Effects Of The Hot Air Drying On The Liberation Of Carotenoids In Vegetables

Carotenoids in vegetables are abundant in content with a variety of physiological functions,however,the liberation of them is significantly low.The structure of the cell wall and the chromosomes are the main barriers to the release of carotenoids in vegetables.Suitable processing can destroy this barrier to improve the liberation of carotenoids.In this paper,carrot,yellow pepper,sweet potato and broccoli were selected as raw materials to determine the structure of cells,the existence form of carotenoids and the effects of hot air drying and oil combined hot air drying on the content and liberation of carotenoids.The study will provide theoretical guidance for improving the liberation of carotenoids of dehydrated vegetables.The main results are as follows:1.Identified the carotenoids in four kinds of vegetables,8 kinds of trans carotenoids including epoxy-carotenoids(neoxanthin,neochrome,violaxanthin,anterxanthin),hydroxyl-carotenoid(lutein,zeaxanthin)and carotene(α-carotene,β-carotene)were identified.The types of carotenoids were identified in carrot and sweet potato broccoli and yellow pepper was 3,3,5 and 7,respectively.2.The cell morphology and microstructure of vegetables were analyzed.The results showed that the size of cells was yellow pepper>sweet potato>carrots>broccoli from large to small.The cell walls of four kinds of vegetables showed fibrous shape,and the intercellular adhesion was good,among which cell walls of carrot and sweet potato had a different degree of degradation.Carotenoids in the carrots and sweet potato existed in chromoplast in the form of crystal structure,and a large content of starch was obesrved in yellow pepper.Carotenoids in yellow pepper were discovered primarily in the form of membranous and globular structure existed in chromoplast.Besides,carotenoids in broccoli combined with protein storaged in chloroplast.3.The effects of hot air drying on the retention rate of carotenoids in vegetables were studied.The results showed that the content of carotenoids in four kinds of vegetables decreased significantly(P<0.05)after hot air drying.And the retention rate of carotenoids gradually decreased with the hot air temperature increased.The retention rates of various carotenoids were significantly different,and the retention rates were from low to low the lutein>α-carotene>β-carotene.And the retention rates of carotenoids in vegetables were significantly different,and the retention rates were from high to low broccoli>sweet potatoes>yellow pepper>carrots.4.The effects of hot air drying on the liberation of carotenoids in vegetables were studied.The results showed that there existed some differences in the liberation of carotenoids in the four vegetables after dehydration.The liberation of carotenoids in carrot and yellow pepper increased,however,sweet potato and broccoli showed a decreasing trend.The highest liberation occurred at 70℃ in carrot,but at 80℃ in yellow pepper.And the lowest liberation occurred at 70℃ in sweet potatoes,but at 80℃ in broccoli.5.The effects of hot air drying combined with oil treatment on the release rate of carotenoids in vegetables were investigated.The liberation of carotenoids in four vegetables increased significantly after the addition of oil.After adding oil,the liberation of carotenoids in carrots increased by 1.2-4.5 times,1-25 times in yellow peppers,3-9 times in sweet potatoes,and 5-36 times in broccolis,respectively.At the same time,the release amount of carotenoids in the four vegetables was significantly higher than that of the fresh ones.