فهرست مطالب
فصلنامه پژوهش های صنایع غذایی
سال بیست و دوم شماره 4 (زمستان 1391)
- تاریخ انتشار: 1391/12/20
- تعداد عناوین: 12
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Page 361Since acetylation mainly increases the hydrophobicity of gluten, it is used as a common method to increase certain functional properties of the gluten. Some components exist in a food system can also affect the properties of the gluten and its derivatives. With the aim of studying the effects of common salt (NaCl) on the characteristics of native and acetylated gluten, in this research NaCl in concentrations of 0.0, 0.2, 0.4 and 0.6 mol/L was added to the protein suspensions at neutral condition. Some of the functional properties of the native and acetylated gluten including solubility, water absorption, water holding capacity, emulsifying activity, emulsifying stability and foaming capacity and stability were studied. The results showed that the water solubility, water holding capacity and water absorption of the acetylated gluten were higher than those of the native gluten only at salt levels less than 0.2 M. Similar effects were observed for emulsifying activity, emulsion stability and foam ability of the samples. The results of this study indicated that the presence of salt in the system could differently influence the functional properties of the native and acetylated gluten and determine their food applications.Keywords: Gluten, Acetylation, Functional properties, NaCl
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Page 373In this study, oxidation kinetic parameters of soybean oil affected by three different concentrations of gallic acid antioxidants (100, 200 and 300 ppm) in comparison with a blank sample were studied by rancimat in three different temperatures 383, 403 and 423 k. Factors calculated in this study were temperature coefficient (Tcoeff), special constant reaction (A), activation nergy (Ea), enthalpy (ΔH++) and entropy (ΔS++). They were estimated based on the Arrhenius, Vant Hoff and the Eyrings equations. Generally, reaction constant of oxidation increased with the rise of temperature, and there was a logarithmic relationship between them. Stability of the oil was also increased by the increase of the antioxidant concentration. The results indicated that there was a significant difference among the temperature coefficient, enthalpy, activation energy and special constant reaction values in the blank sample and samples with antioxidant. No difference was observed between samples with 200 and 300 ppm antioxidant. Concerning the entropy, there was a difference between the blank sample and samples with antioxidant, and a high correlation was observed among the regression relations (0.9479
Keywords: Oxidation kinetic, Soybean oil, Gallic acid, Rancimat
In this study, response surface methodology was used to optimize the osmotic-ultrasonic drying condition to achieve maximum water loss, phenolic compounds and minimum solid gain and %EC50. Temperature (40, 50 and 60), processing time (4, 7 and 10h), sucrose syrup concentration (40, 50 and 60% v/w) and frequency (0, 35 and 130 KHz) were the investigated factors influencing kumquat properties during the osmotic-ultrasonic drying. The liquid medium to fruit ratio was 10:1 (weight basis). Experiments were designed according to the central composite rotatable design. Results showed that the linear effects of temperature, processing time, sucrose syrup concentration and frequency on water loss, solid gain, phenolic compound and EC50 were statistically significant (p<0.05). For each response, second-order polynomial models were developed using multiple linear regression analysis. Analysis of variance was performed to check the adequacy and accuracy of the fitted models.
Providing a quick way to predict the activity of yeast in the baking industry in terms of performance and quality is vital. In this paper, seven instant dry yeast samples of domestic and foreign manufacturers were assessed and compared by four methods for fermentative activity of Saccharomyces cerevisiae: Henry -Simon pressure meter, Gasography, microbial tests and baking test results showed a similar trend for yeast activity and demonstrated further power of Iranian yeast. In gasography and pressure tests, Fariman and French samples produced maximum and minimum gas volumes, respectively. The same trend was seen in microbial test (number of colony forming units) and baking test (loaf volume and height) for these two yeasts. Razavi yeast did not show significant differences with Fariman. Dezmayeh, Golmaye, Kelarmaye, Turkish and France yeasts showed significant differences compared with Razavi and Fariman (P<0.05). All tests showed a close correlation with the baking test. Using the pressure meter as the best method to assess the gassing power of bakery yeast was proposed. This quick and simple test can be a suitable alternative to long cooking methods to observe the capability of CO2 production in bakers’ yeasts.