| Broccoli belongs to Brassica oleracea Lvar.italica,which is a kind of vegetable variety with high nutritional value and medicinal value.It is rich in a variety of bioactive components.Broccoli has many physiological functions,such as anti-oxidation,prevention of diseases and cancer,and improvement of immunity.Only after being digested and absorbed,the nutrients in fruits and vegetables can be utilized in human body.Ultrasound treatment can regulate the bioavailability of bioactive compounds in fruits and vegetables,but the specific mechanism is not clear.In this paper,the effects of ultrasound treatment on the bioavailability of carotenoids,sulforaphane,phenols,ascorbic acid were evaluated by simulating micellization coupled with Caco-2 cells in vitro with broccoli as the object.By analyzing the effect of ultrasound treatment on cell wall structure,polysaccharide composition and digestion characteristics of micelle in different digestion stages,the mechanism of ultrasound treatment to regulate the bioavailability of bioactive compounds was clarified.The results are as following:1.The effects of ultrasound treatment on carotenoids,sulforaphane,phenolic compounds,ascorbic acid content and bioavailability were analyzed.The results showed that the effect of ultrasound treatment on the content rate of bioactive compounds in broccoli was significantly different.With the increase of ultrasound time,the release rate of carotenoids and phenolic compounds increased significantly,the release rate of sulforaphane increased first and then decreased,and the retention rate of ascorbic acid decreased significantly.The bioaccessibility of four kinds of bioactive compounds increased significantly with the extention of ultrasound time.When the broccoli was treated for 120 minutes,the bioaccessibility of carotenoids,sulforaphane,phenolic compounds and ascorbic acid increased by 62-90%,50%,51-71%and 21%.In addition,the cellular absorption of carotenoids,sulforaphane,phenolic compounds and ascorbic acid were significantly promoted by ultrasound treatment,among which the cellular absorption of carotenoids increased the most,reaching 93-120%.2.The effects of ultrasound treatment on the cell wall and polysaccharide components of broccoli were analyzed.Results showed that the microstructure of broccoli was obviously damaged after ultrasound treatment,in which the cell wall was broken and the inner membrane of the cell was disintegrated.The study of cell wall components showed that ultrasound treatment degraded broccoli pectin,reduced the content of neutral sugar,and shortened the side chain length.It was found that ultrasound treatment breaks the pectin glycoside bonds of the cell wall and reduces the molecular weight of pectin.The longer the ultrasound treatment time,the lower the molecular weight of pectin.In addition,the study found that ultrasound treatment could also increase the degree of pectin esterification and the content of unsaturated galacturonic acid in broccoli,further confirming the destructive effect of ultrasound treatment on the cell wall.3.The effect of ultrasound treatment on the digestion characteristics of micelles at different digestion stages was analyzed.The results showed that the average particle size of the micelle decreased after ultrasound treatment.The longer the sonication,the smaller the particle size and the more uniform the distribution,which can be absorbed more easily.The particle size of the micelles in intestinal phase was smaller than that in gastric phase.Further,The zeta potential of micelles reduced significantly after ultrasound treatment,while the stability of micelles was improved.The micelle in intestinal phase was more stable.In addition,ultrasound treatment made the viscosity of micelles significantly decreased.The longer the sonication,the more the reduction.At the same shear rate,the viscosity of digestive mixture in intestinal phase is lower than that in gastric phase,which is more beneficial to the absorption of bioactive compounds. |
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