These data were used for the manuscript \u201cSimultaneous quantification of \u03b2-carotene, anthocyanins, and total phenolics in sweetpotato with visible-near-infrared spectroscopy\u201d by Matthew C. Allan, Ragy M. Ibrahem, Christopher Parish, Suzanne D. Johanningsmeier, Kenneth V. Pecota, and G. Craig Yencho. They are \u03b2-carotene, total phenolics, total monomeric anthocyanins, and anthocyanidins (peonidin, cyanidin, and pelargonidin) contents along with visible-near-infrared spectra (Vis-NIRS) of 203 raw sweetpotato powders.
Materials and Methods
Freeze dried sweetpotato powders (n = 203) were generated from sweetpotatoes that were sliced, freeze dried, then ground into a powder. Sweetpotatoes were selected based on Vis-NIR spectra diversity and historical data of \u03b2-carotene and anthocyanin contents.
Visible - Near Infrared Spectroscopy
Spectra of sweetpotato powders were were collected using a FOSS XDS analyzer (FOSS Analytical, Hilleroed, DK) from 400 to 2500 nm in 2 nm increments.
Compositional analyses
\u03b2-Carotene
1 g of sweetpotato powder was weighed into a 15 mL polypropylene centrifuge tube, 7 mL of hexane with 0.01% w/v BHT (antioxidant) was added, vortexed to disperse, then mixed end-over-end at 40 rpm for 10 min. Tubes were then centrifuged at 6000 g for 5 min, supernatant decanted into 25 mL volumetric flask, and repeated for a total of 3 extractions. Flask was brought to volume, briefly mixed, an aliquot was passed through a 0.45 \u00b5m nylon syringe filter into a 2 mL amber vial, then the headspace of the vial was briefly flushed with nitrogen gas before capping. \u03b2-carotene was quantified using an external calibration curve and Shimadzu Prominence HPLC system (Kyoto, JP) with photo diode array detector at 450 nm. Carotenoids were separated isocratically with 36% methanol, 60% MBTE, and 4% water at 1 ml/min with a YMC (Kyoto, JP) C-30 carotenoid column (5\u00b5m, 4.6 x 250 mm) and guard column at 30\u00b0C. This method has a 98.9% extraction efficiency.
Phenolic and anthocyanin extraction and analyses
Phenolic compounds were extracted using hot acidified methanol. Two hundred and fifty milligrams of sweetpotato powder were weighed into 15 mL polypropylene centrifuge tubes, 10 mL of 0.12 M HCl methanol was added, then mixed for 10 min at 650 rpm and 65\u00b0C in a Thermomixer (Eppendorf, Hamburg, DE). These were centrifuged at 6500 g for 5 min, supernatant was decanted into a 50 mL volumetric flask, and the process repeated for a total of 4 extractions. This method has a 99.5% and 99.8% extraction efficiency for total anthocyanins and phenolics, respectively.
Total anthocyanins
Total monomeric anthocyanins in the methanolic extract were quantified using the pH differential method. Briefly, 200 \u00b5L aliquots of extract were mixed separately with 1800 \u00b5L of pH 1 0.025 M KCl and pH 4.5 0.4 M sodium acetate aqueous buffers. These were vortexed and absorbances at 520 and 700 nm were measured with a Cary 100 UV-Vis spectrophotometer (Agilent, Santa Clara, CA, USA). Extinction coefficient used was 26,900.
Total phenolics
Total phenolic compounds were quantified using the Folin-Ciocalteu total phenolic content assay. Briefly, 350 \u00b5L of phenolic extract, 350 \u00b5L FC phenol reagent, and 5 mL of water were combined, mixed, allowed to sit for 5 min, 1 mL of 20% sodium carbonate was added, mixed, then incubated for 2 h at 30\u00b0C. The 750 nm absorbance values were measured, and phenolics were calculated using an external chlorogenic acid calibration curve.
Anthocyanidin quantities
The anthocyanidins (anthocyanin aglycon) cyanidin, pelargonidin, and peonidin were quantified following acid hydrolysis. 1 mL of methanolic phenolic extract was pipetted into narrow mouthed (8mm) HPLC vials, 0.5 mL of 6 M HCl was added, vials were capped then mixed at 300 rpm and heated at 99\u00b0C in a thermomixer for 1 h. Anthocyanidins were separated using a YMC-Pack Pro C8 plus guard column at 35\u00b0C with the following gradient method at 1 mL/min: solvent A - 5% formic acid in water, solvent B - 5% formic acid in acetonitrile; linear gradient of 10% to 35% B from 0 to 8 min; followed by 5 min of 10% B. Cyanidin and peonidin were detected at 526 nm and pelargonidin at 513 nm and quantified using external standards. This was conducted on the same HPLC system as described above.