Effects Of Vacuum Microwave Drying On Properties Of Pectin And Bioavailability Of Carotenoids In Carrot And Pumpkin

The recent research on the correlation between the changes of food structure and its bioaccessibility of nutrients during processing is a research hotspot in the food field in.Previous studies have found that vacuum microwave drying can effectively improve the bioaccessibility of carotenoids,but the regulatory mechanism is uncertain by now.In this study,carrots and pumpkins were used as raw materials to analyze the changes in characteristics of carrot and pumpkin cell wall pectin before and after vacuum microwave drying,and the effects of vacuum microwave drying on the bioavailability of carotenoids in tissues were investigated to provide a theoretical basis of efficient carotenoid bioavailability.The research results are as follows:1.The cell wall polysaccharide composition of pumpkin and carrot was analyzed.It has found that the two cell wall polysaccharides are mainly composed of galacturonic acid,arabinose,galactose,mannose,and glucose.The molecular weight of water-soluble pectin(WEP)of carrot cell wall was the largest,followed by alkali-soluble pectin(NEP),and the molecular weight of chelating pectin(CEP)was the smallest;the molecular weight of WEP of pumpkin cell wall was the largest,and the molecular weights of NEP and CEP were not significantly different.The CEP of carrot was high ester pectin and the rest are low ester pectin.2.The changes of cell wall and polysaccharide composition of carrot and pumpkin slices after vacuum microwave drying were analyzed.After vacuum microwave drying of the two vegetables,the pore size formed at the microwave power of 9 W/g was more uniform,the surface area was the largest and the structure was the most uniform.The study of cell wall components showed that the cell walls of carrot and pumpkin slices were broken,the degradation of cell wall polysaccharides was significant,the pectin molecular chain was broken,the molecular weight was decreased,WEP,NEP content decreased,and CEP content increased.With the increase of microwave power,the linearity of carrot NEP,pumpkin WEP and NEP decreased,the linearity of carrot CEP and pumpkin CEP increased,the content of unsaturated galacturonic acid(UG)and the degree of esterification of pectin increased first and then decreased.When the microwave power was 9 W/g,the degree of methoxylation of pectin was the highest,and the β-elimination reaction occurred more thoroughly.3.The effect of vacuum microwave drying on the bioaccessibility of vegetable carotenoids was analyzed.The study found that vacuum microwave drying has a significant effect on carotenoid retention and its bioaccessibility.The carotenoid retention rate showed a decreasing trend with an increase of microwave power.The bioaccessibility of carotenoids increased first and then decreased with an increase of microwave power.When the microwave power was 9 W/g,carotenoid bioaccessibility was significantly higher.The highest rate is consistent with the trend of cell wall polysaccharide degradation.4.The changes of cell wall structure after in vitro digestion of fresh and drying carrot and pumpkin were analyzed.It was found that fresh vegetable samples still had intact cell structure after in vitro digestion.Carotenoids were mainly distributed on the inner side of the cells and were not released into the digestive juice.The vacuum and microwave dried carrot and pumpkin samples were completely broken after in vitro digestion.A large area of discrete flocculent structures is present,and carotenoids are more uniformly dispersed in the digestive fluid in the form of small clusters.The viscosity of digestive fluid of carrot and pumpkin samples after vacuum microwave drying was significantly lower than that of fresh samples,but the microwave power changes were not significant.