Polymerized Whey Protein Based Microencapsulation Technology And Its Applications In Functional Foods

Whey protein is the by-product generated from cheese manufacture.It is known by its high nutrition value and its desirable functional properties.Whey utilization may help to protect environment.Whey protein is also a good resource of protein for food and pharmaceutical industries.The film and hydrogel property are important functional characteristics of whey protein.When heating happened,disulfide bonding between ?-lactoglobulin promotes the formation of network of whey protein.Whey protein polymerization can also be improved by noncovalent bonding such as calcium bridges.The main objectives of this study were to investigate the film and hydrogel properties of whey protein and their use on microencapsulation.And then prepare microencapsulated bioactive materials by polymerized whey protein,and make them use in symbiotic fermented milk.Firstly,experiments were carried out to prepare and characterize the heat-reduced polymerized whey protein.Whey protein was polymerized under different conditions,different concentration(8-16%),p H(7.0-8.0),heating temperature(70-90 oC)and heating time(5-30 min).Size distribution,surface potential,rheological properties,secondary structure,free sulfhydryl groups,viscosity and denaturation degree was measured to characterize the polymerized whey protein.The results showed that heating process induced the changes in various properties of whey protein compared with native one.Changes include the decrease and increase of particle size,free sulfhydryl groups and surface hydrophobicity,secondary structure,viscosity,degree of denaturation,etc.These changes characterized the denaturation and polymerization of whey protein.Secondly,polymerized whey protein and Ca2+-induced hydrogel were made under different conditions.Such as different concentrations(11-15%),heating temperatures(70-80 oC)and heating times(5-15 min).Texture,degradation and hydrolysis in simulated digestive juice were observed.Results indicated that the addition of Ca2+ might enhance the gel strength of the polymerized whey protein.The gel strength increased with the polymerization of the whey protein within limits.The cross-linking by Ca2+ generated a network of the polymerized whey protein,and it may encapsulate the core materials effectively.Ca2+-induced gel showed lower dissolvability(~30%)and the degree of hydrolysis in simulated gastric juice,and higher in simulated intestine juice conversely(~100%).Finally,polymerized whey protein was used to microencapsulate bioactive compounds.And then made them use in symbiotic yoghurt as nutritional supplements,separately.The results were described as follows:(1)Ginsenosides is a group of the bioactive compounds in ginseng.Its application in functional dairy foods is limited due to the bitter taste and yellowish color of ginsenosides.Using polymerized whey protein as the wall material to capsulate ginsenosides may effectively mask its bitter taste and improve the color.Ginsenosides was microencapsulated using heating-induced polymerized whey protein as the wall material.The entrapment yield was 97.15 ± 1.95% and release rates were about 20% and 100% in gastric and intestine juices,respectively.Microencapsulated ginsenosides were used for fermented milk formulation.Results indicated that samples with microencapsulated ginsenosides had much higher acceptability score(3.7)compared with those with ginsenoside extract(1.6)(P < 0.01).Addition of microencapsulated ginsenosides significantly decreased the syneresis and increases the content of protein of the sample(P < 0.01).(2)Probiotics are widely used in functional fermented foods.L.acidophilus has a low survivability in stomach.Polymerized whey protein based microencapsulation of probiotics can improve their survivability during digestion.LA-5 was microencapsulated using heating-induced polymerized whey protein as the wall material.The result showed that entrapment rate of the microencapsulated LA-5 was 92.90±3.90%.Microencapsulated LA-5(5%,w/v)were used for fermented cow / goat milk products.Results showed that the microcapsules of L.acidophilus were intact after 10-week storage in yoghurt.And L.acidophilus were released in the small intestine juice,the survival number was above 105cfu/m L.The results showed that eating yoghurt with the microcapsules can make sure the number of probiotics in colon.(3)L.acidophilus was microecapsulated by polymerized whey protein using freeze-dryer.Results indicated that there were no significant differences between the polymerized whey protein and maltodextrin on hygroscopicity and the protective ability.The microencapsulated LA-5 was used for cow / goat milk yoghurt formulation.Results showed that there were no significant differences among the samples on fermentation ability.Polymerized whey protein based LA-5 improved the content of protein and decrease the synthesis of the yoghurt samples.Meanwhile the structure of the goat milk yoghurt was also improved.In summary,this study systematically investigated and characterized the physiochemical properties of polymerized whey protein,and its application in microencapsulation.Microencapsulated ginsensides and LA-5 were made by polymerized whey protein as wall material,and then made then use on fermented milk products.The results can be proved that using polymerized whey protein as wall material for microencapsulation of bioactive compounds and probiotics are feasible.