Ultrasound-Assisted Biosorption Of Phenolic Compounds From Blueberry Pomace By Brewery Yeast

Blueberry is the fruit of the Ericaceae Vaccinium spp.Blueberry pomace is mainly produced during the processing of blueberry juice and wine.It is rich in anthocyanins and other phenolic compounds.It has anti-atherosclerosis,anti-aging and light-induced retinopathy properties.Brewer's yeast is a by-product of the beer production process.Yeasts have wide application prospect in the biosorption field because of their advantages of low cost and strong specificity of adsorption.Ultrasound was used to assist the biosorption and separation of anthocyanins from blueberry pomace by brewery yeast.The influence of sonication conditions on adsorption,adsorption kinetics,adsorption isotherms,adsorption mechanism and bioaccessibility of yeasts enriched with pehnolics were studied.Moreover,a brewer's yeast-polyphenol-lactic acid bacteria chewable tablet was developed.The quality changes of the tablets during storage was studied and the simulated digestion and colonic fermentation in vitro experiments were conducted.The results of the study were shown as follows:1.The influence of sonciation parameters on adsorption,adsorption kinetics and adsorption isotherms were studied.The results showed that the adsorption capacity of anthocyanins and total phenolics at ultrasonic intensity of 394 W/L was significantly higher than that of standing adsorption and the amount of adsorption under shaking(P<0.05).With the increase of adsorption time,the adsorption capacity of anthocyanins and total phenolics by brewery yeast increased and reached an equilibrium at 120 min.With the increase of ultrasonic intensity and temperature,the adsorption amounts of anthocyanins and total phenolics by brewer's yeast were increased.When the initial concentration of anthocyanin ranged from 60 to 180 mg/L,the equilibrium adsorption capacity of anthocyanins and total phenolics also increased with the increase of the initial anthocyanin concentration.When the concentration was higher than 180 mg/L,the equilibrium adsorption amounts increased slowly.The adsorption process of anthocyanins and total phenolics by brewery yeasts was best described using a second-order kinetic model(R2>0.999).The Temkin isotherm model could better describe the adsorption behavior of anthocyanins and total phenolics from blueberry pomace extracts by brewery yeast(R2>0.99).2.The adsorption mechanism of phenolic compounds by brewer's yeast was explored.The results showed that the brewer's yeast had different adsorption degrees on various anthocyanins and other phenolic compounds.FTIR results suggested that the amino,hydroxyl and amide groups of the brewery yeast surface may play a key role on biosorption of the phenolic compounds from blueberry pomace extracts by brewery yeast.These groups achieved the purpose of adsorption by hydrogen,electrostatic interaction and coordination complexes with phenolic substances.The results about particle size,Zeta potential,scanning electron microscopy and X-ray diffraction showed that the adsorption process includes physical adsorption and chemical adsorption.Surface adsorption was the main part and the inner cell adsorption was secondary.3.The effects of biosorption on the stability and bioaccessibility of phenolic compounds from blueberry pomace were studied.The results showed that the stability and bioaccessibility of total anthocyanins and total phenolics after adsorption were improved during simulated digestion and colonic fermentation in vitro.It can be seen that the biosorption can improve the stability of phenolic compounds from blueberry pomace during the digestion process,enhance its antioxidant activity and play a role in protecting the phenolic compounds from blueberry pomace.4.The brewery yeast powders enriched with phenolic compounds,passion fruit powder and lactic acid bacteria powder were used as raw materials to produce chewable tablets.Mannitol,microcrystalline cellulose and magnesium stearate were supplemented.Through single factor and orthogonal test optimization experiments,the brewery yeast-polyphenol-lactic acid bacteria chewable tablet with health effects was prepared.The results showed that the best formula for the brewer's yeast-polyphenol-lactic acid bacteria chewable tablets was ABY:passion fruit powder 6:4,mannitol 30%,microcrystalline cellulose 10%,magnesium stearate 1%,lactic acid bacteria powder 0.1%.The chewable tablet had the unique flavor of yeast and passion fruit with high nutritional value.With the prolonged of storage time,the total anthocyanins,total phenolic content and antioxidant activity in the brewery yeast-polyphenol-lactic acid bacteria chewable tablets decreased.After storage for 3 months,the aformentioned indexes decreased by 33.89%,28.59%,42.69%,and 28.96%respectively.The contents of anthocyanins and phenolic acids also decreased.The living number of lactic acid bacteria in the brewery yeast-polyphenol-lactic acid bacteria chewing tablets decreased,and the total number of colonies increased slowly.After storage for 3 months,the values were 4.17 log cfu/g and 179 cfu/respectively.The total anthocyanins and total phenolic contents in the chewable tablets remained relatively stable during simulated mouth and stomach digestion,while their antioxidant activity did not change significantly.However,they all significantly decreased after simulated intestinal digestion.The total anthocyanins contents significantly reduced.Total phenolic content and antioxidant activity increased slightly after simulated colonic fermentation.