The effects of water activity, salt, sodium metabisulphite and Embanox-6 on the stability of carotenoids in dehydrated carrots has been investigated. Carotenoid pigments have been found to be most stable at 0.43 a,. Incorporation of salt, sodium metabisulphite and Embanox-6 significantly reduced the rate of carotenoid destruction and non-enzymic browning in dehydrated carrots.

Freezing before conventional hot-air drying considerably improved the stability of carotenoids and lipids in dehydrated carrots. Freezing, however, did not influence the peroxidase activity, glycine, alanine, glutamic acid, aspartic acid, arginine and serine exhibited pro-oxidant effect while threonine and valine did not have a significant effect on @-carotene stability. Histidine, leucine, isoleucine, tryptophan, ascorbic acid and quercetin exhibited antioxidant effect on p-carotene degradation.

Effect of water activity (a,) and storage temperature on the degradation of carotenoids in relation to keeping quality of freeze dried papaya is reported. Carotenoids were found to be most stable at 0.33 a,, and both below and above this level their rate of destruction was higher. Above 0.40 a, browning limited the storage life. Freeze dried papaya has maximum stability between 0.22-0.33 a,.

The effects of water activity, antioxidants and fatty acid methyl esters on the stability of p-carotene in isolated model systems has been investigated. The rate of p-carotene degradation decreases with the increase in water activity. Both BHA and PG stabilized p-carotene at all water activity levels. Methyl stearate and oleate enhanced the stability of p-carotene. Methyl linoleate stabilized p-carotene during initial stages of slow oxidation after which it exhibited a strong prooxidant effect.