Effect Of Hot Air Drying And Vacuum Microwave Drying On The Liberation Of Carotenoids In Pumpkin(Cucurbita Moschata)

Cell wall,cell membrane and the membrane structure of chromoplast present in fruits and vegetables are the natural physical barriers to hinder the release of carotenoid.Proper processing can destroy such barriers to increase the release of carotenoids.In this paper,the effect of hot air drying and vacuum microwave drying on the cell morphology and beta-elimination reaction in pectin,as well as the different drying conditions in the two kinds of drying methods and the addition of grease on the retention rate and liberation of carotenoids,were studied with "melon" pumpkin as raw material to explore the mechanism of affecting the release of carotenoids.The main results are as following:1.In the hot air drying,the content of unsaturated galacturonic acid(UG)in pumpkin increased with the increase of the hot air temperature and heating time,and the effect of temperature on UG content was more significant.In vacuum microwave drying,UG content increase first and then decrease with increasing microwave power.Under the same moisture content,the UG content of vacuum microwave drying samples was higher than that of hot air drying.2.In the hot air drying,the retention rate of carotenoids was not significantly different at different drying temperatures.But with the increase of drying time,the retention rate decreased gradually.The retention rate of carotenoids in vacuum microwave drying was significantly higher than that in hot air drying,and the retention rate was the highest at 6 W/g.The retention rates of lutein,α-carotene and β-carotene were more than 70%at this power.3.During the hot air drying,the liberation of lutein,α-carotene and β-carotene increased with the increase of drying temperature and the prolongation of drying time.In the vacuum microwave drying,the liberation of α-carotene and β-carotene increased first and then decreased with the increase of microwave power.4.When the drying terminal point(moisture content below 5%)is reached,the liberation of carotenoids in pumpkin is reduced after hot air drying.Nonetheless,it was significantly increased after vacuum microwave drying,and the highest liberation ofα-/β-carotene occurred at 12 W/g,they were 49.82% and 40.17% respectively.5.The addition of oil can effectively promote the release of carotenoids.After the addition of oil,the increased magnitude of liberation in the dehydrated samples is much higher than that of fresh samples.Compared with the treatment of hot air drying at 80 ℃,the liberation of α-carotene and β-carotene was increased by 26.5 times and 27.1 times after hot air drying combined with oil treatment at 80 ℃,respectively.This indicates that the presence of oil can effectively promote the release of carotenoids.6.Both of the two drying treatments can change the structure of pumpkin and degrade the cell wall to promote the release of carotenoids,but excessive thermal processing would form a new physical barrier within the material to prevent its release.The presence of grease can reduce the polarity of the digestive juice to promote its release.