Esterase activities of autochthonous starter cultures to increase volatile flavour compounds in Chinese traditional fermented fish (Suan yu)

Figures & data

Table 1. Results for esterase activity (U/mg protein) against different substrates in different cell fractions.

	p-NP-acetate		p-NP-butyrate		p-NP-octanoate
Strains	Intracellular	Extracellular	Intracellular	Extracellular	Intracellular	Extracellular
Lp-120	2.85 ± 0.14^d	3.24 ± 0.10^c	1.30 ± 0.08^f	1.50 ± 0.30^e	12.61 ± 0.03^a	3.71 ± 0.00^b
Sx-135	5.03 ± 0.12^d	12.34 ± 0.40^b	2.19 ± 0.60^e	5.22 ± 1.05^d	15.01 ± 0.60^a	11.32 ± 0.55^c
Sc-31	4.97 ± 0.23^c	7.24 ± 0.06^b	2.14 ± 0.15^e	3.54 ± 0.03^d	10.90 ± 1.61^a	6.22 ± 0.11^b

^a–eValues in the same row with different letters were significantly different (p < 0.05).

Figure 1. Effect of pH (1), temperature (2), and Aw (3) on the intracellular (a) and extracellular (b) esterase activity of the three strains (p < 0.05).

Figure 2. Esterase activity of Suan yu samples at different fermentation stages (p < 0.05).

Figure 3. Changes of pH and Aw in Suan yu samples during the processing.

Table 2. Ester concentrations of Suan yu samples during the processing.

Esters (μg /kg)	Raw	Week 0	Week 1	Week 3	Week 5
NS	34.63 ± 3.82^Ac	48.97 ± 10.54^Ac	143.68 ± 51.70^Cb	299.23 ± 57.62^Ba	307.78 ± 85.22^Ca
S1	34.63 ± 3.82^Ad	48.97 ± 10.54^Ad	116.66 ± 14.03^Dc	206.82 ± 18.74^Db	874.12 ± 56.81^Aa
S2	34.63 ± 3.82^Ac	48.97 ± 10.54^Ac	263.18 ± 39.22^Bb	261.16 ± 15.35^Cb	472.07 ± 37.06^Ba
S3	34.63 ± 3.82^Ac	48.97 ± 10.54^Ac	601.26 ± 96.29^Aa	486.62 ± 36.93^Ab	495.01 ± 39.94^Bb

S1: sample inoculated with L. plantarum 120; S2: sample inoculated with S. xylosus 135; S3: sample inoculated with S. cerevisiae 31; NS: sample without inoculation. week 0: At the end of drying.

^A–B Values in the same column with different letters were significantly different (p < 0.05).

^a–eValues in the same row with different letters were significantly different (p < 0.05).