Raw Material Requirements:
Fresh grapes are the primary raw material, combined with a 20% sugar solution and 2% tartaric acid. These ingredients ensure the desired sweetness and acidity balance in the final product.
Process Flow:
The production process includes several key stages: raw material selection, preparation, heating for color extraction, juice filtration, blending, clarification, secondary heating, canning and sealing, and finally sterilization and cooling.
Key Process Points:
1. **Raw Material Selection**: Choose fresh, fully matured grapes that are free from rot, mold, and pests. The fruit should have a deep color, strong flavor, high juice content, and be of a quality variety that enhances the overall taste and appearance of the juice.
2. **Raw Material Treatment**: After selection, the grapes are soaked in a 0.3% potassium permanganate solution for 3 minutes to disinfect them. They are then rinsed thoroughly under running water until the rinse water is no longer pink. Once dried, the stems are removed, and the grapes are crushed using a crusher. It's important to avoid crushing the seeds during this step to prevent bitterness.
3. **Heat Extraction**: The crushed grapes are placed in a container and heated to 60–70°C for 15 minutes or to 70°C for 5 minutes to extract the pigments from the skin into the juice. This step is not necessary for white grapes.
4. **Juice Pressing and Filtration**: After color extraction, the juice is pressed using a mechanical press or manually. The resulting juice is then filtered through a mesh screen (0.3–0.5 mm) or a fine velvet bag to remove any suspended solids and impurities.
5. **Blending**: The sugar level in the juice is adjusted to 16% by adding a 20% sugar solution. Additionally, 2% tartaric acid is added at a rate of 3.0 kg per 100 kg of fruit juice to prevent the formation of tartaric acid precipitates. To prepare the 2% metatartaric acid solution, 1.0 kg of tartaric acid is dissolved in 49 kg of water, soaked for 2 hours, stirred continuously, and cooked for 5 minutes. After cooling, the solution is filtered and diluted to 50 kg with ice water to ensure complete dissolution.
6. **Clarification**: A gelatin-tannin method is used for clarification. Add 4–5 grams of tannin per 100 kg of juice, followed by 6–10 grams of gelatin after 8 hours. The temperature should be maintained between 8–12°C. Once the juice is completely clear, the supernatant is siphoned off.
7. **Fine Filtration and Heating**: The clarified juice is passed through a fine filter and then heated to 80–85°C in a pan to remove foam and any remaining impurities.
8. **Filling and Sealing**: The hot juice is poured into sterilized glass bottles, sealed immediately, and the caps are sterilized for 5 minutes before being applied.
9. **Sterilization and Cooling**: The sealed bottles are sterilized in hot water at 85°C for 15 minutes, then cooled gradually by adding cold water in stages until the temperature reaches 35°C. The bottles are then labeled and prepared for storage.
Product Characteristics:
The finished juice has a purple or light purple color, is clear and transparent, and offers a distinct grapefruit flavor with a balanced sweet and sour taste. It should have no off-odors. Over time, small amounts of sediment and tartaric acid crystals may form. The soluble solids content ranges from 15% to 18% as measured by a refractometer, and the total acidity is between 0.4% and 1.0% expressed as tartaric acid.
Notes:
During processing, it’s crucial to avoid contact with iron or copper materials, as they can cause discoloration. For lighter-colored grapes, using cold-pressed juice can help preserve the natural flavor and aroma.
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