The appearance of a food product can influence purchasing decisions, but a brighter color or longer shelf life does not always indicate better quality.
Recent media reports from Qingyuan, Guangdong Province, China, described bamboo shoots that were allegedly treated with burning sulfur to create a whiter appearance and extend storage time. One tested sample was reported to contain 4,860 mg/kg of residual sulfur dioxide. Local authorities reportedly intervened, sealed the related materials and products, and began tracing their distribution. Although this was a regional incident, it raises an important question for food businesses worldwide: how can manufacturers verify that processing aids and food additives are being used legally and within acceptable limits?
Sulfites Are Not Automatically a Food Safety Violation
Sulfur dioxide and sulfites can perform legitimate technological functions in certain foods. They may be used to maintain color, extend shelf life, inhibit microbial growth or support particular processing steps. Health Canada, for example, recognizes several sulfiting agents as regulated food additives used for preservation, color protection and bleaching applications.
However, permitted applications, maximum residue levels and labeling requirements depend on the food category and destination market. In the United States, the FDA removed the generally recognized as safe status of sulfiting agents when used on fruits and vegetables intended to be sold or served raw to consumers.
For international suppliers, this means that compliance cannot be judged by one universal limit. Companies must match the product, processing method and analytical result with the regulations of the target market.
Why Visual Inspection Is Not Enough
Sulfur treatment can significantly change the appearance of plant-based foods. A naturally yellow or brown product may become unusually white and uniform after treatment. Nevertheless, visual inspection alone cannot determine whether sulfites were used, whether the application was permitted or whether the residue level complies with regulations.
Certificates of analysis and supplier declarations remain important, but they should be supported by risk-based verification. Higher-risk materials may include dried vegetables, mushrooms, fruit products, starches, spices and other ingredients in which color preservation or extended storage creates a strong economic incentive for excessive additive use.
Combining Rapid Screening with Laboratory Confirmation
An effective sulfite-control program can begin at raw-material reception.
Rapid screening solutions allow quality-control teams to check more incoming lots before materials enter production. Suspicious, positive or borderline samples can then be isolated for further investigation. This approach helps companies avoid mixing a questionable ingredient into a much larger production batch.
Rapid methods should form part of a tiered testing strategy rather than replace laboratory analysis. When results approach an internal action limit, companies should repeat sampling and use an appropriate validated or reference method for confirmation. The final decision should consider the food matrix, applicable regulation, sampling plan and measurement uncertainty.
Testing records should also be linked to the supplier, origin, batch number and delivery date. Over time, the results can reveal recurring problems and support more precise supplier qualification and sampling frequency.
Supporting Practical Food Additive Monitoring
Beijing Kwinbon Technology Co., Ltd. develops food safety testing solutions for food additives, contaminants and adulteration risks. Its broader portfolio includes more than 100 ELISA products and over 200 rapid test strips for targets such as antibiotics, mycotoxins, pesticides, food additives and food adulteration.
For food businesses, the lesson from the bamboo shoot case is not that all sulfite use is unacceptable. The real risk comes from unauthorized, undeclared or excessive use without effective verification.
By combining supplier assessment, incoming-material screening, laboratory confirmation and traceable test records, food companies can protect consumers, reduce compliance risks and ensure that attractive appearance never replaces reliable safety evidence.
Post time: Sep-20-2026