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Product Overview
Papain, also known as papaya enzyme, is a proteolytic enzyme. It is a low-specificity protease found in papaya (Carica papaya), widely present in the roots, stems, leaves, and fruit of papaya, with the highest concentration in the unripe latex. The active center of papain contains cysteine and is classified as a thiol protease. It is known for its high enzyme activity, good heat stability, and natural safety, making it widely used in food, pharmaceuticals, feed, daily chemicals, leather, and textile industries.
Chemical Properties
Papain is a protease capable of breaking down proteins in acidic, neutral, and alkaline environments. It appears as a white to light yellow powder with slight hygroscopicity. Papain dissolves in water and glycerin, producing a colorless or light yellow solution, sometimes milky. It is almost insoluble in organic solvents like ethanol, chloroform, and ether. Papain is a thiol (-SH) endopeptidase, exhibiting both protease and esterase activities, with broad specificity and strong hydrolytic ability on proteins, polypeptides, esters, and amides, though it cannot hydrolyze peptones. The optimal pH range for papain is 6-7 (generally effective between 3-9.5), and it functions in neutral to slightly acidic conditions, with an isoelectric point (pI) of 8.75. The optimal temperature is 55-65°C (generally active between 10-85°C), and it has strong heat resistance, remaining active at 90°C. It is inhibited by oxidizing agents and activated by reducing substances.
According to the *GB 2760-2011 National Food Safety Standard for Food Additive Use*, papain can be used as a processing aid in the food industry (as an enzyme preparation). Generally, it should be removed before the final product is made (except where residual levels are specified).
Papain is mainly used in beer chill-proofing (hydrolyzing proteins in beer to prevent cloudiness after refrigeration), meat tenderizing (hydrolyzing muscle proteins and collagen to soften meat), pre-cooking cereal preparation, hydrolyzing proteins, and producing meat flavors. Its use in beer chill-proofing and meat tenderizing is more widespread than other proteases. The typical dosage is 1-4 mg/kg to promote gluten breakdown in biscuits, making the final product softer. Multiple proteases can be used for meat tenderizing, as shown in the following comparison table.
By measuring the enzyme activity of papain in tenderizer powder, the quality of the tenderizer can be assessed. The tenderizer powder is dissolved in hydrochloric acid cysteine solution, and the mixture is reacted with a casein solution for 10 minutes. The amount of tyrosine produced in the reaction is measured by UV spectrophotometry. This method offers good accuracy and reproducibility. The enzyme activity unit is defined as the amount of sample required to hydrolyze casein and produce 1 µg of tyrosine per minute.
Papain Production Process
Papain is derived from the unripe fruit of papaya through a process involving latex extraction, coagulation, sedimentation, and drying, resulting in a crude product. This crude product is primarily used in industrial applications. There are three main production methods for papain: direct hot air drying, spray drying, and membrane separation freeze-drying.
Direct Drying
This method is relatively simple and quick, but it produces a crude enzyme with many impurities, poor color, and microbial contamination. The enzyme activity is also low, ranging from 600,000 to 800,000 units/g. This method is mostly used by small-scale factories and no longer meets domestic food quality and safety standards.
Spray Drying
This method involves removing some impurities through centrifugation before spray drying. The resulting product has relatively high enzyme activity, around 1 million units/g, with fewer impurities and a relatively whiter color. However, during spray drying, the product tends to stick to the walls, leading to significant enzyme activity loss and poorer water solubility and stability.
Membrane Separation Method
This method avoids the drawbacks of the previous two methods, ensuring a hygienic and safe production process with high yields. The resulting enzyme has minimal activity loss, typically reaching 2.8 to 3.5 million units/g, with a maximum of 4 million units/g. The enzyme also exhibits good stability, high purity, bright white color, and low bacterial count, making it suitable for pharmaceutical-grade applications.
The extraction process conditions include ultrasound power of 300W, ultrasound treatment time of 200 seconds, and a pulp concentration of 30%. Ultrasound-enhanced extraction increases enzyme activity by 1.71 times. The enzyme remains relatively stable below 40°C and at a pH of 5.4 to 6.0. EDTA, cysteine, and vitamin C activate the enzyme, while CuSO4 and ZnCl2 inhibit it. KCl, NaCl, CaCl2, and MgSO4 have little effect on enzyme activity.
The process for isolating and purifying papain involves initial collection and treatment, ammonium sulfate fractionation at 20% and 40%, SP-sephadex C50 column chromatography, and hydroxyapatite column chromatography. This method can produce a pure enzyme with a specific activity of 1184 U/mg, a recovery rate of 55.79%, and a purity of 99.31%, resulting in high-purity papain.
Applications of Papain
Papain has a wide range of applications in pharmaceuticals, food, beverages, chemical reagents, feed, textiles, cosmetics, and more, with promising development potential.
Food Industry
In the food industry, papain is used for meat tenderizing, beer clarification, and biscuit softening.
Papain in Beer Clarification
Beer haze is mainly caused by proteins in beer that easily bind with polyphenols to form large molecular complexes. Papain, used in beer clarifiers, has a broad specificity for the haze-forming proteins, breaking them down into smaller molecules, increasing the solubility of protein-polyphenol complexes. Additionally, papain, a biologically active protein, can stabilize these complexes, preventing beer haze during refrigeration.
Meat Tenderizer
Papain breaks down collagen and muscle fibers in meat, loosening its structure. As a cysteine protease, it degrades collagen fibers and connective tissue proteins, converting myosin and collagen into small peptides or even amino acids. This process breaks down muscle fibers and tendons, making the meat tender and easier to digest.
Biscuit Softening Agent
Papain's enzymatic reaction breaks down the proteins in dough into small peptides or amino enzymes, reducing dough's resistance to stretching, making it softer, more pliable, and easier to shape. The dosage varies depending on the biscuit factory's processing methods and the protein content in the dough, with studies suggesting an optimal addition of 6,000 to 10,000 units per kilogram of dough.
Scientific Research Applications
Papain is used in cell culture experiments, specifically in the first step of preparing cell cultures, where it helps separate cells by breaking down the extracellular matrix after treating small tissue blocks with the enzyme for 10 minutes. The reaction is then stopped with a protease inhibitor to prevent further cell breakdown, and the tissue is dispersed into a single-cell suspension using a Pasteur pipette.
In immunology, papain is used to cleave immunoglobulins (antibodies) into Fc (crystallizable) and Fab (antigen-binding) fragments.
Papain Packaging and Storage
Storage Conditions: This product should be sealed, protected from light, and stored in a cool, dry, and well-ventilated area.
Packaging: Bulk 25kg per cardboard drum, samples 1kg per aluminum foil bag, or customized packaging according to customer requirements.
Transportation: Delivered by express or logistics; domestic express delivery within three days, logistics within five days. Prices generally include domestic shipping costs.
Shelf Life: Two years.
Plant Source—Papaya
Papaya (*Pseudocydonia sinensis*), a shrub belonging to the Rosaceae family, has thornless branches with soft hairs when young. Its leaves are elliptical with serrated edges, and the flowers are pale pink with numerous stamens. The fruit is a long elliptical shape, dark yellow, woody, and aromatic, with a short stalk. It flowers in April and fruits from September to October. During the Western Jin Dynasty, Guo Pu annotated the Erya dictionary, explaining that the papaya, resembling a small melon, has a sour taste and a woody texture, thus earning its name.
Papaya is distributed across China's Shandong, Shaanxi, Hubei, Jiangxi, Anhui, Jiangsu, Zhejiang, and Guangdong provinces. It prefers sunny, warm environments with adequate rainfall and semi-dry, semi-wet soil. Papaya can be propagated by seeds or through methods like cutting, dividing, or layering.
Papaya is both medicinal and edible, primarily used for its medicinal properties, such as soothing the liver and stomach, promoting blood circulation, and benefiting the spleen and lungs. It is used to treat conditions like rheumatism, joint pain, limb numbness, vomiting, diarrhea, and abdominal pain. The fruit is astringent and can be eaten after boiling or soaking in sugar syrup. Papaya is also valued for its ornamental qualities, with beautiful, abundant, and colorful flowers, making it a popular choice for ornamental trees, crabapple rootstock, or bonsai cultivation in gardens and parks, contributing to urban greening and landscaping.
