Processing Technology and Process Flow of Citrus Concentrate

I. Process Flow

1. Raw Juice

Citrus raw material → Inspection and acceptance → Temporary storage → Washing → Fruit selection → Whole fruit juicing → Juice → Filtration → Sterilization → Raw juice

1. Frozen Concentrated Juice

Raw juice → Concentration and cooling → Filling → Frozen concentrated juice

II. Key Operational Points

(1) Selection and Intermediate Storage of Raw Materials: When selecting raw materials, choose varieties that do not impart bitterness to the citrus juice during processing. During intermediate storage, damaged or unsuitable fruits must be removed. Additionally, rapid sample testing should be conducted to assess the quality of juice produced from these materials before storing them in an intermediate storage facility.

(2) Sorting and Washing: It is preferable to use roller sorting machines for sorting. Add 1%–2% sodium hydroxide and a disinfectant to the washing water. The fruits should first undergo a brief soak, then be cleaned by rotating brush rollers and rinsed with spray water. The spray water should be chlorinated, with a chlorine content of 10–30 mg/L. Finally, rinse the fruits with clean water.

(3) Oil Removal: After washing, the fruits enter a needle-type oil extractor, where the peel is punctured, releasing oil from the oil glands. The oil is carried away by the spray water, and a disc centrifuge separates the sweet orange oil from the oil-water emulsion. The residual liquid is recycled through pipes back into the oil extractor for reuse as spray water.

(4) Juice Extraction: Conventional juice extractors for pome fruits, stone fruits, or berries are unsuitable for extracting juice from de-oiled citrus fruits. Currently, citrus juice extraction employs machines such as the In-Line extractor, Brown extractor, and Anderson extractor. Care must be taken to prevent peel oil, albedo, and segment membranes from entering the juice, as these not only increase bitterness but also produce off-flavors upon heating. Seed crushing should also be avoided.

(5) Pulp Removal: The raw sweet orange juice from the extractor contains pulp, which must be filtered out using a pulper or similar equipment to remove larger pulp particles.

(6) Deaeration: Citrus juice is highly susceptible to oxidation, leading to changes in color, flavor, and loss of vitamin C. Deaeration is crucial for maintaining juice quality. Equipment such as centrifugal spray, pressure spray, or thin-film flow systems can be used for deaeration.

(7) Pasteurization: To ensure microbial stability alone, a pasteurization temperature of 71–72°C with the corresponding holding time is sufficient. However, to inactivate pectin methylesterase and ensure colloidal stability, a higher temperature of 86–99°C and the corresponding holding time are required.

(8) Concentration: Citrus juice concentrate is primarily produced using freeze concentration, with the soluble solids content concentrated to 65%.

(9) Packaging and Storage: After freeze concentration at -5 to -8°C, the citrus concentrate is packed into polyethylene-lined barrels, sealed, and immediately stored in a cold storage facility at -25 to -30°C. No further pasteurization is needed, eliminating the risk of heat-induced quality degradation.