الجبن الطري ينقسم الى
1-أجبان طرية طازجة soft fresh cheese
أ-جبن طازج ناتج عن التخثر بالحامض Acid-coagulated Fresh Cheese
ب-جبن طازج ناتج عن التخثر الأنزيمى Rennet-coagulated Fresh Cheese
ت-جبن طازج ناتج عن الفصل بالحامض والحرارة Heat-Acid Precipitated Cheese
2-أجبان طرية منضجة Soft-Ripened Cheese
HEAT-ACID PRECIPITATED CHEESE
الجبن الناتج عن الفصل بالحامض والحرارة
Ricotta cheese is made from heat-acid precipitation of proteins from whey or whey-milk blends. The best Ricotta is made from very sweet whey (pH 6.4 - 6.5) without any addition of milk or acid. During heating whey proteins begin to coagulate at about 70C. The rate of coagulation increases as the temperature is raised to 90C and a thick layer of curd forms on the surface of the whey. When coagulation is complete and the curd is firm (after 10 - 20 min. at 90C), the curd is removed with perforated scoops and placed in forms. After removing the first rise, addition of acid (to about pH 5.9) will induce a second rise of coarser curd. If the pH is correct the whey should become clear.
It is now uncommon) to make Ricotta cheese from whey only because:-
(1) Sweet whey with pH>6.4 is not always available
(2) the traditional hand skimming process of removing the floating curd is hot and tedious (يقصد أن وجود بعض الكازين يقوى الخثرة مايسهل كشطها بالطريقة التقليدية)
(3) yields are low
All of these problems are avoided or reduced by adding milk or skim milk before heating. Whey pH as low as 6.1 is then acceptable, the curd can be recovered by mechanical means and the yield is increased.
the manufacture of Ricotta cheese from blends of milk and whey
1-Collect whey (pH>6.1) and weight it into a cylindrical vat. Sweeter whey (pH>6.4) is preferred. Immediately heat the whey to 50C to stop culture growth.
2-Add milk or skim milk (up to 25% of the total weight).
3-Heat by direct steam injection from the bottom of the vat to 80-85C without agitation.
4-Add citric acid (5% solution) to induce maximum coagulation of caseins and whey proteins. The required amount is about 140 g citric acid monohydrate per 1,000 kg of whey-milk blend. The required amount can be determined exactly by titrating a sample of the blend to pH 5.9-6.0 at 20C. Alternatively, add the acid slowly until the whey becomes clear.
5-Continue heating WITHOUT agitation to 90-95C.
6-Hold the curd for an additional 15 min. at >90C. Then scoop the curd into the forms using perforated ladles. Fill the forms in rotation until they are level full.
7-Cover the forms with a clean cloth, place chopped ice on the cloth, and roll the drain table into a cold room (0 - 4C).
8-When the curd is cool it can be packaged in plastic tubs or wrapped in wax paper for immediate sale.
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