Measurement of non‐enzymic browning of dehydrated carrot

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 8-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.

Carotene, ascorbic acid and sugar content of vacuum dehydrated ripe mango powders stored in flexible packaging material

“…Moisture was analysed by vacuum drying method by drying to constant weight (AOAC, 1984) and nonenzymatic browning (NEB) was determined by the method used for carrots by Baloch et al (1973).…”

Kinetics of colour changes in dehydrated carrots

“…Several researchers have studied the effect of drying on carrot quality (Doymaz, 2004;Lin et al, 1998;Mazza, 1983;Park, 1987;Prakash et al, 2004;Schadle, Burns, & Talley, 1983;Sumnu, Turabi, & Ö ztop, 2005). However, the literature contains few references on the retention of b-carotene and colour stability in dehydrated carrots during storage (Baloch et al, 1973;Baloch, 1987;Negi & Roy, 2001). Kinetic parameters including reaction order, rate constant and activation energy are essential to predict the quality of foods.…”

“…Another important chemical change occurred in some dehydrated foods is nonenzymatic browning (Baloch, Buckle, & Edwards, 1973). The formation of dark-coloured pigments in foods during processing and storage is a very common phenomenon.…”

“…Browning can also appear during long storage, and is generally dependent upon product characteristics and storage conditions (Toribio & Lozano, 1984). The most common method for characterizing browning in dehydrated carrot is the measurement of absorbance at 420 nm (Baloch et al, 1973). In addition, tristimulus colourimetry was also used to evaluate colour changes in carrots (Chen, Peng, & Chen, 1995;Inazu & Makino, 1998;Zhao & Chang, 1995).…”

Desulphiting dried apricots by exposure to hot air flow

“…16 Extraction of the water-soluble brown pigment was carried out with 20 g l À1 acetic acid containing 10 g l À1 formaldehyde. Interfering carotenoid pigments were removed by the use of lead acetate and ethanol.…”