Abstract:

Sensory quality, total volatile base nitrogen (TVBN) value, the growth of spoilage bacteria and pH in sterile
whitefish blocks (as control, CK) and those inoculated with different spoilage bacteria were analyzed, and growth kinetic
parameters of spoilage bacteria and the yield factor for TVBN production (YTVBN/CFU) were used for quantitative measurements
of microbial spoilage to identify the specific spoilage organism (SSO) of whitefish at room temperature. The results showed
that the whitefish blocks inoculated with Morganella sp.wf-1 reached the limit (15.16 h) of sensory acceptability earlier
than CK and whitefish inoculated with Staphylococcus sp.wf-1, Morganella sp.wf-1, Morganella sp.wf-2, Proteus sp.wf-1,
Proteus sp.wf-2 and Proteus sp.wf-3, and TVBN value and total bacterial count were 29.98 mg/100 g and 7.53 (lg(CFU/g)）
at this time point, respectively. The analysis of growth kinetic parameters and YTVBN/CFU for these spoilage organisms showed
that Morganella sp.wf-1 had the shortest lag phase of growth, maximum specific growth rate and YTVBN/CFU, which were 2.60 h,
0.304 6 h-1 and 6.27 × 10-9 mg TVBN/CFU, respectively. The pH value tended to first decline and then rise for CK and all
whitefish blocks inoculated with different spoilage bacteria. Notably, pH of whitefish blocks inoculated with Morganella sp.
wf-1 and Morganella sp.wf-2 was much higher than that of CK and whitefish meat inoculated with other spoilage organisms
at 8–48 h time points. In conclusion, Morganella sp.wf-1 was the SSO in whitefish at room temperature also taking into
account the concept of SSO.

Key words: whitefish, specific spoilage organism, total volatile base nitrogen (TVBN), growth kinetic parameters, Morganella sp.