Non-Destructive, Opto-Electronic Determination of the Freshness and Shrivel of Bell Pepper Fruits.

Abstract

(1) The objective of the present study was to identify suitable parameters to determine the (degree of) freshness of Bell pepper fruit of three colors (yellow, red, and green) over a two-week period including the occurrence of shrivel using non-destructive real-time measurements (2) Materials and methods: Surface glossiness was measured non-destructively with a luster sensor type CZ-H72 (Keyence Co., Osaka, Japan), a colorimeter, a spectrometer and a profilometer type VR-5200 (Keyence) to obtain RGB images. (3) Results: During storage and shelf life, bell pepper fruit of initially 230-245 g lost 2.9-4.8 g FW per day at 17 °C and 55% rh. Shriveling started at 6-8% weight loss after 4-5 days and became more pronounced. Glossiness decreased from 450-500 a.u. with fresh fruit without shrivel, 280-310 a.u. with moderately shriveled fruit to 80-90 a.u. with severely shriveled fruit irrespective of color against a background of <40 a.u. within the same color, e.g., light red and dark red. Non-invasive color measurements showed no decline in Lab values (chlorophyll content), irrespective of fruit color and degree of shrivel. RGB images, converted into false color images, showed a concomitant increase in surface roughness (Sa) from Sa = ca. 2 µm for fresh and glossy, Sa = ca. 7 µm for moderately shriveled to Sa = ca. 24 µm for severely shriveled rough surfaces of stored pepper fruit, equivalent to a 12-fold increase in surface roughness. The light reflectance peak at 630-633 nm was universal, irrespective of fruit color and freshness. Hence, a freshness index based on (a) luster values ≥ 450 a.u., (b) Sa ≤ 2 µm and (c) the difference in relative reflectance in % between 630 nm and 500 nm is suggested. The latter values declined from ca. 40% for fresh red Bell pepper, ca. 32% after 6 days when shriveling had started, to ca. 21% after 12 days, but varied with fruit color. (4) Conclusion: overall, it can be concluded that color measurements were unsuitable to determine the freshness of Bell pepper fruit, whereas profilometer, luster sensor, and light reflectance spectra were suitable candidates as a novel opto-electronic approach for defining and parametrizing fruit freshness.

Plant phenotyping relevance

ピーマン果実の鮮度・萎びという植物器官の状態を、光沢センサー、分光、プロフィロメータ、画像で非破壊的に定量化し、鮮度指標を提案しているため、測定法の開発・応用が中心です。

Code and data availability

The article describes opto-electronic freshness/shrivel measurements on bell pepper fruit but contains no data availability statement, no public dataset or image deposit, and no author code or model release. The only URLs present are the CC BY license notice and a cited 2004 dissertation (prior work, not a paper asset,

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