Mozzarella Cheese Production

Types of Mozzarella

The Mozzarella Manufacturing Process

1. Milk standardisation and pasteurisation

Mozzarella cheese milk is standardised to a fat-to-casein ratio appropriate for the target product. Full-fat mozzarella typically uses ratios around 0.95–1.05; part-skim runs lower (0.70–0.85). Standardisation is done with a centrifugal separator and blend-back. See our Pearson's Square calculator for the math and milk standardisation by cream removal for the separator approach.

Milk is HTST pasteurised at 72°C/15s (see milk pasteurisation) then cooled to the cheesemaking temperature of 35–38°C. Higher pasteurisation temperatures damage curd structure and reduce stretch quality, so HTST is preferred over high-heat methods.

2. Inoculation and culture

Thermophilic starter cultures (Streptococcus thermophilus with optional Lactobacillus helveticus or L. delbrueckii subsp. bulgaricus) are added to develop lactic acid. Culture choice influences final pH, flavour development and shelf-life characteristics. Inoculation rate: typically 0.5–1.5% direct-vat-set (DVS) culture by milk volume.

3. Coagulation

Rennet (chymosin or microbial coagulant) is dosed at 20–30 mL per 100 L milk. Coagulation takes 25–40 minutes at 35–38°C. Calcium chloride (CaCl₂) is commonly added at 10–20 g/100 L to compensate for calcium losses during pasteurisation and to firm the curd.

4. Cutting and cooking

The coagulum is cut into pea-sized to acorn-sized pieces (~10–15 mm) and cooked to 40–42°C over 20–30 minutes with gentle stirring. Cook temperature and time determine final moisture — key to differentiating fresh from low-moisture variants.

5. Whey drainage and acid development

Whey is drained when curd has reached the target firmness. The curd is then allowed to acidify further on the draining belt or in trolleys until pH drops to 5.1–5.3 (the critical "stretch window"). This is the most timing-sensitive step; pH that's too high gives a tough, rubbery cheese, while too low gives a brittle, crumbly texture.

6. Stretching (pasta filata)

The acidified curd is mixed with hot water at 75–85°C (or hot whey for some operations) and worked mechanically. Casein realigns into long fibres parallel to the working direction, giving mozzarella its characteristic stretch and string. Modern continuous cookers use a screw or paddle system that combines mixing, heating and kneading in one pass.

7. Forming and cooling

Hot stretched curd is extruded into moulds or balls (fresh) or block formers (LMM). It is cooled rapidly in chilled water or chilled brine to set the shape and stop further whey expulsion.

8. Brining

Cooled cheese is brined in 18–23% NaCl solution at 4–10°C for hours to days depending on size and target salt level. For LMM blocks: typically 4–8 hours. For fresh mozzarella balls: 30 minutes to 2 hours. Brine concentration, temperature and time are tightly controlled to hit final salt-in-moisture of 3–5%.

9. Packaging

Fresh mozzarella is packed in brine pouches, plastic tubs or jars with brine. LMM is vacuum-packed in blocks (typically 2.27 kg / 5 lb or 10 kg) or shredded and bagged with anti-caking agents (cellulose, starch). String cheese is extruded, cut, individually wrapped.

Yield and Composition Targets

Typical yield: 10–11 kg mozzarella per 100 kg cheese milk (3.5–4% fat milk). Yield depends critically on:

• Casein recovery — cooking time/temperature and pH at drain
• Fat retention — minimise fat losses to whey by gentle stirring and avoiding over-cooking
• Final moisture — the legal/spec moisture ceiling sets the upper limit; any moisture below ceiling is yield foregone

The most common commercial defect is over-pumping or over-stirring during stretching, which damages the fibre structure, releases fat to the hot water, and reduces both yield and stretch performance.

Functional Properties for Pizza

Pizza performance is judged on three parameters:

• Stretch — ability to form long elastic strings when pulled. Driven by intact casein fibre structure at pH 5.1–5.3 stretch window.
• Melt — smooth flow without graining or oiling. Driven by calcium-casein interaction balance and fat content.
• Browning (Maillard) — controlled browning of the surface. Driven by free amino acids and residual lactose; affected by culture choice and ageing.

Industrial LMM is typically aged 2–3 weeks before use to develop optimal pizza performance — fresh from production it tends to be too elastic and under-developed.

Brine System Design

Mozzarella brining is a significant operational consideration:

• Brine maintenance — saturation point ~26% NaCl at 4°C; operating at 18–23% leaves headroom for milk-protein dilution
• Acid balance — brine pH drifts down over time as lactic acid leaches from cheese; periodic adjustment with food-grade NaOH or partial replacement
• Calcium balance — Ca leaches from cheese and accumulates in brine; needs management to prevent surface defects
• Microbial control — salt concentration above ~18% suppresses most spoilage organisms; cold filtration or UV polish for high-volume systems

Frequently Asked Questions

What is pasta filata?

Pasta filata ("spun-paste") is the family of Italian cheeses including mozzarella, provolone and scamorza in which acidified curd is heated in hot water or whey and stretched/kneaded to develop fibrous, elastic texture. The stretching realigns casein into long parallel fibres that give the characteristic mozzarella stretch and string.

What's the difference between fresh mozzarella and low-moisture mozzarella?

Fresh mozzarella (Fior di Latte) is high-moisture (50–60%), packed in brine, with a 1–3 week shelf life — for salads and fresh consumption. Low-moisture mozzarella (LMM) is 45–52% moisture, block form, vacuum-packed, with 2–3 month shelf life — the industrial pizza standard.

Why does mozzarella stretch?

During the pasta filata stretching step, casein protein realigns into long parallel fibres rather than the random network of typical cheeses. At pH 5.1–5.3 the casein structure is loose enough to flow but cohesive enough to form fibres. Cooling locks this structure in place.

What pH is mozzarella made at?

The critical pH for stretching is 5.1–5.3. Above ~5.4 the cheese is rubbery and won't stretch properly; below ~5.0 it becomes brittle and crumbly. Tight pH control at the draining belt is essential.

What is the yield of mozzarella from milk?

Typical commercial yield is 10–11 kg of mozzarella per 100 kg of standardised cheese milk. See our Van Slyke yield calculator for modelling based on specific milk composition and target moisture.

Why is mozzarella aged before use for pizza?

Fresh-from-production LMM is too elastic and under-developed for pizza. 2–3 weeks of cold ageing allows partial proteolysis that improves melt and browning behaviour. Specialty pizza-cheese producers may age 4–6 weeks.

What causes oiling-off on pizza cheese?

Excessive free oil release during melting is caused by: (a) cooking the cheese too long before pasta filata, damaging fat globule retention; (b) excessive mechanical work during stretching, releasing fat to the hot water; (c) high fat-on-dry-matter combined with insufficient calcium-casein binding; (d) over-ageing.

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

See related: Cheese making fundamentals, Cheese Yield (Van Slyke) calculator, Feta cheese, Blue cheese, Soft cheese & EMC, Pearson's Square (milk standardisation), Milk standardisation (cream removal), Milk pasteurisation, all dairy science information, consultancy services.