Peanut drying:Effects of various drying methods on drying kinetic models,physicochemical properties,germination characteristics,and microstructure

The current work aims to explore the suitable drying technique for peanut pods which can be used for seeds or edible peanuts.Four drying methods,namely naturally-open sun drying as the control check(CK),hot air drying(HAD),pulsed vacuum drying(PVD),and radio frequency combined hot air drying(RF-HAD),were employed to dry peanut pods,and their effects on the nutritional quality attributes in terms of protein,fat,fatty acid contents,etc.,germination characteristics,microstructure,color,texture,acid value and peroxide value of peanuts were explored.Mathematical models of peanuts drying with four drying methods were also established.According to the statistical parameters including the determination coefficient(R^(2))、root mean square error(RMSE)and chi-square value(v^(2)),theWeibull model was best for predicting the moisture ratio change kinetics of peanuts during its four drying processes.There were significant differences in physicochemical indexes of peanut by different drying methods(p<0.05).Fat and oleic acid contents under RF-HAD were significantly higher than those by the other three drying methods.Compared with the naturally-open sun drying,RF-HAD reduced drying time by 76.70%and the microstructure of RF-HAD peanuts produced larger and more cavities.The RF-HAD kept better comprehensive nutritional quality,but the germination rate was reduced by 27.80%.PVD could maintain good nutritional quality and germination rate among these mechanical drying technologies.However,PVD had a longer drying time of 9.5 h than RF-HAD and HAD,and the microstructure of pulsed vacuum dried peanuts showed dense structure and less cavity.Hot air-dried peanut kernel held the highest protein(28.75%),fatty acids contents(26.11%)and germination rate(88.00%).However,peanut kernel dried by HAD showed poor qualities,such as high acid value,peroxide value and large color changes.These findings indicated RF-HAD was a promising drying technique for edible peanuts regarding the higher drying rate and better-quality preservation,while HAD was suitable for peanut seeds drying as it could well protect the germination rate.

Optimization of drying conditions and components to reduce wall sticking during spray drying of infant formula milk

Wall sticking,which greatly reduces productivity and product quality,has been a big challenge of spray drying.Structure of drying tower and atomizer,as well as drying conditions are the main influencing factors.This research explored the possibility to reduce wall sticking by optimizing drying conditions and components to obtain higher recovery rate of powdered infant formula milk(PIFM).Response surface experimental results indicated that inlet air temperature(T),feed concentration(C),feeding speed(S),as well as interaction term of TC and quadratic terms of C^(2) and S^(2) had significant influences on recovery rate for determined milk formula.According to mixture experiments at optimized drying conditions,whey protein(P),fat(F)and lactose(L)contents,as well as interaction term FL had significant effects on recovery rate.Positive effects were observed for F and L contents on recovery rate,while negative effects were observed for P and FL.Under the optimized drying condition of 136℃,19.80%and 4.07 mL/min,respectively,for T,C and S,the maximum recovery rate of 58.98%was obtained for PIFM with P,F and L content of 18%,31%and 51%,respectively.Wall sticking phenomena could be reduced by optimizing drying conditions and mildly adjusting components of infant formula milk.

Moisture sorption and thermodynamic properties of Camellia oleifera seeds as influenced by oil content

Moisture sorption isotherms and thermodynamic properties of Camellia oleifera seeds as influenced by oil content were investigated.Moisture desorption and adsorption isotherms of Camellia oleifera seeds,kernels and shells from three varieties were determined using constant temperature and humidity chamber method at different temperatures(10°C,25°C,and 40°C)with water activity ranging from 0.20 to 0.90.Six selected mathematic models were employed to fit the experimental data.The Peleg model gave the best results for both seeds and kernels and Langmuir model was the best for shells.The difference of equilibrium moisture contents at the same water activities during desorption and adsorption indicated the occurrence of hysteresis of adsorption processes and the equilibrium moisture contents tended to decrease with the increasing oil content and temperature.The binding energy and average capacity per unit mass decreased with increasing temperature and oil content.The relationships between water activity and the logarithm of sorption activity showed the capillary porous body characteristics of the seeds.