EXPOSURE TIME ON BACTERIA FLORA/COUNT AND SHELF LIFE OF CANNED SARDINE (SARDINELLA PILCHARDUS) UNDER AMBIENT AND COLD STORAGE CONDITIONS

Abstract

This study is aimed at investigating the exposure time on bacteria flora/count and shelf life of conned sardine (Sardinella pilchardus) under ambient and cold storage conditions. Twenty-five cans with an average weight of 165.05 g of the Titus (with an expiration date of 4 years (September 30, 2004 to September 30, 2008 of batch no. 1432) were purchased and stored at the ambient temperature of 27C and cold (−4C) storage conditions as samples for 12 weeks (precisely between June 15 and September 10, 2005 when the experiment lasted). Proximate analysis of the samples was taken at the beginning of the experiment and at the end for both the ambient and cold stored (after an exposure time of 24 h). Initial baseline and biweekly studies were carried out for 12 weeks for: (1) organoleptic (odor, taste, texture, appearance, rigidity of flesh, color and reaction of fish with can); (2) chemical (trimethylamine [TMA], peroxide values [PVs] and thiobarbituric acid [TBA]); and lastly (3) microbiological analysis for bacteria count and identification of the bacteria on the samples from each storage environment after an exposure time of 24 h in each case. All the chemical parameters (TMA, TBA and PV) were significantly (P < 0.05) correlated with exposure/storage time. Correlation coefficients r = 0.60, 0.66 and 0.54 were low in all classes therefore indicating spoilage rate increases slightly with exposure time/storage period. The highest PV (0.023–0.715), TBA (0.057–1.056) and TMA (1.01 × 103–3.63 × 103) ranges were recorded for canned sardines stored at ambient temperature of 27C. However, these are still within acceptable tolerance limit (i.e., organoleptic score of 4–7). Organoleptic assessment with average scores of 5.5 and 6.0 was recorded for cold and ambient stored samples. No viable bacteria count was recorded for cold-stored samples throughout the experiment. However, the range initial 1.0 × 105 and final 5.0 × 104 cfu/g total plate counts recorded for ambient storage were still below the minimum bacteria count for spoilage that could cause significant or deleterious effect that could result in food poisoning. Traces of the following bacterial species were recorded at ambient temperatures: (1) Bacillus subtilis (1.2 × 104 cfu/g); (2) Streptococcus faecium (9.0 × 103 cfu/g); (3) Proteus vulgaricus (7.0 × 105 cfu/g); (4) Pediococcus halophilus (6.0 × 105 cfu/g); (5) Micrococcus acidophilus (4.0 × 103 cfu/g); (6) Streptococcus lactis (4.0 × 103 cfu/g); and (7) Aerobacter aerogenes (4.0 × 103 cfu/g), while fungal species Aspergillus terreus (1.0 × 103 cfu/g) and Aspergillus niger (3.0 × 103 cfu/g) were recorded also for samples stored at ambient temperature of 27C. Hence, in view of this, the 4-year recommended expiration date may be upheld for canned sardine (S. pilchardus fish products in oil sources) provided the hazard analysis and critical control points, and closely monitored. It is, therefore, recommended that exposure of canned sardine in oil should not exceed 12–24 h under whatever food storage temperatures to avoid food poisoning.