Wavelength variation of the depth of penetration of Near Infrared radiation in Hass avocado fruit

Abstract

This study reports on the wavelength dependence of near infrared (NIR) radiation penetration depth into 'Hass' avocado fruit for both transmission and reflectance modes in the wavelength range from 12820−4000 cm−1 (780−2500 nm). For transmission mode, depths of penetration less than 3 mm occurred in the 5369 to 7413 cm−1 (1862−1348 nm) range, while the maximum depth of penetration of approximately 12 mm occurred in the region 11293 to 11987 cm−1 (885−834 nm). Two other wavelength regions were identified with significant depth of penetration in transmission mode, one around 9272 cm−1 (1078 nm) and the second at approximately 7899 cm−1 (1265 nm) with approximately 10 mm and 4.5 mm penetration respectively. In reflectance mode, despite the difference in the optical paths sampled, qualitatively similar trends in wavelength dependence of the depth of penetration were observed, with a lower penetration depth of 3.3 mm occurring around 9311 cm−1 (1074 nm) and maximum depth of penetration of approximately 4.8 mm occurring in the 11625 to 11987 cm−1 (860−834 nm) region.