Near infrared spectroscopy can non-destructively assess the effect of canopy position and crop load on peach fruit maturity and quality

Traditional methodology for fruit quality and maturity assessment is destructive and hard to adopt for field measurements. Near infrared (NIR) spectroscopy was used to test whether physicochemical and maturity properties of peach fruit could be determined non-destructively. Multivariate prediction models of ‘Sierra Rich’ peaches using an ‘open type’ hand-held NIR sensor were developed in the spectral ranges of 729-935 nm for dry matter content (DMC) and soluble solids concentration (SSC), of 477-657 nm for fruit firmness (FF) and of 600-750 nm for index of absorbance difference for chlorophyll (I_AD). Regression data of independent validation were tested for linearity (R²) and root mean square error of prediction (RMSEP) to determine accuracy of the models. Regression statistics of the prediction models highlighted that DMC (R²=0.98; RMSEP=0.52%), SSC (R²=0.96; RMSEP=0.60%) and I_AD (R²=0.96; RMSEP=0.11) could be predicted very accurately with a single scan using NIR. Finally, the created models were used to predict the effect of crop load and peach fruit position in the canopy on peach internal quality and maturity using large volumes of fruit samples. Results showed that heavier crop loads reduced DMC, SSC and fruit maturity as measured by (I_AD). On the other hand, fruit canopy position affected fruit internal quality (DMC, SSC) and maturity (I_AD) mainly in the moderate crop loads. Models developed in this study will be used to efficiently and accurately assess the effect of orchard and environmental factors in peach fruit quality.