Physical properties, resistant starch content and antioxidant profile of purple sweet potato powder after 12 months of storage

Figures & data

Table 1. Physical properties of purple sweet potato powder before and after 12 months of storage at chilled and ambient temperatures

Physical properties	Before storage	After 12-months storage
		4ºC	25ºC
Moisture (% db)	3.21 ± 0.02^b	8.10 ± 0.05^a	6.35 ± 0.17^a
Water activity	0.49 ± 0.00^b	0.54 ± 0.00^a	0.49 ± 0.00^b
Color
L	45.93 ± 2.03^b	43.18 ± 1.65^b	49.30 ± 0.16^a
a	15.81 ± 0.70^a	13.06 ± 0.50^b	14.58 ± 0.06^a
b	−3.98 ± 0.18^b	−5.27 ± 0.01^a	−5.50 ± 0.01^a
ΔE	-	4.10 ± 0.31^a	3.90 ± 0.27^a
Water absorption capacity (%)	840.15 ± 3.40^b	827.33 ± 2.04^b	902.04 ± 1.47^a
Water solubility index (%)	25.54 ± 0.87^a	23.67 ± 0.76^ab	21.20 ± 0.90^b

Each value is the average from triplicate readings; Different letters in the same row indicate significant differences (p ≤ 0.05).

Figure 1. The appearance of purple sweet potato powder (a) before and after 12 months of storage at (b) 4ºC and (c) 25ºC

Table 2. Resistant starch content of purple sweet potato powder before and after 12 months of storage at chilled and ambient temperatures

Resistant starch content	Before storage	After 12-months storage
		4ºC	25ºC
Resistant starch (g/100 g)	3.06 ± 0.01^a	1.73 ± 0.00^b	1.57 ± 0.03^c
Non resistant starch (g/100 g)	51.68 ± 0.78^a	48.04 ± 1.20^a	48.63 ± 1.61^a
Total starch (g/100 g)	54.74 ± 0.77^a	49.77 ± 1.21^a	50.20 ± 1.64^a

Each value is the average from triplicate readings; Different letters in the same row indicate significant differences (p ≤ 0.05).

Figure 2. Changes in resistant starch content (mg/100 g) for purple sweet potato powder stored over 12 months at 4ºC and 25ºC

Table 3. Antioxidant properties of purple sweet potato powder before and after 12 months of storage at chilled and ambient temperatures

Antioxidant properties	Before storage	After 12-months storage
		4ºC	25ºC
Total anthocyanin content (mg/100 g)	121.71 ± 0.02^c	197.61 ± 3.91^a	185.33 ± 18.9^b
Total phenolic content (mg GAE/g)	7.54 ± 0.11^a	6.96 ± 0.23^b	7.41 ± 0.04^ab
Total flavonoid content (mg CE/g)	0.52 ± 0.01^b	0.93 ± 0.02^a	0.97 ± 0.03^a
DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity (µmol TE/g)	101.35 ± 0.04^a	77.48 ± 0.16^b	74.16 ± 0.08^c
FRAP (ferric reducing antioxidant power) (µmol TE/g)	134.35 ± 0.13^a	119.46 ± 0.13^b	115.44 ± 0.20^c

Each value is the average from triplicate readings; Different letters in the same row indicate significant differences (p ≤ 0.05); GAE = Gallic acid equivalent; CE = Catechin equivalent; TE = Trolox equivalent.

Figure 3. Correlation between total anthocyanin content (mg/100 g) and DPPH (μmol TE/g) for PSP powder stored at 4ºC and 25ºC