Effet de l’addition de l’extrait naturel Curcuma Longa L. sur la stabilité nutritionnelle, microbiologique et sensorielle du yaourt nature.

Abstract

This study aims to evaluate the impact of adding natural extract of Curcuma longa L. on the nutritional, microbiological, and sensory quality of plain yogurt during cold storage at 4°C over a period of 30 days. The first phase, dedicated to the characterization of the plant material, revealed the superiority of the ethanolic extract with a yield of 7%, compared to 3% for the aqueous extract. Phytochemical screening of the ethanolic extract of Curcuma longa L. demonstrated a remarkable richness in phenolic compounds, with total polyphenol content of 120.26 mg GAE/g DW, flavonoids at 29.67 mg QE/g DW, and condensed tannins at 3.35 mg CE/g DW. This composition conferred significant antioxidant activity to the extract, as evidenced by the DPPH assay, with an IC₅₀ value of 157.89 μg/ml. The second phase consisted of enriching plain yogurt with the ethanolic extract of Curcuma longa L. at concentrations of 1% and 3%, in comparison with a control sample (0%). Nutritional analyses showed that the addition of the extract did not significantly affect macronutrient content, particularly proteins and lipids. From a microbiological standpoint, the 1% extract concentration promoted the maintenance of lactic acid bacteria viability (Streptococcus thermophilus and Lactobacillus bulgaricus) throughout storage. Furthermore, while the control sample exhibited proliferation of Staphylococcus aureus and Enterobacteriaceae from day 14 onward, the formulation enriched at 3% induced total inhibition of these pathogenic microorganisms up to day 30, with all batches remaining free of Salmonella sp. Finally, sensory evaluation revealed that the plain yogurt enriched at 3% achieved the highest overall preference, owing to improved creaminess, an appealing color, and subtle aromatic notes. The incorporation of Curcuma longa L. at 3% represents a promising natural alternative for enhancing the microbiological and sensory quality of plain yogurt while preserving its nutritional value. This approach offers an excellent industrial opportunity for the development of innovative functional dairy products, combining effective natural preservation with high nutritional added value.