CHEESE TECHNOLOGY

Module 10. Yield of cheese

Lesson 23
CHEESE YIELD, MEASUREMENT OF CHEESE YIELD

23.1 Introduction

The yield of cheese and its control are of great economic importance, determining the profit of cheese plants and the price of milk given to farmers. Therefore, cheese yield and the factors that affect it need to be studied thoroughly. Cheese yield calculation is important for measuring the efficiency of and determining the economic viability of a cheesemaking operation. It also aids in evaluating the potential usefulness of a particular process or change in technology.

23.2 Definition

Cheese yield may be expressed as the quantity of cheese of a given dry matter produced from a given quantity of milk with a defined protein and fat content (kg/100 kg milk). Actual cheese yield (Ya) is often slackly expressed as the ‘kilogram of cheese per 100 kilograms of milk’ or ‘per cent yield’.

23.3 Measurement of Cheese Yield

Measurement of cheese yield requires determination of weight of all the inputs and outputs. This can be easily achieved in a pilot scale plant where cheese is made in batches but in commercial/large scale cheese manufacturing, this cannot be done batchwise. In such plants, yield is calculated on daily basis rather than calculating it batchwise. Once all the inputs and outputs are determined, the actual yield can be calculated as:

Although all different varieties of cheeses have standard limit for maximum moisture content, some batch to batch variations are unavoidable. Thus comparing yields of cheese having different moisture content is erroneous. To avoid the effect of moisture content, yield can be calculated by using the following equation:

Other than moisture, many factors affect the yield of a particular variety of cheese, including the milk composition, the cheese making process, and the type of plant equipment. The latter two factors influence cheese yield, since they affect the recovery of milk fat and protein in the cheese. If a manufacturer wants to compare cheese yields of different days in a year, then comparing the actual yield (Ya) or MCY would be erroneous as the yield is also affected by the actual recovery of fat and protein in cheese and also by the composition of the raw milk. In this situation, if the composition of the cheese milk (protein and fat) and the cheese (protein, fat, and salt) at the different manufacturing times are known, the yield of cheese at the different times may be meaningfully compared by adjusting the protein and fat content of the milk to reference values. The resulting yield expression is termed the moisture-adjusted cheese yield/100 kg milk adjusted for protein and fat (MACYPF):

The above equation assumes that casein content of protein is not changing over time. If it is prone to change over time, then protein content may be replaced by casein content in the same equation.

23.4 Prediction of Cheese Yield

Cheese yield is mainly affected by fat and casein content of milk and recovery of these components in the final product. A general formula for calculating yield may be expressed as Y= aF + bC, where Y is the yield, F and C are fat and casein contents in milk respectively, and a and b are the coefficients which are related to fat loss and casein recovery during manufacturing process. Several formulae are developed for prediction of cheese yield, depending on the cheese variety and composition of the cheese milk. Predictive yield formulae are useful in a cheese plant to measure its efficiency by comparing actual and predicted yields, for better production planning and also to plan product mix. Formulae for some varieties of cheese are given below:

23.4.1 Cheddar cheese

Van Slyke and Price Formula:

Where F = kg fat/100 kg milk; C= kg casein/100 Kg milk; W= kg water/kg cheese

23.4.2 Mozzarella cheese

M = kg water/kg cheese

23.4.3 Cottage cheese

4.9TS-29.72 = Yield ± 0.99

Where TS= total solids of skim milk

These formulae are established on the basis of average fat loss in whey and during other processes like plasticizing in Mozzarella cheese, average loss of casein in whey and increase in the weight of cheese due to other constituents and the added salt. For instance, in the formula for Cheddar cheese, 0.93 is the percent recovery of fat, C–0.10 indicates 10% loss of casein and factor 1.09 is for increase in the weight of cheese by other constituents of milk and added salt.