Background: Microbial spoilage and lipid oxidation are two major factors causing freshness deterioration of Pacific saury (Cololabis saira) during frozen storage. To provide a remedy, the effects of several natural chemicals incorporated alone or in combination in traditional water ice-glazing on the freshness and shelf-life of Pacific saury during frozen storage at -18 °C were investigated. Pacific sauries were subjected to individual quick freezing followed immediately by dipping into cold tap water (control) or solutions containing nisin, chitosan, phytic acid (single-factor experiment) or their combinations ((L₉ (3⁴ ) orthogonal experiment) for 10 s at 1 °C and then packaged in polypropylene bags before frozen storage at -18 °C. The storage duration tested was up to 12 months.

Results: All ice-glazing treatments with individual chemicals could significantly (P < 0.05) inhibit the accumulation of thiobarbituric acid-reactive substances (TBARS), total volatile basic nitrogen (TVB-N) and histamine as well as the increase in bacterial total viable count (TVC) compared with controls, while the combination treatments gave even better effects. The L₉ (3⁴ ) orthogonal experiment showed that the optimal combination was A₂ B₁ C₂ (i.e. 0.5 g L^-1 nisin, 5 g L^-1 chitosan and 0.2 g L^-1 phytic acid). The TBARS, TVB-N, histamine and TVC values in A₂ B₁ C₂ -treated samples remained far below the maximum acceptable limit for good-freshness fish after 12 months of frozen storage at -18 °C.

Conclusion: The incorporation of natural chemicals tested herein in ice-glazing could inhibit microbial spoilage and lipid oxidation and therefore maintain the freshness of Pacific saury during frozen storage. Under the optimal conditions, the shelf-life of Pacific saury could be extended up to 12 months at -18 °C. The study indicated that the combination treatment with natural chemicals could be commercially utilized to maintain the freshness and prolong the shelf-life of Pacific saury. © 2017 Society of Chemical Industry.