Number 17      October 1993

MAFF UK - METHANOL IN ORANGE JUICE

Index to MAFF UK Food Surveillance Information Sheets, 1993

Background

Methanol is formed naturally in orange juice by action of enzymes on the pectin material of cell walls. The enzymes are likely to remain active in unpasteurised orange juice and this may lead to a build up of potentially toxic levels of methanol. Reported literature levels for methanol range from 4 to 420 mg/kg

In 1991, The Working Party on Naturally Occurring Toxicants in Food noted that the recommended shelf life of orange juice had increased from 24-48 hours to up to 10 days and that this might lead to increased levels of methanol in the juice as consumed. A survey was commissioned to determine the concentrations of methanol in orange juice consumed in the UK and to investigate whether the concentrations increased with storage time.

The survey analysed 23 samples of freshly squeezed and nine samples of pasteurised orange juice which were purchased from retail outlets in the Norwich area. The juices were stored as recommended on the label until analysis. Juices from several varieties of newly purchased oranges were also expressed manually to provide a further six samples. These juices were pooled to provide a sample for a trial on the effects of storage on the formation of methanol at 4° and 20°C.

Results

The results of the survey are presented in Table 1 and show methanol levels detected in samples of fresh (including hand squeezed) and pasteurised orange juice. Methanol levels increased in 15 out of 16 samples after storage of five days beyond the 'use by date'. On storage of ten days beyond the 'use by date', methanol concentrations increased slightly in 4 samples and decreased in three samples, but by this stage the juices were unpalatable. No particular trend was observed in the trial on storage at 4° and 20°C.

Interpretation

Levels of methanol in the hand squeezed juices were lower than the commercially pressed juices and this may be due to industrial presses releasing more cell wall enzyme material than hand expressed juices. Pasteurised juices contained lower methanol concentrations than fresh juices and this could indicate that the pasteurisation process reduces enzyme activity.

Dietary surveys have shown that an extreme consumer of orange juice drinks slightly over 2 litres/day. The estimated maximum intake of methanol based on this consumption would be 455 mg for a 60 kg adult which is below the maximum advisory intake of 600 mg per day for a 60 kg adult, recommended by the Department of Health.

Contact Point:

Further information on this project can be obtained from:
Mrs Chelvi Leonard
MAFF, Food Safety and Science Group
Food Contaminants Division
Room 210, Ergon House c/o Nobel House
17 Smith Square
London SW1P 3JR

Tel: +44 (0)171 238 5734
Fax: +44 (0)171 238 6591

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