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Papain
Papain is an endolytic plant cysteine protease enzyme which is isolated from papaya
(C. papaya L.) latex. Laticifers of papaya are complex tissue systems of the articu-
late-anatomizing type. These conducts are multi-cellular columns with perforated
transverse lateral walls, protoplast fusion, and intrusion of phloem cells, forming
branched networks (Hagel et al. 2008). Damage to any aerial part of the papaya
plant, where laticifers are widely distributed, elicits latex release, which is very typi-
cal for this species (Azarkan et al. 2003).
The papain present in the latex is an enzyme of industrial use and of high
research interest (Saran and Choudhary 2013). Papain exporting countries are Zaire,
Tanzania, Kenya, Israel, Philippines, Sri Lanka, Cameroun and India and the major
source of spray dried papain is Zaire. Principal importers are the United States,
Japan, the United Kingdom, Belgium and France. Other countries import papain in
small quantities. Papain is in great demand in international market, particularly the
United Kingdom, the United States and Europe (Ram 2005). With the increase in the
cultivation of papaya in various parts of India, it is highly profitable to manufacture
papain where fruit production is in abundance (Ram 2005). In India, papain can be
supplied and sold to Enzo-Chem Laboratory Yeola, Nasik and M/s. Pharmaceutical
and Cosmetic Promotion Council, Mumbai.
Almost all the best quality papain goes to the England and United States for use as
crude papain in the brewing industry for chill-proofing beer. However, the increasing
trend for additive free beers initiated by other European countries is taking effect in
England and so this market for papain is declining. Among the major applications, it
is used in the food industry (Saran and Choudhary 2013), beer clarification, meat ten-
derising, preparation of protein hydro-lysates, etc. The lanced fruits may be allowed
to ripen and can be eaten locally, or they can be employed for making dried papaya
‘leather’ or powdered papaya, or may be utilised as a source of pectin. Because of its
papain content, a piece of green papaya can be rubbed on a portion of tough meat to
tenderise it. Sometimes, a chunk of green papaya is cooked with meat for the same
purpose. One of the best known uses of papain in commercial market is as meat ten-
deriser, especially for home use. A modern development is the injection of papain into
beef cattle half an hour before slaughtering to tenderise the meat than that it would
normally be. However, the papain-treated meat should never be eaten raw but should
be cooked sufficiently to inactivate the enzyme. The tongue, liver and kidneys of
injected animals must be consumed quickly after cooking or utilised immediately in
food or feed products, as they are highly perishable. Papain has many other practical
applications; it is used to clarify beer, also to treat wool and silk before dying, to de-
hair hides before tanning, and it serves as an adjunct in rubber manufacturing (Amri
and Mamboya 2012). It is applied on tuna liver before extraction of the oil which is
thereby made richer in vitamins A and D. It is incorporated into toothpastes, cosmet-
ics, detergents and pharmaceutical preparations to aid digestion.