Water spectral pattern as a marker for studying apple sensory texture

Aquaphotomics is a scientific discipline which investigates the water-light interactions in biological systems by using NIR spectroscopy and multivariate analysis to relate water absorption patterns to bio-functionalities. This work aimed at evaluating the feasibility of Aquaphotomics to study apple fruit sensory texture. ‘Braeburn’, ‘Gala’ and ‘Kanzi®’ apples were analyzed by a MicroNIR spectrometer and for mechanical, structural and texture sensory characteristics. Cluster analysis on sensory texture attributes showed four different profiles for each cultivar having different water spectral patterns (WASP). On average, the WASP of mealy apples showed the highest absorbance values at 1364, 1372 and 1382 nm and the lowest in the 1438-1492 nm range suggesting a preponderance of water structures with weak-hydrogen bonds; the opposite was found in crispy and juicy apples indicating the presence of more organized water structures with medium-strong hydrogen bonds. This WASP difference could be due to a different softening rate: apples clustered as firm/crispy/juicy had the highest firmness and the lowest intercellular spaces, while mealy apples had low firmness and high intercellular spaces indicating a more advanced softening. The chemical changes due to the pectin hydrolyzation could affect the water structures. The Aquaphotomics approach could be a useful tool for studying the sensory texture of fruits as water structures actually change in apples with different textural characteristics whatever the cultivars.