This kind of complexity is a big problem for the investigation of food poisoning outbreaks. Where do you start looking for the source of a foodborne pathogen and how do you trace it back to its origin? Witness last year's E. coli O104 outbreak in Germany. Initially the investigating authorities were confident that the source was most likely Spanish cucumbers and/or tomatoes. But further detective work later pinned the blame on fenugreek seeds from Egypt. Unfortunately, delays in identifying an outbreak's source can lead to additional cases of illness - sometimes even deaths - that might otherwise have been prevented.

The problem of complex supply chains is well known, but a newly published research study led by the Institute of Food Research in the UK has managed to quantify that complexity and map the networks that supply our food. The researchers used some sophisticated methodology to analyse food trade data from the UN. The maths are a bit beyond me, but the findings are clear. Supply networks are incredibly convoluted and complex, but there are a relatively small number of countries that act as processing and distribution hubs in international food trade - the Netherlands fills this role in Europe. The study's authors concluded that the global food supply network is great for speedy distribution of food, but not much use for finding out where it originated.

I think this supports the view that the food industry needs to pay much more attention to the traceability of its' products and ingredients. Simply meeting the 'one step forward, one step back' requirement of the law is no longer enough. Tougher legislation may be needed, along with industry cooperation to identify best practice. Without action, the problem can only get worse.

The issue was highlighted this week by the "Stericycle ExpertRECALL Index" of all the food recalls logged by the FDA in America for the first quarter of 2012. According to the Index, there were 142 recalls during the three month period, which sounds a lot, although it was apparently 19% fewer than in the previous quarter. Those recalls involved around seven million individual food units, which also sounds a lot, but is actually 90% less than in the previous quarter. The real interest for me lies not in the number of recalls, but in the reasons for them. By far the commonest cause was undeclared allergens, which accounted for 40%, followed by Listeria contamination (30%).

The high number of Listeria-related recalls can be viewed as peculiar to the USA, arising from the 'zero tolerance' policy towards Listeria. Only this week a large nationwide recall of potentially contaminated bagged salads was announced. In the EU that recall may not have been necessary, since food safety rules say that low numbers of Listeria are acceptable, provided they do not rise to dangerous levels during shelf life. Whether the American approach is better is difficult to say, but it makes life a lot more difficult for food manufacturers.

Recalls prompted by undeclared allergens are a different matter. The picture in Europe is much the same as that in the USA, with allergens accounting for a large proportion of food recalls. Are all those recalls necessary? Again, it's hard to say, but what it illustrates is that a lot of food manufacturers really haven't got their act together when it comes to allergen control. Many allergen related recalls are caused by packaging and labelling errors. That should be easily fixable because it just means always matching the product with the correct packaging. Cross contamination incidents are much less common, and adopting sound allergen control plans could prevent many of those. Food manufacturers have it within their capability to do far more to prevent allergen related recalls, which would not only benefit consumers, but would also make sound business sense.

The CAST report, titled 'The Direct Relationship Between Animal Health and Food Safety Outcomes', looks at how the health of food animals produced under different conditions can have effects on food safety at distant steps in the supply chain. For example, a subclinical infection with Salmonella might not be apparent prior to slaughter, but may have a considerable effect on contamination rates at the processing stage. The authors make some thought provoking observations and point out that 'humane' animal production systems, like organic and free-range, can actually lead to higher rates of infection with pathogens than intensive indoor systems.

Reading between the lines, the report seems to be saying that we will need to take a pragmatic approach to meat production if we are to meet the demands of our growing population. We might think that intensive production systems are bad for animal health, but some of the science says otherwise, and this has consequences for food safety. Whether you agree with that or not, it is a point worthy of discussion. So far so good, but the report also contains the following statement on the subject of antibiotics in agriculture, "The use of antibiotics in food-animal production, however, raises some concerns about antibiotic resistance in bacteria that could affect the efficacy of antibiotics in the treatment of human infections. Concern about antibiotic resistance is not equivalent to actual risk. Resistant bacteria were present long before antibiotics were discovered and found in many places without livestock exposure."

This is at odds with much of the scientific literature the authors must have consulted before reaching their conclusions. It is certainly true that antibiotic resistant bacteria have been around for a long time, but isn't that because many antibiotics are derived from compounds produced naturally by microbes in the environment? They can be seen as weapons in an arms race that has been going on for millions of years. Microorganisms compete for resources, and antibiotics provide an advantage if they kill off competitors. Equally, evolving antibiotic resistance as a defence confers a similar advantage. Introducing vast amounts of antibiotics into the environment through livestock means a shift in the balance of power, which is seldom a good thing in ecological terms. It may be true that "Concern about antibiotic resistance is not equivalent to actual risk", but the CAST report does nothing to allay that concern.

It is easy to assume that all you need to stage the Olympics is a few shiny new sporting facilities and somewhere for the athletes to sleep, but the amount of infrastructure and organisation involved behind the scenes is vast. Take food safety as an example. The Games organisers are expecting 24,000 competitors and about nine million visitors to attend. That is a lot of extra catering in a short time. The consequences of a food poisoning outbreak could be disastrous, especially for any competitors affected. Nobody who has trained for years just to get to London deserves to have their medal bid ruined by a dodgy sandwich. So that is why the Food Standards Agency is putting so much effort into ensuring that all the food prepared, sold and eaten at the games is safe. They have announced a ten-member 'Food Safety Squad' of senior officials to oversee the preparations, extra training for enforcement officers, additional hygiene inspections and help for food businesses and funding for testing equipment to monitor food hygiene at Olympic venues. And don't even think about setting up an unlicensed hot dog stand or burger van anywhere in the vicinity. You may well end up in the Tower for the duration.

It's reassuring that so much attention is being paid to food safety for the few weeks of the Games, but what about the rest of the year? The Food Standards Agency is spending a reported £1.5 million on additional food safety inspections alone, yet the budget for routine inspections is being cut. More food testing will be carried out in the run up to the event, but in a few years there may not be enough laboratory capacity to cover even a basic surveillance programme. The Olympic Games is a prestige event for the UK and for London and visitors need to be sure that the food they eat is safe, but surely that applies just as much to ordinary Londoners after the Games are over.