3. Results and discussion
3.1. The optimal ratio of lychee to purple sweet potato
Drying curves of paste of different ratio are shown in Fig. 3.
It can be seen that drying rate increased as lychee content
increased at the first drying stage. Drying rate during the
first 4 min was from 0.413 to 0.451 kg/kg min when the lychee
proportion changed from 20% to 50%. There was significant
difference in drying rate between 20% and 50% lychee proportion
paste (p < 0.05). However, there was no significant
difference between 20% and 30% as well as 40% and 50% lychee
paste mixture. It suggests that drying rate of materials can be
significantly changed at the first drying stage when the difference
in sugar content between two pastes is above 4.8%. In
other words, more sugar content can result in more