The Production Of Neo-kestose And Carotenoid By Phaffia Rhodozyma And Their Applicaton In Yogurt

The Phaffia rhodozyma can catalyze high concentration of sucrose to neo-kestose with high value-added carotenoid accumulation.Neo-kestose is a new oligofructose that binds fructosyl with the glucose group in sucrose byβ-（2,6）glucoside bond,which has higher probiotic ability.Carotenoid is a natural,non-toxic,colorful,and highly bioactive carotenoid,which has 10 times antioxidant capacity thanβ-carotene and 500 times than vitamin E and is known as"super vitamin E".Microencapsulation has the advantage of improving carotenoid stability,concealing unpleasant taste,protecting active substances from decomposition and so on.In addition,microencapsulation can also turn liquid fat into solid,which is convenient for production,storage and use.Yogurt,with natural fermented aroma,delicate and smooth texture,can effectively alleviate lactose intolerance.However,there are some problems such as poor stability,low consistency,rapid decrease of probiotic number and poor antioxidant capacity.Therefore,it’s important to add appropriate prebiotics,stabilizers or thickeners during the processing of yogurt.The addition of carotenoid has a direct effect on the color and antioxidant capacity of yogurt.First,we studied the optimal medium components of P.rhodozyma in the fermentation process in order to improve the activity ofβ-fructofuranosidase and carotenoid accumulation.We optimized the fermentation parameters by single factor experiment and uniform design optimization.The optimum medium for biomass,enzyme activity and carotenoid accumulation was sucrose 21.56 g/L,peptone 26.50 g/L,KH₂PO4 1.02 g/L and Na₂HPO41.06 g/L.The final biomass was 8.31 g/L,carotenoid was 60.73 mg/L,neo-kestose was 49.46g/L by 10 g/L dry P.rhodozyma cells catalyzing 300 g/L sucrose solution 60 min.Then,we collected P.rhodozyma cells to catalyze 300 g/L sucrose solution to produce neo-kestose by optimizing the cell concentration,sucrose concentration,conversion temperature and pH to explore the effect of different catalytic conditions.The results showed that:the best optimal condition was 10 g/L dry P.rhodozyma cells catalyzing 300 g/L sucrose solution 90 min at 22℃.The amount of neo-kestose increased with the increasing of sucrose concentration over 300 g/L under the same condition,indicating that high sucrose concentration could inhibit hydrolase activity.It was not favorable for the accumulation of neo-kestose with the increase of cell concentration for P.rhodozyma cells during the growth period in 72 h or 84 h;the most suitable p H for P.rhodozyma catalyzing sucrose to produce neo-kestose were weak acidic condition.Furthermore,carotenoid was extracted by acid heat method,then encapsulated by MCC and CMC-Na.MCC has strong oil absorption characteristic,and it could form into an effective three-dimensional network structure with hydrogen bond after high shear force dispersion.The encapsulation of carotenoid improved its stability,solubility,antioxidation activity and could be applied potentially in industries.The encapsulated efficiency and solubility of microencapsulated carotenoid were 58.76%and 52.88%,respectively.In comparison with non-encapsulated carotenoid,the encapsulation of carotenoid did prevent carotenoid from dramatically degradation;the value of carotenoid retention in microencapsulated carotenoid was 80.86%at 55℃in 16 hours.Non-encapsulated carotenoid was much more stable in acid phase than neutral,but no significant difference in microencapsulated carotenoid.In the end,the effect of adding neo-kestose and microencapsulated carotenoid on the yogurt was studied.The stability of yogurt adding microencapsulated carotenoids increased9.41%compared with plain yogurt.After 10 times dilution,the DPPH-scavenging activity increased about 3%.There is no significant difference between the numbers of lactic acid bacteria.May be the produce of acid during early period was fast,which would inhibit the growth of Bifidobacterium or Lactobacillus bulgaricus;With color determination,△L=9.41,△a=8.04,△b=6.69,grater than 0 showed the color of yogurt adding encapsulated carotenoid was red orange yogurt.The number of lactic acid bacteria was 7.0×10⁸ CFU/m L and the plain yogurt was 5.5×10⁸ CFU/mL,which showed that the neo-kestose had a probiotic effect.Study on neo-kestose and carotenoid of P.rhodozyma related products can improve the commercial value and promote the industrial application of P.rhodozyma.