HARD AND SEMI-HARD CHEESES

Key technological challenges in hard and semi-hard cheese production

This category covers two production lines: kashar, gouda and edam-type cheeses produced from milk curd and ripened, and block, sliced, toast and pizza-type processed cheeses in which cheese and curd are restructured by heat treatment with emulsifying salts. In these cheeses — where the curd is either stretched (pasta filata) or cooked — the objectives are similar but the root causes of defects differ.

• In ripened cheese: late blowing caused by Clostridium tyrobutyricum spores from silage and soil fermenting lactate into butyric acid and gas; mould and yeast growth on the rind; batch-to-batch variation in coagulation time and yield.
• In block and sliced processed cheese: crumbling during cutting or slices sticking together, hardening throughout shelf life, surface oiling-off and moisture release, crystal formation during storage.
• In pizza and toast types: insufficient or excessive meltability in the oven, oiling-off, blistering, and a rubbery texture after re-melting.

Solution approach

The main variable determining texture in processed cheese is the type and dosage of the emulsifying salt. Phosphate and citrate salts sequester calcium from the calcium paracaseinate network by ion exchange; the casein becomes hydrated, is dispersed by peptisation and emulsifies free fat. The same salts also raise and buffer the pH. As heat treatment and stirring continue, the dispersed casein reforms a network; this thickening, known as creaming, is the foundation of a firm, sliceable body.

• Long-chain polyphosphates have the highest calcium sequestration and creaming potential, steering the product towards a firm block and sliced structure with a clean cut.
• Citrate-dominant blends produce less creaming and are preferred for pizza and toast types that require controlled meltability and flow in the oven.
• Hydrocolloid- and starch-based stabilisers bind free water and support body in high-moisture or vegetable-fat-based formulations.
• In ripened cheese, protection is achieved through a combination of raw-milk quality, bactofugation and preservatives. Lysozyme breaks down the Clostridium cell wall, while natamycin suppresses moulds and yeasts on the surface only.

PROMEL product groups

• Emulsifying salts for sliced and block processed cheese (Promel MS 31, Promel MS 38) — citrate-free, polyphosphate-based; high water binding, firm and non-stick slices.
• Emulsifying salts for pizza, toast and re-melt applications (Promel MS 85, Promel MS 07) — citrate–phosphate based; balancing uniform meltability with clean slicing.
• Corrective and speciality salts (Promel MS 12, Promel MS 92) — pH support for high-acidity raw materials; a citrate-free salt that preserves the granular texture in tulum-type processed cheese.
• Stabiliser systems (Promel Supermix 20, Promel Süpermix 70, Promel M 391, Promel S4020) — water binding, sliceability, stretch and reduced clumping of shredded particles.
• Preservatives (Silvazyme Lysozyme, Silvamycin Natamycin, Promel Silvanisin) — against late blowing, surface mould and spore-related spoilage.
• Rennet, flavouring and colour (Proren Fermented Chymosin, Promel Gouda Aroması, Fla-Pro Tulum Aroması, Promel Beta Carotene EM 5%) — consistent coagulation, mature cheese character and colour standardisation.

Process and formulation tips

• The emulsifying salt is typically used at 0.6–1.3 % of the blend; the maximum P₂O₅ limit set by the applicable food additive regulations must be taken into account for phosphates.
• In sliced products the final pH is typically targeted at 5.4–5.8; a low pH leads to a brittle texture, while a high pH shifts towards a soft and sticky body.
• Young cheese and fresh curd contain intact casein and therefore provide a firm body; ripened cheese offers a weaker body but better meltability due to proteolysis. The raw-material ratio is an integral part of the formulation.
• Cooking temperature and time (typically 68–75 °C) directly affect creaming; in pizza types, prolonged holding reduces performance.
• Lysozyme is added to the cheese milk before coagulation; as it is derived from egg, allergen declaration is required on the label.
• Natamycin is applied to the surface only — by dipping, spraying or coating — and must not be added to the cheese mass (the regulations of the country where the finished product will be marketed should be verified).

Frequently asked questions

Why do slices stick together in sliced cheese?

This is usually due to insufficient creaming, high pH or excessive free water. Switching to a salt with a higher polyphosphate share, lowering the pH or adding a water-binding stabiliser reduces sticking; the slicing temperature should also be checked.

The pizza cheese does not melt sufficiently in the oven — what should be changed?

An excessively firm structure will not melt. Switching to a blend with a higher citrate share, shortening the cooking time and adding some ripened cheese to the raw materials will improve meltability.

White crystals form during storage — what causes this?

These are most often sparingly soluble calcium phosphate or calcium citrate salts. Excessive salt dosage and incomplete dissolution of the salt increase the risk; the blend and dosage should be rebalanced.

Does lysozyme affect ripening cultures?

Lysozyme primarily acts against spore-forming Gram-positive bacteria; lactic cultures are generally more resistant. Nevertheless, since sensitive strains may exist, compatibility with the culture should be verified during pilot production.

Once you share the maturity of your raw-material cheese, target pH and your slicing or melting requirements, the Technofood R&D team will recommend the appropriate emulsifying salt and stabiliser combination; samples and technical data sheets are provided on request for pilot trials.