ناصر همدمی

Freezing and thawing are complex heat transfer processes and the chemical and physical changes that occur during these processes can affect the product quality (Li and Sun, 2002). During the thawing process, physicochemical changes and microorganism activities damage the food products (Bertola et al, 1994; Kalichevsky, Knorr, & Lillford, 1995). Several factors can affect the degree of quality loss, including the rate of thawing, temperature, and microorganisms (Jia et al, 2017). The rate and quality of the thawing process are the fundamental needs of the meat industry, and accordingly, many studies have investigated the thawing conditions to achieve the best quality of meat products (Jia et al, 2017). Modern thawing methods such as high pressure, microwave, ohmic, radiofrequency, ultrasonic, and high voltage electric field thawing can improve the thawing rate at the low temperature (Hsieh et al., 2010). In recent years, the use of high voltage electric fields (HVEF) has been considered due to low thermal damage, no chemical consumption, and being economical. In HVEF thawing, a strong electric field is used between point and plate electrodes in an environment of dielectric fluid to create a force, followed by a secondary motion in the fluid. The secondary flow of fluid name ionic wind, or corona wind, results from localized air ionization around the point electrode. By increasing the corona flow, the volume fluctuation and air velocity increase, which results in an increase in the heat transfer coefficient (Singh et al., 2012). In this case, the thin electrode is an electric discharge electrode and another electrode is a ground electrode. One of the advantages of using an electric field for thawing is the antimicrobial effect of this method. In addition, the electric field can affect oxygen molecules of air and generates free radicals of ozone molecules, which is a strong oxidizing agent with a high disinfection capacity that various studies reported the effect of ozone depletion on poultry meat (Yang and Chen, 1979; Jaksch et al., 2004). The present study was conducted to study the effect of HVEF thawing of mutton on the process rate and its qualitative and microbial properties. For this purpose, three different strengths of the electric fields were produced by varying the voltage at a constant electrode distance, and the HVEF thawing was compared with the conventional air thawing.

The fresh mutton meat was cut into cube pieces (4 × 4 × 3 cm3, 35 g) and after packing in polyethylene bags were frozen by a freezing tunnel at -30° C for 1 hour and stored at -18 ° C until analysis. The HVEF system was consists of a generator with adjustable voltages between -50 and 50 kV and a maximum output current of 5 mA (Ls50KV5mA, China), multiple needle and plate electrodes, and a wooden enclosure. The copper plate electrode was connected to the negative pole and the spot electrode connected to the positive pole of the high voltage power. The thawing process was performed at an electrode distance of 4.5 cm and 3 different voltages of 7.6, 9, and 10.3 kV at a temperature of 25 ˚C. The thawing process proceeded until the center of samples reached 0˚C and an optical fiber thermocouple (FOB 651A, Canada) was used to determine the end time of thawing. The evaporation, thawing, cooking and total losses were measured by weighting the frozen samples before and after thawing and cooking (Mousakhani- Ganjeh et al., 2015). The surface color, pH value and total microbial count of meat samples were measured after thawing.

Thawing of frozen mutton was carried out at 3 voltages of 7.6, 9, and 10.35 kV, and at an electrode distance of 4.5 cm that is equal to the field strength of 1.7, 2.0, and 2.3 kV/cm. Thawing of the control sample was performed at the same condition without field application. Results showed that the thawing rate of the frozen samples significantly increased with increasing field strength so that the thawing time at the near-spark voltage in comparison with the control sample reduced 45%. Investigation of different losses of mutton samples thawed under different strengths of the electric field showed that the evaporation loss of the thawed samples under HVEF increased by arise the electric field strength, conversely, the thawing loss was reduced with increasing the electric field strength. The control sample had the lowest cooking loss and the thawed sample under the strength of 2.0 kV/cm had the highest cooking loss. As the results show, the pH value increased with increasing the strength of the electric field, but this increase was not statistically significant (p>0.05). Investigation of the color parameters of thawed samples showed a* index, as a particular index in the meat color, decreased and L* index increased with increasing the electric field strength. The results of microbial counts of thawed samples under different strengths of the electric field showed a significant decrease (P <0.05) in the total viable counts in thawed samples under HVEF compared to the control sample. Total microbial count of HVEF thawed samples under strengths of 1.7, 2.0, and 2.3 kV/cm decreased to 4.8, 4.69, and 4.5 log CFU/g, respectively.

This study investigated the HVEF thawing of frozen mutton in comparison with air thawing. The results showed that the HVEF thawing of frozen mutton improved the thawing rate and the evaporation, cooking and total loss of the conventional thawed sample was lower than the HVEF thawed samples while the thawing loss decreased by applying the electric field during the thawing process. In addition, HVEF thawing process reduced the total microbial count of thawed samples by the production of ozone and negative ions that this effect improved with increasing the electric field strength.

Several methods have been used to decrease losses during storage of fruits and vegetables. Of these methods, high-voltage electric field seems promising. The objective of this study was to investigate effects of high-voltage electric field on four major quality attributes of pomegranate fruit (Punica granatum L.) during storage.

Pomegranate fruits were exposed to high-voltage electric fields with strengths of 2 and 4 kV cm-1 at two various modes (use of high-voltage electric field alone at Day 1 of storage or repeat the high-voltage electric field treatment with the regular intervals during storage). Quality characteristics of the fruits such as color, texture, antioxidant content and respiration rate were assessed at 15-d intervals for 60 d.

Results showed that the respiration rate of pomegranate fruits decreased with storage time extension and high-voltage electric field treated pomegranates demonstrated significantly lower respiration rates, compared to the control. The lightness value (L*) of pomegranates treated under electric field was higher than that of the control sample
(p < 0.05) and the force needed to compress the pomegranate seeds treated under the electric field during storage was more than those of the control and samples treated with electric field alone on Day 1 of storage. Results also showed that use of electric field could increase the antioxidant activity of pomegranate fruits during storage.

It can be concluded that exposure to high-voltage electric field could induce or stimulate production of reactive oxygen species inhibitory enzymes in pomegranate defense systems. In addition, this study verified efficacy of high-voltage electric field treatment in postharvest preservation of pomegranate.

One of the common defects in the processing of Feta cheese made in package is softening of texture. This defect occurs mainly at low temperatures and salt levels. In the industry, by increasing the amount of syneresis from the curd, some of this defect is prevented.In addition to texture softening, quantity and quality of UF –Feta cheese affected by expulsion or absorption phenomena. Reducing or increasing moisture content of cheeses matrix effected on other compositions and physical properties of cheeses protein matrix. The most important factors that play role on syneresis and textural properties are temperature, NaCl concentration and calcium level. The mechanism of this factors is different, but in summary, any factor that increase protein aggregation in cheeses matrix, grain hardness and syneresis, and in contrast, expanding cheese matrix occur.

In this research, hardness and syneresis or absorption amount measured in six brine concentration consist 0, 2, 8, 10, 18 and 26 in 3 (200, 1700 and 3200 ppm) calcium ions levels (18 treatments) at 3, 11, 9 and 27°C (72 treatments). The 3 replicates were analyzed in triplicate. Data were analyzed using a split-plot design.

Temperature, brine composition (NaCl and calcium ions) and interaction between this factors (Salt× Ca++, T× Salt and T× Ca++) and Salt× Ca++×T, was significant effects (p<0.01) on hardness and syneresis. The absorption phenomena occur in a salt concentration and temperature less than about 8% and 11°C, respectively. At more than 8% NaCl and 11°C, gradually, hardness and syneresis improved. The most swelling was observed in range 8-10% salt. Increasing of Ca++ was shifted maximum absorption to lower brine concentration. When Ca++ ions increased, the maximum swelling was shifted to lower brine concentration. Also, the hardness results and moisture content of cheese confirmed shrinkage and swelling of the cheese matrix.

The interaction of temperature, Nacl and calcium have two different models on syneresis and textural properties in UF-Feta cheese. At below 11°C, when Nacl concentration enhanced up to 8-10%, softening and swelling cheese matrix increased, but Increasing Nacl concentration and temperature above this rang improve shrinkage and hardness cheese matrix. Also, grain in calcium ion concentration reduced swelling and softening in UF- feta cheese at all temperature and Nacl concentrations. Therefore, in order to avoid the softness of the texture of this type of cheese, the process of industrial production and storage should be designed in such a way as to prevent optimal swelling of cheese matrix.

In the past decade, sulfated fucose-rich polysaccharides (fucoidan) have been much interested due to their diverse biological activities, including anticoagulant, antiviral, antitumor, anti-inflammatory, anti-blood lipid, antioxidant, gastric protection and therapeutic activities. In the present study, microwave was used as a green efficient technology for the extraction of bioactive compounds of fucoidan from Iranian macroalgae (Nizimuddinia zanardini). In addition, effects of microwave on chemical composition and antioxidant activity of fucoidan were assessed.

Fucoidan polysaccharides were extracted under optimized conditions of microwave power, processing time and temperature. The compound characteristics, including extraction efficiency, fucose content, sulfate content, uronic acid content and DPPH radical scavenging were assessed. Fourier-transform infrared spectroscopy was used at wavelengths of 400–4000 cm-1 at room temperature.

Results showed that microwave treatment was effective in improving the extraction yield of fucoidan. Fucoidan extraction yields under the microwave technique included 3.71 and 2.35%. The fucose content under the microwave technique (33.17%) was compared to that under the conventional technique (29.5%) with significant increases, indicating less thermal degradation of the polysaccharide structures under the microwave technique. The microwave improved fucoidan antioxidant activity by producing shorter chain polysaccharides.

In this study, fucoidan sulfated polysaccharides were extracted using microwave extraction technique in a much shorter time than the conventional extraction technique with higher efficiency and lower thermal degradation. In addition, the shorter process time decreased solvent use.

Macroalgae are source of many polysaccharides. Based on their pigments content they are divided into brown, green and red algae having specific polysaccharide contents. Among them, brown algae (Phaeophyceae) are source of alginates and/or fucans or fucoidans (Percival and McDowell 1990, Torres et al., 2007). Alginates are anionic polysaccharide that existences in mixer of salt forms (Na+, Mg2+ and Ca2+) in cell walls of brown algae makes the tissues flexible and strong. They consist of (1,4) linked β-d-mannuronic acid (M) with 4C1 ring conformation and a-l-guluronic acid (G) with 1C4 ring conformation, the two uronic acids being in pyranosic conformation(Pawar and Edgar 2012, De Sousa et al., 2007). They offer three varying sequences identified as the blocks MG consisting of nearly equal proportion of both monomers with a high number of MG (or GM) dimmers, the blocks GG and the blocks MM (Haug and Larsen 1962). M/G ratio, length and distribution of sequences depend on the algae species but also on their growth conditions and geographic origins. It also determines the chemical and physical properties of alginates (Karaki et al., 2013). Indeed, their gelling properties are dependent on guluronic acid content and explained by the structural features of GG blocks where selective alkaline earth metal multivalent cations and notably Ca2+ take place by chelation. This phenomenon is known and explained as the “egg-box” model. The formed gel is not soluble in water. However, sodium alginate is a water-soluble polymer having generally pseudo plastic properties in solution (Draget and Taylor 2011). Polysaccharides have wide range of pharmacological activities and some of them are considered as antitumor, antihypertensive, immunomodulator as well as antioxidant agents. Their radical scavenger’s role can be used to inhibit oxidative damage in foods and improve their nutritional quality (Venugopal 2011, Yang et al., 2011).

Twenty-five gram of dried algae (Nizamuddinia zanardinii) was soaked under steering at room temperature for 24 h in 800 mL of 2% (v/v) formaldehyde to remove phenolic compounds and pigments. After that, the insoluble fraction was washed 3 times with MilliQ water and supplemented by 800 mL of 0.2 M HCL before to be incubated at different levels(25-60°C) for different extraction time periods(0.5-3 h) under stirring (250 rpm).After optimizing of acidic step, the suspension was then centrifuged (10000 g for 20 min at 20°C) and pellets with alginic acid were washed 3 times with MilliQ water before to be socked in a range from (2-4 % (w/v)) Na2CO3 solution for different levels (2-4 h) at different extraction time periods (60-90 °C). The mixture was centrifuged (10000 g for 30 min at 20°C) and the supernatant was precipitated with 3 volumes of ethanol 96 % (v/v). Pellets containing sodium alginate were dissolved in MilliQ water and precipitated with ethanol as described above. This step was repeated two times before to collect and freeze dried the sodium alginate. Response surface methodology (RSM) was used to study the effect of extraction temperature; X1 extraction time; X2 for acidic step and concentration; X1 , extraction time; X2,; extraction temperature X3 for alkaline step. A D-optimal design was employed for designing experimental data using Design-Expert 10.0.3 trial software (Stat-Ease Inc., Minneapolis, MN, USA).

Both temperature and time factors have a significant effect on the extraction efficiency and the effect of temperature on extraction efficiency is higher than the effect of time in acidic step. There is also a significant interaction between the two variables of temperature and time. The extraction temperature had an increasing effect on alginate extraction efficiency. Chloridric acid disrupts the cell wall and releases alginate and also converts alginate salts in the cell wall into arginic acid. Increasing temperature causes further cellular breakdown and alginate extraction efficiency increases. With increasing time, the extraction efficiency increased. This increase can be due to the fact that the acid needs time to penetrate the cell wall, and as the time increases, the permeability increases, resulting in the extraction efficiency, so that the permeability is complete and the highest efficiency is obtained and After that, the extraction efficiency remains constant and even due to the long-lasting effect of acid, it causes de-polymerization and decreases the extraction efficiency. Increasing temperature increased the effect of time factor, meaning that the interaction of temperature and time had a significant effect on extraction efficiency. At low temperatures, the effect of time on the extraction efficiency is low because of the breakdown of the cell wall, but at higher temperatures, which contribute to the thermal breakdown of the cell wall, the effect of time variation is more evident. In alkaline step the effect of concentration on extraction efficiency was considered as a quadratic equation and as interaction with extraction time. By increasing the concentration of sodium carbonate, the extraction efficiency increases with an ascending slope. In other words, the amount of efficiency increases with an increase in direct concentration. Sodium carbonate causes the sodium substitution in carboxylic acid arginine groups and sodium alginate salts are obtained. Therefore, increasing concentration results in more calcium ion replacement and alginate extraction efficiency increases. This increase in extraction efficiency is increased to the extent that all carboxylic groups are replaced by sodium ion, and after that the extraction efficiency remains constant, and even due to the high concentration and de-polymerization of the alginate, it reduces the extraction efficiency. With increasing time of extraction with sodium carbonate, the extraction efficiency decreases with a second order gradient. Sodium ion has been completely replaced in argonic acid groups during the initial extraction hours, and if the extraction time is increased due to the prolonged contact, sodium alginate is obtained with an excess of sodium carbonate which has an alkaline pH and because of the adverse effect of this pH Extraction efficiency is reduced. The effect of temperature on extraction efficiency was considered as a first-order equation and as interaction with extraction time. As the temperature rises due to breaking of the bonds that may lead to the separation of sodium ions and also cause de-polymerization of the alginate, the extraction efficiency decreases.

Chloridric acid disrupts the cell wall and releases alginate and also converts alginate salts in the cell wall into alginic acid. the acid needs time to penetrate the cell wall. The results showed that in acidic step temperature and time are two major effective factors on yield and quality of extracted alginate. Sodium carbonate causes the sodium substitution in carboxylic acid arginine groups and sodium alginate salts are obtained. Sodium ion has been completely replaced in argonic acid groups during the initial extraction hours, in high temperature may lead to the separation of sodium ions and also cause de-polymerization of the alginate so in alkaline step, all factors have effect on yield, polyphenol and apparent viscosity of extracted polymer. The optimized conditions of extraction of sodium alginate from brown algae (Nizimuddinia zanardini)were as follows: temperature: 60 oC, time: 3 h (acidic step) and temperature: 60 oC, time: 3 h and concentration 3 % w/v (alkaline step).

Freezing under statically electric fields is one of the novel freezing methods to improve the quality of frozen products by controlling the nucleation process. The objective of this study was to investigate effects of freezing under electrostatic fields on the freezing parameters and microstructures of frozen button mushrooms.

Mushroom samples were frozen at -30 °C under electrostatic fields with voltages of 0.0, 4.5, 9.0 and 13.5 kV. Temperature of the sample center was recorded during freezing. Furthermore, microstructure of the mushrooms was analyzed using light microscopy.

Assessment of the freezing parameters has shown that use of electric fields during freezing increases the nucleation temperature and phase transition time. Increased electric field voltage up to 4.5 or 9.0 kV increased the nucleation temperature, while the nucleation temperature decreased again with further increases in voltage. Furthermore, use of electric field decreased damages to mushroom microstructures during freezing and the smallest ice crystals were formed at voltages of 4.5 and 9.0 kV.

In conclusion, freezing under electric field increases the nucleation temperature and decreases the ice crystal size; therefore, improves the microstructure of button mushrooms. Voltage increase has shown an optimum value for the increase of nucleation temperature and preserve of mushroom microstructure.

In high voltage electrostatic field technique, by applying a high voltage electric field (HVEF) in a needle- plate electrode system, air at the surface of food product is ionized, and a volumetric flow known as corona wind is formed, that increases the heat transfer coefficient in food product by volumetric heat generation. In this thechnology, ozone generation followed by the corona discharge and air ionization, are capable to reducing microbial contamination; on the other hand, since ozone is a strong oxidizer, there is a risk of lipid oxidation. The aim of this paper is using high voltage electrostatic field for thawing of chicken breast, and investigating its effects on microbial count and lipid oxidation. First, fresh chicken breast were cut into equal cubes (2×2×2 cm3) by a designed cast and sharp razor, then, were frozen by a freezing tunnel with forced air circulation at -30 0C and 1 m/s air velocity, after vacuum packaging in polyethylene bags. The frozen samples were kept at -180C until use. Thawing under HVEF at three different voltages (from the corona start voltage to the breakdown voltage), and specific electrode gaps were done. The control sample was subjected to no HVEF but thawed conventionally by still air method. Fat oxidation of thawed samples were investigated at first, third, fifth, and seventh days intervals during storage at refrigerator. The thawed samples were kept at refrigerator (4±10C) after packaging, and evaluated for microbiological tests (total microbial count and psychrotrophic), and the oxidation kinetics were investigated. Total microbial count during first, third and sixth days of storage at refrigerator, by pour plate at 300C for 72 hours, and psychrotrophic bacteria count during ten days storage at 6.50C by surface plate were investigated. The equation resulted from TBARS- time changes curve, is linear. By evaluation of zero-order kinetic model, the kinetic rate constant was determined at different treatments. The kinetic rate constant had no significant difference with control at low electric field strength (1.5 kV/cm); while, this factor was more intense with increasing electric field strength (2.25 and 3 kV/cm). Generally, malonaldahyde formation rate of thawed chicken was increased by increasing voltage and decreasing electrode gap during storage. However, at corona start voltages, malonaldahyde formation rate constant was less than control. Results from microbial growth showed total microbial count decreased at HVEF thawed samples compared with control and fresh chicken during six days storage. Total microbial count in the case of control was 1.07×105 cfu/g at first day, that was increased to 7.82 ×106 cfu/g at sixth day, and in the case of HVEF thawed samples at 8 and 10 kV, were 5× 104 cfu/g and 3.36×104 cfu/g at first day, that were increased to 1.36×106 cfu/g and 1×106 cfu/g at sixth day, respectively. However, total microbial count of fresh chicken was increased from 9.73×104 cfu/g at first day to 6×106 cfu/g at sixth day. On the other hand, storage at 6.5 0C during 10 days, decreased the psychrotrophic microorganisms significantly at HVEF thawed samples) P<0.05). Due to the importance of thawing for products susceptible to spoilage, such as chicken, it is possible to benefit from HVEF thawing method to decreasing spoilage and increasing shelf life, by applying 2.25 kV/cm electric field strength.

Bamiye is kind of sweet that frying is one of the stages of making it. The purpose of this study was to evaluate the effect of pre drying on some quality features of Bamiye. Samples put in oven at 105 ° C for zero (control), 2.5, 5 and 7.5 minutes for drying, then they fried on frying oil at 160 ° C and were measured qualitative characteristics on production day and every 15 days for 1 month at during storage. The Acid and Peroxide values in the pre dried samples showed a significant decrease compared to the control samples. the lowest content were for 7.5 minutes pre dried samples and maximum amount of it were for control samples. During storage Acid and Peroxide values increased in all of samples, but this increase in control samples was more than pre dried samples. By applying pre-drying treatment, volume of Bamiye decreased but tenderness of them increased. During storage time of samples, volume, tenderness and sensory properties decreased. In this case, reduce the volume and tenderness of the treated samples was less than the control sample. The results showed, pre drying is a suitable method for production of Bamiye samples and it has advantages such as saving product time, preparation Bamiye with low calorie, healthy oils and products with a high shelf-life. Advantages such as reducing process time, producing healthy product with lower calorie (due to low oil absorption) and longer lifetime.

With regard to possibility of the acrylamide carcinogenicity, increasing expansion of fried potato products industry and high consumption of these products in the country, the study and modeling of phenomena involved in the process of these products are seems necessary. The aim of this study was to investigate the kinetics of decreasing of reducing sugars, acrylamide formation and color changes during frying of potato strips. The results showed that decreasing of reducing sugars and acrylamide formation are occurring with the exponential patterns during frying and increasing temperature and time of frying are intensifies these phenomena significantly (P

Heat treatment of potato tissue involves chemical, physical and structural changes. The magnitude of these changes will depend on the extent of thermal processing in terms of time and temperature. Blanching is a heating process that used to inactivate enzymes, de-aeration and modification of texture, preserving color, flavor and nutritional value of fruits and vegetables prior to freezing, canning, drying and frying. Temperature and time of blanching is largely determined by the amount of reducing sugars and textural characteristics of the species. In the previous studies performed on the changes of reducing sugars content in potatoes during blanching, some researchers found evidence that besides the mass transfer to the bath there exists an internal generation of reducing sugars, probably due to an enzymatic hydrolysis of starch. Therefore when predicting the concentration of reducing sugars changes, both mechanisms should be considered. Considering that no study has been done on the effect of internal generation of reducing sugars on their effective diffusivity during blanching and so far there is no comprehensive study on the kinetic of texture changes during blanching of potato at different temperatures and also direct relationship of reducing sugars with Maillard reaction and acrylamide formation in potato, therefore the aims of this study are: 1) determination of effective diffusivity of reducing sugars with and without consideration of them generation and 2) investigation of kinetic of texture changes during blanching of potato strips at the temperature range of 50-90 ºC and modeling of these phenomena.
Potatoes (variety Agria, ~23 g/100g (dry basis)) was the raw material used in this study. Potatoes stored in a dark room at 20 ºC for 2 weeks were washed and peeled. Then, were striped into dimensions of 0.8×0.8×8 cm using an electric striping machine (Halldeh, model RG-100). Raw potato strips were rinsed immediately after cutting for 1 min in distilled water to eliminate the starch material adhering to the surface prior to blanching. Then, blanching was accomplished by immersing the potato strips in hot distilled water (ratio of mass of potato to water of 1:20) at 50, 60, 70, 80 and 90 ºC. To investigate the kinetic of generation of reducing sugars, strips packaged in duplex in the polyethylene (HDPE with 10 micron thickness) film were immersed in hot distilled water to blanching at the temperatures. Samples were withdrawn after 5, 10, 15, 20, 40, 60, 80, 100 and 120 minutes to measure the reducing sugars content and texture firmness. All experiments were done in triplicate. Maximum stress caused by penetrating of the probe (diameter of 2 mm) into strip texture was the texture evaluation index. To describe the mass transfer (extraction of reducing sugar) during blanching, a three dimensional numerical model based on finite difference method of solving Fick's Second Law has been developed in MATLAB software. The first order kinetic with production rate limiting effect was used to describe the potato strips texture changes during blanching. All experiments were done in triplicate as factorial based on completely randomized design. Data analysis and plotting of figures were performed in SAS and Excel software respectively.
The results showed that increasing of blanching temperature increase the reducing sugars effective diffusion coefficient significantly (P

Freezing is one of the important refrigeration processes widely applied in food preservation, but textural defects can occur during process depending on freezing rate. These phenomena usually occur during freezing but become visible in the shape of crust cracking and flaking after final frying. This paper represents the effect of freezing and final frying conditions on some physical properties of chicken nugget. Three freezing temperatures (-20, -30 and -40°C) was used in this study. A texture analyzer by compression and penetration tests were used to assess the rigidity of sample after freezing and final frying respectively. Video capturing method was used during compression test for acquiring poison ratio; also, crust cracking and flaking of chicken nugget after freezing and final deep fat frying were evaluated by image analysis. The results showed that reduction in freezing temperature causes an increase in Young’s modulus especially at around of freezing point. But poison ratio decreased gradually by temperature reduction with the greatest change at freezing point. After final frying Young modulus of crust increased significantly (P

Increasing freezing rate can have an effective role in improving the quality of frozen products. The objectives of this study were to compare ice crystal morphology of frozen lamb meat under different freezing temperatures (-20, -30 and -40 oC) and their effect on the quality attributes of the lamb meat. After freezing in different freezing temperatures, the meat samples were thawed and their quality characteristics such as drip loss, texture, and colour were assessed by instrumental methods. Light microscopy technique was used to investigate the effect of freezing process on the lamb meat microstructure. Results showed that freezing temperature led to the significant microstructural changes in meat tissues. The equivalent diameter of the ice crystals formed were 22.58, 19.36 and 17.48 μm for the samples subjected to processes -20, -30 and -40 oC respectively and total relative ice area for temperatures above were determined 52.32, 49.84 and 46.36% respectively. It was also found that the drip loss decreased with decreasing the freezing temperature but freezing temperatures didn’t show any significant effect on colour, texture (stiffness) and shape of ice crystals.

In this study, the aqueous melanoidin solution (as a model for the colorant present during thick beet juice processing) were decolorizied by powdered activated carbon. A Response Surface Methodology (RSM) was applied to optimize the operating variables of the decolorization process. The results revealed that the optimal values of the process parameters for concentration of melanoidins equal to 750.0 mgL-1 were as follow: pH of 7 and reaction time of 30 min. Under these optimal conditions, the color removal performance was achieved 73.07% and 93.0% for aqueous melanoidin solution and sugar beet syrup, respectively with the addition of 0.1 g of powdered activated carbon. Chemical specifications of synthetic melanoidins and activated carbon, before and after adsorption process were determined using Fourier transform infrared. Decolorization kinetic parameters indicated that the adsorption of melanoidins was followed from pseudo-first order equation. Furthermore, adsorption isotherm studies indicated that melanoidins adsorption was correlated reasonably well by Langmuir isotherm model. In following, molecular size distribution of melanoidins was studied in order to get a better understanding of the evolution distribution molecular weight of melanoidins during decolorization processes. Analysis confirmed the presence of melanoidins with molecular weight distribution between 0.7 kDa to 4000.0 kDa. The colorants with a molecular mass of 4000.0 kDa were completely removed whereas components above 230.0 kDa, 7.0 kDa and 0.7 kDa presented lower removal efficiencies, showing lower affinity on powdered carbon during decolorization process. The results of this study indicated that powdered activated carbon has a good potential for removal of the high molecular weight colored impurities in thick beet juice.

The effect of blanching, pre-drying and frying conditions on quality of fried potato strip was investigated. For this purpose, strips with a cross-section of 0.8×0.8×8 cm were prepared and immersed fried in hot oil after performing of each pre-treatment. Pre-treatments were included: 1) blank strips (raw potato), 2) blanched strips in hot water at 70℃ for 10 minutes, 3) pre-dried strips at 70℃ with air velocity of 1 𝑚⁄𝑠 until mean moisture content of 75% (wet basis) and 4) blanch and pre-dried strips and frying was carried out in three treatments of: 1) at 160℃ for 5 min, 2) at 175℃ for 4 min and 3) at 190℃ for 3 min. The results of investigates showed that the minimum of oil content was related to blanch and pre-dried strips in all frying treatments. Blanched strips also had the lowest reducing sugar content and therefore the lowest acrylamide content. Blanching and pre-drying treatment were improved the colorimetric parameters significantly (P

In order to investigate the effect of temperature and time of blanching process on the generation and extraction of reducing sugars and kinetics of color changes during blanching, the potato strips packaged in the polyethylene (HDPE with 10 micron thickness) film or without polyethylene packaging, were immersed in distilled water at temperature range of 50, 60, 70, 80 and 90 ºC for 120 minutes. The results showed that increasing the temperature of blanching accelerated the diffusion of reducing sugars but the generation of these sugars is decreased with increasing temperature and stopped at 80 and 90 ºC. Increasing temperature and time of blanching were also reduced colorimetric parameters significantly (P

The use of nanofillers is a good strategy to improve the properties of biopolymer-basedpackaging films. The present study prepared zein-based nanocomposite film containingmontmorillonite using the solvent casting method. Mechanical, barrier, and thermal properties of the film were investigated. The x-ray diffraction patterns indicated that the composite film has an exfoliated structure.The results showed that the montmorillonite significantly improved the mechanical, barrier, and thermal properties of the zein film. The highest elongation (9.65%) and tensile strength (22.62 MPa) were obtained for the zein nanocoposites containing 0 and 10% montmorillonite, respectively. Increasing the montmorillonite content from 0% to 5% decreased the water vapor permeability of the zein film from 1.73 to 1.23 (28%). This parameter significantly increased (1.93) in film containing 10% montmorillonite. The thermal degradation temperature of zein film increased (from 353 to 373 °C) by increasing the montmorillonite content from 0% to 10%. The results revealed that a small amount of montmorillonite can improve the mechanical and barrier properties of zein film, although uniform dispersion ofmontmorillonite in the zein network is essential to improving the properties of the film.Keyword:

Cheese ripening is one of the most impotant stages during cheese production. After milk coagulation, in order to achieve the appropriate organoleptic properties, it should be exposure to the suitable environmental conditions. Proteolysis is the most substantial stage during cheese ripening. Several parameters are effected the proteolysis in cheese production process such as temperature, salt concentration, water activity and the amount of retentate coagulant enzymes in curd. The goal of present study was to investigate effect of temperature (4, 8, 12ºC) and salt concentration (8, 10, 12%) on kinetic of proteolysis during two monthes. Samples were exposed to physicochemical experiments each two weeks. In order to investigate kinetic reactions, the amounts of soluble nitrogen in pH= 4/6, non protein nitrogen, color intensity of α-casein and β-casein taint in Urea poly acryl-amide gel electrophoresis were measured. By increasing the temperature, degradiation of α-casein and β-casein and production of soluble nitrogen in pH= 4/6, and non protein nitrogen were intensified. Results are also showed that, rising the temperature in constant salt concentration, leads to increase the kinetic constant, whilst the calculated amounts of kinetic constant at 12ºC for all of parameters were the highest. By investigation of proteolysis kinetic in cheese and reciprocal effects of temperature and time, optimum ripening conditions were detrmined at 8 ºC and 10% salt concentration for 6 weeks to obtainig the product with suitable organoleptic properties and high quality.

Fresh bread has a short shelf life, and its acceptability by consumer would be dramatically reduced by increasing the time between baking and consumption. One of the solutions for this problem is frozen dough technology. Therefore, in this study, the impact of cold pre-treatment and pre-fermentation in Sangak frozen dough and its bread was evaluated. Dough samples (with 100% V/W water) were fermented for 10 min and 40 min and after pre cooling (until temperature of dough reaching 4 ˚C or holding 1 hour at 4 ˚C after reaching to this temperature) or without cooling, they were frozen under -25 ˚C in air blast freezer. After 24h storage at -18 °C, Sangak frozen dough and its bread quality were assessed by measuring yeast survival and gassing power after thawing, and by measuring density, texture and color variation after baking. Cooling dough before freezing had a positive effect on the viability of yeast and dough volume; it also improved the quality properties of bread prepared from it, such as density, texture and color (p< 0.05). In addition, pre-fermentation for 40 min improved the gassing power of dough significantly; however, it had no significant effect on its bread (p< 0.05). Use of pre-cold treatment improved frozen dough and its bread quality.

Rehydration typically composes of three simultaneous processes: the imbibition of water into dried material, the swelling of the rehydrated products and the leaching of soluble solids to rehydration medium. In this research, squash (Cucurbita pepo) fruits were cut into 0.4 cm thick and 4 cm diameter slices. Then, squash slices were blanched in a steam chamber for 4 min. After cooling to room temperature, squash slices were dehydrated up to moisture content of 0.1065 kg H2O per kg d.m. Dehydrated samples were stored at 4°C. Squash slices with specified weight were rehydrated by immersion in distilled water at different temperatures (25, 50, and 75°C), various dry matter-water ratios (1:25, 1:50, and 1:100), which was agitated at 100 rpm. At specified time intervals, up to 300 min, the squash samples were removed from the water, and the weight, moisture content and rehydration indices of the sample were determined. The texture characteristics were examined over a 180 min period. The results showed that moisture content, water absorption capacity (WAC) and rehydration ability (RA) of squash slices increased, whereas dry matter holding capacity (DHC) and texture firmness (maximum force and stress) decreased with rehydration time. The maximum WAC was achieved in squash slices rehydrated into 75°C water at 1:100 dry matter-water ratio. The lowest force and stress were observed in squash slices which were rehydrated into 75°C water after 180 minute. These squash slices had the maximum moisture content and RA and the minimum DHC. The lowest moisture content and RA and the highest DHC, force and stress, were observed in squash slices immersed in water at 1:100 dry matter-water ratio. In general, for all rehydration conditions of squash slices, the highest water absorption rate occurred during the first minuts of process. Then, this rate decreased. The highest rehydration rate and amount of water absorption occurred in 75°C.

Throughout the present research، squash (Cucurbita pepo) slices (0. 4 cm thickness and 4 cm diameter) were blanched in a steam chamber for 4 min. Following cooling to room temperature، the squash slices were dehydrated by use of a hotair dryer، under air temperature of 60°C up to moisture content of 0. 1065 kg H2O per kg d. m. Squash slices of specified weights were rehydrated by immersion in distilled water at different temperatures (25، 50، and 75°C). They were agitated at different speeds (0،100، and 200 rpm). For any of the experiments، the dry matter to water ratio was kept at 1:25. The squash samples were removed from water at specified time intervals of up to 300 min. Then their weight، dry matter content and water absorption content (in percent) were determined. The squash slice color was examined over a 180 min period. The results showed thatrehydration time، water temperatureand agitation speed had significant effects (p˂0. 01) on dry matter content، water absorption (percent) and color indices (L*، a*، b*، and ΔE) in the dried squash slices. Water absorption percent and total color difference (ΔE) of squash slices increased، whereas dry matter content and color indices (a*، b*، and L*) decreased with rehydration time. Maximum water absorption and ΔE، minimum dry matter content as well as color indices (a*، b*، and L*)، were observed in squash slices rehydrated into 75°C water and agitated at 200 rpm.

Flaxseed is one of the oilseeds that use as ingredient in food product due to its considerable nutritional and beneficial health effects. In this study in order to produce functional Taftoon bread, ground flaxseed was incubated at 30 ºc and microwaved for 2.5 minutes in order to reduce cyanogenic glycosides compound. Wheat flour replaced with treated ground flaxseed at 5, 15 and 25 percent levels. Results showed that cyanogenic compound reduced 84/6%. Result of rheological properties test of dough showed that, with replacing wheat flour with ground flaxseed, water absorption of dough and expansion of dough during fermentation decreased and stability time of dough increased and the difference between them was significant (p<0.01). Results of stress relaxation test showed that addition of ground flaxseed to wheat flour, increases the viscoelasticity of dough. Results of oxidative stability test showed that with replacing wheat flour with ground flaxseed, peroxide and thiobarbituric acid value increased and highest value was at 15% ground flaxseed and had significant difference(p<0.01). Results showed that bread containing flaxseed had darker color and softer texture and staling of bread containing flaxseed was lower. Results of organoleptic test showed that bread containing flaxseed had better flavor, aroma, texture and overall acceptability by panelist, although color of bread had less acceptance at 15% and 25% level of replacing ground flaxseeds.

Processes such as drying, sauce making, extracting and doping reduced nutritional value and unique sensory characteristics of pomegranate. On the other hand, the difficulty in peeling and removing the arils has limited its fresh consumption. For this reason, the “ready-to-eat” pomegranate may represent a possible option to implement fresh fruit consumption. In this study, the effects of modified atmosphere packaging on quality of pomegranate arils were evaluated. Low density polyethylene (LDPE, 100μm) used for packaging materials and stored for 11 and 9 days at 4 and 10C respectively. At storage period Headspace gas composition and quality parameters (acidity, pH, TSS, firmness and color) were measured. During storage, both Oxygen concentration in head space and acidity of arils reduced but carbon dioxide concentration increased. Temperature and weight of arils in package had a significant effect (p≤0.05) on gas composition. Total soluble solid, firmness al color of arils have no significant change during storage period. LDPE pouch and storage at 4 and 10C, provided reliable shelf life of 7 and 5 days, respectively. At higher temperature macro/micro perforations would be essential on the LDPE film in order to avoid critical levels of O2 and CO2.

Fresh bread has a short shelf life and by considering this matter, its acceptability by consumer dramatically would reduce by increasing the time between baking and consumption. Use of frozen dough technology is one of solution for this problem. Therefore in this current study the impact of freezing storage and pre-fermentation in Sangak frozen dough and its bread was considered. Dough was prepared in three form of non fermented, pre fermented and formed and pre fermented and non formed. Time of pre-fermentation for all samples was 30 min. Then dough wasfrozen under -25˚C in air blast freezer. After freezing, the dough pieces were stored at -18˚C for 24 hours, 4, 7, 10 and 13 weeks. Sangak frozen dough and its bread quality was assessed by measuring yeast survival and dough expansion after thawing and by measuring density and texture after baking. Results showed viability of yeast and dough expansion decreased by freezing and longer storage time. Also density and firmness of bread increased whit longer storage time. Pre-fermentation for 30 minute decreased quality of frozen dough and its bread Therefore, quality of frozen dough and its bread affected significantly by freezing of dough and its storage.

Due to problems in storage, transportation and price fluctuation of fresh potato, production of ready-to-use products like French fries is of particular importance. French fries quality mainly depends on the appearance, taste, color, texture and oil uptake. One of the important steps in product processing is blanching. This step improves product texture and color due to the decrease in reducing sugar content, and causes reduction of oil uptake due to the gelatinization of surface starch. Therefore, by selecting a suitable method and condition, the improvement of product quality is possible. In order to investigate the effect of blanching temperature on kinetic of the reducing sugar content and changes in potato stick color and texture, sticks with 0.8 0.8 8 cm dimensions were prepared and blanching was carried out with hot water at different temperatures (60, 70, 80 and 90°C) and various times up to 120 minutes. Color, texture and reducing sugar content of samples were measured during blanching. The results showed that reducing sugar content was reduced during the blanching as a function of temperature and time. Also, product color and texture were mainly affected by blanching temperature, with the low temperature being more suitable to improve potato stick quality. According to the results, there was no significant difference between blanching at 80, 90°C and 60°C for reducing sugar content. Also, for this parameter, there was no significant difference between times of 100 and 5 minutes at 60°C. The least texture damage was obtained by blanching at 60°C in a short time. It could be concluded that to preserve potato stick color and texture and reduce energy consumption, blanching can be done at 60°C for 5 minutes if enzymes are inactivated.