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 ...
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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 Technology
Dornoush Jafarpour; Parisa Ataei
Abstract
Introduction: Every year during marine fishing, some species that are caught are not suitable for human consumption and they are known as surplus fishing or low consumption, which is an important factor in wasting these rich resources. Therefore, it is necessary to set arrangements to use such species ...
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Introduction: Every year during marine fishing, some species that are caught are not suitable for human consumption and they are known as surplus fishing or low consumption, which is an important factor in wasting these rich resources. Therefore, it is necessary to set arrangements to use such species for human consumption, including the production of surimi. The surimi industry mainly uses Alaska pollock fish as the main source for surimi production. However, due to the increase in the world’s population and partly the depletion of the fish stocks, followed by a reduction in the surimi production of Allaska Pollock fish (due to restrictive fishing laws), the need to use new species is considered urgent. In this regard, additives such as gums can be used to reform and improve the properties of surimi. Therefore, in this study, the possibility of producing surimi paste and gel from Lizardfish and Talang Queenfish was investigated and the effect of Konjac on the physicochemical properties of the product produced from these two types of fish was evaluated. Materials and methods: In this study, Talang Queenfish and Lizardfish with approximate weight of 225.9±33.6 and 275.9±24.4 g and average size of 15.1±2.4 and 17.3± 2.6 cm, respectively, were purchased freshly from the fish market. After preparing surimi paste from both types of fish, Konjac gum in concentrations of 0.25, 0.50 and 0.75 % (w/w) was added directly to the surimi paste. Then to prepare surimi gel, first, the samples were placed in a water bath at 25 ° C for 3 hours for setting and then cooked at 90 ° C for 20 minutes. After that, the prepared gels were cooled in iced water immediately. The produced paste and gel were evaluated in terms of chemical composition, water holding capacity and color factors. Texture and sensory characteristic were assessed on the produced gels of both types of fish and compared with the control sample (without gum). Results and discussion: According to the results, the yield of Lizardfish was 28% and Talang Queenfish was 22%. It seems that the larger size of Lizardfish has been effective in its higher yield than Talang Queenfish. Based on the results, the percentage of ash, protein and fat in the treatments did not change significantly compared to the control sample. Also, there was no significant difference between the two types of fish in the amount of mentioned factors (p>0.05). As the contraction level of Konjac gum increased, the amount of moisture and water holding capacity of the paste samples of both fish increased significantly, which is due to the absorption and binding of water by the Konjac hydrocolloid. The lightness level (L*) of the surimi paste and gel of both types of fish increased significantly with the addition of Konjac, which is related to the increase in water content in the samples. The lightness of the surimi paste and gel of Lizardfish was higher than that of Talang Queenfish, which is due to the presence of more pigments in the Talang Queenfish meat. Control Sample and treatment of 0.25% of Talang Queenfish surimi paste showed more yellowness and redness than Lizardfish, but in the resulting gel, their values were reduced, indicating that the formation of gel structure by Konjac gum and binding to the proteins covered the yellowness and redness of the samples. By increasing the concentration of Konjac in surimi gel of both fish the parameters of texture (firmness, cohesiveness, adhesiveness, springiness, chewiness) breaking force and deformation increased significantly compared to the control sample. Also, the results showed that the surimi gel from Lizardfish has higher firmness, cohesiveness and strength than Talang Queenfish. Sensory evaluations showed that the panelists assigned the highest score for the surimi gel from Lizardfish to the 0.5% treatment and for the Talang Queenfish to the 0.75% treatment of Konjac. Based on the findings of the present study, it was found that surimi gel from Talang Queenfish has a lower quality than Lizardfish, but with the addition of Konjac gum, its properties can be improved.
Homa Mahpour; Toktam Mostaghim; Shahla Shahriari
Abstract
Introduction: Dairy products fortification especially ice cream is one of the most important goals and priorities of today's humanbeing to produce health food products. Protein isolate is one of the compounds used to produce health products.The aim of this study was to produce ice cream with new features ...
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Introduction: Dairy products fortification especially ice cream is one of the most important goals and priorities of today's humanbeing to produce health food products. Protein isolate is one of the compounds used to produce health products.The aim of this study was to produce ice cream with new features based on a functional material by partially replacing dry matter with wheat germ protein isolate. Materials and Methods: In present research wheat germ protein isolate with 1%, 3% and 5% was extracted and added to ice cream. In the first step, protein isolate was evaluated by tests of moisture content, fat percentage, acid insoluble ash, particle size and flour grain size. In the next step, protein isolate of wheat germ by 1, 3 and 5 percent was added to ice cream mix and its effects on rheological and texture properties, color, physico-chemical and sensory parameters of ice cream were evaluated. Results and discussion: The results showed that the moisture, fat and acid insoluble ash of protein isolate were 8.41±0.42, 11.34±0.44 and 3.57±0.23 respectively. The particle size and flour grain size was 282±0.01. Laboratory data showed that by increasing protein isolate replacement, the viscosity, melting resistance and volumizing index were reduced significantly. Whereas, texture, hardness and adhesion parameters, density, particle size and diameter, specific distribution and surface area, and yellowness and redness indices were significantly increased. All the laboratory results and sensory evaluation of the samples revealed that the ice cream sample with 1 percent of wheat germ protein isolate was a preferred and optimized sample.
Marzieh Salami; Massoumeh Mehraban Sangatash; Ahmad Ehtiati
Abstract
Introduction: Yogurt is one of the most popular dairy products, which has numerous health effects on human body. Dietary fiber consumption is highly recommended. Fibers are highly hydrophilic and absorb water into the digestive track, increase the volume of food and thereby facilitating excretion. These ...
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Introduction: Yogurt is one of the most popular dairy products, which has numerous health effects on human body. Dietary fiber consumption is highly recommended. Fibers are highly hydrophilic and absorb water into the digestive track, increase the volume of food and thereby facilitating excretion. These are some health benefits of these compounds. Consumption of fiber-containing yogurt can be helpful for people who suffer from cardiovascular diseases, hypertension, diabetes and obesity. Zucchini, as a vegetable, is a source of fibers and due to its health-promoting effects, can be used in dairy products. The aim of this study is to evaluate the effects of different levels of dried zucchini on stirred yogurt during storage. Materials and Methods: The raw materials for the production of the functional yogurt were zucchini, milk, skim milk powder, whey powder, hydrocolloids stabilizer compound and starter culture. Fresh zucchini was hot-air dried at 70 °C for 7 hours. Two forms of the dried zucchini (powder and granule) were added to fresh yogurt at levels of 0.7, 1.4, and 2%. The samples were then tested on days 1, 5, 10 and 15 for acidity (titration method), pH, texture stiffness (back extrusion), syneresis, color (using image processing) and sensory properties, including color, taste, aroma, consistency, mouthfeel and overall acceptance. The experiments were triplicated and analysis of variance was performed using Minitab software at 95% confidence interval. For the significant variables, the means were compared using LSD method. Graphs were drawn using MS-Excel. Results and Discussion: The effects of zucchini form and level of addition, storage time and interaction of these variables were significant (P<0.05) on the titratable acidity, pH and firmness. Over time, pH decreased and acidity increased, which was related to the starter activity and acid production. Due to the use of stabilizer and whey protein, all samples showed no syneresis. The firmness of the samples containing zucchini powder was higher than that of the granule- (P<0.05). This might be related to the homogeneous structure of zucchini fiber, which increased water absorption regarding its lower particle size. Firmness increased from day one to day five, due to the high water absorption of hydrocolloids that bind to free water present in the yogurt structure. The presence of milk proteins and whey protein concentrate in the yogurt formula enhanced crosslinking in the particle gel network, which resulted in a stronger gel structure. During longer storage, firmness decreased from day 5 to day 10, probably was due to the increased pH, which affects the proteins and polysaccharides interaction. The effects of the form and level of zucchini and the interaction between these variables were significant (p <0.05) on the changes in L*, a*, and b*. The L* and a* values which were higher in the samples containing zucchini granules than in the zucchini powder, most probably due to the smaller particle sizes of the powder compared with the granules, causing the number of the powder particles per unit volume to be larger and the powder-containing samples to become darker. In terms of the level of addition, L* increased as the zucchini level rose to 1.4% and then declined to 2%. The sensory properties of all samples were significantly affected by the storage time (P<0.05). With increase in the storage time, all the sensory scores increased. The highest overall acceptance score belonged to the yogurt sample containing 1.4% granule on the 10th day of storage. Overall, zucchini is a good candidate for yogurt fortification. This incorporation results in a greenish yogurt with more health functionalities. The highest overall acceptance score was obtained for the yogurt containing 1.4% zucchini granule on the 10th day of storage (best consumption date) and the results showed acceptable firmness for this sample.
Nader Cheraghi; Ebrahim Alizadeh Doughikollaee; Mohsen Shahriari Moghadam
Abstract
Introduction: Recently, the high nutritional value of fish and other seafood has caused continuously increasing their consumption in human diet. The meat quality can be decreased during storage due to physical, chemical and microbial changes. Thus, the different methods of preservation should be used ...
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Introduction: Recently, the high nutritional value of fish and other seafood has caused continuously increasing their consumption in human diet. The meat quality can be decreased during storage due to physical, chemical and microbial changes. Thus, the different methods of preservation should be used to improve the quality and increase the shelf-life of the product. The application of bacteriocinins has been increased to extend the shelflife of food products. Nisin is a kind of bacteriocinins that is produced by Lactococcus lactis bacteria and used as food preservatives. It is accepted such as food additive in many food commodities. Bacteriocinins showed synergistic effects when they used with other antibacterial compounds such as natural preservatives and phenolic compounds. Literature review showed that the antibacterial compounds such as sodium acetate play an important role in preventing the growth of bacteria and increasing the shelf life of fish during different storage conditions. Conventional optimization procedures are performed by altering one parameter at a time and keeping all other parameters at fixed levels. However, these procedures are time consuming and require more experimental data sets. Recently, the use of an orthogonal array approach called ‘Taguchi method’ has been successfully examined in the different field of sciences. Therefore the aim of this research was to investigate the effects of nisin, sodium acetate and temperature on the growth of Staphylococcus aureus in Ctenopharyngodon idella fillet using Taguchi experimental design with an array L4 (23).
Materials and methods: The fresh Ctenopharyngodon idella with weight of 1 kg were purchased from market (Zabol, South east of Iran) and transported in isothermal iceboxes to the fish product processing laboratory at University of Zabol in 2016. The fishes were cleaned and filleted. Fillets after inoculated with Staphylococcus aureus (103 Log CFU/g) and added nisin (750 and 1000 IU/g) and sodium acetate (1 and 2 %) were stored in different temperatures (4 and 8 °C). Chemical parameters (pH, PV, TBA and TVB-N) and Staphylococcus aureus count were measured at 0, 3, 6 and 9 days. Microscopic analysis was used to observe the microstructure changes at end of storage. The experiments were performed in three replicates.
Results & discussion: The present study showed that the lowest and highest Staphylococcus aureus growth was observed in treatment 2 (sodium acetate 2%, nisin 750 IU/g, temperature 4°C) and control at 4 and 8° C, respectively. It is noticeable that the growth of Staphylococcus aureus decreased in treatment 3 (sodium acetate 2%, nisin 1000 IU/g, temperature 8° C) during storage at 8° C. Also, the results showed that the temperature was most important factor on the growth of Staphylococcus aureus in the beginning of experiment and the other factors showed their effect during storage. Therefore, the highest and lowest effect was related to temperature and nisin at the end of experiment, respectively. In the present study, the additives could be prevented the growth of bacteria with except in treatment 4 (sodium acetate 1%, nisin 750 IU/g, temperature 8° C). The inhibitory effects of nisin and sodium acetate on the growth of Staphylococcus aureus was better shown with increasing storage time. The TVB-N of fillets increased during storage but this increase was lower in treatment 2 than the other treatments. The temperature and nisin had a significant effect (p
Lida Shashavani Mojarrad; Ali Rafe
Abstract
Textural, thermal and microstructural properties of single component gels and binary composite gels (BCG) of high amylose corn starch (Hylon VII) mixed with wheat flour at different wheat flour/Hylon VII (WF/H) ratios (95:5, 90:10 and 85:15) and temperatures (100, 121 and 135ºC) were investigated. ...
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Textural, thermal and microstructural properties of single component gels and binary composite gels (BCG) of high amylose corn starch (Hylon VII) mixed with wheat flour at different wheat flour/Hylon VII (WF/H) ratios (95:5, 90:10 and 85:15) and temperatures (100, 121 and 135ºC) were investigated. The visual appearance showed that as Hylon VII was increased in BCG, the stronger gel was achieved. Textural results confirmed by increasing Hylon VII, the firmness was increased, but the springiness, cohesiveness and adhesiveness were reduced. Moreover, the BCG at high temperatures showed the higher level of Hylon VII, the higher water solubility index would be achieved. The gelatinization enthalpy (ΔH) and peak gelatinization temperature (Tp) increased by improving the content of amylose in BCG. Hylon VII showed the lowest peak viscosity and the BCG gel containing high amount of Hylon VII indicated a reduction in the paste viscosity. The differences in the microstructure of WF and HylonVII gels were also reflected the pasting properties of the gels. Consequently, BCG of WF/H develops the stronger gel which can withstand at high thermal processing such as retort to improve the shelf-life of the final product.
Asefeh Latifi; Mohsen Esmaiili
Abstract
Introduction: More than half of the world's people consume rice. Rice consumers, especially in Asia know that cooking properties of rice change with its storage. This phenomenon is called aging. The increase in hardness, decrease in adhesiveness during cooking and decrease in solid loss, are the major ...
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Introduction: More than half of the world's people consume rice. Rice consumers, especially in Asia know that cooking properties of rice change with its storage. This phenomenon is called aging. The increase in hardness, decrease in adhesiveness during cooking and decrease in solid loss, are the major changes in rice which caused by aging. However, while some consumers prefer new rice like Japanese (Zhou, 2002) Iranian and many other consumers prefer aged rice. The change in physicochemical properties of aged rice is caused by the alteration and interaction in lipid, protein and starch (Juliano, 1985; Sodhi, et al. 2003; Teo et al. 2000). The conventional aging of rice takes 3-6 months (Jaisut et al. 2009; Soponronnarit et al. 2008).Yet this method needs more space for storage leading to high operating costs. It is necessary to examine other methods that can reduce the aging time and maintain the rice properties similar to those obtained by the conventional aging process. The process for accelerated aging could be developed either by dry or wet heat (Rayaguru et al. 2011; Rosniyana et al. 2004). The dry heat method was successfully tested with heating of rice in high temperatures in a closed container (Battacharya, 2013). One of the basic problems that occur during dry heating is that any moisture loss leads to cracking. Although the concept is simple in theory, it is complicated in practice. Another drying process for accelerated aging of rice employs a fluidized bed dryer. However, this may decrease head rice yield (Soponronnarit et al. 2008; Wiset et al. 2005), not to mention the fact that these dryers are rare and expensive in rice producing countries. Hence, wet heat is more practical and economical in the mentioned countries. The environmental optimum conditions for accelerated aging of Basmati paddy, at temperature 30–50 °C, relative humidity 50–90% and aging period 3–14 days, has been studied and reported to be 43 °C, 71.0% relative humidity (RH) and 11 days (Rayaguru et al., 2011). Parboiling has been implemented as a method of improving the quality of rice. Nonetheless, it is a lengthy process involving soaking, steaming and drying, which results in the complete gelatinization of starch (Gujral, and Kumar, 2003). According to the importance of accelerated aging, the aim of this study was to evaluate quality attributes and physicochemical properties improvement of Tarom variety of paddy.
Materials and methods: In this study, Tarom variety of paddy (a local variety, with high-quality and large area cultivation in Mazandaran province) was chosen. For accelerated aging, two methods were done: Steaming (or steam curing) and controlling the environmental conditions. In steaming method, the paddy was divided into two portions. The first which had an initial moisture content of 24% (wet base) and the second was the paddy which had been rested at the ambient temperature allowing its moisture content to reach 17%. To accelerate aging of the paddy in two moisture levels i.e. 24 and 17%, the samples were treated by steaming (or steam curing) for 5, 10 and 20 min, and then both of samples were dried with fixed bed dryer at 40 ◦C until the grain moisture content reached 11%. Afterwards, the paddy samples were dehusked and polished with satake miller apparatus. Milled whole rice kernels were separated from broken rice for evaluation of physicochemical properties. In controlling the environmental conditions, the samples were dried with fixed bed dryer at 40 ◦C until the moisture content reached 12%, and then stored at 43 °C and RH=74% for 11 days. Similarly, to produce white rice, the paddy samples were dehusked and polished as mentioned above. The control sample which had an initial moisture content of 24% (wet base) was only dried at 40 ◦C to moisture contend wet basis 11%. Several parameters including head rice yield (the percentage of the mass of white rice that remained as head rice after milling), hardness of raw kernel (the maximum force for breakage of raw white rice), color (b value), chalkiness (weight of the kernel that had chalkiness over one half of the kernel surface in 5 gram of white rice), aroma (using hedonic test), pasting properties (including the peak viscosity, final viscosity, breakdown viscosity and setback viscosity), texture profile analysis (TPA) and thermal properties of rice (the onset temperature, peak temperature, conclusion temperature and enthalpy of gelatinization) were determined. The resultant data were subjected to the analysis of variance using SPSS (ver. 19) software. Duncan’s test was used to establish the differences between mean values at 95% confidence interval.
Results and discussions: The quality attributes of the produced white rice were compared with that of the control samples. By doing the steam curing treatment, solid loss of the rice decreased, adhesiveness decreased, gelatinization temperature increased and viscosity changed. All of the mentioned changes were similar to the alterations that occur in naturally aged rice. By controlling the environmental conditions, the solid loss decreased and the elongation increased. According to sensory and apparent characteristics including aroma and chalkiness, treatment by controlling the environmental conditions could be recommended. Steaming treatment for the three levels of time led to complete loss of aroma.
Hossein Jooyandeh; Erfan Danesh; Mostafa Goudarzi
Abstract
Introduction: Health-conscious consumers are interested in eating dairy products including ice cream with less fat. As a consequence, the dairy industry has developed a variety of reduced-fat ice cream products. However, quality aspects of many of these products do not meet consumer expectations for ...
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Introduction: Health-conscious consumers are interested in eating dairy products including ice cream with less fat. As a consequence, the dairy industry has developed a variety of reduced-fat ice cream products. However, quality aspects of many of these products do not meet consumer expectations for ice cream flavor, texture, and appearance. The formation of the ice cream structure is hindered when the fat content is reduced and attributes related to quality, such as viscosity, ice crystallization, hardness, melting rate and flavor, are affected. Low melting resistance, high firmness and undesirable flavor are the most cited defects in reduced-fat ice creams. Enzymatic treatment of reduced-fat milk with microbial transglutaminase has been found to improve the textural and sensory properties of the final dairy products. The transglutaminase enzyme (MTGase; protein-glutamine gamma glutamyl transferase, EC 2.3.2.13) catalyses “acyl” transfer reactions between γ-carboxyamide groups of glutamine residues (acyl donor) and the ɛ-amino group of lysines (acyl acceptor) in proteins, leading to inter- or intra-molecular cross-linking. The enzyme-catalyzed cross-linking of milk proteins results in the formation of high molecular weight polymers that not only are able to lower the melting rate thorough increasing the viscosity of ice cream mix, but they could also provide a smoother texture for the product by mechanically obstructing ice crystal growth. However, the extensive cross-linking of milk proteins may even adversely affect the physical properties of the resultant ice cream and thus, the added amount of enzyme needs to be adequate for the desired effects. The aim of this study was to investigate the effects of different concentrations of TGase enzyme on physical and sensory properties of light ice cream in order to selct the appropriate amount of enzyme concentration that provides the best results.
Materials and methods: The light ice cream (5% w/w fat) was treated with different concentrations of TGase enzyme (2, 4 and 6 units/g milk protein). The enzyme-treated samples were investigated for flow behavior characteristics (apparent viscosity, flow index, consistency index), overrun, melting rate, hardness and sensory properties (flavor, texture, color and total acceptability) in comparison with control light ice cream with no added Tgase.
Results and discussion: The results revealed that TGase treatment effectively increased the viscosity of light ice cream.The higher the enzyme concentration, the greater the viscosity of ice cream samples. This could be attributed to TGase-catalyzed formation of large protein polymers in ice cream mix that resist to flow. All enzyme-treated ice cream mixes exhibited shear-thinning behavior, where the viscosity decreased with increasing shear rate. The power law model was used to find consistency and flow indices for different treatments. The results showed that consistency index increased and flow behavior index decreased with TGase concentration. The stronger shear-thinning behavior (lower flow index) of the samples treated with higher concentration of TGase might be arisen from formation of higher number of large protein polymers in theses samples, which decrease in size during shearing. The enzyme treatment significantly increased the overrun of the light ice cream that could be due to the increasing effect of TGaes on the viscosity. The increase in viscosity promotes the retention of air in the ice cream which is concomitant with increased overrun; however, high viscosity reduces the whipping rate leading to lower incorporation of air into the ice cream and thus decreased overrun. This may account for significantly lower overrun of the light ice cream treated with 6 units TGase/g milk protein than the samples treated with 4 units TGase /g milk protein. It was observed that the enzyme treatment caused a significant improvement in melting resistance of light ice cream. In fact, the light ice cream treated with 6 or 4 units TGase /g milk protein took the longest time to melt, followed by the samples treated with 2 and 0 units TGase /g milk protein. This is somehow in accordance with the results of overrun; that is, the ice cream with higher overrun melted slower attributed to a reduced rate of heat transfer due to a larger volume of air. The overrun could also affect the hardness of ice cream as evidenced by the results of the present study. The results showed that the samples with greater overrun were softer. It could be assumed that the air cells, together with large protein polymers formed via catalytic action of TGase, limited the size of ice crystals by exerting mechanical hindrance, providing a softer texture for the enzyme-treated ice creams. Not surprisingly, the enzyme treatment did not considerably influence the flavor of light ice cream albeit the sample treated with 6 units TGase /g milk protein received significantly lower score than the other samples. Conversely, the color of enzyme-treated samples was more appreciated by consumers than the sample without added TGase possibly because of light scattering properties of enzymatically formed protein polymers in theses samples. Consistent with the results of physical properties, the texture of light ice cream treated with 4 or 6 units TGase /g milk protein were ranked as the most desirable samples, followed by the samples treated with 2 and 0 units TGase /g milk protein. The order of light ice cream samples for total acceptability scores was the same as that for texture scores with the exception of the sample treated with 6 units TGase /g milk protein whose total acceptability score was lower than the sample treated with 4 units TGase /g milk protein.
Hassan Sabbaghi; Aman Mohammad Ziaiifar; Mahdi Kashani-Nejad
Abstract
Introduction: Texture is one of the most important attribute in foods and is always issues for the manufacturing of fried products, because texture plays a crucial role in consumer acceptance and the perceived quality of foods. Prediction of changes in texture during frying can be helpful in process ...
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Introduction: Texture is one of the most important attribute in foods and is always issues for the manufacturing of fried products, because texture plays a crucial role in consumer acceptance and the perceived quality of foods. Prediction of changes in texture during frying can be helpful in process control. Structurally, this quality parameter in fried potato strip made from the formation of a composite structure with two layers as: dry and oily outer layer (crust), and a moist or soft interior layer (core). So, the explanation of texture development during frying is difficult because of the innate heterogeneity of the fried potato tissue. Moreover, both thermal degradation and texture development are functions of variables such as processing time, oil temperature and vaporized moisture of product. Textural changes during frying described as the result of various physical, chemical, and structural changes involved in the frying process. One solution to reduce the complexity of real bio systems in engineering is using various empirical correlations. Application of these relations for prediction of textural changes during frying can help us for understand the proper conditions to achieve desired texture. The purpose of the present investigation was to study the influence of the frying temperatures on texture of potato strips. In fact, textural changes during various stages of frying potatoes including initial heating, surface boiling and falling rate period were investigated. Texture evaluation is done by mechanical measurements, because the stimulus in texture perception is mainly mechanical. Also, textural studies are not clearly performed up to now with focus on cook value as a main factor in potato frying. According to the definition of cook value, this parameter indicates total time of baking in 100 °C. Fractional conversion applied as a technique for analyzing texture degradation kinetics and softening of vegetables upon prolonged heating. A few assumptions were made during study: i) Potato shrinkage is neglected ii) Product is not completely dried iii) The stages of frying were considered separable only based on surface and center temperature iv) Texture of potato strips affected by cook values of each frying stages. Materials and methods: The potato strips with specified size fried at a constant temperature of 145, 160 and 175 °C for 30, 60, 90, 120, 150, 180, 210 and 240 seconds. Then, various stages of the process were separated using surface and center temperature profiles of product that were recorded by data logger and T-type thermocouple in computer. Heating extremity of each stage was determined using cook value parameter. Mechanical properties such as apparent modulus of elasticity (Secant modulus) and toughness were used to show which occurred during frying. The secant modulus (S) variations described using fractional conversion model. The degree of cooking for each sample was expressed in term of cook value and its relationship with the overall acceptance of product was examined. Finally, the suitable temperature was determined by sensory evaluation to achieve the desired texture to determine the proper cook value and to prevent over cooking of product. Results and Discussion: The stages of frying by immersion for experimental conditions can be divided as: I. Initial heating (The first 30 seconds for all oil temperature) II. Surface boiling (30-60 s). III. Falling rate (up to end, longest period). IV. Bubble end point (not considered). Generally, higher oil temperature showed larger center and surface cook values because of the fast temperature increase inside product. During initial heating period (I) because of temperature increase without boiling, the changes in cook values versus time are negligible. Surface cook value increased slowly compared with core during surface boiling. Maximum cook value for core temperature was higher, because of the vapor pressure at the center of the product and thus water evaporation at temperatures above 100 °C (cook value above 1 second). During falling rate period due to gradual reduction of evaporation rates, and thus the vapor pressure drop within product, boiling temperature reduced to 100 ° C. The major part of texture destruction occurred during initial heating period and the changes of textural characteristic were going to be constant at the end of surface boiling. The slope of the regression line for fractional conversion model decreased as temperature increased and therefore product was harder, but equivalent value of secant modulus was independent of process temperature. The consumer texture desired was found for temperature of 160 °C with medium cook value. The kinetics of potato softening followed an exponential decay equation with good correlation on empirical data. The temperature dependence of the degradation rate was reliably modeled by the Arrhenius equation. Activation energy (Ea) for model parameters Se and Ks was 13047.12 and -24949.74 J/mol, respectively. Negative Ea for kinetic constant (Ks) indicated an inverse relationship with oil temperature. In addition, elevated oil temperatures caused less softening of French fries because of higher cook value and thus higher evaporation rate.
Narges Samanian; Seyed Mohammad Ali Razavi
Abstract
Sensory evaluation of food materials is an important factor to choose and even produce new formulations. Being time consuming, results in being difficult to interpret and the necessity to educate specialists make these methods kind of impractical. In this study, we have made an effort to introduce physical ...
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Sensory evaluation of food materials is an important factor to choose and even produce new formulations. Being time consuming, results in being difficult to interpret and the necessity to educate specialists make these methods kind of impractical. In this study, we have made an effort to introduce physical properties as a substitute for sensory evaluations in a semi solid food such as chocolate pudding. Higher reliability, reproducibility and higher pace are among some of the advantages of instrumental measurements. Thus, if sensory evaluation can be predicted based on physical properties solely, besides increasing the inspection pace, they would be available to be used online. The obtained results can also be used in designing new products for special consumers such as the dysphasia patients. The results showed that parameters such as shear viscosity, plastic viscosity, yield stress, extensional viscosity, apparent modulus and adhesive force can be used to design and produce new materials; they make sense beside each other though. In this way, the products which have been designed for the patients with swallowing difficulties should have suitable texture in mouth and also good swallow ease.
Sepideh Amirabadi; Arash Koocheki; Mohebbat Mohebbi
Abstract
In this research, different concentrations of xanthan and Lepidium perfoliatum seed gums (0.1, 0.2 and 0.3%) were used to improve the quality and shelf-life of chiffon cake. For this purpose, specific gravity and apparent viscosity of batter, and the volume, specific volume, moisture, sensory and texture ...
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In this research, different concentrations of xanthan and Lepidium perfoliatum seed gums (0.1, 0.2 and 0.3%) were used to improve the quality and shelf-life of chiffon cake. For this purpose, specific gravity and apparent viscosity of batter, and the volume, specific volume, moisture, sensory and texture properties, crumb and crust color were examined. To investigate the effect of gums on the shelf-life, all cakes were stored for sixth days. Results showed that there were a positive correlation between viscosity of batter and cake volume. Both gums improved chiffon cake properties after removing from the oven and during storage. It was found that using 0.1% xanthan gum increased the cake volume, cohesiveness and sensory scores, decreasing firmness and moisture loss during storage of cake.
Soheil Amiri; Mehran Alami; Amir Daraei Garmekhani
Abstract
Mayonnaise is a popular product which is consumed in large amounts. However, many consumers consider it as a unhealthy product as it contains high amounts of oil. Therefore, production of low fat mayonnaise with a quality close to that of traditional one might respond to consumer demand. In the present ...
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Mayonnaise is a popular product which is consumed in large amounts. However, many consumers consider it as a unhealthy product as it contains high amounts of oil. Therefore, production of low fat mayonnaise with a quality close to that of traditional one might respond to consumer demand. In the present study, gum tragacanth was used as a fat replacer for the preparation of low fat (LF) mayonnaise. Mayonnaise samples were analyzed in terms of their rheological, textural and sensory properties. Fat was partially substituted by gum tragacanth at levels of 20%, 30%, 40% and 50%, and the samples were referred as TRF20%, TRF30%, TRF40% and TRF50%, respectively. The full fat (FF) mayonnaise (75% oil) without gum tragacanth was used as a control. Results indicated that all LF mayonnaise samples had significantly lower energy content than control, but they had higher moisture content than their FF counterpart. In terms of textural properties, the highest value for firmness and adhesiveness was observed in TRF20%. There were no significant differences between the FF and TRF50%. In terms of rheological properties, all of mayonnaise samples exhibited thixotropic shear thinning behavior. In sensory evaluation, in terms of total acceptability, the highest score belonged to TRF20%, but there was not observed significantly difference in other samples. This study showed that gum tragacanth has high potential to use as a fat replacer in mayonnaise.
