| Steam explosion technology was first applied to the treatment of wood cellulose in the last century.It is the use of instantaneous release of steam to pretreat raw materials,so that cellulose,hemicellulose and other substances efficiently hydrolyzed to promote the release of active substances,and the treatment process is relatively environmentally friendly,and in recent years gradually applied to the development and utilization of agricultural and by-product resources.Pomegranate peel,as a processing by-product of products such as pomegranate wine,is rich in active ingredients with high medical research value.In this study,steam explosion was applied to the pretreatment of pomegranate peels to evaluate the effect of steam explosion on the treatment of pomegranate peels by investigating the effects on the phenolic content,antioxidant activity and in vitro simulated digestion of pomegranate peels.The main studies were as follows:(1)The effects of steam explosion on the structure,content of phenolic compounds and some major active substances and antioxidant activity of pomegranate peel were investigated under steam explosion pressure of 0.5-2.0 MPa,steam explosion duration of 30-180 s and particle size of 20-100 mesh.The results showed that the surface fragmentation of pomegranate peels increased with the increase of steam explosion pressure and steam explosion duration.The optimum conditions for steam explosion of pomegranate peels were 1.5 MPa steam explosion pressure,120 s steam explosion duration and 40 mesh particle size,and the highest total phenol content of 203.61 mg GAE/g was achieved under this condition,which was 18.13%higher than that before steam explosion.The three influencing factors on the total phenolic content and phenolic compounds of pomegranate peel were in the order of:steam explosion duration > steam explosion pressure > particle size.After steam explosion,the content of punicalagin and punicalin in pomegranate peel was significantly reduced,and the content of ellagic acid and gallic acid was increased.(2)The changes in the content of phenolic compounds,major active substances and antioxidant activity of pomegranate peels before and after in vitro simulated digestion after steam explosion under different conditions were investigated.The results showed that during the simulated digestion,variation of the total phenolic content,the content of four phenolic compounds,and antioxidant activity of the steam-exploded pomegranate peel is higher than unexploded pomegranate peel.The relative degree of change in the content of the four phenolic compounds,during the simulated digestion,was ellagic acid ≥ punicalagin > punicalin > gallic acid.The antioxidant activity tended to increase and then decrease with the increase of steam explosion pressure and steam explosion duration,and the overall variation with particle size was not significant.(3)The effect of pomegranate peel on α-amylase and α-glucosidase before and after simulated in vitro digestion after steam explosion was investigated.The results showed that the inhibition rates of α-amylase and α-glucosidase were not significantly different between the pomegranate peel digests before and after steam explosion pretreatment.The inhibition rate of α-amylase and α-glucosidase increased with increasing concentration in the pre-digestion and gastric digestion groups of pomegranate peel digest,and the maximum inhibition rate was 73.66% and 38.14%,respectively.The inhibition effect was not significant in the intestinal digestion group,and there was even a promotion of α-amylase.The types of enzyme inhibition by pomegranate peel before digestion,before and after pretreatment by steam explosion were all of mixed type non-competitive inhibition.Pomegranate peel digest had some fluorescence quenching effect on α-amylase and α-glucosidase,and the effect was more obvious with increasing concentration of pomegranate peel digest both before and after gastric digestion,while there was no significant pattern in intestinal digestion. |
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