جستجوی مقالات مرتبط با کلیدواژه "ویسکوالاستیک" در نشریات گروه "صنایع غذایی"

Food gums are a class of food additives playing various roles, such as thickening, gelling and stabilizing of the food aqueous solutions. The aim of this study was to investigation rheological properties of protein-free Balangu seed gum. For this purpose, balangu seed gum was prepared and after its enzymatic hydrolysis, protein-free Balangu was prepared and the rheological properties of balangu seed gum and protein-free balangu seed gum were evaluated in terms of different parameters such as intrinsic viscosity, steady shear flow properties (shear dependence and time dependence tests) and dynamic rehology properties (stress sweep and frequency sweep tests). The results showed that balangu and protein-free balangu seed gums at 1% w/w had shear-thinning and weak gel-like behavior, and indicated the random coil conformation in dilute region. Considering correlation coefficient (0.998), the Herschel–Bulkley model was selected to describe the rheological behavior of Balangu and protein-free balangu seed gum solutions. In the time-dependent test, the balangu and protein-free balangu seed gums showed same ability to create the structure and the amount of thixotropy. The results of dynamic rheological test showed the storage modulus curve was located higher than the loss modulus in the linear region, indicating semi-gel or semi-solid behavior in Balangu and protein-free balangu seed gum. Hydrolysis and decreasing protein content did not significantly affect viscoelastic behavior of balangu seed gum

Yogurt is popular because of its high levels of calcium, vitamins, minerals and low levels of fat, as well as its health-promoting effects and inhibiting harmful bacteria and helping to prolong life. Pumpkin is a good source of β-carotene, water-soluble vitamins and amino acids. In this study, syneresis, pH, acidity and rheological properties of yogurt (1.5% fat) containing 0, 2.5, 5 and 7.5% pumpkin powder were investigated. The results showed that the highest amount of acidity (74° Dornic) was related to the control sample. The results showed that by adding 2.5% pumpkin powder to the control sample, the strength of the formed gel decreased and with increasing concentration up to 7.5%, this property was increased. In the study of the viscoelastic behavior of the samples, it was found that by adding a concentration of 2.5% powder to the control sample, the ratio of viscous to elastic component increases, but with further increase in concentration, this ratio remains almost the same and therefore the viscoelastic behavior remains balanced. The values of loss tangent in the viscoelastic region for the control sample, 2.5%, 5% and 7.5%, were 0.173, 0.308, 0.317 and 0.319, respectively. Therefore, with greater structural cohesion, the consumer feels the same flexibility of the gel regardless of the gel concentration. Also, in all samples, in the whole frequency range, the elastic behavior prevailed over the viscous behavior, which increased by adding 2.5% powder to the control sample, the type of gel structure (b) increased, and the strength of the structure (a) decreased. This means that the yogurt gel becomes weaker and with increasing concentration of the powder, b decreases and a increases; Therefore, the strength of our structure increases.

Gums are long chain polysaccharides components with high molecular weight wildly used in the food and many other industries as stabilizer, texture modifier, gelling agent, thickener and emulsifier. The aim of this study was to investigation evaluation of physicochemical and emulsifying properties of protein-free balangu seed (Lallemantia royleana) gum. The results showed, balangu and protein-free balangu were obtained from molecular weight 3120 and 3360 kDa, respectively. Major functional groups were identified from FTIR spectrum of balangu and protein-free balangu, include O-H, C-H, C=O, -COO-, and C-O-C. The results of GC-MS showed that the major monosaccharides specified in Glucose, Galactose, Arabinose, Xylose and Rhamnose. According to the rheological protein-free balangu had the lowest protein content and this led to formation of large oil droplet size and lower emulsion stability. The parameters of Herschel–Bulkley model were showed, the values of coefficients of determinations (R2) were near to 1 and Root Mean Square Error (RMSE) values were lower than 0.4, which indicate the suitability of this model to describe the flow behaviour of samples. Moreover all emulsions represented flow behaviour index values less than 1, which reveals shear thinning behaviour of emulsions, but no significant difference was found between emulsions (p>0.05). On amplitude sweep test, the storage modulus values were greater than loss modulus values in all emulsions, which indicates their elastic behaviour. On frequency sweep test, the storage modulus values were greater than loss modulus values in all emulsions, which confirmed solid like behavior. The indices of power law’s storage modulus balangu and protein-free balangu emulsions had near to zero which reflect high elastic behaviour of emulsion.

Packaging films are one of the common ways to maintain the quality of food and agricultural products. The effect of PVC and HDPE packaging films, storage and temperature on some mechanical properties, including: the firmness force, yield strain, energy of rupture and modulus of elasticity and also, the viscoelastic behavior of the strawberry fruit was investigated. The mechanical test and relaxation test were done using a texture analyzer. In this study, the stress versus time graph was plotted and three-component Maxwell model coefficients were obtained. According to the results of this study, the use of these films had a positive impact on the yield strain. On the other hand, products in the packaging films were able to store products until the 40th day. In this study, the firmness force of HDPE packaging fruits in 4℃ and 20℃ from 2.17 to 1.10 N, 2.16 to 1.85 N, decrease respectively, during storage. The results show that Maxwell model (RMSE<0.6818 and R2 >0.9158) fits the experimental data. Also, with a retention time, the elastic component of the model is relatively reduced and the application of the packaging prevents the decrease in relaxation time.

Ketchup sauce is a favorite product and it is useful for flavor and color improvement of foods. Addition of hydrocolloids to ketchup sauce in order to physicochemical, rheological, textural improvement and to understand rheological behavior such as viscoelastic properties is important for quality control, process designing, storage condition and textural properties. So, the objective of this research is investigating effect of Xanthan gum and Ispharzeh and Basil seeds mucilage on the viscoelastic behavior of ketchup sauce.
at present study, treatments were determined based on combination of hydrocolloids (0-1%) by mixture statistical design of design expert software 9. For investigating viscoelastic properties of samples, strain sweep (at 0.01-1000%) and frequency sweep (at 0.01-100 Hz) test was done. The best model for test results was fitted and effects of each parameter were determined.
the results of oscillating strain sweep showed that at low and moderate strain, all of samples had linear viscoelastic behavior. In terms of crossover, the highest crossover was seen at sample K1 (0.5% xanthan gum, 0.5% basil seed mucilage) and the lowest of that was seen at samples k9 (0.16% xanthan, 0.66% ispharzeh seed mucilage, 0.16% basil seed mucilage) and K10 (0.5% xanthan and 0.5% ispharzeh seed mucilage). The finding of oscillating frequency sweep showed that storage moduli were higher than loss moduli at all samples. Loss tangent lower than 1 revealed solid viscoelastic of samples. The highest and the lowest of storage moduli, loss moduli and complex viscosity belonged to K4(1%basil seed mucilage) and k10 (0.5% xanthan and 0.5% Ispharzeh seed mucilage) respectively. Except crossover, added hydrocolloids had significant effect on the all parameter in ketchup sauce.
oscillating rheological measurements is a useful method to determine effect of hydrocolloids addition to food systems. Using strain sweep and frequency sweep test, it is possible to investigate flow capability and structure maintenance capability at storage condition. It was concluded that regarding unique functional properties of Ispharzeh and Basil seeds mucilage, they could use as a commercial hydrocolloid accompanied by other hydrocolloids.
Using strain sweep and frequency sweep test, it is possible to investigate flow capability and structure maintenance capability at storage condition. It was concluded that regarding unique functional properties of Ispharzeh and Basil seeds mucilage, they could use as a commercial hydrocolloid accompanied by other hydrocolloids.
Using strain sweep and frequency sweep test, it is possible to investigate flow capability and structure maintenance capability at storage condition. It was concluded that regarding unique functional properties of Ispharzeh and Basil seeds mucilage, they could use as a commercial hydrocolloid accompanied by other hydrocolloids.

In this study، dynamic rheological، structural and thermal properties of Alyssum homolocarpum seed gum (AHSG) were investigated as a function of concentration (1. 5، 2، 2. 5 and 3% w/v) and temperature (5–85 °C). The effects of heating/cooling rate on the rheology of AHSGs were studied using small amplitude dynamic oscillatory shear (SAOS). The LVE of this gum were observed at more than 1% strain. The elastic component was always higher than the viscous one. Mechanical spectra of these gum solutions were obtained by frequency sweep measurement classified into that of weak gels because G’ was larger than G” throughout the tested frequency range. The complex modulus has linear relationship with the frequency. The gums showed dependency behaviour as a function of temperature in the range of 5-85oC. The moduli were dependent on gum concentration. They were shown that strength of AHSG at cooling step was more than heating step. AHSG at concentrations above 2. 5% was formed gel and its gel was irreversible. Gel formation temperature increased with increasing concentration. FT-IR spectra to understanding their functional groups were recorded in the transmittance mode.

Stress relaxation is one of the defined tests to characterize the viscoelasticproperties of agricultural materials. Stress relaxation data are very importantbecause they provide useful and valuable information such as fruit firmness andripening, food processing and predicting changes in the material during mechanicalloading. Viscoelastic behavior of pomegranate that is cultivated in Iran has beenstudied in current research. For this purpose, stress relaxation test was conductedwith Ardestani cultivar of pomegranate for three sizes (small, medium and large)and three different harvesting times. Two common models (the GeneralizedMaxwell model and the Peleg model) were fitted to the experimental data. ForMaxwell model coefficients, values for RMSE, R2 and MAPE less than 0.003,greater than 0.98 and less than 0.385 were obtained respectively. The value ofMAPE has been acquired for all harvesting times and pomegranate sizes except forpomegranate with medium size in first harvesting time. Results showed thatMaxwell model describes the tension relaxation behavior of pomegranate withlower error than Peleg model in a suitable way. The ability of artificial neuralnetworks technique as an alternative to predict the viscoelastic behavior ofpomegranate was assessed. This assessment showed that artificial neural networksand Maxwell model can predict the tension more reliably and more precisely thanPeleg model. According to analysis of tension data using models coefficients,pomegranate behaves like solid viscoelastic in every harvesting stage. It also showsthat elastic behavior of pomegranate is more in the third stage of harvesting thanfirst and second stages.