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 ...
Read More
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.
Liela Mahsouli; Hannan Lashkari
Abstract
Introduction: Milk-based dessert is one of the dairy products which in addition to the nutritional value, makes a variety in the consumer basket of goods. The most important property of desserts is their high energy and a pleasant feeling that is created by the consumer due to its ingredients. These ...
Read More
Introduction: Milk-based dessert is one of the dairy products which in addition to the nutritional value, makes a variety in the consumer basket of goods. The most important property of desserts is their high energy and a pleasant feeling that is created by the consumer due to its ingredients. These products contain mainly milk, thickeners, sugar, flavoring compounds and colorant, and have a jelly structure. Sugar is used as a sweetener in the production of desserts. The grape juice concentrate is one of the traditional products of Iran's grapevine region, which accounts for about 5 to 20 percent of Iranian grapes used to make grape juice concentrate. Grape juice concentrate contains high levels of natural sugars, minerals, vitamins, organic acids and antioxidants. Therefore, grape juice concentrate can be used as a sugar replacer sweetener. Materials and Methods: In order to reduce the amount of sucrose in dessert and its replacement with grape juice concentrate, different ratio of grape juice concentrate (0, 5, 7.5 and 10%) were used. To prepare dessert samples, wheat starch was first added to milk at 4%w/w, and then 0.5%w/w gelatin and sugar were added and mixed until all ingredients were completely dissolved in the milk. Then, it was heated to 95°C and stirred at 270 rpm for 15 minutes, then cooled to 40 °C, and grape juice concentrate and water were added. The mixture was finally filled into the dishes. Samples were subjected to physicochemical, microbial and sensory evaluation after 48 hours of storage at 4 °Ċ. The AOAC (2000) methods were used for measuring the moisture content and fat. The amount of carbohydrate, acidity, and pH were calculated based on method of Ebrahimi et al (2018). To measure the free radicals inhibition by DPPH, method Kamkar (2009) was followed. The color analysis was performed based on the method of Hosseini et al (2019). The parameters of color include L* (lightness), a* (redness) and b* (yellowness) were measured. Texture parameters include hardness (N), cohesiveness, springiness (cm), gumminess (N), chewiness (N.cm), adhesiveness were determined by texture analyzer as described by AOAC (2000). The sensory attributes were evaluated by 15 panelists. A five-point hedonic scale rating (1= very bad, 2=bad, 3= neither bad nor good, 4= good, 5= very good) was carried out. Data analyzed with SPSS software and means were compared with Duncan multiple range test. Results and discussion: The results showed that the increase in the amount of grape juice concentrate in dessert samples caused a significant (p< 0.05) increase in acidity, hardness, total solid, a*, and b* value, and percentage antioxidant activity and a significant (p<0.05) decrease in fat, sucrose, pH and L* index. Grape juice concentrate has no significant (p˃0.05) effect on the texture indexes, total count, mold and yeast. The results of microbial tests showed that the total bacterial count increased in samples of grape juice compared to control (p <0.05) but mold and yeast counts were not significantly different in dessert dairy samples (p˃0.05). It should be noted that the microbial count of the samples is in accordance with the standard dairy dessert No. 14725. Sensory evaluation indicated that the addition of grape juice concentrate in the dessert samples did not have any significant effect on the textural characteristics but increased the score of other sensory factors. The sample containing 10% of grape concentrate juice obtained the highest score in odor, sweetness, color, and acceptance, and since its other characteristics were standard, it was selected as the best treatment.
