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Non-covalent interaction of alcohol dehydrogenase with polysaccharides was studied using three neutral and three anionic polysaccharides. The process of interaction of alcohol dehydrogenase with gum Arabic was optimized with respect to the ratio of enzyme to gum Arabic, pH, and molarity of buffer. Alcohol dehydrogenase-gum Arabic complex formed under optimized conditions showed 93 % retention of original activity with enhanced thermal and pH stability. Lower inactivation rate constant of alcohol dehydrogenase-gum Arabic complex within the temperature range of 45 to 60 °C implied its better stability. Half-life of alcohol dehydrogenase-gum Arabic complex was higher than that of free alcohol dehydrogenase. A slight increment was observed in kinetic constants ( K and V) of gum Arabic-complexed alcohol dehydrogenase which may be due to interference by gum Arabic for the binding of substrate to the enzyme. Helix to turn conversion was observed in complexed alcohol dehydrogenase as compared to free alcohol dehydrogenase which may be responsible for observed stability enhancement. [ABSTRACT FROM AUTHOR]

This work reports on the stability of red beetroot colour used as pre-extrusion colouring of extrudates. Initially, process parameters such as feed moisture content, screw speed and die temperature were optimised using red beetroot colour for pre-extrusion colouring. The colour was monitored in terms of L* and a* values, and also as the percent retention. The optimised conditions that gave maximum retention of colour were a moisture content of 16%, temperature of 160 °C and screw speed of 170 rpm. The effect of citric acid and sodium bicarbonate on colour stability of extrudates during processing, and that of light and packaging materials (polyethylene and metallised polyethylene) during storage at ambient conditions were also evaluated. Addition of 1% citric acid reduced the colour requirement by 37.5%. Metallised polyethylene showed better retention of colour as evident from the time required for 50% loss of colour. The study highlights on the use of red beetroot colour for safe and attractive red-coloured extrudates, and could create a commercial impact. [ABSTRACT FROM AUTHOR]