JOURNAL OF FOOD RESEARCH (UNIVERSITY OF TABRIZ)
Year:2014 | Volume:24 | Issue:2|Papers Count:12

In this research, sour orange juice concentrate was produced using a vacuum evaporator at pressure of 55 mm Hg and evaporation temperatures of 50-80oC. Rheological properties of the sour orange concentrates were evaluated under different conditions of total soluble solid (30-50oB) and temperature (5-55oC) at shear rate range of 0-160 s-1. Viscosity of sour orange concentrates decreased with shear rate and a non-Newtonian behavior was observed. Consistency index decreased with temperature and increased with total soluble solid. Moreover, vitamin C content of the samples before and after evaporation at 50 or 80 C was determined using HPLC. The results indicated that with increasing evaporation temperature the vitamin C loss increased (P<0.05). The lightness of the concentrates was evaluated as a function of evaporation temperature and final concentration. The results showed that the lightness of sour orange concentrate was affected by temperature and time of concentration (P<0.05). However, the sour orange drink prepared from the samples concentrate at 70°C and fresh sour orange was evaluated to be better in the case of flavor and taste, sensory evaluation of the sour orange drinks prepared from the concentrate or fresh sour orange juice did not show any significant differences.

Tarkhineh is one of the traditional products of western part of Iran. This study was carried out in order to obtain more information on drying behavior of Tarkhineh and find ways to improve drying condition. The influence of wheat cooking time (0, 1 and 3.5 hours), drying temperature (70, 80 and 90oC), drying time (from 30 to 900 minutes) and bulgur particle size (fine, medium, coarse) on drying behavior of Tarkhineh were studied. Different mathematical models were applied to explain the drying behavior of Tarkhineh. Color changes of Tarkhineh were determined by Image J software. At the beginning of the drying process, the L* decreased while b* increased rapidly, however both reached a relative stable amount subsequently. a* slightly decreased initially but depending on the type of sample either increased or remained constant then. The results indicated that at 70 °C, the Logarithmic model presented better predictions for modeling of mass (moisture) transfer than for ultra cooked samples but for raw and cooked samples, the Two-term model were appropriate. At 80 and 90oC, the Two-term model was the best descriptive for ultra cooked samples but for raw and cooked samples, the Midilli-Kucuk model was appropriate. Mentioned variables had major effect on the drying behavior of Tarkhineh. For increasing the production rate and improving the color of Tarkhineh, cooking of wheat for one hour and drying at 80oC can be recommended.

Cress seed gum hydrocolloid choosed as a new source of stabilizer and used in ice cream formulation. Ice cream samples produced with 0, 0.1%, 0.2%, 0.3% and 0.4 % gum. Rheological properties were evaluated by using rotational viscometer and textural attributes measured using texture profile analysis instrument. Results revealed that all ice cream samples showed a non-newtonian specifically pseudoplastic behavior. Power law model was completely suitable for describing flow behavior of ice cream samples and increase in gum concentration was accompanied by decrease in flow behavior index and consistency coefficient that is an index of viscosity nature of food material. Increase in storage time lead to increase in hardness of samples textures but adhesiveness of samples decreased by gum increasing in comparison with blank sample. This research showed that we can use cress seed gum hydrocolloid as a stabilizer in ice cream.

Bread is one of the most important food products that should have necessary nutritional properties and value. In this research, effect of brown rice flour (in levels of 5, 10 and 15%) with adding of mono and diglyceride emulsifier (in levels of 0.5 and 1%) was studied on some of qualitative properties of Sangak bread. Based on the results, the highest volume of bread was for control and the lowest was for B1 (having 5% brown rice flour and 0.5 % mono and diglyceride emulsifier). Also control treatment had the highest and B1 had the lowest amount of moisture. On the other hand, B6 (having 15% brown rice flour and 1% mono and diglyceride emulsifier) had the highest and control had the lowest amounts of ash, fiber and fat, respectively. Control and B4 (having 5% brown rice flour and 1% mono and diglyceride emulsifier) had the highest and B3 (having 15% brown rice flour and 0.5% mono and diglyceride emulsifier) and B6 had the lowest amounts of protein. Based on the results of organoleptic properties, all of considered characteristics except of chewing ability, smell and taste, B6 treatment was satisfying than control. Staling results based on sensory method showed that 24 hour after cooking, there were not any significant difference between samples of Sangak bread including brown rice flour and mono and diglyceride emulsifier but 48 and 72 hours after cooking, B6 was the most fresh one and the lowest freshness related to control. In measuring by Instron and 24 hour after cooking, the highest and the lowest staling was measured in control and B3, respectively. But 48 and 72 hours after cooking, the highest and the lowest staling were in control and B6.

UF cheese ripens more slowly than the traditional cheeses, because of high contents of whey proteins. The addition of enzymes has been recommended by some corporations to accelerate the ripening of UF cheeses, but it has not yet been included for the production of Iranian UF Feta cheese. The influence of microbial protease and lipase on the acceleration of flavor development of ultra-filtered Feta cheese was assessed. Enzymes of Lactococcus plantarum extracted via ultrasound as protease and Rizomoccur mehei lipase was used as lipase. Enzymes were added to cheese samples in two different concentrations: 0.12 g/lit and 0.24 g/lit of lipase and 2.5 ml/lit and 5 ml/lit protease. Physicochemical properties of samples were analyzed in days 15, 30, 45 and 60 of cheese ripening. Evaluation of proteolysis process was performed by measuring percentage of soluble nitrogen at pH=4.6 and urea polyacrylamide gel electrophoresis. The results showed that in all samples, ripening time and enzyme concentration significantly (P<0.05) increased the acidity, dry matter, lipolysis index and soluble nitrogen percentage at pH=4.6. These findings proved the effect of applied enzymes in lipolysis and proteolysis process. Descriptive sensory analysis based on cheese flavor intensity that was performed with ten panelists, showed that control samples had the highest total score.

In the present study, response surface methodology was used to optimize hydrolysis conditions of protein hydrolysate from the sheep visceral (stomach, intestine), using Alcalase 2.4l. The investigated factors were temperature (43-52oC), time (65-190 min) and enzyme/substrate ratio (50-95 AU/Kg protein) to achieve maximum degree of hydrolysis and recovery of nitrogen. Experiments were designed according to the central composite design. Each of the studied variables had a significant effect on responses (p<0.01). The optimal conditions to achieve the highest degree of hydrolysis and recovery of nitrogenwere, temperature (47.17, 47.56oC), time (158.74, 153.38 min), and enzyme/ substrate ratio (78.60, 76.03 AU/Kg protein), respectively. Under these conditions, hydrolysis degree, nitrogen recovery were 36.3%, 72.67%, respectively. Regression coefficient for each of the models (Quadratic type) for degree of hydrolysis, recovery of nitrogen were, 0.988, 0.986, respectively. The values indicated the high accuracy of the model to predict the reaction conditions considering different variables. The chemical analysis of protein hydrolysate showed high protein content (83.78%) and low fat content (0.34%).

In this study, the effects of xanthan gum on shelf life of Sangak bread were investigated. The gum was added to the formulation at 0.5 and 1%) w/w) concentration. As a control, no gum added formulations were used. Wheat bread samples were packaged in polyamid/ polyethylene bags with different gas combinations. Two gas concentrations tested included: air (control), and 100% CO2. All packaged bread samples were stored at 25oC for 15 days. During storage, quality and microbial features of bread such as moisture, texture, density, mold and yeast count were assessed at intervals of three days. Statistical analysis of the results of Sangak bread quality characteristics during storage revealed that, the gas in headspace of package did not significantly affect the product density and moisture content, while shear stress, maximum force and the microbial load of the samples were thoroughly impressed by the atmosphere of the package. So that with carbon dioxide, the growth of mold and yeast was more limited. Also was observed all product quality characteristics changes significantly during storage time. So that the reduced moisture and density were observed up to 12th day. Conversely hardness, shear stress and microbial load increased during the storage period. The breads containing 1% xanthan showed the lowest maximum force, shear stress and the microbial load and the highest moisture all over the storage period. Bread samples containing xanthan gum at 0.5% level showed the highest density during their storage time. In bread packaged with 100% CO2, the lowest slope of the maximum force curve and shear stress versus storage time were recorded by treatment having 1% xanthan.

Machine Vision is one of the useful technology in food and agricultural industry. This technology is commodious tool for rapid evaluation of food material quality. In this research, using a digital camera, a PC and an Image J graphical software, a simple and low cost method for the evaluation of color of potato during frying is introduced. Analysis of digital pictures of the surface of samples can give L, a, b Hunter color parameters and color distribution. Efficacy of temperature and time in frying process on potato chips color change were evaluated. Frying of potato chips in temperatures (140, 150, 160 and 170oC) and times (120, 180 and 240 second) was investigated. Color changes of the fried samples were evaluated by analyzing the digital pictures of the samples and showed that increasing of temperature and time caused a systematic increase of a, b and reduction of L values.

This research was aimed to study the effect of basil seed mucilage as a fat replacer on physicochemical, rheological, textural, and sensory properties of low fat (LF) mayonnaise. Fat was partially substituted by basil seed mucilage at levels of 20%, 30%, 40% and 50%, and samples were referred as R-20, R-30, R-40 and R-50, respectively. The full fat (FF) mayonnaise (75% oil) without basil seed mucilage was used as a control. Results indicated that estimated calorie of all LF mayonnaise samples was significantly lower than that of control. However LF mayonnaise sample had higher moisture content than their FF counterpart. In terms of textural properties, the highest values for firmness and adhesiveness belonged to R-30 sample. Results of rheological characteristics showed that all samples exhibited shear thinning behavior. R-30 sample had the highest score for overall acceptability. It was concluded that basil seed mucilage has the potential to use as a fat replacer in mayonnaise.

In order to investigate of cross-linking of milk and soy proteins by transglutaminase and its influence on physicochemical properties of nonfat yoghurt and 4 treatments including (control, Soy Protein Isolate (SPI) enriched, Enzyme treated and SPI enriched with enzyme treated) were prepared from reconstituted milk. Decreasing of protein bands intense in electrophoretic patterns of yoghurt samples SPI enriched with enzyme treated in contrast to samples of SPI enriched improved the cross-linking of soy and milk proteins by transglutaminase and formation of high molecular polymers. In the beginning of storage time, the pH values for enzyme treated sample was lower than control while during storage period, the influence of SPI on pH variations was significant (P<0.05).The sample with SPI enrichment increased acidity value but the effect of enzyme on acidity was not significant (P<0.05). At the first day of storage period, the highest content of WHC was obtained for enzyme treated samples but during storage time, the sample containing SPI showed more effect on WHC enhancement. The SPI enriched with enzyme had maximum WHC in whole storage time (P<0.05). The sample with SPI enrichment caused higher viscosity (P<0.05). The presence of SPI resulted in a sponge like structure in enriched samples; SPI enriched with enzyme treated samples caused a structure with a more homogeneous porosity and smaller particles.

For determination of functional properties and application possibility of Iranian local plants hydrocolloids, the carboxy methyl cellulose (CMC) replaced with tragacanth (T) at levels of 0, 25, 50, 75 and 100 percent and quality characteristics of ice cream (IC) were determined. The results showed that the sample containing 100% T had lower specific gravity (SG) than other samples but by decreasing the level of substitution, the SG of IC mix significantly increased. All levels of substitution led to significant increase of overrun. Sample containing 100% T showed higher viscosity than sample containing mixture of gums, and control sample had the highest resistance to melting. Sample containing 75% CMC and 25% T had the lowest hardness and sample containing 100% T had the highest hardness. Increasing the level of substitution led to improve the sensory properties of IC. According to the results of the physical properties and sensory scores of IC samples obtained from this research, replacement of CMC and T at level of 100% is possible.

Imitation pizza cheese provides a useful model system to examine starch–casein interactions from a rheological perspective. Increasing starch content may be a practical and cost-effective means to control the functional properties of imitation pizza cheese. Imitation cheeses containing 2, 3 and 5% (w/w) modified potato starch as a partial caseinate substitute were manufactured and dynamic rheology of these products were compared to a control (0% w/w starch) in temperature sweep analysis. The dynamic rheological properties of caseinate-based imitation cheeses containing various concentrations of modified potato starch were investigated using a strain-controlled rheometer. The storage modulus (G’), the loss modulus (G”) and the loss angle (Tan d) were measured as a function of temperature (35-100oC). The storage modulus and loss modulus of imitation cheeses was significantly increased (P≤0.05) at all examined temperatures (35-100oC) with the inclusion of modified potato starch. Inclusion of starch significantly reduced imitation cheese peak Tan𝛿 values compared to control (P≤0.05), and the inclusion of 5% (w/w) starch as a partial caseinate substitute had the greatest effect. In sensory evaluation, in terms of texture and mouthfeel, the highest score belonged to control, while in all of samples lowest score observed in sample containing 5% w/w starch. The results of this study showed that varying the level of modified potato starch altered dynamic rheological properties as a function of temperature and thus the functionality (for example, meltability), as well as sensory attributes of imitation pizza cheeses.