High-power ultrasound for the efficient extraction of pectin fractions from discarded carrots (Daucus carota) and eggplant (Solanum melongena) fruit exocarp

ROJAS, ANA M.; HIGUERA COELHO, RICARDO; IDROVO ENCALADA, ALONDRA M.; FISSORE, ELIANA N.

Conferencia; 7th International Conference on Food Chemistry and Technology; 2021

As an advanced valorization strategy, agro-industrial by-products can be utilized for the extraction of valuable components such as pectins, contributing to sustainability. Pectins are complex polysaccharides of the plant cell-walls with functional properties of technological interest to the food and pharmaceutical industries. We efficiently obtained pectins from the dried and milled tissues of discarded carrots (CP) and eggplant exocarp (EP) through the application of environmentally friendly high-power-ultrasound (HPUS) (9.32 W/cm2 power intensity) in water, as a pretreatment before stirring in 0.1 M Na2CO3 for 1 h (23ºC). This mild alkaline step extracts all cell-wall pectins including those anchored by esterification. A 5g:200mL proportion of CP or EP to water was used for HPUS (VCX 750, Sonics Materials Inc., USA: 20kHz, 80% amplitude, 20 min net time).The pectin yields obtained from CP and EP were 23% and 17.1%, respectively, without HPUS, whereas yields increased up to 35.4% for CP and 29.6% for EP with the HPUS pretreatment. In the latter case, 100% of the pectin (uronic acids, UA) content of CP (14% w/w) and 93.3% of that of EP (23.9% w/w) were extracted, demonstrating the high efficiency of the process due to the previous disruption of CP and EP cell-walls by HPUS. The pectin fractions obtained either without or with HPUS from CP and EP had 40% and 75.4% of UA, respectively, with very low degree of methylesterification. Dynamic mechanical spectra of 2.0% w/v aqueous solutions with Ca2+ (20 mg/100g UA) revealed ?true gels?.