Chemical, Microbiological, and Sensory Quality of Cod Products Salted in Different Brines

ABSTRACT: Studies were carried out on the effect of different brines containing high concentrations of calcium chloride (CaCl₂, 0.8%w/w), magnesium chloride (MgCl₂, 0.4%w/w), and potassium chloride (KCl, 50%) on the chemical (chloride and moisture contents), microbial (total viable counts, total coliforms, enterococci, and staphylococci), and sensory quality of salted cod. The brines were prepared from combinations of the Ca, Mg, and K ions and sodium chloride (NaCl) at pH 6.5 and 8.5. Additionally, 3 salts (one composed solely of NaCl, another commercial sea salt from the southern Europe and, finally, a natural salt from northern Europe) were also tested. Principal component analysis structured the chemical and microbiology data in 3 clusters: (1) an extreme cluster, formed by cod brined in the commercial sea salt, which achieved the highest microbiological counts, namely 4.1 log CFU/g on plate count agar (PCA) and 1250 coliforms/g; (2) an intermediate cluster composed of cod salted in brine containing 50% NaCl, 0.4% MgCl₂, and 49.6% KCl (pH 6.5); and (3) a central cluster, including all the other treatments, which presented the lowest microbiological counts, namely 2.4 log CFU/g on PCA and 20 coliforms/g. Although the batches of the intermediate cluster presented slightly higher total viable and staphylococci counts than the central cluster, the presence of Mg and K ions improved the color of the salted product. In the assayed concentrations, CaCl₂, MgCl₂, and KCl can be used in the brining of cod without adversely affecting the microbiological and sensory quality of the salted cod.     

Chemical composition and nutritional value of raw and fried allis shad (Alosa alosa)

The main objective of this study was to compare the proximate chemical composition and fatty acid profile of migrating allis shad (MS) and resident allis shad (RS) and to evaluate the nutritional value of fried migrating allis shad. No significant differences in the proximate chemical composition between males and females of each stock were obtained. However, MS fish had a significantly higher fat content than RS fish. The monounsaturated fatty acids group was the dominant in MS fish and oleic acid presented the highest percentage. Docosahexaenoic acid followed by eicosapentaenoic acid were the main PUFA in fish from both stocks. However, RS fish had higher total ω6 than MS fish due to its higher percentage of linoleic acid and arachidonic acid. Frying resulted in a significant reduction in water content and affected significantly the proximate chemical composition and the fatty acid profile, particularly the palmitic, oleic and linoleic acid.     

Antioxidant synergy of α-tocopherol and phospholipids

The prevention of oxidation of a refined sardine oil by α-tocopherol at 0.04%, by several phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cardiolipin (CL)] at 0.5%, as well as by combinations of α-tocopherol with each phospholipid, was investigated. The evolution of the oxidation process during 1 mon at 40±2°C was followed by a series of methods, measuring peroxide value (PV), diene, triene, and polyene index, and absorbance at 430 nm, while α-tocopherol and phospholipid content were being monitoried. Among these indices, PV was found to be the most adequate to follow the process. PC was the most effective individual antioxidant as shown by the PV values obtained at the end of the storage period, which were 54.0, 83.4, 87.9, and 97.7 meq O₂/kg for PC, CL, PE, and α-tocopherol, respectively. The highest synergistic effect was obtained with a mixture of α-tocopherol and PE, and the second and third best by mixtures made with PC and CL, respectively. The corresponding PV values recorded at the end of the period were 27.0, 35.0, and 58.0 meq O₂/kg. The high degree of synergy between PE and tocopherol is probably due to the occurrence of a simultaneous antioxidant mechanism involving Maillard compounds.     

The role of marine omega-3 in human neurodevelopment,including Autism Spectrum Disorders and Attention-Deficit/Hyperactivity Disorder – a review

Abstract

Autism Spectrum Disorders (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) are two increasingly prevalent neurodevelopmental disorders. This rise may be associated with a higher dietary intake of n-6 polyunsaturated fatty acids (PUFAs) and lower of n-3 PUFAs. Docosahexaenoic acid (DHA), a key nutritional n-3 PUFA, is crucial for an optimal offspring’s neurodevelopment through the last trimester of pregnancy. Recently, lower DHA levels have been reported in children with ASD and ADHD. The present review summarizes the main research achievements concerning the effect of DHA in children neurodevelopment, in order to elicit its role in the prevention and mitigation of ASD and ADHD. As main finding, a low DHA supply seems to negatively affect childhood neurodevelopment in specific conditions and increase the risk and the severity of ASD or ADHD. Higher DHA status at birth was associated with better childhood neurodevelopmental, but controversial results found in prenatal supplementation raised the hypothesis that the benefits of DHA may be influenced by other factors as socio-economic background and life-style. In conclusion, an optimal DHA provision through maternal diet or breastfeed may promote some neuronal protection in specific offspring’s populations, suggesting that DHA may act as a modifiable risk factor for ASD and ADHD.     

Fatty Acid Profile of Pacific Oyster,Crassostrea gigas,Fed Different Ratios of Dietary Seaweed and Microalgae during Broodstock Conditioning

The fatty acid (FA) profile of oysters generally reflects the dietary FA composition. Moreover, incorporation of FA into tissues is modulated by various metabolic factors, and final composition will depend upon the dietary sources, cumulative intake, and oysters' development stage. Thus, the aim of this study was to assess the impact of dietary incorporation of seaweed (SW) Ulva rigida, in replacement of traditional microalgae diet, on the FA composition of Pacific oysters Crassostrea gigas, during broodstock conditioning. The dietary conditioning consisted of direct replacement of microalgae (33% Tisochrysis lutea, 50.25% Skeletonema costatum, and 16.75% Chaetoceros calcitrans) by SW at four different substitution levels (0%, 25%, 50%, and 100% diet). The dietary docosahexaenoic acid (DHA) (22:6n-3) and eicosapentaenoic acid (EPA) (20:5n-3) contents showed a positive correlation with the dietary microalgae level. During the trial, oysters fed with higher percentages of microalgae revealed a depletion of DHA and accumulation of EPA. The 100% SW caused a significant reduction in oxygen consumption and, consequently, in the standard metabolic rate. Based on these results, a partial substitution of up to 25% of dietary microalgae seems to be a suitable alternative, because it elicited similar results to the commercial 100% microalgae diet.     

Effect of a vacuum-leaching technology on the proteins and lipids of lean sardine (Sardina pilchardus) mince

A study on the effect of the vacuum level and leaching time on the washing of lean sardine (Sardina pilchardus) mince was carried out. An experimental design was performed according to the statistical model of central composite design of response surface methodology. Proximate composition, water-holding capacity (WHC) and soluble protein were determined in the mince. Lipid classes and fatty acids were further analysed in the minces and in the extracted solutions. The WHC was greatest in the mince washed at atmospheric pressure for 40 min, and corresponded to the lowest fat content. The highest soluble protein extraction was obtained at intermediate values of pressure (382 mmHg) and time of washing (20 min). The fat initial content (4.6 %) was reduced by approximately 50% and was significantly affected by extreme vacuum levels (4 mmHg and 760 mmHg) and longer washing periods. Triacylglycerols were extracted the most, mainly at intermediate pressure values and increased washing periods. Polar lipids were next in abundance and were not extracted during washing. Polyunsaturated fatty acids were the major group of fatty acids, with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) the most representative, being predominantly extracted at extreme pressure levels and increased periods of washing. DHA was more abundant in the washed mince, whereas the level of EPA was proportionally higher in the emulsions.     

Flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures

A comprehensive review of flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures is presented in this paper. First, various parameters influenced by the lubricant oil in convective boiling of refrigerants, such as mass velocity, vapor quality, oil concentration and geometric characteristics of the heat transfer tube are discussed. The effects of the unavoidable introduction of the lubricant oil on the thermodynamics properties of a refrigerant are described. Then, a review of the main experimental studies of flow boiling of refrigerant/lubricant oil mixtures is presented and also describes research with halocarbons, carbon dioxide, hydrocarbons and ammonia. There is no agreement among these studies regarding the effect of the oil in the evaporator, with studies showing an increase or decrease in the heat transfer coefficient. However, in relation to pressure drop, all the results presented the same trend, increasing the pressure drop with increasing oil concentration. Next, the flow patterns of refrigerant/oil mixtures are illustrated together with a selection of video images. It is possible to notice the difference in frothing formation with respect to the particular refrigerant and tube geometry. Some predictions of oil effects on the heat transfer coefficient and pressure drops based on the mixture physical properties are then presented and the trends compared to data. Finally, some suggestions for future work are given.     

Convective boiling performance of refrigerant R-134a in herringbone and microfin copper tubes

This paper reports an experimental investigation of convective boiling heat transfer and pressure drop of refrigerant R-134a in smooth, standard microfin and herringbone copper tubes of 9.52 mm external diameter. Tests have been conducted under the following conditions: inlet saturation temperature of 5 °C, qualities from 5 to 90%, mass velocity from 100 to 500 kg s⁻¹ m⁻², and a heat flux of 5 kW m⁻². Experimental results indicate that the herringbone tube has a distinct heat transfer performance over the mass velocity range considered in the present study. Thermal performance of the herringbone tube has been found better than that of the standard microfin in the high range of mass velocities, and worst for the smallest mass velocity (G=100 kg s⁻¹ m⁻²) at qualities higher than 50%. The herringbone tube pressure drop is higher than that of the standard microfin tube over the whole range of mass velocities and qualities. The enhancement parameter is higher than one for both tubes for mass velocities lower than 200 kg s⁻¹ m⁻². Values lower than one have been obtained for both tubes in the mass velocity upper range as a result of a significant pressure drop increment not followed by a correspondent increment in the heat transfer coefficient.     

Optimisation of oil extraction from sardine (Sardina pilchardus) by hydraulic pressing

The aim of this study was to evaluate the influence of the processing conditions (pretreatment temperature: 5–55 °C, pressure: 60–120 bar and number of pressing stages: 1–3) on the yield and quality (free fatty acids, peroxide value, p‐anisidine and Rancimat induction period) of the oil extracted from whole sardine by hydraulic pressing. Experimental factors were investigated by a designed experiment and optimised by response surface methodology. A maximum yield of oil, 12.47%, was obtained at 55 °C, 60 bar and two pressing stages. Regarding oil quality, it was found minimum values for acidity (0.25% oleic at 55 °C, 60 bar and one pressing stage) and for peroxide value (0.29 meq kg^?1 oil at 5 °C, 60 bar and one pressing stage). Hence, the opposite effect of pretreatment temperature and number of pressing stages on the yield of oil and on its oxidation parameters suggested applying the weighted‐sum method as multiobjective optimisation technique.