Evaluating ripeness in post-harvest stored kiwifruit using VIS-NIR hyperspectral imaging

Authors: LEE, JEONG-EUN - Kangwon National University; KIM, MIIN-JEE - National Institute Of Agricultural Sciences (RDA); LEE, BO-YEONG - Kangwon National University; LEE, JONG - Kangwon National University; YANG, EUN-HA - Kangwon National University; Kim, Moon; HWANG, IN-GEE - Kangwon National University; JEONG, CHEON - Kangwon National University; MO, CHANGYEUN - Kangwon National University

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2025
Publication Date: 3/17/2025
Citation: Lee, J., Kim, M., Lee, B., Lee, J., Yang, E., Kim, M.S., Hwang, I., Jeong, C., Mo, C. 2025. Evaluating ripeness in post-harvest stored kiwifruit using VIS-NIR hyperspectral imaging. Postharvest Biology and Technology. 225: 113496. https://doi.org/10.1016/j.postharvbio.2025.113496.
DOI: https://doi.org/10.1016/j.postharvbio.2025.113496

Interpretive Summary: Consumer demand for safe, high quality fruit has continued to grow. Post-harvest shipping and storage processes can result in changes to the physical and chemical qualities of fruits and thereby affect final consumption quality attributes such as soluble solids content (sweetness) and firmness or texture. Because sweetness and firmness are important internal qualities for kiwifruit, this study used advanced imaging technology that captures light beyond what the human eye can see to evaluate these qualities for kiwifruits stored for 0 to 120 days. By analyzing the images, mathematical models were developed and found capable of accurately classifying the sweetness and firmness of the fruits with over 91% accuracy. This study demonstrated an effective technique for nondestructively and rapidly identifying the stages of kiwi internal quality and post-storage ripeness that can be used by the fruit processing industry to determine optimal shipping and storage times.

Technical Abstract: Kiwifruit (Actinidia deliciosa) stored long-term at low temperatures after harvest can exhibit varying internal quality upon shipment due to the influence of harvest conditions. Flesh firmness (FF) and soluble solids content (SSC) are attributes of eating quality and ripeness, which change during storage. To ensure the timely shipment of kiwifruit with uniform quality, the development of non-destructive measurement techniques for FF, SSC, and ripeness is necessary. In this study, models to predict the FF, SSC, and ripeness stages of kiwifruits were developed using visible-near-infrared (Vis-NIR) hyperspectral imaging. The FF and SSC of kiwifruit were investigated according to the storage period, and five ripeness stages were defined based on these characteristics. Vis-NIR hyperspectral images of kiwifruit stored for 0-120 d were measured to extract hyperspectral spectra. Partial least squares regression and support vector machine regression (SVMR) prediction models were developed to predict the FF and SSC of kiwifruit, and partial least square-discriminant analysis (PLS-DA) and support vector machine classification (SVMC) models were developed to classify ripeness stages. The SVMR model with second-order derivative preprocessing exhibited the best performance in FF prediction, with R2p and root mean square of prediction (RMSEP) values of 0.878 and 3.008 N, respectively. For SSC prediction, the SVMR model with multiplicative scatter correction preprocessing exhibited the best performance, with R2p and RMSEP values of 0.94 and 0.898 Brix, respectively. Ripeness determination achieved the highest accuracy of 91.463% for the PLS-DA model with maximum normalization preprocessing and 91.548% for the SVMC model with range normalization preprocessing. The results of this study demonstrate that Vis-NIR hyperspectral imaging is useful for rapidly identifying the internal quality and post-storage ripeness stages of kiwifruit stored at low (0') temperatures. Furthermore, the developed technology is expected to contribute to determining the optimal shipping time for kiwifruit during storage.