Sedigheh Amiri; Soleiman Abbasi; Hamid Ezzatpanah
Abstract
In this study, microemulsification of orange peel oil (OPO) using Tween 60:propanol with the ratio of 1:1 was studied under different conditions of pH, ionic strength, and sugar concentration.. Results showed that critical temperature (the temperature in which one- phase microemulsion system was still ...
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In this study, microemulsification of orange peel oil (OPO) using Tween 60:propanol with the ratio of 1:1 was studied under different conditions of pH, ionic strength, and sugar concentration.. Results showed that critical temperature (the temperature in which one- phase microemulsion system was still stable) for the microemulsions with higher sucrose concentrations (in the range between 0 to 30%) was lower while by decreasing in sugar concentration, critical temperature shifted to higher temperatures, as it reached to 90°C for the samples without sugar. The prepared microemulsions were stable at 5 and 25°C for seven days, but samples with higher concentrations of sugar (25 and 30%) became turbid at 45°C, whereas all other samples exhibited a one-phase microemulsion system at this temperature. Microemulsions were not stable at -3°C (freezing temperatures). In sensory evaluation, it was observed that the microemulsified OPO was dissolved in water as soon as it was added into the medium, in contrast to free essential oil as it was spreading on the surface of the solution. Encapsulation of OPO caused lower release of aroma, resulting a milder odor and taste (lower intensity) in samples which were preferred by the panelists. The overall acceptability of all samples containing OPO microemulsion was significantly higher than samples with free essential oil.
Fatemeh Azarikia; Soleiman Abbasi
Abstract
Introduction: Maillard reaction is a well-known technique for covalent coupling of protein–polysaccharide which is usually used to improve the functional properties of proteins. Conjugation by the dry heating method is occurred during Amadori rearrangement step in the Maillard reaction where amine ...
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Introduction: Maillard reaction is a well-known technique for covalent coupling of protein–polysaccharide which is usually used to improve the functional properties of proteins. Conjugation by the dry heating method is occurred during Amadori rearrangement step in the Maillard reaction where amine groups of the proteins are linked to the reducing end of the polysaccharides. This glycation process leads to the improvement of solubility, foaming and emulsifying properties of proteins (Liu et al., 2012). Protein-based emulsions are sensitive to pH and ionic strength alterations as well as heating and freezing–thawing processes. While, joining proteins to high molecular weight polysaccharides protects them against environmental stresses. A wide range of carbohydrates were already utilized to enhance the emulsifying properties of proteins–polysaccharides namely whey protein isolate–dextran (Akhtar et al., 2003), β-lactoglobulin–dextran (Wooster et al., 2006), sodium caseinate–maltodextrin (O’Regan et al., 2009), deamidated wheat protein–maltodextrin or glucose (Wong et al., 2011), whey protein isolate–pectin (Xu et al., 2012), yolk phosvitin–dextran (Chen et al., 2014), β-lactoglobulin–six-carbon monosaccharides (Cheetangdee et al., 2014), soy protein isolate–soy soluble polysaccharides (Yang et al., 2015), lysozyme–tragacanth (Koshani et al., 2015), and β-lactoglobulin–Persian gum (Golkar et al., 2015). However, based on the existing literature, it seems that conjugation of Iranian native gums and proteins needs to be more attended to show their potential applications. Therefore, in this study, conjugate formation between milk proteins (sodium caseinate and whey protein isolate) and soluble fraction of Iranian native gums (gum tragacanth and Persian gum) was optimized using response surface methodology (RSM) and the resulting conjugates were used in emulsion formulation in order to compare protein capability before and after being attached to the gums.
Materials and methods: Iranian native gums were pulverized and sieved (mesh size < 60) after being prepared from local herbal stores. To obtain protein–polysaccharide conjugates, dry heat treatment was accomplished at 60oC and 79% relative humidity at different protein:polysaccharide ratios and heating times. Free amino group content was determined by the ninhydrin method described by Doi et al. (1981). To measure color changes before and after Maillard reaction, Hunter Lab was used. Besides, possibility of stabilizing oil-in-water emulsions using the conjugates was studied. Emulsions were formed by addition of oil phase (4% w/w) into protein–polysaccharide conjugates solution (0.4% w/w) following by ultrasound treatment (amplitude of 100%, for 4 min). Samples were kept at 4 oC for 30 days after adjusting the pH at 3, 5 and 7 to compare the effect of protein–polysaccharide conjugates on their stability at different protein charges. For optimization of Maillard reaction using RSM (central composite design), protein:polysaccharide ratio and heating time were selected as independent variable and were studied at 5 levels. The dependent variables were the substitution degree of free amino groups and color change.
Results & Discussion: Based on our findings, the decrease of free amino group indicated that NH2 group of amino acids in milk proteins was covalently linked to carbonyl group of the gums. Comparing free amino group reduction of the samples containing soluble fraction of gum tragacanth and Persian gum also showed that Persian gum was more capable of forming covalent linkage with milk proteins than gum tragacanth; probably, due to the lower side branches of Persian, its molecular weight as well as its structural flexibility. Moreover, we believe the higher side branches of attached-tragacanthin molecules might prevent further attachment of protein to the other polysaccharide molecules via steric repulsion. According to the results of color measurement before and after dry Maillard reaction, conjugation led to reduction of L* and increase of a* and b*. In addition, higher heating time and protein:polysaccharide ratio caused progress of Maillard reaction (especially in the case of milk proteins–soluble fraction of Persian gum). Based on our findings, in dry Maillard reaction, the optimum heating time and protein:polysaccharide ratio were 8 days and 1:1.59 for whey protein isolate–soluble fraction of Persian gum, 7 h and 1:2 for sodium caseinate–soluble fraction of Persian gum, 13.64 days and 1:3 for whey protein isolate–soluble fraction of gum tragacanth, and 7.82 h and 1:3 for sodium caseinate–soluble fraction of gum tragacanth, respectively. Besides, the obtained Maillard reaction products did not cause complete stability of emulsions at pHs 3, 5 and 7. Our findings also declared that attachment of polysaccharides to proteins might negatively affect the proteins functionality, as emulsifier, possibly by hindering adsorption of hydrophobic groups of proteins to oil droplets. Furthermore, homogenization process during emulsion preparation using ultrasound could break the formed covalent bonds and polysaccharide structure leading to lower steric repulsion and viscosity.
Mahboubeh Ostadzadeh; Soleiman Abbasi; Mohammad Reza Ehsani
Abstract
Despite the potential of high intensity ultrasound treatment on homogenization of milk and dairy based products, this treatment, under certain conditions, may lead to produce off-odors which can influence its applicability in the food industry. Therefore, in this research, cacao flavored milk (chocolate ...
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Despite the potential of high intensity ultrasound treatment on homogenization of milk and dairy based products, this treatment, under certain conditions, may lead to produce off-odors which can influence its applicability in the food industry. Therefore, in this research, cacao flavored milk (chocolate milk) was treated using ultrasound at various levels of power intensity, exposure time, and treatment temperature. A light microscope equipped by high resolution digital camera was used to evaluate the size distribution of cocoa particles. Finally, the color, flow and viscosity, and sensory characteristics of stabilized samples were determined. According to the findings, increase of power intensity and exposure time led to a significant increase on the degree of homogenization, and subsequently a paramount decrease on the size of cocoa particles. The cocoa particle diameters of chocolate milk which sonicated at 65 ºC were significantly smaller than the other temperatures. Moreover, the stabilized samples showed Newtonian behavior where the viscosity of control was lower than those treated by ultrasonic. With increase of ultrasound power intensity and exposure time, the viscosity of treated samples decreased. In terms of color, the sonicated samples showed higher L* values and the increase of power intensity and exposure time led to a significant increase on L* value. These samples gained lower sensorial scores than control mostly due to their ‘rubbery’ aroma. But, overall acceptance of treated samples had no significant difference against control. The ultrasound is an effective, rapid, and novel technique which can reduce the size of cocoa particles in order to produce stabilized chocolate milk where its color, sensory and rheological properties was very similar to one treated by conventional heat treatment. These findings can open new approaches in terms of its applicability in dairy industry.
Esmaeil Zakipour-Molkabadi; Zohreh Hamidi-Esfahani; Soleiman Abbasi
Abstract
Regarding to economical importance of kiwi fruit, its wastes such as highly ripe or partially dried up fruits can be used to produce more economically valuable products like fruit leather. Therefore, the aim of present study was the effective factor evaluation of kiwi fruit leather production. The samples ...
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Regarding to economical importance of kiwi fruit, its wastes such as highly ripe or partially dried up fruits can be used to produce more economically valuable products like fruit leather. Therefore, the aim of present study was the effective factor evaluation of kiwi fruit leather production. The samples were studied in two groups, raw and cooked fruits which were treated in a boiling water bath. Defined amounts of liquid glucose (10%, 17.5%, and 25% w/w), ascorbic acid (100 mg percent of homogenized fruit) and citric acid (0%, 0.5% and 1% w/w) were added to each group. The samples were then poured in a flat pan with 7 mm thickness and were dried at 70°C in a vacuum drier to reach 14±1% moisture content. This research showed that increasing the percentage of citric acid caused an increase in fruit leather acidity whereas increasing the amount of liquid glucose caused a decrease in it. The ratio of vitamin C in samples from raw fruit was lower than that of its amount in samples prepared from cooked fruit. Furthermore, the amount of browning index in the fruit leather had a significant increase in comparison with the primary mixture before drying. Texture analysis showed that the tensile strength of the selected sample was significantly less than those of in the three other samples which are available in the market. Also, elongation of the selected sample was higher in comparison to the other samples. In the present study, regarding to the three decision variables, the acidity, the browning index and the ratio of vitamin C, six appropriate samples were selected for sensory evaluation and the most suitable sample was the sample obtained from cooked kiwi fruit which contained 25% and 0.5% of liquid glucose and citric acid, respectively.
Keywords: Kiwi fruit leather, Browning index, Vitamin C, Sensory evaluation
Soleiman Abbasi; Zohreh Hamidi-Esfahani
Abstract
Dehydration, as one of the practical ways to increase the shelf-life and applicability of yoghurt in various foodstuffs, is normally done by freeze drier (FD) which is an expensive and time-consuming process. For these reasons, in the present study the capability of microwave–vacuum drier (MVD), as ...
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Dehydration, as one of the practical ways to increase the shelf-life and applicability of yoghurt in various foodstuffs, is normally done by freeze drier (FD) which is an expensive and time-consuming process. For these reasons, in the present study the capability of microwave–vacuum drier (MVD), as an alternative process, was investigated. For doing so, the fat free yoghurt samples of 2.2, 4.2 and 6.2 mm were dehydrated under various combination of absolute pressures (60, 200, 400, 600, and 800 mbar) and microwave powers (35,130, and 260 W) using a lab scale drier designed in our lab. Based on our findings, the drying time of yoghurt in microwave–vacuum drier for thickness of 2.2 mm was considerably (80%) shorter than commercial freeze-drier. In addition, the dependency of the drying time to absolute pressure was much less than microwave power and yoghurt thickness. Furthermore, except the color and bulk density, the rest of the qualitative parameters of yoghurt powders dehydrated by MVD and FD methods were almost similar. It should be noted that the highest resemblance in terms of quality and color indices between FD and MVD powders was seen at combination of low microwave power and low absolute pressure (35 W, 60 mbar). All in all, the findings of this study showed the capability of MVD for production of yoghurt and other food powders and this technique can be introduced as a potential alternative for FD.
Keywords: Yoghurt, Shelf-life, Microwave, Drying, Quality
