How is fluid milk composition related to finished cheese? 

Fluid milk fat    Fluid milk casein     Fluid milk C/F ratio     cheese FDB 
3.70%              2.55%                    0.689                          53.6%
3.90%              2.55%                    0.654                          54.8%

Calculation method:     
fluid fat * 100 = lb fat available
Lb fat available * 0.93 = lb fat retained as cheese solids
((Fluid casein * 100) - 0.1) = lb coagulated casein retained as cheese solids
(Lb cheese fat + lb coagulated casein)* 1.09 = lb total cheese solids
(Lb cheese fat / lb total cheese solids) = cheese FDB

Levels of fluid milkfat, protein and other solids can be conveniently manipulated to give a specified final ratio. Part skim fluid milk (heightened C/F ratio) results in reduced fat products such as Mozzarella compared to full fat cheese varieties like Cheddar made with whole milk. Whole milk fortified with condensed or slurried skim will result in a similar finished cheese composition as partially skimmed fluid milk. 

Equations to illustrate fortification of 3.7% fat, 3.1% protein whole milk with 30% skim slurry or whey cream to manufacture Cheddar cheese are shown below:

C/F ratio > 0.687 using skim slurry to decrease Cheddar cheese fat level
Cheese FDB = (0.1796 * ((C/F)^2)) - (0.5983 *(C/F)) + 0.8631

C/F ratio <0.687 using whey creams to increase Cheddar cheese fat level
Cheese FDB = (0.2729 * ((C/F)^2)) - (0.6936 *(C/F)) + 0.8847

NOTE: different equations due to noticeable 'other' solids inclusion when fortifying with skim slurry

Similar facility-specific equations can be used to estimate economic benefits or costs when changing Cheddar cheese fat levels when one knows current values for whole milk, nonfat dry milk (NDM) with slurry prep cost, and milkfat in the form of whey cream. Recent high fluid milk along with relatively steady NDM prices might have favored skim fortification (reduced cheese fat with increased vat milk C/F levels). Consideration of whey cream and skim slurry dual fortification might even be more economically attractive.

The most noticeable differences when fortifying will be increased cheese yield per hundredweight vat volume as well as possible inclusion of more “other” fluid milk solids when fortifying with skim. If such solids increases, namely lactose, lead to cheese quality defects then one could consider a wash or curd rinse before salt addition. 
Keep in mind that any rinsing will decrease overall cheese yield plus increase waste disposal or whey handling costs. 

Moisture control in cheesemaking is somewhat more artistic than the previous basic fluid milk compositional changes. Rate of cooking as well as curd particle size, agitation, final cook temperature, stir-out time at that elevated temperature, water temperature and extent of curd washing, as well as curd acidity prior to “dry stirring” and salted curd handling all have an effect on final moisture. 

Two examples of unsalted curd handling and associated affect on finished cheese moisture are LMPS Mozzarella @ 50% moisture, 40% FDB compared to Parmesan @ 32% moisture and similar FDB. Hopefully, one can see that such Mozzarella is manufactured using less severe conditions than Parmesan although both varieties started with similar fluid milk compositions.

Two examples of salted curd handling and associated affect on cheese moisture are again “traditional, pasta filata” LMPS Mozzarella (50moisture, 40FDB) compared to non pasta filata Pizza cheese @ 45-46% moisture made from the same salted curd. In this case, the relatively unstructured Pizza cheese curd typically loses more moisture during so-called “Cheddar-type” handling than heated and stretched internally structured Mozzarella.

Some might say that cheese moisture determines dry fat content. I submit the thought that dry fat somewhat determines moisture content. I use the previous Pizza cheese (>45 moisture, <45 fat-dry basis) and Cheddar (<38 moisture, >50 FDB) as two examples of that theory. Pizza cheese might have similar level of coagulated casein compared to Cheddar, but the lack of fat could “open” more opportunity for casein-water binding. 

It might be an interesting bit of information to know a more precise relationship between overall cheese fat and moisture content. This would give us guidance as to the seasonal variations noted between winter and summer relative to cheese texture and associated moisture content. One generally runs lower moistures in summer to maintain consistency of cheese organoleptic and functionality. 

My research questions are: 
(1) How much moisture variation at the same cheese solids composition is required to maintain commercial consistency throughout the year?
(2) How do different cheese varieties fare in this same regard to moisture, FDB, and commercial consistency?
(3) How much does NDM fortification help in these regards? Summer cheese is generally firmer when using NDM. Winter cheese does not seem as affected relative to commercial consistency whether or not one is fortifying with NDM.
(4) Do the structures and/or composition of casein and milkfat vary during lactation or are these seasonal cheese consistency observations due to some other cause?
(5) Other than increasing NDM fortification, cheese salt levels and target cheese pH while reducing cheese fat, and moisture, what are the recommendations to maintain acceptable summer cheese quality? 

The reason for this last question is the relatively high associated cost and low cheese yield per hundredweight whole milk during typical summer seasons. 


Our Expert:
Don Dahlstrom has over 33 years of dairy experience in varied positions. Don is currently very active consulting for companies throughout the world. He holds several cheesemaking patents and does not want these articles to go unchallenged. All articles remain open to debate.
To ask Don a question or follow-up on this question, e-mail: columnists@cheesereporter.com.•

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