Multi-sensor approach to improve optical monitoring of papaya shrinkage during drying

This study aimed to assess the feasibility of a multi-sensor approach for predicting shrinkage of papaya during drying using computer vision methods in combination with optical scattering analysis of light at 650 nm. The top-side area and total surface area derived from computer vision were analyzed, while the illuminated area and light intensity from optical scattering images were used to interpret photon migration in the fruit tissue. The relationship between moisture content and shrinkage in terms of volume and area reduction during drying was satisfactorily explained by a linear model. The results demonstrated that the prediction of papaya shrinkage during drying from top and total surface areas of the sample was possible, but can potentially be improved. Multivariate correlations of computer vision parameters and optical scattering properties showed the enhanced performance for shrinkage prediction. This multi-sensor approach could possibly be applied as a fast, accurate and non-invasive technique for in-line quality control to monitor shrinkage in the production of dried fruits

Changes in microstructure and functional properties of papaya as affected by osmotic pre-treatment combined with freeze-drying

Published online: 20 Jan 2017Freeze-drying represents a very effective method to significantly prevent loss of nutrients, especially heat-sensitive compounds. Moreover, osmotic dehydration is frequently applied prior to drying in order to facilitate moisture removal and improve quality. In the present study, the effect of osmotic pre-treatment combined with freeze-drying at different working pressures on microstructure, colour, and functional properties such as carotenoid contents, total phenolic contents (TP) and antioxidant activity in papayas was investigated. Osmotic pretreatment prior to freeze-drying resulted in increased yellowness, apparent density, and solid density, while carotenoids, TP, and antioxidant activity were lower compared to untreated samples. SEM images clearly showed that the effect of working pressure on the characteristic of dried papaya structure. Samples dried at working pressure of 9 and 77 kPa showed higher deformation with large cavities and dense dry layer when compared with those at 28 kPa. In addition, samples were significantly higher in lightness, redness, colour difference, and porosity when the working pressure was applied at 9 kPa. A reduction of working pressure had a negative effect on the retention of carotenoids, TP, and antioxidant activity in freeze-dried samples. It can be concluded that 28 kPa of pressure better conserved bioactive compounds and minimised structural deformation

Computer vision coupled with laser backscattering for nondestructive colour evaluation of papaya during drying

Published online: 19 July 2017Colour change is a common physical phenomenon observed during drying, which need to be controlled since it directly affects consumer acceptance of dried products. This study aimed to investigate the feasibility of using computer vision, combined with laser light backscattering analysis at 650 nm in order to predict colour changes of papaya during drying. The results revealed that each image-processing factor obtained can potentially be used to describe every colour attribute change, except for chroma value. The multivariate correlations of measured backscattering parameters as well as the digital image properties were found to yield the best fitting for colour validations. Interestingly, the use of computer vision technique coupled with laser backscattering methods provides a reliable tool for quality control based on a rapid, consistent, and nonintrusive method for in-line quality measurement in established fruit drying processes

Compositional and functional dynamics of dried papaya as affected by storage time and packaging material

Available online 8 October 2015Papaya has been identified as a valuable source of nutrients and antioxidants, which are beneficial for human health. To preserve the nutritional properties after drying, appropriate storage specifications should be considered. This study aimed to investigate the quality and stability of air-dried papaya in terms of quality dynamics and behavior of bio-active compounds during storage for up to 9 months in two packaging materials: aluminum laminated polyethylene and polyamide/polyethylene. Samples with moisture content (MC) of 0.1328 g g−1 and water activity (aw) of 0.5 were stored at 30 °C and relative humidity (RH) of 40–50%. The MC, aw, degree of browning (DB) and 5-hydroxymethylfurfural (HMF) content were found to notably increase as storage progressed. On the contrary, there was a significant decrease in antioxidant capacity (DPPH, FRAP and ABTS), total phenolic (TP) and ascorbic acid (AA) contents. Packaging in aluminum laminated polyethylene under ambient conditions was found to better preserve bio-active compounds and retard increases in MC, aw and DB, when compared to polyamide/polyethylene