Use of Time-resolved reflectance spectroscopy to distinguish apples with a differing texture

Anna Rizzolo1*, Maristella Vanoli1,2, Fabio Lovati1, Maurizio Grassi1, Marina Buccheri1, Nadja
Sadar3, Alessandro Torricelli4, Angelo Zanella3, Lorenzo Spinelli2
1 Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Unità di ricerca per i processi dell’industria agroalimentare (CREA-IAA), via Venezian 26, Milano
2 Istituto di Fotonica e Nanotecnologie – CNR-IFN, piazza Leonardo da Vinci, 32, Milano
3 Centro di Sperimentazione Agraria e Forestale, Vadena, Laimburg 6, Ora (BZ)
4 Politecnico di Milano, Dipartimento di Fisica, Milano, Piazza Leonardo da Vinci, 32, Milano

Fruits with a differing texture are characterized by different optical properties of the pulp. The coefficients of absorption (μa) and the reduced scattering (μ's), measured in a non destructive way through Time-resolved reflectance spectroscopy (TRS), are linked to the sensory, mechanical and acoustic properties of the fruit pulp. In order to study the possibility to utilize the TRS technique for the selection of ‘Braeburn’ apples with different qualitative and sensory characteristics, 270 fruits harvested at 3 different periods were measured individually using TRS (670-1040nm) after 1, 7 and 14 days of shelf life. From the spectra of absorption and of scattering, the contents of chlorophyll (CHL) and of water (H2O) and the scattering (μ's) were extracted. The same apples were analyzed for their sensory, mechanic and acoustic properties, and for the intercellular spaces (RISV). The sensory attributes (firmness, juiciness, mealiness, crunchiness) underwent the cluster analysis, which led to the distinguishing of 3 sensory profiles (W1, W2, W3). The W1 apples, of mealy texture, had the highest values of μ's and RISV, and the lowest levels of H2O and of the mechanical and acoustic properties. The W3 apples, of crunchy texture, presented the lowest levels of μ's and RISV, and the highest levels of CHL, H2O and the acoustic and mechanic properties. The discriminant analysis based on the optical properties, allowed the correct classification of 73% of the W1 fruits, 85% of the W3 fruits and 49% of the W2 fruits (medium texture). In addition, models of the classification of the intensity (very low, low, medium, high, very high) of the individual sensory attributes were studied. The performance of these models varied from 50% for the crunchiness to 61% for the firmness, even if more than 70% of the apples belonging to the class very or little mealy, and very or little firm were classified correctly.
Activity type
Participation in scientific conference
Activity work package
Fruit quality; improvement of fruit handling/storage
Activity number
Activity contact
Dr. Angelo Zanella
Laimburg Research Centre
Laimburg 6 - Pfatten
I-39040 Post Auer (BZ), Italy
[email protected]
Activity partner
Activity country
Last edit
The EUFRUIT thematic network has received funding from the
European Union's Horizon 2020 research and innovation programme
under grant agreement No 696337.