Effects And Application Of Flavonoids On Pigments And Citrinin In Yam Fermented By Monascus

Monascus,as a medicinal and edible filamentous fungus,can produce a large amount of Monascus pigment which is widely used in the food industry.However,when Monascus produces pigments,it is often accompanied by the production of mycotoxins-citrinin,which restricts the further promotion and application of Monascus products to a certain extent.Therefore,how to effectively reduce or even eliminate the production of citrinin during the fermentation process of Monascus has become one of the research hotspots at home and abroad.The yam contains a variety of functional components that confer a variety of biological activities.However,there are few studies on the effects of Monascus fermented yam on the production of citrinin and pigment.Flavonoids have a variety of biological activities.Whether flavonoids can affect the pigment and citrinin in Monascus fermented yam is rarely reported.Therefore,in this paper,yam was used as the fermentation substrate,and flavonoids were added during the solid-state fermentation and liquid fermentation of Monascus to study their effects on the production of pigment and citrinin from the fermented yam of Monascus.Then a red yeast yam drink was initially designed.The main research contents and results are as follows:(1)The process of solid-state fermentation of Chinese yam and Iron stick yam by Monascus was optimized,and on this basis,the effects of luteolin and genistein on the production of pigment and citrinin by Monascus were investigated.Under the scanning electron microscope,the surfaces of the two unfermented yam were relatively smooth,without obvious voids,and the particle size was large,mainly oval.The surface of these two kinds of yam fermented by Monascus is irregular block,dense structure,less porous structure,and the structure of fermented yam after adding the above flavonoids was looser,with honeycomb-like and porous structure,indicating that the two flavonoids had a great impact on the morphological structure of yamfermented by Monascus.Under the optimized fermentation conditions: Chinese yam needs to be dried for 3 h before fermentation,the amount of yam is 25 g/250 m L erlenmeyer flask,and it needs to be fermented at 28 °C for 18 d;before fermentation,iron stick yam needs to be dried for 4 h,and the amount of yam is 20 g/250 m L erlenmeyer flask,fermented for 18 days at 28°C.It was found that adding 0.2 g of luteolin and genistein,respectively,the content of citrinin in Chinese yam fermented by Monascus reducedby48% and 72%,respectively;The doses of these two flavonoids,citrinin content in Iron stick yam fermented by Monascus,decreased by 55% and 74%,respectively.In the two kinds of yam,the changes of pigments were similar.The addition of genistein had little effect on the pigment production of Monascus,while the content of pigments was increased by luteolin significantly.(2)The liquid fermentation culture conditions of Monascus yam powder were optimized,and the effects of adding luteolin and genistein respectively or adding these two flavonoids simultaneously on the production of pigment and citrinin by Monascus were investigated.The results showed that when the Chinese yam powder was used as carbon source,adding 2.0 g/L luteolin and genistein could reduce the content of citrinin in Monascus fermentation broth by 24% and 63%,respectively.When Iron stick yam powder was the carbon source,adding 2.0 g/L luteolin and genistein could reduce the content of citrinin in the fermentation broth of Monascus by 44% and 75%,respectively;adding 1.0 g/L genistein and 0.5 g/L luteolin were added to the yam powder medium simultaneously,the content of citrinin in the fermentation broth decreased by 88.2%,the contents of yellow pigment,orange pigment and red pigment in the fermentation broth of Monascus were 1.53,1.63 and 1.3 times higher than those in the group without flavonoids,respectively.The addition of genistein can significantly reduce the content of citrinin in Monascus fermented yam powder,and the addition of luteolin can significantly improve the yellow pigment.By adding luteolin and genistein simultaneously,it can not only effectively reduce the citrinin in the fermentation product,but also increase the content of Monascus pigment.(3)UPLC-QTOF-MS was used to analyze the metabolites of yam fermented by Monascus.In addition to four kinds of Monascus pigments,75 compounds were preliminarily identified.Among them,many important metabolites such as lysine,arginine,glycine,glutamic acid,tyrosine,isoleucine and phytosphingosine were found.It was initially found that after adding flavonoids,the metabolites of Monascus Iron stick yam after fermentation were basically the same as those when flavonoids were not added.(4)Designed the production process of red yeast yam drink.Through single factor and orthogonal test,the optimal formula of beverage was determined,and sensory evaluation and biochemical index detection were carried out.Finally,a safe,non-toxic,high nutritional value,red yeast yam drink with red yeast rice flavor and yam fragrance is prepared.