Functional and antioxidative properties of protein hydrolysates from Cape hake by‐products prepared by three different methodologies

BACKGROUND: The production of fish protein hydrolysates (FPH) is a convenient technology for upgrading fish by‐products. The aim of this work was to study three different methods of FPH preparation from Cape hake by‐products to improve yield and quality. Functional and antioxidative properties of all FPHs were determined. RESULTS: The protein content of hake FPH was in the range 807–860 g kg^?1 and the degree of hydrolysis was between 19% and 22%. The maximum yield (71.9%) was achieved by methodology B but the hydrolysate was darker. The peptide profile of all FPHs was very similar. FPH prepared by methodology C had significantly higher emulsifying activity index and hydrolysate prepared by methodology B had the highest foaming capacity. The solubility of FPH was in the range 71–76% and increased the water‐holding capacity of minced fish by about 9%. The fractionation of FPH obtained by methodologies A and B allowed concentrating peptides with higher radical scavenging activity and reducing power. CONCLUSION: The properties of the FPH prepared indicated that they can be used in food systems as natural additives, particularly to improve their water‐holding capacity. © 2012 Society of Chemical Industry     

Supercritical CO2-assisted preparation of a PMMA composite membrane for bisphenol A recognition in aqueous environment

This work reports a novel strategy to prepare affinity composite membranes using supercritical fluid technology. By blending molecularly imprinted polymeric particles with PMMA, a porous hybrid structure with affinity to the template molecule, bisphenol A, was prepared using a supercritical carbon dioxide (scCO₂)-assisted method. Membranes were characterized in terms of morphology, mechanical performance and transport properties. The ability of the polymers and hybrid membranes to adsorb bisphenol A was tested in aqueous solutions and fitted to a linearized Langmuir equation, showing that adsorption takes place at homogeneous affinity binding sites within the imprinted surface. Filtration experiments showed that the imprinted hybrid membrane was able to adsorb higher amounts of template even in non-equilibrium dynamic binding conditions. The hybridization of the PMMA membrane herein reported conveys two important improvements over neat PMMA membrane: it introduced molecular affinity towards the template molecule and significantly increased the permeability of the porous structures, which are key parameters in processes that involve membranes. This technique could expand the applications of polymeric beads powders and enhance the efficiency of the membrane's transport properties. Our work presents a new method to confer affinity to a porous structure by immobilization of imprinted polymers, combining polymer synthesis and membrane formation using supercritical fluid technology.     

Structural/textural properties and water reactivity of fluorinated activated carbons

Hydrophobic activated carbons are considered as interesting materials for air or water remediation due to their enhanced affinity for slightly water-soluble organic species. In this context, a commercial activated carbon, in an extruded form, was fluorinated under mild conditions (pure fluorine gas at room temperature) in order to decrease its hydrophilic character and to preserve its microporosity. For comparison, a hydrogenated activated carbon was also prepared by H₂ treatment. The resulting samples were characterised by various techniques in order to determine the evolution of the activated carbon materials in terms of composition (XPS, elemental analysis, TGA and NMR) and porosity (nitrogen physisorption (77 K), mercury intrusion and immersion calorimetry). For the fluorinated carbon, the nature of the CF_x groups and the strength of the C–F bonds were also investigated using ¹³C and ¹⁹F solid state NMR and TGA techniques. A labile character of the C–F bond, so far exclusively observed for fluorine intercalation compounds, is also shown for the first time for a fluorinated activated carbon by water adsorption/desorption isotherms at room temperature. Care should then be taken for its use in presence of water.     

Effects of polymerization catalyst technology on the melt processing stability of polyethylenes. part 2. single stabilizer performance

The effects of a range of thermal and light stabilizers on the melt stability (investigated via multiple pass extrusion) and color stability of three different polyethylenes (PEs) were examined. The PEs varied in terms of the catalyst system used to synthesize the polymers and included an HDPE produced by using a chromium‐based Phillips catalyst and two LLDPEs produced via chromium‐based metallocene and titanium‐based Ziegler‐Natta catalysts. The additive types included a range of phenolics of different functionality, phosphites, hindered piperidines, an hydroxylamine, and Vitamin E. The results obtained for the three PEs confirmed that primary antioxidants (AOs) such as highly hindered and less, hindered phenols or hydroxylamines promoted good melt stability but in some cases tended toward yellowing. The secondary AOs such as the phosphites or thioethers behaved in the opposite way; color suppression was good, but melt stabilization was poor. It was also shown that for different types of phenols (all with similar molar activity), reducing steric hindrance to the phenolic OH enhanced the tendency to form chromophoric groups and hence color led to better efficiency than high hindrance. Those phenol with higher molar activity (mol OH/kg AO) showed the best processing performance. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Effects of addition of different vegetable oils to lactating dairy ewes' diet on meat quality characteristics of suckling lambs reared on the ewes' milk

The effect of different vegetable oils used in the diet of lactating ewes on the meat quality of their suckling lambs has been evaluated. Lambs (males and females) were slaughtered at 11 kg. Fortyeight lactating Churra ewes (prolificacy 1.5) and their suckling lambs were assigned to four treatments according to the oil added (3% on weight basis) to the ewes' daily ration: palm oil as control (CON); olive oil (OLI); soybean oil (SOY); and linseed oil (LIN). Analyses of pH, colour, thiobarbituric acid reactive substances (TBARS), tocopherol levels, volatile compounds and a sensory evaluation were carried out on suckling lambs' meat. Results showed no substantial effect on pH, colour, TBARS and tocopherol levels. Volatiles typically derived from lipid oxidation were higher in SOY group. However, panellists were only able to correctly identify samples from LIN group. Furthermore, the meat from LIN group showed lower scores towards odour and flavour quality and overall liking than that from the rest of treatments.     

Effect of Curing Method and Freeze-Thawing on Subsequent Growth of Listeria monocytogenes on Cold-Smoked Salmon

The presence of the foodborne pathogen Listeria monocytogenes on cold-smoked salmon is a major concern for the seafood industry. Understanding processing and postprocessing handling factors that affect the ability of this pathogen to grow on cold-smoked salmon is critical for developing effective control strategies. In this study, we investigated the effect of curing method and freeze-thawing of cold-smoked salmon on (i) physicochemical properties and (ii) subsequent growth of genetically diverse strains of L. monocytogenes (inoculated after freeze-thawing) and endogenous lactic acid bacteria. The majority of the measured physicochemical properties were unaffected by freezing and thawing. Overall, wet-cured cold-smoked salmon had higher pH, water activity, and moisture, as well as lower fat, water-phase salt, and phenolic content compared with dry-cured cold-smoked salmon. The curing method and freeze-thawing did not affect growth of endogenous lactic acid bacteria. Freeze-thawing cold-smoked salmon prior to inoculation led to pronounced growth of L. monocytogenes at 7°C. The increase in cell density between days 0 and 30 was significantly (P = 0.0078) greater for cold-smoked salmon that was frozen and thawed prior to inoculation compared with nonfrozen cold-smoked salmon. On dry-cured, freeze-thawed cold-smoked salmon, L. monocytogenes had a lag phase ranging from 3.7 ± 0.1 to 11.2 ± 1.4 days compared with salmon that was wet cured and freeze-thawed, on which L. monocytogenes began to grow within 24 h. Variation in growth among L. monocytogenes strains was also observed, indicating the significance of assessing multiple strains. Further efforts to understand the impact of processing and postprocessing handling steps of cold-smoked salmon on the growth of genetically diverse L. monocytogenes will contribute to improved challenge study designs and data. This, in turn, will likely lead to more reliable and unbiased risk assessments and control measures.