Exploring the physical characteristics of eggs for consumption and industrial use in Kosovo: a comprehensive quality analysis

ABSTRACT

                 Kosovo, like the global trend, is experiencing a rising demand for eggs, emphasizing the necessity for stringent regulatory oversight to maintain freshness and meet increasing consumer and industrials’ needs. The research aimed to evaluate the compliance of eggs in the local market with specified quality criteria outlined in the local Administrative Directive and EC Regulation. Several quality parameters were scrutinized, including egg weight, length, width, specific gravity, air cell, Haugh units (HU), yolk and egg white weights, yolk color intensity, shell weight, and shell thickness. Key parameters varied significantly among Fresh Eggs and farms F1 to F5. Most groups displayed significantly lower egg weights, yolk, and egg white weights compared to Fresh Eggs (p < 0.01). Among different groups, Fresh Eggs have the highest Haugh unit and the lowest specific gravity, indicating superior egg quality. Among groups, F4 has the lowest Haugh unit (p < 0.00001), and F3/F4 exhibited the largest air cell size (p < 0.0001), while F5/Fresh Eggs were the smallest, with no significant differences between themselves (p > 0.05). Fresh eggs outshined in all groups in relation to size and yolk color (p < 0.0001). The study found positive correlations (p < 0.01) between egg weight and internal parameters, including yolk and white weights. Eggshell weight also correlated positively with yolk and white weights (p < 0.05). Conversely, Haugh unit and air cell exhibited negative correlations (p < 0.01), indicating their influence on egg dimensions. Classification based on regulation revealed distinct categories for consumption and industrial use. These findings contribute valuable insights to Kosovo’s egg market, impacting standards and promoting fair competition.

KEYWORDS:

• Egg quality
• internal parameters
• external parameters
• farmers
• Pearson’s correlation

Introduction

Eggs are among the most nutritional and widely consumed foods. They are known as a “miracle food” because of their high protein content, different amino acids, and the perfect balance of unsaturated and saturated fatty acids, while being low in carbohydrates and trans fats.^[1] They are utilized extensively in the food industry because of their high nutritional value and useful functional qualities, including coagulation, gelling, and emulsification.^[2] In the baking, confectionery, culinary and other industries, eggs are commonly utilized as primary or secondary components.^[3,4]

In most countries worldwide, especially in the last decade, due to the high demand for eggs for human consumption and the industry,^[5,6] as well as because the eggs of chickens have high nutritional values and are considered as a complete nutritious product, their production and trade are constantly increasing and in satisfactory parameters.^[1,7–12]

Food and Agriculture Organization shows that worldwide egg production has increased by 29.2%, from 67.0 million metric tons in 2012 to 86.6 million in 2020.^[7] Of the total production of eggs, approximately 30% are used in the second transformation industry producing liquid products from eggs and several solid wastes of eggshells.^[13] In Kosovo, poultry farming is one of the most developed industries. Commercial egg production in Kosovo is mainly oriented toward the production of eggs for consumption and their use in industry.^[14]

The Green Report of the Ministry of Agriculture, Forestry and Rural Development,^[14] shows that in 2020, the total number of poultries in Kosovo has increased by 4.4% compared to the previous year, thus meeting the needs for egg consumption with about 99%. As for the poultry production industry in Kosovo, 73.5% are laying hens, and egg production in 2020 in commercial farms and family farms is estimated to have been around 366 million eggs, compared to 350 million eggs produced in 2016.^[14] While the average consumption per capita in Kosovo is calculated to be 206 eggs/per year. The EU average is 210 eggs per year per capita. However, even among EU nations, there were differences in egg intake: Poland (145 eggs) and Portugal (146 eggs) had lower levels of egg consumption than Spain (273 eggs) and Denmark (248 eggs).^[15] Beyond its nutritional content, studies have indicated that the physical characteristics of an egg (external and internal), hold crucial significance for both consumers, food industry as well as producers.^[12] Additionally, consumer preferences are influenced by socio-cultural factors in addition to the external and internal qualities,^[16]

One of the most important factors in determining the quality of an egg is its freshness, especially when evaluating the yolk and white contents. This is because the nutritional value, processing, by-products, marketing, and selling price of eggs are all influenced by their freshness.^[2,17–24] Furthermore, freshness is the most important index used in the transport and marketing of eggs, and it has been reported that consumers often use this parameter to evaluate the quality of eggs and their nutritional value.^[19,23,25] The freshness attribute of the products is a highly evaluated attribute for other food products in Kosovo.^[26] It has been reported that in addition to environmental,^[23,24] and genetic factors,^[27] egg quality, is also affected by other factors such as diet, chicken age, stress, temperature, lighting, medications used, diseases, management and growth system etc.^[2,28–30]

The primary purpose of this study was to perform a complete and comprehensive analysis of the physical characteristics of eggs in Kosovo, with a special focus on their suitability for both consumer consumption and industrial use in accordance with local and European regulations. Parameters related to egg quality were also compared between farms. A variety of external and internal quality parameters were included in the physical characteristics assessment, including egg weight, egg length, egg width, specific gravity, air cell, Haugh units (HU), egg yolk weight, egg white weight, yolk color intensity, shell weight and yolk thickness of eggs from various sources in Kosovo. The findings of this study will contribute to a deeper understanding of the physical characteristics of eggs in Kosovo, facilitating informed decisions for both consumers and industrial stakeholders. Additionally, the insights gained from this research can be valuable for policymakers in refining regulations and standards related to egg production and quality in the Kosovo.

Materials and methods

Five larger egg producers situated in distinct municipalities across Kosovo, namely Rahovec, Gjakovë, Podujevë, Lipjan, and Ferizaj, with Prishtina serving as the reference group, have been included in the experiment. The reference samples included day-old eggs. The eggs were evaluated based on the quality criteria in the local Administrative Directive (AD No. 17/2008),^[31] and European Commission Regulation (EC No 589/2008). A total of 360 eggs from each producer were sampled from food supermarkets, and an additional 100 fresh eggs (one day old) were sourced from a poultry farm in the Prishtina region. In total, 1,900 eggs underwent analysis over the period from February to October 2022. This sampling strategy allowed for a comprehensive evaluation of egg quality across different producers and regions within Kosovo. The inclusion of a reference group and adherence to regulatory criteria ensure that the study provides a robust assessment of the eggs available in the market. Table 1 provides an overview of different characteristics for six groups of egg producers, including groups Fresh Eggs, F1, F2, F3, F4, and F5. The characteristics include the laying hens’ breeds, the number of hens, and the annual egg production per farm.

Table 1. Number of laying hens and egg production in farms.

Characteristics	Fresh Eggs	F1	F2	F3	F4	F5
Laying Hens Breeds	ISA Brown	ISA Brown	ISA Brown	Lohmann Brown	Lohmann Brown	ISA Brown
The number of hens	10,000	15,000	30,000	11,140	25,000	46,816
The number of eggs produced per year/farm	2,750.00	4,050,000	8,250,000	3,063,500	6,625,000	12,640,320

Weighting the egg, the shell, the yolk, and the egg white, the standard analytical scale (model Analytical Balance, Series BA-W2104, China) was utilized. While, the official egg air cell gauge, FORM PY-35 (5-1-74) was used to measure the air cell size in accordance with US standards and grades for eggs.^[32]

The specific gravity (SW) was estimated by immersing the eggs in saline solutions until they reached their floating point. Various NaCl solutions with specific weights ranging from 1.050 to 1.100 in increments of 0.005 g/cm3 were created in order to ascertain the specific weight of the eggs (Hydrometer precision, 1.000 to 1.100 g/cm³, Greiner-Glasinstrumente, Germany). A Haugh meter (Haugh unit micrometer, B C Ames Co, Waltham, Massachusetts, USA) was used to determine Haugh Units (HU), according to USDA.^[32]

The yolk of each egg was weighed and their color density was visually assessed using DSM Yolk Color Fan with 16 scales (formerly Roche Yolk Color Fan) described according to Beardsworth & Hernandez.^[33] While for the evaluation of the thickness of the eggshell, the length and width of the egg, an Electronic Digital Caliper Micrometer, Adoric 0–6,” with Inch and Millimeter Conversion (150/6) was used.

Statistical analyses

In the analysis of egg quality parameters, Pearson’s correlation coefficients were computed using IBM SPSS (Version 24.0, Armonk, NY). The investigation included a one-way analysis of variance (ANOVA) to assess the inter-group differences across all recorded parameters. Statistical significance was established at a probability threshold of less than 0.05 for all analyses. Post hoc testing was conducted using the Tukey Honestly Significant Difference (HSD) or Tukey Kramer test to discern statistically significant variations between the means of individual groups.

Results and discussions

Table 2 contains key data on statistically significant differences between the means of all independent groups, with significance levels indicated (p-values). Additionally, standard error mean values are provided. Significant variations are evident in key attributes such as egg weight, shell weight, yolk weight, egg white weight, specific gravity, Haugh unit, air cell size, Roche Yolk Color, eggshell thickness, egg length, and egg width. The accompanying standard error of the mean (SEM) and p-values indicate the statistical significance of these differences (Table 2).

Table 2. Egg characteristics variation across different experimental groups (various farms).

Parameters	FreshEggs	F1	F2	F3	F4	F5	SEM	p-value
Egg weight g	66.95	62.06	64.33	60.21	56.98	63.43	0.8102	<0.00001
Eggshell weight g	7.98	7.40	7.39	6.61	7.03	7.94	0.1778	<0.01
Egg yolk weight g	15.32	14.60	14.80	13.93	13.40	14.40	0.3459	<0.01
Egg white weight g	43.63	40.20	42.02	39.45	36.82	41.35	0.7238	<0.0001
Specific Gravity g/cm3	1.086	1.068	1.075	1.065	1.062	1.076	0.0014	<0.00001
Haugh unit (HU)	91.20	75.13	77.61	71.74	62.90	80.94	1.2391	<0.00001
Air cell mm	3.44	4.52	4.47	5.83	6.21	4.22	0.2703	<0.0001
Roche Yolk Color	12.71	9.44	12.13	11.75	10.44	12.31	0.2334	<0.00001
Egg Shell Thickness µm	0.44	0.41	0.45	0.39	0.38	0.42	0.0079	<0.0001
Egg length mm	57.43	53.80	56.05	52.82	49.14	54.72	0.6164	<0.0001
Egg width mm	44.81	42.40	43.8	40.52	38.13	42.35	0.5813	<0.00001

Note: ¹F1, F2, F3, F4, F5: Chicken Eggs Farm; SEM: Standard error mean (%); p < 0.01-Fairly significant;

p < 0.0001-Very highly statistically significant; p < 0.00001-Profoundly significant

Table 3 presents comprehensive measurements of various physical parameters related to eggs across different egg samples. The data is organized for individual egg pairs (FreshEggs, F1, F2, F3, F4, F5) and their combinations (e.g., F1-F2). The parameters evaluated and compared between pairs include egg weight, eggshell weight, egg yolk weight, egg white weight, specific gravity, Haugh unit (HU), air cell size, Roche Yolk Color, egg shell thickness, egg length, and egg width.”

Table 3. Pairwise comparison analysis of egg characteristics with significance levels.

Pair	Egg weight g	Eggshell weight g	Egg yolk weight g	Egg white weight g	Specific Gravity g/cm3	Haugh unit (HU)	Air cell mm	Roche Yolk Color	Egg Shell Thickness µm	Egg length mm	Egg width mm
FEgg-F1	p < 0.001	p > 0.05	p > 0.05	p < 0.05	p < 0.00001	p < 0.00001	p > 0.05	p < 0.00001	p > 0.05	p < 0.01	p > 0.05
FEgg-F2	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.00001	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p > 0.05
FEgg-F3	p < 0.00001	p > 0.05	p > 0.05	p < 0.01	p < 0.00001	p < 0.00001	p < 0.00001	p > 0.05	p < 0.0001	p < 0.0001	p < 0.0001
FEgg-F4	p < 0.00001	p < 0.01	p < 0.01	p < 0.00001	p < 0.00001	p < 0.00001	p < 0.00001	p < 0.0001	p < 0.0001	p < 0.00001	p < 0.00001
FEgg-F5	p < 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.0001	p < 0.0001	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p > 0.05
F1-F2	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.00001	p > 0.05	p > 0.05	p < 0.00001	p < 0.01	p > 0.05	p > 0.05
F1-F3	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.05	p < 0.00001	p > 0.05	p > 0.05	p > 0.05
F1-F4	p < 0.001	p > 0.05	p > 0.05	p < 0.05	p < 0.05	p < 0.00001	p < 0.001	p < 0.05	p > 0.05	<0.0001	p < 0.0001
F1-F5	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.01	p < 0.05	p > 0.05	p < 0.00001	p > 0.05	p > 0.05	p > 0.05
F2-F3	p < 0.01	p > 0.05	p > 0.05	p > 0.05	p < 0.00001	p < 0.05	p < 0.05	p > 0.05	p < 0.00001	p < 0.05	p < 0.01
F2-F4	p < 0.00001	p > 0.05	p > 0.05	p < 0.0001	p < 0.00001	p < 0.00001	p < 0.01	p < 0.00001	p < 0.00001	p < 0.00001	p < 0.00001
F2-F5	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.01	p > 0.05	p > 0.05	p > 0.05	p < 0.05	p > 0.05	p > 0.05
F3-F4	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.00001	p > 0.05	p < 0.01	p > 0.05	p < 0.01	p > 0.05
F3-F5	p > 0.05	p > 0.05	p > 0.05	p > 0.05	p < 0.00001	p < 0.00001	p < 0.01	p > 0.05	p > 0.05	p > 0.05	p > 0.05
F4-F5	p < 0.00001	p < 0.01	p > 0.05	p < 0.001	p < 0.00001	p < 0.00001	p < 0.0001	p < 0.0001	p > 0.05	p < 0.0001	p < 0.0001

Note: FEgg (FreshEggs), ¹F1, F2, F3, F4, F5: Chicken Eggs Farm; p > 0.05-Not significant; p < 0.05-Significant; p < 0.01-Fairly significant;

p < 0.001-Highly significant; p < 0.0001-Very highly statistically significant; p < 0.00001-Profoundly significant

All groups (F1 to F5) exhibit significantly lower mean egg weights than FreshEggs. The lowest mean egg weight is observed in group F4 (56.98 g), while the highest is found in group of FreshEggs (66.95 g). The p-values (<0.00001) indicate a highly significant difference in egg weight mean across the groups (Table 2). Comparing fresh eggs to other groups reveals statistically significant differences in average egg weight. The FreshEggs-F4 pair demonstrates the most substantial difference (p < 0.00001), suggesting a profoundly significant result. However, pairs such as FreshEggs-F2, F1-F2, F2-F3, F1-F5, F2-F5, F3-F4, and F3-F5 have p-values greater than 0.05 (p > 0.05), indicating no significant difference between their means (Table 3).

In summary, the analysis suggests that there are significant differences in eggs weight means for some pairs, while others do not show statistically significant distinctions. The mean egg weight in the research follows the standard egg weight (58 to 62 g) reported by other studies (Eke et al.,^[18] Hartmann et al.,^[34] Rath et al.^[23]). Also, the higher and lower values for egg weight, egg weight loss and the factors affecting them have been reported by previous studies (Eke et al.,^[18] Harnsoongnoen and Jaroensuk,^[19] Kocetkovs et al.,^[8] Nonga et al.,^[35] Rath et al.,^[23] Samli et al.,^[24] Sreenivas et al.^[36]). The factors influencing the weight of hens’ eggs, such as food, hen weight, genetic and environmental factors, temperature and storage time, sanitary conditions in farms and their relationship with egg weight have been reported by different studies (Ahmadi and Rahimi,^[28] Ledvinka et al.,^[37] Peebles et al.,^[38] Rath et al..^[23]

Evaluating mean weight of the eggshell, group F3 has the lowest eggshell weight (6.61 g), while F5 has the highest (7.94 g), but all are lower than Fresh Eggs (7.98 g) (p < 0.01) (Table 1). The Egg shells weight of the compared groups does not exhibit a statistically significant difference, as indicated by the p-values for all pairs being generally over p > 0.05 (Table 2). The pair FreshEggs-F4 and F4-F5 has the lowest p-value (p < 0.01), indicating a fairly significant result compared to the other pairs. In contrast, most other pairs, such as FreshEggs-F1, FreshEggs-F2, FreshEggs-F3, etc., do not show statistically significant distinctions between their means (p > 0.05) (Table 3). As for the evaluating of eggshell mean thickness in micrometers (µm), it is evident that F2 has the thickest eggshell (0.45 µm), while F4 displays the thinnest (0.38 µm). The p-values, which are less than 0.0001, strongly suggest a highly significant difference in eggshell thickness among the different groups (Table 2). The analysis reveals highly significant variations in eggshell thickness means among specific pairs, notably EggsFresh-F3 and EggsFresh-F4 (p < 0.0001), indicating a very strong statistical significance. Additionally, pairs F2-F3 and F2-F4 exhibit even more profound significance, with p-values below 0.00001. Conversely, other pairs do not show statistically significant differences (p > 0.05) (Table 3). The results of our research are in line with other studies, who have reported on the evaluation of external and internal parameters of egg quality and the factors that influence these parameters.^{[8,23,24,37,39–41]}

Exploring egg yolk weights across diverse groups (F1, F2, F3, F4, F5, and Fresh Eggs) reveals that F4 exhibits the lowest mean yolk weight (13.40 g), with F2 presenting the highest (14.80 g), although all values remain below that of Fresh Eggs (15.32 g) (p < 0.01) (Table 2). Statistical analysis indicates no significant difference in the mean egg yolk weight among the compared groups, as evidenced by p-values predominantly exceeding 0.05. Notably, a fairly significant difference in means is observed for the FreshEggs-F4 pair (p < 0.01), while the remaining pairs do not display statistically significant distinctions (Table 3). Regarding yolk color (Roche Yolk Color-RYC), Fresh Eggs and F5 exhibit the highest values (12.71 RYC and 12.31 RYC, respectively). The p-values, which are less than 0.00001, indicate an exceedingly significant difference in yolk color among the groups. (Table 2). Examining the data further, profound variations in the mean of egg yolk color are observed for specific pairs: EggsFresh-F1, EggsFresh-F4, F1-F2, F1-F3, F1-F5, F2-F4, and F4-F5 (p < 0.00001). Conversely, no statistically significant differences are detected in the pairs EggsFresh-F2, EggsFresh-F3, EggsFresh-F5, F2-F3, F2-F5, and F3-F5 (p > 0.05) (Table 3). Higher values of egg yolk weight, colour index and factors that influence losses in weight and colour index have also been reported by previous research (Dilawar et al.,^[1] Gultemirian et al.,^[42] Stadelman and Cotterill,^[29] Sokołowicz et al..^[43]

Evaluating Egg White Weight reveals consistently lower values across all groups compared to Fresh Eggs (p < 0.0001) (Table 2). Significant and fairly differences in the mean weight of the egg white are observed for the pairs FreshEggs-F1 (p < 0.05) and FreshEggs-F3 (p < 0.01). Notably, the pair FreshEggs-F4 stands out with a Profoundly significant difference (p < 0.00001). While other pairs did not show statistically significant differences in means (p > 0.05) (Table 3). Similar results on egg white weight and HU and the factors influencing these egg quality parameters were also reported by Nolte et al.,^[44] Rath et al.,^[23] Samli et al.,^[24] Sokołowicz et al.,^[43] Scott et al.,^[45] Stademan and Cotterill.^[29]

In terms of Specific Gravity, F5 demonstrates the highest value (1.076 g/cm3), yet all groups exhibit values which are lower than of FreshEggs (1.086 g/cm3) (p < 0.00001) (Table 2). The analysis results indicate significant differences in the means for all pairs, each exhibiting varying degrees of significance (p < 0.05). Notably, the FreshEggs-F3 and FreshEgss-F4 pairs attains the highest significance levels (p < 0.00001), signifying a profoundly significant difference (Table 3). Similar results about the specific weight and the factors affecting its loss (especially the influence of temperature and storage time) have been reported by other studies.^[23,24]

Commencing with Haugh Unit (HU), it is noteworthy that FreshEggs exhibit the highest Haugh unit, indicating superior egg quality (91.20 HU). F5 follows with the second-highest Haugh unit (80.94 HU), as reflected by a highly significant p-value (<0.00001) (Table 2). Profoundly significant differences in means for the Haugh unit values (HU) are observed for all pairs. The analysis showed that most pairs exhibit statistically significant differences in means (p < 0.00001). Some pairs, such as FreshEggs-F1, FreshEggs-F2, FreshEggs-F3, FreshEggs-F4 and FreshEggs-F5, showed highly significant variations (p < 0.00001). Whereas, the pairs F1-F2, F1-F3, and F2-F5 did not exhibit statistically significant differences in means (p > 0.05). (Table 3). Factors influencing this egg quality parameter (HU) were also reported by Rath et al.,^[23] Samli et al.^[24] Previous researchers have reported that the Haugh units (HU) of eggs range from 72–110 (Eke et al.,^[18] Stademan and Cotterill^[29]).

Embarking on the analysis of air cell size reveals noticeable variations. Notably, F4 showcases the largest air cell (6.21 mm), contrasting with F5, which presents the smallest (4.22 mm). It is noteworthy that all groups display air cells larger than those found in FreshEggs (3.44 mm) (p < 0.0001) (Table 2). Also, he results of the study showed statistically significant differences regarding Air cells between the mean of some different pairs, while others do not, based on the chosen level of significance (more than p < 0.01) (Table 3). The pair FreshEggs-F3 and FreshEggs-F4 show profoundly significant differences (p < 0.00001). The pair F1-F4 has a particularly low p-value (p < 0.001), indicating a highly significant difference between their means. Conversely, several pairs, including FreshEggs-F1, FreshEggs-F2, and FreshEggs-F5, have p-values greater than > 0.05, indicating no significant difference between their means. Lower and higher values of Air cell in eggs and the factors that affect the deterioration of this important parameter for determining the quality of eggs for consumption and use in the food industry have been reported by previous findings (Eke et. al,^[18] Harnsoongnoen and Jaroensuk,^[19] Rath et. al.,^[23] Samli et. al.,^[24] Stadelman and Cotterill^[29]).

In terms of Egg Length (mm) and Egg Width (mm), it’s evident that FreshEggs surpass other groups with the largest measurements in both length and width (57.43 mm length and 44.81 mm width) (Table 2). The analysis reveals significant differences in the mean length of eggs for specific pairs, while noting nonsignificant differences for others. (Table 3). Pairs FreshEggs-F4 and F2-F4 show profoundly significant distinctions (p < 0.00001). Whereas pairs like FreshEggs-F2, FreshEggs-F5, F1-F2, F1-F3, F1-F5, F2-F5 and F3-F5 exhibit no significant mean differences (p > 0.05). As for the width of the eggs, the analysis indicates significant differences in means for some pairs, while others do not show statistically significant distinctions. The pair FreshEggs-F4 has the largest difference, with a p-value of p < 0.00001, suggesting a profoundly significant result. The pairs FreshEggs-F1, FreshEggs-F2, FreshEggs-F5, F1-F2, F3-F5, F1-F5, F2-F5, F3-F4 and F3-F5 do not show statistically significant differences (p > 0.05). Our research’s findings are consistent with those of other studies that have examined the assessment of internal and external egg quality measures as well as the factors influencing these parameters (Rath et al.,^[23] Kocetkovs et al.,^[8] Sokołowicz et al.^[43]). In general, the data suggests significant differences in various egg parameters among groups, with FreshEggs generally exhibiting superior characteristics.

Table 4 presents Pearson correlation coefficients between various external and internal quality parameters of eggs. Each cell in the table represents the correlation coefficient between two specific parameters, such as egg weight, eggshell weight, egg yolk weight, egg white weight, specific gravity, Haugh unit (HU), air cell size, Roche Yolk Color, eggshell thickness, egg length, and egg width. The significance levels (P-values) are also provided, and some of the main findings are interpreted below.

Table 4. Pearson correlation matrix (r) for key egg quality parameters.

Parameters	Egg weight g	Eggshell weight g	Egg yolk weight g	Egg white weight g	Specific Gravity g/cm3	Haugh unit (HU)	Air cell	Roche Yolk Color	Egg Shell Thickness µm	Egg length mm	Egg width mm
Egg weight g	1	.935**	.972**	.997**	.951**	.969**	−.957**	.626	.954**	.990**	.984**
Eggshell weight g		1	.870*	.917*	.972**	.938**	−.977**	.576	.905*	.885*	.891*
Egg yolk weight g			1	.962**	.890*	.923**	−.932**	.482	.938**	.964**	.984**
Egg white weight g				1	.941**	.965**	−.936**	.662	.945**	.995**	.980**
Specific Gravity g/cm3					1	.984**	−.952**	.672	.875*	.904*	.888*
Haugh unit (HU)						1	−.947**	.645	.863*	.940**	.920**
Air cell mm							1	−.460	−.915*	−.919**	−.941**
Roche Yolk Color								1	.581	.626	.518
Egg Shell Thickness µm									1	.944**	.961**
Egg length mm										1	.988**
Egg width mm											1

Note; **Correlation is significant at the p < 0.01 level.

*Correlation is significant at the p < 0.05 level.

Egg weight demonstrates exceptionally strong positive correlations (p < 0.01) with eggshell weight (r = 0.935), egg yolk weight (r = 0.972), and egg white weight (r = 0.997). This suggests that heavier eggs tend to have proportionally heavier eggshells, yolks, and egg whites. This highlights a remarkable synchrony in the growth of these components within the egg. Our findings of a positive correlation between egg weight and other parameters and no significant correlation between egg weight and Specific Gravity, Haugh unit and Egg Shell Thickness are consistent with the findings of other findings.^[46,47]

Eggshell weight exhibits a robust positive correlation (p < 0.01) with egg weight (r = 0.935) and a significant positive correlation (p < 0.05) with egg white weight (r = 0.917), indicating a proportional relationship between these parameters. This implies a structural interdependence, where the overall weight of the egg, particularly the egg white, is mirrored in the eggshell. A strong positive correlation between Egg yolk weight and Egg weight and Eggshell weight has been found in previous studies reported by Inca et. al.^[47]

Egg yolk weight displays strong positive correlations with egg weight (r = 0.972) and egg white weight (r = 0.962), emphasizing a coordinated development of the yolk alongside the overall egg and its albumen content (p < 0.01). Results from earlier research showed a significant positive association between egg yolk weight and egg weight.^[47]

Strong positive correlations (p < 0.01) have been found between specific gravity and many parameters, including egg white weight (r = 0.941) and the Haugh unit (r = 0.984). These correlations imply that eggs with greater specific gravities have superior quality and denser albumen, as indicated by the Haugh unit. Our findings confirm the considerable positive link previously seen between albumin, specific weight, and other measures.^[47–50] Nonetheless, it was stated that the Haugh unit was dependent on albumen height but independent of egg weight.^[46,48]

The air cell demonstrates strong negative correlations (p < 0.01) with various parameters, notably with egg weight (r = −0.957) and eggshell weight (r = −0.977). This suggests that lighter eggs and thinner shells are linked to larger air cells. Our findings are in harmony with the findings reported by other authors.^[51,52] Egg Shell Thickness reveals a robust positive correlation (p < 0.01) with egg weight (r = 0.954) and egg yolk weight (r = 0.938), underscoring a concurrent strengthening of the eggshell structure as eggs increase in size. An important and strong association between egg shell thickness and eggshell weight, egg yolk weight, and specific gravity was found in the earlier study conducted by Inca and associates.^[47]

Egg length and egg width demonstrate a strong positive correlation (r = 0.988) with each other and with most other parameters (p < 0.01), suggesting a consistent growth pattern where larger eggs tend to be elongated while maintaining proportionality in structure. Significant positive correlations between egg length, breadth, and weight have also been found in earlier studies.^[46,47] It has also been found and reported that there is a substantial negative association between specific gravity and egg length.^[46] The study did not discover any meaningful relationships between the color of the yolk and the other assessed parameters of egg quality.

Conclusion

The increase in egg production in Kosovo is crucial as it contributes to the development of the poultry industry and enhances the country’s economy. Simultaneously, heightened dedication from regulatory bodies is essential to consistently oversee egg production and marketing for human consumption and utilization in the food industry, ensuring adherence to farm hygiene standards. The investigation examined multiple quality indicators to assess egg quality for consumption and industrial use. Results revealed significant variations among farms, indicating potential implications for hen management and feed practices. The study results classified egg quality into two categories, aligning with local Administrative Directive (AD No. 17/2008) and European regulations (EC No. 589/200) for determining egg quality. The majority of egg groups from different farms met the freshness criteria outlined for Class “A” under regulations. However, a specific group of eggs (F4) was classified as Class “B,” reserved for industrial processing. This classification resulted from the primary criterion of air cell quality, as outlined in the regulations, surpassing the specified limit of 6 mm. According to regulations, the air cell of Class “A” eggs should not exceed 6 mm, and for eggs categorized as “extra” class, the air cell should not be over 4 mm. Fresh eggs and eggs from groups F1, F2, F3, and F5 adhered to the standards and legal requirements for egg quality. On the flip side, eggs from group F4 surpassed the mean values specified for air cells, as per regulations. The comprehensive offers valuable insights for consumers, producers, and regulatory bodies, aiding in enhancing quality standards and promoting fair competition in Kosovo’s egg market. Further research and collaboration with farms may uncover contributing factors to these variations.

Acknowledgments

The authors express gratitude to Mrs. Flutra Mestani for her assistance in technical and analytical aspects, including the formatting of statistical results and grammar. The authors are thankful to the Researchers Supporting Project number (RSPD2024R923), King Saud University, Riyadh, Saudi Arabia.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.