Study On Isolation,elucidation And Stability Of Monascus Yellow Pigment From Submerged Fermentation

Recently,a breakthrough in submerged fermentation of high color value Monascus yellow pigments has been achieved,which builds a solid base for its application in food industry.However,due to the complicate composition of fermentation broth,the pigment component remains unclear,as well as its stability.Therefore,this project aims to isolate and elucidate pigment components and study the stability of pigment,to provide more information of relation between pigment stability and its application in food industry,concerning food process and storage conditions.First of all,components in pigments were isolated by HPLC.Two major components showed on spectrum of analytical HPLC as two adjacent peaks,namely A and B.Resolution between A and B was 2.51.Then A and B were isolated on preparative HPLC on which elution condition was based on analytic HPLC with few adjustments,98.95% and 99.02% of purity respectively.Combing MS analysis with 1D NMR and 2D NMR data,A and B were elucidated as Monascin(C₂₁H₂₆O₅,molecular weight 358)and Monaphilone B(C₂₀H₂₈O₄,molecular weight 332).Color of pigment comes from its?,?-unsaturated ketone structure.Subsequent pigment only contained Monascin.Secondly,stability of pigment in oleoresin and water phase system was studied.The results showed that 88.05% of pigment reserved when heated under 100?,only 35.01% and 27.15%reserved stored under different light condition.In water phase system,pigment showed good resistance to thermal process while quite susceptible to light,with 73.33% color loss after 8 h of photobleaching of 850 lux light intensity;oxygen showed little influence during thermal and light degradation;Vitamin E,sodium erythorbate,EDTA and vitamin C could increase the color of pigment;Vitamin E and sodium erythorbate could improve color stability of pigment during photobleaching but showed no improvement during heating.Na⁺,K⁺,Mg²⁺,Ca²⁺ could cause chroma and lightness loss,and Ca²⁺ could bring a red tone to the pigment;pigment was stable in acidic environment.There was different mechanism behind color loss after thermal degradation and photo bleaching.In thermal process,it was chromophore in pigment molecule prone to disruption while it was auxo chrome tends to disappear.At last,Monascus yellow pigment was applied in real foods in different forms.The results showed that pigment could maintain vibrant yellow color in soft drink.When it was added into butter cookie and custard,a red tone was observed.Encapsulation showed some protection on the color tone of pigment in custard.Then investigation of color changing mechanism showed that it was unknown components,not Monascin that react with unionized amino group,and then produced red pigment,causing tone shifting to red.