Identification of biphenyls - Contaminants responsible for off-flavour in soft drinks

Abstract

Off-flavour in soft drinks is one of the main threats to manufacturers, which can result in expensive recalls, and discredit the brand. Off-flavours can occur for a variety of reasons (e.g. chemical contamination of raw material). The presented case study has proved there is a relationship between the identification of biphenyl and its derivatives in the used preservative (benzoate) and off-flavours in the drink. The project consisted of three phases: (1) the assessment of the probable cause of off-flavours based on sensory evaluation and GC-MS-Olfactometry profiling of volatiles; (2) the quantification of biphenyls and the characterisation of their sensory properties; (3) the screening of commercially available benzoates for the presence of biphenyls. Based on the odour threshold obtained by GC-O (0.03 mg/l for 4-methyl-1,1'-biphenyl and 0.02 mg/l for biphenyl in an aqueous solution) and the common benzoate content in soft drinks (0.14 g/l), the 'non-observable sensory' levels of contamination were determined to be maximally 0.143 mg/g of benzoate for biphenyl and 0.214 mg/g of benzoate for 4-methyl-1,1'-biphenyl .