Mehraj Ahmad

Characterisation of composite films fabricated from collagen/chitosan and collagen/soy protein isolate for food packaging applications

This study was undertaken to evaluate the potential of collagen/chitosan (CG/CH) and collagen/soy protein isolate (CG/SPI) composite films for food packaging applications. Two types of composite films at different blend ratios of CG/CH or CG/SPI (10 : 0, 8 : 2, 6 : 4, 5 : 5 and 0 : 10%, w/w) using 30% (w/w) glycerol as plasticiser were prepared and characterised. The results of mechanical tests of the CG/CH composite films displayed higher elongation at break point (EAB), but lower tensile strength (TS) and modulus of elasticity (E), compared to the CG film (P < 0.05). Conversely, the CG/SPI composite films exhibited lower EAB, but greater TS and E values (P < 0.05) compared to the CG film. Water vapour permeability (WVP) increased markedly in the CG/CH composite films; whilst it was found to decrease in CG/SPI composite films at the different blend ratios tested (P < 0.05). Transparency values and water solubility of CG/CH and CG/SPI composite films were decreased substantially, compared to the CG film (P < 0.05). Lower light transmission was observed in all composite films in ultraviolet (UV) and visible regions (200–800 nm), indicating improved UV blocking capacity. Intermolecular interactions through hydrogen bonding among polymeric components were dominant in the CG/SPI (8 : 2) composite film as elucidated by FTIR analysis. Thermo-gravimetric curves demonstrated that CG/CH (8 : 2) and CG/SPI (8 : 2) composite films exhibited lower heat susceptibility and weight loss (%), as compared to the CG film in the temperature range of 30–600 °C. DSC thermograms suggested that the compatible blend of CG/SPI (8 : 2) rendered a solid film matrix, which consisted of highly ordered and aggregated junction zones. SEM micrographs revealed that both CG/CH (8 : 2) and CG/SPI (8 : 2) composite films were slightly rougher than the CG film, but no apparent signs of cracking and layering phenomena were observed, thereby highlighting their potential use as biodegradable packaging materials.

Blend film based on fish gelatine/curdlan for packaging applications: spectral, microstructural and thermal characteristics

A series of novel fish gelatine/curdlan (FG/CL) blend films at different ratios (FG/CL ≈ 10:0, 8:2, 6:4, 5:5 and 0:10%, w/w) were successfully fabricated at pH 12 via a casting approach, and their physico-mechanical, spectral, microstructural and thermal properties were investigated as a function of CL content. FG/CL blend films exhibited lower tensile strength (TS) but higher elongation at break (EAB) and water vapour permeability (WVP), compared to FG film (P < 0.05). Increased contact angle (θ) and moisture content (MC), but decreased water solubility (WS) were obtained for FG/CL blend films having the higher proportion of CL (P < 0.05). Furthermore, the addition of CL decreased a*-(redness) and transparency values (P < 0.05), but enhanced L*-(lightness), b*-(yellowness) and ΔE*-values (total colour difference) (P < 0.05) in FG/CL blend films. Light transmission in ultraviolet (UV) and visible regions (200–800 nm) was lowered in all FG/CL blend films, indicating excellent light barrier characteristics. Significant changes in molecular order and decreased intermolecular interactions in the matrix of FG/CL blend film were determined based on FTIR spectroscopy. TGA and DTG curves displayed that FG/CL (8:2) blend film had enhanced heat stability as evidenced by higher heat-stable mass residues (34.1%, w/w), compared to FG film (26.6%, w/w) in the temperature range of 50–600 °C. DSC thermogram suggested the solid-state morphology of FG/CL (8:2) blend film that consisted of amorphous/microcrystalline phase of partially miscible FG/CL aggregated junction zones and the coexisting of unbound CL domains. SEM micrographs elucidated that FG/CL (8:2) blend film was slightly rougher than FG film, but no signs of phase separation between film components were observed, thereby confirming its prospective use as food packaging material.

Approach toward enhancement of halophilic protease production by Halobacterium sp. strain LBU50301 using statistical design response surface methodology

Highlights • Halophilic protease producing Halobacterium sp. strain LBU50301 was isolated.• RSM optimized the fermentation conditions to enhance halophilic protease yield.• Optimized conditions used in bioreactor resulted about 13-fold enhancement.

Undesirable enzymatic browning in crustaceans: causative effects and its inhibition by phenolic compounds

Undesirable enzymatic browning mediated by polyphenol oxidase (E.C. 1.14.18.1) on the surface of seafood from crustaceans have been a great concern to food processors, causing quality losses of seafood products. Seafoods especially from crustaceans are worldwide consumed due to their delicacy and nutritional value. However, black spot formation (melanosis) is the major problem occurring in crustaceans during postmortem handling and refrigerated storage induce deleterious changes in organoleptic properties and, therefore, decreases commercial value. Polyphenoloxidase (PPO), the copper-containing metalloprotein involved in oxidation of phenol to quinone is the major biochemical reaction of melanosis formation. This enzymatic mechanism causes unappealing blackening in postharvest crustaceans. To alleviate the melanosis formation in crustaceans, use of phenolic compounds from plant extract can serve as antimelanotics and appears to be a good alternative to the conventional sulfites which are associated with health-related disorders. In this review, we focuses on the unique features about the structure, distribution, and properties of PPO as well as mechanism of melanosis formation and provide a comprehensive deeper insight on the factors affecting melanosis formation and its inhibition by various antimelanotics including newly discovered plant phenolic compounds.

Fabrication and characterization of novel semolina-based antimicrobial films derived from the combination of ZnO nanorods and nanokaolin

This study aimed to provide novel biopolymer-based antimicrobial films as food packaging that may assist in reducing environmental pollution caused by the accumulation of synthetic food packaging. The blend of ZnO nanorods (ZnO-nr) and nanokaolin in different ratios (1:4, 2:3, 3:2 and 4:1) was incorporated into semolina, and nanocomposite films were prepared using solvent casting. The resulting films were characterized through field-emission scanning electron microscopy and X-ray diffraction. The mechanical, optical, physical, and antimicrobial properties of the films were also analyzed. The water vapor permeability of the films decreased with increasing ZnO-nr percentage, but their tensile strength and modulus of elasticity increased with increasing nanokaolin percentage. The UV transmittance of the semolina films were greatly influenced by an increase in the amount of ZnO-nr. The addition of ZnO-nr: nanokaolin at all ratios (except 1:4) into semolina reduced UV transmission to almost 0%. Furthermore, the ZnO-nr/nanokaolin/semolina films exhibited a strong antimicrobial activity against Staphylococcus aureus. These properties suggest that the combination of ZnO-nr and nanokaolin are potential fillers in semolina-based films to be used as active packaging for food and pharmaceuticals.