At the recent Security Document Summit in Beijing, Henan Province Wellking Technologies, a member of the International Optical Technologies Association (IOTA), shared a case study about protecting China’s edible salt supply chain. This example highlights how the success of the updated national salt authentication program relies not just on technology but also on implementation and industry standards.
China’s edible salt industry shows this well. Edible salt is one of the most widely used staples in the country, with c. 79 million tonnes consumed in 2024. In such a large market, making sure products are genuine and the supply chain is secure is crucial.
China has used anticounterfeiting labels on salt for many years. But before 2021, manufacturers used different label designs and security features. Wellking says this caused three main problems: inconsistent security standards, widespread counterfeiting, and limited regulatory oversight. Consumers also found it difficult to distinguish genuine products from fake ones.
Addressing these issues, the China Salt Association and regulators launched a new set of standard security labels. There are four types of salt anti-counterfeiting labels: the iodised salt small mark, the combined iodised salt mark and code, the non-iodised salt small mark, and the combined non-iodised salt mark and code.
Fig 1: Examples of new security labels.
The labels are inspired by traditional postage stamps. They mix clear visual designs with advanced micro- and nano-optical technology, making them easy to recognise but difficult to counterfeit.
Fig 2: Level 1 and 2 security features in the new label (forensic features undisclosed).
One distinctive feature is optical levitation encryption, which encodes text and graphics into phase-type micro-lens structures, creating invisible encrypted patterns. When illuminated by a coherent, monochromatic light source, the image reappears with a floating, three-dimensional effect. The apparent depth is controlled by the optical design.
Another feature is dynamic scaling. Special grating structures produce images that change in size or appearance when you change the angle or lighting. This adds a visual check that is hard to copy with regular printing.
On the label, the character ‘盐’ uses high-frequency diffraction gratings with about 2,500 lines per millimetre. These tiny optical structures create strong colour separation, high diffraction efficiency, and colour-shifting effects across many viewing angles, while also reducing stray light.
An additional security layer uses laser reconstruction based on Fourier optics. Hidden micro-grating structures reconstruct the original image only when illuminated with a coherent laser source and remain invisible under normal lighting conditions.
In addition to these optical features, the labels use microtext, micro-encryption, special textures, and precise alignment. These add more layers of protection against counterfeiting.
Beyond the security labels, the initiative established a framework for industry-wide standardisation through two dedicated standards: QB/T 2827-2023 – Technical Conditions of Edible Salt Code Label and QB/T 2828-2023 – Management Specification for Production Enterprises of Edible Salt Code Label.
These standards set rules for security technology, materials, quality control, inspections, traceability, confidentiality, production management, and manufacturer qualifications. They also include specific requirements for the environment, staff, equipment, and materials.
The programme demonstrates that effective authentication relies not only on advanced optical technologies but also on common standards, consistent use, and full supply chain traceability. Together, these steps are building strong protection for China’s salt industry and offer a good example for other large consumer markets.
