Study on Textural, Microbial and Sensory Quality of Blast Frozen Pangasius Fish Fillets Under Frozen Storage

AbstractPangasius fish is one of the rapid growing fresh water species in aquaculture. This study was aimed to assess the microbial number, physical quality and sensory evaluation of the Pangasius fish fillets from Nepal. Pangasius fish were collected from Chitwan and Nawalparasi districts, fillets were prepared and blast frozen simultaneously. The microbial number decreased rapidly during storage in frozen condition while Staphlylococcus aureus and Escherichia coli (which were present initially in fillets) disappeared during storage. The sensory panellists preferred air blast frozen fillets stored for one month than stored for two months. Different parts of the fish body showed different textural properties. Hardness was increased during second month of storage while other textural properties were found satisfactory in first month of storage in frozen condition. This study showed that sensory qualities of air blast frozen Pangasius fish fillets changes with time even in frozen storage.Keywords: fillet, microbial number, Pangasius, sensory, texture AbstrakIkan Pangasius adalah salah satu spesies ikan air tawar yang dapat tumbuh cepat saat dibudidayakan. Penelitian ini bertujuan untuk menilai kualitas mikroba, kualitas fisik, dan evaluasi sensorik fillet ikan Pangasius di Nepal. Ikan Pangasius didapatkan dari daerah Chitwan dan Nawalparasi kemudian dibuat fillet dan dibekukan secara langsung. Jumlah mikroba menurun drastis saat penyimpanan dalam kondisi beku, sedangkan Staphlylococcus aureus dan Escherichia coli (yang memang ada di bahan sejak awal) tidak ada selama penyimpanan. Panelis sensoris lebih memilih fillet ikan dengan pembekuan air blast yang disimpan selama satu bulan daripada dua bulan. Bagian tubuh ikan yang berbeda menunjukkan sifat tekstur fillet yang berbeda. Tingkat kekerasan fillet ikan meningkat saat penyimpanan bulan ke dua, sementara sifat tekstur yang lain paling diminati saat penyimpanan bulan pertama dalam kondisi beku. Studi ini menunjukkan bahwa kualitas sensoris fillet ikan Pangasius dengan pembekuan air blast berubah seiring waktu bahkan dalam penyimpanan beku.Kata kunci: fillet, jumlah mikroba, Pangasius, sensori, tekstu

Interactions between different forms of bovine lactoferrin and sodium alginate affect the properties of their mixtures

The interactions between different forms (apo-, native- and holo-) of lactoferrin (Lf) and sodium alginate at different ratios in aqueous solution in the pH range of 4-7 were evaluated. Fourier transform infra-red (FTIR) spectra of freeze dried mixtures showed shifts only in the bands arising from the carboxylate groups of alginate relative to physical mixtures; indicating intermolecular interactions involving COO- moieties of alginate. Circular dichroism (CD) spectroscopy showed that Lf retained its tertiary structure in the Lf-alginate mixtures. In the pH range of 4-7, the zeta-potential of Lf-alginate solutions was significantly less negative than that of alginate indicating charge compensation. Native-PAGE results indicated that the extent of binding of Lf by alginate was dependent of the form of Lf with apo-Lf displaying a higher binding affinity. At natural pH, the Lf-alginate mixtures generated higher viscosities than their respective sodium alginate controls indicating the existence of intermolecular interactions between the two components. A mixture of native-Lf and sodium alginate showed the highest increase in the viscosity while increasing level of iron saturation in Lf showed an inverse effect on viscosity. DSC analysis showed that the thermal denaturation temperature of native-and holo-Lf can be enhanced upon interaction with alginate in solution. (C) 2015 Elsevier Ltd. All rights reserved

In-vitro digestion of different forms of bovine lactoferrin encapsulated in alginate micro-gel particles

Encapsulation of three forms of lactoferrin (Lf) (apo-, native- and holo-) was undertaken using the novel impinging aerosol technique (Progel). The micro-gel particles were produced from a 2% (w/w) solution of Lf and alginate (at equal mixing ratio) using 0.1M CaCl2 as the cross-linking solution. An encapsulation efficiency of 68-88% was achieved based on the total amount of Lf entrapped in alginate micro-gel matrix. Increasing the CaCl2 concentration to 0.2M reduced the encapsulation efficiency. An in-vitro digestion study conducted in simulated gastric fluid (SGF) and intestinal fluid (SIF) used pepsin and pancreatin (porcine) enzymes, respectively. Lf encapsulated micro-gel particles were able to retain significantly higher amount (76-89%) of Lf (apo- and native-forms) when digested in the SGF for 2h as compared to their corresponding un-encapsulated pure Lf (41-58%). The effect of encapsulation on digestibility in SGF of holo-Lf was minimal. Digestion of all forms of Lf, pure or encapsulated, in the SIF was very rapid. Within 10min, apo- and native-Lf were completely digested, while holo-Lf, exhibited some resistance as less than 5% remained after 10min. This study showed that encapsulating apo- and native-Lf in alginate micro-gel particles can provide protection from the action of pepsin in the SGF and allow their releases in the SIF

Characterization of alginate-lactoferrin beads prepared by extrusion gelation method

The potential use of lactoferrin (Lf) as a food ingredient is attracting increasing attention. Encapsulation of Lf in alginate gel beads can potentially enhance its stability and safe delivery. It is therefore important to understand the properties of alginateeLf beads in order to develop a successful encapsulation method. Three different forms (apo-, native- and holo-) of bovine Lactoferrin (Lf) were encapsulated in alginate beads by the gel entrapment method using calcium as the cross-linking ion. A minimum of 40% alginate was required in the beading mixture to retain the form of a bead. Higher proportion of alginate reduced the water holding capacity and calcium uptake by the beads and these effects were similar for all forms of Lf. Longer cross-linking time led a greater amount of Lf and iron leaching from the beads and this was most pronounced for holo-Lf compared to apo- and native-Lf. The elastic modulus was affected by the composition (mixing ratio) of beads and not by the forms of Lf with decreasing elasticity of the beads with increasing alginate content which was attributed to the decreasing crosslinking density. The stability of the encapsulated Lf was evaluated based on the amount leached into pH adjusted Millipore water and was affected by pH (4 and 7) for holo-Lf but not for apo- and native-Lf. The relative rate of Lf leaching at pH 4 for the different forms of Lf was found not to directly correlate with the pI of the different forms of Lf

Protein-based structures for food applications: from macro to nanoscale

Novel food structures' development through handling of macroscopic and microscopic properties of bio-based materials (e.g., size, shape, and texture) is receiving a lot of attention since it allows controlling or changing structures' functionality. Proteins are among the most abundant and employed biomaterials in food technology. They are excellent candidates for creating novel food structures due to their nutritional value, biodegradability, biocompatibility, generally recognized as safe (GRAS) status and molecular characteristics. Additionally, the exploitation of proteins' gelation and aggregation properties can be used to encapsulate bioactive compounds inside their network and produce consistent delivery systems at macro-, micro-, and nanoscale. Consequently, bioactive compounds which are exposed to harsh storage and processing conditions and digestion environment may be protected and their bioavailability could be enhanced. In this review, a range of functional and structural properties of proteins which can be explored to develop macro-, micro-, and nanostructures with numerous promising food applications was discussed. Also, this review points out the relevance of scale on these structures' properties, allowing appropriate tailoring of protein-based systems such as hydrogels and micro- or nanocapsules to be used as bioactive compounds delivery systems. Finally, the behavior of these systems in the gastrointestinal tract (GIT) and the impact on bioactive compound bioavailability are thoroughly discussed.JM and AP acknowledge the Portuguese Foundation for Science and Technology (FCT) for their fellowships (SFRH/BPD/89992/2012 and SFRH/BPD/101181/2014). This work was supported by Portuguese FCT under the scope of the Project PTDC/AGR-TEC/5215/2014, of the strategic funding of UID/BIO/04469 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Physico-chemical properties of different forms of bovine lactoferrin

Three forms of bovine lactoferrin (Lf), apo-, native- and holo- with 0.9%, 12.9% and 99.7% iron content, respectively, were characterised for their physico-chemical properties. Colour, surface tension, thermal properties, particle charge and rheological behaviour of Lf were found to be affected by the form of Lf. The surface tension of Lf tends to decrease with decrease in iron content. The Circular Dichroism (CD) spectra confirmed that all forms of Lf had similar secondary structures while the tertiary structure was different for holo-Lf. The Differential Scanning Calorimeter (DSC) analysis showed that the apo- and holo-Lf in aqueous solution displayed thermal denaturation temperatures of 71 ± 0.2 and 91 ± 0.5 °C, respectively, suggesting that the iron saturation of Lf tends to increase its thermal stability. The study of particle charge properties (ζ -potential) in 1 mM KCl salt solution showed that apo-Lf reached the net charge of zero in the pH range 5.5-6.5 whereas native and holo-Lf in the pH range 8.0-9.0. The apparent viscosity of 1% (wt/wt) solution of the different forms of Lf showed no difference between apo- and native-Lf (≈ 1.4 mPa s) while the value was significantly higher (2.38 mPa s) for holo-Lf