Wild Blackberry Fruit (Rubus fruticosus L.) as Potential Functional Ingredient in Food: Ultrasound-Assisted Extraction Optimization, Ripening Period Evaluation, Application in Muffin, and Consumer Acceptance

Abstract

The aim of the present study is to evaluate the antioxidant properties of wild blackberry fruits as well as their possible use in powdered form as a functional ingredient. For this, ultrasound-assisted extraction optimization, ripening stage evaluation, and wild blackberry powder incorporation into a real food matrix were applied. The optimum conditions for extraction were as follows: 60% MeOH, 20 min of extraction time, acidification with 0.5% HCl, and a 1:40 g/mL solid-to-solvent ratio, which allowed the following yields: total polyphenol content (TPC): 53.8 mg GAE/g; total flavonoid content (TFC): 5.78 mg QE/g; total monomer anthocyanin content (TMA): 11.2 mg CGE/g; 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH): 71.5 mg AAE/g; IC₅₀: 52.3 µg/mL. The study also highlighted that, during the ripening process, the TPC (41.4%), TFC (17.0%), and DPPH levels (66.4%) of the fruits decreased while the TMA yield increased. The incorporation of blackberry powder at different levels (5-20%) increased the TPC, TFC, TMA, and antioxidant properties of muffins. Although the muffins enriched with 20% wild blackberry powder had the best chemical properties (TPC: 3.15 mg GAE/g; TFC: 0.52 mg QE/g; TMA: 0.23 mg CGE/g; DPPH: 1.70 mg AAE/g; IC₅₀: 1.65 mg/mL), the sensory analysis showed that the addition of blackberry fruit at a concentration of 10% to the muffins resulted in the best consumer acceptability.

Keywords: antioxidant compounds; blackberry fruit; functional food; ultrasound-assisted extraction.

Figure 1

Schematic diagram of the optimization procedure.

Figure 2

Effect of solvent type on TPC, TFC, TMA, and DPPH yield. Data presented as mean ± SD of measurements. Different letters indicate significant differences.

Figure 3

Effect of ripening stage on TPC, TFC, TMA, and DPPH yield. Data presented as mean ± SD of measurements. Different letters indicate significant differences.

Figure 4

Consumer acceptance evaluation of muffins; 5%—enriched with 5% blackberry powder; 10%—enriched with 10% blackberry powder; 20%—enriched 20% blackberry powder.

Figure 5

Muffin samples with different concentrations of blackberry powder.

Figure 6

PCA (A) and AHC (B) analyses of independent factors used for the OFAT optimization.

Figure 7

PCA (A) and AHC (B) analyses of ripening stages.

Figure 8

PCA (A) and AHC (B) analyses of muffin samples.