Cheese Manufacturing

Cheese manufacturing requires precise environmental control across multiple processing stages, from initial milk processing through extended aging periods. The refrigeration system design must accommodate vastly different conditions for cheesemaking areas, pressing rooms, and aging facilities while maintaining strict sanitation standards.

Processing Area Requirements

The primary cheese manufacturing floor operates at 50-55°F (10-13°C) to control bacterial activity during curd formation, cutting, and whey drainage. This temperature range slows acid development while permitting controlled fermentation essential to cheese texture and flavor development.

Air distribution in processing areas must provide gentle, laminar flow to prevent surface drying of exposed curd without creating turbulence that could introduce contaminants. Supply air velocity at work surfaces should not exceed 50 fpm to avoid moisture loss from cheese surfaces during formation stages.

Humidity control in processing areas maintains 65-75% RH to prevent excessive moisture loss from fresh curd while avoiding condensation on equipment surfaces. This narrow operating range requires precise control of both supply air temperature and moisture content.

The refrigeration system must handle substantial sensible and latent loads from steam-jacketed vats, hot whey drainage, and periodic CIP (clean-in-place) operations using 160-180°F sanitizing solutions. Load calculation must account for these cyclical heat inputs that can exceed 100,000 BTU/hr per vat during processing.

Pressing Room Conditions

Pressing rooms operate at 55-60°F (13-16°C) with controlled humidity of 70-80% RH during the mechanical dewatering phase. This environment allows continued whey expulsion while preventing surface case hardening that would trap excessive moisture in the cheese interior.

The refrigeration system must provide stable conditions despite fluctuating loads from batch processing schedules. Temperature swing should not exceed ±2°F to ensure consistent moisture removal rates across production batches.

Air movement in pressing rooms should be minimal, with air changes limited to 4-6 ACH to maintain environment without creating drafts that cause uneven drying. Supply air should be introduced at low velocity through perforated diffusers or textile ducts.

Aging Room Environmental Control

Cheese aging rooms represent the most demanding refrigeration application in dairy processing, requiring simultaneous control of temperature, humidity, and air velocity over extended periods ranging from weeks to years.

Temperature Control Requirements

Aging temperature directly affects enzymatic and bacterial activity that develops cheese flavor, texture, and appearance. The refrigeration system must maintain exceptionally tight temperature control, typically ±1°F or better, to ensure consistent product development.

Temperature variation within the aging room should not exceed 2°F between any two points in the space. This requires careful attention to air distribution, thermal insulation, and refrigeration equipment staging to avoid cycling-induced temperature swings.

Most aging applications use glycol or brine systems operating at 20-25°F (-7 to -4°C) to provide adequate temperature differential for precise control without excessive refrigerant migration or oil return issues common in direct-expansion systems.

Humidity Control Systems

Humidity control in aging rooms prevents both excessive moisture loss (weight shrinkage and economic loss) and excessive moisture retention (surface defects and mold growth). The target humidity varies by cheese type but typically ranges from 80-95% RH.

High-limit humidity control uses refrigeration coil face velocity and coil temperature to extract moisture without overcooling the space. Coil face velocity should not exceed 400 fpm to maintain stable condensate removal, with entering air temperature at least 5°F above coil surface temperature to prevent surface flooding.

Low-limit humidity control employs humidification systems when natural moisture release from aging cheese proves insufficient. Ultrasonic atomizing humidifiers provide the most precise control without introducing excessive thermal load, though evaporative pad systems offer simpler maintenance in less demanding applications.

Humidity stratification must be controlled through proper air distribution. Supply air should be introduced at the ceiling level and directed toward cheese storage areas with sufficient velocity (50-75 fpm at cheese surfaces) to ensure uniform conditions without causing excessive evaporation.

Air Circulation Requirements

Air circulation in aging rooms serves multiple functions: maintaining uniform temperature and humidity, controlling surface mold growth, and promoting rind development. Air movement requirements vary significantly by cheese type and aging protocol.

Natural-rind cheeses require gentle air movement of 10-20 fpm at cheese surfaces to promote even drying and controlled mold colonization. Higher velocities cause excessive moisture loss and irregular rind formation.

Waxed or plastic-wrapped cheeses tolerate higher air velocities since surface evaporation is controlled by the barrier coating. Air velocities up to 50 fpm are acceptable and help maintain uniform temperature throughout stacked cheese inventory.

Air circulation systems must operate continuously during aging to prevent stratification and local temperature variations. Variable-speed fans allow adjustment of circulation rates to match changing requirements as cheese ages and releases decreasing amounts of metabolic heat.

Cheese Type Specific Requirements

Different cheese varieties require distinctly different aging environments based on moisture content, salt concentration, microbial cultures, and desired aging characteristics.

Swiss Cheese Eye Development

Swiss cheese requires specialized two-stage aging with precise temperature control to develop characteristic eye formation. Initial warm room aging at 70-75°F (21-24°C) for 4-6 weeks promotes propionic acid bacterial activity and CO₂ production that creates eyes.

The warm room refrigeration system must maintain temperatures substantially above ambient while controlling humidity at 80-85% RH. This typically requires independent climate control separate from standard aging rooms, with both heating and cooling capacity to maintain setpoint regardless of outdoor conditions.

Following eye development, Swiss cheese transfers to cold rooms at 35-40°F (2-4°C) for final aging, which may extend 6-12 months. This temperature transition must occur gradually over 3-5 days to prevent thermal shock that could cause cracking or irregular eye distribution.

Surface-Ripened Cheese Requirements

Surface-ripened cheeses including Brie, Camembert, and similar varieties require the highest humidity levels in cheese manufacturing, typically 90-95% RH, to support growth of Penicillium candidum and related surface molds.

The refrigeration system must prevent condensation on room surfaces while maintaining these elevated humidity levels. This requires insulation with vapor retarders on the warm side and careful attention to surface temperatures of all interior elements.

Dehumidification must be minimized during surface-ripening phases. Some facilities employ bypass dampers around cooling coils or multiple refrigeration circuits with different coil temperatures to allow humidity control independent of temperature control.

Air circulation must be extremely gentle (10-15 fpm) to prevent desiccation of developing mold cultures while ensuring uniform distribution of mold spores across all cheese surfaces.

Load Calculation Considerations

Refrigeration load calculations for cheese aging facilities must account for multiple simultaneous heat sources with widely varying magnitudes and duty cycles.

Product load includes both sensible heat removal from warm cheese entering the aging room and respiratory heat from ongoing bacterial and enzymatic activity within aging cheese. Fresh cheese enters aging rooms at 55-65°F and must be cooled to aging temperature, representing 25-30 BTU/lb of product sensible load.

Respiratory heat production varies by cheese type and age, ranging from 0.5-2.0 BTU/lb-day for hard cheeses to 3-5 BTU/lb-day for soft, high-moisture varieties during peak metabolic activity. This heat production decreases as cheese ages and microbial activity declines.

Infiltration load in aging rooms can be substantial due to frequent access for turning, inspection, and product movement. Using vestibule entries with properly sequenced doors and air curtains reduces this load by 40-60% compared to single-door entries.

Personnel load includes both sensible and latent heat from workers performing turning, cleaning, and quality inspection operations. Typical values are 450 BTU/hr sensible and 200 BTU/hr latent per person for moderate activity levels in cool environments.

Lighting load should use LED fixtures designed for refrigerated environments, providing 20-30 footcandles for general aging storage and 50-75 footcandles in inspection areas. Modern LED systems contribute only 0.5-1.0 watts per square foot compared to 2-4 watts for older fluorescent or HID systems.

Refrigeration System Design

Cheese aging facilities most commonly employ indirect refrigeration using secondary coolants (glycol or calcium chloride brine) circulated to air-handling units serving aging rooms. This approach provides superior temperature control compared to direct-expansion systems while simplifying refrigerant management and leak detection.

Central chillers using ammonia refrigerant offer the most efficient long-term operation for facilities with substantial refrigeration loads exceeding 100 tons. Ammonia’s superior thermodynamic properties and zero GWP make it the preferred choice despite higher initial installation costs and regulatory requirements.

For smaller operations under 50 tons, packaged glycol chillers using low-GWP refrigerants (R-513A, R-515B, or R-1234ze) provide adequate performance with reduced regulatory burden. These systems sacrifice some efficiency compared to ammonia but offer simplified installation and operation.

Air-handling units serving aging rooms should incorporate multiple refrigeration circuits with independent control to allow staging that prevents excessive cycling. Minimum of three stages provides acceptable control; four or more stages enables optimal efficiency across varying load conditions.

Evaporator coil selection must balance heat transfer effectiveness against air-side pressure drop and moisture removal characteristics. Coil face velocity should not exceed 400 fpm, requiring larger coil face areas than typical comfort cooling applications.

Sanitation and Cleanability

All refrigeration equipment and ductwork in cheese processing and aging areas must be designed for periodic cleaning with high-pressure washdown and chemical sanitizers. This requirement significantly impacts equipment selection and installation methods.

Evaporator coils must use stainless steel construction (300-series minimum) with sloped drain pans and adequate drainage capacity to handle both condensate removal and washdown water. Drain pans require pitch of minimum 1/8 inch per foot toward drain connections.

Air distribution components including ductwork, diffusers, and grilles must be either removable for cleaning or constructed from stainless steel with smooth, crevice-free interior surfaces. Ductwork joints should use welded construction rather than standing seams that can harbor bacterial growth.

Equipment supports, hangers, and penetrations must be designed to prevent water accumulation and facilitate cleaning access. All horizontal surfaces should be sloped or eliminated to prevent standing water that promotes bacterial growth.

Controls and Monitoring

Cheese aging rooms require more sophisticated environmental monitoring and control than typical refrigerated storage due to the extended aging periods and high product value. Temperature and humidity sensors should be placed at multiple locations throughout aging rooms to detect stratification or local variations.

Data logging systems recording temperature and humidity at 15-minute intervals provide documentation of aging conditions essential for quality control and HACCP compliance. These records allow correlation of environmental deviations with product quality issues.

Alarm systems should notify operators of temperature excursions exceeding ±2°F from setpoint or humidity variations beyond ±5% RH. Extended excursions beyond these limits can result in product defects not apparent until final aging completion months later.

Remote monitoring capability allows 24/7 oversight of aging conditions without continuous on-site staffing. Cloud-based systems provide access to current conditions and historical data from any internet-connected device.

Automated defrost controls must sequence defrost cycles during periods of minimal production impact while ensuring adequate frost removal to maintain heat transfer. Demand defrost based on measured pressure drop across coils or differential temperature provides more efficient operation than time-based schedules.

Sections