Comparative Analysis of the Effects of Heating and Essential Oil Extracts of Citrus sinensis and Salvia rosmarinus on the Physicochemical and Microbiological Stability of Tomato Concentrate in Bukavu

Abstract

Tomato concentrates are an essential food product worldwide. This study presents a comparative analysis of the physicochemical and microbiological stability of tomato concentrate in Bukavu by comparing traditional heating techniques with the application of essential oil extracts of Citrus sinensis and Salvia rosmarinus, with the aim of proposing a suitable technique for preserving concentrate quality. A cross-sectional laboratory study was conducted on tomato concentrate for 14 days after production and the application of preservation techniques. A locally produced tomato concentrate was treated with heat and essential oil extracts of Citrus sinensis and Salvia rosmarinus for 14 days to evaluate effects on nutritional and microbiological quality. Statistical analyses included ANOVA and hierarchical clustering. Significant differences (p < 0.05) were observed between treated and control concentrates for most physicochemical quality parameters. Lipid content increased in the canned concentrate (0.55 ± 0.05%), whereas total sugars (12.68 ± 0.05%), reducing sugars (20.53 ± 0.01 mg/100 g) and lycopene (57.87 ± 3 mg/100 g) were higher in the oil-treated concentrates. By contrast, beta-carotene (4.4 ± 0.006 mg/100 g) and ascorbic acid (4.4 ± 0.008 mg/100 g) were higher in the control concentrate, while Brix was highest in the canned concentrate (4.75 ± 0.5). The tomato concentrates maintained a stable temperature (23 °C) for 7 days; pH decreased from 4.39 to 3.96, water content increased from 88.3 to 89.6%, and titratable acidity ranged from 1.59 to 2 meq/100 g between the control and canned concentrates over 14 days, except for protein content, which varied from 1.74 ± 0.01 to 1.75 ± 0.005%. pH and humidity positively influenced microbial growth, whereas pH and acidity showed an opposite effect. Heating, essential oil treatments and the control differed in nutritional and antioxidant properties. However, canning was the most effective method for maintaining microbiological stability (0 CFU/g), while essential oil treatments showed moderate antifungal activity (0 to 12,121 CFU/g) and intermediate antibacterial activity (9,333.3 to 17,787.3 CFU/g).