Data from: Sweetpotato chip texture and fat content and the impact of composition and glass transition temperature

The objective of the study was to investigate relationships between sweetpotato chip textures and fat contents with raw compositions and chip glass transitions temperatures.These data are chip breaking forces, chip fat contents, chip glass transition temperatures, raw dry matter, raw sugar, raw starch, raw pectin contents, and pectin degree of methylation. Materials: Ninety sweetpotato clones from the North Carolina State University Sweetpotato Breeding and Genetics Program. Chip Processing: Three roots were sliced into 1.5 mm thick slices (latitudinally), mixed, then 150 g batches were fried at 149 °C for 3 to 3.5 min in canola oil. Frying ended once the rate of steam bubbles slowed. Around 100-150g of raw slices were freeze dried and ground for raw compositional analyses.Chip Texture: Mechanical chip breaking force averages of 20 chips from each sample were measured using a TA.XT2 Texture Analyzer (Texture Technologies Corp., Hamilton, MA, USA) with a 12.7-mm ball probe and Crisp Fracture Support Rig at 0.8 mm/s pretest, 0.5 g trigger force, then 1.0 mm/s test speed for 5 s. The sampled, broken chips were then ground for fat content and glass transition temperature analysis. Chip Fat Content: Fat contents were measured using a Bruker minispec mq-one seed analyzer (Bruker Corp., Billerica, MA, USA) calibrated with the frying oil.Chip Glass Transition Temperature: Ground chip was defatted using Soxhlet extraction and hexanes. The glass transition event of defatted chip powder was measured in a pinholed pan with a Perkin Elmer DSC 6000 (Waltham, MA, USA) by heating to 140 °C, holding for 5 min, cooling to -40 °C, then heating to 140°C at 10 °C/min. The onset temperature of the glass transition of the 2nd scan was used as the glass transition temperature. Raw Dry Matter: Dry matter was calculated by the weight loss from freeze drying.Raw Sugar Contents: One gram of freeze dried sweetpotato powder was weighed into 50 mL polypropylene centrifuge tubes, then 10 mL of 80% ethanol at 70 °C was added, briefly vortexed, mixed for 10 min, centrifuged for 5 min at 6500 g, then the supernatant was decanted into a 50 mL volumetric flask. This was repeated for a total of 3 extractions before the flask was brought up to volume. A 200 µL extract was dried under vacuum (< 1 kPa) at 60˚C for 1 h then 22°C for overnight. Dried solids were reconstituted with 2 mL of water then filtered through a 0.45 µm nylon syringe filter into HPLC vials. Sugars were separated isocratically with 200 mM NaOH at 1 mL/min on a Dionex™ CarboPac™ PA1 (4 × 250 mm) and guard column (4 × 50 mm) (ThermoFisher Scientific, Waltham, MA, USA) at 30 ˚C then detected using an Antec Scientific Decade Elite (Zoeterwoude, Netherlands) PAD with a SenCell 2 mm Au HyRef reference cell. Raw Starch Contents: Starch contents of the alcohol insoluble solids (AIS) from the sugar extraction was measured by enzymatic hydrolysis. Briefly, 100 mg of AIS was weighed into a 15 mL polypropylene centrifuge tube, 10 mL of buffer (pH 5, 100 mM sodium acetate and 5 mM calcium chloride) and 100 µL of thermostable α-amylase (3,000 U/mL) were added, vortexed, then heated for 15 min at 100 °C. Tubes were cooled for 5 min in a water bath at 50°C, then 100 µL of amyloglucosidase (~3,260 U/mL) was added, vortexed, and incubated for 30 min at 50 °C. An aliquot of the hydrolysate was centrifuged then a portion was diluted to a 1:100 ratio. Glucose was measured using the HPLC sugar analysis method and starch of AIS was calculated by the glucosyl to glucose MW ratio (0.90 = 162.1/180.16). The starch content of the raw material was then calculated by accounting for the sugars removed.Raw Pectin Contents: Pectin was estimated by total galacturonic acid released from enzymatic hydrolysis. 100 mg of raw sweetpotato powder, 9.9 mL of buffer (pH 5, 100 mM sodium acetate with 5 mM calcium chloride), and 100 μL of Viscozyme-L were mixed then incubated in a mixing water bath at 50 ˚C for 24 h. Samples were centrifuged and the supernatant was passed through a 0.45 µm nylon syringe filter into HPLC vials. Galacturonic acid was separated from neutral sugars using a Dionex™ CarboPac™ PA1 (4 × 250 mm) with guard column (4 × 50 mm) (ThermoFisher Scientific) at 30 ˚C by the following gradient profile of mobile phase A (100 mM NaOH) and mobile phase B (100 mM NaOH and 170 mM sodium acetate): 0 to 100% B from 0 to 13 min; 100% B from 13 to 23 min; then reequilibrated in 100% A from 23 to 33 min. Pectin contents were calculated by galacturonic acid g/mg on a dry weight basis (dw), multiplied by the galacturonsyl to galacturonic acid MW ratio (0.907 = 176.12/194.14). Raw pectin degree of methylation: 100 mg of raw sweetpotato powder, 1 mL of 10 mM copper sulfate and 25 mM isopropanol in 2mL centrifuge tube were combined and mixed at 0 °C. Then 1 mL of 1 M sodium hydroxide at 0 °C was added and incubated at 1°C for 1 h while mixing at 2,000 RPM in an Eppendorf ThermoMixer® C with a 2.0 mL SmartBlock. After saponification, the slurry was centrifuged at 15,000 g for 10 min at 1°C. The supernatant was extracted using a needle and syringe then passed through a 13 mm, 0.45 µm nylon syringe filter into a HPLC vial insert. Liberated methanol and isopropanol were separated isocratically with 15 mM sulfuric acid at 0.9 mL/min on an Aminex HPX-87H column (9 µm, 300 x 7.8 mm, Bio-Rad Laboratories, Hercules, California, USA) with guard column at 60 °C and detected with a refractive index detector. Methanol contents were calculated using an internal standard calibration with isopropanol as the internal standard. The degree of methylation was calculated as methanol (mM) divided by the galacturonsyl units (mM).