The Preparation And Application Of Liquid Whey Protein Concentrate Prepared From Sweet Whey

Whey is a by-product from cheese processing.Whey may cause serious pollution when discarded to the environment,primarily because of its large quantity and high organic load.Whey utilization has become an urgent problem to be solved.Whey contains more than half of the solids of the whole milk,including whey protein,lactose,water-soluble vitamins and minerals.In addition to high nutritional value,whey protein also has a high solubility,good water holding capacity,excellent emulsifying properties.Whey protein products have been widely used for food formulations.Up to now,large-scale dairy plants have the ability to utilize whey and to make whey protein products,such as whey protein concentrate(WPC)and whey protein isolate(WPI).For small and medium-sized dairy plants,whey was discharged due to limited production capacity.For some reasons,whey is still discharged as waste,which not only causes nutrient loss,but increases the burden on the environment.Therefore,it is necessary to solve the problem of whey discharge and reuse it in small and medium-sized dairy plants.Liquid whey protein concentrate(LWP)is produced by ultrafiltration/percolation(UF/DF)membrane technology.Then it was modified and added directly into dairy products to achieve higher economic benefits.In order to verify and evaluate the feasibility of recycling methods.Cheese whey was obtained during the Cheddar cheese making by flocculation,microfiltration,ultrafiltration.Optimizing the process parameters obtained liquid whey protein concentrate.The liquid whey protein concentrate was polymerized by heat treatment.Polymerized liquid whey protein concentrate(PLWP)was then used as a thickener and a fat replacer in yogurt formulation.This dissertation includes the following aspects:(1)Study on the preparation technology of liquid whey protein concentrate;(2)Effects of heat treatment on the functional properties of liquid whey protein concentrate;(3)Influence of thermal polymerization on viscosity of liquid whey protein concentrate and its application as thickener in yogurt;(4)Effect of thermal treatment on particle size of liquid whey protein concentrate and its application as a fat replacer in yogurt making.The details as following:(1)Whey(pH5.2-5.6)was collected from Cheddar cheese making.It was used as a raw material to prepare liquid whey protein(LWP).The sweet whey was subjected to microfiltration,ultrafiltration/percolation and electrodialysis.The LWP protein was concentrated and lactose was removed.The effects of CaCl2 concentration,pH value,heating temperature and holding time on whey protein and turbidity were investigated after centrifugation.Comprehensive factors finally was determined as follows:whey adjustment pH 6.2,addition of 0.12%CaCl2,heating at 50?for 10 min.The fat content in cheese whey was removed 76%.The turbidity(A500nm)was decreased to0.07.The protein content of whey reached was 8.1g/L.Microfiltration process parameters:with the increasing of transmembrane pressure(TMP),microfiltration(MF/F)whey filtrate flux increased,membrane flux leveled off when pressure is 0.8MPa,whey pH of 6 under the condition of MF/F protein entrapment rate is highest,0.2?m inorganic ceramic microfiltration membrane in the membrane flux,protein and lactose removal rate of these three indicators are higher than other two membranes.Therefore,0.2?m inorganic ceramic microfiltration membrane was better.Ultrafiltration process:the membrane flux reached the maximum value of144.38L/m~2.h with a cycle temperature of 35?and a TMP of 0.6MPa.The protein content and lactose removal rate were 43.6%and 44.7%,respectively.The filtration times were 3 times and the volume ratio was 3:1.The loss of lactose in one-step UF was 37%,but was reduced to 14%by filtration,and the recovery was between 80%and 90%after three osmosis.Filtration on the ultrafiltration membrane effectively increased the rate of lactose removal.The demineralization rate of concentrated whey protein solution by electrodialysis was more than 85%.(2)Liquid whey protein concentrate was obtained,and the polymerized liquid whey protein(PLWP)was prepared by heating.Effects of heating temperature,time and pH on turbidity,solubility,potential,free sulfhydryl group,surface hydrophobicity,emulsifying properties and polymerization degree of PLWP were studied.It was found that polymerized liquid whey protein was formed after heating treatment.Heat treatment has significant impact on the physicochemical and functional properties of liquid whey protein concentrate.Compared with untreated whey protein,the surface hydrophobicity,Zeta potential,free sulfhydryl group on the surface,turbidity and emulsifying properties of the polymerized liquid concentrated whey protein increased significantly.The SDS-PAGE photograph confirms the formation of polymers by heating.The polymerization degree of whey protein was analyzed by High Performance Liquid Chromatography.With the increase of temperature and heating time,the polymerization degree of liquid whey protein increased up to 86%.Therefore,the polymerized liquid whey protein with certain functional characteristics can be prepared by controlling heating conditions,which will be useful for the subsequent application of PLWP.(3)The aim of this chapter was to investigate suitability of polymerized whey protein prepared directly from cheese whey for yogurt formulation.YWPS had significant differences in viscosity,texture,and syneresis compared with the control yogurt.Scanning Electron Micrographs of YWPS displayed a compact and homogeneous protein network for polymerized whey protein solution(PWPS)samples.The 4 yogurt samples were evaluated by the quantitative descriptive analysis method,and 14 sensory attributes were analyzed by principal component analysis.All3 principal components had significant effects on the sensory profiles,accounting for52.3,24.32,and 10.8%of the variability in the results,respectively.Polymerized whey protein prepared directly from cheese whey may be a good protein-based thickening agent for yogurt making.(4)The aim of this chapter was to investigate the effects of polymerized whey protein(PWP)prepared directly from cheese whey on physiochemical,texture,microstructure and sensory properties of low-fat set yogurt.The Cheddar cheese whey was subjected to a sequential processes,including pasteurization,pre-filtration,microfiltration,ultrafiltration,and electrodialysis,to obtain a concentrated whey solution with?10.0%of protein content and 90%of salt removed.The majority(?72%)of particle size distribution of PWP(70°C for 10min,pH 7.0)prepared directly from whey was in the range of 1–3?m.The PWP(1.4%protein,w/w)was added to skim milk as fat replacer.The texture,apparent viscosity,and sensory properties of the yogurt samples were analyzed in comparison with full-fat(3.0%fat,w/w),low-fat(1.0%fat,w/w)and non-fat(0%fat,w/w)yogurts.The non-fat yogurt incorporated with PWP(1.4%protein,w/w)had comparable sensory and textural characteristics to the low-fat(1.0%fat,w/w)yogurt.PWP prepared directly from whey through membrane separation technology can be used as a fat replacer to develop low-fat yogurt with desired characteristics.PWP might be used as a natural and economical ingredient for formulation of low fat fermented dairy foods.