Module 7. Butter-making process

Lesson 22

22.1 Introduction

Moisture control and working of butter are essential steps in butter manufacturing which determines the final body and texture of butter. When the butter granules are formed, its moisture is checked and the amount of makeup water is calculated to get desired moisture content in the finished butter. As water and salt are added after granules formation, it is not easy to incorporate these into mass of butter fat. Working of butter assists in proper incorporation of these into butter.

22.2 Adjustment of Moisture Content

The adjustment of moisture after churning is necessary so as to meet the legal requirements and also to control body and texture characteristics of the final butter. As per FSSR-2011, butter should not contain more than 16% moisture. The butter, after initial working is tested for its moisture content and then the required quantity of makeup water in calculated.

After initial working, a sample of butter is taken and analyzed for its initial moisture content (i.e. first moisture test). The factors that affect estimation of the correct amount of water to be added are:

a) Accuracy of sampling: Sample of butter should be taken from various places. If moisture content does not appear to be uniform, the sample should be taken from the places in the churn where butter with highest moisture content is present. Take a large sample and mix well to divide up the large droplets, before commencing the weighing.

b) Estimation of the load of butter in the churn: Accurate estimation of the quantity of water to be added is possible only if the load of the butter in the churn is accurately known. The method commonly recommended is to measure the weight or volume of cream in the churn, estimate the fat content of the cream and calculate the expected yield of butter from the churn on an assumed over-run.

22.2.1 Calculation of makeup water

Let first moisture be 15%, desired moisture content be 15.8%, weight of cream be 1000 Kg, fat calculate of cream be 40% and desired over run is 23%. Then expected yield of butter = Kg of fat ´ 1.23

= 400 x 1.23 = 492 Kg.

By straight method water to be added = ((15.8 - 15) / 100) x 492

= 3.94 kg

This basis of calculation, however, is erroneous. The first moisture is taken on unfinished butter and the second on the finished butter. So, before straight % method could be used, it would be necessary to correct the first moisture to the basis of finished butter. It would be simple to use the formula:

= ((desired moisture - first moisture) / water free solid in) x kg of butter in churn

= 100 part of unfinished butter

Then from example given above,
wt. of water to be added = ((15.8 - 15) x 492 / 100 - 15) = 4.63kg

i.e. the difference with respect to straight method is by 4.63/3.94 = 1.2 times. Therefore the correct formula may be given as:

Amount of water to be added

= ((desired moisture - first moisture) x kg of fat in churn x 1.25 x 1.2) / 100

*where over-run is 25%

22.3 Working of Butter

Working of butter is essentially a kneading process in which butter granules are formed into a compact mass. The primary purpose of working the butter is to completely dissolve, uniformly distribute and properly incorporate the salt, to accomplish complete fusion of brine and water in butter and to bring the butter granules together into a compact mass for convenient handling and packing.

Working of butter granules is carried out in two stages namely,

1. Initial working and

2. Final working.

During initial working, excess moisture and buttermilk is removed. This is followed by salt and make-up water addition and the butter granules are worked again. This is called as final working and the purpose of this is to properly incorporate salt and moisture in butter to form a compact mass.

After calculated amount of water and salt has been added, churn door is closed and is set in motion at slow speed. Working in this way is continued until the free moisture has been taken up by butter and churn is dry. At this stage there should be no moisture on the trier plug or a cross section cut from the block of butter and colour should be uniform.

It is safer to slightly over work butter than do under work. Under worked butter may be leaky in body with large visible water droplets and may develop mottles on standing. This favours mould growth. Moisture droplet size normally ranges from 1 to 15 micron and there are approximately 10 billion droplets/g of butter.

If grains are firm and hard, over working can cause stickiness. Over working of soft butter on the other hand, tend to produce butter with greasy texture. With softer butter over working may be necessary to prevent ‘mottled’ colour. Working affects the colour of butter (making it slightly light).

22.3.1 Effect of working on distribution of moisture in butter

The moisture is associated in washed butter in two forms. A portion of this water is present in form of a myriad of minute droplets enmeshed and permanently held within the butter granules. This portion constitutes approximately 8-9% of the weight of butter. The remaining moisture is present in loosely bound form between the butter granules.

At the beginning of the working process, much of the loosely held water is expelled and the moisture content of butter decreases to about 12 to 13%. As the working progresses, the butter loses its granular state and becomes less friable and more plastic. Free butter fat forms the continuous phase in which free water droplets starts to be assimilated. At this stage, moisture content of butter increases again. This increase continues and the amount of water that the butter is capable of assimilating in the working process depends on the firmness of butter, the speed of the worker rolls and the amount of free water in the churn.

22.3.2 Vacuum working

Besides increasing the degree of dispersion of water droplets, working also increases the air content (which favours growth of microorganisms, oxidative defects and therefore poor keeping quality of butter). Conventional butter contains 3-7% air by volume, with an average of 4ml/100g. To avoid air incorporation in butter, vacuum working is carried out. In vacuum working a partial vacuum is maintained during working. In winter the vaccum range from 30-40 cm. of Hg during the first part and from 15-20 cm. Hg during the last part. A lower vacuum is used during summer. This ranges from 20-25 cm during first part and 10-12 cm during the last stage of working.

If too high a vacuum is used, there is a possibility of drawing liquid fat out of the butter resulting in greasy butter. To prevent this, it may be necessary sometimes to omit using vacuum during final stages especially during summer.

22.3.3 Test for dispersion of moisture droplet in worked butter

Indicator papers may be used to check proper dispersion of moisture.

i) Bromo phenol blue indicator paper is used for butter in the pH range of 3-4.6 (ripened cream butter). The indicator paper is brought in contact with the surface of worked butter. Development of blue spots on indicator paper indicates improper working. No spot of blue colour will develop if moisture droplets are small and well distributed.

ii) Bromo thymol blue is used in the pH range of 6 to 7.6 and

iii) Bromo phenol red is used for the pH range 5.4 to 7.

22.3.4 Removal of worked butter from the churn

Worked butter is removed from the churn either manually (this is done with the help of a metal or wooden scoop) or by gravity (where a large metal tray, on wheel, is placed below the churn and churn rotated at slow speed with its gate open. The butter thus falls in the tray). In another method, a large metal tray is wheeled to and inserted into the churn. The churn is then rotated to lift the mass of butter and let into the tray. Besides this, quite often, butter is removed from the churn by means of compressed air (compress air at 3 to 5 psi is used to push out the butter – the butter in this case should, however, be soft.

22.4 Butter Over-Run

Over-run in butter may be defined as the difference between the weight of fat churned and the weight of butter made from that. In addition to fat, butter contains non-fatty constituents such as moisture, salt, curd and small amounts of lactose, acid and ash. These non-fatty constituents make over-run of butter.

22.4.1 Calculating Over-run in Butter

Over-run in butter can be calculated if fat content of final butter and the weight of the total fat present in cream is known. Suppose, the butter has 80% fat and the weight of butter in cream is 100 Kg, then the quantity of butter made will be:

Hence, butter made from 100 kg fat in cream is 125 Kg. Thus, the difference between butter made and the weight of butter fat in cream is 125 -100 = 25.

Thus, the percent over-run is 25%.

According to FSSR-2011, butter should contain a minimum of 80% fat, so maximum over-run possible in butter is 25%.

Other factors that influence over-run are accuracy of testing weight and fat content of cream, fat losses in butter milk, mechanical losses of fat etc.

Last modified: Friday, 5 October 2012, 9:41 AM