Les œufs noirs très spéciaux de Hakone​

Vivre 7 ans plus longtemps grâce à un œuf ? Cela semble très improbable. Pourtant de nombreux Japonais et touristes croient en cette légende urbaine et n’hésitent pas à manger les œufs noirs d’Owakudani.


Hakone se trouve à seulement 3 heures de Tokyo, dans la province de Kanagawa. C’est ici que vous pourrez découvrir le phénomène particulier de Kuro-Tamago, également appelé les œufs noirs d’Owakudani. Owakudani signifie littéralement ‘la grande vallée en ébullition’ et doit son nom au paysage volcanique où règne en permanence une désagréable odeur de soufre.

Le dernier jour (Okuri-bon), un feu appelé okuri-bi est allumé pour renvoyer les esprits.

L’étrange couleur noire

Bien que leur apparence n’en donne pas l’impression, les Kuro-Tamago sont bel et bien des œufs de poules. La coquille est noire en raison de la façon dont les œufs sont cuits. Les œufs sont placés dans des cages en fer et sont cuits dans de l’eau volcanique à 80°C. Ensuite, les œufs sont cuits à la vapeur à 100°C et prennent leur couleur noire spéciale. Pas de panique, à l’intérieur, on retrouve les œufs normaux à la couleur blanche et jaune que nous connaissons, ainsi que le goût normal des œufs de poules.


Toute l’aventure réside dans le voyage à parcourir pour atteindre ces œufs. Vous pouvez accéder à l’endroit par un pont suspendu situé entre la magnifique nature et la vallée volcanique caractéristique d’Owakudani. Après avoir pu longuement admirer le paysage et respirer à pleins poumons cette nature resplendissante (quoiqu’une légère nuance de soufre est omniprésente), vous arrivez dans un petit magasin touristique où vous pouvez acheter les œufs et les manger sur place, tout en profitant d’une vue magnifique sur le Mont Fuji.  

Ceci représente au final bien peu d’efforts en sachant que chaque œuf devrait vous permettre de vivre environ 7 ans de plus. Vous pouvez acheter les œufs à la pièce ou par boîte de 5, mais il n’est pas recommandé d’en consommer plus de deux. Prendriez-vous le risque ?   

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Are fermented foods more nutritious?

Yes, fermentation can improve the nutritional content of foods in many ways. Here we explain you how citing tempeh as an example:

Essential Building Blocks

1. Bacteria involved in fermentation produce essential building blocks (vitamins, antioxidants and minerals) that help keeping a healthy body. For instance, dietary sources of vitamin B12 are usually from animal derived foods with very few plants providing a good amount. Lupin beans per se have very little content of vitamin B12 but when fermented by Rhizopus oligosporus and Propionibacterium freudenreichii into tempeh, the content of this vitamin considerably increases making it ideal for vegetarians. 

Neutralizing Anti-Nutrients

2. The process of fermentation “neutralizes” anti-nutrients or digestion blockers. For example, phytic acid is found in many plant products and is known to reduce the digestibility of protein and the release of minerals such as magnesium, iron, calcium and zinc. In short, this acid turns plant food less nutritious. Thanks to the fermentation of soybeans, research demonstrates that Rhizopus oligosporus NRRL 2710 can decrease, in about one third, antinutritional phytic acid in tempeh. The study also show that this microbe can also improve tempeh’s nutritional value by increasing the content of available phosphate.

Diverse Community

3. Fermented foods provide bacteria that contribute to having a diverse community in our gut. A study in healthy volunteers consuming tempeh showed that the participants had an increased population of, amongst others, Akkermansia muciniphila, a bacterium that is naturally present in the intestine and has been actively researched for its benefit in metabolic syndrome.

Can fermented foods cause gas or bloating?

Yes, this could be possible. If what you eat contains live microbes, gas or bloating are part of the most reported side effects, although these are quite harmless. 

Enjoy Small Amounts

Experiencing this kind of discomfort also depends on the amount of fermented foods you are starting with. Enjoy small amounts and allow your gut to go through an adjustment period


Some people do not have problems, others do. When trying to find the source of bloating, it is also important to bear in mind that consuming other, non-fermented foods can also be undigestible to your body, like lactose, and  can also be a common source of bloating.  Your dietician may help you for sure with your detective work to find the cause and the solution.

Can all bacteria in fermented foods survive in the gut?

Not really again. Let’s take fermented milk as an example. Lactic acid-producing bacteria grow on the sugars and other nutrients in milk. As they multiply, the bacteria produce compounds that change the flavour, texture, and yield nutrients in a wide range of products including e.g. cheese or yogurt. 


Many yogurts, but not all, contain bacteria that when consumed can reach the gut alive. When this happens, these bacteria can have an impact on our health as validated by the European Food Safety Agency (EFSA). 

In a scientific opinion, EFSA’s panel on Dietetic Products, Nutrition and Allergies agreed that yogurt containing at least 108 living cells/g  starter cultures of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus improve the digestion of lactose in people with lactose maldigestion

Do all fermented foods contain live microbes?

Not really. To produce fermented foods, ingredients must undergo a transformation process mediated by microbes, either naturally or through the addition of a starter culture. However, some products may afterwards be treated (pasteurized, baked, or filtered) in a way that ultimately kills/removes any live microbes before we consume them.

Heat Treatment

For example, sourdough.  When the dough is used to make bread it will be baked and this exposure to heat will kill the microbes. As well, some fermented vegetables are packaged in jars and may be heat treated as a means of extending its shelf life, or simply to stop the fermentation. Finally, when you prepare e.g. sauerkraut in your kitchen, you probably will be heating it, so you will also kill or inactivate the bacteria.


It may not always be the case for some fermented products to be treated. For those, a very high number of live bacteria will be present at the end of the fermentation.


Yes and no. First of all, let’s recap about what a starter culture is. This is a preparation containing  a high concentration of desired microorganisms that will start and assist a fermentation by making specific chemical, smell and taste changes. Thus, the process becomes efficient, controllable, predictable and… safe!

Happy accidents

Fermented foods were born as “happy accidents” when in the early times suddenly “spoiled” food turned long-lasting and pleasant-tasting. Such accidents were possible thanks to spontaneous or natural fermentation, an event in which you only rely on the microbes present in the environment or the food to colonize the raw materials. If you opt to go for this kind of fermentation, be aware of the risk of contamination. You should take extra care about many aspects such as: acidity, oxygen, temperature, moulds, etc. By not having a proper control over the fermentation, it is possible that you may have an outgrowth of non-friendly microbes in your food. These can produce offflavours or even toxic compounds that can put your health in danger.


Using a starter is not a must but as you can see, it definitely gives you many advantages. This includes a fast acid formation that makes the development of non-desired bacteria much more difficult. What is also important is that, in principle, the quality of commercial starters is checked and you can get information if the microbes present can produce potential compounds that could lead to unpleasant effects including headache, diarrhea, etc.