ARS | Publication request: Pressurized liquid extraction and quantification of anthocyanins in purple-fleshed sweetpotato genotypes

Submitted to: Journal of Food Composition and Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 22, 2012
Publication Date: May 1, 2012
Repository URL: http://handle.nal.usda.gov/10113/54507
Citation: Truong, V.D., Hu, Z., Thompson, R.L., Yencho, G., Pecota, K.V. 2012. Pressurized liquid extraction and quantification of anthocyanins in purple-fleshed sweetpotato genotypes. Journal of Food Composition and Analysis. 26:96-103.

Interpretive Summary: Recent research on nutraceutical properties of purple-fleshed sweetpotatoes (PFSP) indicated that the extracted anthocyanins have a potential capacity for reducing the risks of several chronic diseases. In the United States, breeding efforts to develop PFSP genotypes suitable for local growing conditions have been carried out in response to the growing interest for healthy food choices and natural food colorants. Analysis of anthocyanins responsible for the purple color is important in genotype evaluation and development of value-added products. This study aimed to optimize the conditions for anthocyanin extraction from PFSP using pressurized-liquid extraction (PLE) method and anthocyanin quantification in various genotypes. The PLE method applies pressure and elevated temperature with liquid solvents to achieve fast and efficient extraction. The use of PLE can improve sample throughput by reducing extraction time and minimizing the use of toxic solvents. Results indicated that anthocyanin levels varied widely among the PFSP genotypes and were in the middle of the spectrum of high anthocyanin fruits and vegetables such as grapes, plum, sweet cherries, raspberries, eggplant and red radishes.

Technical Abstract: Analysis of anthocyanins responsible for the purple flesh color is important for breeding programs and development of value-added products. This study aimed to optimize the conditions for anthocyanin extraction from purple-fleshed sweet potatoes (PFSP) using pressurized-liquid extraction (PLE) method and quantify anthocyanins in various genotypes. Freeze-dried powders of PFSP genotypes were extracted with acidified methanol using an accelerated solvent extractor. Anthocyanin content of the extract was characterized by (a) pH-differential method and (b) color value protocol measuring absorbance at 530 nm, which is commonly used in Japan as a commercial indicator of total anthocyanin quantity. Highest anthocyanin yields by PLE were with an acetic acid:methanol:water mixture of 7:75:18% (v/v), sample weight of < 0.5 g and 80–120 °C. Among 335 genotypes, the anthocyanin content varied widely from 0 to 663 mg cyanidine-3-glucoside equivalent/100 g powder or 0–210 mg/100 g fresh weight. The total monomeric anthocyanin (TMA) contents determined by the pH-differential method were highly correlated with the Japan color value (JCV) protocol, TMA = (0.145) JCV, R^2 = 0.943. These results can be useful for sweet potato breeding programs and processing industry in development of PFSP cultivars and processed products with high anthocyanin levels.