جستجوی مقالات مرتبط با کلیدواژه "نانو کامپوزیت" در نشریات گروه "صنایع غذایی"

In this study, the survival of Lactobacillus casei probiotic bacteria added to polylactic acid-nanocellulose nanocomposite film during 16 days of storage in the refrigerator was investigated. For this purpose, three edible films including polylactic acid, polylactic acid + nano cellulose, polylactic acid + nano cellulose+ Lactobacillus casei (9 log CFU/g) were prepared and the physical and mechanical characteristics of the films as well as the survival of Lactobacillus casei bacteria were investigated. The results of the mechanical test showed that the use of probiotic bacteria decreased the tensile strength and elongation at break of the polylactic acid-nanocellulose film (P < 0.05), but the addition of nanocellulose improved the mechanical properties of the polylactic acid film. The results of physical tests including humidity, solubility, water vapor permeability showed that the addition of probiotic bacteria and nanocellulose improved the physical properties of the film, but the opacity of the films increased (P<0.05). According to the results of the present study, with the increase in storage time, the survival of probiotic bacteria in the nanofilm decreased, and at the end of the storage period, its values were equal to 6.12 log CFU/g, but it was within the permissible range (6 log CFU/g).Therefore, the composition of Lactobacillus casei probiotic strain in the edible film can be its suitable carrier at refrigerator temperature

Among the different types of polymers used for packaging and coating, polyvinyl alcohol (PVA), given its very enviable properties, has been used in various industrial applications. It is used for instance as controlled release in pharmaceutical elements, paper, textile and food supplement coating due to its good physical properties, chemical resistance, thermostability, film-forming capability, efficiency and biodegradability. The aim of this work was to examine the combined effect of montmorillonite (MMT) platelets and titanium oxide (TiO2) spherical nanoparticles on the physical and mechanical properties of PVA/ TiO2/MMT nanocomposites, and to determine the optimal combination to provide good properties, using response surface methodology (RSM).   Materials &

PVA, PVA/TiO2, PVA/MMT and PVA/ TiO2/MMT nanocomposite films were prepared by the solution casting method. For each sample, 1.8 g of PVA was dissolved in 50 mL deionized water and maintained for 24 h at room temperature. The mixture was then heated to 90˚C and stirred using a magnetic stirrer up to 3 h to ensure the complete dissolution of PVA, followed by cooling down the solution to room temperature. Various amounts of TiO2 nanoparticles (1 and 2 w% on a dry basis) were added to deionized water and agitated with a stirrer for 12 h at 500 rpm. This method was also used for MMT (2 and 4 w% on a dry basis). The nanoparticle suspension was subjected to ultrasonic homogenization for 20 min to ensure a good dispersion. The 50 mL nanoparticle suspension was added to the PVA solution drop by drop during a period of 5 min while maintaining intense stirring (1000 rpm). Mixing was continued and glycerol (30 w% based on the polymer) was added. Vacuum with a rotary vacuum pump was applied to remove air bubbles from the solution. The solution was poured into a 15-cm internal diameter Petri dish with a perfectly flat bottom and carefully aligned horizontally. Homogeneous films were peeled off after drying in an air oven at 40˚C for 72 h. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) were performed for characterizing the morphology of nanocomposite films. The effect of these two nanoparticles on physical and mechanical properties, was evaluated by response surface methodology (RSM). A three-level factorial design was used to define the test points for the series of experiments. Among the various design alternatives suggested by theoretical algorithm, the selected design consisted of 13 experiments including five replicate central points used for variance calculation. Furthermore, PVA film data were analyzed using the Design-Expert program (Version 7.0, Stat-Ease Inc., Minneapolis, Minnesota) to find the optimum combination of constituents for the best properties.  

X-ray diffraction patterns showed that the nanoparticles were well dispersed in the polymer matrix of PVA/ TiO2 and PVA / MMT films with layered microstructure. In addition, the linear effect of MMT nanoparticles and the interaction of TiO2 and MMT on tensile strength were significant. The linear, quadratic and interaction effects of both nanoparticles on Young's modulus were also significant. In general, the optimum values of TiO2 and MMT were 1% and 4% respectively for mechanical properties. The presence of both nanoparticles had a significant effect on transparency and ΔE. Results of nanocomposite films indicated that the film with 2% TiO2 and 4% MMT has higher WI and actually is darker than other samples. By analyzing different results with response surface method, the nanocomposite film with 0.5% TiO2 and 4% MMT was proposed as optimum combination for mechanical and physical properties

Natural polymers have gained increasing attention for the development of packaging to reduce ecologically-related problems caused by plastic packaging (environmental pollution). Among these natural polymers, proteins such as gelatin is considered a good candidate for food packaging. However, several studies have shown that gelatin films are brittle, and their hydrophilic nature connotes high water vapor permeability and water solubility. Different solutions have been suggested to overcome these weaknesses, including adding crosslinking agents and chemical modification, adding nanoparticles and developing bio-film blends and bilayers with polysaccharides. Agar is a polysaccharide extracted from marine red algae, which is biocompatible, has good mechanical properties and possesses good film-forming properties. Preventing food spoilage from light and oxygen-induced oxidation is one of the greatest concerns in the food industry. Despite having good mechanical and relatively good water vapor permeability properties, protein- or polysaccharide-based films dont have sufficient barrier properties against oxygen and UV light that cant properly prevent the oxidation of food products. Among nanoparticles, metal oxides like TiO2 (such as antiradiation and antimicrobial activities) and Montmorillonite (such as improved mechanical and barrier properties against moisture, WVP and gases) have evidenced good potential to improve functional properties of bio-films. Thus, the present study aimed to develop a new biodegradable bilayer agar/gelatin film incorporating nanoclay and TiO2 for food packaging, with maximum water sensitivity and maximum UV light and oxygen barrier properties.
Agar/gelatin bilayer films were prepared by a two-step casting technique. First, the agar layer was produced by solubilization of 1.5 g of agar powder (agar-agar analytical grade were obtained from Merck Co., Germany) in 100 mL of distilled water. Then, glycerol (obtained from Merck Co., Germany) was added as plasticizer. The agar film-forming solution was casted onto petri-dish. In the next step, the gelatin (obtained from cold water fish skin was purchased from Sigma-Aldrich, St. Louis, MO, USA) solutions were prepared by dissolving 4 g of the fish gelatin in 100 mL of distilled water. Glycerol was also added as plasticizer. The TiO2 dispersions (in ratios of 0 and 2% of the gelatin) and MMT (Na–montmorillonite (in ratios of 0, 3, 5 and 10% of the gelatin)) were added to the gelatin solution and stirred and sonnicated. Finally, produced solutions were then casted. The agar/gelatin films, with or without TiO2 and MMT, were characterized using SEM analysis. Film transparency, water vapor permeability, water solubility, swelling, surface color and mechanical properties of the bilayer films were also examined.
In this study, bilayer films based on agar and gelatin incorporated with TiO2-MMT nanoparticles have been successfully developed. Results demonstrated that some properties of the bilayer films were greatly influenced by TiO2 and MMT nanoparticle content. So that, the addition of TiO2 decreased water vapor permeability of the bilayers more than 15%, upon increasing TiO2 content to 2%. However, swelling ratio and moisture content increased with the increase in the nano-TiO2 content, probably due to the hydrophilic nature of the TiO2 nanoparticles. Also, whiteness index (WI) increased by adding 2% of TiO2 nanoparticles. As shown in the surface photograph of the bilayer films, TiO2 generated more opaque and whiter films, which might be related to the white color of TiO2 nanoparticles in solution form. Also, the addition of MMT (0, 3, 5, and 10%) to bilayer-2% TiO2 significantly decreased water vapor permeability and transmission of UV light of the bilayer films. However, tensile strength (TS) decreased with further increase of the nanoparticle concentration. Increasing the concentration of nanoparticle's MMT to 5%, the tensile TS of the agar/gelatin films increased from 12.86 to 20.54 MPa; it might also be related to the interactions between sulphydryl and carboxylic groups from certain amino acids in the gelatin structure with MMT and TiO2 nanoparticles. However, the TS decreased again with further increase of the filler content up to 10% MMT. Also, the addition of MMT from 3%-10% concentration significantly reduced the elongation at break value (EB) of the bilayer films from 41.77 to 28.90% for the bilayer films (p

It is important to increase storage quality of orange by using of natural coatings. In this research, quality of Thomson oranges coated with chitosan-clay nano composite edible coating and fogger - wax (fog production from Ortho Phenil Phenol by electro fogger with nano dimension) was compared with the sample without coating during storage. Orange quality properties were evaluated during storage for 3 months in a cold storage at 6oC temperature and 85-90% relative humidity. Results showed that fruits coated with chitosan-clay had highest pH, chroma, peel moisture and firmness compared to the other samples. Therefore, this nano coating increased fruit resistance to fungal diseases, retained peel fruit color and inner texture strength during storage. Amount of total soluble solid and acid total of fruit juice for fogger - wax coating decreased and increased during storage, which this trend could indicate fermentation phenomenon in the fruit. So using of chitosan-clay nano composite edible coating can be offered for prevention of decrease fruit quality during storage.

Three coatings، Carnoba wax، Chitosan and naocomposite، were used to prevent postharvest losses of Golden Delicious apple. The effect of three coatings was compared with uncoated samples on quality and physical properties of apples during storage. These properties were pH، soluble solids (TSS)، color intensity (a، b، L and E coefficients) and density. The variations of quality properties of apples during six months at two conditions of cold storage (2 °C and 95% RH) and environmental storage (20 °C and 45% RH) were evaluated. The results showed that pH، brix and color intensity for three coatings had an ascending trend but density and L had a descending trend in environmental condition. In the environmental condition، the highest color intensity losses were found for the without coating samples and the lowest losses for the wax coating samples. In opposite، color intensity for the wax coating samples had lowest losses. There was no more change in brix trend for nanocomposite coating.

In recent years using fresh foods that have undergone minimal processing، has become widespread. The use of active packaging is a new method for preserving of these products. In this study، active starch-clay nanocomposite films with addition of cinnamon essential oil or potassium sorbate (0، 5، 7. 5 and 10% on the base of dry starch) were prepared. The physical، mechanical and antimicrobial properties of the active films were evaluated. For the evaluation of antimicrobial properties of the films، Aspergillus niger was used as one of the important spoilage fungi of bread. The results showed that 5% of the antimicrobial additives didn’t any antimicrobial activity. However، by increasing the concentration of the additives، antimicrobial activity also increased. In the same amounts of both additives، the films which contained cinnamon essential oil had stronger antimicrobial effects. The addition of potassium sorbate increased water vapor permeability of the films. However، cinnamon essential oil، didn’t affect this property of the films. These results showed that the films could be used as an active food packaging.