Chewing over the problem of gum antioxidant analysis

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  • Published: May 1, 2017
  • Author: Ryan De Vooght-Johnson
  • Channels: Gas Chromatography
thumbnail image: Chewing over the problem of gum antioxidant analysis

Assays of antioxidants in foods remain a challenge

Butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) are widely used as antioxidants in a variety of foods. Although they are generally considered to be of low toxicity, there has been some concern about possible endocrine disruption effects. The legal EU limits on these compounds depend on the foodstuff, but are roughly 100 mg/kg of foodstuff for BHT and 200 mg/kg for BHA. However, the EU limit for each of the two compounds in chewing gum is 400 mg/kg.

It is important to be able to accurately measure the amount of the oxidants in food samples. Spectrophotometric methods, HPLC and GC have all been used. GC should be a rapid technique in principle, but existing methods tend to involve lengthy work-up procedures, or are only suitable for drinks or cosmetics, rather than solid foods. The Milan researchers examined the analysis of BHT and BHA in chewing gum samples by GC-MS using headspace analysis, developing a method that should be applicable to many other foodstuffs.

BHT and BHA in chewing gum analysed by GC-MS

Six different types of chewing gum were purchased and then chewed by volunteers, giving samples for times of 0, 5 and 15 minutes. The dried samples were then extracted by methylene chloride under sonication, undissolved solids being removed by centrifugation. Deuterated BHT or BHA were added as internal standards, depending on which antioxidant was present in the particular brand of gum. The solvent was evaporated, then replaced by water containing 6.7% v/v acetone. The mixture was heated at 60 °C in the headspace, and the volatile BHT and BHA were absorbed onto a solid-phase microextraction (SPME) fibre.

GC-MS was carried out using an Agilent 5975 instrument fitted with a Varian CP7415 column. A 150 to 250 °C gradient was run at 15 °C/min, followed by six minutes at 250 °C. Clear peaks were seen for the antioxidant compounds, with specific masses being noted for both the two compounds and their deuterated analogues. The method gave good linearity and sensitivity. The LODs for the gum samples, which ranged from 1.4 to 2.8 g sample weight, were given as 9 pg for BHT and 130 pg for BHA.

All the gums examined contained either BHT or BHA, but never both together. They all had antioxidant levels below the required limits, giving the equivalent of 170–185 mg/kg BHT and 86–157 mg/kg BHA. It was found that chewing gave a lower gum weight, but no significant difference was found between 5 and 15 minutes. Not surprisingly, no significant differences were found between male and female ‘chewers’.

The BHA levels were lowered by 4 to 28% by chewing, while those of BHT remained roughly constant. The results suggest that there are unlikely to be any health issues with antioxidants in chewing gum, particularly in the case of BHT. Even for BHA, the amount absorbed by an 18 kg child, calculated to be 1.2–3.5 μg/kg body weight, would be well below the European acceptable daily intake (ADI) of 1 mg/kg body weight per day.

Headspace analysis and GC-MS a promising combination for antioxidant determination

The combination of headspace analysis and GC-MS allowed for fast and accurate determination of antioxidant levels. The advantage of using headspace analysis is that extraction is avoided, so the GC instrument is not clogged up by non-volatiles, such as gum materials. The authors note that the method could be automated for large-scale monitoring of samples. It could also doubtless be applied to the analysis of antioxidants in other foodstuffs.

Related Links

Rapid Communications in Mass Spectroscopy, 2017, Early View Paper. Davoli et al. A simple headspace GC/MS method for the quantitative determination of the release of the antioxidants butylated hydroxyanisole and butylated hydroxytoluene from chewing gum.

Wikipedia, Butylated hydroxyanisole

Wikipedia, Butylated hydroxytoluene

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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