146 Papaya
13.5.1 Sun Drying
It gives the lowest quality product as there is considerable loss of enzyme activity
and the papain can easily turn brown. However, in many countries sun drying is still
the most common processing technique for papain. The latex is simply spread on
trays and left in the sun to dry.
13.5.2 Hearth Drying
Papain driers can be of simple construction known as hearth. In Sri Lanka and India,
they are, generally, simple out-door stoves of 1m height, made out of mud or clay
bricks. The latex can also be dried artificially in a home drier in a kind of drying
stove constructed by building a chamber of bricks about a meter high, a meter wide
and 2 m long. The sides and ends are of bricks with an opening at the end to admit
fuel. The top is open. About 30 cm below the top an iron sheet is placed. Upon this
2.5–5 cm of sand is spread to modify and distribute the heat arising from the fire
beneath. The coagulated juice is spread upon brown linen stretched upon the frame
which is made to fit the top of the drier. Smoking spoils the latex. Therefore, coconut
shell or charcoal is recommended as fuel. The fuel is so regulated that drying time,
an approximate 4–5 h is affected slowly with temperature preferably below 40°C.
Drying is complete when the latex becomes crumble and no longer sticky.
13.5.3 Solar Drying
A multi-rack step solar drier for drying papain has been developed with overall
dimensions of 2430 × 1630 × 310 mm 10 trays each of the size of 890 × 460 × 25 mm
and two glass layers each of 3 mm. Trays used in the drier are made of aluminium
and are provided with semicircular grips so that the same trays can be used for latex
collection range of 50–85°C when the ambient temperature is 28–32°C because the
butterfly valves provided in the two rear chimneys control the movement of papain
production by solar drier as compared to the conventional sun drying method.
13.5.4 Spray Drying
Spray-dried papain has a higher enzyme activity (assaying) than other type of papain,
and is totally soluble in water. Extreme care must be taken when handling this form
TABLE 13.1
Operational Conditions of Different Dryers
Number Origin Drier type Temp (°C) Pressure (mbar) Time (h)
1 Latex Oven 40 746.6 8
2 Latex Tray drier 40 746.6 2
3 Latex Vacuum oven 40 137.06 18
4 Latex Lyophilisator − 30 0.1 24