When we talk about cross contamination we only think about those precautionary and hygiene measures that we must maintain in the kitchen. However, we overlook that there may also be cross contamination when shopping. And it is not only about containing possible pathogenic microorganisms. Allergens, such as gluten present in some cereals and derivatives, such as bread, can put the health of our guests, even other customers, at risk if we do not know how to prevent cross contamination.
What is cross contamination?
Claudia Garcia, food technologist and Quality Manager at ALDI Central de Compras (Spain), explains that “cross-contamination between foods is the transfer of contaminating substances from a source to a food. This transfer can be of pathogenic microorganisms (bacteria, for example) or other substances such as, for example, allergens.”
Although this transfer is the result of an unintentional discovery, the expert warns that «it can have harmful effects for the person who consumes the food.» Eating food contaminated by a pathogen can trigger food poisoning. In the case of allergens, they can cause anything from gastrointestinal discomfort to, in the most serious cases, anaphylactic shock.
When does cross contamination occur?
Cross contamination occurs when two foods come into direct contact with the contaminating agent. But it can also be produced through other objects. That is why a distinction is made between direct and indirect cross-contamination.
Types of cross contamination
Direct cross contamination
Dangerous microorganisms or allergens will be transferred from one food to another. A common risk situation in the kitchen, if food is not handled carefully, is bringing a raw product with pathogens close to another already cooked or raw product ready to eat.
In the case of allergens, it can happen, for example, if at home we put a mix of nuts in a jar that contains hazelnuts, walnuts, cashews and peanuts. Once finished, we put, for example, only nuts without washing the container, or without checking if there are remains of other nuts. If one day a guest with an allergy to peanuts or cashews comes to our house and we offer them these nuts as a snack, they could suffer an allergic reaction.
Another possible situation in the domestic sphere is to put a buckwheat bread (gluten-free) and another white or whole wheat bread (with gluten) in the same shopping bag.
Indirect cross contamination
The transfer occurs when using instruments to cut, remove or manipulate food in any way, as well as when placing it on already contaminated surfaces. “It can also happen through the handler’s hands if they are not washed when changing food. And, of course, by not maintaining good hygiene and separation with kitchen material, such as utensils, cloths…,” he points out.
An example of frequent and very dangerous contamination is cutting raw chicken meat and clean lettuce with the same knife. Or use it to cut a cooked food ready for consumption. Or handle gluten-containing panels and gluten-free panels on the same surface. And pay close attention to the unhygienic habit of serving jam with the same spoon used to stir coffee with milk. If we offer that jam to someone with a milk allergy, they could suffer an allergic reaction.
How to avoid cross contamination at home
Cross contamination can be avoided by following some basic hygiene and order practices in the kitchen:
- Store highly perishable fresh foods, such as meat, fish, or seafood, in the refrigerator and in containers that separate them from other foods. In particular, we must avoid any type of dripping of raw food juices into the refrigerator.
- Always separate cooked foods from raw foods
- Using airtight containers minimizes risks
- Maximize hygiene of hands, utensils and work surfaces (apron, countertop, cloths, knives…).
- Do not work with the same utensils if we handle foods with allergens and among our guests there are people with allergies, celiac disease or food intolerances.
- Use different boards to cut bread and other foods. Avoid wooden ones whenever possible, since they are porous and cannot be 100% disinfected.
- Always wash our hands before handling food.
How to avoid cross contamination when purchasing
- Do not use fruit gloves for bakery
Gloves are a hygienic practice in the bakery section to avoid contaminating the product that another consumer is going to pick up. They are also used in the fruit and vegetable section. “Gloves used in the fruit section, for example, should not be used to pick up the ready-to-eat bakery product because we could transfer contaminants or allergenic substances from one to another,” warns the expert.
Something as seemingly harmless as picking some peaches or kiwis, two especially allergenic fruits Even if they are not on the official list of allergens, and you take advantage of that same glove to choose the rolls for breakfast, you can cause an allergy problem for another customer if they are highly sensitive to those allergens. Without forgetting that the surface of the fruit is not completely clean and may contain germs that are transferred to the pan.
The risk, in principle, is lower if we use the bakery glove to select, for example, apples or strawberries. “This is because fruit and vegetables must be washed before consumption. “It could be a problem if consumed without proper cleaning.”
- Different bags for foods with allergens
Our shopping bag can be the unintentional scene of dangerous substance transfers. In this case, the risk is not so much from buying raw food in poor condition, which is not common in Spain given the high food safety measures, but from the passage of allergens without us realizing it when buying certain products in bulk. Without going any further, bread or nuts.
«Bread and pastry items are not sold in airtight packaging and are those that would present the greatest risk. It is true that by their very nature they do not present ideal conditions for the development of germs, but they can be a problem of cross-contamination by gluten,» point.
If you have guests at home with celiac disease, you must separate your bread from other panels, even in the shopping bag.
- Clean the shopping bag periodically
Check if liquids or juices have been spilled, if there are bread crumbs, vegetable remains… These residues can serve as food for microorganisms that could contaminate our next purchase.
- When in doubt, packaged or with a tightly closed bag
In the supermarket most products are packaged. “This way there is no risk of cross contamination. In the case of buying at an assisted sales establishment, we must make sure that the bags of meat, chicken or fish are closed tightly,” says García. The danger here would be «not with those in which cooking or washing is planned, but with those that are ready to eat and do not have a watertight container, such as bread.»
The ALDI Council
Did you know that chefs have a table for each food group and that they differentiate them by a very strict color code? Without going to those extremes, you should have at least two at home. One for meat and fish, and another for fruits and vegetables. Finally: always wash them well between uses to reduce the risk of poisoning.
claudia garcia. Agricultural technical engineer and food technologist. He is responsible for Quality at ALDI Central Purchasing (Spain). Previously he has worked as a logistics process technician and as corporate manager of Fresh Product Quality at Caprabo – Eroski. She has been responsible for Quality at Comertel and a consultant at the Catalan Institute of Technology (Unitat d’Assessorament).
