Safety evaluation of curdlan as a food additive

The EFSA Panel on Food Additives and Flavourings (FAF) provides a scientific opinion on the safety of curdlan as a new food additive used as firming and gelling agent, stabiliser, thickener. Curdlan is a high molecular weight polysaccharide consisting of β-1,3-linked glucose units, produced by fermentation from Rhizobium radiobacter biovar 1 strain NTK-u. The toxicological dataset consisted of sub-chronic, chronic and carcinogenicity, reproductive and developmental toxicity studies as well as genotoxicity. In vivo data showed that curdlan is not absorbed as such but is extensively metabolised by the gut microbiota into CO₂ and other innocuous compounds. Curdlan was not genotoxic and was well-tolerated with no overt organ-specific toxicity. Effects observed at very high doses of curdlan, such as decreased growth and increased cecum weight, are common for indigestible bulking compounds and therefore considered physiological responses. In a combined three-generation reproductive and developmental toxicity study, decreased pup weight was observed during lactation at 7500 mg curdlan/kg body weight (bw) per day, the highest dose tested. The Panel considered the observed effects as treatment-related and adverse, although likely secondary to nutritional imbalance and identified a conservative no observed adverse effect level (NOAEL) of 2500 mg/kg bw per day. Despite the limitations noted in the dataset, the Panel was able to conclude applying the margin of exposure (MOE) approach. Given that curdlan and its break-down products are not absorbed and that the identified adverse effect is neither systemic nor local, no adjustment factor was deemed necessary. Thus, an MOE of at least 1 was considered sufficient. The highest exposure estimate was 1441 mg/kg bw per day in toddlers at the 95th percentile of the proposed maximum use level exposure assessment scenario. The Panel concluded that there is no safety concern for the use of curdlan as a food additive at the proposed uses and use levels.