Manufacturing - Milk Powder - 2001
Development and Use of a Quantifiable Descriptive Language for Characterization of Milk Powders and Concentrates - MaryAnne Drake, North Carolina State University
Buttermilk Fractionation - Rafael Jiménez-Flores, Cal Poly San Luis Obispo
Genetic Polymorphism of Milk Proteins: Effect of Process Heating on Milk Powder Properties - Rafael Jiménez-Flores, Cal Poly San Luis Obispo
Technical Information Handouts for SMP - Phillip S. Tong, Cal Poly San Luis Obispo
Dairy Ingredients Applications Program 2001 - Phillip S. Tong, Cal Poly San Luis Obispo
Stabilization of Milk Proteins in a Heated Acid Beverage Environment - Phillip S. Tong, Cal Poly San Luis Obispo
Freeze-Thaw Stability of Dairy-Based Gels - Phillip S. Tong, Cal Poly San Luis Obispo
Reconstitution Options for Skim Milk Powder - Phillip S. Tong, Cal Poly San Luis Obispo
Detection of Spores in Dairy Products by a Conjugated Monoclonal Antibody Assay - Rafael Jiménez-Flores, Cal Poly San Luis Obispo
Microbial Quality of Milk Powder - Rafael Jiménez-Flores, Cal Poly San Luis Obispo
Milk Powder Stability: Bag Durability and Changes During Storage at Elevated Temperatures - Nana Y. Farkye, Cal Poly San Luis Obispo
Evaluation of Functional Properties of Calcium-Enriched Milk Powder Used as Dairy-Based Ingredients for the Food Industry - Phillip S. Tong, Cal Poly San Luis Obispo
Lactose-Free Dairy Ingredients - Phillip S. Tong, Cal Poly San Luis Obispo
Prototypes Using Dairy Ingredients - Phillip S. Tong, Cal Poly San Luis Obispo
Comparison of MPC, SMP and WPC in Baked Products - Phillip S. Tong, Cal Poly San Luis Obispo
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
Packaging Material Performance - John M. Krochta, UC Davis
Evaluation of Cream Composition, Handling, and Processing Factors That can Influence Churning Efficiency and Butter Quality - Phillip S. Tong, Cal Poly San Luis Obispo
Properties of Milk Protein Concentrate for Cheesemaking - Nana Y. Farkye, Cal Poly San Luis Obispo
Development and Use of a Quantifiable Descriptive Language for Characterization of Milk Powders and Concentrates
MaryAnne Drake, North Carolina State University
The objective of this project is to develop a descriptive quantifiable sensory language composed of desirable and undesirable flavors with precise references for whole and nonfat milk powders and concentrates. The initial sensory language has been identified and refined. Work has been conducted with nonfat dry milk (NDM) that indicates that the language is representative of the flavors encountered in these products. Whole milk powders (WMP) are currently being evaluated to determine the completeness of the language for this product. To clarify more precise references for the sensory language, additional work is being conducted on the chemical components of milk powder flavor volatiles that have been extracted from NDM most similar to fluid skim. Study results indicate that certain chemical volatiles are consistent across heat treatment of NDM (milky flavors) while others changed with heat treatment (heat-induced flavors). Current work is focused on analogous work with extreme off-flavored NDM.
Production of milk powder continues to increase in the United States. To remain competitive in the global market, to maximize existing markets and to identify new markets and ingredient applications, powder quality must be outstanding and consistent. Flavor quality is an important parameter for milk powders because flavor influences consumer acceptability and can influence finished product quality when powders are used in ingredient applications. The development of a precise quantitative sensory language to describe and quantify all the flavors in milk powders will aid in research and marketing communication. The language can be used in marketing to more accurately supply the preferences of consumers and to monitor product consistency. In research applications, the language can be a powerful tool to determine the effects of processing and storage regimes on sensory perception of flavor. The language also can be used with chemical flavor analysis to identify the chemical compounds responsible for specific flavors. Linking powder end-product quality with the technology of powder production and storage will enable powder producers in California and throughout the United States to maximize powder sensory quality, and will provide a descriptive sensory language to identify and quantify flavors in milk powders.
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Buttermilk Fractionation
Rafael Jiménez-Flores, Cal Poly San Luis Obispo
The objectives for this project are to:
1. Isolate milk fat globule membrane material from buttermilk using crossflow microfiltration.
2. Analyze the retentate and permeate using standard chemical analyses as well as atomic force microscopy.
3. Fractionate buttermilk skim proteins from the permeate using crossflow microfiltration and affinity purification.
4. Isolate phospholipids and sphingolipids from milk fat globule membrane-rich fraction from crossflow microfiltration.
5. Analyze the process and perform an economic study.
This project has yielded significant understanding on the primary procedure to obtain major lipid-enriched fractions from commercial buttermilk, as well as fresh buttermilk produced at the Dairy Products Technology Center pilot plant. Several fractions have been produced and analyzed for protein, glyco-protein and lipid content. Each is distinguished by the extent of processing by cross-flow microfiltration concentration.
Particularly relevant to this work was the production and distribution of a buttermilk fraction enriched in milk fat globule membrane material (5-10 g)—in particular sphingomyelin—and sent to be tested by Bruce German at UC Davis. Results from this analysis precipitated the production of larger scale quantities (4kg) of this fraction to be sent to the Nestle Research Center in Switzerland. In addition, practical results from this work include the increase in commercial as well as research activities regarding buttermilk. The National Dairy Council and the California Agricultural Research Initiative have funded additional projects with expanded objectives to this initial work. Results from this work have opened the opportunity for researchers to obtain buttermilk fractions with potential biological activities. We are positioned at this point as suppliers for these ventures.
Due to the opportunities generated from this work, much time was devoted to the construction, validation and optimization of a larger microfiltration system. Operation parameters, pumps and modes of operation had to be optimized to obtain desired results in a time frame appropriate for preventing microbial contamination. The system is now operational.
Researchers at Cal Poly and UC Davis continue to work diligently to optimize the scientific endeavors and maximize the return on investment on research. Renewing valuable collaborations between these two institutions is a valuable asset for California.
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Genetic Polymorphism of Milk Proteins: Effect of Process Heating on Milk Powder Properties
Rafael Jiménez-Flores, Cal Poly San Luis Obispo
The objectives for this project are to:
1. Initiate collaborative research to elucidate the role of b-Lactoglobulin (b-LG) and k-Casein (k-CN) in the functional properties of dairy products after heating.
2. Focus on the identification of peptides resulting from the specific reaction of milk proteins heated in a model system.
3. Use the data from the peptides produced to elucidate their reactivity.
This project was developed along with the New Zealand Dairy Research Institute (NZDRI) as an initial point in a collaborative study of the importance of heat interactions among the most reactive milk proteins under heat—b-Lactoglobulin and k-Casein. It has long been recognized that the extent of the interaction of these two proteins dictates to a large extent the derivative functional properties of the processed foods containing these proteins. The NZDRI has long recognized this fact and has on its staff an active group of researchers studying this problem. Data on the genetic variants of milk proteins and their reactivity is lacking in detail, and due to the expertise and interest at DPTC of functionality of milk powders, common ground was found to develop a joint project.
Focusing on the interaction among k-casein A (it was selected from homozigous milk k-casein AA) and b-Lactoglobulin, Lawrie Creamer and Mike Boland helped in the development of this project. To better understand the effects of processing on the functionality of milk powder, we characterized at the molecular level the protein-protein interactions after heating and drying. The powder sample was produced in the pilot plant of the Cal Poly DPTC in San Luis Obispo, Calif. A simplified milk system was created by mixing affinity-purified b-LG (b-LG genetic variant AB) to casein micelles obtained by filtration of raw milk (k-CN variant AA; b-LG variant BB) through a 0.1mm pore size ceramic membrane. The mixture was heated to 90oC for 15 minutes and spray dried. The high molecular weight molecules were segregated by size exclusion chromatography, identified by SDS-PAGE, and hydrolyzed by trypsin. The native and disulfide-bond-reduced hydrolysates were analyzed by HPLC-MS at the NZDRI Palmerston North facility in New Zealand.
Our SDS-PAGE analysis shows that we isolated a disulfide-linked protein polymer that contained predominantly k-CN and b-LG. By comparing our mass spectroscopy results to tryptic digest data banks; we identified 42 peptide fragments, including 11 disulfide-linked peptides. We identified three different types of disulfide links: (1) the expected intermolecular bridges between two k-CN molecules connected k-CN Cys11 to k-CN Cys11 and k-CN Cys88 to k-CN Cys11, (2) the heat-induced association of two b-LG linked b-LG AA Cys66 to b-LG BB Cys106/119/121 and b-LG Cys160 to b-LG BB Cys106/119/121, and (3) the heat-induced covalent bonding between b-LG and k-CN involving k-CN Cys88 to b-LG Cys66, k-CN Cys11 to b-LG Cys160, and k-CN Cys11 to b-LG BB Cys106/119/121. These peptides aid in the elucidation of protein interactions in dried milk.
This work results in a better understanding of the basis for several New Zealand patents granted in the United States, and in gaining a better strategy to obtain the same or better results using technology and genetic variants common in this country.
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Technical Information Handouts for SMP
Phillip S. Tong, Cal Poly San Luis Obispo
The objective of this project is to deliver a variety of technical information handouts to assist in providing technical support to product developers using dairy ingredients and to manufacturers of dairy ingredients and products.
The following handouts were developed and distributed as Technical Information Handouts for Skim Milk Powder:
- Bulk density of milk powders
- Particle size of milk powders
- Baking with dry milk ingredients
- Formulating with dry milk ingredients
- Calcium-enriched dairy ingredients
These handouts were provided through direct on-line fax to key skim milk powder manufacturers and end-users of skim milk powder. In addition, paper copies of the handouts are distributed upon request, and electronic copies are posted on the Dairy Products Technology Center Web site.
Technical information handouts provide timely and regular communication of useful information to manufacturers and users of skim milk powder. Such information helps to facilitate the successful use of dairy ingredients in many food applications.
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Dairy Ingredients Applications Program 2001
Phillip S. Tong, Cal Poly San Luis Obispo
The objectives for this project are to:
- Provide technical support to end-users and suppliers of dairy ingredients in the food industry.
- Conduct applied research, which facilitates the application of dairy ingredients in the food industry
Specific tasks include:
1. Providing technology assistance to food product developers as referred from Dairy Management Inc. (DMI) or through direct queries to Dairy Ingredients Applications Program as approved by the principal investigator and DMI.
2. Keeping abreast of research on dairy ingredients and transfering applicable information to the food industry.
3. Producing monthly “Dairy Ingredients Faxes,” and distributing them to the food industry.
4. Visiting key research groups to build relationships and understanding of research activities, and transferring in formation to appropriate industry groups.
5. Participating in food industry trade shows by developing and displaying product prototypes, utilizing dairy ingredients in exhibits organized by DMI, and interacting with attendees at the shows.
6. Providing technical support to complete revision of the dairy ingredients applications guides.
We formulated the following prototypes to be used for promotion of dairy ingredients and/or demonstration at trade shows:
- Mocha cappuccino
- High-protein cookie
- Meal-replacement beverage
- Instant pudding
Industry projects:
- Whole milk powder stabilization in caramel sauce
- Instant pudding utilizing nonfat dry milk
- Aseptic puddings targeted for children utilizing nonfat dry milk as an ingredient
- Pancake formulation
- Anti-caking properties of whole milk powder
- Oxidized fat in stored whole milk powder
- Dry Milk Application Guide: Completed 25 formulations to be used in the Dry Milk Application Guide
Outreach:
- Provided milk powder training program for DMI
- Attended the Tulare Farm Show. Demonstrated mocha cappuccino beverage at DMI booth
- Prepared information and products for DPTC open house
- Presented information and hosted meeting with USDEC and visitors from Asia
- Presented information to beverage manufacturer R&D in Florida
- Provided DMI booth support for SCIFT in Pasadena, Calif.
- Provided information and support to two CA fruit processors
- Attended and worked at the DMI booth at NCIFT in Oakland, Calif.
- Attended and worked at the DMI booth at Annual IFT meeting in New Orleans and demonstrated high-protein cookie and meal replacement beverage
- Provided information and hosted meeting with USDEC and visitors from Southeast Asia
- Provided information and organized the Whey Processing workshop in Visalia, Calif.
- Provided information and hosted meeting with USDEC and visitors from Latin America
- Presented information and hosted visitors from the Yangling Agri-Hi-Tech Zone
- Provided information and visited cookie manufacturer
- Provided information and visited frozen food manufacturer
- Hosted Tony Patterson (Massey University) seminar on glass transition for milk powder stickiness
We have seen an increase in use of the services and technical support capabilities of the Cal Poly Dairy Ingredients Applications Program as more people and organizations learn of its activities.
Based on the queries being received and answered, it appears that a real need is being met by the establishment of this program—both for the ingredient manufacturers and the end users. In some cases, we believe our assistance encouraged successful utilization of domestic sources of dairy ingredients by food manufacturers. In addition, technical support provided to dairy ingredient manufacturers continues to promote product/technology innovation to improve dairy ingredient product lines.
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Stabilization of Milk Proteins in a Heated Acid Beverage Environment
Phillip S. Tong, Cal Poly San Luis Obispo
The objective of this study was to identify conditions and ingredients that will stabilize milk proteins in a heated acid beverage environment. Our specific goals were to:
1. Establish a model system to evaluate dairy protein stability in a heated acid environment.
2. Determine a quantitative assessment method for dairy protein stability.
3. Obtain a series of stabilization options, and evaluate their ability to stabilize the model system.
We evaluated a total of 84 beverages. Of those, we processed 14 formulations with three different pH levels (3.5, 4.0, 4.5) at two different heat levels (750C and 850C). We found pectin to be more effective than Polypolene Glycol Alginate (PGA) and xanthan gum for improving precipitation and solubility over a broader pH and temperature range. Pectin stabilized the dairy-acid beverage at 1.5 percent protein at all three pH levels and two temperature ranges. However, as the milk protein increased and the pH decreased, pectin was not successful at stabilizing the milk proteins. All three hydrocolloids showed enhanced product viscosity, improved suspension of proteins and imparted a good mouth feel on the finished dairy-acid beverage at pH 4.5, 750C and 1.5 percent protein.
The findings of this study have implications for formulations to be used in a dairy-juice beverage. The improved stability of certain beverages in the presence of hydrocolloids does not appear to be a result of viscosity changes alone but by an interaction between the hydrocolloid and the casein. Homogenization of the beverage prior to heating and/or the addition of a phosphate system may produce an improvement in the overall stability of these beverages at varying pH and processing temperatures and may be an area for future study.
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Freeze-Thaw Stability of Dairy-Based Gels
Phillip S. Tong, Cal Poly San Luis Obispo
The objective of this project is to evaluate a series of hydrocolloids and other potential stabilizers for their ability to reduce instability caused by freeze/thaw cycles for a dairy-based gel system containing skim milk powder.
A total of 16 acid dairy-based gel formulas were evaluated. The starch and hydrocolloids were evaluated at two different usage levels and two pH levels. The viscosity of the dairy gel prior to freezing is not changed significantly with the addition of the hydrocolloid. The starch at the increased level showed the highest viscosity. The addition of the hydrocolloid did not appear to affect the pH. All the hydrocolloids tested functioned to improve mouth feel and texture during the freeze/thaw cycle period. Carrageenan did not appear to work as well as the starch and xanthan and guar gum. The texture and the mouth feel of the formulas produced with carrageenan were more rigid and much different than the fresh sample. Also, the xanthan gum at the higher usage level did not function as well compared to the evaluation of this gum at the lower usage level. This may be a result of an excessive percentage of gum in the system. This can cause syneresis, because it destabilizes the system. All samples showed some slight syneresis during some point in the freeze/thaw cycle. However, all hydrocolloids tested helped to reduce syneresis and minimize cracking to some extent. The samples without hydrocolloids experienced the most syneresis, as well as the sample of xanthan gum with the high usage level. An acid dairy gel formulated with xanthan gum (0.20 percent), pH 4.0 showed no cracking. The cracked product was formulated with carrageenan at .20 percent, pH 4.0. When the usage level of carrageenan was increased, the product did not crack. The high-usage xanthan gum formula was the only other formula to show cracking.
The addition of the hydrocolloid appears to help bind water and decrease syneresis, as well as minimize cracking of the frozen/thawed acid dairy gel. The texture and mouth feel of the dairy-based gel, although very subjective, formulated with xanthan gum at a 0.20 usage level, produced a product with the best texture and mouth feel, as well as no cracking and syneresis.
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Reconstitution Options for Skim Milk Powder
Phillip S. Tong, Cal Poly San Luis Obispo
The specific objective of this work was to identify and characterize reconstitution options for skim milk powder. We evaluated three factors (reconstitution temperature, mixing conditions and water quality) on dispersibility and solubility of reconstituted skim milk (9 percent total solids). The results indicate that time of mixing, type of mixing and mixing temperature significantly influence measures of dispersibility and solubility of reconstituted skim milk powder. Under less than ideal mixing conditions (low shear), mixing time became critical.
The results of this work provide quantitative information to answer questions related to the effect of reconstitution conditions for skim milk powder. Such information can be utilized by end-users of skim milk powder to guide them in making decisions about the tradeoffs between various options for reconstitution of skim milk powder and their specific effect on dispersibility and eventual solubility.
To achieve good reconstitution conditions for dry milk powders in water, we recommend minimum water temperatures of 25–500C with high shear agitation or use of a powder horn mixing system. Minimum time for the incorporation of powder should not be less than 15 minutes. However, care should be taken to minimize inclusion of air into the reconstituted milk during reconstitution.
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Detection of Spores in Dairy Products by a Conjugated Monoclonal Antibody Assay
Rafael Jiménez-Flores, Cal Poly San Luis Obispo
The objectives of this project are to:
1. Screen for cross-reactivity with endospores isolated from California milk powder in native and denatured states using the Dairy Products Technology Center Bacillus library.
2. Determine sensitivity of spore cross-reactivity by ELISA method.
3. Identify the characteristics of the epitope of our monoclonal antibody.
4. Evaluate methods for applying detection to milk.
The monoclonal antibody used to detect endospores in milk was quick, specific and proved to be sensitive in concentrations of around 1,000 spores per gram of milk type of spore used, the sensitivity could be 100 spores per gram of solid. This was determined through several experiments evaluating a monoclonal antibody for its use in the detection of endospores and adjusting the testing procedure to optimize binding and detection. All of the preliminary laboratory experiments necessary to design a rapid detection assay that is accurate, efficient and sensitive were completed. The assay’s detection limits are as low as 100 spores per gram of solid with high specificity. Depending on the secondary antibody specificity used in conjunction with the monoclonal, the assay ranges from broad specificity (detecting all five spore strains found in milk powder that are detrimental) to very specific (detecting one strain in particular with high intensity). The antibody’s epitope, or site for interaction and recognition, is still unknown; however evidence suggests a conformational bond. From our work, it is suggested that the epitope is a large glycoprotein with subunits that can be analyzed upon reduction of the protein sample. We evaluated other factors that may hinder the assay, including: secondary cross-reactivity, vegetative cell interactions, different secondary antibodies and enzyme substrates used. Secondary cross-reactivity is problematic only at extremely high spore concentrations (>1.0 x 108 spores/ml). For lower concentrations, only slight interactions exist between the spores and secondary antibody, which may be resolved through spectrophotometric corrections. Through many experiments, we determined that the primary antibody does not react with the vegetative cells. Some experiments did show that the secondary antibodies have slight reactivity. This interaction between vegetative cells and the secondary antibody would not be of concern in detection assays. This is because the primary antibody does not bind the vegetative cells and would be washed away before the secondary antibody was added in the ELISA procedure. We found that different secondary antibodies give different results as to spore specificity; however, this would be most beneficial in customizing assays to specific problematic spores. We found that the enzyme substrate used was important, since some spores contain these substrates. Using alkaline phosphate optimized the reaction. With the experiments carried out, we can assume that a monoclonal antibody would be ideal in the development of a rapid detection assay for spores. The procedure, if scaled to a commercial stage, may have desirable characteristics including speed, sensitivity and specificity, and may prove to be a more efficient and more effective method than current microbiological detection methods.
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Microbial Quality of Milk Powder
Rafael Jiménez-Flores, Cal Poly San Luis Obispo
The objectives of this project are to evaluate:
1. The Nuclisens system as a potential method for the rapid detection of endospores in milk powder.
2. RNA extraction methods for Bacillus species for use in the Nuclisens system.
3. the effectiveness of polymerase chain reaction (PCR) amplification using the GerC3 primers with Bacillus species for future use with the NucliSens system.
4. The efficiency of reagents used in the PCR reaction.
Endospore-forming bacteria are resistant to heat and desiccation associated with a harsh environment, including the pasteurization, evaporation and spray-drying of milk. Producers and processors have seen an increase in the restrictions as well as frequency in which spore counts are included in the specifications of milk powder. Contamination by spores, or more specifically bacterial endospores, can cause foodborne outbreaks along with food spoilage. Under proper conditions, spores have the ability to germinate, grow and initiate proteolysis and lipolysis of protein and fat. Therefore methods are needed for detection and elimination of endospore formers associated with milk and milk products. Current methods are labor-intensive, time-consuming and have poor detection limits. Molecular methods offer a unique and sensitive tool for rapid microbial detection over traditional methods. Results from this project have achieved two distinct objectives. First, this work demonstrated the ability to detect spores in milk powder using a PCR-based technique. This approach is rapid, and has potential for commercial application. One of the limitations, however, is that the method is not quantitative, and further development is needed for its commercialization. The second objective is the development of a technique that would allow us to use nucleic acid-based methods for the understanding of the microbial ecology, and thus be able to make judicious decisions about processes to eliminate spores in the final product. While implementation of this knowledge will depend on the economic value to producers and processors of low-spore milks, there are still instances in which the random appearance of excessively high numbers of spores cannot be easily explained.
Our results show that using PCR and amplifying a specific gene for endospores allow us to detect those endospore-former bacteria associated with milk powder production. This detection is possible by isolating the whole microbial community DNA and then analyzing the product of a specific gene with the primers designed for this work. The primer set is specific for the germination gene GerC3 in B. subtilis, and has been shown to correlate with several other Bacillus species. However, the results obtained have shown that the primers specific for the germination gene in Bacillus species were problematic in their inconsistency. Using those GerC3 primers to amplify the germination gene from B. licheniformis, the most common Bacillus species in milk, we sequenced this product and developed new primers to solve this problem.
In a parallel study, this work also yielded a tool that can be used to study and analyze microbial populations at each step during milk powder production. For this objective, a more common gene is targeted. The 16SRNA gene, normally used for typing bacteria species, can be used for developing Terminal Restriction Fragments (TRFs) for the detection of different species of bacteria. Several studies were completed on the optimization of the technique and testing it for its use in dairy products. The ultimate validation has been made in commercial operations, in which samples were taken at each step of the milk powder process.
The objectives were expanded due to matching funds from the California Agricultural Research Initiative (ARI). Deeper understanding was necessary to explain the relationship between the bacterial populations and the incidence of spore-formers that eventually contaminate the final product with spores. The ARI has supplemented funds to expand our experiments toward better understanding this phenomenon. This is a tangible result from the funding and activities in the microbial improvement of milk powder.
Finally, due to the work developed at Cal Poly’s Dairy Products Technology Center, scientists at the Lawrence Livermore National Laboratory can use the spore collection generated by this work, thus helping in their efforts to prevent bio-terrorism.
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Milk Powder Stability: Bag Durability and Changes During Storage at Elevated Temperatures
Nana Y. Farkye, Cal Poly San Luis Obispo
The objectives of this project are to determine the durability of multiwall paper or plastic milk powder bags, and to identify physical and chemical changes in milk powder packaged in various bags and stored at high temperature and humidity.
Plastic bags have been introduced recently as an alternative to multiwall Kraft paper bags in milk powder packaging, as it is believed that plastic bags are more durable and would better preserve the quality of milk powders during storage than paper bags. However, little scientific information is available on the performance of plastic bags for milk powder storage. The aim of this study was to compare the durability of paper and plastic bags in milk powder packaging, and to determine the effects of package type on the properties of milk powder during storage. Skim milk powder (SMP) packed in plastic or paper bags was obtained from commercial milk powder manufacturers. Both 25 kg plastic and paper bags containing SMP were evaluated by butt drop, side drop and shaker test to determine which bag type is more durable. Sets of bags of plastic and paper containing bags containing SMP were stored at 380C and 90 percent relative humidity. Duplicate bags of each type were removed after 0, 45, 90 and 135 days, and the powder samples were analyzed for moisture, water activity, percent lactic acid, pH, insolubility index, bulk density, flowability, dispersibility and particle size. Minimum damage was inflicted to the outer layer of plastic bags. The printed graphics and text were damaged more extensively in plastic bags; however, overall durability performance of plastic bags was better than paper bags. The magnitude of change in the majority of physical and chemical properties measured in powder samples during storage indicate that plastic bags are similar to paper bags in maintaining quality of SMP at high temperature and relative humidity.
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Evaluation of Functional Properties of Calcium-Enriched Milk Powder Used as Dairy-Based Ingredients for the Food Industry
Phillip S. Tong, Cal Poly San Luis Obispo
The objectives of this project are to:
1. Define the most applicable means to increase the calcium levels in milk powder and/or in protein concentrates, and the appropriate form of calcium compounds that can be used to prepare calcium-rich dry milk.
2. Identify and characterize specific functional attributes of calcium-enriched dry milk in products and ingredient applications (solubility as a function of pH, heat stability, fat emulsification, foam stabilization and viscosity).
The information generated as a result of this work provides basic information on various options for calcium fortification of milk powder. Based on this information, any manufacturer interested in selecting a calcium fortification option can evaluate the pros and cons and/or challenges (changes in functionality and stability) in fortifying non-fat milk powder (NFDM) with the calcium salts that are commercially available. In addition, this information also highlights the effect of calcium fortification on a food system and its potential effect on the skim milk solids that may be present in the formulation. The type and amount of calcium fortification can influence the functional properties (e.g., heat stability, emulsion stability, solubility) of non-fat milk powder.
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Lactose-Free Dairy Ingredients
Phillip S. Tong, Cal Poly San Luis Obispo
The specific objective of this project was to develop and evaluate a process for manufacture of lactose-free, calcium-fortified milk powder. A two-stage process was developed: In the first stage, lactose reduction was achieved by ultrafiltration (UF), and in the second stage, the calcium present in the permeate produced during lactose reduction was precipitated using one of the three different methods and then recovered by refiltering the permeate. These methods involved precipitating the calcium by (1) heat treatment, (2) pH adjustment or (3) a combination of pH adjustment and heat treatment to the permeate. The process was first developed at lab scale and then its applicability was tested at the pilot scale. For this, skim milk was concentrated to 4X level (volume basis) with 10 kDa membranes using a stirred cell at the lab scale and a spiral wound crossflow unit at the pilot scale. The resultant permeate containing lactose and minerals besides water was either heat-treated (63 ºC for 30 min), or pH adjusted (to 8.0) or pH adjusted (to 8.0) and then heat-treated (63 ºC for 30 min). Then the treated permeates were refiltered using the same clean UF membrane.
Skim milk, retentates, permeates and the treated permeates were analyzed for total solids, total ash, calcium and lactose content. Permeates and treated permeates were also analyzed for total nitrogen and permeate for the presence of protein. About 75 percent of the total lactose present in skim milk permeated through the membrane during ultrafiltration. About 50 percent of the expected free calcium in the skim milk also permeated through the membrane. The three treatments applied produced white precipitates and turned the clear permeates into turbid permeates. On refiltering the treated permeates, ~ 42 percent, ~ 50 percent and ~ 70 percent of the total calcium present could be recovered from (1) heat-treated, (2) pH-adjusted and (3) pH-adjusted and heat-treated permeates, respectively. Similar results were obtained for both lab scale and pilot scale experiments. Thus, the maximum calcium recovery was obtained by pH adjustment and heat treatment to the permeate followed by refiltration. No marked change occurred in the lactose content due to any of the three calcium precipitation treatments and subsequent refiltering of the treated permeates.
About 75 percent of the total lactose present in skim milk permeated through the membrane during ultrafiltration. The calcium that permeates through the membrane in this process can be heat precipitated, refiltered and added back to the retentate to recover approximately 70 percent of the original calcium.
This work demonstrates the technical feasibility for producing a new reduced-lactose protein stream with high natural milk calcium content for the food industry. A two-step membrane process results in significant lactose reduction but still maintains the naturally high calcium content of the original feed stream.
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Prototypes Using Dairy Ingredients
Phillip S. Tong, Cal Poly San Luis Obispo
The objectives for this project were to formulate and deliver a variety of application prototypes using dairy ingredients. The prototypes will be promoted for the dairy ingredients, and the fact sheets/formula sheets can be used to provide technical assistance for dairy processors using dairy ingredients and manufacturers of dairy products.
Eight prototypes—food products that reflect current marketing trends using dairy ingredients—were formulated and produced. Formulation and technical sheets to accompany each prototype were completed. The prototype samples and fact sheets have been used for trade shows, presentations and demonstrations and will be used at upcoming events. Completed formulas include calcium-enriched hot cocoa, high-protein energy bars, smoothie mix, calcium-enriched scone mix, cream cheese filling, cappuccino mix, high-protein cookies and mocha dairy candy.
The prototypes were developed to reinforce the concept to food product developers that dairy ingredients are versatile and functional in new product formulations. The prototypes have been shown at both national and local trade shows, as well as events at Cal Poly San Luis Obispo’s Dairy Products Technology Center. The food products that were demonstrated helped to show that Cal Poly’s Dairy Ingredients Applications Program can provide needed technical support to food product developers.
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Comparison of MPC, SMP and WPC in Baked Products
Phillip S. Tong, Cal Poly San Luis Obispo
The objective for this project is to identify which dry dairy ingredient (skim milk powder, milk protein concentrate and whey protein concentrate) is most appropriate in bakery applications.
A model system was developed to determine the difference between nonfat dry milk (NFDM, 36 percent protein), whey protein concentrate (WPC, 34 percent protein) or milk protein concentrate (MPC, 42 percent protein) as an ingredient (3 percent) in a baked system. The model system used for this evaluation was a plain type muffin formula, which is bland in flavor, light in color and has good volume and grain. All three dairy ingredients evaluated scored fair or above in the subjective evaluation. The NFDM and WPC muffins yielded a mild dairy flavor, contributing no off-flavors. The MPC muffin had a slightly stronger flavor and was not as well balanced. All three products formed an acceptable golden brown color. The NFDM product was slightly darker in brown color than the other formulations. The MPC product had the best texture—it was moist, had a smooth grain and had the most overall height compared to NFDM and WPC muffins. The texture and volume of the NFDM and WPC products were similar.
All three dairy ingredients contributed to the flavor, texture, color and volume of the muffin. The perceived flavor difference in the NFDM and WPC formulas may result from the higher lactose content (52 percent lactose in both) compared to the MPC (16.5 percent lactose). The texture of the MPC muffin was rated slightly higher, probably as a result of the higher protein content. Milk proteins generally show good water-binding properties, which contribute to good moisture retention in the finished product.
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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
The general objective for this project is to evaluate procedures for scaling up the process of Beta lactoglobulin (b-LG) purification. The specific objectives are divided into two phases:
Phase 1
- Preparation of large-scale biosilicate filtration. Immobilization of all-trans-retinol to the surface of 5 kg of biosilicate Celite R-648TM
- Measurement and evaluation of different variables necessary for the pre-treatment of whey before being subjected to affinity purification
Phase 2
- Design and construction of model systems for processing whey and
purification of b-LG
- Analysis and characterization of the purified b-LG
- Mass balance of the different procedures designed to scale up the process
The two phases of this process have been successfully completed. The first one demonstrated that delipidation of whey was possible and efficient by using biosilicate filtration. Furthermore, the lipids recovered are mostly phospholipids. These substances are being actively sought in several laboratories today. An untapped resource has been identified, and a new area for innovation and value-added products for the dairy industry has been opened.
The second phase was the focus on the isolation of native b-LG with a single step adsorption process. The work concentrated on scaling up the procedure of purification of native b-LG using several types of industrial approaches at the pilot plant.
The process of affinity separation of b-LG in its native form using all-trans-retinal immobilized on Celite R-648TM was scaled up and applied to fractionate industrial sweet whey. Three different methods for mixing the Celite R-648TM and whey for the interaction between all-trans-retinal and b-LG were tried at pilot scale. The three methods used included:
1. A continuous operation using a column packed with Celite R-648TM.
2. A batch operation in a stirred tank.
3. A continuous operation using a fluidized Celite R-648TM particles bed column.
Adsorption and desorption of b-LG were carried out at pH 5.1 and 7.0, using 0.01 and 0.1M phosphate buffers, respectively. The phosphate buffer containing desorbed b-LG was concentrated 20 times using ultrafiltration and then freeze-dried. The packed column, stirred tank and fluidized bed column produced b-LG with purity of 80, >95 and >95 percent, respectively, and recovery of 0.65, 2.88 and 2.88g per kg of Celite R-648TM, respectively. The comparatively poor purity and recovery of b-LG in the case of the packed column was attributed to insufficient contact between the passing fluids and the Celite R-648TM during adsorption, desorption and intermittent washing. The fluidized bed column method, being a continuous operation with a gentle mixing action, was considered the best suited for further scale-up to the industrial level.
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Packaging Material Performance
John M. Krochta, UC Davis
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. Development of whey protein coating on paper and paperboard to improve paper material moisture-barrier, oil-barrier, printability, strength, color and/or gloss.
2. Development of whey protein-coated paper as an oxygen barrier to retard lipid oxidation of packaged food products.
3. Development of whey protein coating on plastic film to replace plastic oxygen barrier layers in laminated composite films.
Grease-barrier properties of whey protein-coated paperboard
Whey protein coatings on paperboard have grease-barrier properties comparable to commercial synthetic coatings. Glycerol and sucrose were found to be effective plasticizers for whey protein isolate (WPI) and WPC-80 (whey protein concentrate) coatings on paperboard. The addition of these plasticizers prevents the whey protein coating from cracking and flaking off the paperboard.
Sucrose-plasticized whey protein coatings on paperboard impart excellent grease resistance, similar to glycerol-plasticized coatings. A concern of possible plasticizer migration into the paperboard over time, with resulting cracking and flaking of the coating, was investigated by determining the effect of long-term storage at ambient temperature. Sucrose-plasticized whey protein coatings on paperboard retain excellent grease resistance after storage, in contrast to glycerol-plasticized coatings that lose their grease resistance.
WPI plasticized with sucrose has good grease barrier property in accelerated (high temperature) testing. WPC-80 plasticized with lower levels of sucrose has better grease barrier property than WPI coating in accelerated testing. This may be due to the different protein concentrations in WPI and WPC, as well as the plasticizing effect of the indigenous lactose in WPC 80. WPC-80 with hydrolyzed lactose plasticized with sucrose has good grease-barrier property in accelerated testing. However, the grease barrier property was impaired with increased storage time at room temperature. This may be due to the hydrolysis of lactose in WPC-80 into smaller molecules (glucose and galactose). The migration of these small molecules likely occurred during ambient storage. Finally, WPC-80 with 10 percent degree of hydrolysis plasticized with sucrose does not have good grease-barrier property.
Among all of the whey protein products, WPC-80 seems to give the best grease barrier property when coated on paperboard. The cost of whey protein material will be substantially reduced with utilization of WPC instead of WPI.
Our studies have shown that whey protein coated on paperboard imparts excellent grease resistance. Gloss studies have shown that whey protein increases gloss of uncoated paperboard, and color studies have shown that low color and good transparency are 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. The research on whey protein coating on paperboard is very timely because of the recent withdrawal of 3M’s fluorocarbon coating—industry’s most widely used grease barrier. Presently, manufacturers are eagerly seeking alternative coatings. Commercial implementation of whey protein for coating paper and paperboard can result in large-volume utilization of whey.
Oxygen-barrier properties of whey protein-coated plastic
Whey protein coatings on plastics have oxygen-barrier properties comparable to commercial synthetic, oxygen-barrier coatings. Heat-denatured aqueous solutions of WPI with various plasticizers were applied on corona-discharge treated low-density polyethylene (LDPE) and polypropylene (PP) films. Oxygen permeabilities (OP) of the resulting WPI-coated plastic films were determined under various temperature and relative humidity (RH) conditions. The OP of WPI-coated LDPE film increased approximately twofold for every 100C rise in temperature, a typical response to temperature. OP of WPI-coated LDPE films also increased with rising relative humidity in the range of 30 percent to 85 percent. WPI-coated LDPE film had lowest OP at the lowest RH, as expected. All the WPI-coated plastic films had good appearance and adhesion between the coating and the base film.
The type of plasticizer used (0.6 M sorbitol, sucrose, propylene glycol or PEG) significantly influenced OP of the WPI-coated plastic films. WPI-coated films containing sucrose plasticizer had the best barrier to oxygen. OP of the WPI-coated LDPE film plasticized with sucrose was only 0.5 percent that of the uncoated LDPE film at the same conditions. This means that the oxygen barrier of the WPI-coated LDPE film was 200 times better than the uncoated LDPE film. Oxygen barrier property of the WPI-coated creased in order of sucrose, sorbitol, glycerol, propylene glycol and PEG 200.
The gloss of the WPI-coated plastic films was affected by the type (sorbitol, sucrose, propylene glycol, PEG) and concentration (glycerol: 20%, 35%, 50%, 70%) of plasticizer used. The gloss units of the coated films with sucrose were even greater than normal base plastic films without coating.
Coating haze was calculated as the difference in the gloss values measured at an angle of 60 degrees and 20 degrees from the normal to the coating surface, respectively. The haze index indicates a measure of the irregularity and heterogeneity of the surface. The results indicate that the WPI coating itself would not give any additional irregularity and heterogeneity to the surface of base films.
A Hunter LabScan colorimeter was used to assess the color of the WPI-coated films. Regardless of the base plastic, the WPI coatings with various plasticizers of different concentrations did not affect significantly the color of the resulting WPI coated films. Any color differences between WPI-coated and uncoated films could not be observed with the human naked eye.
Almost identical oxygen-barrier, gloss, haze and color results were obtained when substituting WPI with 80 percent WPC in the coating formulations. Thus, the less-expensive 80 percent WPC can likely be used for this application.
Properties of whey protein-coated plastic
Common synthetic polymer films made from LDPE and PP are excellent moisture barriers, but they must be coated with expensive synthetic polymers to provide an oxygen barrier. The resulting structures are expensive and non-recyclable. Replacing these synthetic oxygen-barrier coatings with whey protein coatings would provide a new, value-added use for whey protein. The cost of WPC is lower than the synthetic oxygen-barrier polymers. Furthermore, the whey protein coatings could be removed from the LDPE and PP using chemical or enzymatic means, making the LDPE and PP recyclable. These whey protein coating removal processes are currently being researched in our lab.
It is possible to form coatings based on either WPI or WPC on common synthetic polymer films made from LDPE and PP. The LDPE and PP films must be treated with corona discharge to modify their surfaces in order to achieve well-adhering whey protein coatings. The resulting whey protein-coated films have excellent oxygen-barrier properties—much better than the uncoated LDPE or PP films, at low to intermediate RH. The whey-protein-coated films also have excellent gloss and low color. Results were almost identical for WPI- and WPC-based coatings, indicating that the lower-cost WPC could be used for this purpose. Thus, whey protein coatings have excellent potential for replacing existing synthetic oxygen-barrier coatings on LDPE and PP films. Recent demonstration in a related project that whey protein films can be extruded suggests that extrusion coating of whey protein onto LDPE and PP should be possible.
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Evaluation of Cream Composition, Handling, and Processing Factors That can Influence Churning Efficiency and Butter Quality
Phillip S. Tong, Cal Poly San Luis Obispo
The objectives of this project are to:
1. Identify key factors in the physical properties of cream, and the handling and processing of cream, that influence churning efficiency and quality (shortness and emulsification/leakiness) of butter.
2. Characterize key physical properties of cream that affect churning efficiency and butter quality utilizing techniques not normally present or not economically prudent in plant quality control laboratories, but accessible through universities or contract research laboratories.
A system was developed whereby pilot-scale batches of cream (10-20 gal) could be tempered under controlled experimental conditions to establish variable solid-to-liquid fat ratios in cream prior to churning. Experimental batches of cream were churned using the Simon Freres Contimab 2 Continuous Butter Churn or an Egli Continous Butter Churn. Baseline process conditions of cream volumetric flow rate of 3 GPM, 1,500 RPM beater speed and 40 RPM working section resulted in butter containing approximately 16.5 percent moisture. Procedures for quantification of the solid-to-liquid fat ratio in milkfat were developed using differential thermal analysis (DSC-2920,TA Instruments). The method involves heating the test sample to 550C and keeping it isothermal for 10 minutes, followed by cooling to 400C at a rate of 100C per minute and then generating a thermogram of the sample from 400C to 550C at the rate of 50C per minute. Confocal microscopy is being developed to examine the crystalline habit of the milkfat products.
Aging times at 50C for 0, 3 or 6 hours, and heating rate from 5-100C in 10 or 100 minutes were studied. Faster heating rates and shorter aging time resulted in butters with higher fat loss to buttermilk.
Butters made from milkfat with different chemical compositions had different thermal, textural and rheological properties. When cows were fed a diet supplemented with a fat source of canola oil, long-chain oleic acid content of milkfat increased significantly and a more spreadable butter resulted. Regardless of their milkfat compositions, the rheological properties of butters showed strong temperature and frequency dependence. Quick cooling caused the formation of a high quantity of small crystals, resulting in a harder butter. This temper treatment also resulted in the hardest butters, made significantly harder with the addition of the high melting triacylglycerol, tripalmitin. In extreme opposite, the T6,21,12/t2,2,15 tempering scheme, commonly known as ALNARP, was originally designed to produce a soft butter from winter seasonal cream. This is because the “cold-warm-cold” temperature pattern that promotes the slow growth of large fat crystals results in a softer butter. Addition of tripalmitin to the T6,21,12/t2,2,15 butter did not result in a significant increase in hardness. Differences in microstructure using confocal laser microscopy were seen for the different tempering conditions, but further quantification of the images is needed to clearly express this information.
A process system and analytical methodology have been established, whereby controlled experiments can be conducted to characterize how key process factors can influence milkfat products. This will allow us to better understand the factors influencing butter quality. Based on these studies, we discovered that processing variables for both cream and butter processing can influence the rheological properties of butter and its ultimate hardness/spreadability. The project further demonstrated that confocal laser microscopy may be a useful tool in characterizing any structural changes due to processing conditions.
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Properties of Milk Protein Concentrate for Cheesemaking
Nana Y. Farkye, Cal Poly San Luis Obispo
The objectives for this project are to:
1. Characterize and determine the physico-chemical properties of milk protein concentrate (MPC).
2. Standardize whole milk with milk protein concentrate for lower fat Cheddar cheese manufacture.
MPC is a relatively new dairy ingredient produced by membrane filtration of skim milk. It is available in a liquid form or as dry powder. MPC contains high levels of protein and calcium, and low lactose content. The casein-to-whey-protein ratio of MPC used in this study was similar to the standard 80:20 ratio found in milk. Both dried and liquid MPC were used to standardize whole milk or cream, respectively, for the manufacture of reduced-fat Cheddar cheese. Cheese yields were more than 150 percent higher when whole milk was standardized with MPC for reduced-fat cheesemaking. The yield increase was due to higher levels of total solids in the milk containing MPC (17 percent vs. 10 percent) and higher recoveries of total solids. Also, by adjusting the casein-to-fat ratio with MPC, cheesemakers can avoid operating a separator to remove a portion of the milkfat as cream. MPC also has an advantage over skim milk powder because it contains less lactose (18 percent) compared to ~50 percent for SMP, thereby eliminating the chances of undesirable fermentations during cheese manufacture and ripening. Furthermore, increasing vat capacity by using high-solids milk has additional economic benefits to the manufacturer because of savings in labor costs as more cheese can be produced per-unit time. Ripening of cheese made from MPC-fortified milk, as measured by proteolysis, is generally slower than in cheese made from whole milk standardized with skim milk. The flavor attributes of cheese containing MPC were similar to those without MPC. Also, MPC cheeses had little or no bitter flavors, whereas bitter flavor notes were detected in the cheeses made without MPC.
MPC is a high-protein, low-lactose and high-calcium dairy ingredient. The casein-to-whey-protein ratio in MPC of 80:20 is similar to that in milk. The study demonstrates the potential for using MPC to standardize cheese milk to give high yields and good quality.
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