Abstract
In modern fruit processing technology, non-destructive quality measuring techniques are sought for determining and controlling changes in the optical, structural, and chemical properties of the products. In this context, changes inside the product can be measured during processing. Especially for industrial use, fast, precise, but robust methods are particularly important to obtain high-quality products. In this work, a newly developed multi-spectral imaging system was implemented and adapted for drying processes. Further it was investigated if the system could be used to link changes in the surface spectral reflectance during mango drying with changes in moisture content and contents of chemical components. This was achieved by recovering the spectral reflectance from multi-spectral image data and comparing the spectral changes with changes of the total soluble solids (TSS), pH-value and the relative moisture content xwb of the products. In a first step, the camera was modified to be used in drying, then the changes in the spectra and quality criteria during mango drying were measured. For this, mango slices were dried at air temperatures of 40–80 °C and relative air humidities of 5%–30%. Samples were analyzed and pictures were taken with the multi-spectral imaging system. The quality criteria were then predicted from spectral data. It could be shown that the newly developed multi-spectral imaging system can be used for quality control in fruit drying. There are strong indications as well, that it can be employed for the prediction of chemical quality criteria of mangoes during drying. This way, quality changes can be monitored inline during the process using only one single measuring device.
Highlights
Product quality and efficiency are of great importance in the design of drying processes for exotic fruits or other sensitive biological foodstuffs
A newly developed multi-spectral imaging system was implemented and adapted for drying processes. Further it was investigated if the system could be used to link changes in the surface spectral reflectance during mango drying with changes in moisture content and contents of chemical components
This was achieved by recovering the spectral reflectance from multi-spectral image data and comparing the spectral changes with changes of the total soluble solids (TSS), pH-value and the relative moisture content xwb of the products
Summary
Product quality and efficiency are of great importance in the design of drying processes for exotic fruits or other sensitive biological foodstuffs. This is of great interest, since on the one hand, energy is becoming more and more expensive and the accessibility of energy cannot be guaranteed always and everywhere. Exotic fruit demonstrate great health benefits like vitamins, sugars, or acids, which could be destroyed in poor drying processes. In modern approaches in drying technology, a substitution of these analysis techniques is sought. The use of spectrometers, RGB (Red, Green, Blue) cameras or combinations of both (e.g., hyperspectral imaging) bear chances of being this substitution
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