Summer is here, and the season of lychee is coming soon. And when it comes to lychee, I have to mention Du Mu’s well-known saying “When a concubine rides the red dust and laughs, no one knows it is lychee”. The main reason is that the shelf life of lychees is really bad. Bai Juyi once described lychees in the “Preface to Lychees”, “If you leave the original lychees, the color will change in one day, the fragrance will change in two days, the taste will change in three days, and the taste will change in four days. Outside the sun, the color and fragrance are all gone.”
Nowadays, due to the improvement of food freezing technology. The scientific research project jointly launched by South China Agricultural University and Dejieli has also officially started operation. South China Agricultural University is located in Guangzhou City, Guangdong Province. It is a national key university and a national “double first-class” construction university. It is a provincial-ministerial co-construction university jointly established by the Guangdong Provincial People’s Government and the Ministry of Agriculture and Rural Affairs with its advantages in agricultural science and life science.
The research object of this project is also lychee. In order to explore the freeze-thaw characteristics of lychee and determine its suitable freeze-thaw method, this research will use Dejieli tunnel-type liquid nitrogen quick-freezing machine to spray quick-freeze with liquid nitrogen (-40℃ to -100 ℃) and gradient thawing (-20 ℃ ~ 25 ℃) on the freeze-thaw characteristics and quality of litchi, and compared with traditional freezer freezing, immersion freezing, and room temperature thawing. Observation: Within a certain temperature range, the lower the liquid nitrogen temperature, the shorter the time to pass through the maximum ice crystal formation zone, and the better the protection effect on frozen litchi; -100 ℃ liquid nitrogen tunnel line quick freezing combined with “-20 The gradient thawing in the ℃~25 ℃” group can maintain the data of fresh litchi nutrients and bioactive substances (polyphenols, soluble sugar, Vc content, water loss, hardness retention, and integrity of cell structure). Comprehensively, whether the freezing and thawing method of liquid nitrogen tunnel line combined with gradient thawing can better maintain the quality effect of its fresh litchi, and the research results of the project can provide technical support for the industrial storage and processing of litchi in the future.
