Development of techniques for measuring banana fruit maturity levels

Maturity of Homthong banana harvested at different stages has significant effects on the fruit final quality and storage period. Banana harvested too early will have less sweetness upon ripening, while banana harvested too late may have short storage life which is particularly important in the export of banana which may take from 2-4 weeks for land and ship transport between different countries. Maturity level suitable for export occurred when the banana was still green, where the peel color, the total soluble solids (TSS), pH, or firmness have not changed much from the early maturity stage, and thus could not be used as an indicator for a suitable harvesting time. In this work, maturity level of banana harvested at different weeks were assessed through electrical measurements together with other physico-chemical properties of banana. It was found that banana harvested at different weeks display quite a marked difference electrical resistance and tend to be well separated for bananas harvested in early weeks, while bananas harvested in later weeks tend to have similar terminal resistance, or not changed as much as those in early weeks. The electrical resistivity of banana increased as the banana became more mature. The increase in electrical resistivity is probably due to an increase in starch accumulation and a decrease in conductive ionic species as banana became more mature. Electrical resistivity measurement could therefore be used as maturity index to aid fruit growers a suitable harvest time.