## 4 Discussions

Table 6: Effect of CFS from _A. sobria_ on amino acid content of Pacific white shrimp (_L. unamme_). Figure 6: Effect of cell-free culture supernatant (CFS) from _A. sobria_ on the sodium dodecyl sulfate-polyacrylamideamide gel electrophoresis (SDS-PAGE) profile of the myofibrillar proteins of Pacific white shrimp (_L. unamme_) during different cold chain logistics. to be studied. Until now, the related results have been largely unknown. Our data indicated that the initial bacterial counts of the fresh shrimp samples inoculated by _S. putrefaciens_ were initially around 4.0 log CFU/g. The inhibitory effect on bacterial growth was temperature-related. _S. putrefaciens_ counts in group CK1 and SA1 grew slowly, indicating that 0 \({}^{\circ}\)C is not suitable for _S. putrefaciens_, while CK2 and SA2 grew much faster. Similar studies were also reported that the total counts (TAC) in tilapia fillets increased faster at 10 \({}^{\circ}\)C than stored at 0, 4 and 7 \({}^{\circ}\)C [19]. Table 1 shows that _S. putrefaciens_ counts in group CK3 and SA3 were higher than group CK2 and SA2, respectively (_p_ < 0.05), which indicated that temperature fluctuation during transportation and retailing was beneficial for the growth of _S. putrefaciens_[18]. The CFS from _A. sobria_ results in the decline on the growth of _S. putrefaciens_ after the early stationary phase at refrigerated storage consistent with our previous research results. It was noticeable that bacteria counts were lower in group SA3 treated with CFS from _A. sobria_ in comparison with that in group CK3, which showed that the CFS also has a role in the condition of temperature fluctuation during storage. Similar studies were also reported that the addition of CFS from _P. fluorescens_ to _S. baltica_ culture has caused cell decline during the stationary phase, while had no effect on the growth rate during the lag and exponential phase [12]. It could be hypothesized that plenty of metabolites secreted by _A. sobria_ may influence the micro-environment and regulate the production of substance, which might inhibit the growth of _S. putrefaciens_. The acceptability of shrimp to customer is closely related to their sensory evaluation, including color, odor, texture and elasticity of shrimp. The fresh shrimps were fresh sea-weedy odor and firm texture, while it became strong ammonia odor, sulfur odor and soft texture by the end of storage [30]. The sensory scores for the evaluated attributes of shrimp samples (Figure 3) all decreased with increasing storage time at different cold chain logistics. These results were consistent with [PERSON] et al. who found that the odor and texture of cooked fillets reduced significantly during refrigerated storage (_p_ < 0.05) [31]. The differences between CK2 and CK3 were not significant, and CK1 seemed to be much better than them. The results indicated that the temperature fluctuation can decrease the sensory quality of shrimp. The sensory quality of group SA3 was significantly different from that of group CK3 (Table 2). Therefore, CFS from _A. sobria_ could offset the quality deterioration of shrimp exposed to temperature fluctuation during cold chain logistics. TVB-N is composed of basic nitrogenous substances, such as ammonia and amines, due to the activity of spoilage bacteria and endogenous enzymes. The spoilage activity of _S. putrefaciens_ can be quantified by determining the accumulation of TVB-N [22]. Highest TVB-N value after 6 days of storage were found in CK3 and CK2, and lowest value were found in SA1. Therefore, constant temperature and CFS from _A. sobria_ could inhibit the accumulation of TVB-N. The differences of TVB-N between CK3 and SA3 were less significant than that between CK1 and SA1. The spoilage potential of _S. putrefaciens_ also relates to the activity of amino acid decarboxylase, which catalyzes the production of biogenic amine [11]. _S. putrefaciens_ is chiefly involved in the production of putrescine and cadaverine. Application of CFS from _A. sobria_ in culturing of _S.