Summary - folates

EN 15652:2009 Foodstuffs - Determination of niacin by HPLC:

Scope

This European Standard specifies a microbiological method for the determination of the total folate content of foodstuffs by turbidimetric detection of the growth of the microorganism Lactobacillus casei, subsp. rhamnosus (ATCC 7469).

The method allows for the determination of folates in foodstuffs, including naturally occurring folates and added folic acid (pteroylglutamin acid).

Principle

Samples suspended in phosphate buffer are heated to enable extraction of folates. Protease and α-amylase treatment may be used to further digest the food matrix. Naturally occurring folylpolyglutamates are hydrolysed with γ-glutamyl hydrolase (EC 3.4.19.9) to folylmono- or folyldi-glutamates.

Extracted folates are diluted with basal medium containing all required growth nutrients except folate. The growth response of Lactobacillus casei, subsp. rhamnosus (ATCC 7469) to extracted folates is followed turbidimetrically and is compared to the growth response to calibrant solutions with known concentration.

The method allows for the optional use of a semi-automated liquid-handling system and of a microplate or test tubes for incubation of the microorganism.

Precision data

Matrix parameter	CRM 121 Wholemeal flour	CRM 421 Milk powder	CRM 485 Mixed vegetables	CRM 487 Pig liver
Repeatability RSDr	9,2 %	6,7 %	4,9 %	14,8 %
Reproducibility RSDR	22,3 %	16,9 %	13,8 %	17,0 %