Nuclear techniques applied in agro-food quality and safety control in China

Nuclear techniques applied in agro-food quality and safety control in China

Carlos Carbone

This article will present some of the latest trends studied by Chinese researchers for food traceability using nuclear techniques.

Stable isotope analysis for agro-food provenance verification and authenticity discrimination

This technique focuses on the use of isotopic fingerprinting techniques for food traceability. It’s becoming a reliable tool for this, due to the independent property built upon the natural isotopic signals that cannot be altered by man [1]. This type of technology has been implemented in specialized equipment by companies like ThermoFisher, an American company which has branches in China [2, p. 4]. Also, laboratories offer their service of direct analysis in platforms like science exchange [3].

In order to distinguish a product’s origin, it is necessary to have a sample reference which relates the levels of isotopes to geographical locations. According to the type of product this is rather a complex task; studies show efforts to determine the best combination of element analysis to efficiently obtain the origin location of the most popular products handled in food safety in China [1]:

• Beef: Traceability systems for beef rely on ear tags and paper records which can easily be mislabeled; therefore, variations in carbon and nitrogen stable isotope ratios are researched to provide a way to find the geographical origin of the product. Results of 85% correctly classified are obtained with a combined analysis of d¹³C and d¹⁵N stable isotopes.
• Wheat: Due to the physical nature of wheat, the traditional analytical method is usually used to verify the quality of the product, distinguishing high quality from low quality. To ensure traceability precision, the method of element analyzer-stable isotope ratio mass spectrometry is used to measure d¹³C and d¹⁵
• Lamb: For this type of meat an approach of stable hydrogen isotope analysis is used. This is due to the value of the lamb meat being highly correlated with the levels of δ²H in their drinking water. The discrimination is enhanced when it’s combined with analysis of δ¹³H and δ¹⁵
• Tea: Often, due to visual similarities, teas are mislabeled in China and sold at high prices using the name of a higher quality tea; for example, Longjing. Levels of several isotopes must be measured for teas, and pattern recognition techniques with principal component analysis and linear discriminant analysis have been used to determine geographical origins.
• Organic food: In China, as in many parts of the world, organic food has higher prices than conventional food. It’s very easy to counterfeit products under this market scheme by labeling regular products as organic. As one of the main differences between the two, fertilizer of synthetic nitrogen is prohibited in organic agriculture, and the use of nitrogen isotopes techniques to identify organic food is highly encouraged.
• Camellia oil: This oil is highly recommended by health departments as it has many bioactive components. As with other products, camellia oil is constantly adulterated with cheaper oils. For this, analysis of δ¹³C has proven to be an efficient authentication method.

Knowing which elements provide the best classification criteria is key. With this, a reference chart such as Fig. 1 could be used to determine the origin of a product using spectrometry equipment. Fig. 1 is the result of a study which shows levels of carbon and nitrogen isotopes in wheat, when it is grown in Australia, USA, Canada, and two provinces of China [4].

Mass spectrometers are the lab detection workhorses and they are chosen accordingly for the stable isotope analysis of the chosen element within the type of sample, liquid or solid.  Studies show that manufacturers will continue to improve their equipment, so it fits the needs presented by the scientific community as they find more applications and discoveries for this type of technology. Companies like ThermoFisher have developed the Delta V™ Isotope Ratio Mass Spectrometer, used to obtain isotopic mapping for such crops as wheat (see below, Fig.1). (Spectrometer manufacturer list:  http://www.sisweb.com/index/referenc/ms-comp.htm#Mass)

Fig. 1: Distribution of C and N isotopic composition of wheat [4].

Obtaining these charts is quite a challenge and is key to greatly enhancing food safety traceability. To remedy this in China, CTI (which is the parent company of REACH24H) is collaborating with the UK-based isotope lab Food Forensics to create a database by collecting worldwide samples [5].

Other techniques for food safety include nuclear technique application in analytical method development.

The incremental pollution of China is a threat factor that needs close attention by handlers; these contaminants can be measured with high sensitivity and specificity. Techniques applied for this issue include [1]:

• Radio-immunoassay for contaminant analysis: Used for the detection of drugs in feed by detecting the tetracycline antibiotic residues in feed. It can also detect many other substances by methods that have been developed in the last decade.
• Stable isotopes dilution for veterinary drug residue analysis: This method provided a way to identify and quantify multi-component vet drugs in various feeds.
• Determination of microbial toxins: Used for the detection of microbial toxins which contaminate foods during growth, storage and manufacture of raw material. The method provides the determination of the mycotoxin ochratoxin A.

Non-Nuclear Rapid Testing Systems:

• Rapid food testing technology (e.g., pesticide residue testing, water quality testing, waste oil testing, mycotoxins testing, microbial detection, and food safety detectors) has been sanctioned by China’s recently amended food safety law and also included in its “Thirteen Five” national science and technology innovation plan. “Consumers are paying more and more attention to family food safety issues and the rapid testing service provided to families has become a new trend,” said Lichuan Sang, the general manager of Zhiyunda, one of China’s leading rapid food testing technology companies.

[1]          T. Chen, G. Chen, S. Yang, Y. Zhao, Y. Ha, and Z. Ye, “Recent developments in the application of nuclear technology in agro-food quality and safety control in China,” Food Control, vol. 72, pp. 306–312, Feb. 2017.

[2]          “Stable Isotope Analysis.” [Online]. Available: https://www.thermofisher.com/us/en/home/industrial/spectroscopy-elemental-isotope-analysis/isotope-analysis/stable-isotope-analysis.html. [Accessed: 20-Nov-2017].

[3]          “Stable Isotope Analysis – Science Exchange.” [Online]. Available: https://www.scienceexchange.com/marketplace/stable-isotope-analysis?page=1. [Accessed: 20-Nov-2017].

[4]          D. Luo et al., “The application of stable isotope ratio analysis to determine the geographical origin of wheat,” Food Chem., vol. 174, pp. 197–201, May 2015.

[5]          “China Food Safety: Stable Isotopes Analysis to Be Launched for Food Authenticity,” food, 15-Aug-2014. [Online]. Available: https://food.chemlinked.com/news/food-news/china-food-safety-stable-isotopes-analysis-be-launched-food-authenticity. [Accessed: 20-Nov-2017].