ASTM E875-20. Evaluation of Fungal Control Agents as Preservatives for Aqueous-Based Products Used in the Paper Industry. 

Test not accredited in our laboratory.

The ASTM E875 standard defines a test procedure used to determine if a fungal control agent prevents deterioration in water-based processed products used in the paper industry (pigment suspensions, dye solutions, pulps, starch solutions, polymers, gluing agents, latex emulsions…etc.). To prevent product spoilage over a desired period of time, the fungal control agent must kill the fungi, prevent their growth, or both, and also prevent fungal spore germination.

To perform the test, the aqueous material to be preserved is inoculated with an appropriate fungal inoculum, depending on the purpose of the test. If evaluating the basic effectiveness, the use of standardized fungal cultures is recommended. The following strains are considered suitable: Aspergillus niger, Penicillium pinophalum, Trichoderma virens, Candida albicans, and Saccharomyces cerevisiae. Conversely, if the control agent needs to be evaluated for a particularly difficult or specific preservation problem, a fungal spoilage product or a fungal strain or combination of strains isolated from the spoilage product may be appropriated. After inoculation of the samples, the test control agent is added at the desired concentrations. Each test must include a minimum of five concentrations of the fungal control agent (including at least one active and one non-active concentration) and two controls, with no control agent added. Subsequently, the samples are incubated at the storage temperature of the product, generally between 25°C and 30°C. The incubation time of the samples should be set according to the storage time of the aqueous material, using the average time during which the product will need protection, generally six weeks. Samples should be analysed weekly, or at another suitable time interval, for visual deterioration, odour, colour and pH changes, and fungal growth by streaking samples on agar plates. After the incubation time, the level of growth is determined using a scale of 0 (no growth) to 4 (strong growth). Samples showing no visible fungal growth should be re-inoculated and incubated for at least one more week. The proper level of fungal control agent is one that prevents product deterioration and reduces and keeps microorganisms to an acceptable level in the aqueous test material, as determined by the client. To judge the degree of preservation obtained, visual deterioration or other signs of degradation such as changes in pH, colour and odour should also be evaluated. For the assay to be valid, deterioration of the control product (without control agent) due to fungal growth must be observed.