دو تا سوال ازمایشگاه لبنی
هرچه دما بیشتر باشد phکمتر میشود.چرا؟
چرا در صورت زیاد بودن اسیدیته شیر ، الکل منجر به انعقاد پروتئین ها میشود؟
During heating, the most important change is that dissolved calcium and phosphate
become supersaturated and partly associate with the casein micelles. The additional
colloidal phosphate so formed has a molar ratio Ca/P ≈ 1. The reaction is roughly
ca(2bar mosbat)+H2PO4(1bar manfi)------>CaHPO4+H(1bar mosbat)
This implies that the milk becomes more acidic. (The drop in pH partly counterbalances
the insolubilization of Ca and phosphate.)
در رابطه با pH حذف دی اکسید کربن هم دخیل هست و باعث افزایش pHدر ابتدای حرارت دادن میشه اما بعدا با انجام واکنش میلارد pH افت پیدا میکنه. ولی دلیل اصلی میتونه همون شکل گیری کلسیم فسفات کلوئیدی باشه که با آزاد کردن هیدروژن باعث اسیدی شدن محیط میشه.
Addition of ethanol lowers the solvent quality for the hairs of κ-casein. This
causes the hairy layer to collapse and the electrosteric repulsion to diminish or
even to change in attraction. The latter effect is enhanced by a decrease of the
dielectric constant, resulting in a reduced electrostatic repulsion. Moreover, the
colloidal phosphate passes into another, unknown state which causes aggregation
of the ‘micelles’ to be irreversible. The lower the pH of the milk, the smaller the
ethanol concentration needed to cause coagulation. This principle may be applied
to quickly detect slight sourness in milk. In the so-called alcohol stability test,
milk and ethanol are mixed in fixed proportion. If visible flocculation occurs, the
milk is taken to be sour.
برگرفته از والسترا ویرایش دوم (۲۰۰۶)