Innovative formulations of chocolates enriched with plant polyphenols from Rubus idaeus L. leaves and characterization of their physical, bioactive and sensory properties

Abstract

In the present study, bioactive content, physical and sensory properties of milk, semisweet and dark chocolates enriched with concentrated (1% and 3%) and freeze dried (1%) red raspberry leaf (Rubus idaeus L.) extract were studied. The addition of 3% concentrated extract reduced the particle size distribution parameter d(0.5) (20.15–16.63μm in milk, 12.55–8.22μm in semisweet and 13.95–12.05μm in dark chocolates), but provided harder chocolates with higher viscosity and rough, coarse product surface, resulting in an unattractive and sensorily unacceptable product. The addition of freeze dried extract increased the particle size of chocolates (d(0.5)=20.15–22.82μm and d(0.9)=53.90–65.47μm in milk, d(0.5)=13.95–14.29μm and d(0.9)=39.51–83.32μm in dark chocolates), but did not cause any significant difference in the chocolate surface, and was scored the best in terms of visual, textural and flavor attributes.The addition of 1% of concentrated or 1% of freeze dried extract did not alter the total phenol content (TPC) (Folin–Ciocalteu method) of enriched chocolate compared to plain samples, while the addition of 3% concentrated extract enhanced the TPC in all chocolates. Proanthocyanidins content was increased only by the addition of 3% of concentrated extract, while the content of flavan-3-ols exhibited an increase after enrichment, but only when determined with vanillin index assay, due to high variability and structural diversity of flavan-3-ols in the substrate, method of non-selectivity or interferences. The displayed results indicate that the used concentrations of raspberry leaf extract are not effective enough for enhancing the bioactive profile of chocolates and that for achieving the optimal physical, bioactive and sensory properties, a freeze dried concentrate of raspberry leaf should be used.