Food Engineering
Sajad Jafarzadeh; Mohsen Azadbakht; Faryal Varasteh; Mohammad Vahedi Torshizi
Abstract
Since persimmon is a pressure-sensitive fruit and it is difficult to store this fruit in warehouses, in this research, an attempt has been made to examine the parameters affecting the reduction of changes in its physical properties. The samples were loaded at 150 and 250 N, three types of foam container ...
Read More
Since persimmon is a pressure-sensitive fruit and it is difficult to store this fruit in warehouses, in this research, an attempt has been made to examine the parameters affecting the reduction of changes in its physical properties. The samples were loaded at 150 and 250 N, three types of foam container packaging with polyolefin film, polyethylene-terephthalate, and ordinary box, and four types of polyamine putrescine coating with concentrations of 1 and 2 mM, distilled water and uncoated. Properties such as Physiological Weight Loss, volume, and the density of persimmon fruit, as well as the firmness of this fruit in the prepost-storage stage were examined. The results showed, the highest firmness was obtained in the treatment of putrescine at a concentration of 1 mM and a foam container with polyethylene film with a value of 6.5 N, which was almost three times the firmness of uncoated fruits. The lowest Physiological Weight Loss, volume, and density were obtained in the same type of coating and packaging. The values of these parameters were 2.458%, 1.82, and 0.833%, respectively, compared to the first day of storage. Overall, the use of polyamine treatment showed a significant effect on changes in the physical properties of persimmon fruit, and foam containers with polyolefin film emerged as the optimal packaging option, resulting in the least amount of change among the different types of packaging used.
Soheyl Reyhani Poul; Sakineh Yeganeh; Reza Safari
Abstract
[1]Introduction: Nisin is one of the antimicrobial substances that is used today as a preservative in various foodstuffs. It is a bacteriocin comprised of 34 amino acids and a molecular weight of 3.5 Da. With all the benefits of nisin, there are barriers to its use in dairy and protein rich products. ...
Read More
[1]Introduction: Nisin is one of the antimicrobial substances that is used today as a preservative in various foodstuffs. It is a bacteriocin comprised of 34 amino acids and a molecular weight of 3.5 Da. With all the benefits of nisin, there are barriers to its use in dairy and protein rich products. One of these barriers is the combination of nisin with fats, proteins and sugars and the consequent reduction of its antibacterial activity. In the food science and industry, the use of the technique of encapsulation and production of liposome is the best possible solution in such cases. Also, by adding an antimicrobial agent such as chitosan to the coating of nanoliposomes, the antibacterial activity of the product may be increased. The aim of the present research was to produce nanoliposomes carrying nisin with (and without) chitosan coating and to evaluate the physical and antibacterial properties against two gram-positive bacteria, Bacillus cereus and Staphylococcus aureus. Materials and Methods: In this study, four treatments of nanoliposomes carrying nisin (NN), nanoliposomes carrying nisin coated with chitosan 0.05% ((NN-CH (0.05)), nanoliposomes carrying nisin coated with chitosan 0.1% (NN-CH (0.1)) and nanoliposomes carrying nisin coated with chitosan 0.5% (NN-CH (0.5)) were prepared and examined in terms of physical properties (average particle size, particle dispersity index, zeta potential and encapsulation efficiency) and antibacterial activity (against two gram-positive bacteria, Bacillus cereus and Staphylococcus aureus with two diffusion methods in agar medium and microdilution test). This research was conducted in a completely randomized design and SPSS and EXCEL softwares were used for statistical analysis and drawing of diagram, respectively. Data were analyzed by one-way analysis of variance and the difference between the means was evaluated by Duncan's test at 95% confidence level. Results and Discussion: The results showed that the average particle sizein different treatments with each other are significantly different (P<0.05) and vary from about 110 to 327nm; Also as the amount of chitosan in the coating increased, the particle size increased (P<0.05). This indicates the successful binding of chitosan to the surface of the nanoliposome, which results in the formation of a layer around the nanoliposome and an increase in particle size. Particle dispersity index was recorded less than 0.3 in all treatments and was not related to the amount of chitosan in the coating. With increasing the amount of chitosan in the coating of nanoliposomes, zeta potential increased significantly (P<0.05). This index changed from -55.34 in NN treatment to 53.14 mV in NN-CH (0.5) treatment. In fact, chitosan as a cationic polysaccharide changes the potential to positive values. As the amount of chitosan in coating of nanoliposomes increased, the encapsulation efficiency increased significantly in the treatments (P<0.05); this index increased from 32.19% in NN treatment to 75.14% in NN-CH (0.5) treatment. The results of the antibacterial activity of nisin in two methods of diffusion in agar medium and microdilution test showed that its antibacterial activity increased with nanoencapsulation of nisin with (and without) chitosan coating (p<0.05). Also, with the increase in chitosan concentration, the antibacterial activity of carrier nanoliposomes increased and the highest antibacterial activity was recorded in NN-CH (0.5) treatment (p<0.05). The diameter of the non-growth halo of Bacillus cereus against the research treatments (with five concentrations of 2.5 to 25 μg/ml) varied from about 4.5 to 17.5 mm. This amount for Staphylococcus aureus was recorded from 2.1 to 26.5 mm. By increasing the concentration of nisin and carrier nanoliposomes, the diameter of the halo of non-growth of both bacteria increased significantly (p<0.05). But an exception was recorded in this case; The diameter of the non-growth halo for Staphylococcus aureus in two concentrations of 2.5 and 5 μg/ml of treatments was the same and had no significant difference (p>0.05). The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the examined treatments for Bacillus cereus were in the range of 100 to 400 and 200 to 500 μg/ml, respectively. These two concentrations for Staphylococcus aureus were recorded as 50 to 200 and 100 to 400 μg/ml respectively. Based on the values of diameter of non-growth halo, MIC and MBC it can be claimed that Bacillus cereus is more resistant to the examined treatments than Staphylococcus aureus.Nanoencapsulation of nisin in the form of carrier nanoliposomes with chitosan coating is a suitable solution to improve its physical and antibacterial properties. In such a way that by increasing the concentration of chitosan in the coating, both of the aforementioned properties improved significantly. Nanoliposomes carrying nisin with (and without) chitosan coating have the ability to inhibit the growth and killing Bacillus cereus and Staphylococcus aureus bacteria. The antibacterial activity increases with the increase in nisin and carrier nanoliposomes concentrations. The value of non-growth halo, minimum inhibitory concentration and minimum bactericidal concentration confirm that Bacillus cereus is more resistant to nisin and its carrier nanoliposomes than Staphylococcus aureus.
Zohreh Didar
Abstract
Introduction: Nowadays, edible packaging founds great attention due to environmental issues related to synthetic packaging materials. Gelatin is one of the most commonly ingredients used in edible packaging formulation due to its good barrier properties against gases and UV irradiation. Addition of plant ...
Read More
Introduction: Nowadays, edible packaging founds great attention due to environmental issues related to synthetic packaging materials. Gelatin is one of the most commonly ingredients used in edible packaging formulation due to its good barrier properties against gases and UV irradiation. Addition of plant extracts or essential oils is one approach for confer antimicrobial activity to edible films. The aim of this study was to use different percentages (5-100%) of turmeric hydrosol in the formulation of edible gelatin films and assessing the various properties of the resulted film. Materials and methods: Extraction of turmeric hydrosol was done by Clevenger apparatus. Separation of the essential oil from hydrosol was done by a separating funnel. For preparation of gelatin films, 4g gelatin was dissolved in 100ml distilled water, and glycerol as plasticizer was added at ratio of 25w/w gelatin. In gelatin films included turmeric hydrosol, substitution of turmeric hydrosol instead of distilled water in the ratio of 5-100% was performed. Then, the mixture was poured in plexiglass plates (80×120 mm) and dried at 22ºC, 50% RH for 48h.Texture analysis was carried out using the texture analyzer TA-XT plus. The water vapor permeability (WVP) was measured using gravimetrically method. Light transmission was determined by spectrophotometer jenway 6305 at 200-800 nm wavelength. Morphological assessment was performed by scanning electron microscope (phenom proX). For Fourier-transform infrared spectroscopy analysis, Perkin-Elmer (Spectroma2 model) at 4000-4500 cm-1 frequency, used. Antimicrobial test was done by measurement inhibitory zone (mm) of edible films against Staphylococcus aureus (PTCC 1112), Staphylococcus saprophyticus (PTCC 1440) and Staphylococcus epidermium (PTCC 1435).The studied bacteria (Staphylococcus aureus, Staphylococcus saprophyticus and Staphylococcus epidermium) were purchased from the Iranian Scientific and Industrial Research Center and transferred to the suitable medium in sterile condition and incubated at 37°C for 32 hours. Microbial cells were harvested by centrifugation at 4000 rpm. For the estimation of microbial population, McFarland turbidity method was applied. First, the results from comparing turbidity showed the population of microorganisms was equal to 0/5 McFarland solution (approximately 1/5×108 CFU/ml), then for reaching to the desired microbial population (1/5 × 106 CFU/ml), dilution with physiological saline was done. Agar disc diffusion method was used for assessing the antimicrobial effect of the gelatin films. Gelatin films were cut into a 10mm diameter in aseptic condition using a circular knife and then placed on agar plates inoculated with 100µL of tested bacteria (with approximately 106 CFU/mL). The plates were then incubated (37ºC, 24h). The diameter of the inhibition zone was precisely measured using a digital micrometer (Guanglu model 701-211). Each experiment was performed triplicate. Results and discussion: The results of this study showed that the use of turmeric hydrosol causes significant difference on mechanical and physical properties of related gelatin films (p≤0.01). The stress tension was increased by adding hydrosol to the edible film formulation, but the elongation percentage of the edible film decreased. The highest the stress tension was observed in sample containing 100% hydrosol (33.3 Mpa) but the lowest elongation percentage also was belong to this sample (96%). Addition of hydrosol to film formulation cause increasing of UV-radiation barrier property and reducing the transparency of the film. FTIR analysis of gelatin films included turmeric hydrosol, exhibited the existence of aromatic bonds according to appearing peak at 680cm-1. Structural studies by SEM method, showed uniformity in the structure of different gelatin films and hydrosol addition cause minor changes in the structure of films. The water vapor permeability was influenced by the edible film formulation and by adding different percentages of turmeric hydrosol, the permeability to water vapor, decreased (p≤0.01).Thickness was also affected by gelatin formulation and hydrosol caused reduction the thickness. Antimicrobial assessments showed that the addition of turmeric hydrosol cause inhibitory effects against studied staphylococcus strains. Staphylococcus aureus and Staphylococcus saprophyticus showed the highest susceptibility to hydrosol included films (inhibition zone equal to 37 mm for gelatin film included 100% turmeric hydrosol).
Hossein Jooyandeh; Erfan Danesh; Mostafa Goudarzi
Abstract
Introduction: Health-conscious consumers are interested in eating dairy products including ice cream with less fat. As a consequence, the dairy industry has developed a variety of reduced-fat ice cream products. However, quality aspects of many of these products do not meet consumer expectations for ...
Read More
Introduction: Health-conscious consumers are interested in eating dairy products including ice cream with less fat. As a consequence, the dairy industry has developed a variety of reduced-fat ice cream products. However, quality aspects of many of these products do not meet consumer expectations for ice cream flavor, texture, and appearance. The formation of the ice cream structure is hindered when the fat content is reduced and attributes related to quality, such as viscosity, ice crystallization, hardness, melting rate and flavor, are affected. Low melting resistance, high firmness and undesirable flavor are the most cited defects in reduced-fat ice creams. Enzymatic treatment of reduced-fat milk with microbial transglutaminase has been found to improve the textural and sensory properties of the final dairy products. The transglutaminase enzyme (MTGase; protein-glutamine gamma glutamyl transferase, EC 2.3.2.13) catalyses “acyl” transfer reactions between γ-carboxyamide groups of glutamine residues (acyl donor) and the ɛ-amino group of lysines (acyl acceptor) in proteins, leading to inter- or intra-molecular cross-linking. The enzyme-catalyzed cross-linking of milk proteins results in the formation of high molecular weight polymers that not only are able to lower the melting rate thorough increasing the viscosity of ice cream mix, but they could also provide a smoother texture for the product by mechanically obstructing ice crystal growth. However, the extensive cross-linking of milk proteins may even adversely affect the physical properties of the resultant ice cream and thus, the added amount of enzyme needs to be adequate for the desired effects. The aim of this study was to investigate the effects of different concentrations of TGase enzyme on physical and sensory properties of light ice cream in order to selct the appropriate amount of enzyme concentration that provides the best results.
Materials and methods: The light ice cream (5% w/w fat) was treated with different concentrations of TGase enzyme (2, 4 and 6 units/g milk protein). The enzyme-treated samples were investigated for flow behavior characteristics (apparent viscosity, flow index, consistency index), overrun, melting rate, hardness and sensory properties (flavor, texture, color and total acceptability) in comparison with control light ice cream with no added Tgase.
Results and discussion: The results revealed that TGase treatment effectively increased the viscosity of light ice cream.The higher the enzyme concentration, the greater the viscosity of ice cream samples. This could be attributed to TGase-catalyzed formation of large protein polymers in ice cream mix that resist to flow. All enzyme-treated ice cream mixes exhibited shear-thinning behavior, where the viscosity decreased with increasing shear rate. The power law model was used to find consistency and flow indices for different treatments. The results showed that consistency index increased and flow behavior index decreased with TGase concentration. The stronger shear-thinning behavior (lower flow index) of the samples treated with higher concentration of TGase might be arisen from formation of higher number of large protein polymers in theses samples, which decrease in size during shearing. The enzyme treatment significantly increased the overrun of the light ice cream that could be due to the increasing effect of TGaes on the viscosity. The increase in viscosity promotes the retention of air in the ice cream which is concomitant with increased overrun; however, high viscosity reduces the whipping rate leading to lower incorporation of air into the ice cream and thus decreased overrun. This may account for significantly lower overrun of the light ice cream treated with 6 units TGase/g milk protein than the samples treated with 4 units TGase /g milk protein. It was observed that the enzyme treatment caused a significant improvement in melting resistance of light ice cream. In fact, the light ice cream treated with 6 or 4 units TGase /g milk protein took the longest time to melt, followed by the samples treated with 2 and 0 units TGase /g milk protein. This is somehow in accordance with the results of overrun; that is, the ice cream with higher overrun melted slower attributed to a reduced rate of heat transfer due to a larger volume of air. The overrun could also affect the hardness of ice cream as evidenced by the results of the present study. The results showed that the samples with greater overrun were softer. It could be assumed that the air cells, together with large protein polymers formed via catalytic action of TGase, limited the size of ice crystals by exerting mechanical hindrance, providing a softer texture for the enzyme-treated ice creams. Not surprisingly, the enzyme treatment did not considerably influence the flavor of light ice cream albeit the sample treated with 6 units TGase /g milk protein received significantly lower score than the other samples. Conversely, the color of enzyme-treated samples was more appreciated by consumers than the sample without added TGase possibly because of light scattering properties of enzymatically formed protein polymers in theses samples. Consistent with the results of physical properties, the texture of light ice cream treated with 4 or 6 units TGase /g milk protein were ranked as the most desirable samples, followed by the samples treated with 2 and 0 units TGase /g milk protein. The order of light ice cream samples for total acceptability scores was the same as that for texture scores with the exception of the sample treated with 6 units TGase /g milk protein whose total acceptability score was lower than the sample treated with 4 units TGase /g milk protein.
Fatemeh Tabari kouchaksaraei; Masoud Rezaei; Peyman Aryaee; Mehdi Abdollahi
Abstract
Introduction: An edible film is a thin layer, made of edible materials, which once formed can be placed on, or between food components. Protecting the product from mechanical, physical and chemical damages, as well as microbiological activities, are some of its functions (Falguera et al, 2011). The main ...
Read More
Introduction: An edible film is a thin layer, made of edible materials, which once formed can be placed on, or between food components. Protecting the product from mechanical, physical and chemical damages, as well as microbiological activities, are some of its functions (Falguera et al, 2011). The main materials made of these films are proteins, lipids and polysaccharides which are able to be used as alone or in blending form (Hernandez et al, 2008 ;Gennadios, 2004). Carboxymethylcellulose (CMC), is a linear polysaccharide that its natural and biodegradable features cause to exhibit excellent film-forming properties (De Moura et al, 2011). Films prepared with these polymers, generally have good gas barrier properties and moderate to propriate mechanical features (Gutierrez et al, 2012). Using the edible, biodegradable films, due to the sensibility to moisture and poor mechanical properties particularly in moist status, is almost limited (Wang et al, 2009; Silva et al, 2009). Because of high hydrophilic property, CMC films also have a low resistant rate to water vapor permeability (Mohanty et al, 2000). Gum Tragacanth (Astragalus sp.) is another polysaccharide used to produce edible films and coatings. This gum can be widely used as a stabilizer, emulsifier and thickener in food industry, pharmaceutics and cosmetics (Azarikia & Abbasi, 2010). Tragacanth also has a prominent effect on physical and mechanical properties of the potato starch-based edible films (Fazel et al., 2002). It has also a proper blending potential in blending with other hydrocolloids, carbohydrates and most of proteins and lipids (Farahnaki et al., 2009). Yet, not any researches has made about the effect of blending tragacanth gum with other carbohydrate polymers. Blending of polymers can enhance the functional properties of the produced films (Bourtoom, 2008). Hereby, the current study has been done in order to preparate the best edible film with suitable physical, mechanical and biodegradable properties and has tried to introduce an ideal blend film made of different rates of carboxy methyl cellulose and tragacanth. Material and methods: In this research in order to improve the physico-chemical characteristics of biodegradable edible films, blending two polymers of carboxymethyl cellulose (CMC) and tragacanth (Astragalus sp.) was studied. At first, it was tried to making the film. For this purpose in laboratory the solubles of CMC 1% w/w and tragacanth of 0/75% w/w were prepared. In order to dissolute the polymers, both polymers subjected to heat (75 օC) and following the temperature decrease (~ 40 օC), glycerol (20% of the polymer) was added to each one. Therefore, CMC and tragacanth were blended to each other at proportions of 25:75, 50:50, and 75:25 (v/v) and water vapor permeability, solubility, mechanical properties and microstructure were evaluated. Microstructure of the produced films was assigned by an electronic microscope (Philips, made in Netherlands). Thickness of samples was determined by a digital balance (0/0001 mm, Mitutoyo- made in Japan) via measuring in five points of each sample. Water vapor permeability, moisture content and solubility rate were conducted by standard. Tensile strength (TS) and elongation at break (EAB) were determined using an Instron universal testing machine (Model TVT 300 Xp, Sweden) operated according to the ASTM standard method D882-01(ASTM, 2002). Statistical Analysis performed by software of SPSS, ver. 20. Normality of data and homogeneity of data were conducted by Kolmogorov-Smirnov and Levene tests, respectively. For significance of treatments effect One-Way Anova and for statistical comparison of data Duncan test were performed. Results and discussion: The results showed that blended film of 50:50, as well as pure CMC film, had a smooth, flat surface without crack, showing that both polymers were properly blended. Among three blend proportions of two polymers, tensile strength was greatest in 50:50 whereas this amount in proportions of 50:50, 75:25 and 25:75 was recorded 44.59, 32.82 and 26.59 MPa, respectively. These results were in line with Ghanbarzadeh et al. (2011), who indicated the quality of maize starch-based films was suited by CMC and citric acid. With decrease of CMC content in blended films the elongation rate of films significantly decreased. This can be attributed to suitable interactions of the two polymers. This is in accordance with report of Tongdeesoontorn et al. (2011) and Mu et al. (2012), who found the different contents of CMC positively affected the films properties. Water vapor permeability was of better status at 50:50 and 25:75 than at 75:25. Solubility in water did not differ among three blend films but it had better conditions in pure CMC film whereas the blend films showed a decrease about 52 to 58% in solubility compared to the pure CMC film. The results of our research is consistent with findings of Tong et al. (2008), who investigated preparation and properties of pullulan -alginate- CMC blend films. The decrease of solubility can probably be due to proper interactions between CMC and tragacanth. Likewise, blending two polymers at different proportions decreased the moisture content of films. It can be stated that because of the linkages between tragacanth and carboxymethyl cellulose polymer chains, a compact structure has been created that not allows water molecules to presence and thus leads to a reduction in moisture content of films. This is in accordance with findings of Gutierrez et al. (2012), who reported that the increase of leaf extract in plant of murta improved the quality properties of the CMC films. Generally, from this investigation it is deduced that blending the two polymers in different proportions can improve some physico-chemical properties of the CMC- tragacanth edible film.
Seyed Mohammad Ali Razavi; Mostafa Mazaheri Tehrani; Bahareh Emadzadeh
Abstract
Introduction: Recently, consumers have directed their interest towards low fat products as they associated them with a reduced risk of well-known health problems such as obesity and coronary heart diseases. Fat is a multifunctional ingredient in ice cream system. Thus, in attempts to provide desirable ...
Read More
Introduction: Recently, consumers have directed their interest towards low fat products as they associated them with a reduced risk of well-known health problems such as obesity and coronary heart diseases. Fat is a multifunctional ingredient in ice cream system. Thus, in attempts to provide desirable flavor and physical characteristics of full fat ice cream, manufactures looking for fat replacers (Drake et al. 1999). Hydrocolloids have functionalities such as thickening, gelling, fat replacing, which allow them to use in different industries (Roller and Jones, 1996; Williams and Phillips, 2000). Guar gum is used as a stabilizer in ice cream and provides smoothness in texture, retards ice crystal growth, and increases freeze-thaw stability (Wielinga, 2000). The rheological properties and potential of basil seed gum (Rayhan) as a novel stabilizer for structure formation and reducer for ice recrystallization in regular ice cream have been recently investigated (Hosseini-Parvar, 1388; Bahram-Parvar, 1391). In this research, the physicalproperties of light (5% fat) and low fat (2.5% fat) ice creams as a result of replacement of milk fat by guar gum (as a commercial hydrocolloid), basil seed gum (as a novel hydrocolloid) and their blend (50:50) at different concentrations were investigated and compared to those of control sample (10% fat). Materials and methods:The ice cream formulations were prepared based on the following composition: 2.5% (L), or 5% (R) or 10% (B) milk fat, 11% MSNF, 15% sugar, 0.1% vanilla, 0.15% emulsifierand 0.35%, 0.45%, 0.50% or 0.55% selected gums (guar gum, basil seed gum or blend (50:50) of them). Liquid materials including milk and cream were mixed together and warmed up to 50˚C. After that, the pre-weighed and mixed dry ingredients were dispersed into them, under agitation. The mixes were pasteurized at 80˚C for 25 s, homogenized at 23000 rpm for 2 min, cooled rapidly to 5˚C and then aged at constant temperature overnight (12 h) at 5˚C. The freezing was carried out in a batch soft ice cream maker. Apparent viscosity of ice cream mixes were evaluated using a rotational viscometer at 5˚C and 51.8 s-1. Before melting rate determination, samples were tempered at –18°C overnight, Ice cream samples (30 g) were put on a wire screen mesh and allowed to melt at ambient temperature. Melting rates were measured from the slop of linear portion of drained mass vs.time graphs. The pH values for mix samples were measured with a pH meter. After the mix was frozen in a batch freezer, Draw temperature of ice creams was obtained using a digital thermometer.Mix and ice cream samples (3 g) were diluted 1: 500 in two steps with deionized water and absorbance was measured by a spectrophotometer at 540 nm. Turbidity (%) was calculated as (absorbance in mix - absorbance in ice cream)/absorbance in mix 100%. A known volume of ice cream and mix were weight and overrun was determined as (weight of the mix - weight of the ice cream)/ weight of the mix 100%. Results & discussion: Reducing fat in any food formulation will cause a decrease in viscosity (Cody et al., 2007). Fat reduction decreased apparent viscosity (P0.05), ranging from 6.31 to 6.34. Draw temperature as a measure of freezing point of ice cream is dependent on the type and concentration of the soluble constituents and varies with the composition. Addition of some ingredients such as sweeteners, lactose and salts decrease the freezing point. Fat is immiscible with the aqueous phase and carbohydrate polymers are very large molecules, depression of the freezing point is caused indirectly by using of these materials, as a result of decreasing the water content (Marshall and Arbuckle, 1996). In this study, a reduction of fat content of full fat ice cream resulted in higher draw temperature. However, there was not a specific trend in the temperature values of samples with same fat content and different fat replacer levels. There was no significant difference between turbidity of samples with same kind of gum. Similar results were obtained by Schmidt et al. (1993), which related to sufficient amount of milk fat (2.1 and 4.8 %), milk proteins and emulsifiers in ice cream formulations. Conclution: Decreasing the fat content generally caused an increase in the value of overrun. But, very high viscosity of mix may prevent vigorous agitation and air incorporation that seems the reason of why increasing fat replacer concentration resulted in overrun reduction
Amir Jajarmi; Masoud Taghizadeh
Abstract
Introduction: Lime (Citrus aurantifolia L) is belonged to citrus family and has two varieties on the basis of sweet or sour taste; two well known varieties of sour lime are Persian and Key that are cultivated in the southern of Iran. Based on FAO statistics, Iran produced about 615,000 tons of lime in ...
Read More
Introduction: Lime (Citrus aurantifolia L) is belonged to citrus family and has two varieties on the basis of sweet or sour taste; two well known varieties of sour lime are Persian and Key that are cultivated in the southern of Iran. Based on FAO statistics, Iran produced about 615,000 tons of lime in 2010, and is ranked among 10 lime producersinworld wide. Physical properties of fruits are essential information in designing equipments and processes being used in different manufacturing stages such as harvesting, cleaning, sorting and grading, transporting, packaging, as well as estimating of cooling and heating loads during heat transfer processes. Moreover, physical properties affect products acceptability since consumers usually prefer fruits and vegetables with brighter color, appropriate size and uniform shape. Among physical properties, weight, volume and projected area are important parameters for designing sorting equipment.Materials and methods: In this study, lime samples were selected from Key variety which is cultivated in southern of Iran. From the whole, physical properties of about 300 limes were investigated and regression model were developedto estimate weight and volume on the basis of length, width, thickness and projected area.In order to determine the initial moisture, tenlime samples were randomly selected and taken in to hot air oven at 80C for 24 h. The average values of three replicateswerereported.The major dimensions (Length (L), width (W), thickness (T)) were measured using a micrometer with an accuracy of 0.01 mm.Projected area of limes was calculated in three dimensions using image processing technique. Apparent color for the lime samples was also measured in terms of CIE ‘L*’ (lightness), “a*” (redness and greenness) and “b*” (yellowness and blueness), using image processing techniques. Step wise regression was used to develop multivariate models. In this method, the independent variables would enter the equation successively based upon their degree of dependency. In order to estimate weight and volume of lime samples,three category modelswere developed as follow. 1- Regression models based on length, width and thickness. 2-Regression models for predicting weight of lime based on calculated volume. 3- Regression models based on projected area. When there are a large number of variables in the database, it is very likely that subsets of variables are highly correlated with each other.In this study, principle component analysis (PCA)was applied in order to have an accurate and reliable evaluation from existed correlation between physical properties of lime.Result and discussion: The initialmoisture content of limeswas found to be 84.34%.The averaged values of length, width and thickness of limes were35.84, 32.92 and 32.56, respectively. The static coefficient of friction for limes was determined on fourdifferent surfaces namely plywood, galvanized iron sheet, rubber and glass. The glass and plywood showedmaximum and minimum static coefficient of friction respectively. In addition, the sphericity and aspect ratio of lime were found to be 94.32% and 92.18%, respectively. The obtained sphericityvalues were similar to values reported by Sharifi et al., (2007) for orange variety of Tamson and lower than orange varieties of Navel reported by Topuz et al., (2006). The obtained results showed high correlation between three major dimensions and lime’s weight. The predictive models for lime have lower coefficient in comparison with LorestaniandTabatabaeefar(2006) research report forheterogeneous shape of limes. Among regression models for weight prediction of limes, the best model was obtained on the basis of the third projected area with R2of 0.921. The regression models on the basis of calculated volume showed appropriate performance for prediction of lime’s weight. Among regression models on the basis of dimensions, the single parameter model based on lime’s width found to bethe highest coefficient for prediction of volume. Similar toweight prediction, single parameter model on the basis of the third projected area showed the best performance for volume prediction. Conclusion: The results obtained from principle component analysis confirmed the regression models and showed high correlation between physical properties such as projected area, dimension, weight and volume with each other as well as positive correlation with coefficient of friction on the rubber surface and negative correlation on theglass surface.
Hadi Almasi; Babak Ghanbarzadeh; Jalal Dehghan nia; Ali Akbar Entezami; Asghar Khosrowshahi Asl
Abstract
Fatty acid modified cellulose nanofibers (MCNFs) and TBHQ antioxidant were added to poly(lactic acid) (PLA) film. The combined effects of the MCNFs and TBHQ on the morphological, thermal, mechanical and barrier properties of PLA film were analyzed. The morphology of fracture surfaces evaluated by field ...
Read More
Fatty acid modified cellulose nanofibers (MCNFs) and TBHQ antioxidant were added to poly(lactic acid) (PLA) film. The combined effects of the MCNFs and TBHQ on the morphological, thermal, mechanical and barrier properties of PLA film were analyzed. The morphology of fracture surfaces evaluated by field emission scanning electron microscopy (FE-SEM). XRD results showed that the crystallinity of the PLA film with added MCNFs was substantially higher than that of pure PLA and antioxidant active PLA films. Glass transition and melting temperatures changed with the addition of these two components. The addition of 3wt% of TBHQ to PLA films leads to a significant reduction (p
Hassan Safiyari; Ali Asghar Zomorodian; Hossein Rahmanian; Farhad Salmanizade
Abstract
Physical properties are often required for designing post harvest handling and processing equipment for agricultural products. Persimmon (khormandy cultivar) is rich in vitamin A, calcium, potassium, tannic acid and antioxidant phenolic compounds. In this study changes in the physical properties of persimmon ...
Read More
Physical properties are often required for designing post harvest handling and processing equipment for agricultural products. Persimmon (khormandy cultivar) is rich in vitamin A, calcium, potassium, tannic acid and antioxidant phenolic compounds. In this study changes in the physical properties of persimmon fruit during storage were studied. Properties such as fruit dimensions, mass, geometric mean diameter, arithmetic mean diameter, equivalent diameter, sphericity, aspect ratio, surface area, volume and the static coefficient of friction on three surfaces (plywood, glass, and the galvanized iron sheet) were investigated. The results showed that the mean values of all physical properties decreased with increasing storage time. Experiments were carried out at initial moisture content of 44.26% d.b. Dimensions decreased from 56.01 to 52.57 mm in length, 54.19 to 50.01 mm in width, and 36.72 to 32.48 mm in thickness during storage time. Arithmetic mean diameter, geometric mean diameter and equivalent diameter varied from 48.07 to 44.06 mm, 48.95 to 45.06 mm, and 48.7 to 44.75 mm, respectively. The results also revealed that with increasing in storage time, the sphericity, the aspect ratio and the surface area of persimmon fruits were decreased from 0.859 to 0.8383, 0.6548 to 0.6211 and 72.99 to 61.41 mm2, respectively, while average volume and mass ranged from 59.18 to 45.79 mm3 and 72.8 to 65.45 g, respectively. Also, the static coefficient of friction on all surfaces increased significantly during the storage time.
