Processing Technology for Animal Plasma and Blood Cells

Processing Technology for Animal Plasma and Blood Cells

Centered on the core concept of "efficient utilization of all components", the processing technology for animal plasma and blood cells converts animal blood (mainly from pigs, cattle, and sheep) into high-value-added products such as plasma protein powder, blood cell powder, and heme through processes including anticoagulation, separation and purification, and drying and forming. Throughout the process, strict control of hygiene and temperature is required to avoid the destruction of nutritional components. The detailed process is as follows:

I. Pretreatment Stage: Blood Collection and Anticoagulation

This stage is the foundation for subsequent processing, with the core goal of preventing blood coagulation and removing impurities.

1. Blood Collection

Specialized blood collection equipment (e.g., automatic blood collection systems) is used to collect blood within 1 hour after animal slaughter to prevent natural coagulation. During collection, anticoagulants must be added simultaneously: sodium citrate (commonly used, added at 0.8%-1.2% of the total blood volume) or EDTA (added at 0.3%-0.5% of the total blood volume). The mixture is stirred through pipelines to ensure uniform distribution of the anticoagulant.

The collected blood needs to be filtered through an 80-100 mesh filter to remove mechanical impurities such as hair and tissue debris, preventing blockage of subsequent separation equipment.

2. Low-Temperature Temporary Storage

The anticoagulated blood is immediately transferred to a low-temperature storage tank at 2-8°C for temporary storage, with a maximum storage time of no more than 24 hours. This slows down microbial reproduction and enzymatic hydrolysis reactions, and preserves the activity of plasma proteins.

II. Core Separation Stage: Separation of Plasma and Blood Cells

Efficient separation of plasma and blood cells is achieved using centrifugal force, which is a key link in the process. Common equipment includes tubular centrifuges or disc centrifuges.

1. Centrifugal Separation

Low-temperature blood is pumped into the centrifuge:

For tubular centrifuges: Rotational speed is 15,000-20,000 rpm, centrifugal force is 12,000-15,000 G;

For disc centrifuges: Rotational speed is 6,000-8,000 rpm, centrifugal force is 3,000-5,000 G.

Under high-speed centrifugation:

Blood cells (red blood cells, white blood cells, platelets) with higher density are thrown to the inner wall of the centrifuge, forming a solid layer and being discharged through the slag discharge port;

Plasma (containing albumin, immunoglobulin, and fibrinogen) with lower density remains in the center and is continuously discharged through the overflow port, entering the subsequent processing stage.

Purity testing is required after separation: The residual rate of blood cells in plasma should be ≤ 0.5% (no visible red sediment to the naked eye), and the entrainment rate of plasma in blood cells should be ≤ 5% to ensure no cross-contamination between the two.

2. Split-Route Temporary Storage

The separated plasma is transferred to a sterile storage tank at 3-5°C. For blood cells, 0.9% normal saline is added at a ratio of blood cells to normal saline of 1:1 for washing. Centrifugation is performed again (rotational speed: 12,000 rpm) to remove residual plasma, resulting in "clean blood cells" and reducing protein loss.

III. Plasma Processing Subprocess: From Liquid Plasma to Finished Products

Plasma is mainly processed into plasma protein powder; for some high-end demands, immunoglobulin is further purified. The process consists of either two steps ("concentration → drying") or three steps ("purification → drying").

1. Conventional Process: Production of Plasma Protein Powder

(1) Vacuum Concentration

Liquid plasma is pumped into a double-effect vacuum concentrator (vacuum degree: -0.092 MPa to -0.095 MPa, temperature: 50-55°C). Low-temperature evaporation is used to remove water, increasing the solid content of plasma from 6%-8% to 25%-30% and avoiding protein denaturation caused by high temperatures (e.g., the denaturation temperature of albumin is approximately 60°C).

The solid content must be monitored in real-time during concentration (using a refractometer), and the process proceeds to the next step once the standard is met.

(2) Spray Drying

The concentrated plasma is fed into a centrifugal spray drying tower (inlet air temperature: 180-200°C, outlet air temperature: 80-85°C). Under high-pressure atomization (atomizer rotational speed: 20,000-25,000 rpm), the plasma forms tiny droplets, which quickly come into contact with hot air and are instantly dried into powder.

The dried plasma protein powder is cooled to room temperature and sieved through a 100-mesh filter to remove agglomerates. The final product has a moisture content of ≤ 5% and a protein content of ≥ 75% (in line with the national standard GB/T 25166-2010), and can be used as a feed additive or food protein fortifier.

2. High-End Process: Purification of Immunoglobulin

(1) Salting-Out Precipitation

Ammonium sulfate (concentration: 40%-45%) is added to liquid plasma, and the pH is adjusted to 4.8-5.2 (isoelectric point precipitation method) to precipitate immunoglobulin. After standing for 2-3 hours, centrifugation is performed (rotational speed: 8,000 rpm) to collect the precipitate.

(2) Dialysis and Desalination

The precipitate is dissolved in 0.02 mol/L phosphate buffer, transferred to a dialysis bag (molecular weight cutoff: 10,000 Da), and dialyzed in the buffer for 24 hours to remove residual ammonium sulfate, obtaining crude immunoglobulin.

(3) Freeze-Drying

The crude product is transferred to a freeze dryer (vacuum degree: ≤ 10 Pa, pre-freezing at -40°C for 4 hours, then heating to 25°C for sublimation drying for 12 hours). This avoids the destruction of immune activity by high temperatures. The final product has an immunoglobulin purity of ≥ 90% and is used in the biomedical field.

IV. Blood Cell Processing Subprocess: From Clean Blood Cells to Finished Products

Blood cells are mainly processed into blood cell powder or used for heme extraction; the former has a simple process, while the latter has higher added value.

1. Conventional Process: Production of Blood Cell Powder

(1) Enzymatic Hydrolysis (Optional)

To improve the solubility of blood cell powder, protease (e.g., neutral protease, added at 0.3%-0.5%) is added to clean blood cells. Enzymatic hydrolysis is carried out at 50-55°C and pH 7.0 for 2-3 hours to decompose macromolecular hemoglobin into small molecular peptides. After enzymatic hydrolysis, the enzyme is inactivated with hot water at 90°C for 10 minutes.

(2) Spray Drying

The enzymatically hydrolyzed blood cells (or unhydrolyzed clean blood cells) are directly spray-dried (parameters same as plasma drying: inlet air temperature 170-190°C, outlet air temperature 75-80°C). The dried blood cell powder has a moisture content of ≤ 6%, a protein content of ≥ 80%, and is rich in iron (iron content ≥ 20 mg/100 g). It can be used as a feed iron supplement or raw material for food pigments.

2. High-End Process: Heme Extraction

(1) Hemolysis and Acidification

Deionized water (3 times the volume of blood cells) is added to clean blood cells, and the mixture is stirred for 30 minutes to achieve hemolysis (breaking red blood cell membranes to release hemoglobin). Dilute hydrochloric acid is then added to adjust the pH to 2.0-2.5, causing hemoglobin to denature and precipitate.

(2) Centrifugal Collection and Purification

The denatured hemoglobin is centrifuged (rotational speed: 10,000 rpm) to collect the precipitate. The precipitate is washed 2-3 times with acetone (ratio of precipitate to acetone: 1:5) to remove fats and impurities, obtaining crude heme. Further separation is performed via column chromatography (using a silica gel chromatography column) to obtain heme crystals with a purity of ≥ 95%, which are used in medicine (anti-anemia drugs) or food additives (natural pigments).

V. Key Control Points

1. Hygiene Control

All equipment (blood collection pipelines, centrifuges, drying towers) must be sterilized with high-pressure steam at 121°C for 30 minutes or disinfected by wiping with 75% alcohol to avoid microbial contamination (total bacterial count of finished products ≤ 1,000 cfu/g, Escherichia coli not detected).

2. Temperature Control

Low-temperature processing is maintained throughout the process: blood temporary storage at 2-8°C, concentration at 50-55°C, and drying outlet air temperature ≤ 85°C. This prevents protein denaturation and nutrient loss (e.g., immunoglobulin activity retention rate ≥ 80%).

3. Moisture Control

Finished products must be quickly packaged (using vacuum aluminum foil bags) after drying to ensure the moisture content of plasma protein powder is ≤ 5% and that of blood cell powder is ≤ 6%. This avoids moisture absorption and agglomeration, and extends the shelf life (6-12 months at room temperature).

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