Tomato sample firmness was measured by a penetration test
using a texture analyzer (TA-XT Plus; Stable Micro Systems, Surrey,
UK). This test was carried out using a cylindrical stainless steel
module of Ø 4 mm with a test speed of 1.5 mm/s and a distance
of 15 mm. Two maximum forces were registered in this test, corresponding to the maximum force required to penetrate the pulp and
the skin respectively. The texture test was performed four times in
fresh and dried tomato halves. Then the ratio (r) of the maximum
penetration force of dried tomatoes (FmaxDT) and the fresh tomatoes
(FmaxFT) was evaluated (Heredia et al., 2007):
r¼
FmaxDT
FmaxFT
ð3Þ
Theoretically, a values of 1 forrmean no mechanical change
compared to fresh samples (good structure); values ofr< 1 describe a softening of the sample (less good structure) and values
ofr> 1 indicate hardening (less good structure) (Heredia et al.,
2007). However, it is better to have a ratio close to unity indicating
that the tomato after treatment is less firm, easy to rehydrate and
more appreciated by consumers.