Fig. 5 also shows the distribution of changes in SFR. SFR uniformly and linearly increases in the days after pollination. SFR increases from 58.6 N to 222.3 N for the first stage, continues to increase to 381.8 N at the end of the second stage, and reaches 443.2 N at the final stage of over-maturity. This distribution agrees with that found by Jarimopas and Kusol (2007). The slope of the SFR–t curve reduces sequentially when maturity progresses from immaturity to over-maturity. This appears to be because young coconut produces a shield which protects the endosperm and embryo. As a coconut tree is tall, the fruit is subjected to heavy drops and adverse environmental conditions before germinating. Therefore, the fruit shell acquires strength through accumulation of internal components during the maturing process.
Fig. 6 shows that HSL quickly drops from 34.2 N mm−1 to 26.3 N mm−1 during the first stage, decreases slowly and linearly to 23.8 N mm−1 at the end of the second stage, and then decreases faster to 19.6 N mm−1 at the end of the third stage. Husk firmness is an alternative description of husk strength when change of force and deformation are considered together. Husk firmness shows a reduction in strength of the husk with maturity, which is similar to the trend seen for HFR. Husk was deformed and exhibited less firmness when it was pressed (Jarimopas and Ruttanadat, 2007). While HFR requires less measurement and calculation, the HSL is favoured as a non-destructive technique.