The use of freeze-dried black chokeberry pomace as a by-product in pork burgers

The aim of this study was to evaluate the effect of adding freeze-dried chokeberry (Aronia melanocarpa) pomace at levels of 0.0%, 0.5%, 0.75%, and 1.0% on the quality of pork burgers, marked as B0, B05, B075, and B1, respectively, subjected to heat treatment and storage (+4°C, 21 days). Chokeberry pomace was incorporated as a natural source of dietary fibre and bioactive compounds, as well as a means of valorizing chokeberry-processing by-products. Burgers were baked in a convection steam oven (180°C, 10 min) until an internal temperature of 72°C was reached and subsequently evaluated for selected physicochemical and organoleptic properties.

The addition of chokeberry pomace did not significantly affect (p > 0.05) thermal loss, although the difference between burgers B0 and B1 reached 3.6%. In contrast, pomace addition caused a significant increase in shrinkage (p < 0.05), with the difference between B0 and B1 amounting to 7.8%. Increasing the pomace level reduced the water, protein, and fat contents of burgers and significantly (p < 0.05) increased total carbohydrate content from 0.0% (B0 and B05) to 0.34% (B1). Despite small differences in pH values (maximum 0.05 units), increasing pomace addition resulted in a significant decrease in pH (p < 0.05).

Instrumental color analysis showed a significant (p < 0.05) decrease in lightness (L⁎) and yellowness (b⁎), whereas redness (a⁎) was not affected (p > 0.05) on day 1. Neither chokeberry pomace addition nor storage time significantly influenced burger shear force values (p > 0.05). Organoleptic evaluation indicated high quality of all burger variants, with scores of at least 3.9 points on a 5-point scale. However, burgers containing 1.0% pomace received lower color scores (p < 0.05) on days 1 and 21. The results indicate that the addition of freeze-dried chokeberry pomace should not exceed 0.75%, providing an effective strategy for by-product valorization while maintaining desirable burger quality attributes.