Dehydration And Powder Technology And Quality Attributes Of Lycium Barbarum

In this study,fresh Lycium barbarum were used as raw materials to study the effect of single and combined drying methods on its basic characteristics and processing quality,and the optimum drying conditions were obtained.Moreover,the effect of superfine technology on the physicochemical of Goji powders had been investigated.Because of the caking and agglomeration problems during Goji powders storage,based on the theory of water activity and glass transition concepts,the storage stability of Goji powders was further studied.The main conclusions are as follows:Study on single drying technology of fresh Lycium barbarum.Results showed that the fresh Lycium barbarum which soaked in 2%Na₂CO₃ solution for 1 min with the ratio of solid to liquid of 1:10 could significantly shorten the drying time,speed up the drying rate,and improve the overall quality of dried Goji.There was no significant difference in the drying efficiency and drying quality of hot air drying and heat pump drying of Goji.Compared with the constant temperature and humidity drying,stage-varied temperature drying could increase the drying rate and shorten the drying time while ensure the quality of the dried product.The best drying condition is:After 2%Na₂CO₃ pretreatment,the drying temperature is 40°C?2 h?-45°C?4 h?-50°C?6 h?-55°C?10 h?,drying relative humidity is 40%.Study on combined drying of fresh Lycium barbarum.It was determined that the preferred combined drying method was freeze drying?FD?-instant controlled pressure drop drying?FD-DIC?.The process was:explosion puffing temperature of 90°C for 15min,followed by vacuum drying at-0.1MPa and 60°C for 1.5h.Under this process,the products has the highest overall quality:the product has the highest contents of total phenol?11.30 mg GAE/g?,polysaccharide?139.8 mg/100 g?,and antioxidant activity of FRAP?43.69?mol TE/g?and ABTS?57.55?mol TE/g?,respectively.Meanwhile,under the same drying conditions,the FD-DIC products had the lowest moisture content?12.71 g/100g?and highest the glass transition temperature?16.70°C?,which make it more stable at room temperature.Quality analysis and processing behavior of Goji Powder?LB1-LB4?with different particle size distribution.The color,moisture content and hygroscopicity of Goji powder decrease with decreasing of particle size,while the glass transition temperature increases.The dynamic flow energy test,shear cell,and compressibility were used to characterize the flow properties of the Goji powders with different particle sizes.Results showed that the Goji powder's flowability became worse as the particle size decreased.Besides,the nutritional properties were also studied,the total phenolics,flavonoids and antioxidant activity of LB1-LB3 had no significant differences,however,phenolic and flavonoid contents,and antioxidant activity of LB4 increased significantly.Study on storage stability of Goji powder.The effect of 2%addition of magnesium stearate?MgSt?,calcium stearate?CaSt?and silica?SiO₂?on the storage stability of Goji was investigated.Based on the water activity and T_g theory,the state diagrams of different Goji powders were constructed.The results showed that the corresponding glass transition temperature at the monolayer moisture content was Goji13.10°C,and Goji+SiO₂,Goji+MgSt,and Goji+CaSt were 14.80°C,19.22°C and 19.25°C,respectively.It shows that the addition of anti-caking agent can significantly improve the moisture-blocking effect of the powder.Combined FT4 Test of Goji powder moisture absorption result,the three anti-caking agents have the effect of inhibiting the moisture absorption of Goji powder in the following sequence:CaSt>MgSt>SiO₂.