Faculdade de Ciências e Tecnologia
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Browsing Faculdade de Ciências e Tecnologia by Field of Science and Technology (FOS) "Ciências Agrárias::Biotecnologia Agrária e Alimentar"
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- Antioxidant and phenolic compounds in sweet potato peels and leaves: food applications and health benefitsPublication . Anastácio, Ana; Carvalho, Isabel Saraiva deThe valorisation of sweet potato (Ipomoea batatas L.) wastes into a food application with health benefits was studied using a product development framework to translate a product concept into a benchtop prototype. A functional beverage with attributes related to oxidative stress protection was developed using sweet potato peel (SPP) and sweet potato leaf (SPL) as components. The developing processes involved the following steps: literature and patent review, preliminary study, key factors screening, extraction optimization and beverage formula optimization. Total phenolic content (TPC) and antioxidant activity was measured by Folin-Ciocalteau method and antioxidant activity by in vitro screening assays. Literature and patent review for the period 2003-2014 identified research gaps on food applications with health benefits for SPL and especially SPP. Text mining analysis on articles abstracts could picture research main themes. A preliminary study using a factorial design revealed that plant part (stems or leaves) presented the largest main significant effect (p < 0.001) on TPC, total flavonoids content (TFC), total antioxidant activity (TAA), reducing power (RP) and ferric reducing activity power (FRAP) while for DPPH scavenging assay, solvent acidification was the most influential factor. Time of extraction had the only significant effect on RP assay, as main effect and interaction with plant part. Solvent: solid ratio and peel cut depth were the key factors identified by a Plackett-Burman design for the aqueous extraction of phenolics of SPP flour. The aqueous extraction conditions of phenolic from SPP flour were modelled by Response Surface Methodology (RSM) and Artificial neural Network (ANN) analysis of a Central composite Design (CCD) experimental plan. Optimized conditions were 60 mL/g for solvent: solid ratio, 30 min for time and 75 ºC for temperature. Predicted responses were 11.87 ± 0.69 mg GAE/g DM for TPC, 12.91 ± 0.42 mg TE/g DM for ABTS and 46.35 ± 3.08 mg TE/g DM for DPPH assay. Beverage formula components SPP aqueous extract (SPPE), SPL water extract (SPLE) and honey solution (HonS) were combined according to a mixture design. The optimized formula obtained by ANN models for the SPP beverage benchtop prototype was 50.0 % of SPPE, 21.5 % of SPLE and 28.5 % of HonS. TPC, FRAP, DPPH assays and SS predicted responses for the optimal formula were 309 mg GAE/L, 476 mg TE/L, 1098 mg TE/L and 12.3 ± 0.8 ºBrix, respectively. Beverage positioned next to commercial vegetable and fruit beverages in terms of antioxidant activity. Knowledge transfer of these findings to food processors may offer an opportunity to transform SPP and SPL from a liability to an asset and promote further research on food application with health benefits.