• Energy Research

Abstract Using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) thermal characteristics and degradation kinetic parameters of apple pomace flours (APF1–5), obtained by dehydration of apple pomace (originating from single and mixed apple varieties, grown both organically and conventionally) and ground to particle size below of 300 μm, were determined. Glass transition (Tg) close to common storage temperature (21 °C) was ascribed to commercial sample and Tg well above it (28–38 °C) to APF1–5. Both values of Tg and low water activity (0.2-0.4) prolong APF shelf-life. The kinetic parameters of the thermal degradation process: activation energy (E) in the range from 83 to118 kJ/mol, logarithmic value of pre-exponential factor (ln(A/min−1)) in the range from 20 to 28, and rate constant (k200) from 0.143 to 0.278 min−1 were calculated. APF samples were grouped according to rate constant (k200) values of thermal degradation process at baking temperature (200 °C). Organic samples were found to have a higher thermal stability.

Following the idea of sustainability in food production, a yogurt premix based on beetroot (Beta vulgaris) pomace flour (BPF) was developed. BPF was granulated with lactose solution containing lactic acid bacteria (LAB) by a fluidized bed. Particle size increased ~30%. A decrease in Carr Index from 21.5 to 14.98 and Hausner ratio from 1.27 to 1.18 confirmed improved flowability of granulated BPF, whereas a decrease in water activity implied better storability. Yogurts were produced weekly from neat starters and granulated BPF (3% w/w) that were stored for up to one month (4 °C). High viability of Streptococcus thermophilus was observed. Less pronounced syneresis, higher inhibition of colon cancer cell viability (13.0–24.5%), and anti-Escherichia activity were ascribed to BPF yogurts or their supernatants (i.e., extracted whey). Acceptable palatability for humans and dogs was demonstrated. A survey revealed positive consumers’ attitudes toward the granulated BPF as a premix for yogurts amended to humans and dogs. For the first time, BPF granulated with LAB was used as a premix for a fermented beverage. An initial step in the conceptualization of a novel DIY (do it yourself) formula for obtaining a fresh yogurt fortified with natural dietary fiber and antioxidants has been accomplished.

Apple and beetroot pomace flour (APF and BPF), along with two sweeteners, sucrose and a blend of sucrose substitutes (erythritol, stevia, inulin, and fructose), were simultaneously incorporated into three matrices formulated with agar, pectin, or gelatin as gelling agents. The aim was to produce jelly candies with high content of dietary fiber and dietary phenolics, and reduced energy value. The simultaneous incorporation of sucrose substitutes and pomace flour resulted in decrease of Carb:Fiber and Sugar:Fiber Ratio to extremely low values of 2.7–3.4 and 1.3–1.6 respectively, as well as in Energy:Fiber Ratio decrease to 9.2–12.3 kcal/g DF. Relative Antioxidant Capacity Index (RACI), as indicator of antioxidant potential, was calculated by assigning equal weight to Folin–Ciocâlteu, DPPH and FRAP assays applied upon in vitro digestion of 18 formulations of jelly candies. Results obtained for formulations with and without sucrose, as well as with and without APF or BPF, enabled insight into effects of pomace flour addition and sucrose substitution in each gelling matrix on functional properties. The incorporation and the substitution impact on postprandial glucose response were followed in vivo. Their superimposing resulted in glycemic index below 30 and low glycemic load. Efficiency of applied approach in functionalization of confectionery burden with energy and minimization of glucose spike represent an example of agro-residues re-introduction with the highest potential contribution to anti-obesity strategy.