Optimization of deep-fat frying conditions and quality attributes of orange-fleshed sweetpotato crisps by response surface methodology

Figures & data

Table 1. Effect of frying temperature and time on quality attributes of OFSP crisps from Mothers’ Delight variety

Run	Temp. (ºC)	Time (min)	MC (%)	OC (%)	TC (µg/100 g)	L*	a*	b*	Crispiness	Orange colour	Brown colour
1	136	4.5	5.96	31.66	4124.74	49.33	22.31	45.19	3.18	7.97	0
2	140	3.0	18.81	26.30	5953.96	49.45	21.06	37.96	0.03	7.98	0
3	140	6.0	5.25	32.77	4795.52	39.86	13.60	16.79	1.70	8.08	0
4	150	2.4	15.66	29.72	4925.28	56.22	26.78	47.80	0.50	8.80	0
5	150	4.5	2.07	31.43	3793.72	46.58	21.74	36.97	9.29	8.88	0
6	150	4.5	2.21	25.07	3771.22	46.94	18.75	36.90	9.04	8.77	0
7	150	4.5	2.25	29.00	3758.36	46.82	22.45	41.63	9.11	8.81	0
8	150	4.5	2.25	31.67	3713.35	50.85	20.83	43.25	8.88	8.63	0
9	150	4.5	2.27	35.67	3761.58	49.29	23.01	19.62	9.09	8.92	0
10	150	6.6	2.21	35.72	2848.25	41.81	17.67	30.36	9.04	0	7.63
11	160	3.0	5.11	25.78	3677.98	42.91	17.69	33.39	5.39	7.22	0
12	160	6.0	1.74	30.56	3086.03	34.36	14.90	18.61	9.33	0	8.38
13	164	4.5	1.14	31.73	1057.61	37.13	18.26	22.81	9.56	0	9.43

OFSP – orange-fleshed sweetpotato, MC – moisture content, OC – oil content, TC – total carotenoids, L* – lightness, a* – redness, b* – yellowness.

Table 2. Effect of frying temperature and time on quality attributes of OFSP crisps from king J variety

Run	Temp. (ºC)	Time (min)	MC (%)	OC (%)	TC (µg/100 g)	L*	a*	b*	Crispiness	Orange colour	Brown colour
1	136	4.5	5.63	23.96	2643.67	49.20	2.38	32.00	8.90	7.63	1.07
2	140	3.0	3.50	24.28	2597.33	49.59	2.18	30.21	9.15	6.73	1.62
3	140	6.0	15.83	16.74	2526.00	52.99	−2.33	29.59	5.09	6.10	0.19
4	150	2.4	9.43	21.36	4933.68	52.04	−1.32	29.93	3.99	5.56	0.40
5	150	4.5	3.23	22.20	3463.00	53.31	3.15	33.12	9.23	6.69	2.14
6	150	4.5	3.60	21.00	2183.67	51.45	3.01	31.18	7.76	6.55	0.51
7	150	4.5	3.97	24.22	2667.00	45.92	6.54	25.31	9.21	5.43	3.75
8	150	4.5	4.00	25.17	1521.66	40.66	5.42	17.16	9.49	3.22	7.33
9	150	4.5	4.37	22.84	3968.69	46.90	1.22	25.00	9.37	7.31	1.65
10	150	6.6	2.10	26.85	2326.67	40.01	11.19	20.05	9.46	5.32	8.66
11	160	3.0	3.10	24.95	4095.00	43.52	10.11	25.75	8.54	6.03	7.58
12	160	6.0	7.37	20.61	1683.67	53.37	7.13	36.97	7.87	5.40	0.80
13	164	4.5	2.03	25.62	2423.00	48.27	11.54	31.71	9.29	1.97	7.88

OFSP – orange-fleshed sweetpotato, MC – moisture content, OC – oil content, TC – total carotenoids, L* – lightness, a* – redness, b* – yellowness.

Table 3. Analysis of variance for the models for OFSP crisps from Mother’ Delight variety

Responses	Sources of variation	DF	Sum of squares	Mean square	F-value	R^2
MC	Regression	5	358.83	71.77	27.17	0.9510**
	Residual	7	18.49	2.64
	Total	12	377.32
OC	Regression	5	51.32	10.26	0.84	0.3761
	Residual	7	85.14	12.16
	Total	12	136.46
TC	Regression	5	1.317E +007	2.634E +006	6.61	0.8251*
	Residual	7	2.792E +006	3.988E +005
	Total	12	1.596E +007
L*	Regression	5	381.06	76.21	9.14	0.8671**
	Residual	7	58.39	8.34
	Total	12	439.45
a*	Regression	5	100.30	20.06	2.64	0.6536
	Residual	7	53.16	7.59
	Total	12	153.46
b*	Regression	5	693.92	138.78	1.45	0.5094
	Residual	7	668.25	95.46
	Total	12	1362.17
Cr	Regression	5	158.86	31.77	19.29	0.9323**
	Residual	7	11.53	1.65
	Total	12	170.39
Or	Regression	5	156.31	31.26	22.72	0.9420**
	Residual	7	9.63	1.38
	Total	12	165.94
Br	Regression	5	154.37	30.87	16.35	0.9211**
	Residual	7	13.21	1.89
	Total	12	167.58

OFSP – orange-fleshed sweetpotato, MC – Moisture content, OC – Oil content, TC – Total carotenoids.

L* – Lightness, a* – Redness, b* – Yellowness, Cr – Crispiness, Or – Orange colour, Br – Brown colour.

*significant at P < 0.05, **significant at P < 0.01.

Table 4. Analysis of variance for the models for OFSP crisps from King J variety

Responses	Sources of variation	DF	Sum of squares	Mean square	F-value	R^2
MC	Regression	5	151.34	30.27	9.87	0.8758**
	Residual	7	21.46	3.07
	Total	12	172.80
OC	Regression	5	57.20	11.44	2.74	0.6616
	Residual	7	29.25	4.18
	Total	12	86.45
TC	Regression	5	2.831E +006	5.661E +005	0.44	0.2401
	Residual	7	8.958E +006	1.280E +006
	Total	12	1.179E +007
L*	Regression	5	141.29	28.26	1.71	0.5504
	Residual	7	115.43	16.49
	Total	12	256.72
a*	Regression	5	203.79	40.76	7.34	0.8397*
	Residual	7	38.89	5.56
	Total	12	242.69
b*	Regression	5	189.40	37.88	1.57	0.5283
	Residual	7	169.08	24.15
	Total	12	358.48
Cr	Regression	5	33.46	6.69	13.05	0.9031**
	Residual	7	3.59	0.51
	Total	12	37.05
Or	Regression	5	11.76	2.35	0.92	0.3954
	Residual	7	17.98	2.57
	Total	12	29.74
Br	Regression	5	90.05	18.01	3.29	0.7012
	Residual	7	38.37	5.48
	Total	12	128.41

OFSP – orange-fleshed sweetpotato, MC – Moisture content, OC – Oil content, TC – Total carotenoids.

L* – Lightness, a* – Redness, b* – Yellowness, Cr – Crispiness, Or – Orange colour, Br – Brown colour.

*significant at P < 0.05, **significant at P < 0.01.

Figure 1. Effect of frying temperature and time on (a) moisture content, (b) total carotenoids, (c) L* (lightness), (d) Crispiness, (e) orange colour and (f) brown colour of orange-fleshed sweetpotato crisps from Mothers’ Delight variety

Figure 2. Effect of frying temperature and time on (a) moisture content, (b) a* (redness) and (c) crispiness of orange-fleshed sweetpotato crisps from King J variety

Table 5. Optimized frying conditions and quality attributes of OFSP crisps

Variety	Frying temperature (°C)	Frying time (min)	Moisture content (%)	Oil content (%)	Total carotenoids (µg/100 g)	Crispiness	Orange colour
Mothers’ Delight	151.27	4.20	2.85	30.04	3752.33	8.84	8.92
King J	146.36	4.20	5.43	22.25	2803.20	8.47	6.21

OFSP – orange-fleshed sweetpotato.

Figure 3. Sensory attributes of optimized sweetpotato crisps from orange-fleshed varieties

Figure 4. Consumer acceptability of optimized crisps from orange-fleshed sweetpotato varieties