Effect of ethanolic extraction, thermal vacuum concentration, ultrafiltration, and spray drying on polyphenolic compounds of tropical highland blackberry (Rubus adenotrichos Schltdl.) by‐product

Abstract

Tropical highland blackberry by‐product (BBP) has high amounts of polyphenols including ellagitannins (ET) and anthocyanins (ATC). Information of the effect of different operations on ET is scarce. In this study, pseudo‐first and first order kinetic models and response surface methodology were applied to optimize the extraction of polyphenols from BBP using ethanol, a food grade solvent. Retention of total polyphenols, ET and ATC was analyzed considering their contents before and after the application of thermal vacuum concentration, ultrafiltration, and spray drying. The optimal conditions for extraction were: a 3.4 solvent/BBP ratio, 57.1% ethanol, 60.0°C, and 120 min extraction time. Thermal vacuum concentration showed a higher retention of ET. A higher purity of ET was accomplished with ultrafiltration. These results provide the basis for further research on the development of a powder enriched with polyphenols, mainly ET, from BBP for food and pharmacological purposes. Practical applications Ellagitannins (ET) are a group of polyphenols found in tropical highland blackberries grown in Costa Rica, mainly in their seeds that are discarded as a by‐product (BBP) during blackberry processing. The production process of an ingredient with high amounts of ET has not been widely reported. In this study, modeling and optimization of an ethanolic extraction of polyphenols from BBP, and the effects of thermal vacuum concentration, ultrafiltration and spray drying on polyphenolic compounds were analyzed. This information will lead to further experiments on the effective recovery of ET in order to produce a nutraceutical product, which is not only complementary to the diet, but may also aid in the prevention and treatment of diseases, or an ingredient to be used in the production of functional foods.

The Kinetics of Two-Step Ellagitannin Extraction from the By-products of Selected Processed Fruits of the family Rosaceae

“…For the tested pomace variants, the extraction rate constants were on average 40% higher in the first step (0.012 to 0.021 min −1 ) than in the second step (0.0068 to 0.013 min −1 ), except for pomace from the production of wild strawberry puree (0.010 min −1 vs. 0.012 min −1 ). In a study on the kinetics of ET extraction from blackberry byproducts, Quirós et al (2019) obtained an extraction rate constant of 0.079 min −1 , which is in line with the present findings (the extraction rate constant for blackberry pomace in the first step was 0.012-0.021 min −1 ). In terms of the kinetics of total polyphenolic extraction from fruit material, Khan et al (2010) reported a rate constant of 0.03 min −1 for orange peels (also using a first-order model).…”

“…In terms of the kinetics of total polyphenolic extraction from fruit material, Khan et al (2010) reported a rate constant of 0.03 min −1 for orange peels (also using a first-order model). Similar polyphenolic extraction constants have been reported from studies involving blackberry biomass (0.023 min −1 , Quirós et al 2019) and grapes (0.040 min −1 , Sant' Anna et al 2012). In the present study, the extraction half time t 1/2 did not exceed 1 h for any of the tested raspberry and blackberry pomace variants (in the first step), with a significant slowdown in the ET extraction rate after that time.…”

“…The parameters that are typically used to evaluate the fit of extraction kinetics models are the p-value, the determination coefficient R 2 , and the standard error of estimation (SEE) (Quirós et al 2019). In a study on the kinetics of blackberry ET and anthocyanin extraction by Quirós et al (2019), a first-order kinetics model revealed a slightly better fit as compared to a modified pseudo-firstorder model (the latter was marginally better in the case of total polyphenolic extraction) (Sant'Anna et al 2012). Also other studies on the kinetics of polyphenolic extraction from plant matrices indicate a good fit of first-order kinetic models (Spiro and Pui-Lang 1995;Torun et al 2015;Bucic-Kojic et al 2013).…”

“…The choice of the right kinetic model mainly depends on the plant matrix. To date, researchers have mainly focused on the kinetics of ET extraction from two sources-blackberry biomass and oak chips (Quirós et al 2019;Puech et al 1996;Garcia-Estevez et al 2015;Psarra et al 2015). The kinetics of polyphenolic extraction from a fruit matrix have been described using a first-order model (Quiros et al 2019;Khan et al 2010) with modifications (Bucic-Kojic et al 2013;Sant'Anna et al 2012).…”

“…The kinetics of polyphenolic extraction from a fruit matrix have been described using a first-order model (Quiros et al 2019;Khan et al 2010) with modifications (Bucic-Kojic et al 2013;Sant'Anna et al 2012). In a study on the kinetics of polyphenolic extraction from a blackberry matrix, the first-order model was characterized by a high R 2 coefficient (0.860 for ETs, 0.994 for anthocyanins) with a low estimation error (Quirós et al 2019). A secondorder model has been applied to ET extraction from wood (Lazar et al 2016;Puech et al 1996).…”