Preservation of iced refrigerated sea bream (Sparus aurata) by irradiation: microbiological, chemical and sensory attributes

Quality and shelf life of non-irradiated and irradiated (2.5 and 5 kGy) sea bream in ice conditions and stored at +4 °C were investigated by measurement of microbiological, chemical and sensory analysis. Microbial counts for non-irradiated sea bream samples were higher than respective irradiated fish. Total volatile base nitrogen (TVB-N) values increased value of 38.64 mg/100 g for non-irradiated, sea bream during iced storage whereas for irradiated fish lower values of 13.48 and 12.06 mg/100 g were recorded at 2.5 and 5 kGy, respectively (day 19). Trimethylamine (TMA-N) values and thiobarbituric acid (TBA) values for irradiated samples were lower than non-irradiated samples. Acceptability scores for odour, taste and texture of cooked decreased with storage time. The sensory scores of sea bream stored in control and 2.5–5 kGy at +4 °C were 13 and 15 days, respectively. The results obtained from this study showed that the shelf life of sea bream stored in ice, as determined by overall acceptability all data, is 13 days for non-irradiated sea bream and 15 days for 2.5 kGy irradiated and 17 days for 5 kGy irradiated sea bream.     

Nucleotide degradation products of gamma‐irradiated sea bream (Sparus aurata) stored in ice

Nucleotide degradation products of irradiated sea bream stored up to 19 days in ice were investigated. Irradiation had significant effect on the nucleotide concentrations in sea bream muscle (P < 0.05). The results showed that the highest value of inosine monophosphate (IMP) was observed in irradiated sea bream at 5 kGy, followed by at 2.5 kGy. Initial inosine (INO) concentration in irradiated sea bream at 5 kGy was 4.26 μmoles g^?1, which reached maximum value of 8.83 μmoles g^?1 when fish completely spoiled (19 days). When the fish reached the limit of acceptability, the mean values of K, Ki, H and G were 86.8%, 90.3%, 59.8% and 213.9% for unirradiated sea bream, 85.2%, 87.8%, 56.8% and 197.8% for irradiated sea bream at 2.5 kGy and 88.4%, 90.9%, 57.8%, 211.5% for irradiated sea bream at 5 kGy, respectively. The results of this study indicated that nucleotide degradation was more rapid in unirradiated sea bream than those irradiated. K, Ki, H and G value in irradiated fish can be used as a freshness index because there is a good linear relationship between values and storage time of fish.     

Antioxidative and antimicrobial activities of shrimp chitosan on gilthead sea bream (Sparus aurata) during refrigerated storage

This study aims to determine the effects of chitosan obtained from Metapenaeus stebbingi shells on the shelf life of refrigerated gilthead sea bream. It was determined that 1% chitosan‐coated samples had the lowest thiobarbituric acid (TBA) (3.05 mg malondialdehyde (MDA) kg^?1) and free fatty acids (FFA) value (2.79% oleic acid), while the control group had the highest TBA (5.08 mg MDA kg^?1) and FFA value (6.13% oleic acid) on the 27th day of storage. In the last day of storage, TVB‐N was found higher in control group (25.62 mg 100 g^?1) than chitosan‐coated samples (14.57 mg 100 g^?1). Total viable count value of the control group exceeded maximum permissible limit on the 27th day of storage. However, it was lower than 7.0 log CFU/g in chitosan‐coated samples during the refrigerated storage. As a result of this study, it was determined that shelf life of refrigerated gilthead sea bream can be increased up to 27 days with chitosan.     

The effects of natural antioxidants and lighting conditions on the quality characteristics of gilt‐head sea bream fillets (Sparus aurata) packaged in a modified atmosphere

The effects of lighting conditions and the application of natural antioxidants (rosemary extract and ascorbic acid) on the shelf‐life of gilt‐head sea bream fillets (Sparus aurata) packaged in a modified atmosphere (MAP) and stored at 1 ± 1 °C were studied. Lighting with low‐UV colour‐balanced lamps led to an extension of shelf‐life compared with that under supermarket fluorescent tubes, as assessed by lipid oxidation (TBARS value) and sensory evaluation. The application of antioxidants to the surface of MAP fillets delayed lipid oxidation besides improving the sensory quality. Rosemary extract was more effective than ascorbic acid in delaying lipid oxidation under both kinds of lighting. The effect of ascorbic acid was greater in the samples illuminated by low‐UV tubes than in those stored under conventional lighting. However, the effectiveness of rosemary extract was similar in both kinds of lighting conditions. Copyright © 2004 Society of Chemical Industry     

Effects of gutting and ungutting on microbiological, chemical, and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice

The effect of gutting and ungutting on microbiological, chemical, and sensory properties of aqua-cultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice were studied. The total viable mesophilic and psychrophilic bacterial counts increased throughout the storage period of gutted and ungutted sea bream and sea bass. The mesophilic counts reached 8.19 log cfu/g for ungutted sea bream and 7.93 log cfu/g for ungutted sea bass after 14 days of storage. The mesophilic counts reached 8.89 log cfu/g for gutted sea bream and 8.16 log cfu/g for gutted sea bass after 14 days of storage. On day 14 of storage the psychrophilic counts of ungutted sea bream and sea bass were 8.24 log cfu/g and 8.03 log cfu/g, respectively, and for gutted sea bream and sea bass were 8.93 and 8.22, respectively. At the end of the storage period of 14 days, TVB-N, TBA, and TMA-N values of ungutted sea bass were determined as 50.13 +/- 0.25 mg/100 g, 2.66 +/- 0.06 mg malonaldehit/kg, 9.86 +/- 0.01 mg/100 g respectively. TVB-N, TBA, and TMA-N values of ungutted sea bream reached 55.90 +/- 0.36 mg/100g, 2.51 +/- 0.21 mg malonaldehit/kg, 9.79 +/- 0.01 mg/100 g on day 14 respectively. And also at the end of the storage period of 14 days, TVB-N, TBA, and TMA-N values of gutted sea bass were determined as 48.00 +/- 0.26 mg/100 g, 2.48 +/- 0.03 mg malonaldehit/kg, 8.71 +/- 0.06 mg/100 g respectively. TVB-N, TBA, and TMA-N values of gutted sea bream reached 49.66 +/- 0.77 mg/100g, 2.64 +/- 0.07 mg malonaldehit/kg, 8.97 +/- 0.01 mg/100 g on day 14 respectively. The result of this study indicates that the shelf-life of whole ungutted sea bass and sea bream stored in ice as determined by the overal acceptibility sensory scores, chemical quality, and microbiological results show us that the fish were spoilt on day 14. Each chemical, sensory, and microbiological result for sea bream showed us that there was a correlation and similarity and on day 14 it was spoilt.     

Preservation of salted,vacuum-packaged,refrigerated sea bream (Sparus aurata) fillets by irradiation: microbiological,chemical and sensory attributes

The effect of gamma irradiation (1 and 3 kGy) on the shelf-life of salted, vacuum-packaged sea bream (Sparus aurata) fillets stored under refrigeration was studied by monitoring the microbiological, chemical and organoleptic changes occurring in fish samples. Non-irradiated, salted, vacuum-packaged fish served as control samples. Irradiation affected populations of bacteria, namely, Pseudomonas spp., H₂S-producing bacteria, Brochothrix thermosphacta, Enterobacteriaceae and lactic acid bacteria. The effect was more pronounced at the higher dose (3 kGy) applied. Of the chemical indicators of spoilage, trimethylamine (TMA) values of non-irradiated, salted sea bream increased slowly to 8.87 mg N (100 g)⁻¹ flesh (whereas for irradiated, salted samples significantly lower values were obtained, reaching a final TMA value of 6.17 and 4.52 mg N (100 g)⁻¹ flesh at 1 and 3 kGy, respectively (day 42). Total volatile base nitrogen values increased slowly attaining a value of 60.52 mg N (100 g)⁻¹ for non-irradiated, salted sea bream during refrigerated storage whereas for irradiated fish, lower values of 48.13 and 37.21 mg N (100 g)⁻¹ muscle were recorded at 1 and 3 kGy, respectively (day 42). Thiobarbituric acid values for irradiated, salted sea bream samples were higher than respective non-irradiated (salted) fish, and increased slowly until day 28 of storage reaching final values of 1.01 (non-irradiated, salted), 2.15 (1 kGy) and 3.26 mg malonaldehyde kg⁻¹ flesh (3 kGy), respectively (day 42). Sensory evaluation (taste) showed a reasonably good correlation with bacterial populations. On the basis of sensorial evaluation, a shelf-life of 27–28 days was obtained for vacuum-packaged, salted sea bream irradiated at 1 or 3 kGy, compared to a shelf-life of 14–15 days for the non-irradiated, salted sample.     

Reduction in flatulence factors in mung beans (Vigna radiata) using low‐dose γ‐irradiation

Mungbeans (Vigna radiata), control and γ‐irradiated at insect disinfestation dose levels (0.25 and 0.75 kGy) were germinated (0–6 days) and the qualitative and quantitative changes in soluble carbohydrates were studied in detail. The key flatulence‐producing raffinose family oligosaccharides in mungbeans were degraded in the irradiated samples at the onset of the germination (0–2 days) compared to the control where it occurred much later (>4 days). However, the reducing sugars, mainly glucose, fructose and galactose, which are metabolised easily, were enhanced in the irradiated samples. At low dose (0.25 kGy), irradiation had no effect on germination and sprout length, indicating that irradiated beans are suitable for use as sprouted beans. These observations clearly indicate that γ‐irradiation at insect disinfestation dose levels improved the digestibility and nutritional quality of mung beans by reducing the content of oligosaccharides responsible for intestinal gas production. © 1999 Society of Chemical Industry     

Effect of γ‐irradiation on post‐harvest ripening of plantain fruit (Musa paradisiaca) cultivars

Three plantain cultivars, Agbagba, Obino L'ewai and Cardaba, harvested at two stages of maturity, were irradiated at 0.1–1.0 kGy prior to storage under tropical ambient conditions. Post‐irradiation storage behaviour showed that plantain fruits at full three‐quarter grade were more responsive to irradiation treatment than at full grade maturity, while Cardaba, a type of cooking banana, showed the least response. Irrespective of varietal differences, irradiation to 0.5 kGy or higher caused severe tissue damage, softening and skin discolouration; however, γ‐irradiation at optimum dose range of 0.15–0.30 kGy effectively delayed ripening for 10–12 days in Agbagba and Obino L'ewai, respectively, without affecting respiratory pattern or fruit quality. © 1999 Society of Chemical Industry     

Effect of ungutting on microbiological, chemical and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice

The effect of ungutting on microbiological, chemical and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice were studied. The total viable mesophilic and psychrophilic bacterial counts increased throughout the storage period of ungutted sea bream and sea bass. Mesophilic counts of ungutted sea bream and sea bass reached 7.39 log cfu/g and 7.26 log cfu/g after 9 days. At the end of the storage period of 14 days; TVB-N, TBA, TMA-N values of ungutted sea bream were determined as 37.5±0.51 mg/100 g, 3.82±0.03 mg MA/kg, 7.73±0.25 mg/100 g, respectively. TVB-N, TBA, TMA-N values of ungutted sea bass were reached 35.4±0.9 mg/100 g, 3.75±0.81 mg MA/kg, 6.94±0.08 mg/100 g on day 14th, respectively. Result of this study indicates that the shelf life of whole ungutted sea bream stored in ice as determined by the overall acceptability sensory scores, chemical quality and microbiological data is 12, 9 and 9 days, respectively. Each chemical, sensory and microbiological results for sea bream showed us that there was a correlation and similarity, and day 9 was the beginning of spoilage. Whole ungutted sea bass stored in ice as chemical results for sea bass showed us that day 7 was the beginning of spoilage and for sea bream day 9 was the beginning of spoilage.     

Modification of poovan banana (Musa AAB) starch by γ‐irradiation: effect on in vitro digestibility,molecular structure and physico‐chemical properties

This study focussed at evaluating the effect of gamma irradiation on the in vitro digestibility, molecular structure and physico‐chemical properties of poovan banana (Musa AAB) starch using γ‐rays from a ⁶⁰Co source at different doses with a dose rate of 2 kGy h^?1. Physico‐chemical properties varied significantly and exhibited strong dose‐dependent relationship. Escalating irradiation leads to decrease in amylose content, pH, swelling power of the starch granules and syneresis of the gelatinised starch, while the same led to an increase in carboxyl content, in vitro digestibility, solubility and water absorption capacity of the starch granules. The results revealed that peak, hold, final and setback viscosities were significantly reduced. X‐ray diffraction pattern remained the same upon irradiation but a decrease in relative crystallinity was observed with increasing irradiation dose. Gelatinisation temperature and enthalpy decreased significantly when the increasing the dose of gamma irradiation.     

Effects of differences in diet and seasonal changes on the fatty acid composition in fillets from farmed and wild sea bream (Sparus aurata L.) and sea bass (Dicentrarchus labrax L.)

The effects of dietary fatty acids and seasonal variation on the fatty acid profiles of farmed and wild sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were determined by analysis of their fillets. Farmed sea bream and sea bass were fed on the same commercial feeds all year. Fatty acid profiles in the fillets reflected the fatty acid profiles of the commercial feeds. The predominant fatty acids in the trial feeds, fillets of farmed and wild sea bream and sea bass were 16:0, 18:1n‐9, 18:2n‐6, 20:5n‐3 and 22:6n‐3. The fatty acid profiles in the fillets of farmed sea bream and sea bass did not differ (P > 0.05) except in the winter season compared with those of their wild counterparts. However, the content of eicosapentaenoic acid (20:5n‐3), docosahexaenoic acid (22:6n‐3) in the fillets of the farmed and wild sea bass were significantly (P < 0.05) higher than the farmed and wild sea bream. The wild sea bream had significantly (P < 0.05) higher total saturated fatty acid and monounsaturated fatty acid (MUFA) levels, and lower total n‐6 and n‐3 polyunsaturated fatty acid (PUFA) levels in winter than in the summer and spring seasons. Similarly, in the fillets of wild sea bass, total n‐3 PUFA levels were significantly (P < 0.05) lower, and the MUFA levels were higher in winter than in the other seasons. These results indicate that the farmed fish fillets were good sources of n‐3 PUFA in each of the three seasons. However, wild fish were good sources of n‐3 PUFA in the spring and summer.     

Physico‐chemical characteristics of non‐irradiated and γ‐irradiated yams cultivars (Dioscorea rotundata,Dioscorea alata) and sweet potato (Ipomoea batatas (L) Lam)

Physico‐chemical (pasting) properties of non‐irradiated (fresh) and γ‐irradiated yam cultivars and sweet potato were determined using Rapid Visco Analyser (RVA). Generally, pasting characteristics of the commodities decreased significantly with increased γ‐irradiation dose. Non‐irradiated sweet potato showed significantly higher peak (45.79), trough (35.25), breakdown (10.54), final (75.21) and setback (39.96) viscosities (in RVU) than γ‐irradiated samples. Also, peak time (6.97 min) and pasting temperature (50.18 RVU) significantly reduced with increased γ‐irradiation dose of tubers. The pasting properties of non‐irradiated and γ‐irradiated sweet potato showed similar but clearer trend compared with yam flours. Also, non‐irradiated and γ‐irradiated Dioscorea rotundata and Dioscorea alata showed significantly higher values of each of the pasting characteristics than values noted in sweet potato. Aside from the TDr 03/00196, peak time did not vary significantly with γ‐irradiation dose.     

Purification and physicochemical characterization of ovine β‐lactoglobulin and α‐lactalbumin

Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion‐exchange chromatography and reversed‐phase high‐performance liquid chromatography (HPLC) showed the presence of two fractions of β‐lactoglobulin but only one of α‐lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)‐polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation‐mass spectrometry (ESI‐MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine β‐lactoglobulin. Amino acid compositions of the two variants of β‐lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of β‐lactoglobulin A compared to β‐lactoglobulin B at pH 2, and indicated high instability of ovine α‐lactalbumin at this pH.     

Physical,proximate, functional and pasting properties of four non‐ and γ‐irradiated bambara groundnut (Vigna subterranean) cultivars

Effect of γ‐irradiation (2–30 kGy) on physical, proximate, functional and pasting properties of four bambara groundnut cultivars was investigated. Packed (0.74–0.75 g mL^?1) and loose (0.71–0.76 g mL^?1) density varied significantly among cultivars. Generally, CIE L and hue angle decreased, while CIE a, b, deltachroma and colour intensity increased with increased dose. Protein (21.23–23.77 g/100 g), fat (6.38–7.69 g/100 g), crude fibre (1.28–3.54 g/100 g), ash (1.50–4.50 g/100 g) and moisture (10.67–12.92 g/100 g) of non‐ and γ‐irradiated bambara varied with cultivars and dose. Loose (0.41–0.49 g mL^?1) and packed (0.54–0.74 g mL^?1) densities, water absorption (1.62–2.38 g/g) and swelling (10.50–18.00 g/g) increased marginally, while oil absorption (1.93–2.82 g/g), alkaline water retention (0.66–1.23 g/g), emulsion capacity (40.31–58.23%) and stability (31.67–46.49%) decreased with increased dose. Foam capacity (6.85–22.37%) and stability (1.80–22.37%) of γ‐irradiated flours were higher than their nonirradiated (2.03–18.26%) counterparts. Nonirradiated flours showed significantly higher viscosities than their γ‐irradiated counterparts. Flours showed slightly shear‐thinning behaviours.     

Electrophoretic patterns of microwaved and γ‐irradiated beef liver proteins

The effects of γ‐irradiation treatments (2.5, 5 and 10 kGy) and microwaves generated from an oven at low and defrost power settings for 0.5, 1 and 2 min on the total proteins and protein patterns of beef liver immediately after treatment and during frozen storage (?18 °C) for different periods were studied. Chemical analyses indicated that the protein content of beef liver was reduced after exposure to γ‐radiation or microwaves and also during frozen storage. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE) was used to illustrate the changes in protein bands of different molecular weights and their percentages before and after exposure to gamma and microwave radiation. The main effect of γ‐radiation on the protein patterns of beef liver was the disappearance of some high‐molecular‐weight protein bands and the development of other bands characterised by moderate and low molecular weights. This finding indicates the degradation of beef liver proteins by γ‐irradiation. In contrast, microwave treatment caused an increase in the levels of high‐molecular‐weight protein bands with a concomitant decrease in low‐molecular‐weight protein bands. This phenomenon demonstrates the polymerisation of low‐molecular‐weight proteins under the influence of microwaves. © 2001 Society of Chemical Industry     

Evaluation of the radioprotective effect of the leaf extract of Syzygium cumini (Jamun) in mice exposed to a lethal dose of γ‐irradiation

The effects of various concentrations (5, 10, 20, 30, 40, 50, 60, and 80 mg/kg body weight (b.wt.) of the leaf extracts of Syzygium cumini Linn. and Eugenia cumini (SCE, black plum, Jamun, family Myrtaceae) on the radiation‐induced sickness and mortality in mice exposed to 10 Gy γ‐irradiation were studied. The treatment of mice with different doses of SCE, consecutively for five days before irradation, delayed the onset of mortality and reduced the symptoms of radiation sickness when compared with the nondrug‐treated irradiated controls. All doses of SCE provied protection against the gastrointestinal death increasing the survival by 66.66% after treatment with 20, 30, and 40 mg/kg SCE versus a 12% survival in the irradiated control group (oil + irradiation). Similarly, SCE provided protection against the radiation‐induced bone marrow death in mice treated with 10–60 mg/kg b.wt. of SCE. However, the best protection was obtained for 30 mg/kg b.wt. SCE, where the number of survivors after 30 days post‐irradiation was highest (41.66%) when compared with the other doses of SCE.     

Effect of soluble CO2 stabilisation and vacuum packaging in the shelf life of farmed sea bream and sea bass fillets

The objective of this study was to determine the differences of sensory, microbiological and chemical quality in vacuum-packaged fillets of sea bream and sea bass previously submitted to soluble gas solubilisation (SGS) with 100% CO₂, at 2 bar for 30 and 60 min and stored at chilled temperature for 15 days. Apart from pH value that showed a regular increase during chilled storage, the other chemical index [total volatile bases nitrogen (TVB-N), trimethylamine nitrogen (TMA-N) and thiobarbituric acid reactive substances (TBARs)] had showed to be poor indicators of changes in quality of products. Final TVB-N values ranged from 16.0 to 17.4 mg N per 100 g and from 17.3 to 19.4 mg N per 100 g in sea bream and sea bass, respectively. Sensory evaluation resulted as the most reliable parameter of quality decay. The results show that SGS treatment kept the initial quality of fillets for longer time, which was particularly visible on the sea bream fillets, thus contributing to an extension in 2–3 days of the shelf life. SGS had also a positive effect in the delay of microbial growth.     

Screening of β‐Glucosidase and β‐Xylosidase Activities in Four Non‐Saccharomyces Yeast Isolates

The finding of new isolates of non‐Saccharomyces yeasts, showing beneficial enzymes (such as β‐glucosidase and β‐xylosidase), can contribute to the production of quality wines. In a selection and characterization program, we have studied 114 isolates of non‐Saccharomyces yeasts. Four isolates were selected because of their both high β‐glucosidase and β‐xylosidase activities. The ribosomal D1/D2 regions were sequenced to identify them as Pichia membranifaciens Pm7, Hanseniaspora vineae Hv3, H. uvarum Hu8, and Wickerhamomyces anomalus Wa1. The induction process was optimized to be carried on YNB‐medium supplemented with 4% xylan, inoculated with 106 cfu/mL and incubated 48 h at 28 °C without agitation. Most of the strains had a pH optimum of 5.0 to 6.0 for both the β‐glucosidase and β‐xylosidase activities. The effect of sugars was different for each isolate and activity. Each isolate showed a characteristic set of inhibition, enhancement or null effect for β‐glucosidase and β‐xylosidase. The volatile compounds liberated from wine incubated with each of the 4 yeasts were also studied, showing an overall terpene increase (1.1 to 1.3‐folds) when wines were treated with non‐Saccharomyces isolates. In detail, terpineol, 4‐vinyl‐phenol and 2‐methoxy‐4‐vinylphenol increased after the addition of Hanseniaspora isolates. Wines treated with Hanseniaspora, Wickerhamomyces, or Pichia produced more 2‐phenyl ethanol than those inoculated with other yeasts.