Positive vs. Negative Abatement: Correct Use

Blast chilling involves rapidly cooling the core of cooked foods to approximately +3°C, usually within 90 minutes. This process stabilizes the product, making it safe for refrigerator storage, without compromising its taste, color, or nutritional value.

Blast freezing, on the other hand, is a rapid freezing process that brings the internal temperature of the food to around –18°C in a few hours (generally less than 4). It is designed for long-term storage in the freezer, preserving consistency, structure, and aromas.

Both methods are achieved using blast chillers . They differ in terms of final temperatures and cooling times, but they share a common goal: protecting the quality of the food.

Rapid cooling promotes the formation of micro ice crystals, which are much less harmful than the macrocrystals produced by slow freezing. This prevents cell rupture and preserves the organoleptic properties.

Comparison between positive and negative abatement: timing, effects and applications

Blast freezing allows you to rapidly bring the core of food to +3°C in about 90 minutes, making it ideal for cooked dishes that will be stored in the refrigerator. Blast freezing, on the other hand, lowers the temperature to -18°C in about 4 hours, making it perfect for freezing meat, fish, and dough intended for long-term storage. Rapid cooling promotes the formation of micro-ice crystals, which preserve the structure, texture, and freshness of food. Conversely, slow freezing—like in a home freezer—generates macro-crystals that damage tissue and compromise quality and flavor. Both methods effectively block bacterial growth during cooling.

Not all foods react the same way. Some—like creams, sauces, or mayonnaise—cannot tolerate deep freezing without deterioration and require blast freezing. Conversely, more compact or whole products—like meat, fish, or leavened dough—benefit fully from blast freezing, which ensures their long-term preservation.

The latest generation blast chillers offer pre-set programs based on the type of food:

• Soft: gentle cooling to approximately 0°C for fragile preparations,
• Hard: faster and deeper cycle, up to –12 °C, for large or dense portions,
• Turbo: Designed for continuous or high-intensity production.

In addition to these, there are advanced functions such as controlled defrosting, automatic temperature maintenance, and in some models, assisted leavening or low-temperature pasteurization.

Areas of use of the blast chiller

Catering and gastronomy

In professional kitchens of restaurants, caterers, and delicatessens, a blast chiller is an indispensable tool for streamlining production. It allows dishes to be prepared in advance, stored safely in accordance with HACCP regulations, and speeds up service. It is also mandatory in all businesses serving raw fish, such as sushi bars, to ensure the elimination of microbiological risks (e.g., Anisakis).

Pastry : In pastry shops, blast chilling is used for desserts, semi-finished products, and leavened products. Rapid cooling allows, for example, easy removal of desserts from silicone molds and efficient management of pre-leavened or pre-baked products, optimizing time, quality, and preservation.

Ice Cream : In the world of artisanal ice cream, immediate cooling after churning is essential. Blast freezing stabilizes the product, maintains the overrun (the amount of air incorporated), and creates a compact surface that prevents deflation, ensuring optimal creaminess and structure.

Breadmaking : In modern bakeries and ovens, blast chillers are used to preserve raw dough or pre-leavened baked goods. This eliminates night shifts, improves production management, and offers a variety of ready-to-bake breads, pizzas, and focaccias, taking full advantage of refrigeration technology.

Food industry : At the industrial level, thermal shock is an integral part of production lines for freezing and pasteurizing foods on a large scale. Dedicated systems handle large volumes of raw materials and semi-finished products, ensuring process consistency, hygiene safety, and compliance with supply chain regulations.

Medical and biotechnology sectors : Specialized blast chillers exist for biomedical and pharmaceutical use, capable of rapidly reducing biological samples to very low temperatures (down to –70°C) through forced convection. These systems are designed to preserve the integrity of tissues, reagents, and sensitive materials.

Home use : In recent years, compact or built-in models for home use have also been introduced. These are small blast chillers (capacity 1–2 trays) capable of rapid freezing down to –18°C using cold air at –40°C. They offer the same hygienic and nutritional benefits as professional versions and help families reduce waste, improve food preservation, and ensure greater food safety at home.

Safety, hygiene, and compliance regulations: what you need to know

For proper use of the blast chiller, it is essential to follow a HACCP self-monitoring plan, recording every blast chilling cycle performed. Owning a blast chiller is not mandatory, but the procedure is mandatory, which must be documented by completing specific forms for each product processed. It is also good practice to regularly check the calibration of the probes, the correct closing of the doors, and the general condition of the machine, to ensure safety and reliability.

According to EC Regulation 852/2004, foods intended for consumption or storage at low temperatures must be cooled "as quickly as possible" after cooking, to a safe temperature. EC Regulation 853/2004 supplements these guidelines, particularly for the treatment of raw fish. Ministerial Circular No. 10/1992 also establishes that fish intended for raw consumption (e.g., sushi or carpaccio) must be kept at at least -20°C for at least 24 hours, to eliminate the risk of parasites such as anisakis.

The blast chiller must be used within the environmental conditions indicated by the manufacturer, such as an external temperature no higher than 32–40°C and good ventilation of the surrounding space. It is important not to overload the appliance, distributing the food evenly inside, and allowing very hot foods to cool slightly before placing them inside to avoid thermal shock or damage to the system.

To ensure optimal performance and hygiene, it is necessary to regularly defrost and sanitize the interior of the appliance. Some models are equipped with UV lamps to reduce bacterial load. Surfaces, shelves, and gaskets should be cleaned with neutral detergents suitable for stainless steel. Furthermore, it is advisable to schedule periodic maintenance (checking the refrigeration circuit, filters, and fans), always relying on qualified personnel. Ensure the blast chiller is CE marked and compliant with European directives on machinery and refrigeration systems. Also check national regulations regarding electrical safety and the management of refrigerant gases. During installation, it is important to comply with the requirements regarding electrical connections, grounding, and to leave adequate space for ventilation and maintenance.