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New Method for Detecting Rancid Hazelnuts Without Opening Packaging
A team of researchers at the Universitat Rovira i Virgili (URV) has devised an innovative method to detect hazelnuts that have turned rancid due to oxidation. Utilizing infrared light, this technique assesses the chemical makeup of the nuts while they remain within their shells.
This study is published in the journal Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. It presents a significant advancement over conventional methods, enabling the analysis of an entire package of hazelnuts in a single test without necessitating sample destruction or preparation. The researchers advocate that this technology could enhance packaging and distribution strategies, ultimately reducing waste in the nut industry and promoting improved quality standards.
Catalonia, particularly its southern regions, is well-known for its nut production, with the hazelnut ranking second after almonds in annual yield. Over 90 cooperatives in this region generate hazelnuts valued at more than 75 million euros, focusing largely on export markets, especially in the Tarragona area, according to the Catalan Federation of Agricultural Cooperatives.
Effective processing, packaging, and distribution are critical for maintaining hazelnut quality and minimizing loss. The unsaturated fatty acids present in hazelnuts can lead to rancidity when exposed to oxygen and light, which accelerates the oxidation process.
“Improper packaging can significantly increase the rate of oxidation,” notes Jokin Ezenarro, a lead researcher at URV’s Department of Analytical and Organic Chemistry.
Utilizing Hyperspectral Technology
To tackle this issue, the research team has developed a system that allows for real-time monitoring of hazelnut oxidation, enabling producers and traders to assess quality prior to sale. This system employs a hyperspectral camera, which analyzes the oxidation state across the entire package.
“It acts as a spectrophotometer, projecting light at various points to reveal the sample’s composition based on its interactions,” explains Ezenarro.
The technology harnesses infrared radiation, which operates beyond the visible light spectrum. All organic molecules absorb infrared light, though the specific frequencies vary according to their chemical composition.
Unlike traditional spectrometers that analyze isolated points, hyperspectral cameras evaluate the entire surface area, akin to how a conventional camera captures an image through multiple pixels. This capability offers a competitive edge, permitting a comprehensive evaluation of hazelnuts without removing them from their packaging.
The new approach aligns with a growing trend in analytical chemistry that favors non-destructive, eco-friendly techniques. As Ezenarro comments, “These methods eliminate the need for reagents and do not require the apparatus to touch the sample.”
However, the effectiveness of this technique can be influenced by factors such as packaging material and thickness, which affect infrared readings. To calibrate the device, the researchers subjected hazelnuts to various storage conditions over a 78-day period, including vacuum-packed scenarios and exposure to different atmospheres and light conditions. This allowed them to develop a mathematical model correlating analytical data with the nuts’ conservation status.
Findings indicated that environmental factors, particularly the surrounding atmosphere and light exposure, are key contributors to hazelnut oxidation. Prolonged storage emerges as a significant catalyst in the deterioration process.
“Our research confirmed that vacuum packaging proved most effective, while light exposure detrimentally impacted product stability,” Ezenarro states.
The study didn’t stop there; it also sought to assess how oxidation affects consumer perception. By validating their methodology, the researchers aimed to establish if the measurable chemical changes were noticeable to consumers. Sensory tests indicated a clear link between spectroscopic data and sensory characteristics, confirming that exposure to light and atmospheric conditions resulted in noticeably rancid samples.
This push for quality control methods that are non-destructive provides businesses in various fields with a competitive advantage. Particularly in the nut trade, it holds promise for elevating packaging practices, storage solutions, and distribution systems while reducing waste and enhancing quality standards.
Although access to this advanced technology is currently limited due to the high costs of necessary instruments—often exceeding 50,000 euros—similar systems are emerging that can differentiate between sweet and bitter almonds or sort materials in recycling processes.
“The future of hyperspectral imaging in quality assessment is promising,” concludes Ezenarro.
More information: Jokin Ezenarro et al, NIR-HSI for the non-destructive monitoring of in-bag hazelnut oxidation, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2025). DOI: 10.1016/j.saa.2025.125906
This study was conducted at the University of Rovira i Virgili.
Source
phys.org