| Dietary fiber(DF)is one class of material that is derived from plants,animals,microorganisms and so on.It can't be digested and absorbed by human digestive system but has important physiological functions.DF mainly includes substances such as cellulose,lignin,pectin.Soluble dietary fiber(SDF)generally accounts for 30%-50%of total amount of DF which is regarded as high quality.Conventional preparation methods of DF include chemical,physical and biological ones.There is a large amount of waste water in the process of chemical and physical method and the yield and propertises of the product can't be improved obviously.The enzymatic method is suitable for raw materials with higher content of starch and protein.Microorganism fermentation can significantly improve the SDF content and make the function of the product more balanced,which attracted attention of the industry.Citrus dregs is by-product of citrus processing industry which is riched of pectin,cellulose,Vc and flavonoids.Retention of citrus dregs in the industry is as high as 50%,which is a good resource to prerare DF.Research on solid fermentation to improve the SDF content of citrus drges was seldom and there are no special strains till now.In the study,a Penicillium sp.that suitable for solid citrus dregs culture medium was screened,the safety of the strain was evaluated,the process to improve the SDF content in citrus dregs was optimized,and the main composition and the various properties before and after fermentation of citrus dregs were compared.The results were as follows:A filamentous fungi with high cellulase activity,obvious transparent circle on the Congo red-cellulose culture medium,high heredity stability,suitablity for solid citrus dregs culture medium,named CIs16,was isolated from moldy citrus fruit.The strain was identified as Penicillium sp.through morphologic characters investigation and 18S rDNA sequence analysis and named as Penicillium sp.CIs16.Acute toxicity experiment with mice through mouth feed showed that citrus dregs with living strains after digested by pectinase and fermented by Penicillium sp.CIs16 was non-toxic.Preliminary test showed that SDF content of the product fermented by Penicillium sp.CIs16 was 23.52%,which was significantly higher than unfermented(P<0.01);TDF content was 83.24%,which was significantly higher than unfermented(P<0.01);the SDF/TDF was 27.62%,which was significantly higher than unfermented(P<0.01).Effects of amplification ways of the seed culture medium,comparation with Trichoderma Viride,and various fermentation conditions on the yield were studied.The better fermentation conditions when fermented with Penicillium sp.CIs16 were as follows:citrus dregs in a peel and slag ratio of 2:1 in the fermentation culture medium,the inoculation amount was 20%(g/g)and the fermentation was conducted under 28 ? for 3 d.Under above conditions,the SDF content in the fermented products was 36.56%,the TDF content was 70.34%,and SDF/TDF was 51.97%,which were all significantly higher than the unfermented citrus dregs(P<0.01).Properties experiments showed that the water-holding capacity of fermented citrus dregs was 7.21 g/g which was significantly higher than unfermented(5.74 g/g,P<0.01);swelling capacity of fermented citrus dregs was 9.65 mL/g wich was significantly higher than unfermented(7.27 mL/g,P<0.05);cation exchange capacity of fermented citrus dregs was significantly higher than unfermented(P<0.05).Nitrite ion and cholesterol adsorption abilities in vitro were't improved.The scavenging rates on DPPH and ABTS free radical of fermented citrus dregs were higher than those of unfermented.The DPPH and ABTS free radical scavenging rates of fermented citrus dregs in IC50 were 4.700 mg/mL and 7.278 mg/mL respectively,which were higher than those of unfermented citrus dregs(5.378 mg/mL and 8.312 mg/mL respectively).The correlation between concentration and free radical scavenging rate of fermented citrus dregs was less than that of unfermented. |
PDF Full Text Request