Red raspberry waste as a source of anthocyanin-rich food colorants: extraction process optimization and functionality assessment
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abstract
Food colorants are increasingly used in the food industry to preserve, improve or change the food color. While the quite controversial artificial colorants are widely used in this sector, the natural counterparts have been less selected in part due to the limited availability of options and stability issues
Food colorants are increasingly used in the food industry to preserve, improve or change the food color. While the quite controversial artificial colorants are widely used in this sector, the natural counterparts have been less selected in part due to the limited availability of options and stability issues [1]. Within this class, anthocyanins are naturally occurring colorants that can be found in different plant matrices, including berries such as red raspberry (Rubus idaeus L.). These water-soluble pigments show attractive colors ranging from red to purple and present health-promoting effects [2,3]. Therefore, this work aimed to develop a novel anthocyanin-rich food colorant from red raspberry waste through the optimization of a sustainable extraction methodology and to characterize this ingredient for its functionality. Heat (HAE)- and ultrasound (UAE)-
assisted extraction methods were implemented to recover the anthocyanins from red raspberry. Processing time, ethanol concentration, and temperature or ultrasonic power were the independent variables analyzed in a central composite design coupled with response surface methodology for processes optimization. The extraction yield and levels of anthocyanins (cyanidin-3-O-sophoroside and cyanidin-3-O-glucoside) were monitored gravimetrically and by HPLC-DAD-ESI/MSn , respectively, and used as response criteria. The constructed theoretical models were successfully fitted to the experimental data and used to determine the optimal extraction conditions. Overall, HAE originated slightly higher response values (61% extract weight and 8.7 mg anthocyanins/g extract) but needed 76 min processing at 38 °C, with 21% ethanol, while the UAE process required 16 min sonication at 466 W, using 38% ethanol, to obtain 58% extract weightand 8.3mganthocyanins/gextract.Then,thepredictivemodelswereexperimentallyvalidatedand the purple
red extracts obtained under optimal condition showed antioxidant activity through lipid peroxidation and oxidative hemolysis inhibition, and antibacterial effects against food-related bacteria, such as Escherichia coli and Enterococcus faecalis [4]. These results highlight the potential of red raspberry extracts as natural food colorants with bioactive effects. In future studies, it will be interesting to investigate the stability of the developed anthocyanin-rich extracts when exposed to different stability factors and in real food matrices.
The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national
funds FCT/MCTES to CIMO (UIDB/00690/2020). This research was funded by FEDER-Interreg España-Portugal programme
through the projects 0377_Iberphenol_6_E and TRANSCoLAB 0612_TRANS_CO_LAB_2_P, and by the European Regional
Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope of Project Mobilizador Norte
01-0247-FEDER-024479: ValorNatural®. M. Añibarro-Ortega thanks FCT for his PhD grant (2020.06297.BD). National funding
by FCT, P.I., through the individual and institutional scientific employment program-contract for the J. Pinela
(CEECIND/01011/2018) and L. Barros contracts, respectively. The authors thank Ponto Agrícola Unipessoal, Lda for the samples.
The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020). This research was funded by FEDER-Interreg España-Portugal programme through the projects 0377_Iberphenol_6_E and TRANSCoLAB 0612_TRANS_CO_LAB_2_P, and by the European Regional Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope of Project Mobilizador Norte 01-0247-FEDER-024479: ValorNatural®. M. Añibarro-Ortega thanks FCT for his PhD grant (2020.06297.BD). National funding by FCT, P.I., through the individual and institutional scientific employment program-contract for the J. Pinela (CEECIND/01011/2018) and L. Barros contracts, respectively. The authors thank Ponto Agrícola Unipessoal, Lda for the samples.
