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دانلود رایکان مقاله انگلیسی ISI با موضوع پخت نان با استفاده از فناوری گرمایش اهمی

عنوان فارسی مقاله:

پخت نان با استفاده از فناوری گرمایش اهمی؛ یک بررسی جامع مبتنی بر آزمایشات و مدلسازی

عنوان انگلیسی مقاله:

Bread baking using ohmic heating technology; a comprehensive study based on experiments and modelling

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بخشی از مقاله انگلیسی :

3. Results and discussion

3.1. Electrical conductivity of non-yeasted dough

The electrical conductivity of the dough was determined using Eq. (3); its evolution with the temperature at the centre of the dough is shown in Fig. 2. The error bars are represented every minute only, in order to get a clear view. The curve exhibits a threestage pattern. The first stage is linear (R2 > 0.999 for each one of the replications) until around 60 C. During the second stage, the rate of electrical conductivity increase slows down (when reaching about 0.80 S m1 ), and the electrical conductivity starts to decrease slightly. This second stage can almost be assimilated to a plateau. Around 76 C, the electrical conductivity starts to increase again, reaching a linear increase rate after about 80 C (R2 > 0.99). The temperature at which the linear evolution of electrical conductivity stops corresponds to the beginning of starch gelatinisation. This pattern is consistent with that observed by Li et al. (2004) with starch solutions. The area for the motion of electrolytes starts to decrease at the onset temperature as the swelling of starch begins, until the endset temperature at which all starch is gelatinised, and then electrical conductivity starts to rise again linearly. However, as mentioned by Li et al. (2004), the slopes (ds/dT) are different before and after starch gelatinisation. This fact means that there is a modification in the dependence of electrical conductivity on temperature and suggests a change in the product, and therefore in the displacement of the electrical current. The authors suggested that this was due to the viscosity of the starch solution, higher after starch gelatinisation than before, which in our case could be assimilated to the dough/crumb transition.