Food Engineering
Fatemeh Yousefzadeh; Masoud Taghizadeh
Abstract
Introduction The consumption of milk and its products is considered as a main indicators of development of human societies. In order to promote the health of children and provide the sufficient amount of calcium and nutrients and make the consumption of these products attractive. Necessary measures ...
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Introduction The consumption of milk and its products is considered as a main indicators of development of human societies. In order to promote the health of children and provide the sufficient amount of calcium and nutrients and make the consumption of these products attractive. Necessary measures should be taken to increase milk consumption in society and increase the diversity of these products (Keshtkaran et al., 2013). Gelatin as one of the gelling agents used in dairy desserts is a hydrocolloid with unique functional properties and has been used in various industries for a long time (Karim & Bhat, 2008). Gelatin is extracted from the partial hydrolysis of skin collagen, white connective tissue, and animal bones. One of the problems with using gelatin in dairy desserts is the instability at ambient temperature. Therefore, it is necessary to evaluate the characteristics of other native hydrocolloids as an alternative. Tragacanth is a dried gum secreted from several plant species and Iran is the largest exporter in the world. Structurally, the material is regular, odorless and hard. It can be used in various food products. The simultaneous utilization of hydrocolloid mixtures is used to create a synergistic property and to improve these products. Starch originated from a variety of sources , including corn, rice, wheat, potatoes, cassava, bananas, and sorghum (Murphy, 2000) is used in the food industry. Among the sources of starch production, wheat is cultivated in large quantities in Iran. Materials and Methods In this study, pasteurized milk was purchased from Salamat Dairy Products Company, gelatin made in Pakistan, tragacanth gum and Gonabad wheat starch were purchased from Kian Shimi Company and sugar and vanilla were purchased from confectionery stores located in Mashhad. Ingredients for dessert production include 80% milk, 10% sugar, 0.1% vanilla, tragacanth gum at concentrations of 1.3%, 1%, and 0.7% and starch at concentrations of 3% , 2%, and 1% by weight (powder selection) according to the method of Tarrega et al. 2004 with a slight modification. A sample containing 1.5% gelatin was considered as a control sample. The mixture was heated to 90 ° C for 20 minutes, stirring at medium speed. The samples were then placed in special containers and cooled to ambient temperature. Prior to testing, the samples were refrigerated (4-5 ° C) for 24 hours. The samples were coded based on the concentration of gum and starch (: T% of tragacanth gum and: S% of wheat starch). Results and Discussion The flow behavior in all dairy dessert samples was similar to the control and was pseudoplastic type. The Power model was selected as the best model (R <98, RMSE> 1.6). As the concentrations of tragacanth gum and wheat starch increased, the parameters of hardness, consistency, adhesion and adhesion strength increased significantly, and the samples 0.7T2S, 0.7T3S and 1T, 1S had the same value in terms of all textural parameters. At constant concentration of starch, with increasing tragacanth gum from 0.7% to 1.3%, the rate of syneresis of samples decreased from 0.34% to 0.06% and at constant concentration of gum, with increasing concentration of wheat starch, Syneresis decreased significantly from 0.34 to 0.24%. Increasing the shelf life of the samples naturally led to an increase in syneresis. In the samples 0.7T3S, 1T3S, 1T2S, and 1.3T3S, the increase of syneresis occurred to a lesser extent.. According to the results of analysis of variance, the effect of gum on zeta potential was very significant (p <0.05). Increasing the concentration of hydrocolloids in most samples led to an increase in the amount of negative charge and zeta potential. In most samples, at a constant concentration of tragacanth gum, with increasing the concentration of wheat starch from 1% to 3%, the span decreased, while at a constant concentration of starch, the increase in tragacanth gum from 0.7% 0 to 1.3% led to increase the span. Among the dairy dessert samples, 5 dairy dessert samples include: 0.7T2S, 0.7T3S, 0.7T1S, 1T2S and 1.3T1S, were selected the best in terms of physical and rheological characteristics to the control sample. They were more similar, selected and used for sensory evaluation. The results of comparing the mean of the data showed that different concentrations of tragacanth gum and wheat starch had a significant effect on the sensory characteristics of the samples including: color, flavor, sweetness, adhesion, gum state and overall acceptance (P> 0.05) and increasing the concentration of tragacanth gum and wheat starch had no significant effect on other sensory properties (p> 0.05). Conclusion In general, due to the similarities of the physical, rheological and sensory properties of the treatment samples with the control, 1S1T sample was selected as the most suitable sample to replace the sample containing gelatin.
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.
Azam Sattari; Jafar Mohammadzadeh Milani; Zeynab Raftani Amiri; Ali Pakdin Parizi
Abstract
Introduction: Oat establishes a healthy basis for food products. It has gained relevance in human nutrition because it is one of the few cereals with a high content of soluble fiber namely β -glucan, and is a good source of proteins, vitamins, and minerals (Butt et al., 2008). β-glucan is one ...
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Introduction: Oat establishes a healthy basis for food products. It has gained relevance in human nutrition because it is one of the few cereals with a high content of soluble fiber namely β -glucan, and is a good source of proteins, vitamins, and minerals (Butt et al., 2008). β-glucan is one such polysaccharide that has received much attention from the past few years due to its several health beneficial properties, including the ability to remove free radicals in a way identical to antioxidants (Gardiner, 2000). β-glucan is an unbranched polysaccharide consisting of β-D-glucopyranose units linked through (1→4) and (1→3) glycosidic bonds in cereals and (1→6) glycosidic bonds in fungal sources (Ahmad et al., 2016). β-glucan from different sources vary in their molecular structure, chain conformation, solubility, number of β- (1→3)- or β-(1→6)-linkage, and thus different biological activities (Descroix et al., 2006). β-glucan is regarded as an important functional ingredient to lower serum cholesterol, promote weight management, reduce glycemic response, enhance immune system, besides having a prebiotic effect (Zhu et al., 2016; Shah et al., 2016). β–glucan from barley and oat at a 3 g/day dosage as recommended by FDA would reduce cardiovascular disease risk including a reduction in blood glucose and also has satiety effects. Therefore, in order to meet the demands of people related to diets that have a low glycemic index and antioxidant property, non-starch polysaccharides like β-glucan can be used as an ingredient in the products to develop new functional foods (Lee et al., 2016). Oat grain’s fat content is more than that of wheat and it is full of lipase, lipoxygenase, and other hydrolytic enzymes. Over time, enzymes lead to the hydrolysis of the fats present in the oat that make the rancidity taste. Due to the effect of enzyme activity on the stability of oat flakes, these enzymes need to be deactivated during oat processing. One of the methods for disabling enzymes is a hydrothermal process (Doehlert et al., 2010). In this study, the effect of the hydrothermal process using autoclave on the physical and rheological properties of oat β-glucans at different times and temperatures has been investigated. Materials and methods: In this study, beta-glucan was extracted from oats using the hot water extraction method. Hulled oat grains, it put into the autoclave for hydrothermal processing, at three different temperatures of 110, 120 and 130°Ϲ in two different times (10 and 20 minutes) intervals, to measure the effect of time and temperature on physicochemical and functional and rheological properties of β-glucan. After extraction, the physiochemical and functional properties of extracted β-glucan such as solubility, foaming, foaming stability and rheological properties were tested. In order to measure the moisture, ash and protein content, the standard methods (AOAC, 2005) were used. The fat content of the flour was measured by the standard AACC method 25-30. The starch was determined by polarimetry method. For solubility measurement, according to Betancur-Anoka (2003) method, after preparing 90 ml of 1% w / v solution from each sample β-glucan, it was divided into 3 equal parts. Then each of them was placed in a warm bath of 25, 50 and 75 °C for 30 minutes. After centrifuging for 15 minutes at about 8000 g, 10 ml of the upper clear solution was transferred to an oven at 125 °C to reach a constant weight. Finally, solubility percentage at different temperatures was calculated.The foaming capacity and foam stability were studied using the temelli method (1997). For this purpose, 2.5 g, β-glucans was dissolved in 100 mL distilled water. The resulting solution was mixed vigorously for 2 min using a hand held food mixer at high speed in a stainless steel bowl with straight sides and volumes were recorded before and after whipping. To determine foaming capacity, foams were slowly transferred to a 1000 mL graduated cylinder and the volume of foam that remained after staying at 25 ± 2°C for 2 h was expressed as a percentage of the initial foam volume (Temelli et al. 1997; Ashraf Khan et al., 2016). β -Glucan gum solutions were prepared in duplicate in the desired concentration (1.0% of gum, w/w) using distilled water. The rheological properties of the samples were studied by an Anton Paar Physica Rheometer (Physica, MCR 301, Anton Paar GmbH, Germany), with a parallel plate geometry. Results and discussion: β-glucan obtained from hydrothermal process on oat flour at 120°C for 10 minutes had the highest solubility at 25°C and the lowest solubility at 50°C, and 130°C treatment for 10 minutes had the highest solubility at 75°C from hydrothermal process on oat flour at 120°C for 10 minutes had the highest solubility at 25°C, and the treatment of 110°C for 10 minutes and also the treatment of 120°C for 20 minutes had the highest solubility at 50°C and 75°C. The amount of foam in treatment at 130°C for 10 minutes were lower than other treatments and the treatment at 110°C for 10 minutes had the highest foaming stability. In the study of rheological properties, the effect of shear rate on viscosity showed by increasing the shear rate, viscosity decreased in all samples. β-glucan from hydrothermal process on oat flour at 120°C for 10 minutes, had the highest amount of viscosity. In the temperature sweep the parameters included G′ modulus and G″ modulus, the amount of G′ and G″ in β -glucan sample that extracted from hydrothermal process on oat flour were decreased in all samples. Also, G′ and G″ of extracted β-Glucan from hydrothermal process on oat flour at 120°C for 10 minutes was higher than other treatments. In the frequency sweep, at a lower frequency, the amount of G″ was more than G′, and both of them were increased by an increasing frequency and the amount of G′, G″ and η* at 120°C for 10 minutes was higher than other treatments in the frequency of 1 and 10 (Hz). The results showed that the hydrothermal process had a significant effect on the properties and functional properties of β -glucan. Extracted β -glucan sample at 120°C for 10 minutes had the highest solubility at 25°C, and the sample had the lowest solubility at 50°C. The sample treated at 120°C for 20 minutes had the highest solubility at 75°C. The foaming capacity of the sample at 130°C for 10 minutes was lower than other treatments and the treatment at 110°C for 10 minutes had the highest foaming stability. In the study of rheological properties, the effect of shear rate on viscosity decreased in all samples and the treatment of 120°C for 10 minutes had the highest amount of viscosity. In temperature sweep measurement, the amount of G′ and G″ were decreased in all samples and at 120°C for 10 minutes it had the highest amount of G′ and G″. In the frequency sweep, at a lower frequency, the amount of G″ was more than G′, and both of them were increased by an increasing frequency and the amount of G′, G″ and η* at 120°C for 10 minutes was higher than other treatments in the frequency of 1 and 10 (Hz).
Ali Motamedzadegan; Elahe Omidbakhsh Amiri; Mahboubeh Jamshidi; Tandis Khosravi rad
Abstract
Introduction: In industrial operations, a product is submitted to a range of shear rates. The knowledge of the changes in rheology with temperature, frequency and shear rate is needed to design the equipment of operations. The lemon juice is used extensively in the food industry. Information about rheological ...
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Introduction: In industrial operations, a product is submitted to a range of shear rates. The knowledge of the changes in rheology with temperature, frequency and shear rate is needed to design the equipment of operations. The lemon juice is used extensively in the food industry. Information about rheological and physicochemical properties is important for scale up and optimization of processes such as transport and storage of concentrated lemon in commercial applications. The aim of this study was toevaluate the rheological and physicochemical properties of the concentrated lemon produced using vacuum evaporator.
Materials and Methods: Lemon juice was concentrated to 25, 35, 45, 55 and 65 Brix by a rotary evaporator under vacuum at 65°C. The content of soluble solids in terms of brix using refractometer, pH, acidity in terms of citric acid, color in terms of a* , b* and L*, flow behavior and viscoelasticity as function of strain, frequency and temperature using rheometer were investigated. Mean comparison carried out using the least significant difference.
Results&Discussion: As brix increased, pH reduced and acidity increased. An increase in the concentration resulted in a decrease in L* and b* parameters and an increase in a* parameter. Enzymatic browning in this study could be ignored due to the sensitivity of enzymes to temperatures above 50°C. Millard's non-enzymatic browning (formation of hydroxyl methyl furfural and its polymerization) and the degradation of pigments might be a major contributor to color variation, although a decrease in moisture content and an increase in soluble solids are other reasons for darkening of color. Based on coefficient of determination (R2) and root mean square error (RMSE), we could state that the Newtonian and Bingham models had the best fit with laboratory data of the stress-strain obtained for the control sample with the 7Brix, and the samples with 25 and 35 Brix. Newtonian and Bingham viscosity increased as brix increased (p
Maryam Farahmand; Mohammad Taghi Golmakani; Asgar Farahnaki; Gholam Reza Mesbahi
Abstract
Introduction: The pomegranate (Punica granatum L.) belongs to the family Punicaceae, which is planted around the world in different microclimatic areas. The pomegranate production has grown uninterruptedly, which is presumably due to the increasing consumer awareness of the benefits attributed to pomegranate ...
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Introduction: The pomegranate (Punica granatum L.) belongs to the family Punicaceae, which is planted around the world in different microclimatic areas. The pomegranate production has grown uninterruptedly, which is presumably due to the increasing consumer awareness of the benefits attributed to pomegranate and its polyphenols. Pomegranate fruit has valuable compounds with functional and medicinal effects like antioxidant, anticancer, and anti-atherosclerotic effects. Storage of juice concentrate can have a dramatic impact on physicochemical quality. The bioactive compounds and antioxidant activity in fruit juice products are influenced by many external factors like different storage temperatures. Knowledge of the rheological behaviour of juice products is essential for product development, design and evaluation of process equipment like pumps and piping. Pomegranate concentrate is so susceptible to the condition of storage, which results in a reduction in consumer acceptability and quality losses. Accordingly, the industrial concentrate stores frozen (-20 °C) which has a lot of costs to the producer. The objectives of this study were to evaluate the degradation visual color, the rheological characteristics of pomegranate juice concentrates, the stability of phytochemicals, the antioxidant activity, and the haze formation of reconstituted pomegranate juice concentrate during storage at different temperatures to determine the best storage conditions to reduce the quality losses and solving the problem about high cost of storage.
Materials and methods: The concentrated pomegranate (Punica granatum (L.) cv. Rabab) juice used in this study supplied from Narni (Green farm, Neyriz, Iran) factory. The pomegranate juice concentrate was poured into falcons for measuring physicochemical attributes, and micro tubes for determination of antioxidant activities. Then the samples were divided into four parts and stored equally in four different temperatures (-20, 4, 20, and 35 °C). The control samples were stored at -80 °C as fresh sample for the storage period (140 days). Folin-Ciocalteu reagent and 2,2-diphenyl-1-picrylhydrazyl radical (DPPHº) were supplied from Sigma-Aldrich Company (St. Louis, MO, USA). All other chemicals were of analytical grade and purchased from Merck Company (Darmstadt, Germany). The total soluble solid (TSS) was determined with a digital refractometer (Carl Zeiss, Germany). Total insoluble solid was measured by centrifugation at (5,000 × g) according to the IFFJP method 60, using a high speed centrifuge (Ibarz et al., 2011). The haze formation of reconstituted juice was determined by “settling” in a glass tube for 3 hour at room temperature. Color measurements of the juice samples were carried out using a HunterLab (CHROMA METER CR-400/410, KONICA MINOLTA, Japan) after dilution. The rheological characteristics of the pomegranate juice concentrate stored in different temperatures were studied by using a computer controlled rotational viscometer. Sample compartment was monitored at a constant temperature (25°C) using a water bath/circulator, while TSS was 65 °Brix. The viscosity measurements, was carried out According to the methods described by Cárdenas et al., (1997), using a Brookfield cone and plate viscometer (DVII pro Brook field, USA) between the shear rate of 0.5–200 (1/s). Total phenolic content of samples was measured according to the Folin-Ciocalteu colorimetric method (Sun et al., 2007). Total flavonoid content in juices was determined via a spectrophotometer according to the method of Chang et al. (2002). Radical scavenging activities of the samples were measured by using DPPHº as described by Mazidi et al., (2012). The ferrous ion reducing antioxidant power (FRAP) of the samples was measured calorimetrically according to the method by Fawole and Opara (2013). All analyses were performed by the Statistical Analysis System (SAS) software V 9.1 (SAS Institute, Inc., Cary, NC, USA). By using the analysis of variance (ANOVA), the differences among means were determined for significance at P< 0.05.
Results and discussion: The industrial pomegranate juice concentrate stored at (-20, 4, 20, and 35 °C) for 20 weeks, and some physicochemical properties like the second turbidity, CIE Lab color parameters, the rheological properties, the bioactive component (total phenolic and flavonoid contents), and antioxidant properties (FRAP and DPPH) investigated in order to determine the best condition of storage. The second turbidity was obvious among the samples stored at 35 °C in the last fourth weeks. Although there were no significant differences among L* value of the samples stored at -20, 4, and 20 °C, a* and b* value of the samples stored at -20 and 4 °C had the same reduction trend for 14 weeks. Even though the control samples had shear thinning behavior, the samples showed a dilatant behaviour after storage. Antioxidant activities measured via DPPH and FRAP sowed reduction with increasing time and temperature. Flavonoid content increased by increasing time and temperature. In conclusion, storage at 4 °C for 14 weeks was the best storage condition to keep the quality and reduce the costs.
