In this paper, we will discuss an important case of processed foodstuffs contamination by E.coli O157:H7 that happened in the USA in 1996. This outbreak is of interest as it illustrated the importance of food pathogens, highlighted the necessary response of the concerned manufacturer and of the authorities as well as the necessity of improving the USA legislation with regards to food safety. After briefly presenting the Odwalla outbreak, we'll discuss the pathogenicity of E.coli O157:H7 as well as some of the available techniques for its detection and destruction. We will then go further on by bringing up the reforms that happened in the US legislation on food safety and illness surveillance within the year following the outbreak and finish by discussing this issue in relation with developing countries.
The Odwalla outbreak
Explanation and figures
In October 1996 several cases of illnesses caused by a particular strain of E. coli O157:H7 were detected in Washington, Colorado, California and British Columbia. The Centre for Disease Control declared the foodborne-disease outbreak (FBDO) as two or more persons were experiencing the similar illness resulting from the ingestion of a common food. Indeed, the conducted investigations had confirmed that the E. coli infections were related to the consumption of unpasteurized apple juice manufactured and sold by the Odwalla Company. At that time Odwalla, as well as other apple juice companies, were mainly focusing in good practices along the chain production in order to avoid pasteurization as they believed this process altered nutrient contents, appearance and taste (Deliganis, 1998). While screening of E. coli strains were conducted at state level, the Food and Drug Administration (FDA) urged the recall of the products, boosted the inspection of apple juice orchads and conducted its own microbiologic tests of apple juice samples to test the presence of E. coli. (McCarthy, The Lancet, 9 November 1996)
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Odwalla E. coli O157:H7 outbreak facts:
Total number of juice-related cases
Cases ensuing from drinking juice
Cases with illness contracted from a person who drank juice
Children below age 5 in total cases
Cases of HUS
Detected cases of E. coli O157:H7 poisoning in Washington
Cases proved from consumption of Odwalla products in Washington out of 13 cases reported
(Source: Death by Apple Juice: The Problem of Foodborne Illness, the Regulatory Response, and Further Suggestions for Reform (Deliganis, 1998).
Economical burden of E. coli O157:H7 outbreak
After the 1996 E. coli O157:H7 outbreak the Odwalla company followed serious economic losses: in February 28, 1997 the company posted a loss of $11.3 million for the fiscal year ending (Layne & Anni, 2007). Indeed, Odwalla's brand name was damaged and sells fell by 90% in the immediate wake of the crisis and its stock fell by 40% (Austin & Nancy K. 1998). The company laid off ten percent of its 650 workers by the end of 1996 and also faced lawsuits with $27 million worth of insurance and $10 million in cash (Groves & Martha, 1996). Two years after the incident, company's stock price was still low and it was still undergoing reductions in sales and profits (Deliganis, 1998).
In 1998, Odwalla pleaded guilty for several criminal charges and paid a $1.5 million fine from which $250.000 was donated to research on preventing food illness (Henkel, 1999). The firm spent around $12 - 15 millions (Bulluck, 1998) for families of victims' lawsuits as well as for future medical and educational expenditures of the affected children, having to face lifespan medical care. The majority of this money was given to the families whose children were the most ill and for the family of the dead 6 years old girl, Odwalla gave $250.000 (Bulluck, 1998).
Pathogenicity of Escherichia coli O157:H7
Escherichia coli is a facultative anaerobic bacteria, commonly found in intestine of mammals. Most of E. coli strains are harmless; nevertheless some, like E. coli O157:H7, are highly dangerous and induce food poisoning. E. coli optimal growth temperature is of 37Â° which allows it to live in intestine even if the bacteria can survive outside the body for a short period of time.
The strain involved in Odwalla case was of serotype O157:H7: this enterohemorrhagic E. coli (EHEC) can produce lethal toxins (Shiga Toxin E. coli: STEC) causing food poisoning.
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After ingestion of contaminated food, EHEC multiply in intestine, adhere to enterocytes, invade the mucous membrane and trigger off the immune system. Three days to one month after contamination simple diarrhoea can occur. But if EHEC destroy microvilli of enterocytes and produce STEC: these interact with organelles of host cells and destroy their endoplasmic reticulum, leading to enterocytes death (University of Edinburgh). Blood then conveys the STEC which react with vessel walls and red blood cells, reaction leading to haemolytic-uremic syndrome (HUS) (drastic loss of blood cells and kidney failure) and thrombocytopenia (loss of platelets) (PNAS). HUS occurs mainly in children (under 8), the elderly (higher 65) and the immunosuppressed. EHEC infection also leads to thrombotic thrombocytopenic purpura in the elderly. This multi symptomatic disease (neurologic symptoms, kidney failure and micro-angiopathic haemolysis was not detected in the Odwalla outbreak.
Following this outbreak, simple diarrhoea, massive and bloody diarrhoea, haemolytic-uremic syndrome and death occured.
Laboratory diagnosis of E. coli O157:H7 can consist of the molecular detection of DNA fingerprint by pulse field gel electrophoresis (PFGE). This method needs 48 hours only and involves separation of DNA fragments of unknown strain and their comparison with a standard strain (USDA, 1992). An other detection method of E. coli O157:H7 can be the ELISA (Enzyme Linked Immunosorbent Assay) test. A new method of immunomagnetic separation consists on an isolation of bacteria by recovery of antigen-antibody complexes fixed on a magnetic bead with a magnet. This method is faster, automatable and allows EHEC identification in small quantity.
An EHEC contamination is followed by antibiotic therapy and in worst cases by long term dialysis treatment.
Prevention of contamination
Usually, when E. coli is found in a sample, it has to be directly linked to a faecal cycle transmission. In order to prevent this incident, the company has to avoid cross contamination and vector contamination (flies can carry STEC), clean the raw foodstuffs and adopt good hygiene practices (clean hands, gloves) with possible heat treatment of endproduct, etc.
Flash Pasteurization of apple juice
The Flash Pasteurization is used to improve the shelf life of fruit juice in particular apple juice. The characteristics of this process are:
Low treatment time
Flowing of the product
However we should not forget the hygienic conception of the equipments, the pre-sterilization on the installation and the CIP (Cleaning In Place).
So, the flash pasteurization process has several advantages:
High quality of the product
Heat transfer faster and uniform
Cheaper packaging than cans
There are also some disadvantages:
Important investment at the beginning
Important cost of the staff formation
Equipment and control more complex
In the flash pasteurization process, the product is heated to a temperature of 90 to 95Â°C during 2 to 10 seconds and is then rapidly cooled (see T,t chart).
The canning process uses higher temperature (110 to 120Â°C) and more time (couple of minutes).
The pasteurization scheme depends on the kind of bacteria that are present in the juice and the initial and final microbial charges of the product. The reference bacteria are the Streptococcus. Most of the time a 5log or 6log reduction is done.
Indirect heating for the flash pasteurization of fruits
The fruit juices flash pasteurization can be done with a plate or a tubular exchanger therefore using indirect heating and impeding the mix of product and heating (steam or hot water) or freezing (cold water) compound.
The choice of the pasteurizer depends on the juice type:
Light juice, without pulp needs plate exchanger,
Lightly or very charged pulped juice needs tubular one.
In order to determine the type of the pasteurizer, the concentration of the juice in Brix degree should be known. It corresponds to the sucrose fraction in a liquid or, i.e., the percentage of dried soluble matter. The more important the Brix degree, the more concentrated is the juice. The CO2 rate, the percentage and the kind of fibbers are also important parameters.
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In addition, in order to remove all the bad smells (volatile substances), the bleeding of the circuit is necessary and this process corresponds to a temperature fall of 10Â°C.
The plate exchanger is composed of several plates disposed such as millefeuille. These plates are just separated by few millimetres. In these spaces, fluids flow. The plates are limited by seals in order to avoid water or product leaks. Plates are made of corrugated surface (Chevron plates) in order to create turbulent flows that improve heat transfers.
The fluid moves from the top left-hand corner to the bottom right-hand corner of the plate. A pipe allows the product to jump a Chevron plate (which is heated by steam or hot water) and to flow on the next plate. With this kind of equipment, adding plates increase the exchange surface.
Fluids flowing Chevron plate
The fluids flowing are represented by the figure bellow. The product is heated several times by steam and it is finally cooled down by cold water.
This installation is composed of a beam of tubes in a calender. Generally the product flows in the tubes and the heating fluid flows in the radiator grille. The bends improve the turbulence and heat transfer.
Different kinds of tubing exist:
Legislation regarding foodborne diseases in the US
Nowadays, USA is said to have the safest food supply in the world and the tougher nationwide surveillance of illnesses: this approach towards public health and response to crisis is done through advanced equipment and communication technologies. (Food and Nutrition Board, 2010)
The Odwalla outbreak initiated a hardening of USA's legislation on fruit juice safety and foodborne diseases surveillance. (Deliganis, 1998)
National regulation of safety of fruit
Structure of the institutions
The main federal institutions implicated in the food safety and care are: the Food and Drug Administration (FDA) and United States Department of Agriculture (USDA), the Centre for Disease Control and Prevention (CDC) which is a branch of the Department of Health and Human Services (HHS), the Agricultural Research Service (ARS), the Cooperative State Research Education and Extension Service (CSREES) and the Environmental Protection Agency (EPA).
In addition to the definition of key terms and their tighter labeling regulation, these agencies regulate food safety through:
Federal Food Drug and Cosmetic Act (1938) - legal framework for government regulation.
Good Manufacturing Practices (GMP) - guidelines for appropriate sanitation practices along the chain production of any food.
Compliance Policy Guides (CPGs) in which Zero Tolerance is demanded towards the positive detection of pathogenic microorganisms in any foods: this leads to seizure and condemnation.
The Hazard Analysis and Critical Control Points (HACCP) - analysis of dangers presented by the materials used in the manufacturing process through 7 basic principles.
Both the Food Code promulgated by FDA and the Sanitary Transportation and GMPs address transportation issues.
At the time of Odwalla outbreak, only two states had promulgated specific guidelines on apple juice production: California and Florida (Deliganis, 1998).
Private sector and food safety
The industry has to ensure safety of its own products: this is an issue as it is not always clear to which extent are the responsibilities of government and those of industry.
Food safety reforms on apple juice following Odwalla case
The Odwalla case gave the consumers the opportunity to demand the building up of one single agency on food safety instead of 9 federal and multiple state entities (De Waal, 1997). The FDA held a National Advisory Committee on Microbiological Criteria for Foods on December 16th 1996, few weeks after the crisis, to review the situation of food safety presented by the outbreak. After the meeting, FDA adopted a new approach for juice safety comprising (KVENBERG, 1999)
Obligatory updated HACCP procedures.
Obligation for companies to inform consumer about risk of drinking apple juice but voluntary labeling of products that have not gone through pasteurization.
Inspection on hazard analysis.
No mandatory use of a specific intervention technology, such as thermal processing.
Recommended adequate level of a cumulative 5-log reduction in the target pathogen.
Educational programs: for industry and for consumers.
Foodborne illness surveillance in the US
With the CDC as central organism for data collecting and information communication, the US can rapidly act when facing a foodborne outbreak in spite of the inherent delays for case reporting. The E. coli contamination of apple juice was rapidly discovered thanks, first, to the strong active electronic surveillance involving the collection of data given by state laboratories performing routine analysis of stools. Five laboratories using the PFGE technique were part of the Pulse Network (PulseNet) and comprised by the Foodborne Diseases Active Surveillance System (FoodNet), therefore allowing the large scale report of foodborne pathogen detections. Thanks to this active surveillance the health departments of the country were aware about the E. coli 157:H7 outbreak and could take several measures to enforce detection techniques in any laboratory, as a state of emergency. The importance of the technique is such that it has now become of general use throughout the country. (CIFOR, 2009)
1999 administration reforms on food safety and foodborne disease surveillance
As a direct response to the Odwalla E. coli outbreak, Bill Clinton introduced his Food Safety Initiative in 1997 and came up with a plan about how to improve nationwide early warning system about food safety measures, asking for improvements in research and technology and better partnerships between government and private sector. This plan had 6 main key targets: (Deliganis 1998)
Risk posed by foodborne pathogens assessment, defining the frequency of biological agent and the magnitude of adverse health effects for human and aiming the construction of new HACCP,
Increased inspection and compliance of companies to new HACCP,
Increase research and its coordination at a federal level,
National Early Warning System for foodborne illness outbreaks, adding two new surveillance sites to the pre-existing five,
National education campaign,
Better coordination between government actors (federal - state - local) through the Foodborne Outbreak Response Coordinating Group (FORCG).
As we discussed in the Odwalla outbreak foodborne illnesses are of health importance and need to be addressed. When it comes to the food safety situation of developing countries it may be of necessity to improve public health inspection ensuring the chain production hygiene practices. Also, when considering a small company in the tropics, it is obvious that pasteurization should be implemented, and as the optimum temperature-time couple of pasteurization has to be experimentally determined, this can lead to an increase of cost. For cost reasons, developing countries face difficulties when it comes to pathogen detection: the best cost-efficient methods should be implemented and this should go along with the education of professionals. We saw that the USA have a very efficient electronic surveillance and that outbreak are clearly and rapidly spotted: this may involve higher cost but it leads also real-time response by the government and prevent too much economic losses.