L-cystine from hydrolysis of poultry feather keratin (3c391) — authorisation renewed until 5 March 2035; ≥ 98.5 %, determination by IEC-VIS/FLD, impurity specification according to the 2019 Ph. Eur. monograph, protection now for the respiratory tract only
Commission Implementing Regulation (EU) 2025/272, published on 13 February 2025, renews the authorisation of L-cystine as a nutritional additive (amino acids) for all animal species and repeals Implementing Regulation (EU) No 1006/2013, which had authorised it for 10 years. It is based on the EFSA opinion of 18 April 2024 (e8800) and an updated report of the reference laboratory on the methods of analysis.
- Specification (annex): L-cystine at least 98.5 %, solid form, produced by hydrolysis of keratin from poultry feathers; CAS 56-89-3, C6H12N2O4S2. Methods: identification according to the Food Chemical Codex L-cystine monograph; determination in the additive — ion-exchange chromatography with post-column derivatisation and optical detection (IEC-VIS/FLD), in premixtures — IEC-VIS according to Regulation (EC) No 152/2009 or IEC-VIS/FLD, in compound feed — IEC-VIS according to 152/2009. The reference laboratory updated its report on the methods “to take into account scientific and technological progress”, and EFSA verified it (FEEDAP Panel meeting of 15–16 October 2024).
- Conditions: on the label — “Supplementation with L-cystine shall depend on the requirements of the target animals for sulphur-containing amino acids and the level of other sulphur-containing amino acids in the ration”; personal protective equipment for the respiratory tract only, where procedures do not eliminate the risks. EFSA quotes that the previous authorisation required breathing protection, safety glasses and gloves; in studies following OECD guidelines 404, 405 and 429 L-cystine was not irritant to skin or eyes and not a skin sensitiser, but exposure by inhalation is likely (dusting potential 133–300 mg/m³).
- Data from the EFSA opinion (e8800): the applicant updated the impurity specification to the 2019 Ph. Eur. monograph — total ninhydrin-positive substances ≤ 0.5 %, each individual ≤ 0.2 %; water ≤ 0.5 %. Five batches: on average 99.3 % cystine (99.1–99.7 %); 668 batches from 2021: on average 100.1 % (98.5–101.0 %). Specific optical rotation from −222.8° to −221.5° against the Ph. Eur. range −224…−218°. Mercury above the LOQ in only one of ten batches (0.007 mg/kg). Particle fraction below 98 μm 0.6–1.8 %, no particles below 50 μm; solubility in water 0.11 g/L; 48 months of storage at 25 °C without losses.
- Transition: the additive and premixtures produced and labelled before 5 September 2025, compound feed and feed materials for food-producing animals before 5 March 2026, and for other animals before 5 March 2027 (under the rules applicable before 5 March 2025) may remain on the market until stocks are exhausted. For feed laboratories: cystine in compound feed is determined by the IEC-VIS method of Regulation (EC) No 152/2009, and in the additive itself by IEC-VIS/FLD.