Changes in chemical composition and nutritional quality of fried sardine (Clupea pilchardus) produced by frozen storage and microwave reheating

Modifications in proximate composition, fatty acids, amino acids and –SH groups content, as well as changes in solubility and nutritional quality of protein, were studied in fillets of sardine (Clupea pilchardus) that had been successively pan-fried, frozen stored and reheated by two different means, namely conventional oven and microwave oven. Upon pan-frying in olive oil the sardine absorbed C18: 1(n-9) and C18: 2(n-6) and lost saturated (SFA) and polyunsaturated fatty acids (PUFA); this loss continued upon reheating, and as a consequence the percentage of MUFA increased compared to the just-fried sardine. A loss of water was observed during all processes. Upon frying there was a decrease of cyst(e)ine. Upon reheating by both microwave and conventional oven, methionine decreased; however, cyst(e)ine only decreased with the use of a conventional oven. A loss of –SH groups was recorded during frying and this phenomenon continued upon reheating. Biological value (BV) together with net protein utilisation (NPU) decreased upon both frying and reheating. © 1997 SCI.     

Physical,chemical and sensory analysis of sardine (Sardina pilchardus) stored in ice

The shelf-life of iced sardine (Sardina pilchardus) was studied. The main changes which take place in raw fish were investigated by means of organoleptic assessments, chemical analyses (total volatile nitrogen (TVB-N), trimethylamine (TMA-N), trimethylamine oxide (OTMA-N) and hypoxanthine) and physical measurements (GR Torrymeter readings and pH). The influence of both seasonal changes and fat deterioration were also considered. The results obtained indicate that TVB-N and TMA-N parameters are not good freshness indicators for this species, but Torrymeter readings and hypoxanthine values can be used as indicators of freshness. However, they must always be confirmed by a sensory evaluation. From the different combinations tried, the most highly significant degree of correlation was obtained between sensory evaluation and Torrymeter readings.     

Effects of novel modified atmosphere packaging on lipid quality and stability of sardine (Sardina pilchardus) fillets

Modified atmosphere packaging (MAP) is an efficient method to increase shelf-life of fishery products by inhibiting bacterial growth and oxidative reactions. Beside the traditional gases used for MAP, novel gases such as argon (Ar) and nitrous oxide (N₂O) were approved for food use in the European Union. The present research investigates the effect of MAP with unconventional gas mixtures, that previously positively affected microbial shelf-life, on colour, lipid oxidation and sensorial characteristics of sardine fillets during storage. Four atmosphere conditions were tested: Air (20.8% O₂/79.2% N₂), N₂ (30% CO₂/70% N₂), N₂O (30% CO₂/70% N₂O) and Ar (30% CO₂/70% Ar). Samples were stored for 12 days at 3 °C. Results showed that the removal of oxygen significantly inhibited the oxidation process; however, most of the investigated parameters related to fat oxidation did not show any improvement, except for a slight decrease in lipid hydrolysis and improvement in sensory properties in the packaging containing Ar.     

Effects of rosemary and sage tea extract on biogenic amines formation of sardine (Sardina pilchardus) fillets

Natural antimicrobials and antioxidants from rosemary (Rosmarinus officinalis) and sage tea (Salvia officinalis) were produced using solvent extraction method. The effect of two extracts on ammonia (AMN) and biogenic amines (BAs) formation in vacuum packed sardine (Sardina pilchardus) fillets stored at 3 ± 1 °C was investigated for 20 days. Although the effect of extracts was dependent on specific amine and storage time, phenolic compounds from rosemary and sage tea generally resulted in lower AMN and BAs accumulation in sardine muscle. Putrescine (PUT) and cadaverine (CAD) were the most abundant amines, while histamine (HIS) concentration ranged from 2.05 to 28.77 mg 100g^?1. Rosemary and sage tea extracts significantly reduced HIS, PUT, CAD and trimethylamine accumulation in the fish muscle (P < 0.05) while stimulating effect of extracts was observed on serotonin and agmatine formation. At the end of the storage period, PUT and CAD contents of control were 100‐fold higher than those of treated groups.     

Influence of texture of suwari gels on kamaboko gels made from sardine (Sardina pilchardus) surimi

The textural characteristics and water holding capacity of suwari (set) and kamaboko (set and cooked) sardine surimi gels were examined in order to clarify the influence of the initial network formed in setting conditions (25, 35 and 40°C for 30 and 60 min) on the texture of the kamaboko gels. Although the texture of suwari gels set at 35°C improved with longer setting, both setting times ensured kamaboko gels with the highest gel strength. Suwari gels set at 25°C also improved with longer setting but the gel strength of both suwari and kamaboko gels was lower than at 35°C. For gels set at 40°C prolonged setting weakened the suwari networks formed, leading to kamaboko gels with poorer textural characteristics. ©1997 SCI     

The presence of bioactive peptides in hydrolysates prepared from processing waste of sardine (Sardina pilchardus)

A proteolytic enzyme, Alcalase®, was used to produce partly digested proteins from cooked wastes of sardine (Sardina pilchardus). The presence of biologically active molecules was investigated in these hydrolysates prepared under various conditions of time and enzyme/substrate ratio. By means of radioimmunoassays and mitogenic and radioreceptor assays, the presence of molecules related to secretagogue peptides, growth factors and calcitonin gene‐related peptide (CGRP) respectively was detected in the hydrolysates. Exclusion chromatography permits the conclusion that the biological activity of the different fractions is related to their size. © 2001 Society of Chemical Industry     

Optimization of hydrolysis of sardine (Sardina pilchardus) heads with Protamex: enhancement of lipid and phospholipid extraction

BACKGROUND: Fish by‐products are not considered as valuable raw materials even if they usually contain valuable components such as lipids. Fish lipids are well known for their nutritional potential and health effects but their extraction remains problematic due to the use of organic solvents. Enzymatic hydrolysis such as the proteolysis of tissues can lead to lipid extraction. RESULTS: Hydrolysis of sardine heads by Protamex was studied (temperature, hydrolysis time and enzyme–substrate ratio) using response surface methodology in order to obtain the highest release of lipids and particularly phospholipids. No relation between the degree of hydrolysis and lipid recovery were depicted; however, optimum conditions for both the release of lipids and phospholipids were found to be similar (29 min, 31 °C with 2.6 g kg^?1 enzyme). Under these hydrolysis conditions, rich lipid and phospholipid fractions (oily and aqueous fractions) can be recovered when time, temperature and enzyme consumption are minimized. Analytical data have revealed that they contain high‐quality lipids, especially ω3 fatty acid. CONCLUSION: This study demonstrated that proteolysis can be used for high lipid recovery from little‐exploited biomass like fish heads without requiring solvent or thermal treatment. Resulting phospholipids, fatty acids and peptides could be utilized for nutritional or feed purposes. Copyright © 2009 Society of Chemical Industry     

Influence of Frozen Storage and Defrosting on the Chemical and Nutritional Quality of Sardine ((Clupea pilchardus)

Studies were carried out on the changes in solubility in SDS+β-mercaptoethanol, the –SH group content, the amino acid and the fatty acid compositions, and nutritional quality of the muscle protein following freezing, storage at −20°C and conventional defrosting of sardines ( Clupea pilchardus ). During the processes, 8% of the total SH– group content was lost and there was a slight drop in solubility in SDS+β-mercaptoethanol. The amino acids which dropped to the greatest extent were the S-amino acids, followed by histidine, tyrosine, leucine, lysine and phenylalanin. The C22:6/C16:0 ratio dropped and this was considered to be related to oxidation phenomena. The digestibility of protein, biological value and net protein utilization (NPU) also dropped as a result of the processes studied.     

The effects of soluble gas stabilisation on the quality of packed sardine fillets (Sardina pilchardus) stored in air,VP and MAP

Sardine (Sardina pilchardus) is a species that for its abundance assumes great importance in the Portuguese fishing sector. In order to contribute for a better utilisation of this species, the aim of this study was to investigate the effect of the pre‐treatment with soluble gas stabilisation (SGS) (100% CO₂ at 2 bar, during 15 and 30 min) on the quality and shelf‐life of sardine fillets, packed in air (AP), vacuum (VP) and modified atmosphere (MAP: 5% O₂/35% CO₂/60% N₂). During the chilled storage, the quality changes were evaluated by sensory evaluation, chemical and microbiological analysis. The total volatile basic nitrogen content remained almost constant, between 16 and 19 mg N/100 g muscle, during the storage period, for all samples. The TBARs values increased with storage time, for all batches and storage conditions. The application of SGS treatment to sardine fillets, resulted in a bacteriostatic effect, contributing to the improvement of the microbiological quality of fillets. Considering a sensory criteria, the shelf‐life of SGS pre‐treated sardine fillets was found to be 5 days in AP and MAP while in VP‐treated fillets a shelf‐life of 8 days was reported. At sensory rejection, sardine fillets presented a K‐value of 30% in AP and MAP batches and 40% in VP batch.     

Enzymatic oxidative activity in sardine (Sardina pilchardus) and herring (Clupea harengus) during chilling and correlation with quality

 Enzymatic oxidative activity of two fatty fish species, sardine (Sardina pilchardus) and herring (Clupea harengus), was studied during chilled storage. Lipoxygenase enzyme activity was isolated and tested by measuring the hydroperoxides produced after induced oxidation of arachidonic and docosahexaenoic fatty acids. The most abundant degradation products of the hydroperoxides formed were 12- and 16-hydroxy acids which were detected by HPLC. Lipoxygenases were concentrated in the skin tissue of fish, and were active for up to 48 h of chilled storage. The pro-oxidative activity due to haem proteins continued for longer than that due to lipoxygenase. Trends of fluorescent formation resulting from interaction between oxidation products and biological amino constituents were compared with the pro-oxidative activities to establish correlations with quality loss during chilling. Received: 29 December 1998 / Revised version: 14 March 1999     

Acceptability of diets containing olive oil fried sardines (Sardina pilchardus) in the prevention of dietary hypercholesterolaemia in rats

Garlic (Allium sativum L) bulb explants produced undifferentiated white globular callus when grown on MS medium having 2,4-dichlorophenoxy-acetic acid (2,4-D) and Kinetin (Kn). Such callus when grown on medium having indole-3-yl-acetic acid (IAA) and/or Kn developed into the differentiating callus which had comparatively more allicin than that of undifferentiated callus. The effect of sucrose, NH/NO ratios and hormone concentrations on growth and allicin development in the callus was investigated. There was a significant increase in allicin development in callus when grown for up to 4 weeks on medium (a) having sucrose at 3% and 5% levels; (b) having NH and NO ratios at 2:1 and 1;1; and (c) with Kn alone at a concentration of 0.5 mg litre^?1, which produced a tenfold increase in allicin content.     

Sunflower oil versus olive oil and iron metabolism in rats. Influence of a frying process

Olive oil and sunflower oil were used in repeated potato‐frying operations without turnover until the oils reached the limit of 25% polar compounds allowed by law. Over a 28 day period, five groups of rats were fed diets containing 8% unused olive oil, olive oil used in 48 and 69 potato frying operations, unused sunflower oil and sunflower oil used to fry potatoes 48 times. In the final week, faeces and urine were collected and, on day 28, animals were sacrificed. The type of oil, unused or used in frying, did not modify food intake, body weight, faecal iron and its apparent absorption or retention, but consumption of oils used in frying tended to increase urinary iron excretion. No differences were found in serum iron, total iron‐binding capacity and haemoglobin values. Iron contents and concentrations in liver, spleen and skin did not vary between groups. Iron concentrations in erythrocytes were significantly higher in rats fed sunflower oil, either unused or used in frying. It was concluded that the consumption of sunflower oil compared to olive oil could affect intra‐ and extracellular haematic distribution of iron, probably associated with changes in membrane permeability, and that some alteration products of the oils originated during frying tend to increase urinary iron losses without repercussions on iron metabolism. © 2000 Society of Chemical Industry     

Effects of rosemary and sage tea extracts on the sensory,chemical and microbiological changes of vacuum‐packed and refrigerated sardine (Sardina pilchardus) fillets

The effect of the natural antioxidants and antimicrobials from ethanol extracts of rosemary and sage tea on sensory, chemical [Total volatile basic nitrogen (TVB‐N), thiobarbituric acid reactive substances (TBARs), peroxide value (PV), free fatty acid (FFA)] and microbiological (total viable count‐TVC and total coliform count) changes of vacuum‐packaged sardine (Sardina pilchardus) fillets stored at 3 ± 1 °C was investigated for 20 days. The fish fillets were divided into three groups: untreated group (control, C) and treated groups that were immersed in a 1 L of distilled water containing 10 g rosemary (R group) or sage tea (S group) extracts for 4 min. The shelf life of sardine fillets was found to be 13 days for control (C), 20 days for R and S groups according to sensory assessment results, whose corresponded microbiological assessment showed a shorter shelf life (5 days for C group, 9 for R and S groups). At the end of storage period, TBARs values were 0.98 mg malonaldehyde kg^?1 for C group, 0.66 malonaldehyde kg^?1 for R group and 1.44 mg malonaldehyde kg^?1 for S group. Microbiological results showed that natural compounds from rosemary and sage tea resulted in a lower bacterial growth in fish fillets during the storage period.     

Impact of the frying temperature on protein structures and physico-chemical characteristics of fried surimi

In this work, protein structures and properties and physico-chemical characteristics of surimi fried at different temperatures were studied. The effect of frying on surimi protein structure was characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), intrinsic fluorescence, surface hydrophobicity, intermolecular interaction and Fourier transform infrared spectroscopy (FT-IR). SDS-PAGE analysis observed the appearance of new peptide bands and the weakening of myosin heavy-chain and actin bands after frying. In addition, frying damaged the hydrogen bond and ionic bond but promoted formation of the disulphide bond. Moreover, β-sheet and random coil were increased after frying, while α-helix and β-turn were decreased. After frying, the surface hydrophobicity of fried surimi decreased and the fluorescence maximum emission wavelength showed a red shift. The above changes indicated occurrence of protein denaturation and degradation, which were dependent on the frying temperature. Moreover, the effect of the frying temperature on physicochemical properties of fried surimi was characterised by measuring the hardness, oil absorption, porosity and water absorption capacity of fried surimi. The moisture loss, oil uptake, porosity and water absorption capacity of the fried surimi increased gradually with the frying temperature. However, the hardness of fried surimi was not positively correlated with the frying temperature but strongly dependent on the porous structure. These results showed that the physico-chemical properties of the fried surimi were dependent on not only degree of protein denaturation but also the porous structure.     

Quality assessment of whole and gutted sardines (Sardina pilchardus) stored in ice

The quality and shelf life of whole ungutted and gutted sardines ( Sardina pilchardus ) stored in ice were studied. The changes in the fish were investigated by sensory assessments, chemical analyses and microbiological analyses. The sensory scores of uneviscerated and gutted sardines stored in ice at +4 °C were 7 days. The chemical indicators of spoilage, total volatile basic nitrogen and trimethylamine values of gutted sardine increased very slowly, whereas for whole ungutted samples higher values were obtained reaching a final value of 15.03–29.23 mg per 100 g and 2.36–4.16 mg per 100 g, respectively (day 9). Peroxide and thiobarbituric acid values remained lower for whole ungutted sardine samples until day 9 of storage, whereas for gutted fish were higher. The level of histamine exceeded the legal limit in whole ungutted sardine after 7 days of storage in ice, during which sardines were rejected by the sensory panel. Mesophilic aerobic bacteria count, H₂S-producing bacteria, sulphide reducing anaerobe Clostridias, Enterobacteriaceae count of whole ungutted sardine samples are higher than gutted sardine samples during the storage. Psychrotrophic bacteria counts of the two groups were not different. The limits of microbiological data were not exceeded throughout the storage in both the groups' samples.     

Zinc and iron bioavailability of genetically modified soybeans in rats

ABSTRACT:  The aim of this work was to evaluate zinc and iron bioavailability of UFV-116, a new variety without 2 lipoxygenases, with better taste and flavor than a commercial variety OCEPAR 19, containing all 3 isozymes. To evaluate zinc absorption using ⁶⁵Zn whole body retention and femur ⁶⁵Zn uptake, rats were given 3 g of a ⁶⁵ZnCl₂ labeled test meal (0.25 μCi). The 2 varieties were tested at the level of 9 and 30 ppm of zinc as defatted soy flour. Two other groups (control) received egg white as source of protein and ZnS0₄.H₂0 as the zinc source. To evaluate iron absorption, using ⁵⁹Fe whole body retention, animals were given a 3 g ⁵⁹FeCl₃ labeled test meal (0.2 μCi). The 2 varieties were tested at 12 and 25 ppm iron as defatted soy flour. Whole fat soy flour of variety 1 (UFV-116) was higher ( P < 0.05) in Ca, K, Mg, phytic acid, and oxalate than variety 2 (OCEPAR-19). No difference was observed among the soybean varieties ( P > 0.05) for femur ⁶⁵Zn retention, at different levels of zinc. However, whole body retention was lower ( P < 0.05) for UFV-116 than for OCEPAR-19. Femur ⁶⁵Zn uptake was correlated with the whole body retention; however, whole body retention was more sensitive. Whole body ⁵⁹Fe retention from UFV-116 was lower ( P < 0.05) than from OCEPAR-19. Zinc and iron bioavailability was lower for UFV-116, possibly due to its higher content of antinutrient factors, especially phytate.     

Influence of the degree of hydrolysis on the solubility of the protein hydrolysates from sardine (Sardina pilchardus)

The influence of different degrees of hydrolysis on the solubility of sardine proteins and on its correlation with the molecular weight distribution of the protein hydrolysates was examined. All the hydrolysates showed high solubility with a more pronounced reduction for products with a lower degree of hydrolysis in acid pH at both high and low ionic strength. Furthermore, from the gel-chromatographic analysis, a decrease was noted in the high molecular weight fraction as the degree of hydrolysis increased.     

Effects of endogenous and exogenous corn protein and its hydrolysates on the structural change and starch digestibility of fried corn starch

Frying could lead to deformation of starch granules and significant reduction in their internal crystalline structure. All of these changes could lead to rapid digestion of fried starch. The addition of corn protein and its hydrolysate to samples prior to frying can reduce the structural change of the granules and also increase their crystallinity and thermostability. Besides, both corn protein and its hydrolysates showed potent abilities in mitigating starch digestion. The fractions of slowly digestible starch and resistant starch increased significantly after the addition of corn protein or its hydrolysate. Meanwhile, the effect of removal of endogenous protein on fried starch was also examined. The results showed that, after removing the protein, starch granules were severely disintegrated during frying; most importantly, the digestibility of starch was increased significantly. The mitigating effect on corn starch digestion could be attributed to structural changes in the ordered structure and suppression of enzyme activities.