Optimisation Process Parameters and Characterisation of Microwave Dried Beetroot Leather

Tan, Pang Yu (2021) Optimisation Process Parameters and Characterisation of Microwave Dried Beetroot Leather. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Beetroot, a root vegetable that has plentiful of bioactive compounds and phytochemicals, is able to increase its shelf life besides retaining most of its health benefits by processing it into dried-sheet of leather for consumption. A highly efficient microwave drying with optimal drying parameters able to minimise the loss of bioactive compounds. The aim of the study is to investigate the microwave drying characteristics of beetroot leather at various microwave power (80 W, 240 W, 400 W) and sample thickness (3 mm, 5 mm, 7 mm), and determine its optimised drying parameters for desirable quality properties. The effect of sample thickness and microwave power on the quality properties such as moisture content, water activity, pH, colour, texture vitamin C content, betalain content, total phenolic content and antioxidant content of the dried beetroot leather was investigated by means of faced-centred central composite design. The sample with the lowest thickness value at 3 mm and the highest microwave power at 400 W achieved the highest initial drying rate (26.76 % d.b.·min). Microwave power and slice thickness was significantly influenced (p < 0.05) to the texture (hardness) of the leather. The optimal drying parameters were 3 mm of sample thickness and 80 W of microwave power which yielded microwave dried beetroot leather with 17.18% (d.b.) of moisture content, water activity of 0.72, pH 4.38, colour (L* 8.7, a* 14.8 and b* 4.1), texture (167.73 N of hardness and 280.51 J of chewiness), 788.86 mg/ 100 g of vitamin C content, 40.16 mg/ 100 g of betalain content, 392.51 mg GAE/ 100 g of total phenolic content and 222.58 AAE/ 100 g of antioxidant content. In short, this research is able to point out the drying characteristics of beetroot leather and optimises the process parameters for its improvement of quality properties.