Currently, there is no information on the use of starter cultures for
The objective of the present study was therefore to evaluate the technological potential of lactic acid bacteria isolated from spontaneously fermented
A total of 373 LAB isolated and identified from spontaneously fermented
Acidification properties of the LAB were measured by the change in pH with time [
The proteolytic activity of the isolates during fermentation of milk was measured by assessing the free amino groups using the o-phthaldialdehyde (OPA) method [
Strains were grown overnight at 37°C in MRS broth. A loopful of fresh culture was placed on tributyrin agar [
The screening of the isolates for EPSs production was carried out according to the method described by Guiraud [
The positive isolates were confirmed growing them on MRS sucrose broth and incubating them at 30°C for 24 h. A volume of 1.5 mL of the 24 h culture was centrifuged at 5000 g for 10 min (4°C) and 1 mL of the supernatant was put in a glass tube and an equal volume of ethanol 95% was added. An opaque link formed at the interface of the tube indicates the presence of EPSs. Samples were centrifuged 2500 ×g for 20 min and the pellets were dried at 100°C. The total carbohydrate content of the EPS was determined using the phenol-sulfuric acid procedure of Dubois et al. [
Four (4) strains of LAB were selected and used as starter cultures during the fermentation of milk to produce
The LAB strains to be used as inocula were prepared by transferring a loopful of an overnight culture from MRS agar into 10 mL MRS broth and incubated at 35°C for 24 h. One hundred microliters of the 24 h old culture was transferred into 10 mL MRS broth and incubated at 35°C for 16 h (overnight). Subsequently, cells were harvested by centrifugation at 5000 g for 10 min (4°C); washed three times with 20 mL sterile diluent (Merck), pH 7.2 ± 0.2; and finally suspended in 10 mL of sterile diluent, and these served as the isolate inocula. Flasks containing 500 mL of fresh milk pasteurized at 60°C for 30 min in a water bath were inoculated in duplicate at 35°C for 24 h. Single and combined starter cultures used for the fermentation of milk to produce
Starter cultures used for
Type of fermentation | Starter cultures | Codes |
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Single starters cultures |
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LF-22-16 |
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LP-8-2 | |
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LH-22-7 | |
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LM-14-11 | |
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Combined starter cultures |
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LF-22-16 + LP-8-2 |
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LF-22-16 + LH-22-7 | |
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LF-22-16 + LM-14-11 | |
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LP-8-2 + LH-22-7 | |
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LP-22-7 + LM-14-11 | |
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LH-22-7 + LM-14-11 | |
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No starter culture was added | Spontaneously fermented | SP |
The pH of fermenting
All analyses were carried out in triplicate. Data obtained were subjected to one-way analysis of variance (ANOVA) and means were separated by Tukey’s family error rate multiple comparison test (
Rapid acidification is a priority for development of starter cultures for fermented milk products. The acidification properties of predominant LAB isolated from spontaneously fermented
Acidification properties of predominant LAB species isolated from
In general most of the strains tested showed proteolytic activities to varying degrees (Figure
Pattern of proteolytic activities of predominant LAB isolated from
Lipolytic activities were recognized by the presence of a clear halo in the tributyrin agar plates. Out of the 174 strains of
Lipolytic activities of predominant LAB isolated from
LAB species | Zones of inhibition | ||
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No inhibition | 1–3 cm | >3–5 cm | |
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56 | 100 | 18 |
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4 | 28 | 12 |
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9 | 24 | 7 |
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9 | 24 | 8 |
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3 | 21 | 11 |
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7 | 30 | 2 |
Very few studies on lactic acid bacterial lipases have been carried out. Tsakalidou et al. [
As shown in Figure
Exopolysaccharides activities of predominant LAB isolated from
The antimicrobial properties of predominant LAB isolated from
Antimicrobial activities of predominant LAB against selected pathogenic microorganisms.
Number of LAB tested | *Range of inhibition of pathogens | |||||
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8 (+) | 4 (+) | 6 (+) | 2 (+) | 6 (+) | 4 (+) |
2 (++) | 0 (++) | 2 (++) | 0 (++) | 2 (++) | 0 (++) | |
0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | |
164 (ND) | 170 (ND) | 166 (ND) | 172 (ND) | 166 (ND) | 170 (ND) | |
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18 (+) | 4 (+) | 6 (+) | 2 (+) | 6 (+) | 2 (+) |
2 (++) | 2 (++) | 4 (++) | 2 (++) | 2 (++) | 2 (++) | |
0 (+++) | 0 (+++) | 2 (+++) | 0 (+++) | 2 (+++) | 0 (+++) | |
24 (ND) | 38 (ND) | 32 (ND) | 40 (ND) | 34 (ND) | 40 (ND) | |
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6 (+) | 6 (+) | 6 (+) | 8 (+) | 8 (+) | 6 (+) |
4 (++) | 4 (++) | 6 (++) | 4 (++) | 2 (++) | 6 (++) | |
2 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | 2 (+++) | 0 (+++) | |
28 (ND) | 30 (ND) | 28 (ND) | 28 (ND) | 28 (ND) | 28 (ND) | |
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4 (+) | 5 (+) | 4 (+) | 6 (+) | 4 (+) | 3 (+) |
1 (++) | 0 (++) | 0 (++) | 0 (++) | 3 (++) | 2 (++) | |
0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | |
36 (ND) | 36 (ND) | 37 (ND) | 35 (ND) | 34 (ND) | 36 (ND) | |
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6 (+) | 11 (+) | 4 (+) | 6 (+) | 10 (+) | 6 (+) |
3 (++) | 0 (++) | 5 (++) | 0 (++) | 3 (++) | 4 (++) | |
0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | |
30 (ND) | 28 (ND) | 26 (ND) | 33 (ND) | 26 (ND) | 29 (ND) | |
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5 (+) | 6 (+) | 2 (+) | 4 (+) | 4 (+) | 2 (+) |
0 (++) | 3 (++) | 2 (++) | 3 (++) | 1 (++) | 3 (++) | |
0 (+++) | 0 (+++) | 3 (+++) | 0 (+++) | 0 (+++) | 0 (+++) | |
30 (ND) | 26 (ND) | 28 (ND) | 28 (ND) | 30 (ND) | 30 (ND) |
pH of fermenting milk with different starter cultures. Spontaneously fermented (Sp),
The rates of acidification of
The rate of acid development is a critical factor in milk fermentation. The rapid acidification of the raw material prevents growth of undesirable microorganisms and is also essential for aroma, texture, and flavor of the end-product.
Table
Amino acids profile (mg/L) of
Amino acids | Starter cultures | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Sp | Lf | Lp | Lh | Lm | Lf + Lp | Lf + Lh | Lf + Lm | Lp + Lh | Lp + Lm | Lh + Lm | |
Lysine |
2.53 ± 0.02h | 4.60 ± 0.06a | 3.80 ± 0.02b | 4.65 ± 0.02a | 1.91 ± 0.01f | 2.43 ± 0.01e | 3.85 ± 0.01b | 2.63 ± 0.02d | 3.53 ± 0.06c | 2.65 ± 0.02d | 2.12 ± 0.01g |
Argentine | 3.15 ± 0.01a | 6.88 ± 0.09b | 3.44 ± 0.01c | 4.32 ± 0.01d | 1.93 ± 0.01e | 4.94 ± 0.02f | 3.51 ± 0.01g | ND | 3.63 ± 0.01h | 1.55 ± 0.01i | ND |
Histidine |
2.93 ± 0.06a | 3.85 ± 0.09d | 4.11 ± 0.01e | 3.83 ± 0.03d | 3.57 ± 0.03c | 3.00 ± 0.00b | 2.96 ± 0.01b | ND | 3.97 ± 0.06f | 3.10 ± 0.10b | ND |
Methionine |
1.75 ± 0.02a | 4.58 ± 0.02e | 3.99 ± 0.01f | 2.13 ± 0.02c | 1.88 ± 0.01b | 4.88 ± 0.01g | 5.73 ± 0.02h | 1.88 ± 0.01b | 6.77 ± 0.01i | 2.24 ± 0.02d | 2.24 ± 0.02d |
Isoleucine |
2.99 ± 0.01a | 5.80 ± 0.11b | 2.11 ± 0.01c | 6.51 ± 0.02e | 3.49 ± 0.01f | 4.22 ± 0.01g | 2.86 ± 0.01a | 2.95 ± 0.00a | 7.10 ± 0.10h | 1.16 ± 0.01i | 2.57 ± 0.02j |
Tryptophan | 3.13 ± 0.01a | 2.34 ± 0.02b | 3.42 ± 0.02c | 3.95 ± 0.01d | 2.01 ± 0.01e | 4.86 ± 0.01f | 2.51 ± 0.01g | 3.66 ± 0.01h | 5.27 ± 0.06i | ND | ND |
Threonine |
3.33 ± 0.02a | 3.21 ± 0.01b | 2.82 ± 0.01c | 4.07 ± 0.15d | ND | 4.53 ± 0.01e | 2.52 ± 0.01f | 3.32 ± 0.01a | ND | 1.46 ± 0.01g | ND |
Proline | 2.63 ± 0.01a | 2.68 ± 0.02a | 3.77 ± 0.01c | 4.51 ± 0.02d | 0.80 ± 0.01e | 4.67 ± 0.01b | 3.44 ± 0.02f | 4.64 ± 0.01b | 4.75 ± 0.04b | 1.90 ± 0.02g | 2.79 ± 0.02h |
Glutamine | 4.02 ± 0.01a | 4.22 ± 0.01g | 2.68 ± 0.00d | 7.82 ± 0.02i | 0.98 ± 0.01b | 3.80 ± 0.01f | 3.77 ± 0.02f | 2.68 ± 0.01d | 5.47 ± 0.12h | 3.14 ± 0.02e | 1.97 ± 0.01c |
Asparagine | 3.21 ± 0.01f | 2.45 ± 0.01c | 2.55 ± 0.01d | 4.70 ± 0.01g | 1.58 ± 0.02a | 2.95 ± 0.01e | 3.22 ± 0.01f | 1.53 ± 0.01a | 6.41 ± 0.01h | 2.61 ± 0.01d | 1.99 ± 0.01b |
Glutamic acid | 3.14 ± 0.01f | 2.65 ± 0.02d | 3.24 ± 0.05f | 4.50 ± 0.01g | 2.92 ± 0.02e | ND | 2.45 ± 0.02c | 2.09 ± 0.01a | 7.10 ± 0.01h | 3.18 ± 0.01f | 2.39 ± 0.02c |
Valine |
2.81 ± 0.02c | ND | 4.11 ± 0.01e | 4.21 ± 0.01f | 4.87 ± 0.02g | 2.47 ± 0.01b | 2.46 ± 0.02b | 2.96 ± 0.01d | ND | 2.16 ± 0.01a | 2.95 ± 0.01d |
Phenylamine |
1.18 ± 0.01a | 3.83 ± 0.02e | 4.07 ± 0.16f | 3.62 ± 0.01d | ND | 4.74 ± 0.01h | 1.94 ± 0.02b | ND | 4.45 ± 0.01g | 3.96 ± 0.01f | 2.92 ± 0.02c |
Aspartic acid | 1.25 ± 0.01a | 3.54 ± 0.06d | 3.71 ± 0.02e | 4.07 ± 0.01f | ND | ND | 2.81 ± 0.02b | 3.27 ± 0.01c | 4.45 ± 0.01g | ND | ND |
Serine | ND | ND | 2.66 ± 0.02a | 4.74 ± 0.01c | ND | ND | 6.33 ± 0.01b | 3.28 ± 0.01c | 5.32 ± 0.01g | ND | ND |
Glycine | 2.14 ± 0.02b | 4.23 ± 0.01h | 3.24 ± 0.02e | 3.22 ± 0.01e | 2.51 ± 0.01c | ND | 4.07 ± 0.01g | 3.42 ± 0.01f | 5.57 ± 0.01i | 3.12 ± 0.01d | 1.77 ± 0.02a |
Tyrosine | 1.16 ± 0.01a | 2.78 ± 0.02d | 5.34 ± 0.02h | 3.03 ± 0.01e | ND | 3.70 ± 0.01f | 2.71 ± 0.01d | 4.22 ± 0.00g | 6.00 ± 0.10i | 2.16 ± 0.01c | 1.82 ± 0.02b |
Alanine | 1.44 ± 0.01a | 3.75 ± 0.05h | 7.96 ± 0.01j | 2.63 ± 0.02e | 2.47 ± 0.01d | 3.70 ± 0.01h | 3.10 ± 0.00g | 2.43 ± 0.01c | 4.32 ± 0.01i | 2.77 ± 0.02c | 2.15 ± 0.02b |
Cystine | 2.10 ± 0.01b | 2.81 ± 0.01e | 2.70 ± 0.01d | 5.60 ± 0.01g | ND | ND | 6.18 ± 0.02h | 2.41 ± 0.01c | 4.51 ± 0.06f | 2.65 ± 0.02d | 1.59 ± 0.01a |
Leucine |
1.25 ± 0.01a | 2.61 ± 0.02b | 3.92 ± 0.01c | 5.98 ± 0.01d | 0.76 ± 0.01e | 5.77 ± 0.01f | 4.56 ± 0.01g | 4.86 ± 0.02h | 6.21 ± 0.01i | 1.76 ± 0.01j | 1.19 ± 0.01k |
Consumer sensory analysis showed varying degrees of acceptability for
Mean score of sensory attributes of
Starter cultures | Taste | Odour | Colour/appearance | Texture | Overall acceptability |
---|---|---|---|---|---|
Sp (control) | 6.53 ± 0.06d | 5.00 ± 0.10a | 6.40 ± 0.10b | 6.53 ± 0.06b | 6.45 ± 0.06a |
Lf | 6.07 ± 0.15b | 6.53 ± 0.06d | 7.13 ± 0.06c | 7.27 ± 0.06c,d | 7.17 ± 0.12b |
Lp | 7.53 ± 0.06g | 7.90 ± 0.10f | 8.03 ± 0.15e | 8.50 ± 0.20e | 7.20 ± 0.00b |
Lh | 6.40 ± 0.00c | 8.43 ± 0.15g | 7.43 ± 0.15d | 8.20 ± 0.20e | 8.00 ± 0.20e |
Lm | 5.00 ± 0.17a | 6.33 ± 0.06c | 6.53 ± 0.06b | 8.43 ± 0.15e | 7.40 ± 0.17b,d |
Lf + Lp | 8.03 ± 0.15h | 8.50 ± 0.20g | 7.13 ± 0.06c | 7.13 ± 0.12c | 8.43 ± 0.15f |
Lf + Lh | 7.17 ± 0.06e | 8.43 ± 0.06g | 8.03 ± 0.06e | 8.43 ± 0.06e | 8.17 ± 0.12e,f |
Lf + Lm | 6.20 ± 0.10b | 6.10 ± 0.17b | 7.27 ± 0.15c,d | 7.43 ± 0.15d | 7.43 ± 0.06d |
Lp + Lh | 7.03 ± 0.16e | 8.63 ± 0.06g | 7.87 ± 0.15e | 8.50 ± 0.20e | 7.70 ± 0.10d |
Lp + Lm | 7.30 ± 0.00f | 5.17 ± 0.06a | 6.57 ± 0.15b | 8.30 ± 0.10e | 7.50 ± 0.26d |
Lh + Lm | 7.50 ± 0.20g | 7.20 ± 0.10e | 5.53 ± 0.06a | 6.23 ± 0.15a | 6.50 ± 0.20a |
Values are means of two experiments, ±: standard deviation. Values in the same column with different letters differ significantly from each other (
Lactic acid bacteria isolated from Ghanaian traditional fermented milk product (
The authors declare that there is no conflict of interests regarding the publication of this paper.
This study is sponsored by the DANIDA-ENRECA project on capability building in research and quality assurance in traditional fermented foods of West Africa.