Polyphenol removal with ultrasound-assisted ethanol extraction from defatted walnut powder: optimization of conditions and effect on functional properties of protein isolates

BACKGROUND

Walnut kernels are high in polyphenols (PPs), which cause low protein solubility, limiting the use of walnut protein in the food industry. To obtain the best technical parameters of the dephenolization treatment, the defatted walnut powder was dephenolized using ultrasound-assisted ethanol extraction (UAE), and the response surface optimization was performed on the basis of single factor. On this basis, the effects of dephenolization on the solubility, emulsifying properties and foaming properties of walnut protein isolates (WPIs) were compared to those of defatted walnut powder without dephenolization.

RESULTS

The results showed that PP extraction in the UAE could significantly increase PP yield. The optimal process parameters were as follows: 51% (v/v) ethanol concentration, 140 W ultrasound power, 10 min extraction time, 30 °C ultrasound temperature, and a material-liquid ratio of 1:30 (w/v). The results revealed that the UAE dephenolization treatment significantly improved the functionality of WPI and that the functionality of the dephenolized WPI by UAE was superior to that of the protein without dephenolization, and that the functionality of both walnut proteins was the worst at pH 5, with solubility of 5.31% and 4.86%, emulsifying activity index (EAI) of 24.95 and 19.91 m2 /g, and foaming capacity (FC) of 3.66% and 2.94%, respectively; and the best at pH 11, with solubility of 82.35% and 73.55%, EAI of 46.35 and 37.28 m2 /g, and FC of 35.85% and 18.87%, respectively.

CONCLUSION

The study found that dephenolization by UAE can significantly improve the functionality of WPI, and this method should be promoted and used in walnut and walnut protein processing industries. © 2023 Society of Chemical Industry.

Effect of olive mill wastewaters on Scenedesmus sp. growth, metabolism and polyphenols removal

BACKGROUND

The three-phase extraction process of olive oil produces highly contaminated wastewater (OMW). The elimination of this toxic by-product is an important environmental issue that requires the development of an appropriate management solution. The cultivation of microalgae using OMW as growth medium was therefore studied using single (the culture medium was formed by 0% to 80% ultrafiltered olive mill wastewater (OMUF) or OMW added to BG11) and two-stage strategies (microalgae were firstly cultivated in the BG11 medium. In the second stage, 40% and 80% of OMUF and OMW were added to the culture). In this work, biodegradation of OMW and subsequent extraction of lipid and antioxidant molecules was investigated as an ecofriendly method for the bioremediation and valorization of OMW.

RESULTS

For two-stage cultivation, OMUF and OMW stress enhanced the intracellular amount of polyphenol accumulated in Scenedesmus sp. and exhibited the highest 2, 2-diphenyl-1- picrylhydrazyl radical (DPPH) and 2,2'-azino-bis (3-ethylbenzoline-6-sulfonate) radical (ABTS) scavenging ability compared with single-stage cultivation. Moreover, the lipid profile is dominated by polyunsaturated acids. In the single-stage cultivation, the Ch a, Ch b, carotenoid, carbohydrate and lipid content of 2.57, 7.4, 1.69, 368, and 644 g kg^-1 were observed in 40% OMUF added culture, respectively, along with high biomass productivity and 58% of polyphenol removal. Moreover, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that the biomass of Scenedesmus sp. cultured on 40% OMUF did not show any toxic effect, making it an efficient strategy.

CONCLUSION

The results indicate that Scenedesmus sp. is a promising microalga for the biotreatment of OMW and the extraction of bioactive metabolites. © 2021 Society of Chemical Industry.