RICERCA ITALIANA     

EGG PRODUCTION CHAIN: FROM HEN WELFARE TO QUALITY AND SAFETY OF EGGS AND DERIVED FOOD PRODUCTS

Università degli Studi di Milano

Abstract

Consumers are becoming more and more aware of farmed animal welfare, considering it as a major factor affecting food quality and safety. Therefore organic and other alternative egg production methods are now spreading throughout Italy and Europe. In order to ensure that the consumer is able to make an informed choice between the various classes of egg on the basis of the farming method, the EC Commission made it compulsory the indication of the farming method on class A eggs. From January 2004, the following numeric codes are directly stamped on eggs: 0, organic production; 1, free range; 2, barn; 3, cage. Considering the higher selling price of eggs produced through alternative farming methods, consumers have the right to make an informed choice also on the basis of a real quality to price ratio. Actually, a thorough and organic study on hygienic, nutritional, functional and sensorial quality of eggs as affected by farming methods is lacking in the literature. The aim of the project is to fill this scientific gap, considering the whole hen egg production chain, starting from animal welfare to quality and safety of eggs and derived food products. Four Research Units (RU), with specific skills either in poultry production or in food quality and safety, will work together in order to achieve the research aim over a period of two years. UNIMIvet RU will compare production performances and physiological and behavioural features of laying hens either farmed in an organic production system (with available open runs) and in a deep-litter floor system (barn). Hen behaviour will be recorded through video cameras and other electronic devices purposely installed at farms strategic points. The whole hen laying cycle will be recorded. The task of UNIMIagr RU will be the evaluation of hygienic, compositional, functional and sensorial characteristics of egg samples collected at the farms just described, focusing in particular on the comparison of eggs from deep-litter barn system with those from conventional cage system produced by the same farmers. In order to take a picture of the quality of eggs reaching the market and consumers, UNIMIagr RU will also evaluate and compare the quality and safety characteristics of eggs marketed in northern Italy and labeled with the indication of the various farming methods, according to recent European regulations. UNIBO RU will take into consideration either three organic farms and three farms with conventional cages. Microbial profiles of environment and eggs will be evaluated at farms, over the whole hen laying cycle. Moreover the hygienic, compositional, functional and sensorial characteristics of egg samples collected at organic farms will be compared with those of eggs from conventional cage farms. With the aim of comparing organic and cage eggs, UNIBO RU will also thoroughly investigate the composition of egg lipid fraction and its modification during storage at the various steps of the production chain: fresh shell egg, pasteurized egg products (both liquid and spray dried), and finished foods (dried egg pasta and biscuits produced by UNICB RU). UNICB RU will evaluate the compositional-nutritional characteristics of egg products obtained from organic, barn, and cage eggs supplied by UNIMIvet and UNIBO RUs. Other tasks of UNICB RU will be the production of finished foods at pilot plant level and the identification and quantification of process-product markers for raw materials (eggs) and intermediate products (egg products), and for the derived finished products. Furosine, lysine, retinols, carotenoids, tocopherols, and lysozyme will be considered among the possible markers. <<<

Principal Investigator

Margherita ROSSI Università degli Studi di MILANO

Research Objectives

Poultry production has a relevant role in Italian animal production due to its economic impact and to its ability to adapt to market and consumer demands. In these last years food safety and "naturalness" are becoming more and more important consumer claims. This promoted the development of different production methods able to satisfy consumer requests about product quality but also to take into consideration animal welfare and environment in the whole production chain.
Aim of the project is to consider the entire egg production chain, from hen rearing to finished food products, of which egg is a characterizing ingredient. The scope is to evaluate the influence of farming methods and production technology both on hen welfare and on quality of eggs and of their derived products. The researchers joining the project are proficient either in poultry production or in food technology and food quality evaluation. Their skills complement each other to cover the whole production chain.
Research targets can be roughly summarized in the following points.
1. Morpho-physiological and behavioral features of hens reared by alternative methods (organic production and deep-litter barn method), with regards to poultry welfare.
2. Evaluation of production performances of hens reared by different farming methods (organic production, barn, and cage).
3. Evaluation of the effects of the farming method on the microbial population of poultry house (organic and cage production).
4. Evaluation and comparison of morphological, hygienic, compositional, functional and sensorial characteristics of eggs sampled from different farming methods (organic, barn and cage).
5. Evaluation and comparison of morphological, hygienic, compositional, functional and sensorial characteristics of commercial eggs, labeled with the indication of farming method.
6. Assessment of the influence of production technology on egg products obtained from organic and conventional eggs.
7. Characterization of the lipid fraction of organic and conventional eggs throughout the production chain, including pasteurization treatments, egg product storage and their use in finished food products, whose shelf life will be also considered.
8. Chemical, nutritional and microbiological characterization during shelf life of intermediate products (egg products) and finished products (dried egg pasta and biscuits) obtained from eggs produced by conventional and alternative methods.
9. Identification and quantification of process-product markers in intermediate and finished food products produced with eggs from conventional and alternative farming methods.
10. Statistical processing of results in order to evaluate any significant influence of hen farming method on poultry welfare and on the quality of eggs, egg products and finished food products.

RUs involved in the coordinate project will participate to the achievement of the exposed research targets according to their specific skills, equipment and facilities. In particular:
UNIMIagr will coordinate the project and fulfill targets 4., 5. and 10.;
UNIMIvet will fulfill targets 1. and 2.;
UNIBO will fulfill targets 2., 3., 4., 6., 7.;
UNICB will fulfill targets 6., 8., 9..
The described targets will be reached gradually accordingly to timing and requirements of poultry rearing that are conditioned by hen housing starting time and laying cycle. At the end of the first year, partial results related to the different farming methods will be available.
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First Results

Expected results will be in accordance with the proposed targets.
- As far as regards animal farming: They will be identified the factors involved in hen welfare and productivity, microbial habitat contamination, egg safety and quality which are affected by the different farming methods (organic, barn, cage).
- As far as regards marketed eggs: a picture will be taken of the safety and quality level of eggs bearing the indication of the farming methods, in accordance to recent EU regulations. This will supply the consumers with the scientific basis for an informed choice.
- As far as regard egg products and final foods, the following will be the expected results:
1. The identification of lipid fractions and other nutritive egg components (vitamins, and so on) which are affected by hen farming methods (organic, barn, cage).
2. The knowledge of the modifications occuring to such components as a consequence of the technological processes applied during the manufacture of both egg products and final foods, and their implications in products shelf life.
3. The identification of product and process markers to be used either as methods for the control of egg products, processes and egg derived foods, and as means for adding value to and protect premium quality food products. <<<

Timescale

24 months

National and international background

Poultry production system is a very specialised and industrialised activity based on the use of birds of highly productive strains reared at high stocking density in poultry houses, suited to maximize egg production and equipped with modern facilities, where temperatures and humidity are automatically controlled.
Last years have been characterized by a progressive development of new farming systems aiming to produce higher quality eggs and to warrant a better hen welfare. Likewise the consumer requests are moving in the direction of new products obtained through extensive rearing systems or through "more natural" methods in bird keeping. In response to this demand the EU issued the Regulations 1804/99 concerning the organic animal production. Moreover in the 1999 EU also approved the Directive 74/99 regarding the laying hen welfare. According to this Directive the use of cages will be banned from 2012 and new rearing systems for hens, such as furnished cages (perch + nest + sand bath) or systems alternative to cages will be adopted. The indication of hens farming method is reported on package and stamped on eggs as specified by the recent labelling regulation in force from January 2004. This compulsory labelling is in line with the wishes expressed by consumers and consumer organisations and complete traceability of egg production.
These new production systems aim to reach several purposes such as a higher welfare for birds, good environment preservation by tightening the link between animal and vegetable productions, a higher quality, hygiene and a better appeal of the products. Laying hens in alternative and organic farming have some advantages compared to hens in intensive husbandry. For instance, freedom is one of the positive aspects of the welfare of free-living and free-range animals. Nevertheless many welfare problems are involved in organic laying hens production: first of all the evaluation of the adaptability to extensive systems of commercial hybrid strains selected for intensive systems.
Alternative eggs productions need to be accurately studied for better understanding the factors influencing birds' welfare and eggs quality, considering that different researches on this subject often report contrasting results. Laying hen behaviour will be monitored in order to study the differences between litter floor and organic housing. It is important to investigate morpho-physiological parameters directly correlated to hen behaviour (level of activity and aggressiveness). At the same time egg characteristics directly correlated to hen activity and free-range life must be investigated. Research works highlight the interactions among feeding, thermal and hygrometric conditions and the quality of production of hens, belonging to different genotypes (Leyendecker et al., 2001).
Since the organic method is quite different from the conventional intensive cage system both for animal care and diet composition of hens, we presume that organic egg quality is quite different from that of conventional eggs. For instance, the possibility to have access to different vegetable feed sources in open-air runs increases the carotenoid content of yolk (Kouba, 2002). According to poultry farmers, organic eggs have better nutritional, functional and technological characteristics (particularly for pasta production) compared to the conventional eggs (Seghezzi, 2002). However at present, data coming from scientific experiments are lacking and absolutely incomplete either for the quality characteristics of organic eggs and for the effect of the rearing systems on the physical-chemical and microbial contamination of poultry houses or on the production performances of hens.
Actually, a different sensory, nutritional, and hygienic quality of eggs from alternative farming methods is still to be demonstrated. Published works concerning this subject are relatively rare and report conflicting results. Indeed the farming method is only one factor out of those affecting the traits of eggs. Genetic factors and feed also have considerable effects. Therefore rigorous comparisons should be based on researches carried out with hens of the same breed, age, and receiving the same feed (Sauver, 1991), although this is difficult to attain in practical farming conditions. Sauver (1991) reviewed the results of a number of studies aiming to compare the traits of eggs from cage-housed or barn-housed hens. The Author inferred that rearing method permanently modifies neither egg weight, nor overall composition. A tendency (rarely significant) to produce eggs with higher content of linoleic acid and cholesterol was found for barn-housed hens. Wegner et al. (1982) report small differences in egg quality ascribed to housing conditions, and no difference of taste and flavor. However, they observe an increase in the frequency of dirty eggs and in the microbial contamination of shells in eggs obtained with alternative farming methods.
Regarding eggshell quality, Cholocinska & Rozycka (1987) report higher shell strength and lower percentage of cracked eggs in barn eggs than in cage produced eggs. Besides, egg inner quality traits, such as yolk weight (Korenblik & van Niekerk, 1992; Cavalchini & Cerolini, 1984) and the presence of blood and meat spots (Mench et al., 1986) provide no definitive results. For other parameters, such as albumen height and Haugh Units, results in the literature (Appleby et al., 1988; Korenblik& van Niekerk, 1992) are contrasting, being related with egg freshness rather than with the method of farming.
If, as stated above, it is important to obtain scientific results based on rigorously run experiments that minimise the influence of variables other than the farming method; on the other hand the check of the features of marketed eggs is as much important. Such check is a dutiful reply to the expectations of the consumers who pay an extra charge to buy eggs, such as organic eggs, which they consider fresher, safer and more nutritious and tasteful (Hidalgo & Rossi, 2003). From this point of view, the importance of other factors, influencing egg quality but not directly related to the farming method, as for instance the collection and distribution of eggs, cannot be overlooked. A study on the quality and price of the eggs (both alternative and conventional) marketed in the USA (Patterson et al., 2000) and purchased at supermarkets shows that alternative eggs (named specialty eggs) are older and have lower albumen height, while having a similar percentage of cracked eggs. Among specialty eggs, organic eggs show poorer inner quality, included albumen height and Haugh Units. All of this with a price definitely higher than that of conventional eggs.
Egg is a fundamental ingredient for food preparation as pasta, mayonnaise, bakery products, ice creams etc. Due to this fact, the use of industrial egg products is increasing, since their characteristics, composition and hygienic quality are standardized. The wide spreading of egg use for industrial preparations has highly increased the demand for egg products, which, besides providing high convenience, better satisfy the safety requirement of the food industry. Italy, among European Countries, presents the highest use of egg products (36% of total consumed eggs). This peculiarity is due to many products of the gastronomical tradition, such as egg pasta and festivity cakes, in which the minimum amount of egg product is established by law (pasta) or by traditional recipes.
The sanitary-hygienic regulations and the analytical characteristics of the egg products are ruled by the DL 65/93 law. To avoid microbial contamination in dehydrated or frozen eggs, pasteurization should be performed; in fact, dehydrated eggs that have not been subjected to thermal treatment can present Salmonella growth. In egg products and finished products, in which eggs are a major ingredient, like egg pasta and baked products, lipids are present in high quantity and undergo alternating thermal treatments and storage periods. Lipid preservation status is therefore of great importance in defining quality and shelf life of food products. Modifications that can mainly occur are degradation of the triglycerides, fatty acid and cholesterol oxidations and phosholipid modifications. In particular lipids can react with oxigen, forming peroxides that can generate oxidation secondary products, causing oxidative rancidity.
Cholesterol can react with oxygen, following the same reaction mechanisms observed for the monounsaturated fatty acids. Despite the reaction mechanisms are the same, cholesterol oxidation does not generate volatile molecules and does not cause the modification of the organoleptic profile of the food products. Nevertheless, a high number of cholesterol oxidation products (COPs) have been identified and many of them show atherogenic, cytotoxic and carcinogenic effects. The determination of lipid oxidation status and of COPs is, therefore, necessary for a complete evaluation of the quality of the raw materials and the effects of processing and storage conditions on products with high cholesterol content, such as those prepared with eggs. Phospholipids accounting for about 30% of egg lipid fraction exhibit great emulsifying properties due to their chemical structure. Moreover, recent researches highlighted their antioxidant properties and their reactivity with Maillard reaction product (Utzman and Lederer, 2000).
Quality of egg-based products is linked to both hygienic and nutritional characteristics of eggs. From a nutritional point of view are relevant both quantity and quality of nutrients (as assessed on fresh and preserved products) and the presence of undesirable neoformation compounds. It must be verified how peculiar characteristics of raw material are conveyed to finish products. For instance, preliminary experiments show how egg pasta quality, regarding cholesterol fraction, is influenced by egg kind, traditional or organic (Boselli et al., 2004).
The characterisation of a food through objective and analytically measurable parameters is of great importance for the product valorisation and for its defence on the market. Through these descriptors is possible to establish quality classes, to assess genuineness, to ascertain the correct denomination of many foods and to determine ingredients and transformation processes. To this purpose it seems significant to identify and to determine product and process markers in order to monitor the entire production process of pasta and bakery products, from egg to finished products. In the first case, molecules characteristic of a particular product or of an ingredient can be assumed as the product marker. In the second case, markers can be represented either by newly formed molecules coming from reactions induced by the process, or by molecules naturally present in the food and modified by technological process. As for egg products, dried egg-pasta and bakery products, the descriptors for pasteurization of liquid egg-product, egg drying and pasta making (high and low drying temperatures) will be the newly formed substances produced during the first step of Maillard reaction (e.g. furosine). Besides, the degradation/modification of substances naturally present in semolina or eggs, such as lysine, lysozime, reducing sugars, retinols, tocopherols and tocochromanols, and carotenoids, can be considered as process markers.
Although the Maillard reaction is typically favoured by the severity of the thermal treatment, also low temperature (room temperature) for long time allows the first stage of the reaction to have place. For this reason, furosine can be used as a shelf-life index for foods such as milk and dairy product, semolina, dried pasta, tomato, royal jelly, and as freshness index of eggs (Resmini et al., 1990a; Resmini et al., 1990b; Hidalgo et al., 1998; Marconi et al., 2002, Hidalgo et al., 1995). The Maillard reaction in eggs can involves aminoacids and also NH2 groups of aminophospholipids, which are present in a relevant amount in egg yolk (12%). The aminophospholipids can react with reducing sugars to origin intermediate compounds different from the Amadori compound identifiable through furosine. Such compounds may result as useful additional markers of non-enzimatic browning. Egg vitamins, studied in the research project, are tocochromanols, retinols and carotenoids. Besides being natural antioxidants, these compounds exhibit health benefits towards several degenerative diseases. Several reports show losses of vitamin E activity during the storage of egg products and egg-based foods, and carotenoid losses due to the action of enzymes catalyzing peroxidation of polyunsaturated fatty acids (Wahle et al, 1993). The degree of antioxidants loss depends on processing conditions, therefore the amount of these compounds could be useful for the identification of the ingredients used and of the processing conditions applied, and for the assessment of nutritional, technological and commercial quality of ingredients and foods. <<<