Table 1.

Effect of drying method on pyruvic acid content, colour values (L,a,b) and colour change (∆E) of onion powder

Treatment combination		Pyruvic acid content (μmole/g solid)	L	a	b	∆E
Percent dewatering (%)	Temperature (°C)
0	70	13.3 ± 0.28c,d	61.5 ± 1.36b,c	5.3 ± 0.20g,h	10.2 ± 1.16b,c,d,e	19.4a
30	70	13.7 ± 0.16c,d	60.8 ± 2.41b,c	7.8 ± 0.55e	8.2 ± 0.38d,e,f	7.5c
60*	70	10.9 ± 0.44d,e,f,g	63.6 ± 1.29b,c	9.9 ± 0.60c	4.6 ± 0.26g,h	5.7c
0	60	11.7 ± 0.15d,e,f	53.3 ± 1.27d	5.6 ± 0.28g,h	8.1 ± 0.13e,f	14.4b
30	60	8.6 ± 0.29g,h,i,j	68.1 ± 0.76a	6.5 ± 0.16f	14.9 ± 0.85a	17.3a
60	60	9.4 ± 0.18f,g,h,i	70.7 ± 1.73a	4.4 ± 0.12i	14.3 ± 0.36a	14.2b
0	50	12.4 ± 0.25c,d,e,f	52.9 ± 0.96d	4.8 ± 0.18h,i	11.7 ± 0.60b,c,d	17.9a
30	50	7.4 ± 0.19h,i,j	68.6 ± 1.36a	9.3 ± 0.18d	10.5 ± 1.66b,c,d	15.2b
60	50	7.9 ± 0.22g,h,i,j	63.8 ± 0.43b,c	11.0 ± 0.04b	8.5 ± 0.40c,d,e,f	5.3c
Raw onion		21.8 ± 2.64a	54.9 ± 1.98d	16.4 ± 3.62a	4.0 ± 3.68h	–
Fresh onion pulp (30 % dewatering)		17.2 ± 1.86b	54.1 ± 0.76d	5.7 ± 0.55g,h	3.5 ± 0.26h	–
Fresh onion pulp (60 % dewatering)		16.9 ± 1.90b	59.4 ± 1.22c	7.4 ± 0.33e	5.8 ± 0.16g	–

Different letters in the same column indicate a significant difference (p ≤ 0.05). (n = 3)

^*60 % dewatering and70°C is treatment no. 9 in the orthogonal test