Progress 07/01/07 to 06/30/12
Outputs
OUTPUTS: We have developed a high pressure processing facility at the University of Nebraska-Lincoln. It has 2-liter processing vessel and can apply pressures up to 900 MPa. This system has been used to evaluate the quality and safety of various food products including eggs, nuts, meats, and peanut sauces. In additions to its use by researchers, the food processing center at the University of Nebraska-Lincoln has been providing service to several food industries to evaluate this emerging technology. 1. High pressure processing of peanut sauces: Recent Salmonella outbreaks have prompted the need for new processing options for peanut products. Traditional heating kill-steps have shown to be ineffective in lipid-rich matrices such as peanut products. High pressure processing is one such option for peanut sauce because it has a high water activity, which has proved to be a large contributing factor in microbial lethality due to high pressure processing. Four different formulations of peanut sauce were inoculated with a five strain Salmonella cocktail and high pressure processed. 2. High pressure processing of eggs: The goal of this funded project (collaboratively conducted with Dr Stephanie Jung of Iowa State University) is to develop HP treatments of egg white that retain or enhance its functional properties and to examine HP treatment effects on constituent proteins. This year the effects HP treatment on egg white protein denaturation were examined by SDS gel electrophoresis, Circular Dichroism, and Raman spectroscopy. 3. High pressure processing of Beef: Work on the beef projects was also conducted in collaboration with Dr Stephanie Jung of Iowa State University. A presentation was made at the Reciprocal Meats Conference (June 2009) concerning the work on HP processing of beef. This presentation was made by the graduate student (Brittni Fleer) and reported an increased level of postmortem proteolysis resulting from HP treatment, however, there was little or no change in meat texture. Additionally, HPLC was used to characterize the profile of peptides resulting from HP-induced proteolysis. At present the sequence and identity of major peptides in these separations is being determined. PARTICIPANTS: Stephanie Jung, Iowa State University, Jayne Straton, University of Nebraska-Lincoln. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
1. High pressure processing of peanut sauces: Results indicate that increasing pressure or increasing hold time increases log10 reductions. The Weibull model was fitted to each kill curve, with b and n values significantly optimized for each curve (p-value < 0.05). Most curves had an n parameter value less than 1, indicating that the population had a dramatic initial reduction, but tailed off as time increased, leaving a small resistant population. ANOVA analysis of the b and n parameters show that there are more significant differences between b parameters than n parameters, meaning that most treatments showed similar tailing effect, but differed on the shape of the curve. Comparisons between peanut sauce formulations at the same pressure treatments indicate that increasing amount of organic peanut butter within the sauce formulation decreases log10 reductions. This could be due to a protective effect from the lipids in the peanut butter, or it may be due to other factors such as nutrient availability or water activity. Sauces pressurized at lower temperatures had decreased log10 reductions, indicating that cooler temperatures offered some protective effect. Log10 reductions exceeded 5 logs, indicating that high pressure processing may be a suitable option as a kill-step for Salmonella in industrial processing of peanut sauces. Future research should include high pressure processing on other peanut products with high water activities such as sauces and syrups as well as research to determine the effects of water activity and lipid composition with a food matrix such as peanut sauces. 2. High pressure processing of eggs: Pressure treatments resulted in significant egg white protein denaturation (loss of alpha helix and increase in beta sheet structures) however the extent of aggregation could be limited by inclusion of agents that lower pH. HP-induced denaturation under these conditions was also shown to increase the ability of proteolytic enzymes to hydrolyze constituent proteins. The major finding was that HP treatment could be used to make egg white protein more digestible without the application of heat. 3. High pressure processing of Beef: Work using HP treatments to enhance meat texture and flavor served as the basis for a MS thesis project. Brittni Fleer successfully defended her MS thesis (Effects of high pressure treatment on bovine muscle) last April and graduated in May of 2009.
Publications
- Stiles, T. 2010. The Effects of High Pressure Processing on Peanut Sauce Inoculated with Salmonella. M.Sc. Thesis. University of Nebraska-Lincoln.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Egg: The goal of this funded project (collaboratively conducted with Dr Stephanie Jung of Iowa State University) is to develop HP treatments of egg white that retain or enhance its functional properties and to examine HP treatment effects on constituent proteins. This year the effects HP treatment on egg white protein denaturation were examined by SDS gel electrophoresis, Circular Dichroism, and Raman spectroscopy. Beef: Work on the beef projects was also conducted in collaboration with Dr Stephanie Jung of Iowa State University. A presentation was made at the Reciprocal Meats Conference (June 2009) concerning the work on HP processing of beef. This presentation was made by the graduate student (Brittni Fleer) and reported an increased level of postmortem proteolysis resulting from HP treatment, however, there was little or no change in meat texture. Additionally, HPLC was used to characterize the profile of peptides resulting from HP-induced proteolysis. At present the sequence and identity of major peptides in these separations is being determined. Peanut Butter: This is a USDA CSREES Organic Agriculture Research and Extension Initiative funded project that involves several parties including a organic peanut butter processor, high pressure processing co-packer and the Food Processing Center. The output of the research will determine if high pressure processing is an effective post processing treatment for inactivating Salmonella in peanut butter and peanut sauces. The research is currently being conducted at the Food Processing Center (FPC). Nuts: High pressure processing of vacuum-packaged nuts (pecans and walnuts) were evaluated at various pressures (400 and 600 MPa) and treatment time (5, 10, and 20 minutes) were evaluated for inactivation of Salmonella. PARTICIPANTS: Stephanie Jung, Iowa State University. TARGET AUDIENCES: Beef processors, egg processors, nuts processors, and peanut butter manufacturers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Egg: Pressure treatments resulted in significant egg white protein denaturation (loss of alpha helix and increase in beta sheet structures) however the extent of aggregation could be limited by inclusion of agents that lower pH. HP-induced denaturation under these conditions was also shown to increase the ability of proteolytic enzymes to hydrolyze constituent proteins. The major finding was that HP treatment could be used to make egg white protein more digestible without the application of heat. Beef: Work using HP treatments to enhance meat texture and flavor served as the basis for a MS thesis project. Brittni Fleer successfully defended her MS thesis (Effects of high pressure treatment on bovine muscle) last April and graduated in May of 2009. A manuscript developed from Brittni's work will be submitted for publication shortly. Peanut Butter: Due to the most recent peanut butter recall from Salmonella contamination, post processing options are needed to help ensure food safety. One of the outcomes from this research is to determine the effectiveness of HPP on the inactivation of pathogens in peanut butter and peanut sauces. The high pressure processing has provided food processors in the Midwest the opportunity to explore non-thermal treatment for inactivation of harmful pathogens in foods. The Food Processing Center is currently educating food processors about HPP technology through site-visits and its web-site. It is anticipated that more research will be sparked as the technology becomes more affordable for small food processors. Nuts: Due to low water activity of nuts, microorganisms were highly resistant to high pressure. Less than 2 log reduction was achieved at the highest (600 MPa) and longest treatment time (20 minutes) tested in this experiment.
Publications
- Kelly, A., M. Zeece. 2009. Applications of novel technologies in processing functional foods. The Australian Journal of Dairy Technology 64: 12-15.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Outputs Effect of High Pressure Processing on Egg The goal of this funded project (conducted by Dr. Zeece in collaboration with Dr Stephanie Jung of Iowa State University) is to develop HP treatment conditions of egg white that retain or enhance its functional properties and to study the effects of treatment on constituent proteins. Specifically, the effects of HP treatment on egg white functionality were evaluated by measurement of foaming ability. The effect of HP treatment on egg white proteins were evaluated by measurement of free thiol content (DTNB reaction), extent of aggregation (SDS-PAGE), protein structure (CD) and digestibility. The treatments examined include 3 pressure levels (ambient, 400, and 600 MPa), two pH levels (7.6, and 8.8), and addition of a disaccharide (1% sucrose or trehalose). Effect of High Pressure Processing on Beef Work on two funded projects was conducted by Dr. Zeece in collaboration with Dr Stephanie Jung of Iowa State University. The goal of the first project was to develop a HP treatment process that resulted in a value-added product with desirable and consistent texture. LD muscle from undervalued (select grade) carcasses. The goal of the second project was to identify and characterize bioactive peptides (ACE inhibitors) resulting from HP treatment of beef and examine its effect on DPP enzyme activity. PARTICIPANTS: Stephanie Jung, 1436 Food Sciences Building, Department of Food Science and Human Nutrition, Ames, Iowa 50011-1061, Phone: (515) 294-2544, Fax: (515) 294-8181. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Effect of High Pressure Processing on Egg Egg white treated at pH 7.6 (400 or 600 MPa) was found to have better foaming ability than pH 8.8. A large decrease in free thiol level was found for HP-treated egg white at the higher pH suggesting that increased disulfide linkages may be contributing negatively to foaming ability. Pressure treatments at the higher pH also resulted in more aggregates as determined by SDS-PAGE electrophoresis. Overall, pressure treatment at 400 MPa did not substantially alter the foaming ability when compared to untreated egg white. However, pressure treatment had the additional benefit of increasing the pepsin digestibility of the proteins. Electrophoresis showed that pepsin digestion of ovalbumin in HP-treated samples was much greater compared to untreated samples. This observation was reinforced by a decreased alpha helical content (measured by CD) in egg proteins following HP treatment. Together, these results suggest that HP-induced protein unfolding was responsible for the observed increase in digestibility. Inclusion of carbohydrates (1% level) may have slightly decreased foaming ability and had no observed effect on egg proteins as measure by the tests mentioned above. Effect of High Pressure Processing on Beef Work on first project (entree development) found that HP treatment at 400-600 MPa resulted in a notable increase in soluble collagen and concomitant decrease in shear force. Increased soluble collagen and decreased shear force likely resulted from increased proteolysis that was induced by the pressure treatment. HP treatment also improved the meat texture as judged by a taste panel. Work in the coming year will explore HP treatments in the 200-400 MPa range to optimize its results on meat flavor and texture. Results of this work were presented as a poster presentation at the Reciprocal Meats Conference meeting in July 2008. Work on the second project (bioactive peptides) has shown that HP treatment increased the level of post-mortem proteolysis in LD muscle. Degradation of major myofibrillar proteins such as myosin, tropomyosin, troponin, and actin was evident from electrophoretic analysis. Analysis of the peptide fraction produced resulting from post-mortem by mass spectrometry confirmed the identity of these proteins as well as other key proteins (e.g., nebulin). Work is currently underway to identify smaller peptides (<1000 daltons) that have biological activity (ACE inhibition, antioxidant activity and meat flavor). These results together with those of our other project concerning use of HP treatment to develop an entree demonstrates the beneficial affects of the process and also the underlying mechanism responsible for those changes.
Publications
- No publications reported this period
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: Investigation of high pressure treatment of beef: Two proposals were funded by the Nebraska Beef Council in collaboration with Dr Steve Jones of Animal Science regarding the use of high pressure treatment to enhance the quality of beef. 1. "Enhancing healthiness and nutritional quality of beef by high pressure treatment: An investigation of bioactive peptides." ($53,000) 2. "Use of high pressure-treatment to develop value-added beef entrees." ($56,000) As a result of this funding, graduate and undergraduate student research projects have been established to work on these projects. Also, a good relationship has been established with the Nebraska Beef Council, representing major stakeholders for this state. This relationship will contribute to the image of the Food Science department as providing innovative approaches to enhance the value, consumption, and safety of beef. Additionally, an excellent collaborative relationship has been established with Dr Jung at Iowa State
University. Use of High Pressure treatment to enhance egg functionality: A proposal was funded by the Mussehl Poultry Endowment to develop high pressure treatments for egg white ($25,000). This project "Enhanced egg white functionality by use of high hydrostatic pressure treatment." will also be conducted in collaboration with Dr Jung at Iowa State University. Improvement of protein functionality and digestibility and via High Pressure treatment: Collaborative research has been conducted concerning High Pressure treatment of milk proteins with Dr Alan Kelly of University College Cork, in Ireland. This work showed that High pressure treatment improved the digestibility of beta lactoglobulin (a major allergen) and shows promise for development of milk-based products with reduced allergenicity (1). This research collaboration is on-going and additional projects are underway. High pressure homogenizer for pasteurizing apple juice and cider: The objective of this study was to investigate
the effect of high pressure homogenizing alone and in combination with antimicrobial chitosan (two types) at two different concentrations on the reduction of E. coli K-12 in apple juice and cider. Apple juice and apple cider were sourced from a local grocery store. E. coli K-12 strain culture was grown aerobically at 35 degrees Celsius in tryptic soy broth for 16-18 hours. Samples were inoculated with bacterial culture. Low molecular weight chitosan was prepared in 1% acetic acid. Water soluble chitosan (1% solution) was obtained by dissolving in distilled water under magnetic stirring. Final concentration of 0.1% and 0.01% was obtained by dissolving the 1% solution of the chitosan in apple juice and apple cider. A bench-top-high-pressure homogenizer was used for the treatment of the juice as well as the cider.
PARTICIPANTS: Saurabh Kumar, Graduate Student, University of Nebraska-Lincoln; Federico M. Harte, Collaborator, University of Tennessee; Harshavardhan Thippareddi, Co-PI, University of Nebraska-Lincoln; Jung, Collaborator, Iowa State University; Zeece, Co-PI, University of Nebraska-Lincoln; Jones, S., Collaborator, University of Nebraska-Lincoln.
TARGET AUDIENCES: Apple processors Meat processors
Impacts
High pressure homogenizer for pasteurizing apple juice and cider: The homogenizing process involves forcing the liquid on a nozzle and the pressure energy is converted to thermal energy. Though heat was removed from the valve surroundings using a controlled temperature water bath, still the temperature increased with the increase in pressure. The temperature increase indicates that the bacterial inactivation due to high pressure homogenization involves both thermal and non-thermal processes. The apple juice gets heated at the homogenization valve. The time it takes for the apple juice to travel from the treatment region to the end of the cooling chamber was less than 20 seconds. Bacterial inactivation due to non-thermal component of the process is predominant at less than 250 MPa. There was no significance difference between the types of chitosan and control (no chitosan) on E.coli inactivation. As the pressure increased, the microbial inactivation increased. Beyond 250
MPa, all inoculated bacteria were inactivated. Even though, chitosan did not have any effect on microbial inactivation, it had a significant effect in controlling the growth of E. coli K-12 in apple juice during the shelf life study at room temperature subsequent to the high pressure homogenization in the pressure region from 200 to 350 MPa. There was no significant difference between the types of chitosan and levels of chitosan on controlling the growth of E. coli K-12 in apple juice subsequent to the high pressure homogenization.
Publications
- Zeece, M. G., T. Huppertz, and A. Kelly. 2008. Effect of high-pressure treatment on in vitro digestibility of beta lactoglobulin. Innov. Emerg. Technol. Food Sci. 9:62-69.
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