Liquid Yolk Research Articles

반응표면 분석법을 이용한 계란 난황 레시틴 분리 최적조건

난황으로부터 레시틴 고함유 인지질을 회수하기 위하여 전처리, 표면반응분석기법을 실시한 결과 난황 인지질 분리조건(난황액 100g 기준)은 알코올 농도 95.83%, 알코올 첨가량 1: 6.51, 균질온도 <TEX>$40.2^{\circ}C$</TEX>, 20,000 rpm에서 5분간 균질한 후 원심 분리하여 여과 후 진공농축하고 아세톤 150 mL로 1회 세척하여 분리한 것으로 수율은 인지질 64.8%이상 레시틴 함량 55.04%의 인지질 분리를 위한 공정을 확립하였다. The optimum conditions for the extraction of lecithin from egg yolk were determined using response surface methodology (RSM). On the basis of the results of preliminary experiments, the most effective values were selected. The effects of three independent variables, dilution ratio, solvent composition, and extraction temperature on the response of crude egg lecithin (g) were then determined. The optimum conditions for egg lecithin separation obtained using ridge analysis were 6.51, 95.83%, and <TEX>$40.2^{\circ}C$</TEX> for the dilution ratio, solvent composition, and extraction temperature, respectively. Using the optimum conditions, 55.04% of crude lecithin in total phospholipid can be obtained from 100 g liquid egg yolk. The experimental values (56.21% crude lecithin in total phospholipid) agreed with the predicted values.

The effect of feeding rosemary, oregano, saffron and &amp;#945-tocopheryl acetate on hen performance and oxidative stability of eggs

In this study the effects of feeding rosemary, oregano, saffron and &#945;-tocopheryl acetate on hen performance and egg quality were investigated. One hundred-twenty Lohmann laying hens, 32 weeks old, were divided into five groups replicated four times with six hens per replicate. One group was given a basal diet and served as control (CON). The experimental diets given to the other four groups were based on the basal diet but contained an additional 200 mg &#945;-tocopheryl acetate/kg (TOC), or rosemary at 5 g/kg diet (ROS), oregano at 5 g/kg diet (ORE) or saffron at 20 mg/kg diet (SAF). At the end of the feeding trial that lasted 56 days, hen performance and some egg quality characteristics were determined, whereas the oxidative stability of the refrigerated stored shell eggs and liquid yolks were also examined. Results showed no significant differences in egg production, feed intake, feed conversion ratio, egg weight and shape, yolk shape, Haugh units and shell thickness among treatments. However, yolk colour was significantly improved in the SAF group compared to all other groups. The extent of lipid oxidation in shell eggs differed among the dietary treatments, but did not change with storage time. In liquid yolk at pH 6.2, lipid oxidation was higher in the CON group compared to all other groups. The ORE group presented lower oxidation rate than the ROS group, but higher than the SAF group, which in turn exhibited higher oxidation rate than the TOC group. When liquid yolk was acidified to pH 4.2, the lipid oxidation profile remained unchanged but the rate was much more intense. Keywords: Rosemary; oregano; saffron; &#945;-tocopherol acetate;egg quality; hen performance; oxidative stability South African Journal of Animal Sciences Vol. 35 (3) 2005: pp.143-151

Use of UV-C radiation as a non-thermal process for liquid egg products (LEP)

The efficacy of short wave ultraviolet light (UV-C) as a non-thermal process for liquid egg products (LEP) was investigated. Non-pathogenic Escherichia coli strain (ATCC 8739), which shows lower sensitivity to UV-C light than E. coli O157:H7 and Salmonella typhimurium, was chosen as a target microorganism. The inactivation of UV resistant strain of E. coli in LEP was examined by evaluating the effects of depth of liquid food medium (0.5, 0.3 and 0.153 cm), UV light intensity (1.314, 0.709 and 0.383 mW/cm 2) and exposure time (0, 5, 10, and 20 min) by using a collimated beam apparatus. The best reduction (>2-log) was achieved in liquid egg white (LEW) when the fluid depth and UV intensity were 0.153 cm and 1.314 mW/cm 2, respectively. Maximum inactivation was 0.675-log CFU/ml in liquid egg yolk (LEY) and 0.316-log CFU/ml in liquid whole egg (LWE) at the same conditions. The kinetics of UV inactivation of E. coli in LEP was nonlinear. Our results emphasize that UV-C radiation can be used as a pre-treatment process or combined with mild heat treatment to reduce the adverse effects of thermal pasteurization of LEP.

Cholesterol removal in liquid egg yolk using high methoxyl pectins

A process to reduce cholesterol in liquid in natura egg yolk using high methoxyl pectins was optimized by response surface methodology aiming to define the maximum level of cholesterol extraction at a minimum decrease of the yolk protein contend. The most important variables influencing the process were dilution level of egg yolk, ionic strength, and pH of yolk suspension, as well as the amount of pectin gel used in the extraction. The fractionary factorial 2 III 4 - 1 was applied in the central composite design to determine the minimum number of experiments to be conducted. The yolk suspension conditions for the optimized process were 5 g of yolk, 31.23 g of water, ionic strength of 0.39 mol/L and pH equal to 9.2 using 5.78 g of pectin gel containing 3% of pectin. The egg yolk contends of cholesterol and protein decreased to 14.4% and 88.6%, respectively.

Changes of hen eggs and their components caused by non-thermal pasteurizing treatments II. Some non-microbiological effects of gamma irradiation or hydrostatic pressure processing on liquid egg white and egg yolk

Experiments were performed to study changes caused by irradiation or high hydrostatic pressure pasteurization of liquid egg white by differential scanning calorimetry, spectrofluorimetry, electronic nose measurements and NIR-spectrometry. The non-thermal pasteurization treatments were also assessed in relation to loss of carotenoid content, and lipid- and cholesterol oxidation of liquid egg yolk. Unlike radiation pasteurization, high pressure processing caused protein denaturation in egg white, which manifested in changes of its DSC-thermogram and intrinsic tryptophan fluorescence. Electronic nose testing showed changes of the head-space volatile composition of egg albumen, particularly as a function of radiation treatment. Both treatments caused changes in the NIR-spectrometric “fingerprint” of the liquid egg white. Various chemometric analyses of the results of the latter instrumental methods, particularly statistical techniques developed by the group of one of the co-authors of this article, demonstrat...

06/01507 Petrology, mineralogy and geochemistry of mined coals, western Venezuela: Hackley, P. C. et al. International Journal of Coal Geology, 2005, 63, (1–2), 68–97

The goal of this study was to develop a general model of inactivation of salmonellae in commercial liquid egg yolk for temperatures ranging from 58 °C to 66 °C by studying the inactivation kinetics of Salmonella in liquid egg yolk. Heat-resistant salmonellae (three serovars of Enteritidis [two of phage type 8 and one PT 13] and one Oranienburg) were grown to stationary phase in Tryptic Soy Broth and concentrated 10-fold by centrifugation. Each inoculum was added to liquid egg yolk and mixed thoroughly, resulting in a final population of ca. 7 log CFU/ml egg yolk. Inoculated yolk was injected into sterile glass capillary tubes, flame-sealed and heated in a water bath at 58, 60, 62, 64, and 66 °C. Capillary tubes were ethanol sanitized, rinsed, and contents were extracted. Yolk was diluted, surface plated onto Tryptic Soy Agar + 0.1% sodium pyruvate and 50 μg/ml nalidixic acid and incubated at 37 °C for 24 h before colonies were enumerated. Decimal reduction values were calculated from survivor curves with a minimum inactivation of 6 log CFU/ml at each temperature. Survival curves (except for 66 °C) featured initial lag periods before first order linear inactivation. Estimated asymptotic D-values were 1.83 min at 58 °C, 0.69 min at 60 °C, 0.26 min at 62 °C, 0.096 min at 64 °C and 0.036 min at 66 °C. The estimate of the asymptotic z-value was ca. 4.7 °C with standard error of 0.07 °C. A linear relationship between the log10 of the lag times and temperature was observed. A general kinetic model of inactivation was developed. The results of the study provide information that can be used by processors to aid in producing safe pasteurized egg yolk products and for satisfying pasteurization performance standards and developing industry guidance.

Synergistic effect of temperature and pulsed electric field on inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in liquid egg yolk

The effects of temperature, treatment time and electric field strength on inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in liquid egg yolk by pulsed electric field (PEF) processing were examined using the reaction kinetics approach. Egg yolk, inoculated with ∼10 8 CFU mL −1 of E. coli O157:H7 or S. enteritidis, was treated in a continuous flow process at 20, 30 and 40 °C in combination with pulsed electric field intensities of 20 and 30 kV cm −1. A biphasic instant reversal PEF waveform with a 2 μs pulse width was used and a maximum of 105 pulses were applied. Increasing the applied electric field intensity, treatment time and process temperature resulted in increased bacterial inactivation. At 30 kV cm −1 and 40 °C, the populations of E. coli O157:H7 and S. enteritidis were reduced by ∼5 logs. The inactivation rate constants increased from 0.004 to 0.098 μ s −1 for S. enteritidis whereas for E. coli O157:H7 the constants increased from 0.009 to 0.039 μs −1 as processing temperature increased from 20 to 40 °C. S. enteritidis was more resistant to PEF inactivation than E. coli O157:H7 at lower processing temperatures.

Effect of Feeding Rosemary and .ALPHA.-Tocopheryl Acetate on Hen Performance and Egg Quality

The goal of this study was to determine the effect of feeding rosemary and α-tocopheryl acetate on hen performance and egg quality. Ninety-six Lohmann laying hens, 32-week-old, were allocated into four groups. One of the groups was given a control diet (CONT), two groups were given diets supplemented with ground rosemary at 5 and 10g/kg (ROS-5 and ROS-10, respectively), whereas the other group a diet supplemented with 200mg/kg α-tocopheryl acetate (VIT-E). Following 60 days feeding, hen performance and some egg quality characteristics were determined, whereas the oxidative stability of the refrigerated stored eggs and liquid yolks was also examined. Results showed that there were no significant (P>0.05) differences in egg production, feed consumption, feed conversion ratio, egg weight and shape, yolk diameter, height and color, Haugh units, and shell thickness, among the dietary treatments. The extent of lipid oxidation in eggs differed (P<0.05) between the dietary treatments, but did not change with the storage time. In liquid yolks, lipid oxidation was lower (P<0.05) in the ROS-5 group compared to the CONT group. The ROS-10 group, in turn, exhibited lower (P<0.05) oxidation rate than the ROS-5 group, a finding suggesting that rosemary exerted a dose dependent antioxidative activity. The VIT-E group presented lower (P<0.05) lipid oxidation rate compared to all other groups.

液卵製造工程のモニタリングによる微生物学的問題点の調査とその改善について

From January to November, 2003, bacterial contamination was surveyed in a small egg-breaking factory that produced non pasteurized liquid egg. Test egg samples were taken at various stages of the egg processing operation. Salmonella Enteritidis was isolated from liquid egg yolk and liquid egg white on October, but was not found in any other samples (50 liquid egg samples, 21 containers and 94 attached production facilities and gloves). The data suggest that the contamination rate (3.8%) is lower than those reported previously. Levels of bacterial standard plate counts, gram-positive bacterial counts and gram-negative bacterial counts were in the ranges of 2 to 5 log CFU/g, 2 to 3 log CFU/g, 2 to 5 log CFU/g, respectively. Liquid egg containers returned from customers was contaminated with bacteria at the level of 8 log CFU per container. However, washing and application of a sanitizer containing sodium hypochlorite reduced the bacterial counts.

Effect of dietary saffron (Crocus sativus L.) on the oxidative stability of egg yolk

1. The effects of dietary inclusion of red stigmas of Greek saffron (Crocus sativus L.) on the oxidative stability of shell eggs and liquid yolks were investigated and compared with those of dietary α-tocopherol. 2. Ninety-six Lohmann laying hens, 38 weeks old, distributed into 4 groups with 4 replicates each, were given either a control diet, diets enriched with 10 (SAF10) or 20 (SAF20) mg/kg saffron, or a diet enriched with 200 mg/kg α-tocopheryl acetate (VE200). 3. Following 6 weeks of feeding, eggs were collected and the rate of lipid oxidation was determined in refrigerated stored shell eggs, as well as in yolks adjusted to a pH of 6·2 or 4·2 and stored in the presence of light. 4. The results showed that the extent of lipid oxidation in shell eggs, as measured by malondialdehyde (MDA) formation, differed between dietary treatments, but did not change with storage time. In stored shell eggs, MDA levels differed between dietary treatments at all time points. 5. Yolks from the control group adjusted to pH 6·2 gave MDA values higher than those of the SAF10 group, which in turn were higher than those of the SAF20 group, a finding suggesting that saffron exerted a dose-dependent antioxidative activity. The VE200 group gave lower MDA values than the other groups at all time points. The oxidation profile of yolks at pH 4·2 showed a similar pattern but the rate of oxidation was greater.

Effect of gamma radiation and cold storage on chemical and organoleptic properties and microbiological status of liquid egg white and yolk

This investigation aims to establish a feasible radiation dose for treating liquid egg white (LEW) and yolk (LEY) at room temperature to improve their microbial safety. Samples of LEW and LEY were subjected to gamma irradiation doses of 0,1,2,3 and 4 kGy at room temperature followed by storage at 4 ± 1 °C. Then the effects of irradiation and cold storage on proximate composition, pH, soluble protein and free sulfhydryl content (SH) were determined for LEW and LEY in addition to the contents of total carotenoids in LEY. Moreover, free fatty acids (FFA) and peroxide value (PV) were determined for lipids of LEY.The microbial safety of LEW and LEY was established during storage throughout the enumeration of the total plate count, enterobacteriaceae, Staphylococcus aureus as well as the detection of Salmonella. The effects of irradiation at 3 kGy dose, which was enough for improving the microbial safety of samples, on amino acid composition of LEW and LEY and fatty acid profiles of LEY lipids were studied. In addition, sensory evaluation was carried out for liquid and scrambled egg white and egg yolk samples. The results showed that gamma irradiation and refrigerated storage had no significant effects on proximate composition and pH of liquid egg samples, while significantly decreased the contents of total carotenoids in LEY samples. Furthermore, gamma irradiation had no significant effects on protein solubility and the contents of free SH in LEW, while induced significant slight decreases in protein solubility and the contents of free SH in LEY. Cold storage, however, showed no significant effects on protein solubility and free SH in all liquid egg samples. FFA contents and PV of LEY lipids significantly increased post irradiation treatments and during storage, but the observed values were relatively low and acceptable. In addition, gamma irradiation at 3 kGy dose had no significant effects neither on the amino acid composition of LEW and LEY nor on fatty acid profiles of LEY lipids. The sensory preference did not alter neither for the liquid egg samples nor for scrambled egg samples that prepared from irradiated liquid egg products. Finally, gamma irradiation at 3 kGy dose appeared to be the optimum for treating LEW and LEY at room temperature followed by cold storage at 4 ± 1 °C.

CONTINUOUS PASTEURIZATION OF EGG YOLK: THERMOPHYSICAL PROPERTIES AND PROCESS SIMULATION

ABSTRACT This article presents empirical correlations to predict the density, specific heat, thermal conductivity and rheological power–law parameters of liquid egg yolk over a temperature range compatible with its industrial thermal processing (0–61C). Moreover, a mathematical model for a pasteurizer that takes into account the spatial variation of the overall heat transfer coefficient throughout the plate heat exchanger is presented, as are two of its simplified forms. The obtained correlations of thermophysical properties are applied for the simulation of the egg yolk pasteurization, and the obtained temperature profiles are used for evaluating the extent of thermal inactivation. A detailed simulation example shows that there is a considerable deviation between the designed level of heat treatment and that this is predicted through process simulation. It is shown that a reliable mathematical model, combined with specialized thermophysical property correlations, provide a more accurate design of the pasteurization equipment that ensures effective inactivation, while preserving nutritional and sensorial characteristics.

Effect of Antioxidants on Cholesterol Oxidation in Spray‐dried Egg Yolk during Extended Ambient Storage

ABSTRACT: Equimolar amounts of butylated hydroxyanisole, ascorbyl palmitate or a tocopherol blend were added to liquid yolk and spray‐dried. One‐g samples were stored in the dark at ambient temperature for 36 mo, then evaluated using gas chromatography. The tocopherol blend and BHA inhibited 7‐ketocholesterol production. No significant differences were observed between the control and the various antioxidant treatments for the production of other cholesterol oxides. In contrast to the results of a previously conducted accelerated study, the added antioxidant levels were insufficient to significantly reduce cholesterol oxidation in spray‐dried egg yolk held for an extended period of time, and additional means of inhibition may be required.

Fracture and textural properties of low fat egg yolk gels containing emulsion droplets

The influence of corn oil content and the type of emulsifier on the fracture and textural properties and the expressible liquid of gels prepared by heat-treatment of low-fat yolk protein concentrate (YPC) containing emulsified oil has been investigated. Oil incorporation in the form of fine droplets results in a decrease of gel network strength, the textural parameter values depending on the amount of added oil. Tween 20 (polyoxyethylene sorbitan monolaurate) when used as the oil emulsifier brings about a reduction in gel textural parameter values compared to liquid egg yolk, the result depending on the emulsion droplet size. Additionally, the gels differ in their yielding behaviour since the latter yield but do not fracture at strain values as high as 0.7 while the former fracture at relatively low strains and their fracture stress and strain parameter values depend on oil droplet size. This behaviour is explained in terms of the effect of the surfactant on the yolk constituents and, particularly, its interactions with the yolk apoproteins, which result in stiffer bulk gel network structure.

Factors Influencing Inactivation of Salmonella Enteritidis in Hard-Cooked Eggs

The inside of a hen's egg, once considered sterile, is now known to occasionally harbor Salmonella Enteritidis. At least two recent outbreaks of salmonellosis in which Salmonella Enteritidis PT34 was involved have been associated with hard-cooked eggs. This study was undertaken to compare D56°C values of Salmonella Senftenberg 775W and six strains of Salmonella Enteritidis isolated from outbreaks associated with eggs. D56°C values for Salmonella Enteritidis in liquid egg yolk ranged from 5.14 to 7.39 min; the D56°C value for Salmonella Senftenberg was 19.96 min. The two PT34 strains from outbreaks associated with hard-cooked eggs did not exhibit significantly higher resistance to heat compared with two PT4 strains and one strain each of PT8 and PT13a. A PT4 strain and a PT34 strain of Salmonella Enteritidis were separately inoculated (107 to 108 CFU) into the yolk of medium and extra large shell eggs at 10 and 21°C, and survival was monitored using two cooking methods: (i) placing eggs in water at 23°C, heating to 100°C, removing from heat, and holding for 15 min (American Egg Board method) and (ii) placing eggs in water at 100°C, then holding for 15 min at this temperature. Within the 15-min holding periods, inactivation was more rapid using the method recommended by the American Egg Board compared with method 2. Within each cooking method, inactivation was most rapid in medium eggs initially at 21°C. The PT4 strain survived in yolk of extra large eggs initially at 10°C when eggs were held in boiling water 9 min using method 2. The final temperature of the yolk in these eggs was 62.3 ± 2°C. Of the two methods evaluated for hard cooking eggs, the American Egg Board method is clearly most effective in killing Salmonella Enteritidis in the yolk.

A simple chemical method for identification of irradiated industrial processed food

The dependence of o- and m-tyrosine levels in protein rich products upon the absorbed radiation dose offers the possibility for identification of radiation processed foodstuffs. A simple and fast method was applied for determining irradiation of industrial processed food. Free amino acids of irradiated and unirradiated liquid egg samples (liquid egg, liquid egg yolk) and homogenized turkey sausage samples were extracted with trichloroacetic acid. After centrifugation and filtration aliquots of the crude extract were applied for HPLC analysis using a RP-C18 column and trichloroacetic acid as ion-pairing agent in combination with an electrochemical dual cell detector. o- and m-Tyrosine were identified by relative retention times and their peak height ratios at different potentials in comparison to those of a standard mixture and quantified by calibration curves. The commercial products investigated were unirradiated.

Effect of electron beam irradiation on physical, physiochemical, and functional properties of liquid egg yolk during frozen storage

Raw yolk of 1-d-old eggs was either subjected to linear electron beam irradiation at approximately 2.5 kGy dosage or not processed. Both irradiated and nonprocessed egg yolk samples were stored at -15 C after irradiation. Testing was conducted on 0, 1, 7, 15, 30, and 60 d of storage. Development of storage modulus (G') was delayed in irradiated samples after 7 d, which suggests that less structure was developed in irradiated egg yolk than in nonprocessed egg yolk during storage. Irradiated samples retained more soluble protein within the first 7 d and showed slightly improved emulsion capacity over that from nonprocessed samples. However, irradiated egg yolk was less bright than nonprocessed samples. No differences were observed in SDS-PAGE patterns of soluble proteins and delipidized low density lipoprotein (LDL). The LDL isolated from irradiated liquid egg yolk showed no difference in N-terminal amino acids compared to that of nonprocessed egg yolk, indicating no detectable cleavage of LDL. However, the denaturation temperature of irradiated samples at Day 0 shifted about 1 C lower than that of the nonprocessed sample. Results indicated that electron beam irradiation did not cause significant physical, chemical or functional changes of egg yolk, or cleavage of egg yolk protein. Therefore, electron beam irradiation could serve as a preservation method for liquid egg yolk.

Effect of Dietary Thyme on the Oxidative Stability of Egg Yolk

The effect of dietary thyme on the oxidative stability of shell eggs over a 60-day refrigerated storage has been evaluated. Also, the influence of dietary thyme and storage time on the oxidative stability of liquid yolks adjusted to various pH values and agitated in the absence or presence of light has been investigated. Yolk lipid oxidation was determined by monitoring malonaldehyde formation through use of third-order derivative spectrophotometry. Results showed that although malonaldehyde is not produced during storage of shell eggs, it is present in the yolk of fresh eggs. It is also evident that thyme treatment reduced oxidation of liquid yolk, which significantly increased with light and increased acidity at pH 3 and declined thereafter as acidity increased to pH 2. A comparative examination of the antioxidant activity of various synthetic and natural antioxidants added to yolk suggested that thymol, the main antioxidant constituent of thyme, cannot be considered totally responsible for the oxidative resistance of the thyme-treated yolk. There may be additional thyme components with antioxidant activity that pass into egg yolk providing antioxidant properties. Keywords: Dietary thyme; yolk stability; lipid oxidation; egg storage; malonaldehyde

Thermal Resistance of Salmonella spp. and Listeria monocytogenes in Liquid Egg Yolk and Egg White

Decimal reduction times (D values) were determined for Salmonella spp. and Listeria monocytogenes (five pooled strains per pathogen) in raw liquid egg yolk (pH 6.3) and liquid egg white (pH 8.2 versus 9.1) by using a low-volume (0.05 ml per sample) immersed sealed-glass capillary-tube procedure. For Salmonella, D values ranged from 0.087 min (at 62.2°C) to 0.28 min (at 60°C) in yolk. and from 1.00 min (at 58.3°C) to 7.99 min (at 55.1° C) in egg white (pH 8.2). For Listeria, D values ranged from 0.58 min (at 62.2°C) to 1.34 min (at 60°C) in yolk, and from 2.41 min (at 58.3°C) to 7.59 min (at 55. 1°C) in egg white (pH 9.1). Mean ZD values for Salmonella ranged from 3.54 to 4.33°C; for Listeria, ZD values ranged from 6.06 to 9.43°C. In egg white, the heat sensitivity of both pathogens was enhanced at pH 9.1, although this trend was more evident for Salmonella spp. than for L. monocytogenes over the temperature range tested. The results indicate that USDA-prescribed minimal pasteurization requirements for liquid egg yolk (equivalent to 3.9- to 22.1-D processes, on the basis of the present study) would be far more lethal to the Salmonella and L. monocytogenes strains tested than would the corresponding thermal processes for liquid egg white (equivalent to 0.7- to 2.2-D processes).

5514401 Supercritical fluid extraction of cholesterol from liquid egg yolk

5514401 Supercritical fluid extraction of cholesterol from liquid egg yolk