Preservation in Oil and Botulinum - Risks and Dangers

Welcome to the kitchen of My-personaltrainerTv. Today we will deal with a rather thorny topic, often unfortunately underestimated: the preservation of food in oil. Considering the delicacy of the topic, I have decided to give you some very important basic theoretical notions, to understand together what are the possible risks and dangers associated with consumption. of inadequately prepared preserves in oil.

Among the most felt dangers stands the "intoxication from C. botulinum, an anaerobic bacterium with high temperature resistant spores, capable of producing a life-threatening neurotoxin. Let us briefly remember that spores are particular forms of resistance put in place by bacteria to survive even in conditions unfavorable to them. But let's proceed step by step.

Limit contamination of volatile bacteria

Isolates the food from the surrounding environment

No because...

• It has no effect on anaerobic bacteria (e.g. Botox)

The solution is to subject the food to be preserved in oil to particular treatments, capable of guaranteeing its microbiological healthiness (eg acidification, salting, pasteurization).

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, high pH) the spores germinate in vegetative cells, then in live and active bacteria responsible for the release of the toxin.
To understand the danger of botulinum toxins, just think that a single gram is capable of killing 10 million people!

Please Note
To make food preserves safe, it is therefore important to BLOCK or PREVENT SPORE GERMINATION.

, it is important to create an unfavorable environment for spore germination; this result is obtained through specific treatments, such as:

• Acidification (pH <4.5): method that involves boiling or blanching the food in an acid solution (consisting of water and vinegar or vinegar alone). Blanching guarantees an "optimal consistency of the food", while acidification ( or the reduction of pH below 4.5) is an indispensable practice in conservation in oil, to prevent the germination of botulinum spores.
• Brine / salting: preservation of the food in saline concentrations of 10-33%. This treatment is ideal for the preservation of certain foods, such as olives, capers and anchovies.
• Addition of sugar (50-60%): indispensable treatment in the preparation of jams and marmalades.
• Sterilization treatment at 121 ° C for at least 3 minutes. This method, which is almost impossible to carry out at home, is carried out on an industrial level by using autoclaves. Such temperatures destroy all heat-resistant spores, possibly present in the preserves.
  Whereas the spores of the C. botulinum type A can withstand temperatures of 100 ° C even for 5 hours, it is understood how the classic home heat treatment of jars in water cannot, by itself, guarantee 100% microbiological safety. When preparing a preserves in oil at home it is therefore necessary to resort to some additional treatments, such as preventive acification (see below).
• Freezing
• Drying

, peppers, beans, onions, etc.)

Animal preserves (tuna and canned meat)

Sausages and smoked meats

Non-acid sauces rich in oil (e.g. pesto alla genovese, rocket pesto)

Foods rich in salt or sugar, and canned foods with an acidic pH (<4.5):

• Dried foods (e.g. dried tomatoes)
• Fruit preserves rich in sugar (jams and marmalades)
• Animal preserves rich in salt (e.g. salted anchovies)
• Vegetable preserves in brine (e.g. olives)
• Vegetable preserves with acid pH (tomato sauce)

or to other specific disinfectants; washing must be followed by rinsing the food in running water.

Appropriate PREPARATION OF TOOLS and containers before food preparation. In this regard, washing in the dishwasher or prolonged boiling for 20 minutes of jars (with their respective screw caps) and utensils is recommended.

ACIDIFICATION OF THE FOOD to be preserved in oil. The "food must" be subjected to acidification until a pH <4.5 is reached by adding acidifiers (citric acid) or blanching in vinegar or in a 50:50 solution of water and vinegar. The ideal vinegar for this treatment it is certainly that of wine, with acidity equal to or greater than 6%. If you want to use a more delicate vinegar (eg apple cider vinegar, with an acidity of 5%) it is advisable not to dilute it in water, but to use it pure.

TREATMENT OF SPICES / AROMATIC HERBS. Particular attention must be paid to the use of aromatic plants inserted raw in preserves in oil: even the spices must in fact be adequately treated to reduce the risk of microbial contamination. For this purpose, we recommend the use of dried aromas; those who wish to use fresh aromatic plants, on the other hand, must proceed with the scalding in water and vinegar, and with the subsequent drying in a clean cloth.

CORRECT DRYING OF THE FOOD TO BE STORED. After the preliminary treatment in the solution of water and vinegar, the food must be wrung out or otherwise dried from excess water. For example, when preserving aubergines in oil, they must first be boiled in water and vinegar, then squeeze and leave to dry in a clean cloth for a few hours, or overnight, in order to remove as much water as possible. Let us briefly remember that the presence of water in the food can facilitate the development of molds, other microorganisms that are potentially dangerous for the organism or even favor the germination of botulinum spores.

FILLING THE AIR SPACES that form in the preserving container. During potting, it is not uncommon to observe the presence of small air bubbles trapped in the oil. To fill all the empty spaces, it is good practice to press the food with a spatula or a specific press (both tools must be subjected to a preliminary heat treatment in boiling water or in the dishwasher); you will then have to wait a few hours before closing the jar with the cap to help the air escape.

TOPPING UP. Make sure that the food to be stored is completely covered with oil. After having filled and waited for any air bubbles to come out of the jar, it is likely that the oil level has dropped, thus leaving some parts of the food uncovered. It may therefore be necessary to top up, or add of other oil

PASTEURIZATION of the preserves in oil at 80 ° C for at least 10 minutes; this further heat treatment guarantees the elimination of any botulinum toxins (much less resistant to heat than the spores). In oil preserves, in which acidity and water scarcity conditions reduce the resistance of the spores to heat, a pasteurization treatment at relatively low temperatures (80 ° C) for a few minutes is sufficient.
As an alternative to pasteurization, on an industrial level, the product can be subjected to a sterilization treatment at higher temperatures (121 ° C for at least 3 minutes). Reaching such temperatures it is possible to sterilize the food (destruction not only of toxins, but also of spores), therefore the preventive acidification treatment described in point three becomes superfluous. Nevertheless, sometimes even the industry prefers to opt for a "preventive acidification, so as to be able to perform a milder heat treatment (pasteurization at 80/90 ° C for 10/20 minutes), to the full advantage of the consistency and nutritional properties of the product.

STORAGE IN A DARK and DRY PLACE. The oil tends to deteriorate in contact with light: for this reason, it is advisable to store the jars in the dark or to wrap them with aluminum or dark paper.

rancid of the preserve

Alteration of the appearance of the stored food

Even just one of the aspects listed above should set off an alarm bell.
However, it is appropriate to reiterate that the danger of botulinum also lies in its relative "invisibility": it is not uncommon, in fact, that the contaminated food does not show any sign of significant alteration or deterioration. In case of doubt, even at the mere suspicion of alteration , it is recommended not to open nor to taste the preserves in oil.