Abstract:
Almost all instrumental non-destructive (ND)
type firmness test methods which involve a
physical contact with the tomato when used for testing, deliver at least a minute damage to the
fruit. The damage induced on a fruit was estimated when a so-called non-destructive firmness
test was performed repeatedly on tomato fruit. The common method of firmness testing uses
Magness-Taylor (MT) type firmness tester and in
this destructive type test method, after having
peeled, the tomato pulp is pierced with a probe. Qualitest (HPE-ll-FFF model) tester and the
Bishop (FT 327 model) tester were used as ND
and MT type firmness testers, respectively.
Tomato variety “Rajitha” grown in Rathkinda area in Matale, during
Maha
season (Sept 2008)
was subjected to this investigation. In a series
of repeated ND type firmness test , a loss of
firmness of 9.5 % was observed between the fi
rst and the second measurement, regardless the
ripeness level of tomato. At lower ripeness leve
ls, tomato exhibited an exponential decay in
percentage loss of firmness when subjected to repeated ND test, while red-ripe tomatoes
demonstrated a slightly deviated behaviour.
A study on the behaviour of MT vs. ND type
firmness suggests a good linear relationship with a non-zero intercept. The relationship
proposes a ND type firmness of 0.405 kg for a
tomato which registers zero MT type firmness.
Hence the contribution of the peel to th
e ND type firmness would be 0.405 kg.
