Danial Dehnad

Thermal and antimicrobial properties of chitosan–nanocellulose films for extending shelf life of ground meat

Chitosan-nanocellulose biocomposites were prepared from chitosan having molecular weight of 600-800 kDa, nanocellulose with 20-50 nm diameters and various levels of 30, 60 and 90% (v/wCHT) for glycerol. Agitation and sonication were used to facilitate even dispersion of particles in the polymer matrix. The nanocomposites were examined by differential scanning calorimetry, X-ray diffraction and agar disc diffusion tests; finally, the film was applied on the surface of ground meat to evaluate its performance in real terms. Chitosan-nanocellulose nanocomposites showed high Tg range of 115-124°C and were able to keep their solid state until the temperature (Tm) range of 97-99°C. XRD photographs revealed that nanocellulose peak completely disappeared after their addition to chitosan context. Agar disc diffusion method proved that the nancomposite had inhibitory effects against both gram-positive (S. aureus) and gram-negative (E. coli and S. enteritidis) bacteria through its contact area. Application of chitosan-nanocellulose nanocomposite on the ground meat decreased lactic acid bacteria population compared with nylon packaged samples up to 1.3 and 3.1 logarithmic cycles at 3 and 25°C after 6 days of storage, respectively.

Microencapsulation optimization of natural anthocyanins with maltodextrin, gum Arabic and gelatin.

The barberry (Berberis vulgaris) extract which is a rich source of anthocyanins was used for spray drying encapsulation with three different wall materials, i.e., combination of maltodextrin and gum Arabic (MD+GA), maltodextrin and gelatin (MD+GE), and maltodextrin (MD). Response Surface Methodology (RSM) was applied for optimization of microencapsulation efficiency and physical properties of encapsulated powders considering wall material type as well as different ratios of core to wall materials as independent variables. Physical characteristics of spray-dried powders were investigated by further analyses of moisture content, hygroscopicity, degree of caking, solubility, bulk and absolute density, porosity, flowability and microstructural evaluation of encapsulated powders. Our results indicated that samples produced with MD+GA as wall materials represented the highest process efficiency and best powder quality; the optimum conditions of microencapsulation process for barberry anthocyanins were found to be the wall material content and anthocyanin load of 24.54% and 13.82%, respectively. Under such conditions, the microencapsulation efficiency (ME) of anthocyanins could be as high as 92.83%.

Physical and mechanical properties in biodegradable films of whey protein concentrate–pullulan by application of beeswax

Different ratios of whey protein concentrate (WPC):pullulan (PUL) (70:30, 50:50, 30:70%w/w) and various rates of beeswax (BW) (0, 10, 20, and 30%w/wglycerol) were applied to prepare biodegradable WPC-PUL films containing glycerol as a plasticizer, for the first time. Thickness, moisture content, water solubility, water vapour permeability, colour, and mechanical properties of prepared films were measured. Higher ratios of WPC:PUL led to more desirable physical and mechanical properties; in other words, lower rates of thickness, moisture content, water solubility and water vapour permeability, and higher elongations were achieved. Application of BW (especially in higher contents) could successfully improve colour indices, diminish water solubility (nearly 12%) and water vapour permeability (approximately 3×10(-11)gm(-1)s(-1)Pa(-1)), and increase tensile strength (by about 7MPa) of WPC-PUL blend films. Our edible films enjoyed great whiteness and ignorable yellowness indices, making it a suitable alternative for application in food products. Overall, WPC70-PUL30 containing 30% BW resulted in the best performance of physical and mechanical aspects as an optimum film.

The Influence of Refractance Window Drying on Qualitative Properties of Kiwifruit Slices

Abstract: In this research, effect of Refractance Window (RW) drying on the quality properties of the kiwifruit samples was investigated. Drying temperatures of 80–100 °C, slice thickness of 0.8–2.4 mm and Mylar thickness of 100–300 µm were the independent variables and different qualitative attributes including drying duration, textural hardness, colour, rehydration ratio and organoleptic properties were responses monitored in each situation. Drying temperature was the most important factor contributed to quality features of RW dried kiwifruits with significant effects on all properties. Similarly, slice thickness influenced nearly all quality traits except textural hardness and some colour indices. However, Mylar membrane thickness failed to affect about every qualitative property of kiwifruit samples significantly. The majority of organoleptic properties of RW dried kiwifruits, including flavour, colour, texture, shrinkage and overall acceptance, were judged to be in the range of medium to good quality (scores of 3–4) by panellists.

Hydrophobicity, thermal and micro-structural properties of whey protein concentrate-pullulan-beeswax films.

In this research, effects of beeswax (BW) on functional properties of whey protein concentrates (WPC):pullulan (PUL) films were investigated. For this purpose, 0, 10, 20 and 30w/w(glycerol)% BW rates and 30:70, 50:50 and 70:30w/w% WPC:PUL ratios were applied. Films containing 70% WPC:30% PUL (WPC70) and 30% BW (BW30) justified the highest contact angle (92.4°) among all films; SEM micrographs indicated that BW could come toward the surface of films during drying stage and resulted in a higher hydrophobic behavior of bilayer films compared with blend films. WPC70 supplied the lowest T(g) values (36-48 °C) among different proportions of WPC-PUL; the highest melting points were just assured in the absence of BW regardless of combination ratio for WPI:PUL. BW30 films deserved lower roughness rates than BW20 (and even BW10) films, indicating more advantageous microstructure and higher hydrogen connections in BW30 films and justifying similar melting points attained for BW30 films to BW20 or 10 ones. Overall, application of WPC70 and BW30 was recommended to obtain optimum combination of final properties for WPC-PUL-BW bilayer films as SEM exhibited flexible and elastic structures of such films.

Arrhenius equation modeling for the shelf life prediction of tomato paste containing a natural preservative

BACKGROUND The shelf life of tomato paste with microencapsulated olive leaf extract was compared with that of samples containing a commercial preservative by accelerated shelf life testing. Based on previous studies showing that olive leaf extract as a rich source of phenolic compounds can have antimicrobial properties, application of its encapsulated form to improve the storage stability of tomato paste is proposed here. RESULTS Regarding total soluble solids, the control and the sample containing 1000 µg g-1 sodium benzoate had the lowest (Q10  = 1.63) and highest (Q10  = 1.88) sensitivity to temperature changes respectively; also, the microencapsulated sample containing 1000 µg g-1 encapsulated olive leaf extract (Q10  = 1.83) followed the sample containing 1000 µg g-1 sodium benzoate in terms of the highest kinetic rates. In the case of consistency, the lowest and highest activation energies (Ea ) corresponded to samples containing 1000 µg g-1 non-encapsulated olive leaf extract and 1000 µg g-1 microencapsulated olive leaf extract respectively. CONCLUSION Interestingly, samples containing microencapsulated olive leaf extract could maintain the original quality of the tomato paste very well, while those with non-encapsulated olive leaf extract rated the worst performance (among all specimens) in terms of maintaining their quality indices for a long time period. Overall, the shelf life equation was able to predict the consistency index of all tomato paste samples during long-time storage with high precision.

Evaluation of physical, rheological, microbial, and organoleptic properties of meat powder produced by Refractance Window drying

ABSTRACT Meat spoils very rapidly and its microbial load exceeds the permitted limit very soon even if it is kept in a refrigerator. The main goal of this study was to dry meat by a Refractance Window drier successfully, for the first time, and to evaluate its compositional, physical, rheological behavior, microbiological, and organoleptic properties. Meat powder produced by RW drying had good physical properties including maximum absolute density of 0.81 g cm−3, porosity of 0.67, rehydration ratio of 2.8, L* value of 64, and minimum a*/b* value of 0.57. Herschel–Bulkley and Bingham models could predict rheological indices of meat powder solutions with high R2 rates of 0.955–0.995. Sensory evaluation indicated that although meat powder obtained from 3 mm slices was more favorable for panelists, the consistency of 2 mm meat powders was more agreeable, which could be attributed to better functional properties of more dried samples. 100°C and 2 mm treatment could decrease aerobic bacterial count from 6.1 to 3.7 log CFU/g and Enterobacteriaceae population from 3.1 log CFU/g to nil successfully. In summary, our comparison indicated that meat powder produced by Refractance Window drying technique can lead to better dried products than dried meats having been prepared with other novel techniques recently.

Preparation and characterization of nano-SiO 2 reinforced gelatin-k-carrageenan biocomposites

The main goal of this study was to prepare bionanocomposites by combination of gelatin (10% w/v), k-carrageenan (0.5%) and nano-SiO2 (1, 3 or 5%). Then, mechanical properties (tensile strength, elongation at break, Youngs modulus), gas permeability (water vapor, oxygen), water solubility, color, UV-vis transmission/absorbance, water vapor adsorption isotherms and Fourier transform infrared (FTIR) analysis of nanocomposites were evaluated. As the results indicated, inclusion of nano-SiO2 (at each level) could increase tensile strength and Youngs modulus significantly, with the latter becoming nearly 110% higher at 5% nanoparticle level compared with gelatin-carrageenan biocompostes. Furthermore, incorporation of 5% nano-SiO2 could decrease water vapor permeability of biocomposites from 8.9 to 1.6 × 10-11 g m-1 s-1 Pa-1 and their oxygen permeability from 226 to 97 cm3 μm m-2 day-1 atm-1. Water vapor adsorption isotherms revealed that the water activity of 0.5 was the critical point beyond which the difference in equilibrium moisture content between nanoparticle-incorporated films and biocomposites increased considerably. Besides, this research demonstrated that including 5% of nano-SiO2 is a good solution to delay UV light driven reactions as it elevated absorbance of UV light (220 nm) by biocomposites up to 4 times.

The influence of nanocellulose coating on saffron quality during storage

Since saffron is an added-value product, and the most expensive agricultural product, it is necessary to increase its shelf life, prevent its quality loss during storage, and maintain its organoleptic properties, enabling producers to export saffron with higher quality and better consumer acceptability. So, in this research, saffron samples were coated through applying different carbohydrate biopolymers: maltodextrin with DE=4 or DE=20 (MD4 and MD20) or their combination with nanocellulose fibres (MDC4 and MDC20). Finally, the experiments were carried out to measure rehydration ratio, water activity, crocin content, color values, and sensory properties of saffron samples coated by different materials. MDC4 resulted in the lowest rehydration ratio among coated samples since, first, lower DE degrees of biopolymer complexes decreased moisture adsorption and solubility of maltodextrin and second, crystalline nanocellulose fibres increased tortuous and bended pathways in materials and reduced penetration possibilities of water molecules. MDC4 was the most effective treatment in preventing crocin decrease. Indeed, film forming characteristic of maltodextrin with low hydrolysis degree and special structure of nanocellulose led to the maintenance of crocin bioactive ingredient. SEM observations revealed coating on saffron surfaces as a thin clear and brilliant layer which enhanced saffron acceptability for our panelists.