19 | 5.65 ± 0.43 | 4.24 ± 0.39 | n.d. | 1.20 ± 0.26 | 2.25 ± 0.45 | 4.5 ± 1.6 | −0.13 ± 0.18 | 0.40 ± 0.30 | 0.43 ± 0.25 |
| 4% NaCl | 6.39 ± 0.21 | 6.29 ± 0.20 | 5.78 ± 0.28 | 4.77 ± 0.35 | n.d. | 0.75 ± 0.69 | 1.50 ± 0.52 | 4.2 ± 2.1 | −0.03 ± 0.19 | 0.26 ± 0.33 | 0.36 ± 0.19 |
| 6% NaCl | 6.31 ± 0.20 | 6.23 ± 0.20 | 6.020 ± 0.080 | 5.31 ± 0.12 | n.d. | 1.35 ± 0.45 | 1.65 ± 0.69 | 2.70 ± 0.90 | 0.01 ± 0.14 | −0.44 ± 0.32 | −0.44 ± 0.18 |
| E. faecium ZGZA7-10 | |||||||||||
| Skimmed milk | 6.67 ± 0.08 | 6.21 ± 0.23 | 5.13 ± 0.34 | 4.63 ± 0.15 | n.d. | 1.50 ± 0.52 | 3.2 ± 1.2 | 5.1 ± 2.1 | 0.27 ± 0.20 | 0.520 ± 0.050 | 0.72 ± 0.31 |
| 2% NaCl | 6.45 ± 0.13 | 6.14 ± 0.24 | 5.15 ± 0.30 | 4.730 ± 0.080 | n.d. | 1.65 ± 0.26 | 3.3 ± 1.4 | 5.1 ± 2.3 | 0.29 ± 0.24 | 0.37 ± 0.27 | 0.41 ± 0.36 |
| 4% NaCl | 6.44 ± 0.22 | 6.21 ± 0.19 | 5.43 ± 0.36 | 5.03 ± 0.14 | n.d. | 1.05 ± 0.94 | 3.0 ± 1.4 | 4.5 ± 1.6 | 0.20 ± 0.30 | 0.28 ± 0.30 | 0.47 ± 0.18 |
| 6% NaCl | 6.40 ± 0.22 | 6.22 ± 0.17 | 5.61 ± 0.22 | 5.40 ± 0.12 | n.d. | 1.2 ± 1.0 | 2.4 ± 1.4 | 3.0 ± 1.4 | −0.24 ± 0.15 | 0.16 ± 0.26 | −0.15 ± 0.34 |
* n.d.—not detected; LOD of the diacetyl by GC-FID is 100 ppm. ** Haemolytic activity on Columbia Blood Agar (Oxoid LTD, Basingstoke, UK) with 5% sheep blood was not detected. Values are mean ± standard deviations of results from three separate evaluations. a,b,c,d Values in the same column having different letters in superscript differ significantly (p < 0.1).