Leeder Consulting specialist laboratory services



food analysis services
>> food analysis services > taint in food ( 1 ) ( 2 ) ( 3 ) ( 4 - case study)
 
Taint Resolution in the Food Industry  
Case Study - The Case of the "Parmesan Cheese" Paper
This case shows how a complex set of events led to the evolution of a highly odorous compound from imported paperboard destined for take-away pizza boxes in Australia.
Taint Resolution in the Food Industry Case Study
A shipment of around 500 tonnes of paperboard was shipped from Finland to Australia via the hold of a cargo ship. An initial inspection revealed no defects so the shipment was accepted. However as the rolls were unwound to convert them into corrugated pizza boxes, the corrugator operator noticed an intense odour reminiscent of parmesan cheese. It was discovered that the odour was indeed emanating from the paperboard.

Laboratory investigations using headspace gas chromatography - mass spectrometry identified the offending compound as butyric acid at levels of around 0.2 mg/kg. Butyric acid has a very intense odour which closely matched the parmesan cheese odour in the paperboard. Butyric acid is not normally detected in the volatile emissions from paperboard.

Literature searching uncovered the Clostridia family of bacteria which are commonly known as "butyric acid bacteria". Clostridia also emit acetic acid in a fixed ratio to butyric acid. Further examination of the analytical data revealed that acetic acid was present in direct proportion the butyric acid, thus providing further evidence for Clostridia being the source of the taint. Clostridia is a spore-forming anaerobic bacteria which germinates under warm anaerobic conditions. It feeds on carbohydrates with the major metabolite products being butyric acid and acetic acid.

It was finally traced to the water system of the paper mill in Finland where a new water treatment plant had been installed. In response to environmental pressure to reduce wastewater emissions, the mill had closed up their water system and installed a new anaerobic water treatment plant. It was in this anaerobic system that the bacteria originally bred through many generations resulting in both free bacteria and spores being present in the mill's process water.

The manufacture of paper is a continuous process involving filtering of a dilute slurry of pulp fibres, followed by pressing and drying. The heat of the driers on a paper machine operate at temperatures in excess of 150OC and are normally extremely good at sterilising the paper. However the microscopic spores of Clostridia are resistant to heat and survived the drying process. The spores by this stage were well interred within the tightly wound rolls of paperboard, but did not germinate to form the free bacteria.