Measuring perceived sweetness by monitoring sorbitol concentration in apples using a non-destructive polarization-based readout

The determination and qualification of sugars in fruits are important for quality control and assurance of horticultural produce. The sugars determine the sweetness levels in fruits. The requirement for a universal technique that is also robust to predict the sweetness of the fruit in a non-destructive fashion is immense. The handheld refractometer, hydrometer, electronic tongues, and high-pressure liquid chromatography (HPLC) in combination with other detectors have long been used to determine the sweetness of horticultural produce. Though these techniques are very accurate and useful, they require extensive sample preparation and are generally time-consuming and expensive. Optical techniques like visible to near-infrared spectroscopy (vis/NIRS) are simple in use and can rapidly predict the sweetness of the fruit in a non-destructive fashion. The instrumentation used in these techniques is simple and cost-effective for routine analysis of the fruits. However, their systems need calibration for each sample, and the measurement variation depends on the type of horticultural produce on which measurements are done. An optical-based technique is proposed that uses reflected phase information of the incident light and correlates the same to the presence of sorbitol concentration in apples. The refractive index of sorbitol varies as the fruit ripens due to its change in concentration, and the reflected phase information accordingly changes. Monitoring the reflected phase information allows a prediction mechanism of the sweetness content in the fruit.