Iranian Food Science and Technology Research Journal
Year:2010 | Volume:6 | Issue:3|Papers Count:14

In this study, ultrafiltrated Feta cheese was prepared from cow’s milk ultrafiltraton retentate and soymilk blend. Rennet and calcium chloride were used simultaneously as coagulant to coagulate cow’s milk proteins and soymilk proteins, respectively. Then, the effect of storage period on physical (Texture Profile Analysis test, Penetration test), chemical (total solids, protein, fat) and sensory (flavor, texture) properties of samples was investigated in 3, 20, 40 and 60 days after production. The results showed that during storage period physical properties decreased for both Texture Profile Analysis test and Penetration test. But, sensory and chemical characteristics of the product during storage did not significantly change, the way that the flavor and texture scores of the last day were still higher than the middle and the product after two months storage well was usable.

Edible coating can provide effective protection for fresh fruits. In the present paper we use an edible coating based on whey protein concentrate (WPC) and four different levels of rice bran oil (0, 0.2, 0.4, and 0.6 g/100ml) to maintain the quality of kiwifruit (A. deliciosa). We have tested and compared the following postharvest storage quality conditions of coated groups and a control group in four subsequent weeks: weight loss, color parameters (L*, a*, b*), texture changes, titratable acidity, soluble solids content, and sensory attributes. Coating application reduced the weight loss in kiwifruits. Our results indicate also a significant difference in the soluble solids content and a non-significant difference in titratable acidity between the control and coated kiwifruits after 4 weeks of storage at 8oC. Moreover, our results show that kiwifruits coated with whey protein concentrate-based coatings had higher L*, and lower a* than the uncoated kiwifruits. Our coated kiwifruits received higher scores than the control samples in sensory evaluations. Coating reduced texture loss up to 5% with respect to the control samples depending on the rice bran oil contents.

Silver carp is the major specimen in warm water fish culture system in Iran which is presented in various size and different price. The present study was aimed to compare nutritional value and to investigate proportion of nutritional value and financial of various weight groups of silver carp in spring season. For this purpose silver carp was prepared in market sizes and their dry matter, fat, protein and ash content and fillet yield were determined and the indices of proportion of nutritional value and financial (NP) and justified price difference based on dry matter content (PDdm) were calculate for weight groups. According to obtained results, the more heavy weights of silver carp contain lower moisture but higher fat and energy (p<0.01). But their protein and ash content were similar (p>0.05). Light weight group has a higher (p<0.01) NP indices rather than medium and heavy weight groups for dry matter, protein, ash and energy. NP indices were same in medium and heavy weight groups for all nutritional components (p>0.05), except fat (p<0.05). With regarded to these results, light weight has a better nutritional proportion than medium and heavy weights and the light weight is advised fir buying until that the price difference between light weight and two other one be more than calculated PDdm indices for them. But when the choosing be between medium and heavy groups, both of them have a nutritional value proportionate with their prices.

Inulin is widely used in functional foods throughout the world for its health-promoting and technological properties. Helianthus tuberosus is cultivated widely in the northern part of Iran. Helianthus tuberosus can be a valuable source of Inulin. To optimize conventional extraction of Inulin, various combinations of time, temperature, and solvent: solid ratio, were used. In this research, a series of statistically designed studies were performed to investigate the effect of each of the independent variables (temperature and pH of extraction medium, extraction time, and solvent: solid ratio). The following variables: solvent: solid ratio (5-12 v/w), temperature (40-90oC) and time (5-40 min) were studied. The central composite design (CCD) and response surface methodology (RSM) were employed as experimental design and statistical analysis. Based on canonical analysis, the optimal conditions for maximizing Inulin extraction yield (42.2%) were 76.64oC for 23.90 min and solvent: solid ratios of 12:1 (v/w).

In this study, chemical composition and functional properties of red bean, chickpea, lentil and canellini bean were evaluated. Our results revealed that chickpea had the highest protein (43.4%) and fat (5.17%) content and lentil, red bean and canellini bean were the following ones. The isoelectric point of all the samples were determined as about pH=4 but other than lentil, the remaining samples had a second isoelectric point. Red bean flour had the maximum water holding capacity (146.15%) and the influence of pH and ionic strength on the samples were similat in terms of water holding capacity. An increase in salt concentration led to a decrease in water holding capacity. Regarding oil absorption capacity, red bean flour had the highest capacity (92.1%) and lentil flour had the lowest one (80.45%).

The effect of pre-treatments in combination with hot air, vacuum and hot-a microwave drying methods the progress of the drying process, and textural, and colour and rehydration rate on button mushroom (Agaricus bisporus) slices were investigated. In this work, one of the following methods: hot air, vacuum drying or microwave-assisted convective drying and also different pre-drying treatments, viz. blanching (with hot water or vapour) and sulphitation, were applied. Textural properties of button mushroom were measured during drying and rehydration using a texture analyser. The colour changes of samples during drying and rehydration were analysed applying a Hunterlab Colorimeter. During drying, hardness of mushrooms was increased. Sulphitation pre-treatment improved the structural and rehydration rate of the dried samples, but had varying effects on the colour. Microwave energy reduced drying time and can modify the structure, colour and texture strength of the final product. The effect of microwave treatment on colour varied with the type of pre-treatment applied before drying. Microwave samples showed also the highest rate of rehydration among all samples.

In the present research work, influence of fleawort (Plantago ovate L.) seed hydrocolloid at three concentration level (0.1, 0.15 and 0.2%) was investigated on physicochemical, textural and sensory characteristics of low fat yoghurt. The treated yoghurt samples were compared with a positive (3% fat) and negative (0.2%) co trol sample after 1, 7 and 15 days of storage. Fleawort seed hydrocolloid did not change the pH and titrable acidity of samples, significantly (p<0.05). Synersis of all treated yoghurt samples was less than that of control samples. More over synersis was decreased through the storage period, so that the minimum level was observed in the day 15, which belonged to the sample containing 0.2% of hydrocolloid. Viscosity of treated samples was higher than that control samples. Viscosity of sample was increased dramatically through the storage period, so that the highest viscosity belonged to the yoghurt containing 0.2% hydrocolloid in the day 15. It was concluded that the fleawort seed hydrocolloid is suitable to be used as a fat mimetic in yoghurt formulation.

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.

Soy flour is the least processed form of soy protein products which has become increasingly popular in food technology for its nutritional benefits, low cost and good functional properties. The aim of this study was to investigate functional properties of soy flours produced by four different industrial processes: defatted, defatted and toasted, low fat, and full fat soy flours. Because of different production procedure and degrees of heat treatment, soy flours had significant differences in protein dispersibilities (which determine the amount of residual trypsin inhibitors and use of the final products) and fat contents which affected on other functionalities. Soy flours with lower protein dispersibility indices (PDI) had lower foaming properties (capacity and stability), emulsification (activity and stability), water holding and fat binding capacities, and solid dispersibility indices. Comparison of low fat and full fat soy flour showed that fat content result in reduced functionalities such as water holding and fat binding capacities, emulsification stability, and solid dispersibility. Negative effects of fat content increase on functional properties are equal or more than PDI.

The main purpose of present paper is the modeling of onion drying process and investigation of experimental data of onion drying obtained with using a hot air dryer. therefore some empirical and regression models have been considered to fit experimental data. The investigation of the experimental data shows the onion drying happens only in falling rate zone. The experimental data have been fitted with 12 emprical models and 74 regression models. The results showed that at 60, 70, 80 and 90, “Midilli-Kucuk” model is the best model. The results obtaine from regression model shows that the best model is 10th order polynomial. Overall, it can be concluded the best polynomial model is slightly better than the best empirical model.