Food Technology
Seyfoallah Hamzeh-Kalkenari; Hojatollah Bodaghi; Ziba Ghasimi Hagh
Abstract
Introduction: Button mushrooms are the main edible mushrooms in Iran and the most important quality indicators of this fungus are the whiteness, having a glossy cap, straight stem, lack of brown spots. The mushroom has a higher respiration rate than other horticultural products and, due to the lack of ...
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Introduction: Button mushrooms are the main edible mushrooms in Iran and the most important quality indicators of this fungus are the whiteness, having a glossy cap, straight stem, lack of brown spots. The mushroom has a higher respiration rate than other horticultural products and, due to the lack of natural protective cover to prevent water loss, its edible quality is rapidly lost. In the last decade, the use of polyethylene films to create a modified atmosphere and natural essential oils to extend the shelf life of crops has been greatly expanded. Mushrooms packaging Polymeric nanocomposites are two-phase systems comprising a polymeric matrix and inorganic nanoparticles. Clay nanoparticles are among the most widely studied nanoparticles. When added to the nanocomposite films, the clay nanoparticles increase the film strength and decrease the permeability of the nanocomposite film. Also, the incorporation of natural essential oils can greatly increase the post-harvest life and prevent deterioration. Recently, essentail oils have been widely used in various fields after harvesting fruits, flowers, and vegetables. So far, there has been no report on the combined use of nanocomposite films and plant essential oils on extending shelf life of buttom mushroom. Materials and methods: Mushroom samples were obtained from Shahwar Company in shahrood. The experiment was conducted as a factorial experiment in a completely randomized design with 3 replications. The first factor Echinophora cinerea essential oil, was sprayed on the product at three levels of 0, 5 and 10 µl /l. The second factor was low-density polyethylene packaging films and 20 μm thick polyethylene-clay nanocomposite films. Subsequently, 100 g bottom mushrooms were packaged in the desired 25×20 cm films, the packed mushrooms were then transferred to 4± 1°C and relative humidity 90% storage conditions. Post-harvest qualitative traits were studied at 5-day intervals for 35 days. The studied traits were: tissue firmness, membrane permeability (electrolyte leakage), membrane lipid peroxidation (MDA), catalase and superoxide dismutase activity, microbial population, browning index, fungal opening percentage and fungal marketability. Results and Discussion: Packed mushrooms in nanocomposite films with and withoutessential oils did not show a significant effect on weight loss during storage, which could be due to the effective performance of nanocomposite films in preventing water vapor and the creation of a favorable modified atmosphere in the microclimate space inside the packages. Tissue softening was delayed in packed mushrooms in nanocomposite films compared to polyethylene films, also coating of essential oil on packed mushrooms in nano films compared to polyethylene films. Polyethylene films had a significant effect on decreasing the firmness parameter during storage. Evaluation of the effect of essential oil coating and the packaging showed that the essential oil was effective in reducing electrolyte leakage and malondialdehyde content in both types of packaging with both concentrations, but the results were better with 100 μl /l. The change in membrane permeability and malondialdehyde content reflects membrane damage as the cellular oxidative damage of MDA content, which is a product of membrane lipid peroxidation, increases. The higher activity of catalase in the mushroom in nanocomposite films coated with essential oils indicates that the process of decay and aging in the mushroom tissue is delayed. The aerobic cells of the plant produce reactive oxygen species such as H2O2 against stress and their toxicity is eliminated by both types of enzymatic and non-enzymatic antioxidant systems. SOD enzyme activity was higher in mushroom packed in nanocomposite films and coated with essential oils than in polyethylene films alone. This enzyme acts as the basic scanengering enzyme for O-2 radicals and catalysis to H2O2 and O2. It seems that the lower permeability of nanocomposite films compared to polyethylene films leads to prevent oxygen entry to a certain extent and the lower activity of this enzyme reduces the browning of the mushroom caps. On the other hand, coating with essential oil has also reduced the browning rate. The marketability of mushroom in polyethylene packaging has decreased significantly since the 20th day of clay nanocomposite, while the marketability of mushroom in the packaging of nanocomposite and essential oil coatings was acceptable by the end of 35th day. The results of this study indicate that although for the better prevention of senescence and contamination of buttom mushrooms during storage at 4°C, use of essential oil in polyethylene packaging can be effective but change in the structure of polyethylene by adding 5% nanoclay, it was highly desirable to increase the shelf life of the mushroom by retaining the quantitative and qualitative characteristics.
Hojatollah Bodaghi; Younes Mostofi; Abdulrasoul Oromiehie; Zabihollah Zamani; Babak Ghanbarzadeh; Ziba Ghasimi Hagh
Abstract
Introduction: Active and intelligent packaging devices and systems represent emerging technologies that may have profound implications on the quality, safety and integrity of packaged food and beverage products. It is well known that the photocatalyst titanium dioxide (TiO2), being a wide band gap (3.2 ...
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Introduction: Active and intelligent packaging devices and systems represent emerging technologies that may have profound implications on the quality, safety and integrity of packaged food and beverage products. It is well known that the photocatalyst titanium dioxide (TiO2), being a wide band gap (3.2 eV) semiconductor under UV illumination, generates energy-rich electron-hole pairs that can be transferred to the surface of TiO2, and promotes reactivity with the surface-absorbed molecules leading to the production of active radicals. These active radicals oxidize C-H bonds resulting in degradation of the organic molecules TiO2 photocatalyst has been used to degrade organic pollutants and inactivate a wide spectrum of microorganisms. To the best of our knowledge, there is no report on the photocatalytic disinfection properties of low density polyethylene (LDPE)-TiO2 nanocomposite produced by extrusion. Therefore, in this study LDPE-TiO2 nanocomposite film was prepared by a film blowing machine. The antimicrobial activity of the new packaging film against Pseudomonas spp. and Rhodotorula mucilaginosa, representing the main microorganisms on fruit and vegetable crops, was examined in vitro under UVA light. The antimicrobial property of the developed active film was also tested in a food application Materials and methods: LDPE -TiO2 nanocomposite was prepared by the melt blending method. Modified TiO2 (M-TiO2) powder obtained by mixing modified anatase and rutile phases in a weight ratio of 7:3 (total of 30 g), LDPE granules (935 g), PE-MA (30 g) and glycerol (5 g) were blended for 1 h using a mixer. The mixture was extruded by a Brabender twin-screw compounder (model DSE 20, Germany) for incorporating nanoparticles into the LDPE matrix. For LDPE and its nanocompounds, a constant temperature of 130 °C was used in all the zones of the extruder and the speed of the central screw was set to 120 rpm. The extrudate was cooled down in air at 23 ± 3 °C and pelletized. A composite LDPE-TiO2 film with a thickness of 30 ± 3 µm was finally obtained by a film-blowing machine. The resulting film had a milky whitish appearance. In vitro and in vivo antimicrobial activity test of film Each test film (6 cm diameter) was placed in sterilized petri dishes under aseptic conditions. One mL of each microorganism stock solution (containing approximately 108 and 107 CFU/mL for Pseudomonas spp. and R. mucilaginosa, respectively) was pipetted onto each test piece in its petri dish. Test samples were placed at a distance of 25 cm from six 8-WUVA black light bulbs Samples were taken in three replicates at 60 min intervals for 3 h. Then, 9 mL of sterile saline solution was added to the petri dishes containing the test and polyethylene films and shaken for 180 s on a universal small shaker (IKA MS 3 digital, Germany). One milliliter of solution was withdrawn at each sampling event and diluted to 1/10, 1/100, 1/1000, and 1/10,000 with sterile saline solution. A volume of 0.1 mL of the undiluted and diluted solutions was plated over appropriate media. Pseudomonas agar base (PAB) was incubated at 25 °C for 48 h for Pseudomonas spp. and Sabouraud dextrose agar for R. mucilaginosa and the colony-forming units (CFU) were counted. For in vivo test, every 6 days, approximately 20 g of packed apricot pieces with nanocompsite films, were collected randomly and placed into 180 mL of saline solution and agitated in a stomacher bag for 120 s. Decimal dilutions were made in sterile saline solution and 0.1 mL of the undiluted and diluted solutions were plated. Results and discussion: This work describes a TiO2 nanocomposite thin film with biocidal capacity for food packaging that was prepared by the extrusion method. The film caused inactivation of Pseudomonas spp., R. mucilaginosa and mesophilic bacteria in saline solution and on apricot when exposed to UVA light. The number of microorganisms on LDPE-TiO2 nanocomposite film plus UVA light was lower than that on LDPE-TiO2 nanocomposite film without UVA light and LDPE film exposed to UVA light. These results suggest that the TiO2 nanoparticles were responsible for the antimicrobial effect when exposed to UVA light illumination. The higher antimicrobial activity of the composite films under UV light is due to the photocatalytic reaction of the TiO2 nanoparticles in the matrix. Thus, the prepared TiO2 nanocomposite films are effective in diminishing live microorganisms and are promising as antimicrobial packages.
