Improving the Safety and Quality of Eggs and Egg Products

Egg Safety and Nutritional Quality

F Van Immerseel, Y Nys, M Bain, F Van Immerseel, Y Nys, M Bain

• Publisher: Woodhead Publishing
• Year: 2011
• ISBN:
  9780857093929
• Topic: Tecnologia e ingegneria
• Subtopic: Scienze dell'alimentazione

Eggs are economical and of high nutritional value, yet can also be a source of foodborne disease. Understanding of the factors influencing egg quality has increased in recent years and new technologies to assure egg safety have been developed. Improving the safety and quality of eggs and egg products reviews recent research in these areasVolume 2 focuses on egg safety and nutritional quality. Part one provides an overview of egg contaminants, covering both microbial pathogens and chemical residues. Salmonella control in laying hens is the focus of part two. Chapters cover essential topics such as monitoring and control procedures in laying flocks and egg decontamination methods. Finally, part three looks at the role of eggs in nutrition and other health applications. Chapters cover dietary cholesterol, egg allergy, egg enrichment and bioactive fractions of eggs, among other topics.With its distinguished editors and international team of contributors, Volume 2 of Improving the safety and quality of eggs and egg products is an essential reference for managers in the egg industry, professionals in the food industry using eggs as ingredients and all those with a research interest in the subject.

• Focuses on egg safety and nutritional quality with reference to egg contaminants such as Salmonella Enteritidis
• Chapters discuss essential topics such as monitoring and control procedures in laying flocks and egg decontamination methods
• Presents a comprehensive overview of the role of eggs in nutrition and other health applications including dietary cholesterol, egg allergy, egg enrichment and bioactive fractions of eggs

Part I

Microbial and chemical contamination of eggs

1

Microbiology and safety of table eggs

M.T. Musgrove, United States Department of Agriculture, USA

Abstract:

This chapter describes the microbiology of table eggs, effects of processing, regulatory influences, relative risk of egg-borne disease, and the role of retail and consumer practices in outbreaks. Effects of washing, refrigeration, and facility sanitation in US commercial facilities will be described and their contribution to shelf-life and food safety will be discussed. Current regulations, recent changes, and the influence of Safe and Quality Foods (SQF), a voluntary program required by some retailers, are described. A general discussion of table egg microbiology, pathogens, and emerging pathogens is followed by a description of sampling methods. Finally, the relative risk of egg-borne illness in the US and the contribution by retail and consumer practices will be discussed.

Key words

table eggs

table egg microbiology

table egg sanitation

table egg processing

table egg safety

1.1 Introduction

Eggs, a nutritious and inexpensive food, are an important part of human diets worldwide (McNamara, 2003). Modern operations allow for the washing and packaging of thousands of eggs an hour (Klippen, 1990). Since large-scale operations became prevalent in the 1970s, there have been many modifications to the process (Moats, 1978; Hutchison et al., 2003). Understanding how shell egg microbial populations are affected by processing (washing, grading, packing) is important to ensuring product quality and safety.

1.1.1 United States table egg industry

In the early 1900s, 90% of US commercial eggs were produced on multipurpose farms by 100–300 birds that roamed freely, fed with waste grain, insects and forage (Bell 1995, 2002). After World War II, farms became modernized, and flock sizes were increased to take greatest advantage of efficient systems (Bell, 2002). Multiple-tier cages became common and came equipped with automated transport belts for gathering eggs. Currently, more than 80% of US eggs are gathered by this method (Fig. 1.1). Mechanical feed and watering devices are present in 90% of layer houses. Temperature, humidity, feed intake, water consumption, and all other mechanical operations are electronically monitored. These conditions allow egg companies to employ only 15 persons per million hens. Prior to environmentally controlled housing, eggs were only produced in the spring and summer months. After eggs had been separated according to cleanliness and size, washed and clean eggs were stored until needed for retail. Today, eggs are now transported to retail outlets almost as soon as they are packaged (Stadelman, 1995; Bell, 2002; Zeidler, 2002).

Fig. 1.1 Inline shell egg layer house and plant layout.

Modern equipment for washing, candling, sizing, and packaging can handle over 180,000 eggs per hour. Photographs and a diagram of this type of operation are depicted in Fig. 1.1.

As late as the 1950s, it took egg producers most of their time to clean, size, and pack eggs. Production was ~ 1.4 cases/person hour (1 case = 360 eggs). Eggs that are transported to processing and packaging rooms by conveyor from hens housed in buildings attached to the processing facility are known as ‘in-line’ eggs. Eggs that are transported from remote housing are known as ‘off-line’ eggs. Conveyor systems, mass candling, automatic check (crack) detection, and electronic egg scales with computer controls have allowed for the transformation in production capacity (Zeidler, 2002; Curtis, 2002; Curtis et al., 2004) (Fig. 1.2).

Fig. 1.2 Schematic of shell egg processing facility.

Per capita egg consumption has also undergone a great deal of change. Highest per capita egg consumption was in 1945 at 402 while the nadir occurred in 1991 at 233.9 eggs. Health concerns associated with egg-related outbreaks of salmonellosis caused by Salmonella Enteritidis and a desire to reduce cholesterol intake are regarded as the principal reasons for the decline. Currently, most nutritionists and medical doctors recommend daily egg consumption. In 2009, per capita egg consumption was 247.7 (American Egg Board, 2010).

As late as the 1960s, many eggs were obtained directly from farms or home delivered by milk companies (Bell, 1995). Today, most eggs are sold in supermarkets. Once size (pee wee to jumbo), color (brown or white egg tables), and quality (AA, A, B, or ungraded) were the only egg choices consumers could make. Now, specialty eggs comprise ~ 5% of the market. Examples include organic, vegetarian fed, free range, cage free, or fertile. Some egg types boast higher contents of nutrients such as vitamin E or omega-3 polyunsaturated fatty acids while one type claims 25% less cholesterol than traditional eggs. Even generic eggs provide a number of essential fatty acids, vitamins, and minerals. Human milk is the only food source with a higher biological protein value for people (Anderson, 2003).

In 2009, 57.8% of eggs went to retail, 30.8% were further processed, 8.5% went to foodservice use, and 3.0% of eggs were exported. Top foreign markets for table eggs were Canada, Hong Kong, and the European Union, while Canada and Japan were the top importers of egg products. Egg quality allows the US to out-compete competitors such as China, even though they are able to produce eggs more cheaply.

1.2 Washing table eggs

In the United States, Canada, and Japan, shell eggs are washed and graded prior to being packaged for retail (Zeidler, 2002). Though washing eggs was once disallowed in the US, it is now required for plants that participate in the Agricultural Marketing Service (AMS) voluntary grading program (USDA, 2003). Washing eggs with water colder than the egg, heavily contaminated with bacteria, containing large amounts of soluble iron, or in machines whose surfaces are contaminated with large numbers of microorganisms are factors determined to increase chances of bacterial cross-contamination during egg washing (Moats, 1978; Zeidler, 2002). Such conditions are addressed by AMS guidelines (see www.ams.usda.gov) and when attention is given to these factors, modern commercial shell egg washing operations result in improved microbiological egg quality (Baker and Bruce, 1995).

1.2.1 Effects of washing

Initially, table eggs in the US were not washed but were sanded to remove stains. In the 1940s, at the height of per capita consumption, a non-automated system involving submersion of eggs into water was common. Water conditions were not monitored closely so some eggs were washed with dirty, colder water. After eggs were separated according to cleanliness and size, washed and clean eggs were stored until needed for retail (Stadelman, 1995; Bell, 2002; Zeidler, 2002). After the USDA published Market Research Report Number 757, submersion of eggs was no long advised. Since that time, research has been conducted to verify and further improve the efficacy of egg washing.

Kinner and Moats (1981) inoculated simulated wash water with bacteria previously isolated from shell eggs. Temperature, pH, and detergent affected the survivability of pure cultures. When wash water pH was > 10, Escherichia coli, Salmonella, Citrobacter, Enterobacter, Proteus, Klebsiella, Alcaligenes, Flavobacterium, and Pseudomonas; Escherichia coli Pseudomonas were almost instantly destroyed. Staphylococcus aureus was adversely affected by detergent though protected by 1% egg solids. Streptococcus faecalis was the most resistant of the organisms tested, surviving for over 2.5 h.

Catalano and Knabel (1994) analyzed the effects of pH and rapid chilling on S. Enteritidis destruction during simulated commercial egg processing. Eggs were immersed in inoculated fecal slurry before being washed at pH 9 or 11 in 37.7 °C wash water followed by rapid or slow chilling. Wash water pH significantly affected shell surface survival of Salmonella. Significant cross-contamination was observed between inoculated eggs and control eggs at wash-water pH 9 (75.0%) but was decreased at pH 11 (8.3%), based on shell surface counts. Slow chilling increased S. Enteritidis survivability regardless of wash-water pH. At pH 9, S. Enteritidis penetration into egg contents increased.

Leclair et al. (1994) describe a model for inactivation of Listeria monocytogenes and S. Typhimurium in simulated wash water. Temperature, egg solids, pH, and chlorine were the treatments used to generate the data used in the models. Higher temperature and lower egg solid negatively affected survivability of both organisms. S. Typhimurium survivability decreased significantly affected at higher wa...