Abstract:

The physical properties and nutritional contents of jujube powder prepared by explosion puffing drying, vacuum
drying, hot air drying and vacuum freeze drying were measured and analyzed to explore the effects of drying methods on
quality characteristics of jujube powder. The results showed that the color of jujube powder prepared by vacuum drying and
vacuum freeze drying were much better; jujube powder prepared by vacuum freeze drying was less soluble than that obtained
from the other methods; no significant difference was found in hygroscopicity; jujube powder prepared by explosion puffing
drying and hot air drying had better rehydration, while jujube powder prepared by vacuum freeze drying had the smallest
particle size and bulk density. The nutritional contents of all four kinds of jujube powder were decreased compared with
fresh winter jujube, but reducing sugar and total sugar content of jujube powder prepared by explosion puffing drying and
vacuum freeze drying were higher; jujube powder prepared by vacuum drying had the highest level of total acid content;
vitamin C and flavonoid contents of jujube powder prepared by vacuum drying and vacuum freeze drying were higher;
Cyclic adenosine monophosphate contents in jujube powder prepared by vacuum freeze drying and explosion puffing drying
were higher than in that obtained from the other two methods. Based on the results of comprehensive scoring, the quality of
jujube powder prepared by vacuum freeze drying was the best, followed by vacuum drying and explosion puffing drying,
while jujube powder prepared by hot-air drying was the worst. However, high cost was needed for vacuum freeze drying
and vacuum drying. In conclusion, jujube powder prepared by explosion puffing drying has better overall quality with high
drying efficiency and low cost, which makes it suitable for extensive application in jujube powder processing industry.

Key words: explosion puffing drying, vacuum drying, hot air drying, vacuum freeze drying, jujube powder, quality characteristics