Butter Making

What is Butter?

Butter is legally defined in most jurisdictions as a water-in-oil emulsion with a minimum 80% milk fat content and maximum 16% water. Composition typically runs:

Butter, butteroil and ghee distinctions

Butter is the water-in-oil emulsion described above. Butteroil or AMF (Anhydrous Milk Fat) is 99.9% pure butterfat, produced by heating, vacuum (to strip volatile odours) and centrifugation — either directly from cream or from butter. Ghee is similar to AMF but less refined, made by a simpler boiling and decanting process; it retains more browned milk-solid flavour notes and is most common in South Asian and Middle Eastern markets.

The Buttermaking Process

1. Cream separation

Butter starts with cream separated from whole milk using a centrifugal separator. Standard separator output for buttermaking is cream at 40% fat. A higher cream fat (up to 48%) gives lower cream volume per unit fat — useful where storage or transport is constrained — but standardising at 40% is the most common workable balance.

2. Cream pasteurisation

Cream is typically pasteurised at ~80°C in the EU (higher temperatures than milk pasteurisation due to higher fat protecting microorganisms thermally). In developing countries with higher microbial loads, pasteurisation temperatures may run higher still. For cultured butter, the cream is then cooled and inoculated with lactic acid culture for diacetyl development before ageing.

3. Cream ageing and crystallisation

This is the critical step. Cream is held overnight (approximately 12 hours) in a controlled-temperature, gently-agitated tank (the "ageing tank") at 8°C to 12°C. During this period the fat partially crystallises, forming larger fat globules that break more easily during churning.

Key technical points:

• Latent heat of crystallisation — the chemical reaction releases heat, causing temperature rise in the cream. Controlled cooling and gentle agitation are needed to keep temperature uniform.
• Gentle agitation — prevents uneven crystallisation between tank edge (cooler) and centre (warmer). Without it, fat closer to the tank wall over-crystallises.
• Temperature target — too cold and fats are too viscous to migrate and crystallise; too warm and crystallisation is incomplete and yield suffers.

4. Churning — continuous buttermakers

Modern volume buttermaking uses continuous buttermakers (Fritz, Westfalia, Egli, Simon Frères designs) that combine churning, washing and working into a single in-line machine. A well-specified continuous buttermaker has:

• Cream tempering section — preheats or precools incoming cream to a precisely controlled feed temperature, ensuring consistent crystallisation state at the churn inlet
• Controllable cream feed rate — usually with a feedback loop tying churn discharge consistency to feed rate
• Barrel cooling — jacketed barrel to remove latent heat liberated as churning progresses
• Recycle loop — ability to return cream to the ageing tank in the event of downstream stoppage, preventing waste
• Working section — where moisture and salt are worked into the butter, with a brine/water injection system

5. Salting

Salt is generally dosed in water/slurry form into the working section. For salted butter at 1.5–2% added salt this is a metered injection; for unsalted butter the salt injection is simply disabled. Dry salt application is no longer standard practice in continuous operations.

6. Buttermilk handling

Buttermilk (the aqueous phase expelled during churning) can be:

• Partially recycled to the working section when needed
• Pasteurised and sold as cultured buttermilk drink
• Spray dried as buttermilk powder (5–7% fat, useful as a functional ingredient)
• Added back to raw milk silos at small percentages (5%) for reprocessing — reduces wastage but requires care not to contravene finished product specifications

Buttermilk should be passed through a sieve at exit to recover fines and grains for return to the butter stream.

7. Packing

Butter exiting the churn barrel goes either directly to a packing machine or into a buffer tank ahead of packing. For bulk butter, the standard format is 25 kg blocks in coloured polythene liners inside cardboard cartons, sealed, coded, dated and moved to chilled or (more commonly) frozen storage at −18°C or below.

Retail packaging (250 g, 500 g) is done either inline directly after the churn for small-volume operations, or in a separate packing line after tempering of bulk frozen blocks for high-volume operations. Wrapper cleanliness is critical — any external grease on the wrap risks yeast and mould growth and cross-contamination of nearby products.

Yield, Quality and the 16% Moisture Ceiling

The legal 16% moisture limit cannot be exceeded. This makes moisture control the single biggest yield lever in buttermaking. A 1% variation in moisture or salt content is a direct loss of profit / yield — on a 5,000 tonne/year operation this is around £200,000+ per year at typical UK butter prices.

Yield-critical levers:

• Cream fat consistency — tight control of separator output reduces churning variability
• Cream ageing temperature precision — the more consistent the crystallisation state, the more consistent the buttermilk separation
• Cream handling gentleness — over-pumping damages the fat globule membrane (lecithin layer), releasing free fatty acids that are lost to the buttermilk
• Buttermaker tuning — barrel speed, working section pressure, and salt/water injection all affect final moisture
• In-line moisture monitoring — NIR moisture sensors at the working section enable real-time feedback control of water injection

Butter Grading

Butter grading evaluates several parameters and is carried out on each production batch before release:

Sample boxes from each shift are kept until the following day's grading and lab results are available. Once everything matches spec, the batch is released.

Shelf Life and Storage

Typical butter shelf life:

Note: retail shelf life starts from the packing date after thaw/temper, not from the original production date. This makes bulk-frozen storage a flexible inventory management tool for seasonality smoothing.

Microbiological Risk: Yeasts, Moulds and Coliforms

The single biggest microbial risk in butter is yeast and mould spoilage. Yeasts and moulds are ubiquitous in atmospheric air and on surfaces. For high-volume operations, controls include:

• Clean, filtered, over-pressure air in buttermaking and packing rooms (HEPA filtration; positive pressure relative to surrounding areas)
• CIP discipline — thorough cleaning of ageing tanks, churn barrels and working sections; particular attention to seals and dead legs
• Wrapper / packaging cleanliness — any grease on outer wrappers risks yeast/mould growth in storage and contamination of nearby products
• Coliform testing — routine testing as indicator of post-pasteurisation contamination
• Personnel hygiene — gloves, hairnets, footwear protocols enforced strictly

Butter Variants

Frequently Asked Questions

What is butter, technically?

Butter is a water-in-oil emulsion containing at least 80% milk fat and at most 16% water, with optional small additions of salt, lactic culture and (in some markets) annatto colour. The legal definition varies slightly by country but the 80% fat / 16% water benchmark is near-universal.

Why is cream aged before churning?

Ageing at controlled temperature (8–12°C) with gentle agitation for ~12 hours lets the fat partially crystallise into larger globules. These break more easily during churning, giving better yield and a more consistent butter texture. Without ageing, the buttermaking process is harder to control and yield drops measurably.

What is the maximum legal water content of butter?

In most countries the legal maximum is 16% moisture. This limit cannot be exceeded under any circumstance, so even a 1% variation in moisture represents a direct yield loss equivalent to the underfilled water. Tight process control of moisture is consequently the single biggest profit lever in buttermaking.

What is the difference between AMF, butteroil and ghee?

AMF (anhydrous milk fat) and butteroil are essentially the same product — ~99.9% pure butterfat produced via heating, vacuum (to strip volatiles) and centrifugation, either from cream or from butter. Ghee is similar but less refined, made via a simpler boiling and decanting process, and retains more of the brown-milk-solid flavour notes from the heating step.

Why are yeasts and moulds the main spoilage risk?

Yeasts and moulds are airborne and surface-resident, and they thrive in the high-fat, moderate-water environment of butter. Bulk storage at −18°C suppresses them but does not kill them. Once retail-packed and chilled, they resume growth and define the effective shelf life. Air filtration, surface hygiene and packaging cleanliness are the practical controls.

Continuous vs batch buttermaking — which is better?

For high-volume commercial production (above ~5 tonnes/day), continuous buttermakers are the standard — lower labour cost, better consistency, lower yield variability. For artisan and lower-volume production, batch churns remain in use, often as a marketing differentiator. The fundamental chemistry is the same; the engineering and economics differ substantially.

Can buttermilk be reused?

Yes. Buttermilk can be pasteurised and sold as cultured buttermilk drink, spray dried as buttermilk powder (5–7% fat, valued as a functional ingredient), partially recycled to the working section of the buttermaker, or added back to raw milk silos at low percentages (~5%). The choice depends on plant configuration and product mix.

Further reading: John Watson publishes articles on dairy industry topics on LinkedIn. Browse all articles by John Watson on LinkedIn →

Related Downloads

See related: Butter standards / specification, EU Intervention Board (IBAP) forms, Butter lab control record sample, Pearson's Square (cream blending), Milk standardisation (cream separation), Milk separator, all dairy science information, or browse all consultancy services.