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Quick freezing is a rapid cryopreservation technique used to preserve the quality of fruits and vegetables. Quick-frozen produce is processed by first freezing the raw materials, then storing them at temperatures between -18°C and -20°C for later use. This method is considered one of the most effective ways to maintain the original flavor, texture, and nutritional value of fresh produce in modern food preservation technology.
First, the raw materials used for quick-freezing must be fully matured, with rich color, aroma, and taste. The produce should have a crisp texture, no signs of pests or diseases, mold, yellowing, or mechanical damage. Ideally, the fruits and vegetables should be harvested on the same day and processed immediately to ensure the highest quality.
Second, after harvesting, the produce often carries heat from the atmosphere and respiration. To achieve efficient freezing, pre-cooling is essential before the quick-freeze process. This can be done through air cooling using fans or water cooling by soaking or spraying with cold water.
Third, the surfaces of cleaned fruits and vegetables may still contain dirt, dust, or soil. To meet hygiene standards, thorough cleaning is necessary before freezing. Since these products are not washed again before consumption, this step is crucial. Cleaning can be done manually, with washing machines (such as rotary drums or vibratory belt washers), or high-pressure water jets.
Fourth, some fruits and vegetables need to be peeled, trimmed, or cut into uniform sizes for packaging and freezing. Vegetables are typically sliced into pieces, strips, cubes, or slices, ensuring even thickness and size. Berries, however, are usually frozen whole to prevent juice loss.
Fifth, blanching is commonly used in the processing of frozen vegetables. It helps deactivate enzymes, soften fibrous tissues, and remove strong flavors. Not all vegetables require blanching; those with high fiber content, such as beans or cauliflower, benefit from it. On the other hand, vegetables like green peppers or cucumbers should avoid blanching to maintain their crispness. Blanching is typically done at 90–100°C, with the product reaching at least 70°C. Afterward, they are cooled quickly with cold water to around 10–12°C.
Sixth, after cutting or blanching, vegetables often retain excess moisture. If not removed, this can cause clumping during freezing, which hinders the process. Draining is essential. Methods include natural drying in baskets, using centrifugal dryers, or vibrating screens.
Seventh, once drained, the vegetables must be frozen quickly. Rapid freezing ensures that ice crystals form finely within the cells, preserving the structure and quality. This is typically done at temperatures between -25°C and -35°C, followed by proper packaging and storage.
Eighth, packaging plays a key role in maintaining the quality of frozen produce. It prevents moisture loss, oxidation, and contamination. Common packaging materials include cardboard boxes, plastic bags, and vacuum-sealed containers. Packaging sizes vary depending on the market—individual portions may be 0.5 kg or 1 kg, while bulk orders for restaurants might be 5–10 kg. Once packaged, the products should be stored at -18°C. Storage duration varies by type: beans and kale can last up to 8 months, while carrots and pumpkins may stay fresh for up to 24 months.