Defined shear and heat treatment of apple pomace: impact on dietary fiber structures and functional properties

Abstract

Food by-products can be modified by extrusion processing. However, the impact of thermal and mechanical stress, respectively, on the structure and thus functional properties of dietary fiber-rich food by-products is still unknown. In the extrusion process, thermal and mechanical stress are coupled, not constant, and difficult to measure or calculate. Thus, their influence on structural changes and functional properties cannot be evaluated separately. In this work, a specific shear cell, denoted by closed cavity rheometer, was used to treat apple pomace with defined thermal and/or mechanical stress. Dietary fiber composition and fiber polysaccharide structures appeared to be more susceptible to high temperatures than mechanical stress. With increasing temperature (and mechanical stress) soluble and low-molecular-weight soluble dietary fiber contents increased, whereas insoluble fiber contents decreased. Arabinans as rhamnogalacturonan type I polysaccharides and galacturonic acid containing pectic polysaccharides were identified as being most susceptible to degradation under these conditions. Furthermore, the defined treatment affected the functional properties. Although changes in the water solubility index (WSI) and/or the water absorption index (WAI) were not detected up to 90 °C, WSI and WAI decreased significantly at a treatment temperature of 120 °C. However, at very high temperatures (160 °C), WSI and WAI increased. The application of shear and longer treatment times resulted in higher WSI values and complex viscosities as compared to low shear stress. Graphic abstract

Molekulare Charakterisierung ferulasäurehaltiger Polysaccharidgele

“…während der Lagerung, wie Wefers und Mitarbeiter (2018) bei der Untersuchung von Äpfeln feststellten. Gleichermaßen sind AN thermo-und säurelabil, wodurch die AN-Zusammensetzung auch erheblich von der Extraktionsmethode beeinflusst wird (Levigne et al, 2002b;Schmid et al, 2021;Oosterveld et al, 1996;Kaya et al, 2014). Bei Studien zu technofunktionellen Eigenschaften von Zuckerrübenpektin konnte festgestellt werden, dass die Feinstruktur der Arabinane die Emulgiereigenschaften beeinflussen kann.…”

Chemical composition and technofunctional properties of carrot (Daucus carota L.) pomace and potato (Solanum tuberosum L.) pulp as affected by thermomechanical treatment

“…The extruder had an L•D −1 ratio of 40 and a die of 2 mm (diameter). The screw configuration was a combination of a kneading zone (3 L•D −1 ) followed by two reverse elements (for detailed schematic illustration see [20], screw configuration 4). The barrel zone consists of eight sections, which can be heated and cooled separately.…”

Sustainable Management and Valorization of Agri-Food Industrial Wastes and By-Products as Animal Feed: For Ruminants, Non-Ruminants and as Poultry Feed

“…Pomace represents the solid remains of processed raw material (fruit or vegetable) and it usually consists of the pulp, skin, stem and seeds. It is referred to as a by-products of the fruit and vegetables [11][12][13]. In Figure 1, fruit and vegetable processing leading to pomace generation is depicted.…”