Study On The Formation Of Benzoic Acid During Fermentation In Yoghurt And Investigation Of Benzoic Acid In Fermented Dairys

The formation of benzoic acid during fermentation in Yoghurt is studied; A method of reversed-phase high performance liquid chromatography to determine content of hippuric acid in dairy products is established, and the levels of benzoic acid in Yoghurts and cheeses are analyzed.Hippuric acid can well be separated by RP-HPLC on ODS (Octadecyl silane) column and with methanol-water-acetic acid as mobile phase and UV detector at 254 run . The sample would be determined after being deposited with zinc acetate and potassium ferrocyanide, and with chloroform :phenol (V/V,1: 1), to remove the protein and fat so that it can shorten the pretreatment, decrease the interference and improve the sensitivity. The recovery is 96.2% ~ 104.4%. The minimum detectable value is 0.09mg/kg, and the variation coefficient is 1.60%.This essay also studies the mechanism formation of benzoic acid during fermentation in Yoghurt. During the course of fermentation , benzoic acid is produced from hippuric acid by lactic acid bacteria used as starters, according to a stoichiometric reaction (1:1). Hippuric acid disappears after 3 hours of fermentation, probably having been converted to benzoic acid, mainly because of the lactobacilli. Lactic acid bacteria is the more effective factor rather than acidity.The hippuric acid and benzoic acid levels of yoghurts and cheeses in Nanjing marketplace are investigated. 91.3% of benzoic acid can be found. Benzoic acid has been detected in all of the cheese samples. A second metabolic pathway has been proposed: One...