Destructive and optical non-destructive grape ripening assessment: Agronomic comparison and cost-benefit analysis

Reliability and economic assessment of the Multiplex® optical sensor employed for non-destructive grape parameters estimates was evaluated in 2017 against a wet chemistry approach in mature vineyards including five cultivars (two whites, two red and one pink colored) assuring a broad range of variation in both technological and phenolic maturity parameters. Among the five Multiplex (Mx) indices evaluated (SFR_R, FLAV, FLAV-UV, ANTH_RG and FERARI) in all cultivars with the exception of Barbera SFR_R showed a significant and linear correlation with total soluble solids (TSS) for TSS ≥ 10 °Brix. Conversely, no significant correlation was found between FLAV and total flavonols concentration, whereas a significant linear correlation was found in Barbera (R2 = 0.66) and Ervi (R2 = 0.63) when the FLAV index was replaced with the FLAV_UV index. Within each cultivar, both ANTH_RG and FERARI showed close correlations with total anthocyanins concentration determined by wet chemistry although under different model shapes. Expressing berry color accumulation on a per skin mass basis rather than for whole berry mass basis, allowed for better separation of behavior of single cultivars and improved accuracy of model fitting for the combination of Barbera and ANTH_RG. A strict linear correlation was always found, within each index, for Mx readings taken on the two opposite sides of the same cluster, implying no significant within-cluster differences in sugar, color and flavonol concentrations. Economic assessment of Mx by means of the Net Present Value (NPV) approach showed that Mx is economically viable for a two hectare vineyard cultivating three red grape varieties (90 samples per year) if its lifetime is at least 7 years. Conversely, if only two red varieties are grown Mx should be used at least 11 years to make it economic suitable. Bigger properties growing a higher number of red varieties are the more interested in Mx as the expected NPV assumes positive values with a Mx usage of minimum 3 years.2017年，针对覆盖工艺成熟度与酚类成熟度参数广泛变异范围的成熟葡萄园（共包含5个葡萄品种：2个白葡萄品种、2个红葡萄品种及1个粉葡萄品种），以湿化学法（wet chemistry approach）作为对照，对用于无损估算葡萄生理参数的Multiplex®光学传感器（Multiplex® optical sensor）的可靠性与经济性进行了评估。本次评估共涉及5种Multiplex（Mx）指标，分别为SFR_R、FLAV、FLAV-UV、ANTH_RG及FERARI。在所有供试品种中，除Barbera外，当总可溶性固形物（total soluble solids, TSS）≥10°白利糖度（°Brix）时，SFR_R均与TSS呈现显著线性相关。与之相反，FLAV指标与总黄酮醇浓度未呈现显著相关性；但当将FLAV指标替换为FLAV_UV指标后，Barbera（决定系数R²=0.66）与Ervi（决定系数R²=0.63）的FLAV_UV指标均与总黄酮醇浓度呈现显著线性相关。在各供试品种内部，ANTH_RG与FERARI指标均与湿化学法测得的总花青素浓度呈现较强相关性，不过二者对应的模型拟合形式有所不同。以果皮质量为基准而非整果质量来表征葡萄色泽积累量，可更好地区分各品种的检测表现，并提升Barbera与ANTH_RG组合模型的拟合精度。针对同一果串两侧获取的Mx读数，各指标均始终呈现严格的线性相关，这表明果串内部的糖分、色泽与黄酮醇浓度不存在显著差异。采用净现值（Net Present Value, NPV）法对Mx进行经济性评估的结果显示：若种植3个红葡萄品种（年采样90份）的2公顷葡萄园使用Mx设备，当其使用寿命至少为7年时，该设备具备经济可行性。反之，若仅种植2个红葡萄品种，则Mx设备的使用寿命至少需达到11年方可满足经济适用性要求。种植更多红葡萄品种的大型种植园对Mx设备的接受度更高，因为当Mx设备的使用年限至少为3年时，其预期净现值即可为正值。