Processing Technology Of Jujube Blackening And Effect Of Humidity On Its Quality

During the processing,Maillard reaction occurs to make jujube blackening appear dark brown and the product has a unique sweet smell.This product does not add any additives which is a product of its own reaction.In this paper,the jujube of the half red date is used as raw material to optimize the processing conditions so as to achieve the best taste,fragrance,texture,etc.The effects of different humidity on the indexes of jujube blackening and the antioxidant activity of jujube blackening were studied,which provided the theoretical basis for the follow-up study.The main results are as follows:The effects of processing time,temperature and humidity on sensory score,hardness,elasticity and chewability were studied.The optimum conditions for the production of jujube were processing time 25 d,processing temperature 65 ℃ and processing humidity40%.On the basis of single factor,response surface optimization test was carried out to further optimize the technological conditions of the products.Processing time,temperature and humidity were selected as three factors.Sensory score,hardness,elasticity and chewability were used as response values.The optimum technological conditions were obtained: processing time 22 d,processing temperature 66 ℃ and processing humidity 39%.At this time,the sensory score of the product is 91.2,the hardness is 2.9N,the elasticity is3.3mm,and the chewability is 3.1m J.Under this condition,the product has the highest sensory score,good hardness,elasticity,chewability,good quality,rich jujube flavor,with sweet and burnt flavor,moderate sour and sweet degree,and dark brown color.The results showed that the processing humidity had a effect on the formation of quality of jujube processing.In this paper,it shows that the higher the humidity,the higher the content of water,reducing sugar,total phenol and total flavone,but the lower the browning degree and titratable acid.When the browning degree reaches about 73,it can be judged that the jujube is mature by processing.And it is the lower the humidity,the shorter the time needed to reach the mature color of jujube processing.During the whole process,water content and total flavone content decreased,reducing sugar content and total phenol content increased first and then decreased,browning degree and titratable acid increased.The free radical scavenging ability of jujube blackening was higher than that of fresh jujube.Among them,DPPH and ABTS scavenging ability changed obviously.DPPH and ABTS free radical scavenging rates of fresh jujube were 30.91% and 14.96% respectively.DPPH and ABTS free radical scavenging rates of jujube blackening 58.74% and 42.51%respectively.The iron content of fresh jujube and jujube blackening was 1.19mg/L and2.21mg/L respectively.