Because of their low moisture content micro-organisms cannot develop on them, however once placed in a suitable environment the micro-organisms proliferate.
For example, with seeds as a salad topping, dry fruit or nuts in a yoghurt, spices or herbs as seasoning, bacteria find the ideal conditions to multiply and reach levels that can result in food poisoning.
Bacteria are present everywhere but most are harmless and some are even beneficial. Others however are pathogenic and cause serious illness when allowed to reach high contamination levels.
The contamination can take place in the field (contaminated irrigation water), at harvest (soiled equipment or trucks), in the factory during processing or even during storage (poor hygiene or sanitation).
Some bacteria cause visible signs of adulteration similar to mould but other bacteria may develop without any sign of spoilage.
Quality control and pasteurisation
Food laboratories look for contaminants by growing the micro-organisms present on food samples in a culture medium. Total bacterial count and mould and yeast levels indicate the overall sanitary condition of the food. Pathogenic bacteria such as E Coli and Enterobacteria are identified separately.
Processors and packing facilities verify the microbiological levels of the foods they handle through quality control. But sampling programs and laboratory analysis will at best identify some of the contaminated material, but not all, because of the random nature of sampling and the inhomogeneous distribution of the contaminants.
Standards for maximum and target levels of microbiological contamination are set by industry specifications.
Suppliers to the food industry have to meet the strictest standards to minimise the risk of contaminating the final product and to guarantee its microbiological safety up to the end of its shelf life.
Specifications in effect in most nut and seed processing facilities are indicated in Table 2 below. The data shown are based on quality controls of incoming ingredients many of which need to be decontaminated because maximum levels were exceeded.
These results were compiled form facilities equipped with NAPASOL pasteurisation installations. Contamination levels are reduced below target values following pasteurisation guaranteeing microbiologically safe products.
This technology is supplied by NAPASOL AG a Swiss company specialised in food safety technologies. Steam injected in a strong vacuum allows condensation on the surface of the product rapidly raising temperature and effectively killing the micro-organisms. A subsequent vacuum phase removes the moisture by condensation thus cooling and drying the product. Exposure to heat and moisture are thus minimised to the benefit of the quality of the product. The thermal treatment developed by NAPASOL is a rapid low temperature processes that is effective at decontamination without cooking the product.
Risks and consequences
Food poisoning might only trigger gastrointestinal disorders in healthy individuals but in the young, the elderly, and those with weakened immune system it can be life threatening.
Several product recalls have affected the spice industry because consumers were using spices and herbs to flavour foods that were not subsequently cooked or not cooked at temperatures sufficiently high to be lethal for the bacteria.
Because spices and herbs have notoriously high microbial loads irradiation and fumigation are approved processes for decontamination. However consumer resistance to irradiated products and environmental concerns related to fumigation favours treatment with more natural steam based thermal processes such as the technology developed by NAPASOL AG.
Currently a massive product recall is affecting the US peanut industry because of salmonella contamination. In this case the peanuts and peanut paste were sold as an ingredient to more than 100 companies and made their way in the recipes of over 1900 branded products. Products recalled include ice cream, biscuits, cakes, candy, snack bars, snack mixes, peanut butter and even pet food.
Many are well-known brands manufactured by reputable food companies and the financial consequences are colossal.
The peanuts have sickened scores of people and sent 600 to the hospital and may have killed as many as eight people.
The detection of salmonella in retail packs of seeds or seed mixes has prompted 12 product recalls in the UK between February and May 2008 alone. Different seeds of various origins were found to harbour Salmonella. Recent outbreaks of food born illness have been traced back to nuts and seeds and have prompted the Food Safety Authority to implement an ongoing intensive five month sampling programme which ran until March 2009 at retailers throughout the UK.
Ready-to-eat seeds and nuts are not usually cooked but rather eaten as is or used as a raw ingredient. All these high risk products should go through a thermal process to eliminate bacteria. This is particularly critical when they are used as an ingredient in many recipes as is the case in the extensive recall underway in foods containing the salmonella peanuts.
The California almond industry recently faced two product recalls in 2001 and 2004 because of salmonella contamination.
In 2007 the FDA mandated the pasteurisation of all almonds commercialised in the USA. The mandatory treatment of some 120 million kg of raw almonds requires large investments in pasteurisation lines.
Improving food safety
In a tightly regulated food safety environment, microbiological standards are increasingly demanding. New technologies are needed to manage the microbiological risk of all foods that may be naturally contaminated and consumed raw. Investment in food safety must be a top concern of managers in the food industry because of the enormous cost of product recalls.
In addition to the loss of the product itself, damage to the brand, loss of customer confidence and the cost of litigation can be tremendous. Therefore a substantial investment in pasteurisation equipment is more that justified. Food operators will certainly be looking for technical solutions such as the NAPASOL pasteurisation technology to insure that microbiological risks are properly managed.
Natural pasteurisation processes such as the NAPASOL technology successfully kills micro-organisms without altering the organoleptic and nutritional qualities of the products.
Dr Cameon Ivarsson is Director, NAPASOL AG, Reinach, Switzerland. www.napasol.com.
