Beware of health risks with home-made herbal oils

Herbal oils and vegetables pickled in oil pose health risks
Home-made herbal oils and vegetables soaked in oil, such as peppers, chilli, or aubergines, are in vogue in many private households. However, there is a risk of an increase in pathogenic germs, which is why the Federal Institute for Risk Assessment (BfR) discourages "self-produced products such as vegetables in oil or herbs in oil in private household to produce and store."

The Federal Institute for Risk Assessment has considered whether self-produced herbal oil and vegetables stored in oil could pose a risk of food poisoning from toxins of Clostridium botulinum if these foods are produced in reserve and kept for a period of time in the household. The analysis of the available data showed "that the manufacturing processes in the private household can not ensure that the propagation of Clostridium (C.) botulinum and the formation of botulinum toxin is generally prevented in the products," according to the BfR communication. From the storage of self-made products such as chilli or garlic oil, vegetables in oil or herbs in oil in the private household should therefore be discouraged.

In self-produced herbal oils dangerous bacteria can multiply during storage. (Image: fotoknips / fotolia.com)

Formation of dangerous neurotoxins
If the herbal oils and the pickled vegetables are heated sufficiently before consumption, it is generally to be assumed that there is complete killing of possibly existing germs. But home-made foods are often meant for direct consumption, and the bacteria they contain can be a problem. "In particular, in the event that the products are not sufficiently heated before consumption or used for cooking and frying, but for the preparation of salads and other raw foods are intended," according to the BfR a health risk. For in self-produced foods, bacteria of the genus C. botulinum can multiply on prolonged storage, which at worst cause a life-threatening disease of botulism. According to the BfR, the bacterium only reproduces in the absence of oxygen and is able to form so-called spores, which are highly resistant and can survive unfavorable environmental influences. These spores are to be found on almost all foods of animal and especially vegetable origin.

Threatening disease of botulism
In conditions without the presence of oxygen and with sufficient nutrients - such as those found in herbal oils - the bacteria can produce neurotoxins, which cause botulism in humans, BfR warns. According to the Institute, these neurotoxins are absorbed by eating contaminated food. A disease of botulism then shows up initially with nonspecific symptoms such as gastrointestinal disturbances, nausea and vomiting. In the further course occur "the typical symptoms such as double vision, pupillary rigidity, speech disorders and later respiratory paralysis and asphyxiation in full consciousness," reports the BfR. A total of 36 cases of human botulism were reported in Germany between 2008 and 2013, including at least one death.

Complete killing of germs difficult to ensure
In the production of vegetables or herbs in oil, there are, according to BfR a variety of different production options and recommended tips on how to proceed, in principle, the vegetable food directly or after different pretreatment (eg washing, cutting, drying, heating) in a corresponding Vessel to be filled with the desired oils. Since there is no more oxygen due to the addition of oil in the finished product, there are good conditions for the proliferation of C. botulinum and the formation of the neurotoxins. In order to avoid this, the usual kitchen hygiene rules must be observed during the preparation, but a complete removal or killing of the bacteria in the household is difficult to achieve, the BfR warned. Although the washing of the vegetables already leads to a reduction of the germ load and the heating can also cause a reduction of the load. A safe kill of C. botulinum and especially the spores was, however, guaranteed "only when heated to at least 121 ° C" and "this temperature can not be reached by boiling in the household," explains the BfR. If the heating temperature is too low, there is even a risk "that any bacteria that may be present will only be stimulated to form resistant spores that can later germinate again."

Store herb oils refrigerated
Accordingly, in the production of vegetables and herbs in oil with the presence of C. botulinum and the formation of neurotoxins is to be expected. If the finished product is intended for storage, the proliferation of bacteria must be prevented so that no toxin production threatens. The factors such as available nutrients, available water and temperature must be taken into account, explains the BfR. Also, the acidity plays a crucial role. "The proliferation of C. botulinum continues to be inhibited with decreasing temperature and shortened storage time, decreasing water content and increasing acidity, until finally no more propagation takes place," explains the institute. For this reason, manufacturers need to know exactly how much acid the product contains and how much water is still available to the microorganisms to set the shelf-life for a given storage temperature. Cooling to below eight degrees Celsius and often even below three degrees Celsius is usually a mandatory requirement here. But many consumers are unaware that herbal oils are actually in the fridge.

Propagation of the bacteria can not be safely ruled out
Even with industrially manufactured products, the risk of an increase in C. botulinium can not be completely ruled out, as reports to the rapid alert system of the European Union show, according to the BfR. Thus, a product recall due to the detection of C. botulinum in "garlic in oil" from Germany (2003) and a disease outbreak by "zucchini and tomatoes in oil" from Germany (2015) are documented. Only under strictly controlled conditions can a safe product be produced. In hobby production in the private household, however, the individual parameters such as water content and acid can not be adequately captured. Thus, it is not ensured that an increase and toxin production of Clostridium botulinum is prevented in the products. Therefore, the BfR strongly advises against storage of self-produced products. (Fp)