144 Papaya
easily inhabited by contact with some metals such as iron, copper, zinc, etc., and
works best at particular temperatures. Fresh latex is obtained from 75 to 90 days
old developing green fruits fit for latex extraction. This starts in rainy season and
continues up to March. Cool and wet periods produce more papain. It is obtained by
making incisions on the surface of the green fruits early in the morning.
Maximum latex flow was obtained between 5:00 and 10:00 a.m. The incising
knife is made using a stainless steel razor blade set into a piece of rubber attached
to a long stick used for lancing the fruit. The blade should not extend beyond more
than 2 mm as cuts deeper than 2 mm because juices and starch from the fruit pulp
mix with the latex, which lowers the quality. Four vertical incisions are made in the
fruits with a sharp knife to a depth of 1–2 mm on fruit from stalk end to the fruit
tip (Figure 13.2). The incision should be repeated on 3–4 subsequent occasions at
an interval of 4–5 days. A non-metallic container should be used for collecting the
latex. The greener the fruit, more active is the latex flow. The higher the specific
activity or rate of catalysing per unit weight of enzyme, higher is the value. The
activity of papain can be increased by refinement in processing. The quality and the
grade of papain is determined by colour and enzyme activity (tyrosine unit) which is
classified in three groups, (i) crude papain white brown to brown, (ii) crude papain in
flake or powder referred as semi-refined and (iii) spray dried crude papain of higher
activity in powder form referred to as refined papain. The refined papain having the
activity of 800–1000 units or higher is most preferred in world trade. Extraction of
latex must tap more than 1000 average-size fruits to gain 450 g of papain. Fruits
should be tapped at intervals of about 4–7 days and for the first tapping it is usually
sufficient to make only one cut. On subsequent tapping the two or three cuts are
spaced between earlier ones.
FIGURE 13.2 Papain extraction technique.