Nondestructive and Rapid Assessment of Intact Tomato Freshness and Lycopene Content Based on a Miniaturized Raman Spectr
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Nondestructive and Rapid Assessment of Intact Tomato Freshness and Lycopene Content Based on a Miniaturized Raman Spectroscopic System and Colorimetry Xiaping Fu 1
&
Xueming He 1 & Huirong Xu 1 & Yibin Ying 1
Received: 14 October 2015 / Accepted: 11 February 2016 # Springer Science+Business Media New York 2016
Abstract Tomatoes and tomato-related products are associated with many health benefits and disease risk reduction. This work was to explore the use of a miniaturized Raman spectroscopic system for rapid and nondestructive quality assessment of intact tomatoes. Combined with colorimetry and spectrophotometry methods, surface color and lycopene content of intact tomatoes were measured as references. The ratio of two chromaticity indices a*/b* of tomato surface increased when their freshness declined; the correlation coefficient (r) of the second-order polynomial curve-fitting was 0.908. The freshness discriminant model developed on Raman spectra gave a correctness of 85.6 %. The quantitative models performed poorly for predicting lycopene content based on Raman spectra. From the results obtained, it can be concluded that the established miniaturized Raman spectroscopic system was feasible for assessing the freshness of intact tomatoes. However, it is difficult to predict the lycopene content accurately. Keywords Raman spectroscopy . Tomato . Lycopene . Freshness . Colorimetry . Spectrophotometry
Introduction Tomatoes and tomato-related products are associated with many health benefits and disease risk reduction mainly due * Huirong Xu [email protected]
1
College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China
to the high content of lycopene in tomatoes (Bicanic et al. 2010; Pudney et al. 2011; Kocks et al. 2013). Lycopene belongs to the family of carotenoids, which are important components of antioxidant defense against lipid peroxidation in living cells (Agarwal et al. 2005). It has received particular attention as a result of studies indicating that lycopene has highly efficient antioxidant with free radical scavenging capacity, which stands for health benefits. Over 85 % of the dietary lycopene in the North America diet is provided by tomatoes and tomato-related products such as juice, ketchup, paste, sauce, and soup (Rao and Agarwal 2000). Therefore, the quality assessment of tomato samples is of relevant importance, providing very useful information from the nutritional and physiological points of view. Spectrophotometry and high-performance liquid chromatography methods have been extensively applied for analyses of carotenoids (Barba et al. 2006; Ravelo-Pérez et al. 2008; Bunghez et al. 2011; Luterotti et al. 2013); however, these wet chemical methods are very cumbersome, time-consuming, and expensive. In order to get a deeper insight into biological samples, many spectroscopy techniques were developed and used to analyze the light-matter interaction phenomena. Examples are absorption spectroscopy (Schmitt et al. 2014), fluorescence spectr
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