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Effect of Hens Age and Storage Time on Functional and Physiochemical Properties of Eggs
C 2018 Poultry Science Association Inc.
Agata Marzec,∗,1 Krzysztof Damaziak,† Hanna Kowalska,∗ Julia Riedel,† ‡ Monika Michalczuk,† Ewa Koczywas, Fernando Cisneros,§ Andrzej Lenart,∗ and Jan Niemiec† ∗
University of Life Sciences, 02-786, Warsaw, Poland; Department of Food Engineering and Process Management, Faculty of Food Sciences; † Poultry Breeding Division, Department of Animal Breeding and Production; ‡ DSM Nutritional Products Sp z o.o., 96-320 Mszczonow; and § DSM Nutritional Products A/S P.O. Box 2676, 4002, Basel, Switzerland
Primary Audience: Researchers, Eggs Consumers, Eggs Producer SUMMARY In this study, we aimed to determine the effect of hens age and storage time on the functional and physicochemical properties of eggs. Eggs from hens 25–26, 45–46, 55–56, and 69–70 wk of age were assessed, when fresh (0 d) and after storage 3, 6, and 9 d at 30◦ C and at 50% humidity. As hens age and storage time progressed, albumen height, Haugh unit (HU) score, yolk index (YI), and vitelline membrane strength (force breaking and elasticity) significantly decreased. The values of albumen height, HU, and YI were found to be higher in eggs obtained from the younger hens (25–26 wk of age) than those from the older hens. A significant effect of hens age was also found on the yolk pH and water activity. There was no statistical difference observed between the analyzed parameters of eggs from older hens (45–70 wk of age). There was no effect of hens age on the egg quality that was found to be the best when fresh. Interaction between hens age and the storage time also had significant impact on egg weight, albumen height, HU, yolk pH and YI, yolk weight, yolk ratio, and water activity. HU and YI scores were found to be greatly influenced by the age of hens and storage time of eggs. Changes of egg quality from the younger and older hens during storage have proceeded similarly, but eggs from older hens had significantly higher eggs weight and yolk weight that changed slowly. Key words: egg quality, Haugh unit, yolk index, force breaking 2018 J. Appl. Poult. Res. 0:1–11 http://dx.doi.org/10.3382/japr/pfy069
DESCRIPTION OF THE PROBLEM Monitoring of egg quality is important from an economic point of view. Of particular importance for egg producers is the quality of the shell, whereas for the processors and culinary pro1
Corresponding author: agata [email protected]
fessionals, the functional and physicochemical properties of eggs are important that indicate freshness and quality. The diet of hens plays a significant role in the external and internal egg quality; however, the storage conditions also affect egg quality. In addition, egg quality is influenced by various genetic factors [1] as well as environmental factors such as temperature and
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Effect of Hens Age and Storage Time on Functional and Physiochemical Properties of Eggs
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When the vitelline membrane weakens or breaks, these nutrients can contaminate the albumen and possibly inhibit its antimicrobial properties or allow bacteria to penetrate the yolk [14–16]. Vitelline membrane strength is important for egg breaking when separating the yolk from albumen as to reduce yolk contamination of the albumen. Physicochemical transformation of egg content reflects the aging process of egg. The egg quality, and thus its culinary and processing values, can be determined by measuring the physicochemical changes. Therefore, in this study, we aimed to evaluate the effects of hens age and storage time on the functional and physicochemical properties of eggs.
MATERIALS AND METHODS The experiment was conducted at the RZD Wilan´ow experimental station belonging to the Warsaw University of Life Sciences, Poland. The hens were kept in the commercial production, and supplements used in the experiment were recorded in the Register of Animal Feed Commission at the Ministry of Science and Higher Education Poland. According to the Council Directive 70/524/EEC, canthaxanthin has been authorized to be used up to 80 mg/kg in the diet laying hens. According to the EU Commission (2005) regulation 1459/2005, the permitted levels of iodine for laying hens range from 5 to 10 mg/kg of the feed (12% of humidity) [17, 18]. According to the Act of 22 July 2003 on experiments with animals [19], the production was not an experimental procedure and therefore did not require application to and consent of the National Ethical Commission at the Ministry of Science and Higher Education in Poland. Birds and Their Treatment A total of 300 ISA Brown laying hens (age 18 wk) used in this study were bought at the Musielak, Specialist Poultry Farm, Limited Company, Złotokłos, Poland. All birds were under veterinary control during the rearing and the laying periods. Lighting program and temperature in the building were consistent with the ISA Brown Management Guide [20]. The birds received the same feed. The laying performance
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storage humidity [2]. The process aging of egg influenced by the storage conditions has been studied previously in detail [3, 4]. The hens age influences the egg weight (EW) and shell quality [3, 5–7]. Albumen height and Haugh unit (HU) score are important indicators of egg quality; HU is a logarithmic function of height of thick albumen adjusted for EW [8]. Determining the HU score is a common way to assess the egg’s internal quality. Albumen quality constitutes a standard measure of egg quality testing and is of significance for both the processing industry and the consumer. Silversides and Scott [9] demonstrated that albumen height decreases with hen age, even if EW and the total albumen content in the egg increases in fresh eggs. Silversides and Villeneuve [10] reported that pH is a useful indicator of changes in albumen quality over time during storage. Significant increases in yolk pH were observed with increasing storage time [2]. Furthermore, hen’s age is the most important factor affecting the egg quality. Albumen quality decreases rapidly with advancing hens age [11]. Most of the changes in egg quality are measured in terms of HU score, albumen height, albumen pH, yolk index (YI), and EW and yolk weight (YW). Moreover, size of air cell increases with a loss in moisture content due to evaporation through the pores of the shell and the escape of carbon dioxide (CO2 ) from the albumen [12]. Thus, water activity (aw ) of albumen and yolk may also be an important indicator of egg quality. Water activity assumes values from 1 for clean water to 0 for the environment without water or where water molecules are unable to perform their activity. From the practical point of view, water activity means the amount of water available for the growth of microorganisms and activity of enzymes and other chemical changes that may take place in the food [13]. Both storage conditions and storage time may significantly affect the water activity of albumen and yolk, thus influencing the stability and quality of egg’s contents. The vitelline membrane, which surrounds the yolk, is responsible for keeping the yolk content separate from the albumen. Determining the strength of vitelline membrane is important because a strong vitelline membrane prevents components of the yolk from diffusing into the albumen. The yolk contains nutrients that are good for the growth of bacteria.
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MARZEC ET AL.: HENS AGE AND STORED EGGS
Storage of Eggs Eggs from 25–26, 45–46, 55–56, and 69–70 wk of hens age were collected. Approximately 500 eggs were collected each time and were kept in storage chamber [22] at 30◦ C and 50% humidity during 3, 6, and 9 d. Analysis of Egg Quality Quality assessments were performed 4 times: on the day of laying (fresh eggs) and after 3, 6, and 9 d of storage, each time with 120 eggs per group. Eggs were analyzed using the ORKA Food Technology Egg Analyzer device [23], which determines EW (±0.1 g), height of thick albumen (mm), yolk weight (YW) (±0.1 g), and yolk color. Albumen height was expressed as height of thick albumen (mm) and in terms of HU score, which were automatically calculated from the measurements (on a scale of 0–130) by the device.
Table 1. Composition and Nutrients of Experimental Diets. Feed composition Wheat Yellow corn, 8.5% Soybean meal, E46% Uz Sunflower meal, O/C 36% Wheat bran, 16% Limestone, 38% Monocalcium phosphate Salt Sodium bicarbonate Sunflower oil DL Methionine Lysine HCL 1 Premix Nutrient ME Kcal/kg Crude protein g/kg Crude fat g/kg Crude fiber g/kg Calcium g/kg Available phosphorus g/kg Cys.+ Met g/kg Lysine g/kg Methionine g/kg Choline mg/kg Linoleic acid g/kg
5.00 56.17 13.82 8.00 5.85 8.08 0.51 0.22 0.10 1.00 0.15 0.12 1.00 2649.99 160.00 42.13 44.86 37.00 3.40 7.00 7.60 4.15 945.93 20.09
Supplementation per kg of premix: manganese 6,000 mg, zinc 6,000 mg, iron 6,000 mg, copper 800 mg, iodine 100 mg (according to treatment group), selenium 25 mg, vitamin A 1,000,000 IU, vitamin D3 300,000 IU, vitamin E 3,000 mg, vitamin K 250 mg, vitamin B1 250 mg, vitamin B2 250 mg, vitamin B6 350 mg, vitamin B12 1.5 mg, nicotinic acid 3,000 mg, panthotenic acid 800 mg, folic acid 100 mg, biotin 10 mg, canthaxanthin 3,000 mg, and phytase 60,000 FT.
Yolk ratio (YR) is expressed as the ratio of YW to EW (%). YI was determined by measuring the width of the yolk with dial calipers and the height of the yolk using a standard tripod micrometer (accuracy 0.01 mm). The yolks were measured in their natural position in the egg, and YI was calculated according to the following formula [24]: Yolk Index =
yolk height × 2 yolk width 1 + yolk width 2
Albumen was separated from the egg. Vitelline membrane strength was measured using the TA.HDPlus Texture Analyzer [25] with a 5-kg load cell and a sensitivity of 0.1 g. Compression tests were performed on egg yolks by
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of hens was controlled for 46 wk, that is, from the 23rd to 69th wk of age. The laying hens were kept in a 3-level cage battery with 30 cages total, 10 hens per each cage. The cages [21] had the following dimensions: width of 120 cm, depth 126 cm, and a minimum height 45 cm (910 cm2 /hen). They contained a scratchpad area (2 × 900 cm2 ), perch areas of 20 cm/hen, and 2 nests of 1,200 cm2 ; the floor gradient was 7.7◦ . The nesting area was separated by a red curtain composed of plastic strips. At the16th wk of age, light stimulation was started by extending day length for 2 h followed by extensions of 1 h/wk until it reached 16-h light exposure. The 16-h light stimulation was continued till the end of the experiment. Throughout the experiment, the average room temperature was maintained at 18 ± 2◦ C. Water was available ad libitum from 2 nipple drinkers in each cage. Experimental diets were limited to 114 g/hen/d and were administered twice a day (in portions 57 g each) after switching on the light and in the eighth hour of the day, through 240 cm long feeders (20 cm/hen). From the 18th wk of age onward, the hens were fed with feed mixtures (experimental diets) as shown in Table 1.
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Statistical Analysis Data were analyzed using the general linear model (GLM) procedures of Statistic 12PL. Factorial arrangement of hens age (W) and storage time of eggs (T) and respective interactions to assess the effect on functional and physiochemical properties of eggs were used. All statements of statistical significance were based on P < 0.05. Data were subjected to ANOVA using the procedure of GLM: Yi j = μ + Wi + T j + (W T )i j + ei jk where Yij is a variable: μ is the general mean; Wi is the week of hens age, i = 25–26, 45–46, 55– 56, and 69–70 wk of hens age; Tj is the storage time, j = 0, 3, 6, and 9; (WT)ij is the interaction of age × storage time; and eijk is the random error. The model a multiple linear regression was used to describe the hens age and shelf weeks on the HU and YI score: Y = b0 + b1 W + b2 T ± e where Y is the HU or YI; b0 , b1 ,, and b2 are the regression coefficients; W is the week of hens age; T is the storage time; andε
analyzed variables was assessed with the help of PCA. This analysis allows the possibility to observe similarities and differences between the study groups [29].
RESULTS AND DISCUSSION Effect of Hens Age Tables 2 and 3 present the effects of hens age on the functional and physicochemical properties of eggs. The hens age significantly affected all tested parameters except for the albumen aw (P = 0.775), color (P = 0.829), and elasticity of vitelline membrane (P = 0.080) of yolk. The average value of EW from the younger hens (25–26 wk of age) was around 54 g, which was found to be statistically lower than eggs from older hens (61 g, 45–70 wk of age) (P < 0.001) (Table 2). Hens age is a factor that affects the value of EW [7, 30]. Several research studies have shown that eggs from older hens are heavier than those obtained from younger ones [8, 9, 31–33]. On the contrary, Zemkov´a et al. [34] showed that the age of hens has no significant influence on EW. In this study, we found significant influence (P < 0.001) of hens age on the values of albumen height and HU. Both these parameters were found to be significantly higher in case of eggs obtained from younger hens (25–26 wk of age) than those obtained from older hens. Albumen height and HU score were found to be higher in case of eggs obtained from the younger hens (25–26 wk of age) than from the older hens by approximately 22%. Our results demonstrated that older hens had greater YW and YR values (22 and 13%, respectively) than that of younger hens (Table 3). The relationship is consistent with that described in the literature [32–37]. In this study, lowest YW and YR were found in case of younger hens at 25–26 wk of age than that of older hens at 45–70 wk of age (Table 3). Zita et al. [30] confirmed that YW and YR significantly increased with the hens age, which agrees with our results. It was found that the hens’ age had an effect on the increase EW, YW, and YR [38]. YI was found to be 0.342 for eggs from younger hens (25–26 wk of age) and 0.315 from older hens (45–70 wk of age) (Table 3). This means that eggs from
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a cylindrical probe with a diameter of 100 mm and with an applied compression rate of 1 mm/s to obtain 300 g of force. Vitelline membrane strength was shown in terms of breaking force (g) and elasticity (mm). Egg yolk color was visually measured using a YolkFanTM [26], which is an industrial color scale varying from 1 (pale yellow) to 16 (dark orange). Albumen and yolk pH were separately measured using a pH meter with glass electrode IJ44C [27]. Albumen and yolk water activity (aw ) were measured using the AquaLab Model CX-2 [28] at 30◦ C.
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Table 2. Effect of Hens Age and Eggs Storage Time on Functional and Physicochemical Properties of Eggs Albumen.1 Albumen
25–26
Storage time (d)
EW2 (g)
Height (mm)
Haugh unit
pH
aw 3
0 3 6 9
57.93 53.43 53.85 52.62 0.29 <0.001 62.67 60.87 60.22 58.44 0.36 <0.001 64.23 62.19 62.22 60.23 0.32 <0.001 62.34 61.19 60.93 60.31 0.32 <0.001
8.75 5.04 4.10 3.74 0.08 <0.001 7.06 4.07 2.97 2.73 0.07 <0.001 7.27 3.99 3.09 2.56 0.08 <0.001 6.86 3.83 3.08 2.58 0.07 <0.001
93.52 71.44 62.30 59.39 0.63 <0.001 83.18 58.16 43.69 42.07 0.76 <0.001 83.74 56.35 44.37 36.72 0.85 <0.001 81.39 54.74 45.25 37.55 0.89 <0.001
7.8 8.8 9.1 9.1 0.04 <0.001 8.1 9.2 9.4 9.4 0.03 <0.001 8.2 9.2 9.3 9.4 0.02 <0.001 8.2 9.1 9.3 9.4 0.03 <0.001
0.989 0.993 0.992 0.990 0.0005 0.403 0.990 0.990 0.990 0.991 0.0006 0.850 0.990 0.992 0.992 0.992 0.0003 0.250 0.990 0.992 0.992 0.991 0.0005 0.728
0.14 0.24 0.24 0.002 0.003 0.023
0.08 0.04 0.06 <0.001 <0.001 <0.001
0.65 0.22 0.60 <0.001 <0.001 <0.001
0.01 0.01 0.02 <0.001 <0.001 <0.001
0.0004 0.0004 0.0007 0.775 0.072 0.724
SEM P-value 45–46
0 3 6 9 SEM P-value
55–56
0 3 6 9 SEM P-value
69–70
0 3 6 9 SEM P-value
Source of variation SEM Weeks of age Storage time Weeks of age × storage time P-value Week of age Storage time Weeks of age × storage time Values are means for 120 eggs in each parameter. 2 EW = egg weight. 3 aw = water activity.
both younger and older hens were characterized by acceptable quality to consumers. The hens age had a significant impact (P < 0.001) on the value of YI (Table 3). The value of YI from the younger hens was found to be about 8% higher than that of older hens. The yolk color is an important parameter for the consumer. Although preferences vary, consumers in most countries prefer an egg yolk color with a DSM YolkFanTM value of 12 or more [26]. The hens age was also not found to affect the yolk color (Table 3). Yolk color was found to be stable and did not change with the hens age from 25 to 70 wk (Table 3). Probably, the
observed higher values of yolk color were due to diet of hens. Vitelline membrane strength was evaluated on the basis of its breaking force and elasticity. Elasticity is the distance from the point of the membrane deformation to its breaking. There were no significant (P = 0.08) differences between the elasticity of the membrane depending on the hens age (Table 3). The highest breaking force (274 g) was observed at 25–26 wk of hens age. The vitelline membrane of the yolk from older hens (45–70 wk of age) was weaker (18%); the difference was significant in relation to the hens at 25–26 wk of age (Table 3).
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Weeks of age
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Table 3. Effect of Hens Age and Eggs Storage Time on Functional and Physicochemical Properties of Eggs Yolk.1 Weeks of age
Storage time (d)
Yolk Ratio2 (%)
SEM P-value
13.89 13.09 13.77 14.01 0.09 <0.001 16.94 17.83 17.33 17.93 0.13 <0.001 17.23 17.63 18.76 18.93 0.13 <0.001 16.62 17.82 18.34 18.65 0.13 <0.001
23.99 24.54 25.62 26.67 0.16 <0.001 27.08 29.37 28.81 30.72 0.19 <0.001 26.88 28.38 30.20 31.46 0.21 <0.001 26.72 29.16 30.15 30.97 0.21 <0.001
0.416 9.55 0.374 8.76 0.314 9.03 0.262 9.17 0.002 0.27 <0.001 0.220 0.386 9.61 0.350 8.98 0.270 9.03 0.238 9.59 0.003 0.291 <0.001 0.390 0.379 9.90 0.333 9.59 0.295 9.62 0.214 10.22 0.003 0.21 <0.001 0.142 0.382 9.88 0.344 9.65 0.288 9.44 0.247 9.78 0.003 0.26 <0.001 0.668
Source of variation SEM Weeks of age Storage time Weeks of age × storage time P-value Weeks of age Storage time Weeks of age × storage time
0.08 0.16 0.02 <0.001 <0.001 <0.001
0.08 0.08 0.15 <0.001 <0.001 <0.001
<0.001 <0.001 0.002 <0.001 <0.001 <0.001
25–26
0 3 6 9 SEM P-value
45–46
0 3 6 9 SEM P-value
55–56
0 3 6 9 SEM P-value
69–70
0 3 6 9
Index
Force Color breaking (g)
0.11 0.11 0.19 0.829 0.905 0.944
Elasticity (mm)
pH
273.96 232.22 211.81 207.29 4.50 <0.001 246.94 197.58 168.80 148.49 4.07 <0.001 254.01 193.14 171.82 153.94 3.91 <0.001 237.87 195.90 171.01 145.84 4.03 <0.001
9.11 7.48 6.43 5.44 0.08 <0.001 9.00 7.41 5.83 4.90 0.06 <0.001 9.09 7.49 6.19 4.97 0.06 <0.001 8.90 7.89 6.24 5.28 0.10 <0.001
5.6 5.5 5.7 5.7 0.01 <0.001 6.1 6.2 6.2 6.2 0.06 <0.001 6.1 6.1 6.2 6.2 0.05 <0.001 6.1 6.1 6.2 6.2 0.05 <0.001
0.986 0.987 0.988 0.986 0.0003 <0.001 0.984 0.986 0.985 0.987 0.0003 <0.001 0.983 0.988 0.988 0.988 0.0004 0.025 0.986 0.989 0.989 0.990 0.0004 <0.001
1.81 1.81 3.13 <0.001 <0.001 0.161
0.04 0.06 0.06 0.080 <0.001 <0.001
0.02 0.03 0.05 <0.001 <0.001 <0.001
0.03 0.03 0.05 <0.001 <0.001 <0.001
aw 3
Values are means for 120 eggs in each parameter. 2 Yolk weight ratio to egg weight (%). 3 aw = water activity.
In this study, yolk pH (from hens 25–26 wk of age) was about 5.6; however, in eggs from older hens (45–70 wk of age) yolk pH was about 6.1, which is significantly higher than in the case of younger hens (P < 0.001) (Table 3). Yolk aw of eggs from hens at 25–46 wk of age was about 0.986. However, eggs from older hens (55–70 wk of age) had yolk aw about 0.988. Observed differences in yolk aw were found to be significant (P < 0.001) (Table 3). At the same time, there were no differences in yolk pH from hens at 45– 70 wk of age as well as in yolk aw from hens at 55–70 wk of age. Effect of Storage Time of Eggs As in the case of hen aging, the prolonged storage time of eggs significantly affected the
deterioration of the parameters of most of the analyzed albumen parameters (Table 2) and egg yolk (Table 3). The storage time of eggs did not impact the albumen aw (P = 0.072) and yolk color (P = 0.905). HU score was found to be decreased by about 22 and 47% after 3 and 9 d of storage, respectively. Albumen height was found to be decreased by about 61% after 9 d of storage (Table 2). Scientists have reported that albumen height and the HU score value are equally indicators of albumen quality [10, 14], which is similar to our results. It is assumed that higher the value of HU, the better is egg quality [2, 5]. There are many studies describing the influence of storage time and temperature on HU [2, 6, 39]. Determining HU score to assess the egg’s interior quality [8] has been accepted by the USDA Agricultural Marketing Service as a
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Weight (g)
MARZEC ET AL.: HENS AGE AND STORED EGGS
the measured breaking force are characterized by considerable standard deviation [46]. Interaction of Hens Age and Storage Time of Eggs The significant interaction of hens age and storage time of eggs was confirmed for height, HU, and albumen pH (Table 2), and the most parameters of yolk except for color and breaking force of VM (Table 3). The results of this study showed that all the tested parameters of egg quality showed that hens age and storage time caused considerable changes in the values of HU and YI. These changes have been explained mathematically using the regression equation. Table 4 presents the model and coefficients of regression equation. According to the regression equation, the expected values for HU and YI were found to be 98.55 and 0.426, respectively. The HU and YI values expected through estimation differ from the real (empirical) values on average by 10.82 (HU) and 0.035 units (YI), respectively. The value of HU was found to be decreased by a mean of 0.380 units in albumen from older hens and by 4.52 units with the prolongation of the storage time. Furthermore, changes were observed in case of values of YI, which was found to be decreased with the hens age yet on average by 0.001 and approximately by 0.017 with the storage time (Table 4). Our analysis demonstrates that YI is a more sensitive parameter describing the quality of egg than that of HU score. In addition, the determination factor (R2) for HU is lower than that of YI. This means that the proposed linear model describes variability in 69.3% HU and in 73.2% YI according to the age of hens and storage time (Table 4). Principal Component Analysis PCA was conducted, allowing for a reduction of analyzed parameters and grouping eggs with similar quality. For the analysis of PCA, 10 parameters were considered: vitelline membrane strength (breaking force and elasticity), EW, albumen height, HU, YW, YR, YI, albumen pH, and yolk aw . PCA reduces the number of parameters from 10 to 2 (PC1 and PC2) (Figure 1). Component PC1 was positively correlated with albumen height, HU score, vitelline
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reliable method [40]. Furthermore, albumen pH in case of younger hens (24–25 wk of age) was found to be 7.8, which was found to be significantly lower than that of older hens (pH = 8.2; 45–70 wk of age) (Table 2). However, there was no difference between the albumen pH evaluated from older hens (45–70 wk of age) (Table 2). During storage there was an increase in the value of albumen pH (Table 2). Egg albumen releases CO2 originating from the carbonic acid dissociation, forming a buffer system within albumen. The process is followed by alkalization, demonstrated by an increase of albumen pH [41]. Alkalization within the egg causes changes in the structure of albumen. Numerous authors confirm the relationship between the storage time of eggs and the increase in albumen pH [42–44]. Usually, the quality of yolk is given by YW, YR, and YI. Our results confirmed a significant of storage time on the values of YW and YR (P < 0.001) (Table 3). YW was found to be increased by about 5 and 9% after 3 and 9 d of storage, respectively. Extension of the storage time caused a decrease in the value YI, which dramatically decreased by 10% after 3 d and 37% after 9 d of storage (Table 3). Statistical analysis showed that the storage time of eggs had significant influence on the vitelline membrane strength (breaking force and elasticity). After 3 d of storage, the breaking force decreased by approximately 20%, and after 9 d it decreased by approximately 34%. In case of elasticity, the decrease amounted to approximately 17% after 3 d of storage, but after 9 d, it was found to by approximately 43% (Table 3). According to Berardinelli et al. [45], the rupture energy and the maximum force, obtained by driving a probe with diameter of 2 mm into the highest point of the yolk, significantly decreased by about 40% after 3 d of storage at 20◦ C. Caudill et al. [14] stated that the vitelline membrane strength, along with the HU, constitutes another important parameter of egg quality. It should be emphasized that in practice the evaluation of vitelline membrane strength is a difficult task, requiring a strength-measuring device (texture analyzes) with appropriate sensitivity. Moreover, selection of the proper deformation probe and finding the rate of destruction is necessary in such a study. Due to the heterogeneity of the vitelline membrane, the mean values of
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Table 4. Regression Analysis Coefficient and Model of Hens Age and Eggs Storage Time. N = 1920
Significance directivity factor
HU
∗
b1
b2
ε
R2
−0.380
−4.528
10.821
0.697
Weeks of age Storage time
−0.316 −0.773∗
98.553
Weeks of age Storage time
−0.151∗ −0.842∗
0.426
Model Yolk index Model ∗
HU = –0.38 (W) -4.53 (T) + 98.55 ± 10.82 −0.001 −0.017 0.035 0.732
YI = –0.001 (W) – 0.017 (T) + 0.426 ± 0.035
Significant values.
Figure 1. PCA diagram. The effect of hens age and storage time on the functional and physicochemical properties of eggs. Hens age 25–26 wk: A – 0 fresh, B – 3 d, C – 6 and 9 d eggs storage time. Hens age 45–46, 55–56, 69–70 wk: D – 0 fresh, E – 3 d, F – 6 and 9 d eggs storage time.
membrane strength (breaking force, elasticity), but YI correlation with YR, albumen pH, and yolk aw was negative. PC1 explains 70.7% of the variability of the studied traits. PC2 was positively correlated with EW and YW, and explains 20.5% of the variance. The loss of information on reduction in parameters was found to be minor, which amounted to 8.8%. Table 5 presents correlation parameters with PC1 and PC2 components.
The fresh and stored eggs from younger and older hens were more or less grouped according to their preparation procedure in the space for PC1 and PC2 components (Figure 1). Egg quality deteriorated with the hens age and storage time. The examined eggs were assigned to 6 groups (A, B, C, D, E, and F) differing in PC1 and PC2 components. Fresh eggs from the younger hens (25–26 wk of age) (group A) were located on the right side of the
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b0
MARZEC ET AL.: HENS AGE AND STORED EGGS Table 5. Correlation Between PC1, PC2, and Egg Quality Parameters. Parameters
PC1
PC2
0.97 1.00 − 0.01 0.99 0.91 0.92 − 0.62 − 0.87 − 0.94 − 0.68
0.16 0.02 0.99 − 0.04 0.35 0.17 0.79 0.46 − 0.20 − 0.16
diagram and possessed the highest values of PC1 component (Figure 1) meaning that they had the highest values of albumen height, HU, YI, vitelline membrane strength, and lower values of albumen pH and yolk aw (Tables 2 and 3). Fresh eggs from older hens (45–46, 55–56, and 69– 70 wk of age—group D) had similar quality parameters, and they were characterized by smaller PC1 and larger PC2 component than eggs from younger hens (25–26 wk of age—group A). PCA suggested that better fresh egg quality (groups A and D) was associated with PC1 component (YI, breaking force and elasticity of vitelline membrane, HU, and albumen height) (Figure 1). PCA diagram clearly shows that fresh eggs from older hens (group D) had the quality parameters (PC1) only slightly worse than eggs form younger hens (group A). But group D had higher PC2 component (EW and YW) than group A. However, regarding hens age, eggs from older hens had faster degradation of egg quality from storage 3 to 9 d (groups E and F in opposition to groups B and C). During storage, PC1 component was found to decrease in case of eggs from older hens (45–70 wk of age), whereas PC2 component did not change. Poor egg quality was due to the increase in albumen pH and yolk aw . There were no differences with respect to egg quality parameters between eggs stored for 6 and 9 d (group F). The difference between eggs from the younger (groups A, B, and C) and older hens (groups D, E, and F) is mainly due to the increase in PC2 component (increase EW and YW in older hens). However, eggs from the younger hens had lower PC2 component than eggs from older hens, which was in terms of lower EW and YR. Eggs from the oldest hens (69–70 wk of age) had the same quality as eggs from younger hens (45–46 and 55–56 wk of age).
Regarding storage time, eggs from older hens had greater degradation in egg quality after 3 d of storage (groups E and F), as already observed for eggs from younger hens (groups B and C). Eggs from the younger hens stored at 6 and 9 d (group C) had the same PC1 component, which is similar to the eggs from older hens stored at 3 d (group E). This means that stored eggs from the younger hens retained good quality for longer time than stored eggs from older hens. The storage time of 3, 6, and 9 d had a strong impact on PC2 component from the younger hens (samples were distributed in the lower portion of the diagram) (Figure 1). EW and YW were considerably decreased (Tables 2 and 3). Eggs from the younger hens (25–26 wk of age) after 3, 6, and 9 d of storage were also characterized by lower PC1 component than that of fresh eggs. In case of eggs from older hens (45–46, 55– 56, and 69–70 wk of age), PC1 component decreased after 3, 6, and 9 d of storage (samples distributed on the left side of the diagram). However, PC2 component was less affected by the storage time. This means that eggs from older hens are less susceptible to the changes in EW and YW. Thus, HU and YI parameters with a strong correlation to PC1 appear to be good parameters of egg quality evaluation (Table 5). Furthermore, the egg quality parameters strongly correlated with other (Table 6). Statistical analysis (correlation matrix) based on hens age and storage time of eggs showed that force and elasticity are positively correlated with albumen height, whereas HU and YI and force and elasticity are negatively correlated with the YW, YR, albumen pH, and yolk aw (Figure 1, Table 6). As storage time progressed, the average values of yolk pH increased after 6 d of storage (Table 3). Yolk aw of fresh eggs was found to be significantly lower than that of stored eggs (Table 3). The change in aw during storage is caused by the diffusion of water from the albumen to the egg yolk. Differences among the yolk aw in eggs stored for 3, 6, and 9 d were not found (Table 3).
CONCLUSIONS AND APPLICATIONS 1. Hens age influences the strength of the vitelline membrane (breaking force), EW,
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Albumen height (mm) Haugh unit Egg weight (g) Force breaking (g) Elasticity (mm) Yolk index Yolk weight (g) Yolk ratio (%) Albumen pH Yolk water activity
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10 Table 6. Correlation Between Functional and Physicochemical Properties of Eggs. Egg weight 0.137
Haugh unit
Albumen Albumen pH aw
Yolk weight
Yolk ratio
Yolk index
Force breaking Elasticity
1.000
− 0.002 − 0.162
0.975∗ 1.000 − 0.975∗ − 0.938∗
1.000
− 0.037
− 0.219∗ − 0.191
0.213∗
1.000
0.415∗
0.075
0.756∗ − 0.460∗ − 0.585∗
0.379∗ − 0.739∗ − 0.820∗ 0.692∗ 0.127 0.895∗ − 0.825∗ − 0.098 0.151 0.871∗ 0.927∗ − 0.859∗ − 0.172 − 0.012 0.897∗
1.000 0.892∗ − 0.423∗ − 0.578∗
1.000 − 0.703∗ − 0.806∗
1.000 0.851∗
1.000
0.890∗ 0.885∗ − 0.862∗ − 0.132 − 0.276∗∗ − 0.616∗ 0.955∗ 0.869∗ 1.000 0.328∗ 0.381∗ 0.033 0.955∗ 0.838∗ − 0.406∗ − 0.571∗ − 0.253∗ 0.749∗ − 0.431∗ − 0.539∗ − 0.117 − 0.544∗ − 0.557∗ 0.526∗ 0.307∗ 0.241∗ 0.411∗ − 0.414∗ − 0.479∗ − 0.444∗
YR, yolk pH, and yolk aw . It reduces the strength of the vitelline membrane, but at the same time it causes a significant increase in EW, YW, and YR. Hens at 69–70 wk of age did not have such a large of egg quality. 2. Eggs’ storage time affected the quality of albumen and yolk. The greatest reduction in quality occurred after 3 d of storage. A significant decrease of albumen height, HU, YI, and strength of vitelline membrane was observed. An increase in the albumen pH and the yolk aw was also found after 3 d of storage. Extending the storage time up to 9 d did not have such a large of egg quality. 3. Interaction between hens age and storage time of eggs also had a significant impact on EW, albumen height, HU and albumen pH, YI, YW, YR, and yolk aw. The results indicate that HU and YI are parameters that are greatly influenced according to the hens age and storage time of eggs. Stored eggs from the younger hens retained good quality longer time than eggs from older hens, but EW and YW were significantly lower in eggs from younger hens. 4. Haugh unit and YI can be used to successfully monitor egg quality independently of hens age and storage time of eggs.
FUNDING This work was financially supported by the DSM Nutritional Products A/S P.O. Box 2676,
Bldg. 241 4002, Basel, Switzerland and also by a statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Faculty of Food Sciences of Warsaw University of Life Sciences.
DISCLOSURE STATEMENT The authors have not conflict of interest to disclose.
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29. StatSoft INC. 2011. STATISTICA (Data Analysis Software System), Version 10. Tulsa, Oklahoma, USA, StatSoft Inc. www.statsoft.com. ˇ 30. Zita, L., E. T˚umov´a, and L. Stolc. 2009. Effects of genotype, age and their interaction on egg quality in brownegg laying hens. Acta Vet. Brno. 78:85–91. 31. Oloyo, R. A. 2003. Effect of age on total lipid and cholesterol of hen eggs. Indian J. Anim. Sci. 73:94–96. 32. Peebles, E. D., C. D. Zumwalt, S. M. Doyle, P. D. Gerard, M. A. Latour, C. R. Boyle, and T. W. Smith. 2000. Effects of breeder age and dietary fat source and level on broiler hatching egg characteristics. Poult. Sci. 79:698–704. 33. Van Den Brand, H., H. K. Parmentier, and B. Kemp. 2004. Effects of housing system (outdoor vs cages) and age of laying hens on egg characteristics. Br. Poult. Sci. 45:745– 752. ˇ J. Simeonovov´a, M. Lichovn´ıkov´a, and 34. Zemkov´a, L., K. Somerl´ıkov´a. 2008. The effects of housing systems and age of hens on the weight and cholesterol concentration of the egg. Czech J. Anim. Sci. 52:110–115. 35. Silversides, F., and K. Budgell. 2004. The relationships among measures of egg albumen height, pH and whipping volume. Poult. Sci. 83:1619–1623. 36. Rossi, M., and C. Pompei. 1995. Changes in some egg components and analytical values due to hen age. Poult. Sci. 74:152–160. 37. Suk, Y. O., and C. Park. 2001. Effect of breed and age of hens on the yolk to albumen ratio in two different genetic stocks. Poult. Sci. 80:855–858. 38. Sokołowicz, Z., J. Krawczyk, and E. Herbut. 2012. Quality of eggs from organically reared laying hens during their first and second year of production. Food Sci. Technol. Qual. 4:185–194. (in Polish). 39. Akyurek, H., and A. A. Okur. 2009. Effect of storage time, temperature and hen age on egg quality in free–range layer hens. J. Anim. Vet. Adv. 8:1953–1958. 40. USDA. Unites States Department of Agriculture. 2000. Egg-Grading Manual. 56. https://www. ams.usda.gov/publications/content/egg-grading-manual. 41. Jin, Y. H., K. T. Lee, W. I. Lee, and Y. K. Han. 2011. Effects of storage temperature and time on the quality of eggs from laying hens at peak production. Asian Australas. J. Anim. Sci. 24:279–284. ´ 42. Smiechowska, M., and P. Podg´orniak. 2013. Study and assessment of selected quality parameters of organic hen eggs available on the tri–city market. J. Res. Appl. Agric. Eng. 58:186–189. 43. Calik, J. 2013. Changes in quality traits of eggs from ˙ yellow leg partridge (Z–33) laying hens depending on storage conditions of eggs. Food Sci. Technol. Qual. 87:73–79. (in Polish). 44. T˚umov´a, E., and Z. Ledvinka. 2009. The of time of oviposition and age on egg weight, egg component weight and eggshell quality. Arch. Gefl¨ugelkd. 73:110– 115. 45. Berardinelli, A., L. Ragni, A. Giunchi, P. Gradari, and A. Guarnieri. 2008. Physical–mechanical modifications of eggs for food–processing during storage. Poult. Sci. 87:2117–2125. 46. Marzec, A., M. Michalczuk, K. Damaziak, A. Mieszkowska, A. Lenart, and J. Niemiec. 2016. Correlations between vitelline membrane strength and selected physical parameters of poultry eggs. Ann. Anim. Sci. 16:897– 907.
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Agata Marzec,∗,1 Krzysztof Damaziak,† Hanna Kowalska,∗ Julia Riedel,† ‡ Monika Michalczuk,† Ewa Koczywas, Fernando Cisneros,§ Andrzej Lenart,∗ and Jan Niemiec† ∗
University of Life Sciences, 02-786, Warsaw, Poland; Department of Food Engineering and Process Management, Faculty of Food Sciences; † Poultry Breeding Division, Department of Animal Breeding and Production; ‡ DSM Nutritional Products Sp z o.o., 96-320 Mszczonow; and § DSM Nutritional Products A/S P.O. Box 2676, 4002, Basel, Switzerland
Primary Audience: Researchers, Eggs Consumers, Eggs Producer SUMMARY In this study, we aimed to determine the effect of hens age and storage time on the functional and physicochemical properties of eggs. Eggs from hens 25–26, 45–46, 55–56, and 69–70 wk of age were assessed, when fresh (0 d) and after storage 3, 6, and 9 d at 30◦ C and at 50% humidity. As hens age and storage time progressed, albumen height, Haugh unit (HU) score, yolk index (YI), and vitelline membrane strength (force breaking and elasticity) significantly decreased. The values of albumen height, HU, and YI were found to be higher in eggs obtained from the younger hens (25–26 wk of age) than those from the older hens. A significant effect of hens age was also found on the yolk pH and water activity. There was no statistical difference observed between the analyzed parameters of eggs from older hens (45–70 wk of age). There was no effect of hens age on the egg quality that was found to be the best when fresh. Interaction between hens age and the storage time also had significant impact on egg weight, albumen height, HU, yolk pH and YI, yolk weight, yolk ratio, and water activity. HU and YI scores were found to be greatly influenced by the age of hens and storage time of eggs. Changes of egg quality from the younger and older hens during storage have proceeded similarly, but eggs from older hens had significantly higher eggs weight and yolk weight that changed slowly. Key words: egg quality, Haugh unit, yolk index, force breaking 2018 J. Appl. Poult. Res. 0:1–11 http://dx.doi.org/10.3382/japr/pfy069
DESCRIPTION OF THE PROBLEM Monitoring of egg quality is important from an economic point of view. Of particular importance for egg producers is the quality of the shell, whereas for the processors and culinary pro1
Corresponding author: agata [email protected]
fessionals, the functional and physicochemical properties of eggs are important that indicate freshness and quality. The diet of hens plays a significant role in the external and internal egg quality; however, the storage conditions also affect egg quality. In addition, egg quality is influenced by various genetic factors [1] as well as environmental factors such as temperature and
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Effect of Hens Age and Storage Time on Functional and Physiochemical Properties of Eggs
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When the vitelline membrane weakens or breaks, these nutrients can contaminate the albumen and possibly inhibit its antimicrobial properties or allow bacteria to penetrate the yolk [14–16]. Vitelline membrane strength is important for egg breaking when separating the yolk from albumen as to reduce yolk contamination of the albumen. Physicochemical transformation of egg content reflects the aging process of egg. The egg quality, and thus its culinary and processing values, can be determined by measuring the physicochemical changes. Therefore, in this study, we aimed to evaluate the effects of hens age and storage time on the functional and physicochemical properties of eggs.
MATERIALS AND METHODS The experiment was conducted at the RZD Wilan´ow experimental station belonging to the Warsaw University of Life Sciences, Poland. The hens were kept in the commercial production, and supplements used in the experiment were recorded in the Register of Animal Feed Commission at the Ministry of Science and Higher Education Poland. According to the Council Directive 70/524/EEC, canthaxanthin has been authorized to be used up to 80 mg/kg in the diet laying hens. According to the EU Commission (2005) regulation 1459/2005, the permitted levels of iodine for laying hens range from 5 to 10 mg/kg of the feed (12% of humidity) [17, 18]. According to the Act of 22 July 2003 on experiments with animals [19], the production was not an experimental procedure and therefore did not require application to and consent of the National Ethical Commission at the Ministry of Science and Higher Education in Poland. Birds and Their Treatment A total of 300 ISA Brown laying hens (age 18 wk) used in this study were bought at the Musielak, Specialist Poultry Farm, Limited Company, Złotokłos, Poland. All birds were under veterinary control during the rearing and the laying periods. Lighting program and temperature in the building were consistent with the ISA Brown Management Guide [20]. The birds received the same feed. The laying performance
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storage humidity [2]. The process aging of egg influenced by the storage conditions has been studied previously in detail [3, 4]. The hens age influences the egg weight (EW) and shell quality [3, 5–7]. Albumen height and Haugh unit (HU) score are important indicators of egg quality; HU is a logarithmic function of height of thick albumen adjusted for EW [8]. Determining the HU score is a common way to assess the egg’s internal quality. Albumen quality constitutes a standard measure of egg quality testing and is of significance for both the processing industry and the consumer. Silversides and Scott [9] demonstrated that albumen height decreases with hen age, even if EW and the total albumen content in the egg increases in fresh eggs. Silversides and Villeneuve [10] reported that pH is a useful indicator of changes in albumen quality over time during storage. Significant increases in yolk pH were observed with increasing storage time [2]. Furthermore, hen’s age is the most important factor affecting the egg quality. Albumen quality decreases rapidly with advancing hens age [11]. Most of the changes in egg quality are measured in terms of HU score, albumen height, albumen pH, yolk index (YI), and EW and yolk weight (YW). Moreover, size of air cell increases with a loss in moisture content due to evaporation through the pores of the shell and the escape of carbon dioxide (CO2 ) from the albumen [12]. Thus, water activity (aw ) of albumen and yolk may also be an important indicator of egg quality. Water activity assumes values from 1 for clean water to 0 for the environment without water or where water molecules are unable to perform their activity. From the practical point of view, water activity means the amount of water available for the growth of microorganisms and activity of enzymes and other chemical changes that may take place in the food [13]. Both storage conditions and storage time may significantly affect the water activity of albumen and yolk, thus influencing the stability and quality of egg’s contents. The vitelline membrane, which surrounds the yolk, is responsible for keeping the yolk content separate from the albumen. Determining the strength of vitelline membrane is important because a strong vitelline membrane prevents components of the yolk from diffusing into the albumen. The yolk contains nutrients that are good for the growth of bacteria.
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Storage of Eggs Eggs from 25–26, 45–46, 55–56, and 69–70 wk of hens age were collected. Approximately 500 eggs were collected each time and were kept in storage chamber [22] at 30◦ C and 50% humidity during 3, 6, and 9 d. Analysis of Egg Quality Quality assessments were performed 4 times: on the day of laying (fresh eggs) and after 3, 6, and 9 d of storage, each time with 120 eggs per group. Eggs were analyzed using the ORKA Food Technology Egg Analyzer device [23], which determines EW (±0.1 g), height of thick albumen (mm), yolk weight (YW) (±0.1 g), and yolk color. Albumen height was expressed as height of thick albumen (mm) and in terms of HU score, which were automatically calculated from the measurements (on a scale of 0–130) by the device.
Table 1. Composition and Nutrients of Experimental Diets. Feed composition Wheat Yellow corn, 8.5% Soybean meal, E46% Uz Sunflower meal, O/C 36% Wheat bran, 16% Limestone, 38% Monocalcium phosphate Salt Sodium bicarbonate Sunflower oil DL Methionine Lysine HCL 1 Premix Nutrient ME Kcal/kg Crude protein g/kg Crude fat g/kg Crude fiber g/kg Calcium g/kg Available phosphorus g/kg Cys.+ Met g/kg Lysine g/kg Methionine g/kg Choline mg/kg Linoleic acid g/kg
5.00 56.17 13.82 8.00 5.85 8.08 0.51 0.22 0.10 1.00 0.15 0.12 1.00 2649.99 160.00 42.13 44.86 37.00 3.40 7.00 7.60 4.15 945.93 20.09
Supplementation per kg of premix: manganese 6,000 mg, zinc 6,000 mg, iron 6,000 mg, copper 800 mg, iodine 100 mg (according to treatment group), selenium 25 mg, vitamin A 1,000,000 IU, vitamin D3 300,000 IU, vitamin E 3,000 mg, vitamin K 250 mg, vitamin B1 250 mg, vitamin B2 250 mg, vitamin B6 350 mg, vitamin B12 1.5 mg, nicotinic acid 3,000 mg, panthotenic acid 800 mg, folic acid 100 mg, biotin 10 mg, canthaxanthin 3,000 mg, and phytase 60,000 FT.
Yolk ratio (YR) is expressed as the ratio of YW to EW (%). YI was determined by measuring the width of the yolk with dial calipers and the height of the yolk using a standard tripod micrometer (accuracy 0.01 mm). The yolks were measured in their natural position in the egg, and YI was calculated according to the following formula [24]: Yolk Index =
yolk height × 2 yolk width 1 + yolk width 2
Albumen was separated from the egg. Vitelline membrane strength was measured using the TA.HDPlus Texture Analyzer [25] with a 5-kg load cell and a sensitivity of 0.1 g. Compression tests were performed on egg yolks by
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of hens was controlled for 46 wk, that is, from the 23rd to 69th wk of age. The laying hens were kept in a 3-level cage battery with 30 cages total, 10 hens per each cage. The cages [21] had the following dimensions: width of 120 cm, depth 126 cm, and a minimum height 45 cm (910 cm2 /hen). They contained a scratchpad area (2 × 900 cm2 ), perch areas of 20 cm/hen, and 2 nests of 1,200 cm2 ; the floor gradient was 7.7◦ . The nesting area was separated by a red curtain composed of plastic strips. At the16th wk of age, light stimulation was started by extending day length for 2 h followed by extensions of 1 h/wk until it reached 16-h light exposure. The 16-h light stimulation was continued till the end of the experiment. Throughout the experiment, the average room temperature was maintained at 18 ± 2◦ C. Water was available ad libitum from 2 nipple drinkers in each cage. Experimental diets were limited to 114 g/hen/d and were administered twice a day (in portions 57 g each) after switching on the light and in the eighth hour of the day, through 240 cm long feeders (20 cm/hen). From the 18th wk of age onward, the hens were fed with feed mixtures (experimental diets) as shown in Table 1.
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Statistical Analysis Data were analyzed using the general linear model (GLM) procedures of Statistic 12PL. Factorial arrangement of hens age (W) and storage time of eggs (T) and respective interactions to assess the effect on functional and physiochemical properties of eggs were used. All statements of statistical significance were based on P < 0.05. Data were subjected to ANOVA using the procedure of GLM: Yi j = μ + Wi + T j + (W T )i j + ei jk where Yij is a variable: μ is the general mean; Wi is the week of hens age, i = 25–26, 45–46, 55– 56, and 69–70 wk of hens age; Tj is the storage time, j = 0, 3, 6, and 9; (WT)ij is the interaction of age × storage time; and eijk is the random error. The model a multiple linear regression was used to describe the hens age and shelf weeks on the HU and YI score: Y = b0 + b1 W + b2 T ± e where Y is the HU or YI; b0 , b1 ,, and b2 are the regression coefficients; W is the week of hens age; T is the storage time; and
analyzed variables was assessed with the help of PCA. This analysis allows the possibility to observe similarities and differences between the study groups [29].
RESULTS AND DISCUSSION Effect of Hens Age Tables 2 and 3 present the effects of hens age on the functional and physicochemical properties of eggs. The hens age significantly affected all tested parameters except for the albumen aw (P = 0.775), color (P = 0.829), and elasticity of vitelline membrane (P = 0.080) of yolk. The average value of EW from the younger hens (25–26 wk of age) was around 54 g, which was found to be statistically lower than eggs from older hens (61 g, 45–70 wk of age) (P < 0.001) (Table 2). Hens age is a factor that affects the value of EW [7, 30]. Several research studies have shown that eggs from older hens are heavier than those obtained from younger ones [8, 9, 31–33]. On the contrary, Zemkov´a et al. [34] showed that the age of hens has no significant influence on EW. In this study, we found significant influence (P < 0.001) of hens age on the values of albumen height and HU. Both these parameters were found to be significantly higher in case of eggs obtained from younger hens (25–26 wk of age) than those obtained from older hens. Albumen height and HU score were found to be higher in case of eggs obtained from the younger hens (25–26 wk of age) than from the older hens by approximately 22%. Our results demonstrated that older hens had greater YW and YR values (22 and 13%, respectively) than that of younger hens (Table 3). The relationship is consistent with that described in the literature [32–37]. In this study, lowest YW and YR were found in case of younger hens at 25–26 wk of age than that of older hens at 45–70 wk of age (Table 3). Zita et al. [30] confirmed that YW and YR significantly increased with the hens age, which agrees with our results. It was found that the hens’ age had an effect on the increase EW, YW, and YR [38]. YI was found to be 0.342 for eggs from younger hens (25–26 wk of age) and 0.315 from older hens (45–70 wk of age) (Table 3). This means that eggs from
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a cylindrical probe with a diameter of 100 mm and with an applied compression rate of 1 mm/s to obtain 300 g of force. Vitelline membrane strength was shown in terms of breaking force (g) and elasticity (mm). Egg yolk color was visually measured using a YolkFanTM [26], which is an industrial color scale varying from 1 (pale yellow) to 16 (dark orange). Albumen and yolk pH were separately measured using a pH meter with glass electrode IJ44C [27]. Albumen and yolk water activity (aw ) were measured using the AquaLab Model CX-2 [28] at 30◦ C.
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Table 2. Effect of Hens Age and Eggs Storage Time on Functional and Physicochemical Properties of Eggs Albumen.1 Albumen
25–26
Storage time (d)
EW2 (g)
Height (mm)
Haugh unit
pH
aw 3
0 3 6 9
57.93 53.43 53.85 52.62 0.29 <0.001 62.67 60.87 60.22 58.44 0.36 <0.001 64.23 62.19 62.22 60.23 0.32 <0.001 62.34 61.19 60.93 60.31 0.32 <0.001
8.75 5.04 4.10 3.74 0.08 <0.001 7.06 4.07 2.97 2.73 0.07 <0.001 7.27 3.99 3.09 2.56 0.08 <0.001 6.86 3.83 3.08 2.58 0.07 <0.001
93.52 71.44 62.30 59.39 0.63 <0.001 83.18 58.16 43.69 42.07 0.76 <0.001 83.74 56.35 44.37 36.72 0.85 <0.001 81.39 54.74 45.25 37.55 0.89 <0.001
7.8 8.8 9.1 9.1 0.04 <0.001 8.1 9.2 9.4 9.4 0.03 <0.001 8.2 9.2 9.3 9.4 0.02 <0.001 8.2 9.1 9.3 9.4 0.03 <0.001
0.989 0.993 0.992 0.990 0.0005 0.403 0.990 0.990 0.990 0.991 0.0006 0.850 0.990 0.992 0.992 0.992 0.0003 0.250 0.990 0.992 0.992 0.991 0.0005 0.728
0.14 0.24 0.24 0.002 0.003 0.023
0.08 0.04 0.06 <0.001 <0.001 <0.001
0.65 0.22 0.60 <0.001 <0.001 <0.001
0.01 0.01 0.02 <0.001 <0.001 <0.001
0.0004 0.0004 0.0007 0.775 0.072 0.724
SEM P-value 45–46
0 3 6 9 SEM P-value
55–56
0 3 6 9 SEM P-value
69–70
0 3 6 9 SEM P-value
Source of variation SEM Weeks of age Storage time Weeks of age × storage time P-value Week of age Storage time Weeks of age × storage time Values are means for 120 eggs in each parameter. 2 EW = egg weight. 3 aw = water activity.
both younger and older hens were characterized by acceptable quality to consumers. The hens age had a significant impact (P < 0.001) on the value of YI (Table 3). The value of YI from the younger hens was found to be about 8% higher than that of older hens. The yolk color is an important parameter for the consumer. Although preferences vary, consumers in most countries prefer an egg yolk color with a DSM YolkFanTM value of 12 or more [26]. The hens age was also not found to affect the yolk color (Table 3). Yolk color was found to be stable and did not change with the hens age from 25 to 70 wk (Table 3). Probably, the
observed higher values of yolk color were due to diet of hens. Vitelline membrane strength was evaluated on the basis of its breaking force and elasticity. Elasticity is the distance from the point of the membrane deformation to its breaking. There were no significant (P = 0.08) differences between the elasticity of the membrane depending on the hens age (Table 3). The highest breaking force (274 g) was observed at 25–26 wk of hens age. The vitelline membrane of the yolk from older hens (45–70 wk of age) was weaker (18%); the difference was significant in relation to the hens at 25–26 wk of age (Table 3).
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Weeks of age
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Table 3. Effect of Hens Age and Eggs Storage Time on Functional and Physicochemical Properties of Eggs Yolk.1 Weeks of age
Storage time (d)
Yolk Ratio2 (%)
SEM P-value
13.89 13.09 13.77 14.01 0.09 <0.001 16.94 17.83 17.33 17.93 0.13 <0.001 17.23 17.63 18.76 18.93 0.13 <0.001 16.62 17.82 18.34 18.65 0.13 <0.001
23.99 24.54 25.62 26.67 0.16 <0.001 27.08 29.37 28.81 30.72 0.19 <0.001 26.88 28.38 30.20 31.46 0.21 <0.001 26.72 29.16 30.15 30.97 0.21 <0.001
0.416 9.55 0.374 8.76 0.314 9.03 0.262 9.17 0.002 0.27 <0.001 0.220 0.386 9.61 0.350 8.98 0.270 9.03 0.238 9.59 0.003 0.291 <0.001 0.390 0.379 9.90 0.333 9.59 0.295 9.62 0.214 10.22 0.003 0.21 <0.001 0.142 0.382 9.88 0.344 9.65 0.288 9.44 0.247 9.78 0.003 0.26 <0.001 0.668
Source of variation SEM Weeks of age Storage time Weeks of age × storage time P-value Weeks of age Storage time Weeks of age × storage time
0.08 0.16 0.02 <0.001 <0.001 <0.001
0.08 0.08 0.15 <0.001 <0.001 <0.001
<0.001 <0.001 0.002 <0.001 <0.001 <0.001
25–26
0 3 6 9 SEM P-value
45–46
0 3 6 9 SEM P-value
55–56
0 3 6 9 SEM P-value
69–70
0 3 6 9
Index
Force Color breaking (g)
0.11 0.11 0.19 0.829 0.905 0.944
Elasticity (mm)
pH
273.96 232.22 211.81 207.29 4.50 <0.001 246.94 197.58 168.80 148.49 4.07 <0.001 254.01 193.14 171.82 153.94 3.91 <0.001 237.87 195.90 171.01 145.84 4.03 <0.001
9.11 7.48 6.43 5.44 0.08 <0.001 9.00 7.41 5.83 4.90 0.06 <0.001 9.09 7.49 6.19 4.97 0.06 <0.001 8.90 7.89 6.24 5.28 0.10 <0.001
5.6 5.5 5.7 5.7 0.01 <0.001 6.1 6.2 6.2 6.2 0.06 <0.001 6.1 6.1 6.2 6.2 0.05 <0.001 6.1 6.1 6.2 6.2 0.05 <0.001
0.986 0.987 0.988 0.986 0.0003 <0.001 0.984 0.986 0.985 0.987 0.0003 <0.001 0.983 0.988 0.988 0.988 0.0004 0.025 0.986 0.989 0.989 0.990 0.0004 <0.001
1.81 1.81 3.13 <0.001 <0.001 0.161
0.04 0.06 0.06 0.080 <0.001 <0.001
0.02 0.03 0.05 <0.001 <0.001 <0.001
0.03 0.03 0.05 <0.001 <0.001 <0.001
aw 3
Values are means for 120 eggs in each parameter. 2 Yolk weight ratio to egg weight (%). 3 aw = water activity.
In this study, yolk pH (from hens 25–26 wk of age) was about 5.6; however, in eggs from older hens (45–70 wk of age) yolk pH was about 6.1, which is significantly higher than in the case of younger hens (P < 0.001) (Table 3). Yolk aw of eggs from hens at 25–46 wk of age was about 0.986. However, eggs from older hens (55–70 wk of age) had yolk aw about 0.988. Observed differences in yolk aw were found to be significant (P < 0.001) (Table 3). At the same time, there were no differences in yolk pH from hens at 45– 70 wk of age as well as in yolk aw from hens at 55–70 wk of age. Effect of Storage Time of Eggs As in the case of hen aging, the prolonged storage time of eggs significantly affected the
deterioration of the parameters of most of the analyzed albumen parameters (Table 2) and egg yolk (Table 3). The storage time of eggs did not impact the albumen aw (P = 0.072) and yolk color (P = 0.905). HU score was found to be decreased by about 22 and 47% after 3 and 9 d of storage, respectively. Albumen height was found to be decreased by about 61% after 9 d of storage (Table 2). Scientists have reported that albumen height and the HU score value are equally indicators of albumen quality [10, 14], which is similar to our results. It is assumed that higher the value of HU, the better is egg quality [2, 5]. There are many studies describing the influence of storage time and temperature on HU [2, 6, 39]. Determining HU score to assess the egg’s interior quality [8] has been accepted by the USDA Agricultural Marketing Service as a
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Weight (g)
MARZEC ET AL.: HENS AGE AND STORED EGGS
the measured breaking force are characterized by considerable standard deviation [46]. Interaction of Hens Age and Storage Time of Eggs The significant interaction of hens age and storage time of eggs was confirmed for height, HU, and albumen pH (Table 2), and the most parameters of yolk except for color and breaking force of VM (Table 3). The results of this study showed that all the tested parameters of egg quality showed that hens age and storage time caused considerable changes in the values of HU and YI. These changes have been explained mathematically using the regression equation. Table 4 presents the model and coefficients of regression equation. According to the regression equation, the expected values for HU and YI were found to be 98.55 and 0.426, respectively. The HU and YI values expected through estimation differ from the real (empirical) values on average by 10.82 (HU) and 0.035 units (YI), respectively. The value of HU was found to be decreased by a mean of 0.380 units in albumen from older hens and by 4.52 units with the prolongation of the storage time. Furthermore, changes were observed in case of values of YI, which was found to be decreased with the hens age yet on average by 0.001 and approximately by 0.017 with the storage time (Table 4). Our analysis demonstrates that YI is a more sensitive parameter describing the quality of egg than that of HU score. In addition, the determination factor (R2) for HU is lower than that of YI. This means that the proposed linear model describes variability in 69.3% HU and in 73.2% YI according to the age of hens and storage time (Table 4). Principal Component Analysis PCA was conducted, allowing for a reduction of analyzed parameters and grouping eggs with similar quality. For the analysis of PCA, 10 parameters were considered: vitelline membrane strength (breaking force and elasticity), EW, albumen height, HU, YW, YR, YI, albumen pH, and yolk aw . PCA reduces the number of parameters from 10 to 2 (PC1 and PC2) (Figure 1). Component PC1 was positively correlated with albumen height, HU score, vitelline
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reliable method [40]. Furthermore, albumen pH in case of younger hens (24–25 wk of age) was found to be 7.8, which was found to be significantly lower than that of older hens (pH = 8.2; 45–70 wk of age) (Table 2). However, there was no difference between the albumen pH evaluated from older hens (45–70 wk of age) (Table 2). During storage there was an increase in the value of albumen pH (Table 2). Egg albumen releases CO2 originating from the carbonic acid dissociation, forming a buffer system within albumen. The process is followed by alkalization, demonstrated by an increase of albumen pH [41]. Alkalization within the egg causes changes in the structure of albumen. Numerous authors confirm the relationship between the storage time of eggs and the increase in albumen pH [42–44]. Usually, the quality of yolk is given by YW, YR, and YI. Our results confirmed a significant of storage time on the values of YW and YR (P < 0.001) (Table 3). YW was found to be increased by about 5 and 9% after 3 and 9 d of storage, respectively. Extension of the storage time caused a decrease in the value YI, which dramatically decreased by 10% after 3 d and 37% after 9 d of storage (Table 3). Statistical analysis showed that the storage time of eggs had significant influence on the vitelline membrane strength (breaking force and elasticity). After 3 d of storage, the breaking force decreased by approximately 20%, and after 9 d it decreased by approximately 34%. In case of elasticity, the decrease amounted to approximately 17% after 3 d of storage, but after 9 d, it was found to by approximately 43% (Table 3). According to Berardinelli et al. [45], the rupture energy and the maximum force, obtained by driving a probe with diameter of 2 mm into the highest point of the yolk, significantly decreased by about 40% after 3 d of storage at 20◦ C. Caudill et al. [14] stated that the vitelline membrane strength, along with the HU, constitutes another important parameter of egg quality. It should be emphasized that in practice the evaluation of vitelline membrane strength is a difficult task, requiring a strength-measuring device (texture analyzes) with appropriate sensitivity. Moreover, selection of the proper deformation probe and finding the rate of destruction is necessary in such a study. Due to the heterogeneity of the vitelline membrane, the mean values of
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Table 4. Regression Analysis Coefficient and Model of Hens Age and Eggs Storage Time. N = 1920
Significance directivity factor
HU
∗
b1
b2
ε
R2
−0.380
−4.528
10.821
0.697
Weeks of age Storage time
−0.316 −0.773∗
98.553
Weeks of age Storage time
−0.151∗ −0.842∗
0.426
Model Yolk index Model ∗
HU = –0.38 (W) -4.53 (T) + 98.55 ± 10.82 −0.001 −0.017 0.035 0.732
YI = –0.001 (W) – 0.017 (T) + 0.426 ± 0.035
Significant values.
Figure 1. PCA diagram. The effect of hens age and storage time on the functional and physicochemical properties of eggs. Hens age 25–26 wk: A – 0 fresh, B – 3 d, C – 6 and 9 d eggs storage time. Hens age 45–46, 55–56, 69–70 wk: D – 0 fresh, E – 3 d, F – 6 and 9 d eggs storage time.
membrane strength (breaking force, elasticity), but YI correlation with YR, albumen pH, and yolk aw was negative. PC1 explains 70.7% of the variability of the studied traits. PC2 was positively correlated with EW and YW, and explains 20.5% of the variance. The loss of information on reduction in parameters was found to be minor, which amounted to 8.8%. Table 5 presents correlation parameters with PC1 and PC2 components.
The fresh and stored eggs from younger and older hens were more or less grouped according to their preparation procedure in the space for PC1 and PC2 components (Figure 1). Egg quality deteriorated with the hens age and storage time. The examined eggs were assigned to 6 groups (A, B, C, D, E, and F) differing in PC1 and PC2 components. Fresh eggs from the younger hens (25–26 wk of age) (group A) were located on the right side of the
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b0
MARZEC ET AL.: HENS AGE AND STORED EGGS Table 5. Correlation Between PC1, PC2, and Egg Quality Parameters. Parameters
PC1
PC2
0.97 1.00 − 0.01 0.99 0.91 0.92 − 0.62 − 0.87 − 0.94 − 0.68
0.16 0.02 0.99 − 0.04 0.35 0.17 0.79 0.46 − 0.20 − 0.16
diagram and possessed the highest values of PC1 component (Figure 1) meaning that they had the highest values of albumen height, HU, YI, vitelline membrane strength, and lower values of albumen pH and yolk aw (Tables 2 and 3). Fresh eggs from older hens (45–46, 55–56, and 69– 70 wk of age—group D) had similar quality parameters, and they were characterized by smaller PC1 and larger PC2 component than eggs from younger hens (25–26 wk of age—group A). PCA suggested that better fresh egg quality (groups A and D) was associated with PC1 component (YI, breaking force and elasticity of vitelline membrane, HU, and albumen height) (Figure 1). PCA diagram clearly shows that fresh eggs from older hens (group D) had the quality parameters (PC1) only slightly worse than eggs form younger hens (group A). But group D had higher PC2 component (EW and YW) than group A. However, regarding hens age, eggs from older hens had faster degradation of egg quality from storage 3 to 9 d (groups E and F in opposition to groups B and C). During storage, PC1 component was found to decrease in case of eggs from older hens (45–70 wk of age), whereas PC2 component did not change. Poor egg quality was due to the increase in albumen pH and yolk aw . There were no differences with respect to egg quality parameters between eggs stored for 6 and 9 d (group F). The difference between eggs from the younger (groups A, B, and C) and older hens (groups D, E, and F) is mainly due to the increase in PC2 component (increase EW and YW in older hens). However, eggs from the younger hens had lower PC2 component than eggs from older hens, which was in terms of lower EW and YR. Eggs from the oldest hens (69–70 wk of age) had the same quality as eggs from younger hens (45–46 and 55–56 wk of age).
Regarding storage time, eggs from older hens had greater degradation in egg quality after 3 d of storage (groups E and F), as already observed for eggs from younger hens (groups B and C). Eggs from the younger hens stored at 6 and 9 d (group C) had the same PC1 component, which is similar to the eggs from older hens stored at 3 d (group E). This means that stored eggs from the younger hens retained good quality for longer time than stored eggs from older hens. The storage time of 3, 6, and 9 d had a strong impact on PC2 component from the younger hens (samples were distributed in the lower portion of the diagram) (Figure 1). EW and YW were considerably decreased (Tables 2 and 3). Eggs from the younger hens (25–26 wk of age) after 3, 6, and 9 d of storage were also characterized by lower PC1 component than that of fresh eggs. In case of eggs from older hens (45–46, 55– 56, and 69–70 wk of age), PC1 component decreased after 3, 6, and 9 d of storage (samples distributed on the left side of the diagram). However, PC2 component was less affected by the storage time. This means that eggs from older hens are less susceptible to the changes in EW and YW. Thus, HU and YI parameters with a strong correlation to PC1 appear to be good parameters of egg quality evaluation (Table 5). Furthermore, the egg quality parameters strongly correlated with other (Table 6). Statistical analysis (correlation matrix) based on hens age and storage time of eggs showed that force and elasticity are positively correlated with albumen height, whereas HU and YI and force and elasticity are negatively correlated with the YW, YR, albumen pH, and yolk aw (Figure 1, Table 6). As storage time progressed, the average values of yolk pH increased after 6 d of storage (Table 3). Yolk aw of fresh eggs was found to be significantly lower than that of stored eggs (Table 3). The change in aw during storage is caused by the diffusion of water from the albumen to the egg yolk. Differences among the yolk aw in eggs stored for 3, 6, and 9 d were not found (Table 3).
CONCLUSIONS AND APPLICATIONS 1. Hens age influences the strength of the vitelline membrane (breaking force), EW,
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Albumen height (mm) Haugh unit Egg weight (g) Force breaking (g) Elasticity (mm) Yolk index Yolk weight (g) Yolk ratio (%) Albumen pH Yolk water activity
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10 Table 6. Correlation Between Functional and Physicochemical Properties of Eggs. Egg weight 0.137
Haugh unit
Albumen Albumen pH aw
Yolk weight
Yolk ratio
Yolk index
Force breaking Elasticity
1.000
− 0.002 − 0.162
0.975∗ 1.000 − 0.975∗ − 0.938∗
1.000
− 0.037
− 0.219∗ − 0.191
0.213∗
1.000
0.415∗
0.075
0.756∗ − 0.460∗ − 0.585∗
0.379∗ − 0.739∗ − 0.820∗ 0.692∗ 0.127 0.895∗ − 0.825∗ − 0.098 0.151 0.871∗ 0.927∗ − 0.859∗ − 0.172 − 0.012 0.897∗
1.000 0.892∗ − 0.423∗ − 0.578∗
1.000 − 0.703∗ − 0.806∗
1.000 0.851∗
1.000
0.890∗ 0.885∗ − 0.862∗ − 0.132 − 0.276∗∗ − 0.616∗ 0.955∗ 0.869∗ 1.000 0.328∗ 0.381∗ 0.033 0.955∗ 0.838∗ − 0.406∗ − 0.571∗ − 0.253∗ 0.749∗ − 0.431∗ − 0.539∗ − 0.117 − 0.544∗ − 0.557∗ 0.526∗ 0.307∗ 0.241∗ 0.411∗ − 0.414∗ − 0.479∗ − 0.444∗
YR, yolk pH, and yolk aw . It reduces the strength of the vitelline membrane, but at the same time it causes a significant increase in EW, YW, and YR. Hens at 69–70 wk of age did not have such a large of egg quality. 2. Eggs’ storage time affected the quality of albumen and yolk. The greatest reduction in quality occurred after 3 d of storage. A significant decrease of albumen height, HU, YI, and strength of vitelline membrane was observed. An increase in the albumen pH and the yolk aw was also found after 3 d of storage. Extending the storage time up to 9 d did not have such a large of egg quality. 3. Interaction between hens age and storage time of eggs also had a significant impact on EW, albumen height, HU and albumen pH, YI, YW, YR, and yolk aw. The results indicate that HU and YI are parameters that are greatly influenced according to the hens age and storage time of eggs. Stored eggs from the younger hens retained good quality longer time than eggs from older hens, but EW and YW were significantly lower in eggs from younger hens. 4. Haugh unit and YI can be used to successfully monitor egg quality independently of hens age and storage time of eggs.
FUNDING This work was financially supported by the DSM Nutritional Products A/S P.O. Box 2676,
Bldg. 241 4002, Basel, Switzerland and also by a statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Faculty of Food Sciences of Warsaw University of Life Sciences.
DISCLOSURE STATEMENT The authors have not conflict of interest to disclose.
REFERENCES AND NOTES 1. Johnson, A. S., and E. S. Merritt. 1955. Heritability of albumen height and specific gravity of eggs from white Leghorns and Barred Rocks and the correlations of these traits with egg production. Poult. Sci. 34:578–587. 2. Samli, H. E., A. Agna, and N. Senkoylu. 2005. Effects of storage time and temperature on egg quality in old laying hens. J. Appl. Poult. Res. 14:548–553. 3. Siyar, S. A. H, H. Aliarabi, A. Ahmad, and N. Ashori. 2007. Effect of different storage conditions and hen age on egg quality parameters. Aust. Poult. Sci. Symp. 19:106–109. 4. Roberts, J. 2004. Factors affecting egg international quality and egg shell quality in laying hens. Jpn. Poult. Sci. 41:161–177. 5. Fletcher, D. L., W. M. Britton, G. M. Pesti, A. P. Rahn, and S. I. Savage. 1983. The relationship of layer flock age and egg weight on egg component yields and solids content. Poult. Sci. 62:1800–1805. 6. Feddern, V., M. Celant de Pr´a, R. Mores, R. da Silveira Nicoloso, A. Coldebella, and P. Giovanni de Abreu. 2017. Egg quality assessment at different storage conditions, seasons and laying hen strains. Ciˆenc. Agrotec. 41:322–333, May/Jun. 2017 http://dx.doi.org/10.1590/1413-70542017413002317. 7. Rizzi, C., and G. M. Chiericato 2005. Organic farming production. Effect of age on the productive yield and egg
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Albumen height Haugh unit Albumen pH Albumen aw Yolk weight Yolk ratio Yolk index Force breaking Elasticity Yolk pH Yolk aw
Albumen height
MARZEC ET AL.: HENS AGE AND STORED EGGS
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