D. Sukumar

Comparison of the properties of multi-composite fish gelatin films with that of mammalian gelatin films

Four types of films viz. gelatin, gelatin-MMT, gelatin-chitosan and gelatin-MMT-chitosan prepared from redsnapper and grouper bone gelatin were compared with the mammalian gelatin films, for their mechanical and barrier properties. Grouper gelatin films had higher tensile strength (TS) and Youngs modulus (YM), but lower elongation at break (EAB) than redsnapper films. Incorporation of MMT and chitosan improved the TS (p<0.05) of the films. Water solubilities were lower (p<0.05) in films incorporated with chitosan compared to simple gelatin film. Protein solubilities were lower in gelatin-MMT films, irrespective of the type of solvent used. The water vapour transmission rates (WVTR) of fish and mammalian gelatin films were similar, but addition of MMT had reduced WVTR (p<0.05). SEM micrographs depicted smoother surface for gelatin-MMT and gelatin-MMT-chitosan films. Thus, composite fish gelatin films made with MMT and chitosan could be the good natural biodegradable films due to their better mechanical and barrier properties.

Effect of different types of heat processing on chemical changes in tuna

The chemical changes in skipjack tuna (Katsuwonus pelamis) subjected to cooking, frying, canning and microwave heating were studied. Raw tuna contained an unusual fatty acid C16:3 in high proportion (29.3%) followed by C18:2, C24:1, C16:0 and C18:3. Health beneficial fatty acids, eicosapentaenoic acid (EPA) (1.67%) and docosahexaenoic acid (DHA) (2.50%), were quite low with ω-3/ω-6 ratio 0.28. The total saturated fatty acids suffered major loss in fried (70%) and canned tuna (40%) due to loss of C16:0, C14:0 and C22:0. The monounsaturated fatty acids content increased (38%) in cooked and microwave heated tuna due to C24:1. The polyunsaturated fatty acids content increased in fried (50%) and canned (25%) tuna due to the uptake of frying and filling oil, respectively during processing. The loss of health beneficial ω-3 fatty acids, EPA and DHA were minimum in cooked tuna followed by microwave heated tuna. Canning totally destroyed these fatty acids. In fried tuna, the losses of EPA and DHA were 70 and 85%, respectively. Thiobarbituric acid — reactive substances values increased in heat processed tuna. Cholesterol increased in canned and microwave heated tuna but not in cooked tuna. Reduction of cholesterol in fried tuna was due to its migration into frying oil. This study indicated that cooking and microwave heating are the better processing methods to retain the health beneficial ω-3 fatty acids in comparison to frying and canning.

Quality changes in squid (Loligo duvaucelli) tubes chilled with dry ice and water ice

Squid tubes were packed with 100% (w/w of squid) dry ice (PI), 20% dry ice and 50% water ice (PII) and 50% water ice (PIII) in polyethylene bags and store in thermocole boxes at room temperature (32 ± 2°C) for 24 h. Quality changes curing storage were studied. Lowest temperature of −30.3°C was attained in PI while it was 15–16°C in PII and PIII at 1 h of storage. The gas compositions in packages initially were 21% O2, 0.4% CO2 and 78.1% N2 in PI, PII and PIII, respectively. During storage for 24 h highest level of 82.5% CO2 was noticed in PII. Fresh squid tubes had bacterial flora of Hafnia, Pseudomonas, Bacillus, Flavobacterium and Alcaligens. Hafnia constituted 74% of the flora. Alcaligenes (47%), Alteromonas (30%) and Alcaligenes (56%) were dominant in squid tubes stored in 100% dry ice, in the combination package, and in 100% water ice, respectively. Increase in total volatile base nitrogen and trimethylamine nitrogen, no definite trend in free fatty acid values in all packages while increase in pH in PI and PIII and no consistent changes in PI were noticed during storage for 24 h. The PI had lowest bacterial counts and PIII the highest. Squids stored in PI and PII were sensorily acceptable after 24 and 18 h, respectively.

Quality Evaluation in Chilled Cuttlefish (Sepia pharaonis) Fillets

ABSTRACT The bacteriological, biochemical and sensory quality of cuttlefish (Sepia pharaonis) fillets chilled in ice was investigated. One lot was immediately iced (II) with flake ice at the ratio of 1:1 (wt/wt) and the other lot was left at room temperature of 32°C for 6 h and then iced and designated as delayed iced (DI). Total bacterial count in both II and DI samples ranged from 103 to 107 cfu/g. Total lactic acid bacteria varied from at 0 to 102 cfu/g. Total coliforms became zero on the 3rd d in II sample. TMA-N and TVB-N did not exceed the limit of acceptability. Hx was in between 0.054 and 4.969 mg/100 g in II sample. Delayed icing of cuttlefish fillets reduced the shelf life by 5 days.

Quality of Ornate Emperor (Lethrinus ornatus) Packed in a Combination of Dry Ice and Wet Ice and Stored Under Refrigeration

Ornate emperor (Lethrinus ornatus) stored under refrigeration (5 °C) in a combination of dry ice and wet ice at an optimum level of 1 : 0.2 : 0.5 (w/w/w) were found to be sensory acceptable up to 12 days without re-icing. Samples stored in wet ice at 1 : 1 (w/w) were acceptable for only 8 days. Total bacterial load ranged from 104 to 106 cfu/g, while total psychrotrophs increased 6 log cycles. Lactic acid bacteria count increased 3 log cycles and H 2S producers increased 4 log cycles. Micrococcus constituted 79% of the flora in fresh fish. Micrococcus (40%) was also the dominant flora in the combination pack, while Alcaligenes (26%) was dominant in wet ice pack. TVB-N content did not exceed the limit in any of the packs. Free fatty acid and hypoxanthine contents reached to 18.27% as oleic acid and 13.36mg/100g, respectively at the end of storage. Total fat was very low (0.26%), but total protein was high (25.5%) in the raw fish. During storage in the combined ice pack, there was a gradual reduction in the salt soluble proteins from 77.1 to 62.9%. Raw fish contain health beneficial ω-3 fatty acids particularly docosahexaenoic acid (DHA) at a level of 7.15% out of total fat. The loss of this essential fatty acid during storage in the combined pack was only 61%, while in the control pack, the loss was high (88%).

Microbiological quality of Cuttlefish (Sepia pharaonis) fillets stored in dry and wet ice

Microbiological quality of cuttlefish (Sepia pharaonis) fillets stored in three different ice conditions was studied. Fillets stored in wet ice at a ratio of 1:1 (package III) were sensorially acceptable for only 18 h, while that stored in dry ice at 1:1 (package I) and combination of dry ice and wet ice at 1:0.2:0.5 (package II) were in acceptable condition up to 24 h without re-icing and thus there was an extension of shelf life by about 33%. Total bacterial load was 7 log10 cfu/g at the end of the storage period. Total psychrophilic population increased from zero to 7 log10 cfu/g while total lactic acid bacteria from zero to 5 log10 cfu/g. H2S producers were detected only at 18 h, with a count of 1 log10 cfu/g. Sulphite-reducing Clostridia increased gradually from zero to 110 most probable number count/g. Fresh cuttlefish fillets carried a bacterial flora of Micrococcus, Planococcus, Streptococcus, Moraxella, Proteus and Aeromonas. Pseudomonas was dominant in wet ice pack, while Aeromonas was dominant in both the dry ice and combination pack. Immediately after packing, the temperatures recorded in packages I, II and III were 10.5, 1.2 and 3.0 °C, respectively, which drastically decreased in 1 h and then maintained and finally increased gradually. The results indicate that use of combination of dry ice and wet ice is economical and very much useful to seafood industries, as this package considerably reduced the cost of air freight, as well as improved the quality and shelf life of cuttlefish.