Editorial Feature

Citrus Fruit Freshness Assessed Using Portable Raman Instruments

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Many reasons  highlight the importance of citrus fruit consumption for human health. It is well established that they are a rich source of vitamins, minerals and dietary fiber (non-starch polysaccharides) that are essential for normal growth and development, and overall nutritional well-being.

Portable Raman instruments are increasingly used for analysis  and component identification in many fields of study. A search on the Web of Science platform found 177 scientific articles with the words “portable” and “Raman” in the title, published from the year 1992 onwards and concentrated in the past several years. The portable Raman systems versatility in reaching real-world samples prevailed over the difficulty to fit large samples on the lab-based Raman system stage. Data acquisition and processing were achieved with the BWSpec software.

The research features in a paper published in Food Chemistry.

Fran Nekvapil et al., 2018 have aimed to study the relationship, if any, between the freshness of citrus fruit species available on the common markets and their Raman spectroscopy output. More specifically, the freshness hypothesis should be related to the fruit’s aspect and color, and consequently, to the net carotenoids content of the outer peel. Furthermore, such prospect with portable instruments would allow the prompt, in situ, non-destructive and fast evaluation of the quality and freshness of the fruit  objectively and sensitively.

Specimens of mandarin oranges were  obtained as stocks of 0.5 kg from a freshly supplied local market. Three different varieties commonly known as clementines, tangerines and mandarins, were  selected. From the market point of view, the fruits were “the freshest”. Market entering date was used as a starting date (Day 1). Three replicates of each stock on each analysis session was used.

The clementine specimens were divided into two groups. One was kept for 20 days, exposed to daily light at room temperature. The second group was preserved in dark conditions and was analyzed in the fresh state (Day 1), one week later (Day 7), and further, depending on the degradation of the individuals. Fruits were individually wrapped in aluminum foil to prevent contamination and dehydration at room temperature.

Image credit: Louise Crouch/Shutterstock

Randomly selected tangerines and mandarins were additionally considered during the study, under preservation in dark conditions at room temperature. The variability of the individual fruits’ stock concerning their provenance, transport and deposit conditions up to the market supply was not taken into consideration.

Freshness was found to correlate strongly with l the Raman signal collected from the same area of the intact fruits, in a time course of a maximum of 20 days. The intensity of the carotenoid Raman signal is a good indicator of fruit freshness and induced a Raman coefficient of freshness (Cfresh), whose time course is linearly decreasing, with a different slope for different citrus groups. Additionally, they determined that freshness assessments could be completed using a portable Raman instrument. These results could have a influential impact on consumer satisfaction and the food industry.

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  1. Kumar Deepam Kumar Deepam India says:

    Very impressive

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoOptics.com.

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