Anthocyanin extracts from purple sweet potato by means of microwave baking and acidified electrolysed water and their antioxidation in vitro

Abstract

Two anthocyanin extracts from purple sweet potato (PSP) were prepared by means of microwave baking (MB) and acidified electrolysed water (AEW) or 95% ethanol. The extraction yield in AEW (pH 3.0) was up to 35.0% nearly 2.5 times higher than in ethanol. When pH £ 3.0, the lower the pH values of the extracts in solution were, the darker the red extracts were. Total flavonoids, phenolic and monomeric anthocyanin contents in AEW extract were 132.13, 64.52 and 102.31 mg g )1 , respectively, whose values were the similar to or slightly lower than those in ethanol extract. On the contrary, its total sugar content (61.31 mg g )1 ) was nearly five times higher than that of the ethanol extract. In vitro assay indicated that the scavenging capability of DPPH free radicals of AEW extracts (IC 50 = 12.0 lg mL )1 ) was stronger than that of the ethanolic ones. The reducing power and inhibiting lipid peroxidation of the two extracts were similar. Thus, the new extraction of MB-AEW described here was not only simple and low in cost, but also had much higher extraction yield. The anthocyanin extracts with a strong antioxidation and a stable red colour could be widely used as food colouring additives and anti-ageing health foods.

Composition and color stability of anthocyanin-based extract from purple sweet potato

“…However, the sample at pH 8 exhibited certain instability which was visually confirmed by the difference in color during storage. This instability may result from a gradual process of anthocyanins degradation (Castañeda-Dvando et al, 2009) and phenolic hydroxyl oxidation (Lu et al, 2010), which are prone to take place in alkaline conditions. These results indicate that PSPAs are more stable at low pH values, and alkaline condition should be avoided when PSP extract is used as a colorant in food industry.…”

“…As a group of natural, water-soluble and nontoxic pigments, anthocyanins are widely distributed in plant world and display a variety of colors from orange to purple (Fossen et al, 1998;Janna et al, 2007;Lu et al, 2010). So, some anthocyanin-rich extracts from fruits and vegetables can be used as food colorants to replace the synthetic ones in consideration of consumer preference.…”

“…Thus, PSP is a good source for the preparation of anthocyanin-based food colorant. Acidified methanol and ethanol are commonly used to extract anthocyanins from plant tissues (Castañeda-Dvando et al, 2009) and some new technologies such as microwave-and ultrasonic-assisted methods were also developed to promote the efficiency (Lien et al, 2012;Lu et al, 2010). However, in consideration of cost and environment, a water-extraction process is attractive in food industry.…”

Advances in the Extraction of Anthocyanin from Vegetables

“…The neurological and behavioral effects caused by the synthetic dyes used in food industry are adverse to human health [2]. Therefore, anthocyanins, with their high potential in terms of high stability, high colorant power and low cost, have been considered as a great candidate for this requirement of new sources of pigments.…”

“…Depending on pH values, they account for colour of the plant leaves, flowers and fruits with red, pink, violet, blue and green [2]. The word anthocyanins came from Greek, in which anthos means flower and kyanos means blue.…”