Food freezing technology serves as a core component of the modern food industry. It not only drastically extends food shelf life but also retains maximum nutritional value and original flavor. Among various freezing equipment, tunnel freezers are highly favored in the industry for their efficient and uniform freezing performance.
Step 1: Vegetable Cleaning：As a critical pretreatment before quick freezing, cleaning aims to remove surface soil and impurities while minimizing microbial contamination risks. Common methods include water rinsing and bubble cleaning. The duration and intensity of cleaning should be adjusted based on vegetable types to prevent tissue damage. Post-cleaning, a preliminary screening is conducted to ensure consistent quality of raw materials for subsequent processing.
Step 2: Vegetable Cutting：This step involves cutting cleaned vegetables into small pieces or slices suitable for quick freezing, requiring high process precision. Cutting methods and sizes are determined by vegetable varieties and final product forms. Scientific cutting not only improves freezing efficiency but also preserves the vegetables' appearance and texture after freezing.
Step 3: Blanching Treatment：Blanching uses short-term high-temperature processing to inhibit enzyme activity in vegetables, preventing browning and flavor loss during subsequent processing and storage. Precise control of water temperature (usually 80-90℃) and duration (a few seconds to several minutes) is required to effectively inhibit enzymes without compromising taste and nutrients.
Step 4: Cooling and Draining：Blanched vegetables must be rapidly cooled to room temperature to avoid over-cooking from residual heat. Excess moisture is then removed via centrifugal dehydration or natural draining. This step is critical for subsequent freezing, as excessive moisture leads to large ice crystals that damage vegetable cell structures.
Step 5: Feeding into CBFI Tunnel Mesh Belt Freezer：The CBFI tunnel mesh belt quick freezer is a high-efficiency device that achieves rapid freezing via low-temperature air flow. To ensure uniform freezing, drained vegetables are evenly spread on the conveyor belt without stacking, which transports them into the freezing tunnel for low-temperature quick freezing.
Step 6: Quick Freezing Process：Inside the CBFI tunnel freezer, vegetables are exposed to extremely low temperatures (usually below -30℃), with their core temperature dropping rapidly below -18℃. This rapid freezing induces the formation of small, evenly distributed ice crystals in cells, reducing pressure on cell walls and preserving the original structure and nutrients.
Step 7: Nutrient Retention：The formation of small ice crystals is the core of quick freezing technology. By optimizing freezing speed and temperature parameters, the CBFI tunnel freezer maximizes nutrient retention without damaging cell structures, improving frozen vegetable quality and meeting consumers' demands for healthy and delicious food.
The formation of small ice crystals directly determines the quality and nutritional value of frozen vegetables, serving as the core of the quick freezing process. Its formation is closely related to freezing rate and equipment performance, with specific mechanisms as follows:
1. Changes in Intracellular Water State：At room temperature, water in vegetable cells exists in a liquid state. As temperature drops, water begins to solidify into ice. Slow freezing causes water to accumulate into large ice crystals, which squeeze and damage cell walls, resulting in poor texture and nutrient loss after thawing.
2. Function of Rapid Freezing：Rapid freezing achieves an abrupt temperature drop, inhibiting intracellular water migration and accumulation, thus forming small, uniform ice crystals. These crystals exert minimal pressure on cell walls without damaging the structure, fully preserving the vegetable's original form, texture and nutrients.
3. Technical Implementation Details：The CBFI tunnel freezer ensures uniform cooling of vegetable surfaces and interiors by optimizing air flow speed and direction. Meanwhile, the extremely low temperature setting (below -30℃) accelerates the freezing process, shortening the time window for ice crystal formation and preventing large crystal growth.
4. Final Effects：This quick freezing technology stabilizes the core temperature of vegetables below -18℃, ensuring the formation of small ice crystals. It not only maintains cell structure integrity but also maximizes the retention of key nutrients such as vitamins and minerals.
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