Spectral shift as advanced index for fruit chlorophyll breakdown

Abstract

The decline of fruit chlorophyll is a valuable indicator of fruit ripeness. Fruit chlorophyll content can be nondestructively estimated by UV/VIS spectroscopy at fixed wavelengths. However, this approach cannot explain the complex changes in chlorophyll catabolism during fruit ripening. We introduce the apparent peak position of the red band chlorophyll absorption as a new qualitative spectral indicator. Climacteric fruit (apple: n =24, mango: n =38, tomato: n =48) were analysed at different ripeness stages. The peak position and corresponding intensity values were determined between 650 and 690 nm of nondestructively measured fruit spectra as well as of corresponding spectra of fruit extracts. In the extracts, individual contents of chlorophyll a, chlorophyll b, pheophytin a and carotenoids were analysed photometrically, using an established iterative multiple linear regression approach. Nondestructively measured peak positions shifted unimodal in all three fruit species with significant shifts between fruit ripeness classes of maximal 2.00±0.27 nm (mean ± standard error) in tomato and 0.57±0.11 nm in apple. Peak positions in extract spectra were related to varying pigment ratios (R max =−0.91), considering individual pigments in the pool. The peak intensities in both spectral readings, nondestructive and fruit extracts, were correlated with absolute chlorophyll contents with R max = −0.84 and R max =1.00, respectively. The introduced spectral marker of the apparent peak position of chlorophyll absorbance bears the potential for an advanced information gain from nondestructive spectra for the determination of fruit ripeness.

Fluorescence indices for monitoring the ripening of tomatoes in pre- and postharvest phases

“…In practice, visual classification is time-consuming and may not always be accurate because the definition of colour is a subjective perception influenced by changing light conditions, particularly under greenhouse and field conditions (Hobson et al, 1983). With in tomatoes (Farneti et al, 2012;Seifert et al, 2014), and chlorophyll content in apples (Zude-Sasse et al, 2002;Kuckenberg, 2008) and bananas (Zude-Sasse, 2003) as well as carotenoid content in carrots (Zude-Sasse et al, 2007). Another method, fluorescence spectroscopy, has been proposed for the analysis of tomato ripening in the laboratory (Lai et al, 2007), whereas a hand-held multiparametric sensor has been used to characterize ripening and quality attributes of apples (Betemps et al, 2012), grapes (Cerovic et al, 2009;Ben Ghozlen et al, 2010;Agati et al, 2013) and oil palm bunches (Hazir et al, 2012a(Hazir et al, , 2012b).…”

Use of time‐resolved spectroscopy as a method to monitor carotenoids present in tomato extract obtained using ultrasound treatment

“…In intact leaves, in this spectral region, changes have been explained by differences in the relative contributions of photosystem II (PSII, emitting toward 670 nm) and photosystem I (PSI) chlorophyll that emits at longer wavelengths (Franck et al ., ; Pedrós et al ., ). In fact, changes in the chlorophyll make up have been proposed as a means to follow fruit ripening, albeit based on absorption spectra (Seifert et al ., ). Whether this applies to our extract is a moot point, but certainly a change in the chlorophyll emission is observed between the samples.…”

Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs

“…Although we do not consider it a bioactive, the fact that chlorophyll is present needs to be kept in mind and knowledge about its fluorescence behaviour understood. In relation to the food industry, the ability of producers to ascertain the health of plants in the “field” is becoming an economic necessity and remote sensing [ 50 , 51 ] has been employed, with an emphasis on monitoring chlorophyll fluorescence to monitor plant health [ 52 , 53 , 54 ]. Monitoring chlorophyll fluorescence has also been used to assess the influence of herbicide [ 55 ] and to this effect time-resolved fluorescence also employed [ 56 ].…”

“…Fruit ripening is also an area where monitoring the change in chlorophyll emission is useful and this has found application with tomatoes [ 57 ] and even post-harvest with olives [ 58 , 59 ]. Use of the chlorophyll absorption spectrum has also been proposed to monitor fruit ripening [ 54 ]. In fact, the whole subject field of photosynthesis and chlorophyll research is an exceedingly large area of investigation spanning from fundamental biology into materials and green energy applications.…”