Production of Ymer.
(soft cheese)

Culture : Probat M 4 or “set milk” from Danlac web store.
Fat content : Min 3 % (3- 4 % BF)
None fat solids (NFS): 11 % (11 - 14 %)
Acidity : 110 Th? (1.0 % lactic acid)

Difference between Ymer (soft case) and other cultured products (yoghurt):
High total solids, which makes it dry, smooth with a mild acidic and aromatic taste.

Pasteurizing: Skim milk pasteurizes to negative peroxidase test. It is important that the milk is not pasteurized too high, as it reverses the ability for whey separation. The milk is then pumped to a double jacked tank or cheese vat.
Heating and cooling is done in the jacket and is preferable done with warm and cold water, but heating can also be done by steam.

Culturing: The milk is added 0.5 - 2 % culture and setting temperature is 20 - 23 ?C. Addition of 2 ml. rennet (single strength) per 1000 lt. milk has been tried but is not necessay for whey separation.

Concentration: After 20 - 24 hours of acid development, the curd is stirred very carefully and is heated with warm water or steam in the jacket. The water temperature should not be higher than 35 ?C.
Steam as well as well as too high temperature water mean the mass will be heating uneven, which can course relative hard lumps. Under heating, the mass will raise, so that whey can be drained gradually. To obtain 14 - 15 % solids, 46 % is drained. If pasteurizing, culturing and heating are done right, the draining of whey will last not more than 3 - 4 hours.

Standardizing: How much whey to drain and cream to add to obtain the right solids with the right cream content, can be calculated by knowing the solid content of skim milk, whey and cream plus the fat content of the cream.
The amount of whey drained is X and added cream is Y, the calculation can be done using the following formula:

I : 100 x St - X x Vt + Y x Ft = Yt (100 - X + Y)
II: Y x Ff = Yf = Yf (100 - X =Y)

St Skim milk solid approx. 8.9 %
Vt Whey solid approx. 7.0 %
Ft Cream solid at 40 % fat content approx. 45.5 %
Yt Ymer solid Approx. 15.0 %
Ff Cream solid approx. 40.0 %
Yf Ymer fat content approx. 3.5 %

Ymer cont.…

Isolate X of the two equations above:

100 Yt (Ff - Yf) + Yt Yf - Yf Ft - St (Ff - Yf)
X = Yt ( Ff - Yf) + Yf Yt - Vt (Ff - Yf ) - Yf Ft

After which Y can be calculated by replacing the value of X in one of the above equations.

By inserting the found values, 47 liters of whey is drained per 100 liters skim milk and 7.3 liters cream is added, which gives 60.3 liters Ymer.

Homogenizing:After stirring, the mass is homogenized. The purpose of homogenizing is to obtain an even, smooth and homogen consistency. Before the homogenizing, the mass looks like grainy soup. Homogenizing of the fat is zero, as the process is taking place with temperature of 25 - 30 ?C, and the fat is therefore not liquid.

The mass is therefore slow flowing and grainy, which makes it difficult for the homogenizer to suck through. A pump is used for even flow trough the homogenizer.

Cooling: Immediately after homogenizing, the Ymer is cooled in a plate cooler to 12 - 15 ?, but not lower then 10 ?C.

Filling: Filling is done in plastic cups or paper cartons such as Perga, Tetra Pak, or similar packaging material.

Modifications: The time consuming part with heating and draining can be modified by skim milk cultured by 10 % culture and setting temperature of 30 ? C. When the curd is formed, which is normally after 5 hours, the mass is stirred carefully. The next morning (if lucky), the mass has risen to the top and a sufficient amount of whey can be drained without heating. The rest of the process goes as above.