The representativeness of the berry samples is the second major concern.Techniques based on intrinsic fruit fluorescence (autofluorescence) have been successfully applied to grapes [15�C19] and apples [20,21]. Fluorescence indices, based on the comparison of chlorophyll fluorescence excited at two wavelengths, were shown to reflect not only the content of epidermal phenolics in leaves [22,23], but also olive [24] and grape berry [16] skin anthocyanin content. The method is often called the chlorophyll fluorescence screening method (cf. [16]) to distinguish it from the use of variable chlorophyll fluorescence linked to photosynthesis in leaves but also used on fruits [25,26].

Because of the use of a logarithm according to the Beer-Lambert law, the method is also called logFER (for logarithm of the fluorescence excitation ratio) [27,28].

Although the method provides satisfactory results, the different fluorescence-based indices for anthocyanins assessment have to be compared because they are based either on signal ratios [16,29] or on transformed single signals [18,19] that each have different advantages and drawbacks. In our previous works, we used a prototype version of a portable optical sensor with a different optical head geometry [18,19] than the one used in the present study. An industrial version is now commercially available under the same name Multiplex? that includes both options of using the chlorophyll fluorescence screening method and the fluorescence emission ratios.

There is thus a need to test its potential and limits for assessing grape phenolic maturity.

The objectives AV-951 of this work were to validate the use of Multiplex? indices based on the chlorophyll fluorescence screening method by: (1) calibrating the sensor��s different indices for the estimation of grape anthocyanin content, (2) producing a model to separate the decrease of green berries number from anthocyanin accumulation during maturation Dacomitinib and (3) proposing and testing a protocol for the implementation of the sensor to Champagne conditions and grape varieties.2.?Experimental Section2.1.

The Multiplex SensorMultiplex? (FORCE-A, Orsay, France, patent pending) is a hand-held, multi-parametric fluorescence sensor based on light-emitting-diode (LED) excitation and filtered-photodiode detection that is designed to work in the field under daylight on leaves, fruits and vegetables (Figure 1).Figure 1.The Multiplex? sensor. (a) Front view of the optical head with LED sources (6 UV & 3 RGB) and three detectors in the middle (YF, FRF, RF) identical for Multiplex? 2 and 3. (b) Top view of the Multiplex? 2 sensor showing …A block diagram of Multiplex? functions is shown in Figure 2.