Progress 02/01/15 to 01/31/18
Outputs
Target Audience:Egg processing industry, egg producers, a wide range of food and food ingredient industry utilizing processed egg products as ingredients in the products, such as bakery, dairy, dressing, confectionery, and meat industry, national and international researchers in egg and food science areas, governmental agencies related to egg processing, students in food and poultry sciences, and consumers Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A graduate student was trained through hands-on practices to acquire general lab techniques, sample handling and preparation, advanced analytical skills, and scientific writing skills for her future scientific research. The student acquired proper sample handling and preparation techniques to minimize changes in the samples during storage and sample preparation. The student was trained to acquire knowledge and techniques to perform the analyses to determine physicochemical and functional characteristics of egg white powder using various instruments, including pH meter, colorimeter, spectrophotometer, microplate reader, and texture analyzer. In addition, the student acquired knowledge and analytical techniques to prepare protein hydrolysates and analyze their antioxidant capacity and biological activity. The analytical skill sets to determine functional characteristics of protein-rich sources and protein hydrolysates will be the great assets for the student's future research career in various food industry sectors. How have the results been disseminated to communities of interest?Four abstracts were presented at local and international professional conferences such as Institute of Food Technologist (IFT) and Poultry Science Association (PSA) annual meetings and Association of 1890 Research Symposium (ARD) and UMES research symposiums in order to share the results of the project with targeted audience. Master's thesis was also published to disseminate the information generated by this project to target audience. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Irradiation of shell eggs significantly reduces the viscosity of egg white even at lower doses (< 2 kGy) to make it watery. Watery egg white can facilitate the separation of egg white to improve its yield and eliminate the homogenization step. It also can facilitate the process to separate individual functional egg white proteins and produce bioactive peptides from egg white. However, irradiation can cause oxidative damages to proteins and consequently impair protein functional properties. However, little information is available regarding impacts of irradiation of shell eggs on physicochemical and functional properties of liquid and spray-dried egg white products and bioactivities of the functional proteins and peptides. For Objective I, shell eggs irradiated at 1 and 2 kGy were broken and liquid egg white (LEW) was collected. LEW collected from irradiated shell eggs was not homogenized, while that from non-irradiated was to reduce its viscosity to conduct physicochemical analysis and spray-drying. A portion of LEW was spray-dried using a lab-scale spray drier to make egg white powder (EWP). As expected, the viscosity of irradiated LEW (IR-LEW) was significantly lower than that of the non-irradiated (Non-IR; p<0.05). The viscosity of IR-LEW at 1 kGy was not different from that at 2 kGy, indicating that the irradiation dose even at 1 kGy can completely break the ovomucine network responsible for the viscosity of egg white. Protein solubility and pH were not changed by irradiation, but protein oxidation, surface sulfhydryl content of the proteins (SSC), and color (lightness (L*) and yellowness (b*)) were significantly lower in Non-IR and IR-LEW at 1 kGy than at 2 kGy, while total sulfhydryl contents of the proteins (TSC) increased as irradiation doses increased (p<0.05). These results indicated that irradiation of shell eggs at 2 kGy may cause protein oxidation and configurational changes in protein in LEW, probably affecting protein functionality. Foaming capacity and stability and emulsion stability of IR-LEW at 1 and 2 kGy were significantly greaterthan those of Non-IR (p<0.05). Textural properties such as hardness, cohesiveness, resilience, and chewiness of the thermal gel made from IR-LEW at 1 and 2 kGy were significantly lower than those from Non-IR (p<0.05). In addition, water holding capacities (WHC) of thermal gels made from Non-IR and IR-LEW at 1 kGy was significantly higher than that at 2 kGy (p<0.05). These results indicated that irradiation may cause configurational changes in egg white proteins to improve surfactant ability of egg white proteins between two immiscible phases (water/lipid in emulsion and air/water in foam) but adversely affect their water binding and thermal coagulation abilities. The volumes of angel cake prepared using the Non-IR and IR-LEW at 1 kGy were significantly higher than those using at 2 kGy (p<0.05). Cooking yields of beef patties made with IR-LEW were not different from those with Non-IR. However, the textural properties such as hardness, cohesiveness, and chewiness of meat patties made of IR-LEW at 1 and 2 kGy were significantly lower than those with Non-IR probably due to their lower viscosity (p<0.05). IR-egg white powder (EWP) at 1 and 2 kGy showed higher pH but lower lightness (L*), blueness (a*) and yellowness (b*) than did Non-IR-EWP (p<0.05). Protein solubility of EWP was not affected by irradiation, but the surface hydrophobicities of IR-EWP at 1 kGy and Non-IR-EWP were lower than at 2 kGy (p<0.05). Protein oxidation and SSC were higher and lower, respectively, in IR-EWP at 1 and 2 kGy than in Non-IR-EWP (p <0.05). These changes indicated that irradiation may cause partial denaturation and oxidation of proteins in EWP. However, they appeared to positively affect the functional properties of IR-EWP. Foaming capacity and stability of IR-EWP at 1 and 2 kGy were greater than those in Non-IR-EWP (p<0.05). Emulsion activity and stability were higher in IR-EWP at 1 kGy than at 2 kGy and Non-IR-EWP (p<0.05). IR-EWP at 1 and 2 kGy produced stronger thermal gels with higher WHC compared to Non-IR-EWP (p<0.05). However, hardness and chewiness of the thermal gel prepared from IR-EWP at 2 kGy were significantly lower than those at 1 kGy, indicating that irradiation at 2 kGy can cause relatively severer changes in protein structure and consequently negatively impact thermal gelation properties of IR-EWP. The addition of IR-EWP at both doses to angel cake did not change foaming and textural properties compared to Non-IR. On the other hand, the addition of IR-EWP significantly affected cooking yield, and texture profile of beef patties. Compared to the beef patties without EWP (No-EWP), Non-IR-EWP added beef patties showed higher cooking yield probably due to WHC by Non-IR-EWP. However, the IR-EWP-added beef patties, regardless of the irradiation dose, showed significantly lower cooking yield and higher textural parameters, such as hardness, cohesiveness, chewiness, and resilience, compared to the No-EWP and Non-IR-EWP. These results indicate that IR-EWP may act as a binding agent of meat particles in the beef patty, resulting in the decreased space within the patty to hold water and the increased textural integrity. For Objective 2, LEW collected from irradiated shell eggs was not homogenized, but that from non-irradiated was to reduce its viscosity for separation of functional proteins and enzyme hydrolysis to produce bioactive peptides. Ovotransferrin, ovalbumin, and ovomucine was separated from Non-IR and IR-LEW at 1 and 2 kGy using environmentally friendly sequential separation method developed in our lab. Irradiation at 1 and 2 kGy did not affect the extraction yield, separation efficiency, and purity of those proteins compared to those of Non-IR. LEW were hydrolyzed to prepare protein hydrolysates, using 3 proteases (Promod 278P (EC. 3.4.24.28, endopeptidase), Multifect 14L PR (EC 3.4.24.27) and Protease from Bacillus licheniformis (EC. 3.4.21.62)) with or without pre-heat treatment. It has been suggested that pre-heat treatment causes protein denaturation, leading to facilitating enzyme hydrolysis. Antioxidant capacity (as oxygen radical absorbance capacity (ORAC)) and angiotensin-I-converting enzyme (ACE) inhibition activity were evaluated in the protein hydrolysates. The results showed that irradiation did not cause protein degradation and changes in the hydrolytic characteristics of egg white proteins and did not affect the ACE inhibition and antioxidant capacity of the protein hydrolysates. The results suggested that pre-heat treatment and proteases, rather than irradiation, are the determinants for the effectiveness of enzyme hydrolysis. Pre-heat treatment considerably improved the effectiveness of enzyme hydrolysis. Multifect 14L protease produced the protein hydrolysates showing the higher ACE inhibition and antioxidant activity than did other proteases. In conclusion, this project showed that irradiation of shell eggs at 1 kGy can lower the viscosity of egg white and produce watery egg white that can be directly used, without homogenization, for spray drying, separation of functional proteins, and enzyme hydrolysis without negative impacts on their functionalities. The irradiation at 1 kGy improved the functional properties, such as foaming, emulsifying, and/or binding properties, of egg white products such as LEW and EWP while oxidative changes in egg white proteins was not or marginally occurred. It did not affect bioactivity of functional egg white proteins and its hydrolysates. Therefore, these results suggested that irradiation of shell eggs at 1 kGy has potentials to improve functional properties of egg white products and the efficiency of egg white processing.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Moon, S. H., Kim, J., Ahn, D. U., and Min, B. 2017. Impacts of low-dose irradiation of shell eggs on physicochemical and functional properties of liquid egg white. IFT17 Annual Meeting. June 25-28. Las Vegas, NV.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Nega, M., Min, B. R., Moon, S. H., and Ahn, D. U. 2017. Physicochemical and functional properties of egg white powder prepared from shell eggs irradiated at low doses. 2017 Poultry Science Association Annual Meeting. July 17-27. Orlando, FL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Nega, M. and Min, B. 2017. Physicochemical and functional properties of egg white powder prepared from irradiated shell eggs. ARD Research Symposium 2017. April 1-4, 2017. Atlanta, GA.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2017
Citation:
Nega, M. and Min, B. 2017. The physicochemical and functional properties of spray-dried egg white powder prepared from irradiated shell eggs. 2017 UMES Research Symposium 2017. April 18. Princess Anne, MD.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2017
Citation:
Nega, M. 2017. Effects of Low-dose Irradiation of Shell Eggs on physicochemical and Functional Properties of Spray-dried Egg White Powder and Activities of Egg White Peptides. MS Thesis. University of Maryland Eastern Shore, Princess Anne, MD.
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Progress 02/01/16 to 01/31/17
Outputs
Target Audience:Egg processing industry, egg producers, a wide range of food and food ingredient industry utilizing processed egg products as ingredients in the products, such as bakery, dairy, dressing, confectionery, and meat industry, feed industry, national and international researchers in egg and food science areas, governmental agencies related to egg processing, students in food and poultry sciences, and consumers Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A graduate student was trained to acquire general lab techniques, sample handling and preparation, and advanced analytical skills required to conduct the project through hands-on practices. The student received general lab safety training. The student acquired proper sample handling and preparation techniques to minimize changes in the samples during storage and sample preparation. The student was trained to acquire knowledge and techniques to perform the analyses to determine physicochemical and functional characteristics of egg white powder using various instruments, including pH meter, colorimeter, spectrophotometer, microplate reader, and texture analyzer. In addition, the student acquired knowledge and analytical techniques to prepare protein hydrolysates and analyze their antioxidant capacity and biological activity. The analytical skill sets to determine functional characteristics of protein-rich sources and protein hydrolysates will be the great assets for the student's future research career in various food industry sectors. How have the results been disseminated to communities of interest?Four abstracts were prepared and submitted to local and international professional conferences such as Institute of Food Technologist (IFT) and Poultry Science Association (PSA) annual meetings and Association of 1890 Research Symposium (ARD) and UMES research symposiums in order to share the results of the project with targeted audience. They were all accepted for presentation in those conferences in 2017. What do you plan to do during the next reporting period to accomplish the goals?The objective I and a part of objective II have been completed. For the objective II, bioactive peptides was prepared by enzyme hydrolysis of liquid egg white and their bioactivities was determined. Functional egg white proteins, including lysozyme, ovomucin, ovotransferrin, and ovalbumin from liquid egg white have been isolated. Their activities as affected by irradiation will be determined during the next reporting period. In addition, the results will be presented in local, national and international professional conferences and the articles will be prepared and submitted to a peer-reviewed journal. One graduate student will graduate in 2017.
Impacts
What was accomplished under these goals?
The objective of the project accomplished in this period was to determine the effects of low-dose irradiation of hen eggs at 1 and 2 kGy on the physicochemical and functional properties of spray-dried egg white powder (Objective 1) and bioactivities of egg white protein hydrolysates (peptides) (Objective 2), compared to non-irradiated. Irradiated shell eggs at 1 and 2 kGy using electron beam were immediately broken and liquid egg white was collected for spray-drying and enzyme hydrolysis. Only liquid egg white collected from non-irradiated shell eggs was homogenized to reduce the viscosity for further processing. A portion of liquid egg white was spray-dried using a laboratory-scale spray drier to make egg white powder (EWP) samples. The dried products were subdivided into portions, packaged in oxygen permeable zipper bags and stored at -18 °C until analysis. The other portion of liquid egg white were enzyme-hydrolyzed to prepare protein hydrolysates. A portion of diluted liquid egg white (adjusted pH = 6.8-7.0) were centrifuged and the supernatant was collected as the sample for enzyme hydrolysis. The other portion of the diluted liquid egg white underwent pre-heat treatment to facilitate enzyme hydrolysis. Protein hydrolysates were generated from the egg white supernatant (Non- or Pre-Heated) using 3 proteases: Promod 278P (EC. 3.4.24.28, endopeptidase), Multifect 14L PR (EC 3.4.24.27) and Protease from Bacillus licheniformis (EC. 3.4.21.62). Enzyme hydrolysates were centrifuged and the resulting supernatant was freeze-dried, and the powder was used as the egg white hydrolysate. Antioxidant capacity (as oxygen radical absorbance capacity (ORAC)) and angiotensin-I-converting enzyme (ACE) inhibition activity were evaluated in the protein hydrolysates. EWP produced from shell eggs irradiated (IR) at 1 and 2 kGy showed significantly higher pH but lower lightness (L*), greenness (-a*) and yellowness (b*) compared to that from non-irradiated (Non-IR). Protein solubility of EWP was not affected by irradiation, but the surface hydrophobicity of IR-EWP at 2 kGy was higher than that at 1 kGy and Non-IR-EWP. Protein oxidation and surface sulfhydryl content were higher and lower, respectively, in IR-EWP at both doses than in Non-IR-EWP. These changes in EWP indicated that irradiation may cause partial denaturation and oxidation of the proteins in EWP. However, they appeared to positively affect the functional properties of IR-EWP. Foaming capacity and stability of IR-EWP at both doses were significantly greater than those of Non-IR-EWP. Emulsion activity and stability were significantly higher in IR-EWP at 1 kGy than at 2 kGy and Non-IR. Thermal gelation properties of EWP were also affected by irradiation. IR-EWP at both doses produced stronger thermal gels with better water holding capacity, compared to Non-IR-EWP. However, hardness and chewiness of the thermal gel prepared from IR-EWP at 2 kGy were significantly lower than those at 1 kGy , indicating that irradiation at over 1 kGy can cause relatively severer changes in protein structure and consequently negatively impact thermal gelation properties of IR-EWP. The effects of addition of IR-EWP on quality parameters in angel cake and beef patty were also determined. For the angel cake, the color, foaming property and textural properties of the IR_EWP-added were not different from those of the Non-IR-EWP-added, regardless of irradiation doses. However, the addition of IR-EWP significantly affected color, cooking yield, and texture profile of the beef patties. The beef patties made without EWP (No-EWP) was prepared as a negative control. Addition of the Non-IR-EWP to beef patties significantly decreased their lightness and redness and increased their cooking yield, compared to No-EWP, but did not affect their textural properties. The increased cooking yield is likely due to the water holding capacity of the EWP. Addition of IR-EWP further decreased the lightness of the beef patties. However, unlikely the Non-IR-EWP, the IR-EWP-added beef patties, regardless of the irradiation dose, showed significantly lower cooking yield and higher textural parameters, such as hardness, cohesiveness, chewiness, and resilience, compared to the No-EWP and Non-IR-EWP. These results indicate that IR-EWP may act as a binding agent of meat particles in the beef patty, resulting in the decreased space within the patty to hold water and the increased textural integrity. In summary, irradiation of shell eggs caused protein oxidation and changes in pH, color, surface sulfhydryl, and surface hydrophobicity of egg white powder. However, it improved foaming and emulsion properties and water holding capacity and strength of thermal gel. Interestingly, egg white powder prepared from shell eggs irradiated at 1 kGy showed greater foam stability and emulsion activity and stability than did that at 2 kGy. The addition of the powder prepared from irradiated egg white did not affect quality of angel food cake such as foaming properties. The addition of the powder made from irradiated egg white showed lower cooking yield but harder beef patty, indicating that irradiation increase the binding capacity of egg white protein to meat particle and consequently the structural integrity of the beef patty. Overall, the results of this study indicated that irradiation of shell eggs, especially at low dose (< 2 kGy) has potentials to improve the functional properties of egg white powder. In the enzyme hydrolysis study of liquid egg white (objective II), the SDS-PAGE band pattern of liquid egg white (LEW) and egg white hydrolysates showed that irradiation did not cause protein degradation and the hydrolytic characteristics of egg white proteins. The effectiveness of enzyme hydrolysis was dependent up on pre-heat treatment and types of proteases. Pre-heat treatment considerably improved the effectiveness of enzyme hydrolysis. The effectiveness of the Multifect 14L on protein hydrolysis was significantly higher in Non-IR EW than in IR-EW. The ACE inhibition activity of No-Heated protein hydrolysates were only observed in the Multifect 14L protease-catalyzed protein hydrolysates. The ACE inhibition activity of Pre-Heated protein hydrolysates catalyzed by Multifect 14L protease were the higher than those by other enzymes. The results indicates that the ACE inhibition activity of the protein hydrolysates was not affected by irradiation, but depending on enzyme and pre-heat treatment. The similar results were obtained in the antioxidant capacity of the protein hydrolysates. The ORAC values of egg white protein hydrolysates were not affected by irradiation, but improved by pre-heat treatment. Protease Multifect 14L PR-catalyzed egg white protein hydrolysates showed the greatest ORAC value, followed by Promod 278P and Protease from Bacillus licheniformis enzymes. Egg white proteins have been found to be an excellent source for bioactive peptides with various biological activities, including ACE-inhibitory activity and antioxidant capacity. The results suggested that irradiation did not affect the ACE inhibition and antioxidant capacity of enzymatic hydrolysates of egg white proteins. Their activities may depends on the enzyme type and degree of protein denaturation. This study showed that irradiated egg white can be spray-dried to produce egg white powder without homogenization due to the viscosity-lowering effect of irradiation. Irradiation is a proven decontamination technology in shell eggs to control Salmonella. Therefore, irradiation at low doses (< 2 kGy) has potentials to improve the efficiency of egg white processing, such as facilitating egg white separation from yolk and shell, the flow of egg white between the processing steps, and enzyme hydrolysis and removing homogenization process for pasteurization and drying processes in addition to functional properties and safety of egg white powder.
Publications
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2017
Citation:
Nega, M. and Min, B. 2017. Physicochemical and functional properties of egg white powder prepared from irradiated shell eggs. ARD Research Symposium 2017. April 1-4. Atlanta, GA.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2017
Citation:
Moon, S. H., Kim, J., Ahn, D. U., and Min, B. 2017. Impact of low-dose irradiation of shell eggs on physicochemical and functional properties of liquid egg white. IFT17 Annual Meeting & Food Expo. June 25-28. Las Vegas, NV.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2017
Citation:
Nega, M. and Min, B. 2017. The physicochemical and functional properties of spray-dried egg white powder prepared from irradiated shell eggs. 2017 UMES Research Symposium. April 18. Princess Anne, MD.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2017
Citation:
Nega, M., Min, B. R., Moon, S. H., and Ahn, D. U. 2017. Physicochemical and functional properties of egg white powder prepared from shell eggs irradiated at low doses. 2017 Poultry Science Association (PSA) annual meeting. July 17-20. Orlando, FL.
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Progress 02/01/15 to 01/31/16
Outputs
Target Audience:Egg processing industry, egg producers, a wide range of food and food ingredient industry utilizing processed egg products as ingredients in the products, such as bakery, dairy, dressing, confectionery, and meat industry, feed industry, national and international researchers in egg and food science areas, governmental agencies related to egg processing, students in food and poultry sciences, and consumers Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A graduate student was recruited and trained to acquire general lab techniques, sample handling and preparation, and advanced analytical skills required to conduct the project through hands-on practices. The student received general lab safety training. The student acquired proper sample handling and preparation techniques to minimize changes in proteins during storage and sample preparation. The student was trained to acquire knowledge and techniques to perform the analyses to determine physicochemical and functional characteristics of liquid egg white, egg white powder and proteins using various equipment, including pH meter, colorimeter, spectrophotometer, etc. The analytical skill sets to determine functional characteristics of protein-rich sources will be the great assets for the student's future research career in various food industry sectors. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?The analyses for physicochemical and functional properties of spray-dried egg white will be performed to accomplish the objective 1). In order to accomplish the objective 2), functional egg white proteins, including lysozyme, ovomucin, ovotransferrin, and ovalbumin, from liquid egg white and their functionalities as affected by irradiation will be determined. In addition, bioactive peptides will be prepared by enzyme hydrolysis of liquid egg white and separated proteins as above and their bioactivities will be determined. The results will be presented in local, national and international professional conferences and the articles will be prepared and submitted to a peer-reviewed journal.
Impacts
What was accomplished under these goals?
Because of recent consumers' trends to pursue healthy foods and avoid lipids and cholesterols in egg yolk, the demands of processed egg white products by consumers and food industry have continuously increased and will be accelerated in the future. However, highly viscous egg white lowers the yield of egg white at egg breaking plant due to a significant portion of egg white remaining in the shell. Moreover, separated egg white should be homogenized and filtered to make it a uniform, less viscous mixture to accommodate pasteurization and drying processes and facilitate the flow of egg white between processing steps. The homogenization, filtration, and transportation of highly viscous egg white requires excessive energy and costs, and can cause inclusion of oxygen to egg white, resulting in oxidative damages to egg white proteins and their functionalities. Therefore, introduction of the technology to reduce the viscosity of egg white into shell egg processing will provide economical and environmental benefits for the egg processing industry. It has been suggested that irradiation of shell eggs even at a low dose significantly reduces the viscosity of egg white. Hence, irradiation can improve the yield of egg white, eliminate the homogenization and filtration steps that consume energy, time and cost, and facilitate the production of the functional proteins and bioactive peptides. In addition, irradiation of shell eggs can significantly improve the safety of egg white products due to its pasteurization ability without heat. Shell eggs are vulnerable to Salmonella contamination as proven by Salmonella outbreak in 2010. However, the impacts of the low-dose irradiation of shell eggs on physicochemical and functional properties of egg white products and bioactivities of the functional proteins and peptides are not clear. This project will improve understanding of the potentials of the low-dose irradiation of shell eggs as a processing enhancer for the production of processed egg white products and functional proteins and peptides. The objective of the project in this period was to determine the effects of low-dose irradiation at 1 and 2 kGy on the physicochemical and functional properties of liquid and spray-dried egg white (Objective 1). Shell eggs were irradiated in the paper flat at 1 and 2 kGy using electron beam at a commercial food irradiation facility. Because of the height of the shell eggs, they were irradiated twice from top and bottom to achieve the uniform doses. After irradiation, the eggs were transported in iceboxes with ice to the lab. Upon arrival, the eggs were immediately broken and liquid egg white was collected and stored in a 4 °C refrigerator until analysis. Parameters for physicochemical and functional properties of liquid egg white determined were including total solid contents, pH, color, turbidity, protein solubility, protein oxidation, sulfhydryl content, viscosity, foaming capacity and stability, emulsification properties, water holding capacity, gelation property (gel texture), and applicability to angel cake and meat patty. A part of liquid egg white was used for spray-drying to prepare dried egg white power and the powder was stored in a -18 ºC freezer until analyses. Un-irradiated liquid egg white was homogenized before spray-drying while irradiated liquid egg white was not. As expected, irradiation at 1 and 2 kGy significantly decreased the viscosity of liquid egg white by more than half (3.58 and 3.35 mPas, respectively) compared to the un-irradiated (7.31 mPas). Physicochemical properties of liquid egg white irradiated at 1 kGy were not significantly different from those of un-irradiated while those at 2 kGy were significantly but marginally different from those of un-irradiated. The total solid content in irradiated liquid egg white at 2 kGy (15.13%) were significantly higher than that in un-irradiated (13.89%). The pH among the samples ranged between 9.36 and 9.40. As measured using CIE L*a*b* color system (L*: lightness, a*: red/green, b*: yellow/blue), the color characteristics significantly changed by irradiation: a significant increase in L* value at 2 kGy, significant decreases in a* value (greenness) at 1 and 2 kGy, and a significant increase in b* value (yellowness) at 2 kGy. Turbidity of liquid egg white was significantly decreased by irradiation at 2 kGy (abs 0.437) compared to the un-irradiated (0.482). Characteristics of liquid egg white proteins seemed to be affected by irradiation at 2 kGy. Protein solubility (%) of liquid egg white were not changed by irradiation while protein oxidation (nmol carbonyl/mg protein) was significantly increased only by irradiation at 2 kGy (1.88) compared to the un-irradiated (1.14). Surface sulfhydryl contents (µmol sulfhydryl/g protein) were significantly increased by irradiation at 2 kGy (1.70) compared to the un-irradiated liquid egg white and irradiated at 1 kGy (1.25 and 1.20, respectively) while total sulfhydryl contents (µmol sulfhydryl/g protein) increased as irradiation doses increased. These changes in the properties of egg white proteins could affect the functional properties of liquid egg white. Foaming capacity and stability and emulsion stability were significantly improved by irradiation at 1 and 2 kGy while water holding capacity during thermal treatment was decreased by irradiation at 2 kGy. Gel texture properties of liquid egg white was affected by irradiation. Hardness, cohesiveness, resilience, and chewiness of the gel was significantly decreased by irradiation at 1 and 2 kGy compared to the un-irradiated while springiness were not changed. Changes in functional properties in liquid egg white by irradiation indicated that irradiation may cause structural changes in egg white proteins to improve surfactant ability of egg white proteins between two immiscible phases (water/lipid in emulsion and air/water in foam) but adversely affect their thermal binding ability. In application of liquid egg white to angel cake, addition of irradiated liquid egg white affected its volume and texture compared to that of un-irradiated. The volume of the angel cake made of un-irradiated liquid egg white were not different from that of irradiated at 1 kGy, but were significantly higher than that of irradiated at 2 kGy. As irradiation doses for liquid egg white increased, hardness and chewiness of the angel cake increased while its adhesiveness, resilience, cohesiveness, and springiness were not affected. When liquid egg white was applied to beef patties as a binder, cooking yields and color of beef patties were not affected by uses of irradiated or un-irradiated liquid egg white, but their texture properties were affected. Hardness, cohesiveness, and chewiness of the beef patties significantly decreased when irradiated liquid egg white at 1 and 2 kGy was added, while their adhesiveness and springiness did not change. Due to the delay of student recruitment, analyses for the physicochemical and functional properties of spray-dried egg white powder are still on-going and will be done in the early next period. Overall, liquid egg white irradiated at 1 kGy significantly reduced the viscosity of liquid egg white, did not or marginally cause adverse effects on protein and functional properties of liquid egg white, and improve its foaming and emulsion properties. The use of low-dose irradiation at 1 kGy of shell eggs can provide huge economic impacts to the egg processing industry due to the advantages from use of low viscous egg white. The application of irradiation technology to shell eggs will make egg processing more efficient, energy saving, environment friendly, and safer. Therefore, its use will significantly enhance the efficiency, sustainability, profitability, and competitiveness of the egg processing industry and help the industry to reduce its carbon footprint.
Publications
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