Attachment 
1 
 Designation of L-methionine as a feed additive 
 
The Ministry of Agriculture, Forestry and Fisheries (MAFF) will designate L-methionine as a feed 
additive allowed to manufacture and sales and establish its standards and specifications in the 
ministerial ordinance. Outline of standards and specifications is as follows. 
 
L-methionine 
 
Compositional specifications in general 
 The content of L-methionine in feed must be 0.1 to 0.5%. 
 
Specifications for method of manufacture in general 
L-methionine of the following specification is allowed to be used as feed additives for all animals. 
 
Specifications for feed additives 
A. Raw material for manufacturing  
(a) Compositional standards 
Content: When this product is determined following a 4-hour drying at 105 °C, it contains 
more than 98.5 % of L-methionine (C5H11NO2S) 
Physical and chemical properties: 
i. This product is white to pale-yellow crystals or crystalline powder. 
ii. This product is lightly soluble in water and hardly soluble in ethanol or ether. 
iii. This product is soluble in dilute hydrochloric acid or 1 mol/L sodium hydroxide test 
solution. 
iv. The pH of a solution of this product in water (1→100) is 5.2 to 6.1 
Confirmation test: 
i. 25 mg (24.5~25.4 mg) of this product is added with 1 mL of sulfuric acid saturated with 
anhydrous copper sulfate. The resulting solution is yellow.  
ii. 5 mg (4.5~5.4 mg) of this product is dissolved with 5 mL of water, added with 2 mL of 1 
mol/L sodium hydroxide test solution, shaken up well, added with 0.3 mL of sodium 
nitroprusside test solution, shaken up well again, allowed to stand at 35~40 °C for 10 
minutes, cooled with ice for 2 minutes, added with 2 mL of dilute hydrochloric acid and 
shaken up. The resulting solution is red. 
Purity test: 
i. Specific rotation: This product is dried at 105 °C for 4 hours, approximately 1 g of it is 
weighed to the digits of 0.01 g, and the value is recorded. It is dissolved with 6 mol/L 
hydrochloric acid test solution to make 50 mL and the solution is filtered as needed. The 
optical rotation of the solution; [α] D25 shall be +21.1 to + 25.1 °. 2 
 ii. Clarity and color of solution: 0.5 g (0.45~0.54 g) of this product is dissolved with 20 mL 
of water. The resulting solution shall be colorless and almost clear. 
iii. Chloride: When chloride is tested using a sample solution prepared with 0.09 g 
(0.085~0.094 g) of this product by the chloride test method and a control solution 
prepared with 0.5 mL of 0.01 mol/L hydrochloric acid, the turbidity of the sample 
solution shall not be higher than that of the control solution (0.20 % or less). 
iv. Sulfate: When sulfate is tested using a sample solution prepared with 0.08 g 
(0.075~0.084 g) of this product by the sulfate test method and a control solution prepared 
with 0.5 mL of 0.005 mol/L sulfuric acid, the turbidity of the sample solution shall not be 
higher than that of the control solution (0.30 % or less). 
v. Lead: 0.5 g (0.45~0.54 g) of this product is weighed. When lead is tested using this 
sample by the lead test method (Method No. 1 of atomic absorption spectrophotometry 
test method), the concentration of the solution shall be less than 20 µg/g. 
vi. Arsenic: 1.0 g (0.95~1.04 g) of this product is placed in a 100 mL decomposition flask, 
and is added with 5 mL of nitric acid and 2 mL of sulfuric acid. A small funnel is placed 
on the mouth of the flask and the solution is carefully heated until white smoke emerges. 
It is allowed to cool, added with 2 mL each of nitric acid twice, heated, added with 2 mL 
each of hydrogen peroxide solution several times, and heated until the solution reaches 
colorless to slightly yellow. It is allowed to cool, added with 2 mL of saturated 
ammonium oxalate and again heated until white smoke emerges. It is allowed to cool and 
added with water to make 5 mL. This is used as a sample solution. When arsenic is tested 
by the method using device A, the color of the absorbing solution shall not be darker than 
the standard color (2 µg/g or less). 
Loss on drying: Less than 0.5 % (1 g, 105 °C, 4 hours) 
Ignition residue: Less than 0.5 % (1 g) 
Assay: This product is dried at 105 °C for 4 hours, approximately 0.3 g of it is weighed to the 
digits of 0.001 g, and the value is recorded. It is placed in a stoppered flask, added with 100 
mL of water, 5 g (4.5~5.4 g) of dibasic potassium phosphate, 2 g (1.5~2.4 g) of potassium 
dihydrogenphosphate and 2 g (1.5~2.4 g) of potassium iodide, and shaken up to dissolve. It 
is added with 50 mL of 0.05 mol/L iodine solution using a volumetric pipetted, tightly 
stoppered, shaken up well, and allowed to stand for 30 minutes, and an excess amount of 
iodide is titrated with 0.1 mol/L sodium thiosulfate solution (indicator: 1 mL of starch test 
solution). A blank test is performed in the same manner. 
0.05 mol/L iodine solution 1 mL = 7.461 mg C5H11NO2S 
(b) Standard of storage method 
It shall be stored in a capped container. 
B. Preparation 
(a) Compositional standards 3 
 The compositional standards of the raw material for manufacturing of L-methionine are 
applied mutatis mutandis. 
(b) Standard of storage method 
The standard of storage method of the raw material for manufacturing of L-
methionine is applied mutatis mutandis.