Exploring the effect of utilising organic acid solutions in ultrasound-assisted extraction of pectin from apple pomace, and its potential for biomedical purposes.

Biomass resulting from food production represents valuable material to recover different biomolecules. In our study, we used apple pomace to obtain pectin, which is traditionally extracted using mineral acids. Our hypothesis consisted of carrying out extractions with organic acids, assisted by ultrasound, by varying processing parameters including time, temperature, and type of acid. The analytical determinations of galacturonic acid content, methoxylation and esterification degree, ζ-potential and extraction yield were used as pectin quality indicators. Pectins extracted using treatment conditions with better performance were assessed biologically in vitro for their potential to be used in biomedical applications. Overall, the extracted pectin presented a galacturonic acid content, methoxylation and esterification degree ranged from 19.7 to 67%, 26.8-41.4% and 58-65.2% respectively, and were negatively charged (-24.1 to -13.2 mV). It was found that factors of time and temperature greatly influenced the response variables excepting the esterification degree, while the acid type influenced the ζ-potential, methoxylation and esterification degrees. Additionally, it was seen that the longer extraction time (50 min) and higher temperature (50 °C) exhibited the better extraction yield (∼10.9%). Finally, the selected pectin showed high cytocompatibility up to 500 µg/mL of concentration when seeded with Neonatal Normal Human Dermal Fibroblasts.

Synergistic depolymerisation of alginate and chitosan by high hydrostatic pressure (HHP) and pulsed electric fields (PEF) treatment in the presence of H2O2.

Physically-induced depolymerisation procedures are often preferred for obtaining alginate and chitosan oligosaccharides as they either do not use or make minimal use of additional chemicals; therefore, separation of the final products is facile. In this work, solutions of three types of alginate with different mannuronic and guluronic acid residues ratio (M/G ratio) and molecular weights (Mw) and one type of chitosan were non-thermally processed by applying high hydrostatic pressures (HHP) up to 500 MPa (20 min) or pulsed electric fields (PEF) up to 25 kV cm-1 (4000 µm) in the absence or presence of 3 % hydrogen peroxide (H2O2). The impact on the physicochemical properties of alginate and chitosan was investigated by rheology, GPC, XRD, FTIR, and 1H NMR. In the rheological investigations, the apparent viscosities of all samples decreased with increasing shear rate, indicating a non-Newtonian shear-thinning behaviour. GPC results reported Mw reductions that ranged between 8 and 96 % for all treatments. NMR results revealed that HHP and PEF treatment predominantly reduced the M/G ratio of alginate and the degree of deacetylation (DDA) of chitosan, whilst H2O2 promoted an increase in the M/G ratio in alginate and DDA of chitosan. Overall, the present investigation has demonstrated the feasibility of HHP and PEF for rapidly producing alginate and chitosan oligosaccharides.

Impact of heterogeneously crosslinked calcium alginate networks on the encapsulation of ß-carotene-loaded beads.

This study investigated the impact of heterogeneity of crosslinking on a range of physical and mechanical properties of calcium alginate networks formed via external gelation with 0.25-2% sodium alginate and 2.5 and 5% CaCl2. Crosslinking in films with 1-2% alginate was highly heterogeneous, as indicated by their lower calcium content (35-7 mg Ca·g alginate-1) and apparent solubility (5-6%). Overall, films with 1-2% alginate showed higher resistance (tensile strength = 51-147 MPa) but lower elasticity (Elastic Modulus = 2136-10,079 MPa) than other samples more homogeneous in nature (0.5% alginate, Elastic Modulus = 1918 MPa). Beads with 0.5% alginate prevented the degradation of ß-carotene 1.5 times more efficiently than 1% beads (5% CaCl2) at any of the storage temperatures studied. Therefore, it was postulated that calcium alginate networks crosslinked to a greater extent and in a more homogeneous manner showed better mechanical performance and barrier properties for encapsulation applications.

Chlorophylls and carotenoids of kiwifruit puree are affected similarly or less by microwave than by conventional heat processing and storage.

The impact of microwave (1000 W - 340 s) and conventional heat (97 °C - 30s) pasteurisation and storage (4, 10, 22 °C for up to 63 d) on total and individual carotenoids and chlorophylls in kiwifruit puree was evaluated. Bioaccessibility of carotenoids, before and after pasteurisation and storage, was also studied. Microwaves and conventional heating led to marked changes in the chlorophyll (42-100% losses) and carotenoid (62-91% losses) content. First- and second-order kinetics appropriately explained the degradation of total carotenoids and chlorophylls over time, respectively. Pasteurised samples showed significantly (p < 0.05) enhanced stability of these pigments, with microwaves (k = 0.007-0.031100 g mg(-1) day(-1) at 4-22 °C) promoting chlorophyll stability to a greater extent than conventional heating (k = 0.0015-0.034100 g mg(-1) day(-1) at 4-22 °C). Bioaccessibility of carotenoids remained (p < 0.05) unaffected by processing and storage. These results highlighted that the pigment composition of microwaved kiwifruit was more similar to that of the fresh fruit and better preserved during storage.