Food Technology
Elham Safaei; Hannan Lashkari; Sara Ansari; Alireza Shirazinejad
Abstract
Introduction Manufacturers are trying to replace plastic materials in the food packaging industry with biodegradable and edible films. Biodegradable edible films and coatings are mainly made from carbohydrates, lipids and proteins and their mixtures. In recent decades, various carbohydrates from ...
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Introduction Manufacturers are trying to replace plastic materials in the food packaging industry with biodegradable and edible films. Biodegradable edible films and coatings are mainly made from carbohydrates, lipids and proteins and their mixtures. In recent decades, various carbohydrates from plant sources have been investigated and introduced as new compounds for the preparation of these films. Flaxseed gum is a white to cream-colored powder that dissolves in water and produces a gel, and is a desirable compound for forming films and coatings. Recently, through the integration of reinforcements or fillers with at least one nanometer dimension in the substrate of one or more natural biopolymers, the physicochemical, mechanical, optical, thermal and barrier properties of pure biofilms have been improved. The use of cellulose nanoparticles in biofilms as a reinforcing agent for polymer materials leads to the creation of composite films with better quality characteristics and leads to the creation of functionalization activities in film production. Therefore, the aim of this research was to produce and characterize edible and biodegradable film based on the combination of flaxseed gum and cellulose nanocrystals. Materials and Methods Cellulose nanocrystals (Degree of crystallinity: 42% and average particle size: 58 nm) were extracted from cotton linters. Glycerol and other chemicals used for this research were obtained from Merck, Germany. Flaxseeds were purchased from the local market of Shiraz (Iran). Bionanocomposite films were prepared from different ratios (0:100, 30:70, 50:50, 70:30 and 100:0) of flaxseed mucilage (2% w/v) and cellulose nanocrystal (6% w/v) solutions. The prepared solutions were poured on a petri dish with a diameter of 15 cm and dried in an oven at 80°C for 4 hours. Their physical, color and mechanical properties were investigated and the best ratio was selected for the preparation of bionanocomposite film. The produced films were subjected to different analysis to determine thickness, solubility, water absorption capacity, permeability to water vapor, tensile strength, elongation at break point, and colorimetry. The microstructure of the produced film was studied using a scanning electron microscopy (SEM).The average data were analyzed by analysis of variance in a completely randomized design using SPSS 22.0 software. Differences between treatments were expressed in Duncan's multiple range test at the 95% probability level (p<0.05) and the corresponding graphs were drawn with Excel 2013. Results and Discussion The results of the film thickness test showed that the film containing 100% mucilage has the lowest thickness and with the addition of cellulose nanocrystals, the thickness increased significantly (p<0.05). The results of the water solubility and water absorption capacity of the film samples showed that the addition of cellulose nanocrystals to the flaxseed mucilage film initially led to a significant decrease in the water solubility and water absorption capacity (p<0.05), so that the lowest level ofthese two physical parameters were obtained in the film containing the combination of 70% flaxseed mucilage and 30% cellulose nanocrystal, and then with the increase of cellulose nanocrystals, an increase in water solubility and water absorption capacity of the films was observed. Nanocrystal cellulose at low levels (30%) acted as a filler and was uniformly dispersed in the network of the film and by filling the empty pores of the biopolymer film based on flaxseed mucilage, it caused the transfer of water vapor more complicated and reduced the permeability to water vapor. However, its higher amount increased the permeability of the film to water vapor.The results showed that by adding cellulose nanocrystal to the film based on flaxseed mucilage and increasing its amount, the brightness of the films decreased and the intensity of redness, yellowness and turbidity of the films increased significantly (p<0.05). By combining flaxseed mucilage and cellulose nanocrystals in a ratio of 30:70, the best film was produced in terms of mechanical strength and stability against moisture and water vapor. The SEM image of this film showed a smooth, even surface and a uniform distribution of cellulose nanocrystals in the film network. Conclusion The results finally showed that the combination of flaxseed mucilage and cellulose nanocrystals in a ratio of 30:70 was able to produce a biodegradable and edible film with favorable structural and barrier properties. The characteristics of this film include; thickness (0.313mm), solubility (53.42%), water absorption capacity (44.44%), permeability to water vapor (0.350 g.m-1s-1Pa-1 × 10 -10), tensile strength (0.973 MPa), elongation at break point (30.52%) were obtained. The colorimetric indices L*, a*, b* and turbidity were determined as 79.73, 1.95, 3.48 and 1.335 mm-1 respectively. Acknowledgement The authors would like to express their sincere gratitude to Islamic Azad University, Sarvestan Branch.
Food Technology
Maryam Alsadat Nazemi; Sara Ansari
Abstract
Introduction: Roasting is one of the most important thermal processing to improve the physicochemical and organoleptic properties of nuts. Wild almond, especially roasted wild almond is very sensitive to oxidation due to its high content of unsaturated fatty acids. Lipid oxidation can be inhibited by ...
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Introduction: Roasting is one of the most important thermal processing to improve the physicochemical and organoleptic properties of nuts. Wild almond, especially roasted wild almond is very sensitive to oxidation due to its high content of unsaturated fatty acids. Lipid oxidation can be inhibited by using a suitable packaging material and modifying the atmosphere of the packaging. In this research, the effects of roasting degree (light roasting at 50°C/60 min, medium roasting at 100°C/45 min and dark roasting at 200°C/ 30 min), as well as the presence/ absence of nitrogen gas in two types of pouches including polyethylene (PE) and oriented polypropylene/ cast polypropylene (OPP/CPP) were investigated. The effects of above mentioned treatments were examined using Completely Randomized Design on the moisture, total fat, firmness, peroxide value and conjugated trienes, fatty acid profile and sensory properties during two months storage at 37°C. Materials and Methods: The wild almonds used in this research were collected randomly from the Dasht-e-Arjan region in Fars province (Iran). The debittering process of almonds was done by soaking in 4- 6 % (w/v) of NaCl solution for 12 hours at three consecutive days. A certain amount of debittered wild almonds with a uniform size were roasted at 50°C for 60 minutes (light- roasting), 100°C for 45 minutes (medium- roasting) and 200°C for 30 minutes (dark- roasting) in a laboratory toaster (SSN-2004x, Iran). After cooling at room temperature, samples of 100 g were packed using gas flushing packing machine (90SM4, Shadmehr Co., Iran) in three different conditions: a) air atmosphere (in transparent PE pouches, 70- 75 mm thickness), b) modified atmosphere flushed with N2 gas (in transparent PE pouches, 70- 75 mm thickness), c) modified atmosphere flushed with N2 gas (in two-layer transparent OPP-CPP pouches, 25 and 50 mm thickness of the first and second layer). The samples were stored for two months at 37°C and 7-8% R.H. At definite time intervals, the samples were analyzed for the moisture content by oven drying, total oil content by the soxhlet method, protein content by the Kjeldahl method, and fiber content through chemical gravimetric method. Extraction of oil from the nut samples was carried out using hexane, as described by Kornsteiner et al. (2009). Peroxide value (PV) was determined by the iodometric assay according to IUPAC standard method 2.501. Conjugated trienes were calculated according to IUPAC Official Method 2.205 based on measuring absorbance of a solution containing 0.01-0.03 g of oil in 25 ml of isooctane. The fatty acid composition of wild almond oils was determined by gas chromatography equipped with flame ionization detection. Hardness of the wild almond was evaluated using a Texture Analyzer (CT3-Brookfield, USA). Sensory evaluation of samples was carried out by 30 trained panelists using a five point hedonic scale. Statistical analysis of completely randomized design with three replications and means comparison in 95% confidence level was employed using the SPSS-19 software. Results and Discussion: Analysis of variance indicated that the independent effects of roasting conditions, packaging and storage time and the interaction of roasting conditions and storage time on the mentioned parameters were significant (p<0.01). With roasting at higher temperatures, the moisture content and hardness decreased significantly while the oil, protein and fiber content of wild almond kernels and the peroxide value (PV) and conjugated trienes (CT) of their oils increased significantly. However, the increase in protein and CT for medium and low roasting conditions and the increase in fiber for medium and high roasting conditions were not significant (p>0.05). Moreover, increasing the roasting temperature of wild almond led to a significant increase of palmitic acid and a significant decrease of stearic acid whereas other fatty acids did not change significantly. There was a remarkable increase and then a rapid decrease in the fiber, fat and protein content of all roasted samples during the first and second months of storage, respectively. Whereas the PV and CT of oils increased and the moisture content and hardness decreased significantly during the two- months storage. For each roasting temperature, wild almonds packaged in pouches under N2 had lower PV and CT of oils and the OPP/CPP pouches under N2 had better performance in this regard and retaining moisture, fat, protein, fiber content and texture. At the end of storage with PV of 24.6 (meqO2/kg oil) and K268 of 1.92 the dark-roasted almond sample packaged with PE/air atmosphere was the least stable, and the light-roasted sample packaged with OPP/CPP under N2 with PV of 5.3 (meqO2/kg oil) and K268 of 1.57 was the most stable form against oxidation. According to the results of sensory analysis, the highest overall acceptability score was attributed to the samples roasted at 100°C for 45 minutes.
Sara Karamzadeh; Sara Ansari
Abstract
Introduction: Pectin is a complex mixture of polysaccharides in the primary cell wall of plants which is a polymer of α-galacturonic acid, to which neutral sugar is connected to form aside chain. Pectin is a natural food additive used extensively in the food industry as thickener, texturizer, emulsifier, ...
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Introduction: Pectin is a complex mixture of polysaccharides in the primary cell wall of plants which is a polymer of α-galacturonic acid, to which neutral sugar is connected to form aside chain. Pectin is a natural food additive used extensively in the food industry as thickener, texturizer, emulsifier, stabilizer and gelling agent. In 2018, the world market demand for pectin was in excess of 60,000 tons and Europe was estimated to have the largest market with 31,000 tons (valued about US$420). In Iran, about one hundred tons of pectin is consumed annually in the food and pharmaceutical industries, all of which are supplied from abroad, and due to its price in the world market is of considerable magnitude. Therefore, the study of its production within the country could be of great importance. During processing and canning of eggplant, its cap and skin are discarded as waste which can be considered as a valuable ingredient in the food industry. The main objective of this study was to develop an MAE (Microwave assisted extraction) of pectin from eggplant peel and investigate the effect of process variables (microwave power, irradiation time and pH) and the response (extraction yield, degree of esterification, galacturonic acid content and emulsifying activity); and to obtain optimum conditions for maximum extraction yield of pectin from eggplant peel. The response surface methodology (RSM) using Box-Behnken design was employed in this study. Material and methods: Eggplant peels were provided by Yek-o-Yek factory as an unwanted by-product. Then, the peels were divided into small pieces and dried in hot air oven at 65 °C until it attains constant weight. The peels were then grinded and passed through a 40-mesh sieve to obtain powdered sample. The independent variables examined were microwave power (360–450–540 W), irradiation time (1–2.5–4 min) and solution pH (1–2–3). MAE of pectin was performed in an ordinary household microwave oven with a total of 17 treatments according to RSM. About 5 g of dried eggplant peel powder was weighed and placed into a 250 ml beaker, 75 ml distilled water (the liquid-solid ratio 15:1 v/w) containing different pH values was added and exposed to microwave radiation at different powers for the selected irradiation times. After microwave heating, the mixture in the beaker was allowed to be cooled down and filtered using filter paper (Whatman no-1). The filtered extract was centrifuged and the supernatant was precipitated with an equal volume of 98% (v/v) ethanol. The coagulated pectin mass was washed with 98% (v/v) ethanol for two times and dried in oven at 60 ° C until it attains constant weight. The pectin extraction yield was calculated by dividing the weight of dried pectin to the weight of dried eggplant peel powder. Galactoronic acid content of pectins was determined using the meta-hydroxydiphenyl method. The esterification degree of the pectins was determined by the titrimetric method with minor modifications. The emulsifying activity (EA) of the eggplant peel pectins were analyzed according to the method by Dalev & Simeonova (1995). Optimum extraction conditions to achieve maximum extraction efficiency, degree of esterification, galacturonic acid content and emulsifying activity were determined. Then, the stability of the oil-based emulsion prepared by mixing 0.5% w/w solution of pectin extracted in optimal conditions and corn oil, were examined at 4 and 23 ° C. In addition, the behavior of pectin extracted under optimal conditions (at concentrations of 0.1, 0.2, 1 and 2%) and its spectra using a Fourier transform infrared spectrometer (FTIR) were investigated. Results and discussion: The results indicated that the extraction efficiency, esterification degree, the amount of galacturonic acid, and the emulsifying activity of the pectins extracted were 2.20- 17.16%, 20.20- 36.13%, 51.3- 74.7%, and 1.87- 21.64%, respectively. With increasing microwave power, irradiation time and decrease of solution pH the extraction efficiency of pectin extracted increased, while esterification degree decreased. The amount of galacturonic acid and emulsifying activity showed an upward trend up to microwave power of 450 watts and the irradiation time of 3 minutes after which demonstrated a downward trend. The optimum conditions for reach to the maximum extraction yield, galacturonic acid content and emulsifying activity were in microwave power of 360 W, irradiation time of 4 min and pH of 1 that at these conditions, the extraction yield of 16.17, galacturonic acid content of 70.81 and emulsifying activity of 2.68 were predicted. Also, these observations indicated that with increase in concentration, the flow behavior of pectin solutions was changed from Newtonian to pseudo-plastic. In addition the stability of pectin-stabilized emulsion at 4°C was more than 23°C. In general, this study showed that the microwave method could be used as a novel and high-performance method for extracting pectin from eggplant peel.
Feresshteh Gholami; Sara Ansari
Abstract
Introduction: Roasting is an essential process that improves the taste, color, texture and appearance of the product. The shelf-life is also extended as a result of roasting. The temperature and the duration of roasting are the most important factors that influence favorable traits. IR is a novel technique ...
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Introduction: Roasting is an essential process that improves the taste, color, texture and appearance of the product. The shelf-life is also extended as a result of roasting. The temperature and the duration of roasting are the most important factors that influence favorable traits. IR is a novel technique for roasting that, compared to conventional heating, has positive advantages such as shorten heating time, significant energy saving and uniform heating. This study aimed to investigate the effect of IR, compared to conventional, roasting on some physicochemical and quality properties of soybeans. Moreover, the conditions of roasting soybeans via the two mentioned methods were optimized using Response Surface Methodology (RSM).
Material and methods: Soybean seeds were collected from a commercial farm in Gorgan (North of Iran) and were dried in an oven at 40 °C for 48 hours until the moisture content became lower than 5 % w/w. For each treatment, 25 g of raw soybeans were spread in glass petri dishes and were then roasted under the conditions selected for each experiment. In conventional roasting an electrical oven with the temperature range of 180 to 260 °C and time duration of 5 to15 min was used. IR roasting was performed using an IR-warm air apparatus with a constant power of 1300 W at the air temperature of 180-240 °C for 5-15 min. After the temperature equilibrium was reached, the samples were packed in polyethylene bags and were kept at 4 °C until further analysis. For each roasting method, a central composite design consisted of two variables of time and temperature (each in three levels) and a total of 13 experiments were applied. Response surface analysis was performed using Design-Expert software. The moisture content of samples was determined by drying the samples in a drying oven at 105 °C until a constant weight was reached. The total phenol content was measured quantitatively by the Folin-Ciocalteu colorimetric method based on the reaction of reagents with the active hydroxyl groups of phenolic compounds. The radical scavenging activity of the samples was determined by the DPPH radical. The force needed to break the roasted seeds was evaluated using a texture analyzer equipped with a load cell of 25 Kg. The color of samples was evaluated in a special box under controlled conditions (in terms of light intensity and camera position) using a digital camera and the color parameters (L*, a* and b*) and the color change (ΔE) were determined.
Results and Discussion: According to the results, the second- and first-order models were suggested for the study of time and temperature effects on moisture reduction that were both significant (p<0.05). In two methods, total phenolic content and antioxidant activity models were significantly (p<0.05) second-order. With increasing time and temperature, these above values increased. Hardness and color differences of oven roasting were both first-order but only color differences were first-order for infrared roasting. Effects of two parameters were significant in all models. Optimum conditions for soybeans roasting sing oven and infrared were 223°C – 13 min and 231°C – 11 min, respectively. In optimum condition, experimental data for the moisture content, total phenolic content, antioxidant activity, hardness and color differences were: (1.10, 4.53, 42.75, 9.03, and 4.93) , (1.58, 4.93, 47.85, 6.20, and 4.79) respectively. Based on above results, infrared can be introduced as a replacement of conventional oven method for the roasting of soybeans.
