Emerging Technologies for Non- Destructive Quality Evaluation of Fruit

The development of science and technology, and especially of information technology, has made available many non-destructive methods for analysis of materials, which can also be applied to fruits. The fruit industry needs non-destructive techniques for on-line sorting and certifying high quality fruit. Electronic noses, acoustic methods and optical methods like near infrared spectroscopy are mentioned, and their applicability for fruit analysis is discussed. The principles and the application of time-resolved reflectance spectroscopy (TRS) are more deeply described. TRS can measure separately and independently the optical properties (absorption coefficient a and transport scattering coefficient s’) at selected wavelengths in highly diffusive media. Absorption coefficient is related to chemical compounds, like pigments, while scattering coefficient is related to tissue structure and to air and water distribution. TRS has recently gained increasing use in biomedicine for the non-invasive investigation of biological tissues. It has also been used for optical characterization of fruit. TRS measurement is not influenced by color or other surface characteristics, because it probes a volume at a depth of 1-2 cm. Recent experiences of application with fruit are reported. In pears it was possible to detect brown heart (by a at 720 nm) and mechanical injury (bys’ at 720 nm), which were not visible externally. In apples, the scattering coefficient was related to pectin composition and to firmness after storage. In nectarines, by using a at 670 nm, high and low flavour fruit were selected and the softening during shelf life was predicted. The absorption at about 670 nm, near the chlorophyll peak, is also useful to evaluate maturity in apples and pears.