Whey Research Sponsored by CDRF

Whey 2000

97 FLR-01
Scaling-Up and Feasibility Study of a Novel Adsorption Process to Separate and Purify Proteins from Whey

Rafael Jiménez Flores, Cal Poly
San Luis Obispo

Executive Summary

Beta-lactoglobulin is a pure, natural food stabilizer with impressive gelatin and water-binding properties that are useful in frozen dairy desserts and many other foods that require stabilization. Therefore, the isolation of b-lactoglobulin from whey has the potential to become an important aspect of the dairy processing industry.

During this period, we continued to generate technical information regarding reducing residual lipids from whey and subsequent purification of b-lactoglobulin. We concluded that this process is feasible at an industrial scale if the ultimate goal is to recover a fraction of the non-denatured b-lactoglobulin from whey. This absorption process is highly dependent on the fat levels of the starting whey. Lipid content in whey of above 0.08 percent has a detrimental effect in the column and on the recovery of b-lactoglobulin.

Most important, during this period, a step was taken for transferring the technology to industry. This technology will be tested in a commercial setting.

97 GEB-01
Controlling the Pro-oxidant and Antioxidant Properties of Lactoferrin in Foods

J. Bruce German, UC Davis

Executive Summary

Lactoferrin is a whey by-product from the cheese industry with great potential as a value-added component for foods. The ability of lactoferrin to bind iron improves the oxidative stability of infant formula, a food product fortified with iron. Lactoferrin was added to this formula at several concentrations, ranging from its content in human milk (1mg/mL) to the amount required to bind all the iron in the formula (11mg/mL). Lactoferrin decreased oxidation in a concentration-dependent manner. A small amount of lactoferrin (1mg/mL) inhibited the formation of hydroperoxides by 48 percent. At the highest level tested (lactoferrin:iron ratio 1:2), lactoferrin completely inhibited both the formation of hydroperoxides and hexanal during the testing period.

Lactoferrin forms active anti-microbial peptides on hydrolysis, but it is not known if the hydrolysis products retain their antioxidant properties. Lactoferrin was hydrolysed for various lengths of time, and the ability to inhibit lipid oxidation and decomposition declined with hydrolysis. Therefore, intact lactoferrin is a more effective antioxidant than its hydrolysed peptides.

During 2000, oxidation in infant formulas was measured by several methods to estimate the degree of oxidation. A lipid extraction method was developed to recover the fat from the formula and analyze it for hydroperoxides. The volatile compounds produced by decomposition of the hydroperoxides and responsible for rancidity were analyzed by headspace gas-chromatography. Finally, the changes in protein due their interaction with oxidized lipids were measured by fluorescence.

Bovine lactoferrin proved to be an effective antioxidant in infant formula fortified with iron. Addition of lactoferrin at levels as low as 1:18 lactoferrin:iron ratio reduced by half the pro-oxidant effect of iron. Lactoferrin can be an excellent iron carrier and improves the oxidative stability of foods fortified with iron for nutritional purposes. Lactoferrin is expected therefore to have applications in other iron-supplemented foods, such as flour and cereals.

98 KRJ-01
Whey Protein Coating for Improving Packaging Material Performance

John M. Krochta, UC Davis

Executive Summary

The overall objective of this project is the large-volume utilization of whey protein as a packaging material. To accomplish this, the following sub-objectives have been defined:

1. Develop whey protein coating on paper and paperboard to improve paper material moisture-barrier, grease-barrier, printability, strength, color and/or gloss.
2. Develop whey protein-coated paper as an oxygen barrier to retard lipid oxidation of packaged food products.
3. Develop whey protein coating on plastic film to replace plastic oxygen-barrier layers in laminated composite films.
4. WPI- and WPC80-coated paperboard

The grease-barrier property of whey protein isolate (WPI)-coated paperboard has been determined using a standard test method that quantifies grease penetration. WPI-coated paperboard imparts excellent grease resistance and is comparable to current commercial paperboard grease coatings. Cracking of the WPI coatings over long storage times suggests the replacement of the present glycerol plasticizer with one that does not migrate into the paperboard. WPC80 is now being explored as a less-expensive alternative to WPI for coating paperboard. Initial results show it has good potential for providing excellent grease resistance. Furthermore, the lactose present in WPC80 has potential for reducing the amount of additional plasticizer needed to give flexible coatings. Finally, alternative plasticizers to glycerol are being explored to eliminate the plasticizer migration problem that can lead to cracking of coatings.

The oxygen-barrier property of WPI-coated paperboard was determined using an Oxtran instrument that measures oxygen permeability. WPI-coated paperboard imparts excellent oxygen barrier properties relative to uncoated paperboard and commercial coatings. The oxygen-barrier properties of the WPC-coated paperboards will also be determined.

WPI- and WPC-coated paperboard improves gloss, a desirable attribute for packaging purposes. By forming a continuous coating layer, the whey protein coating creates a smooth surface over the rough paper fibers and imparts a significantly glossier surface than non-coated paperboard. Storage tests have shown that whey protein coating maintains its gloss over time.

No noticeable color changes occurred with the WPI-coating over time. WPC coatings appear to give a slight increase in color with time. Additional gloss and color determinations must be made with WPC80-coated paperboard.

WPI- and WPC80-coated plastic

WPI and WPC80 form flexible, transparent coatings on plastic films, including polyvinyl chloride (PVC), low density polyethylene (LDPE) and polypropylene (PP). To obtain good adhesion of whey protein coatings to LDPE and PP, these films must first be treated with corona discharge to modify the film surfaces and improve interaction with the water-based whey protein coating. Measurements of WPI-coated plastic-film color, gloss and oxygen barrier properties are underway. Initial results indicate good gloss, low color and excellent oxygen barrier. WPI coatings have potential for replacing commercial synthetic coatings on plastic films.

Our studies have shown that WPI-based coating on paperboard imparts excellent grease resistance. Gloss studies have shown that WPI increases gloss of uncoated paperboard and color studies have shown that transparency is maintained. Examples of commercial applications include donut boxes and pizza boxes, which require a significant level of grease barrier on their packaging to retard grease penetration and unsightly stains. Examples of applications that will benefit from a good oxygen barrier in addition to grease barrier are pet-food and coffee bean containers. These are just a few examples of the range of applications whey protein coating on paperboard can have. This research on whey protein coating on paperboard is very timely because of the recent withdrawal of 3M’s flourocarbon coating—the industry’s most widely used grease barrier. Presently, manufacturers are seeking alternative coatings. Commercial implementation of whey protein for coating paper and paperboard can result in large-volume utilization of whey. Our research is now focusing on using WPC80 for the coatings to reduce cost and compete more favorably with competitive coating systems.

Our studies have also shown that whey protein coatings can be formed on typical plastic films such as PVC, LDPE and PP. The whey protein coatings are flexible and transparent and have good gloss. Initial results indicate that the coated plastic films have much-improved oxygen-barrier properties. Thus, whey protein has potential for replacing present commercial synthetic coatings. Our research will continue to gather data on properties of whey protein coated plastics, including use of WPC80 to reduce cost.

Whey protein-coated paperboard imparts excellent grease resistance, and comparisons with commercially coated papers show that whey protein is comparable in resisting grease penetration when coated on paperboard. Additional studies have shown that whey protein has excellent oxygen barrier properties. Transparency is maintained in the coating and higher gloss is observed. Whey protein exhibits excellent potential as a grease and oxygen barrier. Further studies on plasticizer migration and properties of WPC80-based coatings are necessary before commercial implementation.

Plastic films can be coated with whey protein formulations that have good adhesion, flexibility, transparency and gloss. Initial results indicate that the coatings improve the oxygen-barrier properties of the plastic films in a manner similar to present synthetic coatings. Further studies will focus on use of WPC80 coatings, plasticizer type and amount, and resulting film gloss, color and oxygen-barrier properties.

99 KRJ-01
Whey Protein Coating Formulations and Application Methods for Dry Foods

John M. Krochta, UC Davis

Executive Summary

The objectives of this project are to:

1. Develop whey protein coating formulations to improve coating application efficiency, adhesion, durability and effectiveness on peanut and chocolate surfaces.
2. Determine coating process conditions (coating application rate, temperature, humidity and air velocity) to achieve desired whey protein coatings on peanuts and chocolate.
3. Measure by instrumental and sensory methods the quality and shelf-life improvements for peanuts and chocolate with whey protein coatings formed in a pilot-scale coating process.
4. Coating Formulations

A number of whey protein-based coating formulations were developed that provide good coating efficiency, adhesion and durability on peanut surfaces. Critical to coating effectiveness is the addition of a food-grade surfactant that provides for good peanut-surface coverage by the WPI coating formulations. The excellent oxygen-barrier properties of WPI films were used to protect peanuts from oxidative rancidity. The WPI coating formulations developed differ by use of native vs. heat-denatured WPI and the addition of vitamin E to enhance peanut protection from oxygen.

Several whey protein-based coating formulations have also been developed that provide good coating efficiency, adhesion and durability on chocolate surfaces. The intended goal is to replace shellac coatings in providing good gloss and reducing surface stickiness. The addition of food-grade plasticizer is necessary to prevent cracking of the formed coating. The type of plasticizer to incorporate in the whey protein isolate (WPI) coating is critical to obtaining good coating gloss that endures with long storage time.

Coating Process Conditions

A commercial coater that is generally used to coat pharmaceuticals and nutritional supplements has been used successfully with our whey protein-based formulations to coat peanuts. The processing conditions employed provided good coatings that were evenly distributed on the peanut surface.

A different coater has been used to assess whey protein-based formulations for coating efficiency and properties on chocolate-covered almonds. This coater is a type generally used in the confectionery industry. The processing conditions employed with this coater have produced good whey protein-based coatings on the chocolate-covered almonds.

Quality and Shelf-life Improvements

Both instrumental and sensory procedures were developed for assessing the effect of whey protein coatings on peanuts. Peanut samples stored for different times and temperatures were analyzed using these methods. Both instrumental and sensory methods clearly indicate that the whey protein coatings dramatically reduce peanut oxidation.

Both instrumental and sensory procedures were developed for assessing the effect of whey protein coatings on chocolate-covered almonds. These procedures clearly indicate that the whey protein coatings produce gloss comparable to the presently used shellac coatings. We are working with the confectionery industry on commercialization of whey protein coatings for peanuts and chocolate.

Oxidation of nuts in confectionery products is usually the limiting factor for product development, quality and shelf life. Demonstration of effectiveness of water-based whey protein coatings in retarding nut oxidation has captured the attention of the confectionery industry and has great potential for creating new markets for whey protein.

Similarly, demonstration that water-based whey protein coatings can compete with ethanol-based shellac in providing acceptable gloss of chocolate products also has high potential for creating new whey protein markets. This is especially the case, since the EPA is pressuring the confectionery industry to eliminate the ethanol vapor emissions that result from shellac coating operations. Since whey protein coatings are water-based, no such ethanol emissions would occur.

We have demonstrated that whey protein can be combined with appropriate food-grade plasticizers and surfactants into formulations that can be used to efficiently coat peanuts using commercial coating equipment. The resulting coatings have good adhesion and durability on the peanut surfaces. Both instrumental and sensory analyses of coated peanuts indicate large reductions in peanut oxidation. These results indicate that this application for utilization of whey protein is worthy of additional development toward commercialization. Additional research should focus on improving coating coverage, adhesion and durability, as well as clarifying the affect of other components of the whey protein coating formulations.

We have also demonstrated that whey protein can be combined with appropriate food-grade plasticizers and lipid materials into formulations that can be used to efficiently coat chocolate products using commercial coating equipment. Several formulations and coating conditions have been assessed. Both instrumental and sensory analyses of coated chocolate indicate gloss values of the various whey protein coatings investigated are comparable to presently-used shellac coatings. With the pressure being exerted on the confectionery industry by the EPA to reduce ethanol-vapor emissions from shellac-coating formulations, this application for utilization of whey protein is worthy of additional development toward commercialization.

00 KRJ-01
Milk Protein Film and Coating Application Lab

John M. Krochta, UC Davis

Executive Summary

The overall objective of this project is the large-volume utilization of whey protein as a food coating or packaging material. To accomplish this, the project goals are to

1. Develop whey protein-lipid composite film systems that can be applied as moisture-barrier coatings to foods using pilot-scale coating equipment.
2. Determine the diffusion characteristics and effectiveness of anti-microbial compounds in whey protein films and in cheese.
3. Determine the effect of moisture content and plasticizers on whey protein thermal transitions and use this data to form films.
4. Whey protein-lipid composite moisture-
5. barrier films

Several approaches to formation of WPI-lipid bilayer moisture-barrier films are being investigated. Techniques for forming a two-step bilayer on WPI films using molten beeswax and an ethanolic dispersion of beeswax were successfully developed. The formation of a second layer with an aqueous emulsion was investigated. This method did not produce consistent high-quality films. An experiment to compare the water vapor permeabilities of the different bilayer films is underway.

Antimicrobial-containing whey protein coating for cheese

A brush-coating method to apply preservative-containing whey protein coatings to Cheddar cheese was developed, and further coating trials are underway. Adhesion, durability and appearance of such coatings on cheese are being evaluated over time at temperatures and humidity levels equivalent to that of cheese ripening and storage. An analytical test for mold growth on Cheddar cheese and coated Cheddar cheese is also being optimized. This test incorporates the coating, preservative, cheese and spoilage mold. The test is being conducted at temperatures and humidity levels equivalent to that of cheese ripening and storage. Diffusion coefficients of potassium sorbate in WPI films have been examined in several different film formulations. By adjusting the film composition, the diffusion properties of preservatives in the films can be optimized to give the most effective antimicrobial coating formulations. The diffusion of preservatives in cheese will be investigated. Using the diffusion data in cheese and in film coatings, a mathematical model can be developed to predict the shelf-life of coated cheese.

Formation and properties of whey protein films

The thermal properties of b-lactoglobulin films plasticized with different plasticizers were determined with a Differential Scanning Calorimeter over a range of plasticizer concentrations. Such information will allow formation of whey protein films by extrusion. The results show that the type and amount of plasticizer have different affects on the film thermal properties.

Solubility or insolubility in water is an important property of edible films. Potential applications may require water insolubility to enhance food-product integrity and water resistance. However, in some cases film water solubility before consumption of the product might be beneficial. The degree of protein denaturation and unfolding as protein heating time and temperature are increased, affects the degree and nature of protein-protein cross-linking and, as a consequence, the solubility and mechanical properties of the films. Our results show that whey protein isolate (WPI) film solubility decreases as film-formation solution heating temperature and time are increased. Parallel to the decrease in film solubility, films became stiffer, stronger and more stretchable as heat-denaturation time and temperature are increased. Oxygen permeability is lower for heat-denatured WPI films than for native WPI films. These results indicate that an increase in covalent cross-linking as heat-denaturation of the whey protein increases is important to forming water-insoluble film with higher tensile properties and lower oxygen permeability.

Because of their lower non-protein content, WPI films can achieve higher strength, stiffness and stretchiness than WPC films. WPC films with flexibility similar to WPI films had oxygen-barrier properties that improved as lactose content increased. However, the WPC 65 and WPC 35 films tended to exhibit lactose crystallization, which is detrimental to film integrity. WPC 80 films had good stability and oxygen permeability similar to WPI films. Rate and extent of film yellowing significantly increased as lactose content in the films increased. Such yellowing may be an advantage for some food products.

The applications targeted in this research reflect food industry needs for improvement in food product quality and shelf life. Thus, achievement of our objectives will result in substantial utilization of whey protein for edible films and coatings.

Several novel approaches to forming whey protein-lipid bilayer films have been identified. Such bilayer films have potential for possessing the good mechanical properties of whey protein films and the good moisture-barrier properties of the lipid. Testing of the bilayer films for mechanical and moisture-barrier properties will begin soon. Durable moisture-barrier edible coatings is one of the food industry’s greatest needs.

Methods for coating cheese with preservative-containing whey protein films, measuring diffusion of the preservative in the film and cheese, and measuring rate of mold growth have been identified. These methods will now allow assessment of ability of preservatives entrapped in whey protein film coatings to inhibit mold growth on cheese. Preliminary results have shown WPI films to be feasible carriers of preservatives and to be used as coatings for cheese. This concept also has great potential for other high-moisture and intermediate-moisture foods.

Whey protein films require addition of plasticizers to avoid brittleness and maintain flexibility. Such plasticizers also affect the film’s thermal properties. Several different plasticizers studied produced different transition temperatures with b-lactoglobulin films. Collection of such thermal transition data is the first step toward developing an extrusion process for producing whey protein-based edible films for use as food wraps and pouches.

Understanding the structure and interactions between protein molecules in film formation are essential in order to form films with the desired solubility, mechanical and barrier properties. An increase in covalent cross-linking as heat-denaturation of the whey protein increases is important to forming water-insoluble film, with higher tensile properties and lower oxygen permeability. The results clearly indicate the importance of controlling heat denaturation time and temperature in order to achieve the desired film properties.

WPI films are generally stronger and more stretchable than WPC films. However, WPC 80 films have reasonably good mechanical properties. WPI and WPC films with comparable flexibility also have comparable oxygen-barrier properties. Thus, WPC 80 films have potential for certain food applications.