Changes During Processing and Sodium Chloride Supplementation on the Physical and Chemical Properties of Douchi

Figures & data

Table 1 Changes in Hunter L-values, a-values, and b-values and total color difference (ΔE) during in processing. ^a

Step	L-values	a-values	b-values	ΔE
Soaked soybeans	54.40 ± 2.13 A	−4.03 ± 0.28 H	14.39 ± 2.30 A	— ^b
Steamed soybeans	46.31 ± 0.71 B	0.35 ± 0.18 EF	5.95 ± 1.30 D	12.48
12h	43.28 ± 0.24 C	0.20 ± 0.01 FG	9.54 ± 0.06 B	12.85
24h	41.74 ± 0.72 D	0.40 ± 0.08 E	5.90 ± 0.24 D	15.87
36h	40.92 ± 0.40 DE	0.62 ± 0.06 D	10.27 ± 0.10 B	14.85
48h	40.14 ± 0.24 E	0.12 ± 0.08 G	7.02 ± 0.20 DC	16.58
60h	37.76 ± 0.14 F	1.6 ± 0.01 C	6.52 ± 0.01 DC	19.25
1wN10 ^c	35.82 ± 0.52 G	3.79 ± 0.09 A	10.13 ± 0.06 B	20.60
2wN10 ^c	29.04 ± 0.20 G	3.20 ± 0.07 B	5.99 ± 0.07 D	27.67
3wN10 ^c	29.24 ± 0.24 H	3.30 ± 0.04 B	5.92 ± 0.08 D	27.54
^aValues represent the mean ± standard deviation; n = 9. Values in a column with different superscripts were significantly different (p < 0.05). ^bA reference sample (soaked soybeans), cannot be calculated. ^c10 = 10% NaCl content in Douchi.

Table 2 Changes in firmness and chemical parameters in Douchi processing. ^a,b

Step	Moisture (%)	Firmness (g)	pH	Soluble protein (%)	Amino-type nitrogen (%)
Raw soybeans	9.46 ± 0.01 E	— ^c	— ^c	9.16 ± 0.45 E	2.58 ± 0.02 D
Soaked soybeans	54.25 ± 0.01 B	441 ± 47 A	6.66 ± 0.002 D	14.07 ± 0.56 C	3.54 ± 0.01 C
Steamed soybeans	55.29 ± 0.45 A	324 ± 78 C	6.88 ± 0.001 B	13.39 ± 0.78 D	1.19 ± 0.03 D
Douchi qu (60h)	48.44 ± 0.30 C	407 ± 57 B	8.43 ± 0.045 A	18.99 ± 2.95 B	6.01 ± 0.02 B
Douchi (3wN10 ^d )	42.95 ± 0.01 D	138 ± 47 D	6.71 ± 0.033 C	48.51 ± 0.02 A	26.46 ± 0.03 A
^aValues represent the mean ± standard deviation; n = 3. ^bValues in a column with different superscripts were significantly different (p < 0.05). ^cNot detected. ^d 3wN10 = 10% NaCl content in Douchi at third weeks post-fermentation.

Figure 1 Changes in the firmness of Douchi during Douchi post-fermentation at various NaCl content. Results are mean + S. D. of thirty determinations. Bars with different letters were significantly different (p< 0.05).

Figure 2 Changes in pH value during Douchi fermentation. Results are mean ± S. D. of three determinations.

Figure 3 Changes in pH value during Douchi post-fermentation at various NaCl content. Results are mean ± S. D. of three determinations.

Figure 4 Changes in the percent content of soluble protein and amino-type nitrogen during Douchi fermentation. Results are mean ± S. D. of three determinations.

Figure 5 Changes in the percent content of soluble protein during Douchi post-fermentation. Results are mean ± S. D. of three determinations.

Figure 6 Changes in the percent content of amino-type nitrogen during Douchi post-fermentation. Results are mean ± S. D. of three determinations.

Figure 7 SDS-PAGE patterns of Douchi samples during processing. Lane 1: molecular weight marker; lane 2: raw soybean; lane 3: at 60 h in fermentation; lane 4–7: at 1 w in post-fermentation combined with 5, 7.5, 10, and 12.5% NaCl, respectively; lane 8-11: at 3 w in post-fermentation combined with 5, 7.5, 10, and 12.5% NaCl, respectively.