Non-invasive Digital Refractometer to Measure Maturation of Climacteric Fruits

Abstract

Sugar content is a superior quality indicator for the post-harvesting and ripening status of climacteric fruits. Total soluble solids (TSS) represented by ∘Brix index is a measure of the sugar content. The conventional way to measure TSS is by invasive (IN) technique using manual or digital refractometers. While non-invasive (NIN) infrared refractometer devices have been developed in recent years for various agricultural and food science applications, its accuracy to measure fruit TSS directly is not straightforward, as the device is only dedicated to uses for a specific fruit. This study aims to investigate the suitability of the use of a non-invasive refractometer to measure TSS directly for some post harvested fruits. For comparison, a conventional invasive digital refractometer was also used. Red apples and green apples were used as a reference, while tests were done on bananas, mangos, red pears, golden pears and sapodillas. Among the fruit samples, red pear is the only fruit whose TSS can be measured using the non-invasive refractometer accurately, whereas the device is not suitable for the other fruits due to the significant percentage error and inapplicable corrective calibration value which may lead to a limited prediction of TSS content values.