No 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 te...

The keeping quality and shelf life of fermented and unfermented Chrysichthys nigrodigitatus were monitored in this study. Four kilograms of fresh Chrysichthys nigrodigitatus was minced into fine particles (with an initial pH of 7.2 before distribution into 8 samples). Samples 1-4 are unfermented cooked while Samples 5-8 were fermented, not cooked. All the 8 prepared samples barely lasted for two weeks, while samples 1, 3 and 7 lasted for six weeks. Total Volatile Base (TVB) ranged higher (24.12 -29.43) mg/100gm in Samples 1-4 than (14.23 -18.09) mg/100gm recorded in Samples 5-8. In Samples 1-4, FFA values were not significantly (P > 0.05) different; also followed a narrow range of (6.14 -6.45)% while higher range of (6.42 -12.27)% recorded in samples (5-8). Peroxide values (PV) increased in all the 8 samples in the second, fourth and sixth week, however higher values were recorded in Samples 5-8. Acidity generally increased with length (weeks) of fermentation with a gradual drop in pH from 7.2 (in the fresh fish) to pH 4.5 (sample 7), the worst sample at six weeks. Sample 4 with bacteria load of 5.05 × 10 5 at second week and sample 7 (8.2 × 10 5 ) at sixth week became unfit for consumption having exceeded the 5.0 × 10 5 ICMSF standard for safe fish product. Five bacteria species (Lactobacillus sp, Proteus spp, Staphylococcus aureus, Staphylococcus epidermis, Bacillus sp) with the exception of Proteus spwere not represented in sample 1 (due to salt content). Strong positive correlation (r = 0.97, P < 0.01) exists between PV and FFA. Acidityof the fermented products increased over the weeks with strong negative correlation (r = −0.121, P < 0.01) exists between pH and FFA. Acidity (i.e drop in PH) with increasing rancidity since (r = −0.313, P < 0.05) exists between PV and pH.

Three different packaging materials of (37 cm × 25 cm) size (Sealed Transparent Polythene Bag (STPB) Sealed Paper Bag (SPB) (Brown envelope), Open Mouth Polythene Bag (OMPB) (Black incolour)) were used for Oreochromisniloticus (O), Clariasgariepinus (C) and Mormyrusrume (M). Twenty fish samples per species (averaging 250 gm) were hot smoked dried whole for 36 hours at an average temperature of 100˚C. Packaged hot at the rate of 6 fishes per package for each species (three packs for each packaging treatment i.e. 18 pieces were packed while the remaining 2 pieces were used for initial bacteria load and microbial load). Microbial load (Total Viable Count (TVC), Total Coliform Count (TCC) and Total Fungi Count (TFC)) for the fresh fish was initial hot smoked and finally at the end of 12 weeks was monitored. The TVC (bacterial load) of O. niloticus dropped from (10.6-8.4) × 10 4 (fresh state-hot smoked) and M. rume (9.8-7.0) × 10 4 , while C. gariepinus slightly increased from (12.4-12.6) × 10 4. After hot smoking, highest TVC of 8.6 × 10 4 (OMPBC), 8.3 × 10 4 (SPBC) and 8.2 × 10 4 (STPBC) was recorded in C. gariepinus among the 9 packaging at 12 weeks. However highest tendency for heavy TVC is in all OMPB with highest bacteria load in the OMPBC (8.6 × 10 4), 7.6 × 10 4 (OMPBO) and 6.6 × 10 4 (OMPBM). After 12 weeks highest ranged TFC of (0.6-0.7) × 10 4 was recorded in M. rume as against 0.2 × 10 4 recorded in the initial smoked for all. TCC was highest in C. gariepinus (4.0-4.3) × 10 4. Packaging did not limit the existence of microorganisms. Six bacteria species (Micrococcus (acidiophilus, luteus), Bacillus (subtilis, cereus, aureus), Staphylococcus aureus, Streptococcus lactis, Proteus (vulgaricus, morganii), Pseudomonas aureginosa) and three fungi species (Aspergillus (niger, tamari), Rhizopusnigricans, fusariumoxysporum) were represented in all the packages. On the average five bacteria and two fungi species were represented, excepting for OMPBM and OMPBO with six bacteria species.

Eight samples of average size (184.94 gm), live Chrysichthys nigrodigitatus were used to study drip loss, organoleptic assessment and filleting characteristics weekly under varying cold temperature storage conditions of −5, −20 and −29C for a 6‐week period. Wet and dry weights of the samples and six hourly drip losses were taken on a weekly basis. A gradual reduction in weight was observed within an 18‐h period of exposure to air. The storage temperature of fish determines the extent of drip loss. Reducing the cold storage temperature to −29C reduces the drip loss to 5.02%, where r = 0.2840, At −20C, the drip loss was 9.62%, where r = 0.2565, whereas at −5C, the drip loss was 9.87%, where r = 0.0340. Exposure for longer periods may result in further drip losses. Poorest qualities/filleting characteristics were assessed at −5C with a score of 1.50–4.63.

Sensory and non-sensory assessment of frozen fish: Sardinella species and Micromesistius poutassou obtained from four Agricultural Development Programme (ADP) zones (Ibadan/Ibarapa, Ogbomoso, Oyo and Saki) of Oyo State were carried out. Overall acceptability was based on 7-point Hedonic scale (very much liked (7)-very much disliked (1). Chemical tests [Hypoxanthine (Hx), Peroxide value (PV), Trimethylamine (TMA) and Free fatty acid (FFA)] were carried out using standard methods. Data were analyzed using the mean, standard deviation and t-test.Overall acceptability of the two frozen fish species was between 5.47±0.20 and 5.90±0.08.Hx values varied between 22.15±1.04 and 25.96±0.53mg/100g fish for Sardinella spp. and M. poutassou respectively. The values recorded for both Sardinella spp. and M. poutassou were between 17.48±0.81 and 19.79±1.03 meq/kg for PV; 19.03±065 and 23.63±0.60 mg/100g fish for TMA and between 1.38±0.07% and 1.85±0.31% for FFA respectively. In both Sardinella spp. and M. Poutassou respectively, Oyo Zone had the least PV (17.48±0.81; 17.90±0.60meq/kg), TMA level (20.58±0.90; 19.03±0.65mg/100g). Sardinella spp. samples from the Ogbomoso Zone had highest PV (18.83±0.60meq/kg), FFA (1.85±0.13%) and TMA (23.63±0.60mg/100g) levels, and also the highest FFA values (1.81±0.19%) in M. poutassou. Hypoxanthine and TMA valueswere significantly different in the Sardinella spp. and M. poutassou samples across the zones, respectively.Quality of frozen fish was best in the Oyo Zone.All sensory and non-sensory indicators of fish quality were however within acceptable limits in the four zones of Oyo State.

No abstract

The utilization of cheap, abundant, highly prolific T. nilotica (Oreochromis niloticus) for fish paste, cake and especially fishmeal in fish diets as an alternative to conventional fishmeal is tested in this study. Eight different preparations of T. niloticus fish paste were set up for 7 days. Also, dried fish cake and fishmeal were produced and kept for 3 months, part of the fishmeal were used in compounding six isonitrogenous diets with (0, 20, 40, 60, 80 and 100%) of 40% crude protein (CP) to feed Clarias gariepinus fry (0.52–0.73 g), stocking at 30 fry/bowl for 6 weeks. The unfermented, cooked, salted and frozen (at−25C) fish paste (super grade 1) of CP 52.13% was the best, because it did not change its physical appearance and still retained its natural seaweedy odor. The fish cake (CP 38.60%) and fishmeal (CP 65.70%) qualities were still well preserved at 3 months. The Tilapia fishmeal was tested by supplementing with conventional fishmeal on C. gariepinus diets for an experimental period of 6 weeks in order to determine the best level of utilization. Significant variations P < 0.05 occurred at all levels of diet treatments with Tilapia fishmeal (TFD) at 80% being the best‐producing fish with highest specific growth rate (SGR; 3.68) and 0% TFD being the poorest producing fish with lowest SGR (1.61). PRACTICAL APPLICATIONS This study focused on the utilization and product development of available, cheap, abundant protein animal sources such as highly prolific Tilapia niloticus (Oreochromis niloticus) prepared into paste, cake and fishmeal. The fish paste especially the super grade 1 (crude protein [CP] 52.13%), which was salted, cooked and frozen, could be used as sauces and condiments in food and soup preparations. The super grade 1 Tilapia fish paste could be preserved for longer periods at −25C or at much lower temperatures. The fish cake (CP 38.15%) is an Irish potato flour based fish protein concentrate that could last for at least 3 months under storage in a cool dry place. Fish cake can be used as additives in animal feed formulation. The Tilapia fishmeal (CP 65.69%) is a good supplement for the expensive conventional fishmeal at 80% supplementation level, which produced the best growth performance in the diet of Clarias gariepinus fingerlings.