Start a Papain Making Unit

    
(264) Start a Papain  Making Unit
Papain is a proteolytic enzyme from the cysteine proteinase family. It is manufactured from
the latex of raw papaya fruits as papaya is very rich in papain. A milky fluid known as latex
containing papain oozes out of the green papaya. The greener the fruit, more active is the
papain. papaya is grown in large quantities in the North-East region including Assam.
Papain enzyme results in high value-addition. Hence this product can be manufactured . It is also possible to produce papain enzyme in many other states
Maharashtra, UP, AP and so on. Ideally, some progressive papaya grower should undertake
this venture as a measure of forward integration.
2.0 PRODUCT
2.1 Applications
Dry powder made from the latex of raw papaya is commonly known as crude papain. Dried
papain is stored in powder or flakes form. They are diluted with lactose powder to get BPC
grade papain. There is a market for raw as well as BPC grade papain. This note considers
production of BPC grade papain.
2.2  Availability of know-how and compliances
CFTRI, Mysore, has developed the technical know-how. Compliance with FPO is necessary.
3.0 MARKET POTENTIAL
Papain is used in many industries for variety of reasons. Some of the end-users are
breweries, pharmaceuticals, food, leather, detergents, meat and fish processing etc. Thus, the
end use segments are many. Most of these industries are growing. Good quality papain has
export demand as well. In spite of very good domestic as well as export demand, papain
194manufacturing has not yet picked up in the North-East and hence there are good prospects
for new entrants.
4.0 MANUFACTURING PROCESS
White milky latex of green and fully grown papaya fruits is collected in the early morning by
making deep longitudinal cuts by stainless steel or wooden sharp knives. Latex is collected in
stainless steel trays while latex coagulated in the surface of the fruits is scrapped and
collected in the trays. A fruit is tapped about 6 times in the course of 16 days. This latex is
passed through 50 mesh sieves to remove dirt and then it is mixed with potassium
metabisulphate and spread on trays and dried in a vacuum shield drier at a temperature of
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about 55 C for 4-5 hours. The dried product is packed in air-tight containers and stored in a
cool, dry place. It should be kept in flake form as powdering decreases the stability of the
product during storage. Dried flakes are powdered and diluted with lactose powder to get
BPC grade papain. Plastic containers should be used to pack crude papain flakes or powder
as metal containers would result in loss of enzyme activity. Transportation is also very
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critical as papain has to be kept below 20 C temperature or else its shelf life is reduced.
With proper storage and handling, its shelf life is 5-6 months. Recovery of BPC grade papain
is in the range of 25% to 30%. In other words, 100 kgs. of good quality latex is required to
produce 25-30 kgs. of BPC grade papain. CFTRI, Mysore, has developed the technical knowhow for the product.

Methods of collection and extraction

Papain is obtained by cutting the skin of the unripe - but almost mature - papaya before
collecting and drying the latex which flows from the cuts. The fruit should be tapped some time during the morning (a period of high humidity). The lower the humidity levels, the lower the flow of latex.

Two or three vertical cuts (except the first cut, see below) 1-2mm deep are made,
meeting at the base of the fruit. The incisions are made using a stainless steel razor blade
set into a piece of rubber attached to a long stick. The blade should not protrude more than
about 2mm as cuts deeper than 2mm risk juices and starch from the fruit pulp mixing with
the latex, lowering quality.

Fruits should be tapped at intervals of about 4-7 days. For the first tapping, it is usually
sufficient to make only one cut. On subsequent tappings, the two or three cuts are spaced
between earlier ones (as explained above).

After about 4-6 minutes the flow of latex ceases. A dish is used to collect the liquid; it is then scraped into a polythene-lined box with a close fitting lid. The box should then be stored in the shade. Using a close fitting lid and keeping the box in the shade reduce the reactions which cause loss of enzyme activity.
Foreign matter such as dirt and insects should be kept out of the collected latex. Any secreted latex adhering to the fruit should be carefully scraped off and put into the collecting box. However, dried
latex should not be mixed with fresh latex, as this lowers the quality.

When handling fresh latex, care should be taken to ensure that it does not come into contact
with skin: it will cause burning. Neither should the latex come into contact with heavy metals such
as iron, copper or brass, as it causes discolouration and loss of activity. Pots, knives and
spoons should only be used if made from plastic or stainless steel. Fresh latex does not keep well and should therefore be dried to below 5% moisture as soon as possible. This gives it a dry and crumbly texture.

After two or three months the fruits are ripe and should be removed from the tree. The ripe
fruits are edible but have little sale value due to their scarred appearance. However, ripe green papaya skin does contain about 10% pectin (dry weight): the fruits could be processed to extract this.

Drying papaya latex

The method of drying is the main factor that determines the final quality of papain. Various grades have been used since the enzyme has become an international commodity. Up until the mid-1950s, Sri Lankan papain dominated the market, three grades were known:
1 - fine white powder;
2 - white oven-dried crumb, and
3 - dark sun-dried crumb.
Until the 1970s there were two grades:
1 - first or high grade oven-dried papain in powder or crumb form (usually creamy white in colour);
2 - second or low grade sun dried brown papain in crumb form.
As a result of new processing techniques, papain has been reclassified into three groups since 1970:
1 - crude papain - ranging from first grade white down to second-grade brown.
2 - crude papain in flake or powder form - sometimes referred to as semi refined.
3 – spray-dried crude papain - in powder form, referred to as refined papain.

Sun-drying

Sun-drying gives the lowest quality of product, as there is considerable loss of enzyme activity
and the papain can easily turn brown. In many countries, however, sun-drying is still the
most common processing technique. The latex is simply spread on trays and left in the sun to dry.

Oven-drying

Papain driers can be of simple construction. In Sri Lanka they are generally simple outdoor
Stoves. They are typically about one metre high and made of mud or clay bricks. Drying times vary, but an approximate guide is 4-5 hours at a temperature of 35-40°C. Drying is complete when
the latex is crumbly and no longer sticky. A better quality product is obtained if the latex is sieved
before drying. The dried product should be kept in air-tight, light-proof containers (eg. sealed clay pots or metal cans) and stored in a cool place. Metal containers should be lined with polythene.

Spray-drying

Not possible at small-scale because considerable investment in equipment is required. However, it is feasible to buy spray-dried papain for the small-scale processing of foods.
Spray-dried papain has a higher level of enzyme activity than other types of papain and is totally soluble in water. Extreme care must be taken when handling this form of papain: it can cause allergies and emphysema if inhaled. For this reason, spray-dried papain is often encapsulated in a gelatine coat.

Enzyme activity

Whether papain is to be exploited commercially for an export market or for local food industry use, it is important to be able to determine the level of enzyme activity, a process known as assaying.
This can be carried out by, say, the National Standards office.  Papain is used to hydrolyse (or break down) proteins. Therefore, assays to measure papain activity are based on measuring a product of the hydrolysis. There are two main methods of carrying out assays :

Method 1

This method relies on the ability of papain to clot milk. It is a low-cost method but is time consuming. Furthermore, the absence of a standardised method of finding the clotting point, combined with variations in the milk powder used, can introduce errors.
A papain sample is prepared by dissolving a known weight of papain in a known volume of acetic acid solution. This is then added to a fixed amount of milk, which is prepared by dissolving a known weight of milk powder in a known volume of water, warmed to 30°C in a water bath.  The contents are thoroughly mixed and then observed until the first signs of clotting – the formation of lumps - are detected. The length of time from when the papain was added to the milk until clotting begins is recorded.
The experiment is repeated using different known amounts of papain solutions. The varying amounts of papain sample used should give a range of clotting times, between 60 and 300 seconds for optimum results. The activity of the papain samples is then calculated by plotting a graph, finding the time taken to clot milk at an infinite concentration of papain and then using that value in a formula to calculate the activity.  In order to introduce a measure of standardisation, the amount of milk can be fixed at a known concentration. This is done by reacting a known concentration of high-grade papain with the milk. The concentration of milk powder solution can then be adjusted in order to obtain the desired clotting time under fixed reaction conditions. The 'activity of pure papain' at this known amount of milk can then be calculated. Testing the sample papain under the same reaction conditions and same (known) amount of milk will then give an activity which is relative to the pure papain.

Method 2

The second method is based on the science of light absorption, or absorptiometry. This technique measures the amount of radiation (or 'colour' of light) absorbed by a chemical solution.  It is known, for example, that a yellow-coloured solution absorbs blue light. (Blue is the complementary colour to yellow). The greater the concentration of yellow in the solution, the more blue light is absorbed. This is a useful technique because the resulting products of some chemical reactions are coloured. The more intense the colour, the more concentrated the resulting product. Therefore, by shining the relevant complementary colour through the sample liquid, the amount of light absorbed can be related to the concentration of product.  Not all 'colours' (or radiations of light) are visible to the human eye. The technique used when the 'colours' extend beyond the visible spectrum is known as spectrophotometry, and the instrument used is called a spectrophotometer.

In this second method of determining the amount of activity of papain, a known amount of the enzyme is mixed with a fixed amount of casein (the protein found in milk). The
reaction is allowed to proceed for 60 minutes at 40°C. After this time the reaction is stopped by adding a strong acid.  The resulting product of the reaction is tyrosine, which is known to absorb ultra-violet light (invisible to the human eye). The solutions containing the tyrosine are prepared for analysis using the spectrophotometer. The amount of ultra-violet light absorbed by the solution can then be compared to the number of tyrosine units produced by the papain sample. Hence, the greater this number, the greater the activity of the papain sample.

World trade in papain

The principal producers of crude papain are Democratic Republic of Congo (formerly Zaire), Tanzania, Uganda and Sri Lanka. Most spray-dried papain comes from DRC.

Main importers are USA, Japan, United Kingdom, Belgium and France. Almost all the best quality papain goes to the United States.  Crude papain is used in Britain in the brewing industry for chill-proofing beer and lager. However, an increasing trend in additive-free beers - initiated by other European countries - is taking effect in Britain, whose market for papain is therefore declining. Papain is, however, used in the tenderising of meat and in production of meat tenderising powders.

Source of Technology
Technology for papain production could be obtained from CFTRI, Mysore.
The plant should be set up near the field but water and electricity should be available. In
addition, farmer can sell the ripe fruit in the market. It is a highly profitable venture. Another has
been instruments is transfer of this technology to few entrepreneurs.