The efficacy of cell-free supernatants from Lactobacillus plantarum Cs and Lactobacillus acidophilus ATCC 314 for the preservation of home-processed tomato-paste

Abstract

The unsafety concern associated with the chemical preservatives and the understanding of the preservative potential of lactic acid bacteria on varied food substances led to the present study which was aimed at the evaluation of the bio-preservative potential of L. plantarum Cs and L. acidophilus ATCC 314 on home-processed tomato paste. The test organisms were activated in glucose supplemented deMan Rogosa Sharpe broth under stationary condition at 37 °C for 36 h to produce cell-free supernatants (CFSs) which were concentrated to 50% with 5 M sucrose solution and precipitated with 4 °C acetone respectively. The treated CFSs were first exposed to chemical analysis prior to their antimicrobial sensitivity to the indicator organisms (Staphylococcus aureus, Escherichia coli, Aspergillus niger and Aspergillus flavus). The minimum inhibitory concentration (MIC) of the most active CFS was selected for shelf-life study on home-processed tomato paste at room temperature for 45days. Among the detectable amount of CFS biomolecules, a significant (P>0.05) high amount of lactic acid (6.491±0.017 mg/ml) was recovered from concentrated CFS from L. acidophilus ATCC 314 while precipitated CFS from L. plantarum Cs had the highest significant protein molecules (0.863±0.013 mg/ml). However, the concentrated CFS (cCFS) from both test organisms at 100% demonstrated the strongest antimicrobial activity to all the indicator organisms among the other two CFSs. Their inhibitory effect was greater on Staphylococcus aureus (11.9±0.10–12.85 ± 0.08 mm) than E. coli (7.57 ± 0.06–8.15±0.05 mm) and Aspergillus niger (5.94 ± 0.08–6.98 ± 0.06) than Aspergillus flavus (5.05± 0.04–5.60 ± 0.05). The L. plantarum Cs and L. acidophilus ATCC 314 cCFSs- treated tomato pastes significantly (P>0.05) extended the pastes shelf-life to 25 and 30 days respectively. However, the 5 days’ shelf-life extension of the tomato paste by L. acidophilus ATCC 314 cCFS as compared to that from L. plantarum Cs was insignificant (P>0.05). The increase in shelf-life of the home-processed tomato paste suggests the possible use of L. plantarum Cs and L. acidophilus ATCC 314 CFS as bio-preservatives in tomato processing.