Measurement of non‐enzymic browning of dehydrated carrot

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Abstract
Non‐enzymic browning of sulphited dehydrated carrot is measured by extracting brown materials with 2% acetic acid containing 1% formaldehyde, followed by precipitation of interfering pigments absorbing at 420 nm with 10% lead acetate and ethyl alcohol. The presence of sulphur dioxide is shown to reduce the absorption at 420 nm of a glucose—glycine browning solution and an extract of dehydrated carrot, the effect depending on time of incubation and exposure to light. The use of formaldehyde in the extraction solvent overcomes the effect of sulphur dioxide at concentrations up to 19 200 parts/million. The presence of carotenoids is shown to increase the absorption of browning extracts at 420 nm leading to high results. The interference from pigment materials is overcome by precipitation with lead acetate and ethyl alcohol. The use of both formaldehyde and lead acetate has no additional effect on browning determinations.Comparative tests of the proposed lead‐alcohol precipitation method with an alcohol precipitation method, using both a glucose‐glycine browning mixture and an extract of dehydrated carrot, shows only the lead‐alcohol precipitation method to overcome errors due to carotenoid pigments either originally present in the extract or added as β‐carotene, while the additional use of formaldehyde during extraction is necessary to overcome errors due to sulphur dioxide.Browning of dehydrated sulphited carrot stored for up to 20 days at 50 °C decreased with time of storage when measured by the alcohol precipitation method and in dehydrated non‐sulphited carrot, browning showed only a slight increase with storage time. When measured by the lead‐alcohol precipitation method, browning showed only a slight increase in stored dehydrated sulphited carrot, but a marked increase in stored dehydrated non‐sulphited carrot, in agreement with visual observations.