Viability of lactic acid bacteria in polyphenol-enriched fermented milks

¹ Department of Milk and Dairy Products Technology, Technological Faculty, University of Food Technologies, 26 Maritza Blvd. Plovdiv, BG-4002, Bulgaria
² Department of Food Preservation and Refrigeration Technology, Technological Faculty, University of Food Technologies, Plovdiv, Bulgaria
³ Department of Analytical Chemistry, Technological Faculty, University of Food Technologies, Maritza Blvd. 26, 4002 Plovdiv, Bulgaria

^* Corresponding author: mdimitrova@uft-plovdiv.bg

Abstract

The enrichment of probiotic dairy products with polyphenol extracts from different plant origins is a good approach to enhance the beneficial health effects of functional foods. The aim of the present study was to evaluate the effect of rose (Rosa damascena Mill.) petals polyphenol extract (RPPE) fortification on the lactic acid production and the viability of Lactobacillus delbrueckii subsp. bulgaricus S19 (Lb. bulgaricus), Lactobacillus rhamnosus YW (Lb. rhamnosus) and Streptococcus thermophilus S13 (S. thermophilus) in fermented milk samples during refrigerated storage. The fermented milk samples with RPPE (samples R1 and R2) and without RPPE (samples K1 and K2) were stored at 4 ± 2°C for 15 d. The results for physicochemical parameters showed a constant decrease in the pH values from 4.35 ± 0.04 to 3.99 ± 0.03 and an increase in the lactic acid concentration from 8.68 ± 0.17 g/L to 11.45 ± 0.26 g/L, respectively. The residual lactose concentration in the controls (K1 and K2) and supplemented samples (R1 and R2) at the end of the refrigerated storage was about 32.0 ± 0.24 g/L. Good survival of probiotic strains of lactic acid bacteria was observed. The results show that on the 15th day of refrigerated storage, the total count of lactic acid bacteria remains high - about 2.8 × 10⁸ CFU/ml. Thus, RPPE could be used as a functional ingredient in fermented milk production.