P. Muhamed Ashraf

Structural and oxidative stabilization of spray dried fish oil microencapsulates with gum arabic and sage polyphenols: Characterization and release kinetics.

The synergistic efficacy of gum arabic and sage polyphenols in stabilising capsule wall and protecting fish oil encapsulates from heat induced disruption and oxidative deterioration during spray drying was assessed. The emulsions prepared with sodium caseinate as wall polymer, gum arabic as wall co-polymer and sage extract as wall stabiliser was spray dried using a single fluid nozzle. Fish oil encapsulates stabilised with gum arabic and sage extract (SOE) exhibited significantly higher encapsulation efficiency compared to encapsulates containing gum arabic alone (FOE). Scanning electron microscopic and atomic force microscopic images revealed uniform encapsulates with good sphericity and smooth surface for SOE, compared to FOE powder. In vitro oil release of microencapsulates indicated negligible oil release in buffered saline whereas more than 80% of the oil loaded in encapsulates were released in simulated GI fluids. The encapsulates containing sage extract showed a lower rate of lipid oxidation during storage.

Effect of optically active substances and atmospheric correction schemes on remote-sensing reflectance at a coastal site off Kochi

The present study focused on understanding the variability of optically active substances (OASs) and their effect on spectral remote-sensing reflectance (Rrs). Furthermore, the effect of atmospheric correction schemes on the retrieval of chlorophyll-a (chl-a) from satellite data was also analysed. The OASs considered here are chl-a, coloured dissolved organic matter (CDOM), and total suspended matter (TSM). Satellite data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite was used for this study. The two atmospheric correction schemes considered were: multi-scattering with two-band model selection NIR correction (hereon referred as ‘A1’) and Management Unit of the North Sea Mathematical Models (MUMM) correction and MUMM NIR calculation (hereafter referred as ‘A2’). The default MODIS bio-optical algorithm (OC3M) was used for the retrieval of chl-a. Analysis of OASs showed that chl-a was the major light-absorbing component, with highly variable distribution (0.006–25.85 mg m–3). Absorption due to CDOM at 440 nm (aCDOM440) varied from 0.002 to 0.31 m–1 whereas TSM varied from 0.005 to 33.44 mg l–1. The highest concentration of chl-a was observed from August to November (i.e. end of the southwest monsoon and beginning of the northeast monsoon), which was attributed to coastal upwelling. The average value of aCDOM440 was found to be lower than the global mean. A significant negative relationship between aCDOM440 and salinity during the southwest monsoon indicated that much of the CDOM during this season was derived from river discharge. Spectral Rrs was found to be strongly linked to the variability in chl-a concentration, indicating that chl-a was the major light-absorbing component. Satellite-derived spectral Rrs was in good agreement with that in situ when chl-a concentration was lower than 5 mg m–3. The validation of chl-a, derived from in situ Rrs, showed moderate performance (correlation coefficient, R2 = 0.64; log10(RMSE) = 0.434; absolute percentage difference (APD) = 43.6% and relative percentage difference (RPD) = 42.33%). However the accuracy of the algorithm was still within acceptable limits. The statistical analysis for atmospheric correction schemes showed improved mean ratio of measured to estimated chl-a (‘r’ = 1.6), log10(RMSE) (0.49), APD (25.46%), and RPD (17.57%) in the case of A1 as compared with A2, whereas in the case of A2, R2 (0.56), slope (0.26), and intercept (0.27) were better as compared with A1. The two atmospheric correction schemes did not show any significant statistical difference. However the default atmospheric correction scheme (A1) was found to be performing comparatively better probably due to the fact that the concentration of TSM and CDOM was much lower to overcome the impact of chl-a.

Structural, functional and in vitro digestion characteristics of spray dried fish roe powder stabilised with gum arabic

Fish roes are considered as nutritionally valuable for their high content of essential fatty acids and amino acids. However, roe lipids undergo considerable extent of oxidation during processing and storage, imparting objectionable bitter taste and rancid flavour to roe products. Hence, the objective of the study was to reconstitute the roe mass and microencapsulate lipid fraction, so that small oil droplets are entrapped within a dry matrix of roe proteins during spray drying. Prior to spray drying, the emulsion was stabilised with gum arabic as it also act as a co-wall polymer. The microscopic images indicated presence of larger aggregates in unstabilised powder (RC) compared to well-separated particles in stabilised powder (RG). Incorporation of gum arabic retarded rancidity development during storage. In vitro digestive pattern of roe powder indicated higher amount of oil release in RG. These observations highlight the potential of converting the soft textured carp roe mass into stable fish roe powder with superior storage stability and functionality.

Development of graphene–nanometre-sized cerium oxide-incorporated aluminium and its electrochemical evaluation

Graphene–nanometre-sized cerium oxide-incorporated aluminium was prepared and its electrochemical and surface morphological characteristics were studied. The atomic force micrographs and scanning electron micrographs evaluation highlighted that the graphene and nanometre-sized cerium oxide in aluminium had decreased the surface roughness and improved the surface morphological characteristics. The graphene: nanometre-sized cerium oxide (ratios 1:2 or 2:1) with lesser amounts of particle in the matrix showed excellent corrosion resistance in the marine environment as evidenced by linear polarization, electrochemical impedance and weight loss studies. Introduction of graphene in the aluminium matrix showed a barrier separation between the outermost layer and inner layer, increased roughness and increased corrosion. The material is found to be a potential candidate for use in marine environment.