With the improvement of people’s environmental protection concept, kraft paper packaging has gradually become part of people’s daily life. With its great advantage of environmental protection and safety, it is gradually replacing the plastic packages which used to dominate the food packaging industry.

A variety of kraft paper items are used frequently in Food Trucks, McDonald’s, KFC, Starbucks and other restaurants. However, not all of the kraft paper can be used in food packages. Actually, the selection of kraft paper in the food industry is extremely circumspect.

Plain kraft paper：For instance, Kraft shopping bag of mall, kraft carton from delivery.

Food-grade kraft paper can be divided into two main categories, one can directly contact with food, such as deep-fried wrapping paper. The other can’t directly contact with food, like takeaway bags in McDonald’s.

Under normal conditions, the difference between the two, which cannot be identified by our eyes. Using tools to check if residual fluorescence agent.

Plain craft paper normally has a high-level fluorescence agent. By comparison, Food-grade craft paper which can directly contact food eliminates fluorescence agents. The other type which is not allowed to directly contract with food only contains a trace amount of fluorescent agent.

Introduction for a fluorescent agent.

In most cases, fluorescent agents are some specific dyes, which can also be called fluorescent whitening agents. It is a complex organic compound. Absorbing incident light and producing fluorescence is its feature. With this feature, the dyed substance will have a luminescent effect. Then when we look at the dyed substance, it appears whiter and brighter. Furthermore, fluorescent whitening agents have also been used in the paper industry for more than 60 years.

The function of fluorescent whitening agents

The paper made from chemically free virgin pulp will be yellowish, such as Rice paper for Chinese paintings. In fact, most of the paper on the market is white, due to the color requirement, virgin pulp paper failure to meet demand. Therefore, bleaching is needed in production process. In order to make virgin pulp become whiter, will add blue dye to neutralize the color. However, the paper failure to reach the required white color after bleaching, so fluorescent whitening agents will be added as a facilitator.

Distinguishing food-grade kraft paper and plain kraft paper by fluorescence detection.

Most of the raw materials for kraft paper on the market come from 3 sources. High-content recycled pulp, Low-content recycled pulp and pure virgin pulp.

For detecting fluorescent agents, we need to prepare a fluorescent test lamp. Irradiating the test light to kraft paper surface, if the illuminated area appears faint yellow with on bluish violet spots, basically, we can consider it can be directly contacted with food. If the illuminated area with faint bluish violet, it most probably that direct contact with food is prohibited. However, if the illuminated area has an extensive dark bluish violet spot, this is obviously made from high-content recycled pulp. (Ref. Figure 3)

Significantly, the detection of the fluorescent agents is only a simple method to distinguish food-grade kraft paper and plain kraft paper. Identifying kraft paper should follow with food safety standards, industry food certification.