Nutritional Quality and Shelf Life of Processed Tomato Juice and Paste Using Rosmarinus officinalis Essential Oil Combined with Low Heat Treatment in Challenged Conditions with Bacillus cereus Spores

Aims: This experiment was done to investigate the effect of adding Rosmarinus officinalis essential oil (REO) in tomato juice and paste during processing in condition of reduced thermal treatment on nutritional qualities and evaluate their postharvest shelf life under Bacillus cereus spore contamination.

Place and Duration of Study: Laboratory of Microbiology, University of Yaoundé I, Cameroon, from January 2017 to June 2018.

Methodology: Total polyphenol content was determined using the Folin Ciocalteu coloric method; the Titatrable acidity and vitamin C content were determined by titration with indicator method. The effect of level of Bacillus cereus contamination, time of thermal treatment and concentration of REO was assessed using a experimental CCD plan. The shelf life was estimated using the storage efficacy of the product on a period of time, and calculated based on the percentage of spoiled products. Data were analysed using XLSLTAT and STATISTICA packages for non-linear regression analyses.

Results: Only 10 min pasteurization at 95°C in the presence of 100ppm of ROE was necessary to totally deactivate 104 Bacillus cereus spores/g in tomato juice while for tomato paste the same concentration of ROE needed 20 min pasteurization at 95°C to totally deactivate up to 108 Bacillus cereus spores/g. Total polyphenols, Titratable acidity and Vitamin C content were affected under this combined processing technique. The storage efficacy of tomato products and hence the extended shelf life was as a result of combined effects between cooking time and microbial load percent reduction that depended on the spore load concentration.

Conclusion: Using Rosmarinus officinalis essential oil can help reduce the thermal impact during tomato juice and paste processing even in condition of high contamination of spores of Bacillus cereus. Moreover in this processing condition, nutritional compounds are not significantly impacted.