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High-power ultrasound pretreatment for efficient extraction of fractions enriched in pectins and antioxidants from discarded carrots (Daucus carota L.)

Idrovo Encalada, Alondra M., Pérez, Carolina D., Calderón, Paola Alzate, Zukowski, Enzo, Gerschenson, Lia N., Rojas, Ana M., Fissore, Eliana N.
Journal of food engineering 2019 v.256 pp. 28-36
Daucus carota, alpha-tocopherol, antioxidant activity, antioxidants, beta-carotene, carrots, food additives, functional foods, gels, lutein, modulus of elasticity, molecular weight, pectins, polymers, sodium carbonate, viscosity
A useful pectin-enriched fraction (PEF) extracted through high-power-ultrasound (HPUS) pretreatment and sodium carbonate was efficiently obtained from discarded carrots. Formerly, the effect of HPUS-power intensity and time (A: 40 min-2.08 W/cm2; B-E: 5–20 min ≈ 10 W/cm2) on carrot powder (CP) used for PEF-isolation, was investigated. Reducing carbohydrates-, cell-wall neutral sugars- (NS), uronic acids- (UA) of pectins, and protein releases increased with HPUS-energy. CP had antioxidant capacity, containing α- and β-carotene, lutein, α-tocopherol. Only HPUS B-E treatments (≈10 W/cm2) were capable to produce matrix disruption, promoting polymers' release. CP pretreated through selected E-treatment (20 min; ≈10 W/cm2) followed by 0.1M-Na2CO3 (1 h-stirring) extracted the whole pectin content of CP (UA = 14.0%). PEFs were orange, with co-extracted antioxidants. More substituted (1.27 NS/UA ratio) three lower molecular weights' components of HPUS-PEF produced higher Newtonian viscosity before shear-thinning, and calcium-crosslinked gels with lower elastic modulus (G’ = 12Pa). Sustainable HPUS/Na2CO3 method isolated efficiently an antioxidants-carrying PEF useful as functional food additive.