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What is Katsuobushi?
Katsuobushi, also known as "okaka", is a preserved food based on fish. It is striated tuna meat or skipjack tuna ( Katsuwonus pelamis, Tribù Thunnini) dried, smoked and fermented.
The Katsuobushi is a derivative of the 1st fundamental food group. Being dehydrated it is very caloric and, in general, concentrated. Contains significant amounts of high biological value proteins, semi-essential omega 3 polyunsaturated fats - eicosapentaenoic acid EPA and docosahexaenoic DHA - water-soluble B vitamins and fat-soluble D, minerals - such as iron and iodine - cholesterol and histamine. However, it is a food considered hygienically unsafe and unsuitable for certain special conditions such as pregnancy. Below we will go into more detail and we will also deepen the related dietary applications.
A variant of Katsuobushi, the "Bonito Flakes" (scales / Bonito petals), is an almost identical preparation but for many of lower quality. The difference lies in the raw material; while the Katsuobushi is obtained from the processing of the K. Pelamis, the Bonito Flakes is based on fish from the Sardini tribe - for example the genus Cybiosarda, Gymnosarda, Orcynopsis, Sarda etc.
The "karebushi", a traditional variant of Katsuobushi, is inoculated with the fungus Aspergillus glaucus which helps to reduce the humidity. Cases of intoxication due to the presence of mycotoxins in Katsuobushi produced by the micro-organism have occurred.
The Katsuobushi has a very intense flavor, sapid taste and very pronounced umami - attributable to the high content of inosinic acid. According to some research, the Katsuobushi is also responsible for a sensation, recently discovered, called kokumi (in English "heartiness" or "mouthfulness").
deepening
According to some Japanese researchers, food kokumi - or "heartiness" or "mouthfulness" - is a gustatory sensation related to some γ-L-glutamyl peptides capable of activating a receptor sensitive to calcium and glutathione.
Katsuobushi flakes and dried kelp - kombu - are the main ingredients of "dashi", a broth used as a base for many soups (such as "miso") and various sauces (for example "soba no tsukejiru") in Japanese cuisine.
Supporting the Katsuobushi with flakes on hot food, it "moves" by the action of the convective motion of the hot air, giving the dish a unique appearance.
Nutritional Properties
Nutritional properties of Katsuobushi
Katsuobushi is a food preserved for dehydration. Water shortage is responsible for the percentage increase of all nutrients.
Containing proteins with high biological value, specific vitamins and minerals, Katsuobushi is a derivative that belongs to the first fundamental food group.
It is very caloric. Energy is supplied mainly by peptides, followed by lipids and traces of carbohydrates. The amino acid profile outlines a high biological value of proteins. The fatty acids are mainly polyunsaturated, with great importance of the semi-essential omega 3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); carbohydrates are simple. It should however be specified that EPA and DHA are very delicate nutrients that are sensitive to both heat and oxidation. It is therefore conceivable that the Katsuobushi does not actually contain all the aforementioned semi-essential omega 3 fatty acids.
The cholesterol intake is significant; the fibers are absent. Katsuobushi does not contain lactose or gluten; it is rich in histamine and purines.
From the mineral point of view, Katsuobushi is an excellent source of phosphorus, potassium, iron, iodine, selenium, zinc and magnesium. As for vitamins, it shows significant concentrations of the liposoluble vit D, and of the water-soluble: thiamine (vit B1), riboflavin (vit B2), niacin (vit PP), pyridoxine (vit B6), biotin (vit H or B8) and cobalamin (vit B12). Also the values of vitamin E (alpha tocopherol) and pantothenic acid (vit B5) are discrete.
Diet
Katsuobushi in the diet
Katsuobushi is a food to be used in marginal quantities in the diet.
The strong nutritional concentration makes it useful for achieving many needs, including especially those of minerals and vitamins. As we have anticipated, the profile of fatty acids would be of excellent quality, nevertheless it is very likely that the processing and storage significantly reduce the final content of EPA and DHA. This means that the Katsuobushi is not, in spite of appearances, a good nutritional source of metabolically active omega three (eicosapentaenoic acid and docosahexaenoic acid).
The Katsuobushi, whose portion of use is always very reduced (5-10 g), despite being quite energetic, can also be used in the diet against overweight and metabolic pathologies. It has no contraindications in case of obesity, type 2 diabetes mellitus, hypertriglyceridemia, hypercholesterolemia and arterial hypertension. On the contrary, if the concentration of omega 3 fatty acids were intact, it could even be considered beneficial in the fight against diseases of the spare.
It must however be remembered that the Katsuobushi has a high cholesterol content. Nevertheless, the reduced portion does not significantly affect the overall contribution of the sterol, making it suitable even in the case of hypercholesterolemia.
One of the fundamental aspects that distinguishes Katsuobushi from other typical European preserved fishery products is the low presence of sodium. On the contrary, bottarga and cod, for example, are contraindicated in the case of sodium-sensitive hypertension. This does not apply to Katsuobushi which, being not dehydrated with salt but through smoking, radiation and fermentation, has a perfectly tolerable sodium concentration even for hypertensives.
Katsuobushi is a food that contributes to increasing the intake of iodine, zinc, selenium, phosphorus, potassium and magnesium. Extremely scarce in the diet, iodine is of fundamental importance for the good functioning of the thyroid gland (which regulates cellular metabolism). The abundance of iron can be useful in the case of iron deficiency anemia. Zinc and selenium, on the other hand, are powerful antioxidants. Potassium and magnesium, alkalizing substances very involved in nerve conduction, are often lacking in athletes and in all those who sweat profusely. Phosphorus is essential for bone metabolism, nervous tissue, etc .; it is almost never lacking.
The generous concentration of vitamin D makes it excellent for the diet of children and the elderly, who need a fully functioning bone metabolism. It is also necessary for the functioning of the immune system. The water-soluble of group B are coenzymatic elements necessary for multiple cellular type reactions.
Being rich in purines, Katsuobushi should be avoided in the diet against hyperuricemia and gout. Furthermore, since it is a preserved fish, it is very likely that it contains high amounts of histamine and is therefore contraindicated for food intolerance. It is instead pertinent for lactose intolerant and for celiacs.
Katsuobushi is a smoked food. This means that it contains significant levels of combustion residues which, as is now known, are involved in the carcinogenesis of the digestive tract (esophagus, stomach and intestine). The Katsuobushi is therefore not recommended for those who are familiar or other risk factors for cancer of the esophagus, stomach and intestines.
Katsuobushi is also a food unsuitable for pregnant women and those suffering from compromised immune systems (immunosuppressed, HIV-infected, etc.). Being cooked during processing, this derivative is totally free of parasites; there is no risk of carrying Anisakis. However, it is inoculated with A. glaucus which, as we shall see in the next section, may be responsible for food poisoning due to the production of fungal toxins. Moreover, the foods stored in this way have greater risks of containing dangerous bacterial colonies such as, for example, Listeria monocytogenes (the bacterium perhaps the most dangerous to contract in pregnancy).
Katsuobushi does not lend itself to vegetarian and vegan diets. Buddhists and observant Hindus reject their use.
The average portion of Katsuobushi is, as we have said, 5-10 g (17-35 kcal).
Katsuobushi and mycotoxins
Katsuobushi, like miso and soy sauce, has been responsible for the spread of foodborne illnesses. Fungal fermentation of some strains of A. glaucus can in fact cause the production of mycotoxins.
Let's not forget that Katsuobushi is a smoked food. The smoking, applied by burning of vegetable products, increases the concentration of benzopyrene in addition to the EU standards and up to 37 μg / kg. For this, they have been withdrawn from the market and banned all over Europe.
Kitchen
How to use the Katsuobushi in the kitchen?
According to Japanese tradition, the Katsuobushi should be cut into flakes only when needed, using a tool called "katsuobushi kezuriki". Today, on the other hand, Katsuobushi is more frequently marketed already prepared and stored in special plastic airtight bags, even though its fragile consistency makes it particularly sensitive to crumbling.
There are basically two types of Katsuobushi in a bag:
- "Hanakatsuo", small and thin, used as a condiment for many Japanese dishes such as "okonomiyaki"
- "Kezurikatsuo", thick and thick, used more generally for "dashi".
Katsuobushi is not a product commonly used in Italian cuisine. Today, the starred chefs who work to cross the world's gastronomic traditions, also use this ingredient together with seaweed, soy and derivatives, soy sauce, etc. However, the only local products that can be traced, in some way, to the organoleptic and gustatory characteristics of Katsuobushi are: salami and tuna ham, bottarga and various smoked fish.
In addition to the famous "dashi", other culinary uses of katsuobushi are:
- Okaka: the Katsuobushi must be finely chopped and seasoned with soy sauce
- Filling for "onigiri" (rice balls)
- Seasoning for rice: "bento" is widely known, covered with nori seaweed strips (laver)
- Dried Okaka: used as an ingredient for covering furikake rice (called "okaka furikake").
- Condiment for cold tofu or "hiyayakko", together with grated ginger and winter onion or spring onion
- Condiment for "zarusoba" (cold soba noodles), along with sesame seeds and nori seaweed
- Seal for "takoyaki" and "okonomiyaki"
- Seasoning for secular or "pidan" eggs - duck eggs, hen, quail etc., stored for weeks or months in a mixture of clay, ash, salt, quicklime and rice bran - together with sesame oil and salsa di soy
- Nutritional treatment with high protein content for cats, sold in pet stores (read: Barf Diet)
- "Ramen" seal mixed with salt.
Production
Production of Katsuobushi
Katsuobushi is a tuna fillet based food. The fish must therefore first be beheaded, gutted and filleted. The fat area of the belly, that is the ventresca, due to the high lipid concentration does not lend itself to conservation and is eliminated. The fillets are placed in a basket, immersed in water and cooked just below the boiling point for 60-90 ', depending on the size. At this point the ventral spines are removed.
The fillets are then smoked using oak wood, pasania or castanopsis; this process can take up to a month. They are smoked for 5-6 hours, left to rest for a day - so that the deep humidity of the meat has time to surface - then dried with heat and smoked again the next day, repeating this cycle 12-15 times. The tar that has accumulated on the surface due to smoke is removed from the surface of the food. At this stage the fillets are called "aragatsuo" and are commonly found in the form of flakes already packaged for sale under the name "katsuo-kezuri-bushi" or "hanakatsuo". Note : without the stage of final fermentation it is not yet possible to speak of katsuobushi, but it is still considered a good substitute.
The last phase of Katsuobushi is drying in the sun and fermentation with mold. The fillets are then inoculated with Aspergillus glaucus and left indoors for 2 weeks. Microorganisms ferment the fillets and eliminate residual moisture.
The Katsuobushi is further dehydrated in the sun to increase its hardness and dryness, until it takes the appearance of "a piece of wood" and does not reach 20% of its initial weight. A fresh 6 kg fillet can weigh only 1 kg at the end of the process. Only the fillets processed in this way, by definition, can be referred to as Katsuobushi. However, after repeating this process of mold growth and sun drying at least twice, the Katsuobushi can also be called "karebushi"; the fillets that repeat this process more than three times are also called "honkarebushi" (true dried fillet). When tapped one another, they emit an almost metallic sound and, unlike their opaque beige exterior color, they show an intense and shiny ruby color inside. Although rarely, very high quality honkarebushi can repeat this drying process for over two years.
