Effect of dietary supplementation of gallic acid and linoleic acid mixture or their synthetic salt on egg quality

The effect of a dietary supplementation of gallic acid and linoleic acid mixture (MGL) and their synthetic salt, sodium 2,3-dihydroxy-5-(((9E,12E)-octadeca-9,12-dienyloxy)carbonyl)phenolate (NGL), on egg quality was investigated. A total of 120 laying hens were allotted into five groups over 4 weeks of the experimental period. Birds were fed the following diets: (1) control [commercial diet (CD)], (2) 0.05% MGL (w/w, GA:LA = 1:1, equal molar ratio), (3) 0.1% MGL, (4) 0.05% NGL, (5) 0.1% NGL. The performance of the hen, the anti-oxidative potential of egg albumen and yolk, and the fatty acid composition and cholesterol content of egg yolk were measured. The TBARS value of egg yolk from hens fed 0.1% MGL and 0.05% NGL was lower than that fed control diet after storage for 14 days. The ABTS⁺ reducing activity of egg albumen was significantly improved by MGL and NGL, but only NGL had an effect on yolk (p < 0.05). The dietary supplementation of 0.05% or 0.1% MGL, and 0.05% NGL raised the PUFAs composition in egg yolk. The cholesterol content of egg yolk from hens fed control diet was higher than those fed 0.1% MGL, 0.05% or 0.1% NGL (p < 0.05). In conclusion, a diet consisting of MGL and NGL can improve the antioxidative potential of egg and the fatty acid quality of egg yolk while lowering the cholesterol level.     

Determination of the CO2 mass diffusivity of egg components by finite element model inversion

With the aim to improve the technological properties and the product freshness maintenance, the conservation of eggs in saturated CO₂ atmosphere has been proposed. In this research, to study the CO₂ diffusion inside the egg, a numerical model was developed. This required a characterization of the involved materials, with particular reference to the mass diffusivity. The present paper proposes a method, based on just simple laboratory determination of average total CO₂ concentration and on the inversion of a finite element model, to estimate the CO₂ mass diffusivity in the thin albumen, thick albumen and yolk of hen eggs. The method does not require complex devices and looks susceptible to extension to other physical problems. The results showed that the values of mass diffusivity determined by inverse method (thin albumen: 1.8E−09 m²/s; thick albumen: 8.5E−10 m²/s; yolk: 1.6E−10 m²/s) are comparable to the data reported in the literature for similar materials.The simulated and experimental values of CO₂ concentration appear to be in good agreement, particularly for the albumen.     

MAP storage of shell hen eggs, Part 1: Effect on physico-chemical characteristics of the fresh product

The aim of this study was to compare some physico-chemical properties (O₂ and CO₂ in the package headspace, weight loss, pH, albumen and yolk water content and colour, Haugh unit) of non packed eggs and eggs packed in high barrier plastic pouches with three atmospheres (air, 100% N₂, 100% CO₂) during 28 days of storage at 25 °C. Modified atmosphere packaging (MAP) permitted a strong reduction of the weight loss from the product. While the greatest quality decline was observed for the control eggs (not packed), eggs packed in CO₂ maintained the initial values of Haugh unit during storage and the albumen pH was about 2 units lower than in the control group. Nevertheless, the light yellow colour of CO₂ sample albumen deepened and the shell gradually developed a powdery surface. MAP with 100% N₂ did not promote any additional benefits to the eggs in comparison with the product packed in air.     

Growth of Salmonella serovars in hens’ egg albumen as affected by storage prior to inoculation

Different Salmonella enterica serovars, including Enteritidis, were tested for growth at 20°C in separated albumen upon inoculation with 39 cfu ml⁻¹. The albumen was fresh or stored for up to 3 weeks prior to inoculation (p.i.) either in the shell egg or separated from the yolk. The serovar Enteritidis did not behave differently than the other serovars indicating that the association between human S. Enteritidis infections and eggs is not due to its growth behaviour in albumen. A pronounced growth occurred more frequently and up to a one-log unit higher level in fresh albumen than in albumen stored p.i. This was at least partly explained by a pH effect. Since growth in the separated albumen was similar when the albumen had been stored p.i. in the absence or presence of yolk, we have no indication that nutrients or factors negating the inhibitory properties of the albumen leak out from the yolk during storage. Growth of Salmonella inoculated at a level of 8 cfu in the albumen of fresh and stored whole shell eggs was studied to simulate a more natural situation. In this case, growth also occurred more frequently when inoculated in the albumen of fresh eggs compared to eggs stored p.i. It can be concluded from our study that cooling practices are recommended shortly after lay to prevent Salmonella from growing in eggs.     

The cholesterol content of eggs produced by the Slovenian autochthonous Styrian hen

The cholesterol content of eggs produced by the Slovenian autochthonous Styrian hen in comparison with eggs of the Isa Brown, reared in two different rearing systems, was determined. Eggs were collected four times during the year. The cholesterol content was determined by the enzymatic-spectrophotometric method. The influence of genotype, in two different rearing systems, on the cholesterol content in eggs was studied. The cholesterol content determined in eggs from cages was 13.1 ± 0.43 mg g⁻¹ yolk of the Styrian hens as compared to 11.4 ± 0.49 mg g⁻¹ yolk of Isa Brown hens. The cholesterol content determined in free range eggs was 13.6 ± 0.22 mg g⁻¹ yolk of the Styrian hen and 11.8 ± 0.30 mg g⁻¹ yolk of Isa Brown.     

Quality of eggs coated with oil–chitosan emulsion: Combined effects of emulsifier types,initial albumen quality,and storage

Effects of mineral oil:chitosan (MO:CH at 25:75) emulsions prepared with four different emulsifiers (2 water- and 2 oil-miscible) as coatings on the internal quality (weight loss, Haugh unit, yolk index, and albumen pH) of coated eggs were evaluated during 5 weeks at 25 ± 2 °C and 20 weeks at 4 ± 2 °C. Eggs with two initial albumen qualities [Haugh unit (HU): H = 87.8 and L = 70.9] were used. At 25 ± 2 °C, Haugh unit, yolk index, and albumen pH of all coated eggs decreased with increased storage time. Coated H- and L-eggs maintained an A-grade up to 4 weeks and 1 week, respectively. Weight loss of all coated eggs remained below 1.35% after 5 weeks of storage at 25 ± 2 °C. All coated eggs maintained an A-grade with less than 2.5% weight loss during 20 weeks of storage at 4 ± 2 °C. Emulsifier types marginally affected the internal quality of coated eggs regardless of storage temperatures.     

A market study on the quality characteristics of eggs from different housing systems

To study the differences among commercial eggs from four housing systems i.e. cage, barn, free range and organic, 41 physical and chemical parameters were evaluated on 28 fresh egg samples from the Italian market. The univariate statistic analysis evidenced that organic eggs had the highest whipping capacity and foam consistency but the lowest freshness (the highest air cell height) and albumen quality (the lowest Haugh Unit); cage eggs presented instead the lowest whipping capacity and the highest shell resistance to breaking. The multivariate technique discriminant partial least-squares regression was unable to correctly classify the eggs from the four housing systems but successfully differentiated cage eggs from alternative (organic + barn + free range) eggs. The variables with the most discriminant power were shell breaking resistance, overrun, protein content, and shell thickness.     

A 3-D computational fluid dynamics model for forced air cooling of eggs placed in trays

Freshly laid shell eggs must be cooled quickly for controlling Salmonella Enteritidis (SE) growth. To fulfill a research need identified by Food Safety and Inspection Service (FSIS), a 3-D computational fluid dynamics (CFD) model was developed to predict the temperature of eggs placed on a tray (6 rows × 5 columns) under forced air cooling. The continuity, momentum, and energy equations were solved along with standard k − ε turbulence model using PHOENICS software. The model was validated by conducting experiments in a wind tunnel at various air temperatures (7-11 °C) and velocities (0.3-0.7 m/s). Root mean square error for predicting yolk temperatures was within 1 °C. Finally, the CFD model was integrated with a microbial growth model to estimate the risk of SE growth during cooling. This model can be incorporated into the FSIS risk assessment model for more accurate estimation of SE risk in shell eggs.     

贮藏温度-时间变化对壳蛋新鲜度影响研究

该文以新鲜罗曼粉壳蛋为研究对象,研究5个贮藏温度-时间变化组壳蛋新鲜度指标变化,分别于0、10、20、30 d检测所有实验组壳蛋失重率、气室高度、哈夫单位、蛋黄指数、浓稀蛋白比、蛋清pH。结果表明,贮藏期间壳蛋失重率、气室高度和蛋清pH显著升高（P<0.05）,哈夫单位、蛋黄指数和浓稀蛋白比显著下降（P<0.05）。贮藏20 d时,处理组5壳蛋哈夫单位和蛋黄指数显著高于（P<0.05）对照组1、处理组1、处理组2和处理组3,而失重率、气室高度、蛋清pH较低（P<0.05）。贮藏30 d时,处理组5壳蛋失重率和气室高度显著低于对照组1、处理组1和处理组3（P<0.05）,蛋黄指数显著高于对照组1、处理组2、处理组3、处理组4（P<0.05）。除失重率、哈夫单位外,对照组2与处理组5壳蛋新鲜度指标整体差别不大。因此,除了壳蛋自身品质外,需要尽可能延长低温（4 ℃）贮藏时间,延缓壳蛋新鲜度指标劣变。     

储存温度对鸡蛋微生物及品质的影响

为了解温度对鸡蛋中各组分微生物生长的影响,对鸡蛋在8、10、20、25℃储存30d内的蛋壳、蛋清和蛋黄的细菌总数变化规律做初步研究,并分析储存终点时鸡蛋的气室深度、蛋黄指数、浓蛋白含量、挥发性盐基氮含量品质指标。结果表明：储存温度对鸡蛋各部分细菌总数影响较大。8℃储存30d时蛋壳、蛋清和蛋黄细菌总数分别为3.5×103、2.4×103、1.7×103CFU/g,而25℃储存时则分别达4.6×106、7.5×104、5.3×105CFU/g。8℃和10℃储存10d内,蛋清和蛋黄中均未检测到细菌,25℃储存时则分别在第5天和第10天从蛋清和蛋黄中检测到细菌。鸡蛋各项品质指标的测定结果也表明储存温度越高鸡蛋品质越差。     

Lipid,fatty acid and carotenoid content of edible egg yolks from avian species: A comparative study

A comparative study has been conducted of the major lipid classes composition, as well as the fatty acid and carotenoid content in the yolk of conventional eggs from five avian species (ostrich, turkey, quail, duck and goose); the nutritional indices were calculated. The neutral lipids were the major yolk fractions but their proportions varied among species. All yolks and especially ostrich’s yolk were found to be an excellent source of dietary lecithin. Quail yolk displayed the lowest fat and cholesterol content and the lowest values for the cholesterol index (CI) and cholesterol-saturated fat index (CSI). It is therefore more appropriate for a healthier diet. Turkey and goose yolks contained significantly (P < 0.05) higher ω-3 fatty acid proportion and ω-6/ω-3 ratio. The turkey yolk was characterised by the lowest AI and TI values, which are recommended for a healthy diet. Quail yolk lipids contained a favourable PUFA/SFA ratio. All the examined yolks contained highly bioavailable functional nutrients, such as lutein and zeaxanthin.     

Fatty acid composition of certified organic,conventional and omega-3 eggs

The objective of this study was to compare the fatty acid composition of commercially available conventional, certified organic, and omega-3 eggs. Egg components were assessed, and the fatty acid composition of yolk lipids was determined by gas chromatography. Organic egg yolk contained a higher percentage of palmitic and stearic acids than did conventional yolk (P < 0.05) with no differences observed in the monounsaturated or polyunsaturated fatty acid compositions. Compared with organic and conventional eggs, omega-3 egg yolk contained lower percentages of myristic and palmitic acids, and higher omega-3 fatty acids. In a sub-analysis of conventional egg types, the percent of stearic acid in “cage” egg yolk was significantly lower (P < 0.05) than those of “barn-laid” and “free-range” eggs. “Cage” eggs had a significantly lower percentage (P < 0.05) of arachidonic acid than had “barn-laid” eggs. Consumption of omega-3 eggs has the potential to confer health benefits through the increase in intake of omega-3 fatty acids. With regard to organic or conventional methods of production, the small differences in saturated fatty acids observed in the present study are unlikely to have any significant metabolic effect on the consumer.     

Storage effects on dielectric properties of eggs from 10 to 1800 MHz

ABSTRACT:  The dielectric constant and loss factor of egg albumen and egg yolk over the frequency range from 10 to 1800 MHz were measured at 24 °C at weekly intervals during 5-wk storage at 15 °C. Moisture and ash contents of albumen and yolk, as well as Haugh unit and yolk index, were also measured. The dielectric constant and loss factor of albumen were higher than those of yolk. Linear relationships were evident between the log of frequency, below about 1000 MHz, and the log of loss factor of albumen as well as that of yolk. The dielectric constants of albumen and yolk at 10 MHz were lower than those of fresh albumen and yolk when eggs were stored at 15 °C for 1 wk. However, after 2 wk in storage these dielectric constants rose and remained at higher levels for the rest of the 5-wk period. At frequencies of 100 MHz and higher, the dielectric constant was essentially constant during the entire storage period. Storage had much less influence on the loss factor of either albumen or yolk. In general, the moisture content and ash content of albumen and yolk decreased slightly as eggs aged. The moisture content of yolk increased somewhat with storage, and there was a corresponding decrease in albumen moisture content. The freshness qualities, Haugh unit and yolk index, also decreased as eggs aged. No obvious correlation between dielectric properties and moisture content, ash content, Haugh unit, or yolk index was observed.     

Effect of Storage Conditions on the Quality Attributes of Shell (Table) Eggs

In tropical countries like Nigeria, egg preservation is a serious problem. The common practice is to store under ambient condition due to lack of refrigeration facilities and erratic power supply. Four crates of fresh table eggs were bought from the University of Agriculture, Makurdi farm and preliminary investigations of egg weights, Haugh unit, pH and yolk index were carried out before storage and found to be within standard. Thirty eggs were stored under ambient condition with and without application of oil respectively. The other group of thirty eggs was refrigerated. The initial weights were in the range of 60 – 69 g which reduced drastically. All other quality indices like the Haugh unit, the yolk index and pH declined drastically within the four weeks of the storage especially those that were stored under the ambient conditions. Those stored under refrigeration and those that were oiled and stored under ambient conditions (32 + 2 °C) maintained high quality standards in all the quality indices evaluated. The microbiological result also showed higher bacteria, yeast and mould count on those stored under ambient condition with the initial count of 5.0 × 10³ at first week and 2.8 × 10⁷ at the fourth week while the oiled and refrigerated eggs had values of 5.0 × 10³ at week zero and 7.2 × 10⁴ at week four of storage respectively. It is suggested that application of oil on eggs before storage can be practised to ensure retention of good quality eggs especially in the tropics and most developing nations of the world.     

Assessment of egg freshness by prediction of Haugh unit and albumen pH using an artificial neural network

Eggs are a good source of high quality protein and knowing their quality (physical and chemical properties) during storage is of great importance. Thus, the aim of this research was to design a computer vision system to assess egg freshness during storage time. To this end, 210 intact eggs were collected and stored for 30 days under room conditions (25?±?2 °C and 20?±?3%). After imaging, every other day, some internal and external quality characteristics including yolk height, yolk and albumen pH, yolk and albumen density and Haugh unit (HU) were measured as destructive parameters and area index (D) egg weight as non-destructive parameters. Based on Pearson correlation coefficients, area index were significantly correlated with all destructive variables (p?<?0.05). In order to predict egg freshness, artificial neural network was trained by Levenberg–Marquardt, scaled conjugate gradient, Bayesian regulation, resilient and radial basis algorithms. The best result of artificial neural network for HU and albumen pH prediction was achieved by the Levenberg–Marquardt algorithm with the correlation coefficient of 0.93 and 0.87, respectively.     

鸡蛋内部品质与其呼吸强度的关系

贮藏期鸡蛋品质的变化与呼吸作用息息相关,为了进一步明确鸡蛋内部品质与其呼吸强度之间的关系,本研究选取同一品种的鸡蛋作为实验样本,利用呼吸测定仪测定鸡蛋的二氧化碳呼吸强度,通过SPSS 19.0软件分别分析鸡蛋哈夫单位、蛋白高度、pH值、黏度、蛋黄指数、蛋黄比例以及蛋黄色度与呼吸强度间的关系。结果表明：鸡蛋哈夫单位、蛋白高度及黏度与呼吸强度之间呈极显著正相关（P＜0.01）;pH值与呼吸强度之间呈极显著负相关（P＜0.01）;蛋黄指数、蛋黄色度与呼吸强度之间呈极显著正相关（P＜0.01）;而蛋黄比例与呼吸强度间相关性较小;此外,pH值与黏度、蛋黄指数、蛋黄色度间均存在极显著负相关（P＜0.01）;黏度与蛋黄指数、蛋黄色度之间呈极显著正相关（P＜0.01）;蛋黄比例与其他参数相关性较小。总之,在鸡蛋内部品质参数中,鸡蛋哈夫单位、蛋白高度、蛋黄指数、pH值、黏度及蛋黄色度对呼吸强度影响较大。     

Efficiency of dietary vegetable oils in preserving the quality of shell eggs under ambient tropical conditions

The study evaluates the efficacy of three common market-grade culinary vegetable oils—groundnut oil, cottonseed oil and coconut oil—in preserving the internal quality of freshly laid eggs coated with them and stored under tropical room conditions of 25–32°C and 40–85% r.h. for 36 days. All three vegetable oils significantly (P<0.01) limited diurnal weight losses of the eggs to 0.013–0.016 g as against 0.186 ± 0.013 g for the untreated eggs over 36 days storage. Liquefaction of the yolk and albumen was also significantly reduced (P<0.05) such that the albumen pH of the oiled eggs increased from 7.65 to only 8.35–8.65 after 36 days when the untreated eggs had an albumen pH of 9.80. Subsequently, the yolk index of oiled eggs dropped by only 0.10–0.13 after 36 days and remained significantly superior (P<0.001) to that of the untreated eggs which had dropped from an initial value of 0.47 to 0.11. These preservative effects of the vegetable oils may be attributable to their fatty acid component, rather than their glycerol which showed no significant (P>0.05) improvement over untreated eggs.     

Effects of initial albumen quality and mineral oil–chitosan emulsion coating on internal quality and shelf‐life of eggs during room temperature storage

Effects of mineral oil (MO) and mineral oil–chitosan emulsion (MO:CH = 25:75) as coatings on internal quality and shelf‐life of eggs were evaluated during 5‐week storage at 25 °C. Eggs with three different initial albumen qualities [Haugh unit (HU): H = 87.8, M = 75.6 and L = 70.9] were evaluated. As storage time increased, HU and yolk index values decreased whereas weight loss increased. Coating with MO and/or 25:75 MO:CH emulsion could preserve the internal quality for at least 4 more weeks for H‐eggs and at least 3 more weeks for M and/or L‐eggs, all with weight losses <0.92%. All coated eggs had >70% positive purchase intent, and their colour differences at week 0 could not be detected by naked human eye (ΔE^* < 3.0, noncoated eggs as reference). Consumers significantly differentiated freshly MO‐coated from noncoated eggs on overall surface appearance. This study demonstrated that MO and 25:75 MO:CH emulsion coatings could preserve internal quality and prolong shelf‐life of eggs.     

Influence of curd cutting programme and stirring speed on the prediction of syneresis indices in cheese-making using NIR light backscatter

An NIR reflectance sensor, with a large field of view and a fibre-optic connection to a spectrometer for measuring light backscatter at 980 nm, was used to monitor the syneresis process online during cheese-making with the goal of predicting syneresis indices (curd moisture content, yield of whey and fat losses to whey) over a range of curd cutting programmes and stirring speeds. A series of trials were carried out in an 11 L cheese vat using recombined whole milk. A factorial experimental design consisting of three curd stirring speeds and three cutting programmes, was undertaken. Milk was coagulated under constant conditions and the casein gel was cut when the elastic modulus reached 35 Pa. Among the syneresis indices investigated, the most accurate and most parsimonious multivariate model developed was for predicting yield of whey involving three terms, namely light backscatter, milk fat content and cutting intensity (R² = 0.83, SEy = 6.13 g/100 g), while the best simple model also predicted this syneresis index using the light backscatter alone (R² = 0.80, SEy = 6.53 g/100 g). In this model the main predictor was the light backscatter response from the NIR light back scatter sensor. The sensor also predicted curd moisture with a similar accuracy.     

Determination of cholesterol in Italian chicken eggs

Chicken eggs represent a relevant diet source of cholesterol. With the aim of evaluating the cholesterol content of the eggs from Campania Region (Italy) and to test a new analytical procedure, a sample of 100 chicken eggs from local market was analysed by gas chromatography using a polar capillary column. The total free cholesterol was extracted from the egg yolk with n-hexane and trichloroacetic acid, and analysed without the saponification step commonly used. This alternative procedure was compared with the official method. The results indicate that the total free cholesterol content is in the range of 120-193 mg/egg (average value 157 ± 3 mg/egg) lower than the previously reported value of 213 mg/egg. The total free cholesterol quantity is not related to the yolk weight. The bound cholesterol contribution to the total cholesterol was negligible. Dietary recommendations aimed at restricting the egg consumption should be taken with caution and should not include all individuals.