By Stephen Daniells
11-Aug-2008 -
A dried stock made from the bonito fish – a stock used extensively in Japanese cuisine – may improve the palatability of reduced-salt products, suggests new research.
Promising results published in the Journal of Food Science indicate that the salt content of certain food products could be reduced by 15 percent without affecting palatability.
“The results of these sensory evaluations indicated that the characteristic flavor of dried bonito stock induced saltiness enhancement,” wrote M. Manabe from Doshisha Women’s College of Liberal Arts in Kyoto.
“In everyday Japanese food, the flavor of dried bonito stock could enhance saltiness and prevent the loss of palatability that would otherwise result from reducing the salt content.
“This finding is expected to be useful for improvement of the palatability of salt-reduced food,” added Manabe.
A body of evidence has linked excess salt (sodium chloride) in the diet to an increased risk of high blood pressure and stroke. Campaigns are underway around the world to encourage consumers to reduce their daily intake. The UK's Food Standards Agency (FSA), for example, advises that adults should consume no more than six grams of salt a day.
While an important part of reformulating foods to contain less salt lies with enhancing the taste of the salt that is there, ingredients companies are collaborating with their customers to do their part in reducing sodium in the individual components that go in to a finished product.
Study details
The Japanese researcher performed two sensory evaluations. In the first, which used a model system, the saltiness of a salt solution containing 0.8 percent sodium chloride was achieved with only 0.68 percent sodium chloride when used in combination with the dried bonito stock (six percent).
On the other hand, no enhancement of saltiness was observed when 0.12 percent monosodium glutamate (MSG) was used.
In the second evaluation, the dried stock was tested in two Japanese foods – a traditional soup and a steamed egg custard.
While no salt-enhancement was observed in the soup, wrote Manabe, a reduction of the salt content by 15 per cent did not affect the perceived palatability.
When formulated into the custard, however, saltiness and palatability were enhanced by the fish stock.
“These results suggested that the dried bonito egg custard was considered palatable even if the NaCl concentration was decreased to 0.75 percent,” wrote Manabe.
Chemistry behind bonito
According to Manabe: “The characteristic flavor of dried bonito stock is very popular with the Japanese. Inosine 5'-monophosphate (IMP), another typical umami substance, is known to be a major contributor to the flavor that has ensured the popularity of dried bonito as a stock.
“In addition to IMP, the stock contains various taste active components, including glutamic acid, histidine, lactic acid, and others. Moreover, the aroma of dried bonito stock is also an important factor in its desirability.”
Source: Journal of Food Science
August 2008, Volume 73, Issue 6, Pages S321-S325, doi: 10.1111/j.1750-3841.2008.00844.x
“Saltiness Enhancement by the Characteristic Flavor of Dried Bonito Stock”
Author: M. Manabe
Wednesday, September 10, 2008
Dried fish stock may be salt enhancer for food
Tuesday, September 9, 2008
Katsuobushi (dried bonito) itself has no anti-hypertensive activity
Katsuobushi (dried bonito) Oligopeptide is food derived from Katsuobushi protein by enzymatic reaction. However, eating Katsuobushi itself does not show any anti-hypertensive activity. The reason is that peptides derived from different enzymes show different biochemical activities even if obtained from the same protein. When you take Katsuobushi itself, it is hydrolyzed by digestive enzymes such as pepsin, trypsin and chymotrypsin, secreted from stomach or intestine. Katsuobushi Oligopeptide, on the other hand, is made by an enzyme called gthermolysin (it is secreted by Bacillus thermoproteolyticus, one of Bacillus natto line)h. Katsuobushi Oligopeptide is never produced in human body because no enzyme, which has the same activity with thermolysin, is available in digestive systems.
Enzymatic digests of Katsuobushi by pepsin, trypsin or chymotrypsin indicated any anti-hypertensive activity in animal experiment (Table 1).
Table 1: Effect of enzymatic digests of Katsuobushi on lowering blood pressure
--------------------------------------------------------------------------------
Enzyme Effect of lowering
blood pressure
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Thermolysin
(Katsuobushi Oligopeptide) 30 mmHg
Pepsin
(digestive enzyme secreted in stomach) 0
Trypsin
(digestive enzyme secreted in intestine) 0
Chymotrypsin
(digestive enzyme secreted in intestine) 0
--------------------------------------------------------------------------------
Thermolysin is a safe enzyme, used for food processing such as meat softening or making seasoning (aspartame). It is allowed to use as a food additive in Japan.
2, Katsuobushi Oligopeptide made from natural bonito (non-dried bonito) does not show anti-hypertensive activity either
Thermolysin digests of non-dried bonito protein obtained no oligopeptides with anti-hypertensive activity.
The reason is assumed as follows:
During a Katsuobushi (dried bonito) manufacturing process, bonito meat is treated with special fungi for a while. It seems that proteases secreted from the fungi are closely contributed to ACE-inhibitory activity.
Katsuobushi Oligopeptide
1, What is gKatsuobushi (dried bonito) Oligopeptideh ?
gKatsuobushi (dried bonito) Oligopeptideh described below is protease digests of Katsuobushi (dried bonito), a Japanese traditional seasoning made of bonito muscle.
Protein made of over one hundred amino acids is converted to amino acids by digestive enzymes, when it is taken into human body. Protein is not completely digested to each amino acid at one time, but is partially hydrolyzed to peptides, consisting of two to ten amino acids, and then gradually decomposed and absorbed through digestive organs into body. During this decomposition process, amino acid sequence less than ten amino acids is called gOligopeptideh.
What is Katsuobushi?
Katsuobushi is a Japanese traditional food and has 1500 years of history. Down the ages, Japanese have used it to make soup stock and to season the food.
This is Katsuobushi oligopeptide derived from Katsuobushi.
2, Katsuobushi (dried bonito) Oligopeptide shows anti-hypertensive activity
Oligopeptides are produced from any food protein taken into human body. Primary structure of the oligopeptide will be changed and are depend on a kind of raw material protein or proteases worked because each protein has its own amino acid sequence and each digestive enzyme has different decomposing activity. In short, in some cases, protein can produce especially useful oligopeptides to human body and others do not.
Recently, gKatsuobushi Oligopeptideh was found with anti-hypertensive activity. Professor Masaaki Yoshikawa, department of Food Science and Technology in Kyoto University, showed that gKatsuobushi Oligopeptideh was obtained from gthermolysinh digest of dried bonito.
3, Katsuobushi (dried bonito) Oligopeptide is converted into active form during digestion
The main component in gKatsuobushi Oligopeptideh, showing anti-hypertensive activity, is a sequence of five amino acids, gLKPNMh (Leu-Lys-Pro-Asn-Met). This amino acid sequence is characteristic of Katsuobushi Oligopeptide. You can not take the same peptide from any other ordinary food or Katsuobushi itself.
LKPNM is converted into gLKPh (Leu-Lys-Pro) and gNMh (Asn-Met) in digestive organs or blood. The converted gLKPh, having anti-hypertensive activity, is called as gActive Formh.
This reaction is important to show the long-lasting and moderate anti-hypertensive activity of Katsuobushi Oligopeptide.
Katsuobushi oligopeptide lowers blood pressure by suppressing blood vessel contraction
Katsuo Dashi - Recipes
Ingredients:
3 1/4 cups water
2/3 oz. katsuobushi (dried bonito) flakes
Preparation:
Put water in a deep pot and heat on medium heat. Just before the water boils, add katsuobushi flakes. When the water boils, skim off any foam that rise to the surface. Stop the heat. Strain the stock through a paper towel.
*Makes about 3 cups
rice with soy-glazed bonito flakes and sesame seeds
We love this recipe as much for the soy-glazed bonito flakes, with their maddeningly good smoky-savory-sweet flavor, as for making such great use of leftovers.
Active time: 15 min Start to finish: 45 min
For bonito-flake topping
Leftover katsuo bushi (dried bonito flakes) from making dashi or 1 cup katsuo bushi fresh from package
1 tablespoon sake
1/4 teaspoon sugar
1 1/2 tablespoons soy sauce
2 tablespoons sesame seeds, toasted
For rice
2 cups Japanese short-grain rice
2 cups water
Make bonito-flake topping: If using katsuo bushi flakes from package, moisten with a few drops of sake or water. Finely chop katsuo bushi, then cook in a dry heavy skillet over moderate heat, stirring frequently, until fragrant and mostly dry. Add sake, sugar, and soy sauce and cook over moderate heat, stirring frequently, until mixture is dry and glazed. Stir in sesame seeds and spread on a plate to cool.
Make rice:
Rinse rice in a bowl in several changes of cold water until water is almost clear; drain well in a large sieve. Combine rice and 2 cups water in a 3-quart heavy saucepan and let stand 10 minutes. Cover with a tight-fitting lid and bring to a boil over high heat. Cook at a rapid boil (lid will be rattling and foam may drip down outside of pan) 5 minutes, or until water is absorbed. Remove from heat and let stand, covered, 10 minutes.
Serve rice with bonito-flake topping.
Cooks' note:
• Bonito-flake topping keeps in an airtight container at room temperature 1 week.
