Butter is a water-in-oil emulsion with the milk proteins acting as the emulsifiers. At refrigeration temperatures, butter remains a firm solid. However, it softens into a spreadable consistency and melts into a liquid at relatively low temperatures.
In the butter making process, you can choose to use either sweet cream or sour cream to produce the product that you desire. Sweet cream is a fresh cream without any developed acidity while sour/aged cream has developed acidity.
The Butter Making Process Flowchart
Step One: Neutralization Process
This process takes place just before the cream pasteurization begins. However, it is not a mandatory process and you can skip it when dealing with fresh cream (0.1 – 0.12% lactic acid).
Neutralization process aims to achieve the following purposes
- Lowering the acidity of the cream to a point that allows effective pasteurization
- Eliminating abnormal flavors in butter; high acid content promotes oxidized and fishy flavors.
- Producing a product with consistent quality parameters.
Lime and soda-based neutralizers are very effective in cream neutralization.
Soda-based neutralizers include: Sodium hydroxide, Sodium bicarbonate, and sodium carbonate
Lime-based neutralizers include: Calcium hydroxide, calcium oxide, and calcium carbonate.
When the cream has an unusually high level of acidity, you should use a combination of these two types of neutralizers. Using a large quantity of soda-based neutralizers to neutralize such a cream will cause partial saponification.
On the other hand, using large volumes of lime-based neutralizers will cause a strong limy flavor in the product, and will become very hard. You have to strike a balance for successful butter making. In some instances, you will find the acidity indicated in a different scale other than the percentage lactic acid.
Listed below are some of the common scales that represent the acidity index.
a) Dornic scale (°C) ==> 10°D
It represents the volume (in ml) of 0.11N NaOH used per 100 ml of the sample.
b) Soxhlet Henkel scale (°SH) ==> 4.4°SH
It represents the volume (ml) of 0.25N NaOH used per 100 ml of the sample
c) Thorner scale (°Th) ==> 11°Th
It represents the volume (ml) of 0.1N NaOH used per 100 ml of the sample.
Determining the percentage (%) lactic acid in a sample
% l.a = {[Vol (ml) of 0.1N NaOH × 0.009]/[volume (ml) of sample]} × 100
0.009 is a constant and you derive it as follows:
If 1 lit (1000 ml) of 0.1N NaOH neutralizes 9g of lactic acid
1 ml will neutralize (9/1000) = 0.009g of lactic acid.
Molecular equivalence between the lactic acid neutralized and the neutralizing agent
- CH3CHOHCOOH : NaOH = 1:1
- CH3CHOHCOOH : NaHCO3 = 1:1
- CH3CHOHCOOH : Na2CO3 = 1:2
- CH3CHOHCOOH : CaCO3 = 1:1
- CH3CHOHCOOH : Ca(OH)2 = 1:1
After determining this ratio, you will be able to know the volume of alkali required to neutralize the lactic acid according to the ratio of the reaction.
Amount of neutralizing agent = (Acidity determined – Desired acidity) × Molar equivalent × Volume of the product.
Example
If you have 1000 kg of cream with 40% butterfat and the acidity is high at 0.5% lactic acid to be neutralized to 0.1% lactic acid using NaHCO3. Calculate the amount of neutralizer(s) to use in your butter making process.
Solution
Amount of acid to be neutralized is 0.5% – 0.1% = 0.4%
0.4% of the 1000 kg cream is 4 kg of lactic acid
Ratio of alkali (NaHCO3) : lactic acid in the neutralization reaction
NaHCO3 : 90 (molecular weight of lactic acid)
84 (molecular weight of NaHCO3) : ?
Amount of neutralizer = 4 kg of l.a × (84/90) = 3.73 kg of NaHCO3
If you were to use Na2CO3 as the neutralizer, what amount would you need?
Amount of neutralizer needed = 4 kg l.a × (53/90) = 2.35 kg of Na2CO3
Note: 63 is half the molecular weight of Na2CO3 because its molecular equivalence in a reaction is 1:2
If you were to use NaOH as the neutralizer;
Molecular volume of NaOH is 40
Amount of neutralizer used = 4 kg l.a × (40/90) = 1.77 kg of NaOH
Adding the neutralizers
- Ensure high precision during weighing. Add excess and saponification will occur; too little and precipitation of the cream occurs.
- Dilute the neutralizer in a small amount of warm milk before adding to facilitate mixing.
- Add the diluted neutralizer to the cream at 30°C while gently stirring. Rapid/violent stirring will cause foaming of the cream.
- If the acidity of the cream is very high, use a combination of both lime and soda-based neutralizers. For instance, when the acidity is 0.4%, use 0.2% soda and 0.2% lime-based neutralizers. When you use lime-based neutralizer alone, it will cause cream thickening and produce a limy flavor.
Step Two: Pasteurization
You first determine the heat stability of the cream then subject it to high temperature pasteurization. Pasteurization ensures that the resultant butter is free from all pathogenic microorganisms. The time/temperature combination for cream pasteurization varies according to the method of pasteurization used.
Reasons why cream undergoes high temperature pasteurization
a) Fat is a poor conductor of heat
Fat can insulate some microorganisms if normal pasteurization temperatures are used. High temperatures ensure the destruction of all the microorganisms in the cream.
Peroxidase test confirms the effectiveness of cream pasteurization. Peroxidase is more heat resistant than alkaline phosphatase. It is destroyed at 80°C/15-20 seconds in continuous pasteurization, 75°C/30 minutes in batch pasteurization, and 140°C/2-4 seconds in UHT pasteurization.
Pasteurizing milk products with more than 8% fat content under low temperatures reactivates the alkaline phosphatase enzyme.
b) To denature lipolytic enzymes/lipases
Certain psychrotrophic bacteria such as Bacillus cereus and Pseudomonas spp. produce heat resistant proteolytic and lipolytic enzymes. To get rid of such bacteria, subject the milk to thermisation treatment. This is where you subject the milk to heat treatment at lower temperatures than pasteurization temperatures but for the same time period, e.g. 65°C/15-20 seconds.
c) To produce sulfhydryl groups (SH)
High temperatures denature whey/serum proteins. This opens/exposes the amino (SH) groups, which produce burnt flavors. These SH groups serve as inherent antioxidants and add preserve the product.
d) To remove strong flavors through vacreation systems
Through vacreation (also known as vacuum pasteurization), the boiling causes the volatile flavors to escape.
Step Three: Cooling and Handling of Cream
The cooling order is designed to control the formation of crystals of fat so that the resultant butter has the desired consistency. The butter must remain firm enough at room temperature and elastic enough to allow for spreading.
Without varying the cooling program of the pasteurized cream, the consistency of the butter would depend exclusively on the chemical composition of the fat and subsequently vary with season or feeding. The cooling program is designed to suit the iodine value hence optimize the butter consistency.
During cream cooling, the high melting point fat crystals will form first and form a mesh around the low melting point fat. During this process, timing is key. Hold for a very short period and a leaky butter forms, which will lead to lots of losses in the buttermilk. If at all you have to use a shorter cooling time then it is advisable to use a lower cooling temperature to facilitate firming up of the mesh.
Longer holding time at lower temperatures produces a firmer butter due to a stronger mesh. You can churn such butter at high temperatures without incurring much loss because the cream has undergone complete crystallization.
Cream cooling regimes: Plasticity of fat based on its Iodine Value
a) Treatment regime for hard fat with Iodine value of 28-29.
Here, you should first cool it to 8°C for 2 hours then warm it up to 21°C for another 2 hours then finally cool to 16°C. This treatment program aims at optimizing the liquid fat by converting some of the solid fat into liquid fat, adequate for the churning process.
Cooling the fat to 8°C causes formation of large number of small fat crystals. These crystals bind the fat from the liquid phase onto their surfaces. Warming to 21°C causes conversion of some solid fat crystals into liquid. At this point, only the high melting point fat crystals remain solid. They continue to grow bigger during the 2-hour storage period. Cooling down to 16°C causes binding up of more liquid fats onto the surface of the crystalline fat.
Following this treatment regime, the high melting point fat crystals collect more fat onto their surfaces and grow in size. This increases the efficiency of the butter working process as more butter oil is obtained during churning.
b) The low melting point fat treatment regime (fat with IV <40)
Cool to 19°C then to 16°C and finally down to 8°C. At 19°C, most of the fats are still in liquid form. Cooling to 16°C initiates fat crystallization. When the crystallization has started, cool the cream rapidly down to 8°C through a superfast cooling process.
Rapid cooling promotes rapid crystallization and formation of tiny crystals, which have higher surface area hence move up the column. Superfast cooling encourages formation of tiny crystals, which bind more liquid fat hence reduces loss in the buttermilk.
Climate and the feeding regime affect the IV index of fat. In Kenya for instance, the weather does not vary considerably hence the IV of fat varies between 25 and 35.
Types of cream used for making butter:
i) Sweet cream
This is the cream without formed acid. You cool it immediately after pasteurization to between 4°C – 6°C for 8 – 10 hours. This allows for partial formation of the fat crystals (ageing).
After aging, you raise the temperature to between 8°C – 11°C, which are the most appropriate temperatures for butter churning. At these temperatures, you will obtain butter with a better consistency and incur minimal losses.
ii) Sour cream
After pasteurization, cool the cream to between 15°C – 20°C and inoculate with 2 – 4% starter culture. The starter culture will produce acid and flavor components. Stir the inoculated cream gently to ensure that the starter culture is evenly distributed in the cream.
The incubation lasts for between 10 – 15 hours or check for the pH value of between 4.4 – 4.6. At this pH, all the MSNF coagulates. During the early stages of acidification, homofermentative bacteria predominates the medium. As the acid increases (medium becomes more anaerobic), anaerobic Leuconostoc spp or diacetilactis takes over the fermentation process.
Mesophilic cultures are preferable in cream pasteurization due to the low fermentation temperatures involved. Once the fermentation process is complete, lower the temperature to 8°C – 11°C, which is the churning temperature range.
Justifications for culturing before churning cream
- Culturing lowers the pH of the cream and preserves the product by hindering microbiological activity.
- To control the culturing process, control the amount of the inoculum, the incubation temperatures, and the incubation time.
- You can also monitor the pH as a control measure. Using the pH as a control method can be very effective due to the use of optimal pH of the product as a reference point.
- You should practice proper culturing techniques if you expect to end up with a high-quality product.
Aroma formation
Apart from acid formation, optimum CO2 and aroma components are also important indicators of a proper culturing process. These components give the butter a fresh aromatic flavor.
The fermentation process yields a product, acetyl methyl carbinol, which is either reduced into a flavorless product (acetoin) or oxidized to form diacetyl.
This conversion depends on oxygen tension and the pH of the medium. Under normal conditions, oxygen tension and pH will be such that most of the acetyl methyl carbinol is reduced to acetoin. However, at lower pH values and high oxygen tension, more diacetyl will form. You can achieve this by stirring more oxygen into the fermenting cream. Do not forget that diacetyl is a volatile compound, which you will need to stabilize by cooling the cream.
When you use only the D-culture (predominated by L. lactis diacetylactis), acetaldehyde is produced. This acetaldehyde produces the yoghurt flavor. Leuconostoc spp. has the ability to convert the acetaldehyde into milk diacetyl. On the other hand, you can ferment the butter by adding lactic acid concentrate with flavor components into the butter during the kneading process.
Step Four: Churning Process
This is the process of converting the fat in cream from a discontinuous phase to a continuous phase. This process also converts the fat globules into fat granules.
The churning theory
The three most predominant theories of butter churning include the following:
i) Agglomeration/form theory
Applicable when converting the cream to butter
ii) Concentration theory
Applicable when using very high concentration cream/plastic cream
iii) Combination theory
Preferable when reconstituting butter using butter oil (99% purity). Yields butter with 88% butterfat content.
Methods of churning
You can choose to use either batch or a continuous system depending on several factors. Regardless of the method you use, the form theory still holds.
How the form theory of butter churning works:
The fat globule membrane (FGM) consists of various molecules that are partially fat-soluble and partially water-soluble. These two ends are repellent to each other, necessitating the need for a neutral phase. The air bubbles provide the required neutral phase.
The membrane materials are phospholipids and lipoproteins that seek to place themselves in the interphases between the water and fat or between water and air. During churning, foam forms. The FGM that seeks the water/air and water/fat interfaces enter into a competition and attach themselves onto the air bubbles.
Agitation removes the membrane materials. Consequently, the liquid fat spreads over the inner surface of the air bubbles of the water/air interface. As the churning continues, the bubbles collide, caombine and burst decreasing the total surface. After rapturing, the fat globules coalesce to form granules. The liquid fat becomes the cementing agent for the granules.
The fat globules, which have lost some of the membrane materials during the process aggregate into a smaller surface. Here, they coalesce to form granules with the liquid fat holding them together.
Break-point during butter churning
This is the stage during churning when the butter grains separate from the serum phase. The butter grains are visible and the buttermilk starts washing the sight glass. This process may delay to reach the breakpoint due to excessive foaming, which you can reduce by releasing excessive gas. You can also add breakwater (chilled water) to induce breakpoint.
However, when you are manufacturing sweet cream butter, try not to use breakwater because it will adulterate the buttermilk. Buttermilk from the sweet cream manufacturing process is usually recycled.
Step Five: Washing the Butter Granules
Stop churning immediately the granules attain the desired size (diameter of 3 – 5 mm). drain the buttermilk off. Some of the coagulated proteins will remain in the granules and act as sieves to ensure only buttermilk drains off.
Adding chilled water before draining the buttermilk ensures a better separation of the granules from the buttermilk. The common practice is to add wash water of an equivalent amount of the drained buttermilk and churning for about 10 minutes with the wash water.
The length of churning will depend mostly on the status of the butter granules and the quality of the buttermilk. If necessary, you can wash twice. This also improves the consistency of the grains. When you have used a good quality cream for the manufacturing process, you can use chilled buttermilk to wash the butter granules.
Step Six: Working/Kneading the Butter
After draining the buttermilk and washing the butter granules, your butter is now ready for kneading.
Objectives of kneading
- To homogenize the separate granules
- Removing any remaining buttermilk and wash water
- To distribute the moisture content in the butter in form of tiny droplets
- To uniformly distribute the salt and other additives added at this stage
During working, you get to press the granules together thereby pressing out part of the watery phase to achieve the desired moisture content. To ensure effective water removal, ensure that the butter grains attain a certain level of firmness otherwise it will not be possible to remove or incorporate water/moisture.
Some important formulae in the butter making process
How to calculate the amount of neutralizer to use in high acid cream
Neutralizer quantity = cream quantity (kg/ltrs) × (% l.a in cream – desired % l.a in cream) × molar equivalent of neutralizer to lactic acid.
For instance, if you use sodium bicarbonate, it will be 84/90 and if you use sodium carbonate, it will be 53/90 instead of 106/90.
Calculating expected yield from the butter making process
Weight of butter = weight of cream × % B.F of cream × 1.2
Calculating the amount of salt to add during the butter making process
Weight of salt = % salt needed × weight of expected butter.
Calculating the amount of makeup water (water to add)
Makeup water = {[desired M.C – M.C in butter] × estimated amount of butter}/[100 – M.C in butter.
Calculating percentage overrun
% butter overrun = [(butter – pure fat) × 100]/pure fat
Calculating effective salt concentration in butter
Note: effective salt is the % of salt in water.
Effective salt = (2 × 100)/16 = 12.5%
Step Seven: Packaging, Storage, and Summing up the Butter Making Process
After manufacturing, you can now package the butter in various packs depending on the intended use. You can use grease proof paper, vegetable parchment, laminated foil, lacquered tins or plastic tubs for packaging.
The reason for using these materials is to ensure that the butter does not lose moisture or absorb a foreign flavor during storage. Infusing nitrogen into the butter helps keep the butter soft and spreadable even at refrigeration temperatures.
If you intend the butter almost immediately, store it at low temperatures of about 5°C. However, when the butter is to be used at a later date calling for a long-term storage, lower the storage temperatures to -25°C. Lower temperatures improve the keeping quality of butter and reduces the risk of package distortion during handling.
Here is a video of the butter making process for home-made butter. Even though it does not show the salting and kneading process, it gives you a rough idea of the butter making process.
Video by Reviving Tradition
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