Retention of vitamin B-12 during manufacture of six fermented dairy products using a validated radio protein-binding assay

The aim of this work was to study vitamin B-12 retention during manufacture of six fermented dairy products. Careful validation of a commercial radio protein-binding kit showed this assay to be suitable after optimisation of sample pre-treatment and control of the kit for possible matrix effects. In fermented milks, vitamin B-12 concentrations decreased by 40-60%, compared with the starting milk, during storage of the final product at 4degreesC for 14 days, most likely attributed to consumption by starter cultures. In cottage cheese, hard cheeses and blue cheese, 18-56% of the vitamin B-12 originally present in the milk was retained. Removal of the whey fraction was the dominant factor reducing vitamin B-12 retention in cheeses, while the fermentation by starter cultures hardly affected vitamin B-12 concentrations. (C) 2003 Elsevier Science Ltd. All rights reserved.