Food Engineering
Mohammad Reza Salahi; Seyed Mohammad Ali Razavi; Mohebbat Mohebbi
Abstract
Introduction: Emulsion-filled gel is a sort of gel system that traps oil droplets as a filler and contains a wide range of semi-solid to solid food products. They can also be utilized as a dual system to distribute and control the release of both lipophilic and hydrophilic bioactive and micronutrient ...
Read More
Introduction: Emulsion-filled gel is a sort of gel system that traps oil droplets as a filler and contains a wide range of semi-solid to solid food products. They can also be utilized as a dual system to distribute and control the release of both lipophilic and hydrophilic bioactive and micronutrient substances. The main polymers involved in gel formation in food products are proteins and polysaccharides. Using molecular interactions between biopolymers, a wide range of rheological and physicochemical properties of gels can be methodically created. As a result, the interaction between proteins and polysaccharides has received a lot of attention in order to generate novel products. Because of their functional qualities and high nutritional value, whey proteins are frequently used in the food industry. As a result, mixed gels based on whey protein have gained a lot of attention. k-Carrageenan is commonly utilized in the food industry as a gelling and firming agent. Because k-Carrageenan, like whey protein isolate, can form a gel independently, its interaction with whey protein isolate in emulsion gel systems appears appealing. Therefore, in this study, the effect of k-Carrageenan gum (0.0, 0.1, 0.3, 0.5, and 0.7%) on the textural (uniaxial compression test), rheological (steady shear, strain sweep, and frequency sweep tests), and water holding capacity of cold-set emulsion-filled gel based on whey protein isolate was investigated.Materials and Methods: Whey protein isolate (WPI) (98.9% protein, dry basis) was given as a gift by Agropur Ingredients Co. (Le Sueur, Minnesota, USA). k-Carrageenan and CaCl2 (m_w: 147.01 gr/mol) were purchased from Sigma Aldrich Co. (USA) and Merck Co. (Darmstadt, Germany), respectively. Sunflower oil was bought from a local supermarket. Stock dispersions of WPI and k-Carrageenan were made by dissolving sufficient amounts of their powders in deionized water. To prepare uniform oil in water emulsion, sunflower oil was added to the WPI dispersion and the obtained mixture homogenized first using a laboratory rotor-stator homogenizer (15000 rpm, 3 min), then by an ultrasonic homogenizer (20 kHz, 5 min). The prepared emulsion and k-Carrageenan dispersions were poured into Schott bottles and heated in a water bath (90 C, 40 min). WPI emulsion and AG dispersion were mixed in a cylindrical container on a stirring plate at a speed of 600 rpm for 6-8 min to obtain a homogeneous mixture. After decreasing the temperature to 60 C for the ion-induced gelation, the mixtures were charged with CaCl2 (10 mM). The prepared samples were incubated in a refrigerator overnight to stabilize the 3D network. The final mixed EFG samples contained 5.5% WPI, 20% oil, and 0, 0.1, 0.3, 0.5, and 0.7% (w/w) of k-carrageenan. The tests performed on emulsion-filled gel samples were: 1) steady shear (0.01-10 s-1), 2) strain sweep (strain: 0.1-1000%, frequency: 1 Hz), 3) frequency sweep (frequency: 0.1-100 Hz, strain: 0.5%), 4) uniaxial compression (target strain: 80%, deformation speed:1 mm/s), and 5) water holding capacity (by utilizing a microcentrifuge, 600×g for 10 min).Results and Discussion: According to the steady shear test, all samples had a shear thinning behavior, and based on the power-law model, this behavior was intensified in the presence of k-Carrageenan; and with increasing the gum concentration from 0 to 0.7%, the consistency coefficient increased from 339.9 to 545.7 Pa.s. In the strain sweep test, with the increase in the gum concentration, the values of the elastic and viscous modulus in the linear region and the modulus at the crossover point increased, and Tan LVE decreased from 0.17 to 0.13, which indicated an increase in the strength of the emulsion gel network structure. Based on the frequency sweep test, with the increase in k-Carrageenan concentration, the parameters K^' and K^'', network strength and network expansion, respectively, increased from 5311.8 Pa, 939.9 Pa, 1.5380 Pa.s1/z and 10.05 in the control sample to 25080 Pa, 3574.9 Pa, 16097.7 Pa.s1/z and 16.41 in the sample containing 0.7% k-Carrageenan, respectively. Moreover, the frequency dependency of elastic modulus decreased from 0.095 in the control sample to 0.050 in the 0.7% k-Carrageenan contained sample. According to the large deformation test, in general, in the composite emulsion-filled gels, the values of apparent modulus of elasticity and fracture stress were higher and fracture strain and fracture energy were lower than in the control sample. Also, the results showed that different k-Carrageenan concentrations had no significant effect on the water holding capacity.The obtained results showed that k-Carrageenan had considerable influence on the rheo-mechanical features of cold-set emulsion-filled gels based on whey protein which can add to the knowledge base for the production of new functional foods.
Food Engineering
Morteza Kashaninejad; Seyed Mohammad Ali Razavi; Mohammad Reza Salahi
Abstract
Introduction: One of the products that its production has not been investigated well and is an imported product is cream powder. Foam mat drying is a widespread technique to dehydrate liquid or semi-liquid foods with high viscosity, adhesion and high sugar content, which are usually difficult to dry. ...
Read More
Introduction: One of the products that its production has not been investigated well and is an imported product is cream powder. Foam mat drying is a widespread technique to dehydrate liquid or semi-liquid foods with high viscosity, adhesion and high sugar content, which are usually difficult to dry. Evaluating moisture content over time is the first indication of how the drying process is performed and can be used as a tool to compare the drying behavior of food. The rate of drying, which is expressed as a function of time or moisture content, is also a very important parameter that helps to understand drying properties of a material. Color can also indicate chemical changes in food during the thermal process such as browning and caramelization. Therefore, since in the drying industry, process time, product quality, optimization and equipment design are directly affected by the rate of drying of food, hence, in this study, in the process of drying the camel milk cream by the foam mat drying method, drying operation at temperatures of 45, 60 ,and 75 °C and thicknesses of 1, 3 and 5 mm was performed in a non-continuous cabinet dryer to evaluate the kinetics of drying , structure and color of the dried foam. Materials and Methods: Camel milk cream was mixed with carboxymethyl cellulose (0.1%), cress seed gum (0.1%) and 80% whey protein concentrate (5%) at 25 ° C. After pasteurization, the samples were stirred with a mixer at a maximum speed of 1500 rpm (5 minutes) for proper aeration. The foam samples were poured into a plate in a thin layer with thicknesses of 1, 3 and 5 mm and then dried in a dryer at temperatures of 45, 60 and 75 ° C until a constant moisture was reached. The process treatments were performed in a completely randomized central composite design (CCD) (5 replications at the center point) for 2 variables at three levels. The effective diffusion coefficient was calculated based on the second Fick's law of diffusion. Then, using Arrhenius equation, which shows the relationship between temperature and effective diffusion coefficient, activation energy was also calculated. After the drying stage, in order to investigate the changes in moisture during the drying, by determining MR, we have used some experimental models that were previously used for drying agricultural products, to fit the experimental data using the statistical software MATLAB 2016. Results and Discussion: The results showed that increasing the temperature from 45 to 75° C reduced the drying time of the samples by almost 50%. Reducing the thickness from 3 to 1 mm led to an 80% reduction in drying time of the samples. The overall effective diffusion coefficient of the tested samples varied between 7.09×10-10 and 8.11× 10-9 m2/s. The increase in the temperature led to an increase in the effective diffusion coefficient of the samples. The activation energy of the samples varied between 25.59 and 38.22 kJ /mol, and comparison of the means showed that the activation energy of the samples was also increased by increasing the foam thickness. Totally, 17 models were evaluated to investigate the drying kinetics of the samlses and in all cases of foam drying , page and Midilli models with R2 values above than 0.99 and the lowest values of RMSE indicate the best fit with the experimental data among the 17 fitted model. Examining the digital images of the samples also showed that at low temperatures, the structure of the dried foams was smooth and it became more uneven and porous as a result of increasing the temperature. Also, the trend of changes in the parameters of the gray level co-occurrence matrix (GLCM) (energy, correlation, and homogeneity) of the samples was almost the same with the changes in temperature and thickness so that, the increase in the drying temperature and a decrease in the thickness of the samples led to a decrease in these parameters. Increasing the foam thickness at high temperatures led to a decrease in the browning index and at low temperatures, led to an increase in the browning index of the samples.
Atefeh Pourmahdi; Mohebbat Mohebbi; Ashraf Gohari Ardabili; Mehdi Varidi; Mohammad Reza Salahi
Abstract
Introduction: Potato is one of the most consumed and highly nutritious vegetables with high energy, dietary fiber, phytochemicals, vitamins, and minerals which offer great benefit for utilization as functional food ingredient. The dried potato powder can be used in formulation of many foods like soups, ...
Read More
Introduction: Potato is one of the most consumed and highly nutritious vegetables with high energy, dietary fiber, phytochemicals, vitamins, and minerals which offer great benefit for utilization as functional food ingredient. The dried potato powder can be used in formulation of many foods like soups, snacks, sauces, noodles, etc. The foam mat drying involves the dehydration of a thin layer of foam followed by its disintegration in order to obtain a powder which can be easily reconstituted in water when added to other foods. Because of the porous structure of the foamed materials, mass transfer is enhanced leading to shorter drying times and consequently acquiring higher quality in the dried product. Food foams can be considered as biphasic systems where a gas (dispersed phase) is embedded in a continuous liquid phase. The foam properties such as structure, density and stability have important influence on moisture migration during drying and accordingly, the quality of final product. Foams that do not collapse for at least 1h are mechanically or thermally stable for the entire drying process. Response surface methodology (RSM) is a combination of mathematical and statistical techniques which used to investigate the interaction effects of independent variables on responses. There is considerable information on foam-mat dried food powders, but there is not any scientific literature that related to study on foam-mat drying of potato puree. The present research was thus focused on optimizing the foaming conditions (potato puree: gum solution ratio; Arabic gum (AG) concentration as the stabilizer and whipping time [WT]) to minimize foam density (FD) and drainage volume (DV) using RSM. Likewise, choosing a suitable model for thin-layer drying of foam and the effect of different drying temperatures (45, 60 and 80°C) on drying behavior were investigated, and the effective moisture diffusivity and activation energy were calculated. The effects of drying temperatures on water activity (aw) and water binding capacity (WBC) were also investigated.
Material and methods: Fresh potato was purchased from a local market (Mashhad, Iran). Arabic gum was procured from Sigma Chemical Company (USA). For preparation of potato puree, fresh potatoes were washed and peeled by steel knife and were washed again and additional water was taken absolutely and then crushed by Phillips home crusher (600W) with maximum speed for 3 minutes to get a homogeneous puree. Based on preliminary tests, AG solutions were prepared by dissolving a suitable amount of the selected gum powder in distilled water and stirring with a magnetic stirrer to obtain a uniform solution. This solution was refrigerated at 4°C overnight to complete hydration. RSM was used to estimate the main effects of the process variables on FD and DV in potato puree foam. The experiment was established based on a face-centered central composite design (FCCD). The experimental range was chosen on the basis of the results of preliminary tests. The independent variables were consisted of potato puree: gum solution ratio (1:1 –2:1 w/w), AG concentration (0.1–0.9% w/w) and WT (3–9 min). According to the experimental design, to prepare 100 g of samples, appropriate amount of potato puree and AG solution were mixed in a 250-mL beaker. The mixture was then whipped with a kitchen mixer (model no. SM88, Sonny, China) at a maximum speed of 1,500 rpm at ambient temperature during given time which was recommended by Design-Expert software. The density of foamed potato puree was determined in terms of mass over volume and expressed in g/cm3. In order to assess foam stability, the drainage test was performed for 1h. To evaluate drying behavior of the optimized foam, drying was carried out in a batch-type thin-layer dryer at temperatures of 45, 60 and 80°C on 3 mm thickness. Ten thin-layer drying models were evaluated in the kinetics research. The higher value of R2 and lower values of χ2, RMSE and SSE were selected as the basis for goodness of fit. Fick’s diffusion equation for particles with a slab geometry was used for calculation of effective moisture diffusivity. The foamed potato puree spread on a tray was considered as slab geometry. Activation energy was calculated by a simple Arrhenius-type relationship, by plotting the ln (Deff) against the reciprocal of absolute temperature (1/T). Furthermore, the effects of drying temperatures on aw and WBC of powders were investigated.
Results and discussions: The quadratic model was selected as a suitable statistic model for both FD and DV. ANOVA showed that this model is significant for both responses. Moreover, lack-of-fit was not significant for response surface models at 95% confidence level, indicating this model is adequately accurate for predicting responses. The optimum values of variables for best product quality in terms of minimum FD and DV corresponded to potato puree to gum solution ratio 2:1(w/w), AG 0.77% (w/w) and WT 6.80 min. The amount of FD and DV for foam at these optimum conditions were 0.30 g/cm3 and 5 ml, respectively.
The result showed that when the drying temperature increased, the drying time decreased. This was due to the quick removal of moisture at higher temperature. Drying rate (DR) versus moisture content of potato puree foam-mats figure showed that DR was higher during the initial stage as compared with the final stage and foam-mat drying was occurred principally in the constant rate period. Due to the increase in surface area and the porous structure, removal of water from the inner surface of potato puree foam to the outer surface was fast enough to preserve the surface moisture. The rate of movement of moisture from the inner surface to the exposed surface decreased with decreasing moisture content, which indicates that the DR decreased and the falling rate period started. The effective moisture diffusivity varied from 3.286×10-9 to 8.032×10-9 m2/s with activation energy value of 30.97 kJ/mol. Statistical analysis results showed that the Weibull distribution model provide the highest R2 and lowest values of χ2, RMSE and SSE at all drying temperatures. The temperature elevation reduced aw. This is due to the fact that at higher temperatures, the rate of heat transfer to the sample would increase, therefore, it provides greater driving force for moisture evaporation which results the dried foams with reduced aw. Drying temperatures did not show any significant effect on WBC of powders.
Farnaz Hassanzadeh Rad; Fakhri Shahidi; Mohebbat Mohebbi; Mohammad Reza Salahi
Abstract
Introduction: Kilka Fish is one of the most popular seafood products available for aquaculture development. It is a rich source of proteins, vitamins and minerals such as calcium and phosphor. The highly perishable nature of Kilka fish has strongly attracted researchers to find new methods to extend ...
Read More
Introduction: Kilka Fish is one of the most popular seafood products available for aquaculture development. It is a rich source of proteins, vitamins and minerals such as calcium and phosphor. The highly perishable nature of Kilka fish has strongly attracted researchers to find new methods to extend its shelf life. Kilka fish powder can be used in many foods, such as soups, sauces, snacks, etc. Foam-mat drying is a new effective technique has recently gained much attention because it does not suffer from major problems associated with traditional dehydration methods, such as poor rehydration characteristics, unfavorable sensory profile, and long drying time. The main objectives of this study were: (1) to optimize the effective parameters (egg white powder and xanthan gum concentration, and whipping time) on foaming properties of Kilka fish; (2) to study the effects of drying temperature and foam thickness on the drying characteristics and select a suitable model for thin-layer drying of foam; (3) to compute effective moisture diffusivity and activation energy of foam during drying; and (4) to study the effects of drying conditions on moisture content, water activity, hygroscopicity and color of powders and microstructure of dried Kilka fish foams.
Materials and method: Fresh Kilka fish (C. delicatula) was obtained from the Pak Samar Miroud Company (Mazandaran, Iran). Xanthan gum and egg white powders were purchased from Sigma Chemical Company and Gol Powder Company (Golestan Province, Iran) respectively. The Kilka fish skin removed and cleaned, and then crushed using a kitchen blender to obtain a homogeneous and uniform mixture. Based on preliminary tests, xanthan gum solution was prepared by dissolving a suitable amount of the selected gum powder in distilled water and mixed with a magnetic stirrer to obtain a uniform solution. The resulted solution was cooled at 4°C for 18–24h to complete hydration. According to the experimental design, to prepare 100 g of samples, appropriate amount of fish, egg white powder, xanthan gum solution and distilled water were mixed a 250-mL beaker. The mixture was then whipped with a mixer (Gosonic, model No. GHM- 818, 250W, China) with maximum speed at ambient temperature during given time, which was recommended by Design-Expert software version 6.02 (Stat-Ease, Inc., Minneapolis, MN). Foaming conditions, namely amount of egg white powder, xanthan gum and whipping time, optimized using response surface methodology (RSM) for minimizing foam density (FD) and drainage volume (DV). To evaluate drying behavior of the optimized foam, drying was carried out in a batch-type thin-layer dryer at three drying temperatures (45, 60 and 75°C) on 3- and 5-mm thicknesses. Ten thin-layer drying models were evaluated in the kinetics research. The higher values of R2 and lower values of χ2 and RMSE were selected as the basis for goodness of fit. The effective moisture diffusivity was calculated using method of slopes. A Fick’s diffusion model with slab geometry was used to describe the transport of moisture during drying inside a single Kilka fish foam mat. Activation energy was calculated by a simple Arrhenius-type relationship, by plotting the ln (Deff) against the reciprocal of absolute temperature (1/T). The microstructure of the dried fish foam-mats was analyzed by a scanning electron microscope. Finally, the effects of drying conditions on physicochemical properties of fish powder including moisture content, water activity, hygroscopicity and color were investigated.
Results and Discussion: The optimum values of variables for best product quality in terms of minimum FD and DV corresponded to egg white powder 3.67 % (w/w), xanthan gum 0.28% (w/w) and whipping time 8.93 min. The amount of FD and DV for foam at these optimum conditions were 0.92 g/cm3 and 0 ml, respectively. As expected, the increase in drying temperature and decrease in foam load led to acceleration of the dehydration of Kilka fish foam. Based on the statistical tests performed, Weibull distribution model can describe drying behavior of foams for all drying processes. Moreover, Fick’s second law was employed to calculate the effective moisture diffusivity that varied from 7.266×10-8 to 1.31×10-7 m2/s and from 7.404×10-8 to 1.693×10-7 m2/s with activation energy values of 18.201 and 25.615 kJ/mol for foam thicknesses of 3 and 5 mm, respectively. It was noted that the effective moisture diffusivity was increased when the drying temperature increased. Results showed that at the higher thickness, the internal moisture migration occurs along a longer distance rather than lower thickness. Therefore, an increase in moisture diffusivity occurs both with increase in drying temperature and sample thickness. The analysis of scanning electron microscopy (SEM) micrographs showed that there is wide porous structure of dried foams at higher speeds drying. With increasing drying temperature (due to reduction of drying times), combination of adjacent bubbles and therefor, collapse of foam structure occur less. Higher temperature reduced moisture content and aw , and thickness rise increased moisture content and aw under the same thickness and drying temperature, respectively. This is due to the fact that at higher temperatures, the rate of heat transfer to the sample would increase, therefore, it provides greater driving force for moisture evaporation which results the dried foams with reduced moisture content and aw. Moreover, with increasing foam thickness due to increased drying times and probably collapsed structure of foams and therefor weak pore structure, drying was performed difficultly which causes to retain more water in dried foams. Drying conditions had significant effect on hygroscopicity of powders. Results of color investigation showed that in both thicknesses, powder produced at 60°C have higher L* and lower a*.
