BUTTER CHURNING

BUTTER CHURNING ,THEORY OF CHURNING,FACTORS INFLUENCING CHURNING

1. CHURNING OF BUTTER -DEFINITION-THEORY OF CHURNING-FACTORS INFLUENCING CHURNABILITY OF CREAM

2. DEFINITION Agitation of cream at a suitable temperature until the fat globules adhere forming larger mass and until a relatively complete separation of fat and serum occurs. The purpose of churning is to destroy the 5-10 nm thick fat globule membrane Butter oil emerges from porous parts of membrane and fat agglomeration takes place. For Agglomeration of fat globule into butter granules to take place, its necessary that part of fat in crystalline form.

3. Contd …. Agglomeration is difficult at too low temperature when the proportion of liquid fat is too low And also difficult at too high temperature when all the fat is in liquid form. So, Higher the fat content – lower should be the temp. During churning the fat in water emulsion changes to water in fat emulsion

4. Factors influencing churnability Chemical composition of fat Size of fat globules Viscosity of cream Temperature of cream at churning Fat % of cream Acidity of cream Load of churn Nature of agitation Speed of churn

5. Design of butter churn Cylindrical wooden drum rotating around horizontal axis Diameter- 2m & 2.5m long Cream 45% of its volume. Battens inside of churn help in formation of foam & butter granules. Speed -20rpm Time -45 minutes Churning temperature : Winter --- 10-13°C; Summer--- 7-9°C

6. RPM for efficient churning varies with diameter. Large churns have small speed than smaller churns. High speed centrifugal force will exceed gravitational force &cream will stick to periphery & rotate with drum. mw²R <m. g. n=rpm (2∏n)² R < g R = radius n < √(g/R)*1/2∏ ≈1/2√R m=mass

7. Butter churn

8. Cylindrical butter churn

9. Conical butter churn

10. THEORIES OF CHURNING FISHER AND HOOKER ‘S PHASE REVERSAL THEORY Churning is a process of phase reversal Changing oil in water type of emulsion to Water in oil type of emulsion Agitation in cream Causes coalescence and clumping of fat globules The ratio of surface area to volume of fat -- so small No longer contains all the buttermilk in stable form Fat in water emulsion breaks

11. RAHN’S FOAM THEORY cream contains a foam producing substance which gets solidified gradually when cream (or milk) is agitated. During churning: first foam is produced fat globule tend to concetrate on the foam bubble clumping of fat globule takes place thus the foam producing assumes a solid character and the foam collapse. Then the fat globules is tend to form coalesce and butter is formed

12. Contd … Based on his findings Rahn conclude that: Air was necessary for normal churning of butter. In the absence of air did not result in churning of cream.  Overloading of churn resulting in increased churning time. But this theory is criticized because of the fact that foam formation i.e. presence of air, is not required in some of the continuous butter making processes

13. KING’S MODERN THOERY In cooled cream, fat is present as clusters of fat globules. Within each globule it is present partly as solid and partly liquid. Churning breaks the clusters and causes foam formation   fat globules become concentrated to air bubble in the foam thus are brought into close contact of each other. The globules then adhere together to form larger and larger particles. Eventually these particles become visible as butter grains.

14. Contd … The butter grains causes the globules to move over one another.   Finally the butter is obtained