Food Chemistry
Dara Rezakhani; Abdolmajid Mirzaalian Dastjerdi; Somaye Rastegar
Abstract
The sapodilla fruit has a limited shelf life due to its perishability and rapid moisture loss. The application of edible coatings has attracted much interest because they are effective in prolonging the shelf life of fruits. This study aims to evaluate the effectiveness of an edible coating made from ...
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The sapodilla fruit has a limited shelf life due to its perishability and rapid moisture loss. The application of edible coatings has attracted much interest because they are effective in prolonging the shelf life of fruits. This study aims to evaluate the effectiveness of an edible coating made from xanthan gum (XG) (0.1% and 0.2%) combined with oleic acid (Ol) (1%) in prolonging the shelf life of sapodilla fruit at 8 ± 1 οc and a relative humidity (RH) of 85-90%. Weight loss was significantly reduced in the treated fruits, with the minimum weight loss observed in the Xan 0.2% + Ol treatment. Except for the Ol treatment, the other treatments showed a higher level of firmness compared to the control. At the end of the experiment, the treatments significantly reduced fruit respiration. The treated fruits also showed significantly increased antioxidant capacity and higher levels of ascorbic acid compared to the control. The lowest TSS (22.8%) level was noted in the Xan 0.2 + Ol treatment. Moreover, the results showed that fruit treated with Xan 0.1% + Ol coating exhibited higher activity in the superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) enzymes compared to the fruit treated with Xan 0.2 + Ol coating and the control samples. In general, fruits treated with Xan 0.2 + Ol and Xan 0.1% + Ol demonstrated the highest overall quality compared to the control and other treatments. Therefore, the application of these treatments is recommended for maintaining the quality of sapodilla fruit.
Food Technology
Rahmatollah Pourata; Hamid Jahangir-Esfahani; Iman Shahabi-Ghahfarrokhi
Abstract
Introduction: Among the bio-based materials which used in the food packaging, starch is interested as an ecofriendly material. This interest is mainly due to its acceptable film forming properties, easy access, renewability and low cost. Nevertheless, high hydrophilic and weak mechanical properties have ...
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Introduction: Among the bio-based materials which used in the food packaging, starch is interested as an ecofriendly material. This interest is mainly due to its acceptable film forming properties, easy access, renewability and low cost. Nevertheless, high hydrophilic and weak mechanical properties have been limited its utilization as a commercial packaging material. Many researches have been done to reduce hydrophilic properties of starch using chemical modification, irradiation, and composition with nanoparticles and other biopolymers. Most of the methods are based on blocking the hydroxyl groups of starch chains with hydrophobic agents, formation of emulsions and blocking of the pores. Fatty acids, such as oleic acid (OA) are lipid derivatives that can potentially improve the moisture barrier properties of hydrophilic films. OA is a yellow liquid at room temperature and miscible with biopolymer without further heating treatment. Due to the polar nature of biopolymers, OA needs to surfactant to get homogenous distribution in the matrix of biopolymers. On the other hand, OA is not very sensitive to oxidation which increases its safety in food packaging applications. Titanium dioxide (TiO2) is an inert, cheap and nontoxic material with broad application as a food pigment and potential activity against a wide variety of microorganism due to its photocatalytic activity.TiO2 is the most commonly used semiconductor, photocatalyst which activated by UV ray. The main purpose of the current study was modification of starch hydrophilicity using OA, nano-titanium dioxide and UV ray. In this study OA and TiO2 added at the optimized condition and the solution was irradiated by UV ray. Materials and Methods: A starch solution 5 (wt. %) in distilled water was prepared. This solution was mixed and heated (85 ˚C for 15 min) until the starch gelatinized. Thus, plasticizer (glycerol, 40 wt. % of dry base) was incorporated into the solution to achieve more-flexible films. OA 1(wt. % of dry base) mixed with Tween 80 as emulsifier (10 wt. % of the OA). This solution was mixed and heated (50 ˚C for 10 min). Then, 10 ml of distilled water was added to the solution, and homogenized by ultrasonic homogenizer (Dr. Hielscher, Teltow, Germany) for 7 min. The suspension of TiO2 nanoparticles in water was prepared so that the final TiO2 content in film specimens was 2 (wt % of dry base). The suspensions were stirred for 10 min, and homogenized by ultrasonic homogenizer for 60 min. The TiO2 suspension was added to starch solution gradually and mixed for 10 min. Afterward, OA- Tween 80 solution was added to starch solution gradually and mixed for 10 min.The starch solution containing TiO2 and OA was homogenized by ultrasonic homogenizer for 7 min. Film forming solution placed under three UV-C lamps (8w, Phillips, Holland) at a distance of 5 cm. The solutions were stirred simultaneously with UV irradiation. After 0, 30, 60 and 90 min of UV exposure, the air bubbles were removed and the solutions were casted into flat, leveled, non-stick disposable 15 cm-Petri dishes. Each of the dishes were contain 43 g which dried for 48 hours at room temperature. All the film specimens were conditioned at 50-55% relative humidity and room temperature for 48 hours before subjected to further analysis.Moisture content (MC), moisture absorption (MA), solubility in water (SW), water vapor permeability (WVP), surface properties, visual properties and mechanical properties of the film specimens were measured. The chemical structure of the films was investigated by FTIR spectroscopy.Results and Discussion: The results shown that water contact angle of the starch film was increased by adding OA and TiO2. But it was decreased after UV exposure of the starch-OA-TiO2 solution. WVP of the starch based films was decreased by its composition with OA and TiO2. But no change was observed after UV exposure of the starch-OA-TiO2 compositions. MC of the starch-OA-TiO2 film had no change, simultaneously. However, the tensile strength and Young’s modulus were decreased by adding OA-TiO2. Elongation at break and tensile energy to break were increased, simultaneously. However, the mechanical properties of the starch-OA-TiO2 nanocomposites were changed by UV exposure but these changes did not follow a specific trend.Although, whiteness index (WI) and total color difference (ΔE) were not changed by OA-TiO2 composition. But yellowness index (YI) was changed, simultaneously. After UV irradiation ΔE and YI were increased and WI was decreased. The results, demonstrated that the virgin starch-OA-TiO2 composition was the best modification method to decrease the sensibility of starch based films to moisture as a packaging material. UV irradiation at short time (30 min) was the optimum condition to modify sensibility of the films to moisture and mechanical properties among the UV cured films.
Masoud Taghizadeh; Asma Eghbal
Abstract
Introduction: One of the methods for increasing shelf life of food is the use of edible coatings, since films and coatings have an important role in the enhance of shelf life and food product’s marketing. Various edible films are nowadays used for food packaging. Using of these biodegradable compounds ...
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Introduction: One of the methods for increasing shelf life of food is the use of edible coatings, since films and coatings have an important role in the enhance of shelf life and food product’s marketing. Various edible films are nowadays used for food packaging. Using of these biodegradable compounds is a new method of replacing polymeric materials and of increasing shelf life of food. Film and coating can control the diffusion of water, oxygen and carbon dioxide. Edible coatings also have the ability to enhance color, acid, sugar and taste during storage. Starch as a natural polymer be a lot in the nature and has a low cost and due to its structure containing amylose and amylopectin it is a suitable option for its use as film and edible coating because starch is barrier for oxygen, semi-permeable to CO2, and has good mechanical properties, therefore suitable for packaging films and edible coatings. However, due to the hydrophilic properties of starch, the starch based films are permeable to moisture and water vapor. One of the ways to reduce water vapor permeability for films and edible coatings is to use hydrophobic compounds such as oleic acid that formed in two layers. There is starch in the lower part of layer. Hydrophobic compound place in the upper layer and it is the barrier for water vapor. The main purpose of this research was to produce edible films based on starch and oleic acid and to investigate their characteristics (thickness, solubility, water vapor permeability, and tensile strength). One of the suitable treatments was then selected and tested at three concentrations as a film coating for greengage, and cases of pH drop and loss of weight, color, and hardness of the samples were recorded for four weeks. Material and methods: First, the film of starch and oleic acid were prepared and then the edible film characteristics such as thickness, solubility, water vapor permeability and tensile strength were measured. After evaluating the film parameters, the optimal amount of oleic acid was selected, then the starch and oleic acid solution of 8, 10, 12 g / l were prepared based on film formulation including starch, glycerol, oleic acid and tween 80. Then the characteristics of Greengage such as weight loss, pH, color and rigidity were measured. Result & discussion: The addition of oleic acid resulted increases in thickness of the edible films because of the increase in the material during solvent drying and variation in the relative humidity of the environment during drying of the material.Solubility: By increasing the amount of oleic acid, the amount of solubility decreased, which could be due to the change in the polarity of the film compounds, which increases the hydrophobicity of the film by increasing the oleic acid that is non-polar, and keep the polar parts away from water. Oleic acid, due to good hydrophilic properties, significantly reduces the vapor flow rate. According to the results, the lowest water vapor permeability is for 10% of oleic acid in the film. According to the results, the amount of tensile strength decreased with increasing oleic acid content. On the other hand, elongation has increased with the increase of oleic acid, and this again decreased in the film with 15% oleic acid. Oleic acid is a short-chain fatty acid, so it can be located between the amylose and amylopectin strands as a plasticizer and because of this, the amount of hydrogen cross link in the film has decreased and its resistance has decreased. Subsequently tensile stress of film increased due to the good and proper distribution of oleic acid in the film. But at the level of 15%, this amount of oleic acid was high, increasing the gap between the amylose and amylopectin strands, followed by weakened films, and both the tensile strength and long elongation were reduced. Regarding the parameters obtained in the film production (mechanical strength and transparency and water vapor permeability) the film formulation with 10% oleic acid was selected and the solutions with total solid of 8%, 10% and 12% for Greengage coating are selected. It is observed that weight loss for coated samples is less than the control sample. These results confirm the starch barrier against the passage of oxygen and carbon dioxide. In all treatments pH has increased over time. The increase in pH in the control sample is than the coated samples because of different respiration rates. Coated sample is a suitable gass barrier followed by reduce the amount of respiration rate, resulting in a slower rate of pH change. In the third and fourth weeks, changes were significant, and in the control samples, the amount of light was higher and the green’s index in them decreased. Color changes in fruits can take place due to loss of moisture and chemical and enzymes reactions. Proteolytic enzymes such as polyphenol oxidase can destroy phenolic compounds that affect color. According to the results, the highest weight loss and moisture loss associated with the control sample showed the highest rigidity over time, which significantly reduced these changes with coating the sample. It seems that the concentration of 10 and 12% of oxidized starch and oleic acid emulsion can be used for proper coating with the least loss of weight and color. Due to the fact that the oxidized starch is very transparent and has a low viscosity, its appearance is not negatively affected and can be used in food coatings.
Maryam Ebrahimi; Morteza Khomeiri; Yahya Maghsoudlou
Abstract
Introduction:Toxigenic fungi such as A. flavus grow widely in peanut and produce aflatoxins, a group of carcinogenic metabolites. Aflatoxin produced in peanut differed from the genetic variety of plant. The high humidity and moderate temperatures in the subtropical Caspian littoral of northern Iran could ...
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Introduction:Toxigenic fungi such as A. flavus grow widely in peanut and produce aflatoxins, a group of carcinogenic metabolites. Aflatoxin produced in peanut differed from the genetic variety of plant. The high humidity and moderate temperatures in the subtropical Caspian littoral of northern Iran could increase the growth of A. flavus and the production of aflatoxin. The objectives of this study were 1) to determine the chemical composition of peanut cultivars grown in Golestan Province, Iran, 2)to select resistant variety of peanut to aflaoxigenic A. flavus growth and 3) to evaluate relationship between A. flavus growth and changes in oleic and linoleic acid content and peroxide value. Materials and method: Peanut samples were used from four important varieties of peanut, Goli, Mahalli, China and India. those have been harvested from farms in Golestan province, Iran. Fat, protein, ash, moisture, reducing sugar, AFB1 content and peroxide value in each sample were measured by the standard method of AOAC. Fatty acids of the peanut seed oil were analyzed using gas chromatography (GC, Varian CP-3800 model) with a flame ionization detector (FID) and a DB-WAX column (50 m × 0.32 mm ×0.2 µm). To study the effects of A. flavus on peanut varieties, they were sterilized with 0.5% NaClO solution and then one ml of A. flavus spore suspension was added to every 20gr disinfected peanut and was placed in the incubator for eight days at 26°C. After incubation, the number of seeds colonized by fungi, spore production, AFB1 production, the association between colonization rate of hydrolysis of fatty acids and peroxide value were determined.Results and Discussion: The results showed that there were significant differences (P
