Preserving agent and preserving method

Details Preserving agent and preserving method Preserving agent and preserving method

1999-08-23

2001-03-13

Pratt, Helen (Department: 1761)

Food or edible material: processes, compositions, and products

Inhibiting chemical or physical change of food by contact...

C426S573000, C426S618000, C426S634000

Reexamination Certificate

active

06200619

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a preserving agent and to a preserving method.
BACKGROUND ART
Organic acids, inorganic acids, ethanol and glycine are commonly used to prevent degeneration and improve the shelf-life of food products (Japanese Unexamined Patent Publication No. 56-109580, 57-43668, 58-138367).
Various foods have been screened for food-preserving substances in recent years, resulting in the discovery of such preservatives as polylysine, protamine, lysozyme, etc., in addition to synthetic chemical products; however, since these preservatives exhibit exceedingly strong antibacterial activity only against certain specific bacteria, they are not adequate as general food preservatives. In order to achieve satisfactory preservation it is necessary to add large amounts of these substances to foods, which is undesirable because of their high price which increases overall costs.
In addition to these substances, spices which have long been used in foods have also been reported to contain substances exhibiting antibacterial activity, but they also fail to fully satisfy the conditions required for food preservatives.
As mentioned above, preserving agents used in foods and drinks will preferably exhibit a continuous antibacterial effect for preservation over long periods with minimal amounts of addition, and when used in foods they must not impair their taste or texture.
Because widely used food preserving agents such as ethanol, glycine, organic acids and inorganic acids themselves have characteristic flavors and aromas, they cannot be added to foods and drinks in amounts required to provide adequate preservation effects. Also, natural substances such as polylysine, protamine and lysozyme have very weak antibacterial spectra, and thus while exhibiting strong antibacterial activity against specific bacteria they are not effective against most microbes responsible for degeneration of foods, and therefore cannot be considered as satisfactory preserving agents.
DISCLOSURE OF THE INVENTION
As a result of diligent research in the light of these circumstances, the present inventors have found that water-soluble hemicellulose, and especially bean-derived water-soluble hemicellulose, exhibits antibacterial activity and can be effectively employed as a preserving agent for foods and drinks. In particular, water-soluble hemicellulose is effective for foods with water activity (AW) of 0.8 or greater, for example foods such as kneaded marine products (AW=0.8 or greater), raw noodles (AW=0.85) and vegetable salad (AW=0.9 or greater). When water-soluble hemicellulose is used as a preserving agent for foods and drinks, adequate antibacterial activity should preferably be achieved with only a small amount, and further diligent research by the present inventors has resulted in the finding that using the water-soluble hemicellulose in combination with ethanol, glycine, sorbic acid, benzoic acid and their salts, organic acids such as acetic acid, fumaric acid, adipic acid and their salts, lower fatty acid esters, sugar esters, polylysine, protamine, lysozyme, mustard extract, horseradish extract, chitosan and the like results in notably enhanced antibacterial activity. The present invention has been completed based on these findings.
In other words, the present invention provides preserving agents containing water-soluble hemicellulose as an effective component, preserving agents containing (A) water-soluble hemicellulose and (B) one or more selected from the group consisting of ethanol, glycine, sorbic acid, benzoic acid and their salts, organic acids such as acetic acid, fumaric acid, adipic acid and their salts, lower fatty acid esters, sugar esters, polylysine, protamine, lysozyme, mustard extract, horseradish extract, chitosan and phytic acid as effective components, and a preserving method comprising the combined use of (A) water-soluble hemicellulose and (B) one or more selected from the group consisting of ethanol, glycine, sorbic acid, benzoic acid and their salts, organic acids such as acetic acid, fumaric acid, adipic acid and their salts, lower fatty acid esters, sugar esters, polylysine, protamine, lysozyme, mustard extract, horseradish extract, chitosan and phytic acid.
BEST MODE FOR CARRYING OUT THE INVENTION
The water-soluble hemicellulose according to the present invention is preferably derived from beans, especially soybeans, and particularly from the cotyledon. Also, a lower protein content of the soybean hemicellulose is preferred, and specifically it is preferred to be no greater than 5%.
The water-soluble hemicellulose can be of any molecular weight, but a high molecular substance is preferred, especially an average molecular weight of a few thousand to a few million, and specifically 5000 to one million. If the molecular weight is too large the viscosity will increase, thus lowering the handleability. The average molecular weight of the water-soluble hemicellulose is the value determined by the limiting viscosity method wherein the viscosity of a 0.1 M NaNO
3
solution is measured using standard pullulan (product of Showa Denko, KK.) as the standard substance. Measurement of uronic acid was carried out by the Blumenkrantz method and measurement of neutral sugars was carried out by the GLC method after alditol acetation.
The water-soluble hemicellulose is either obtained by water extraction from the hemicellulose-containing starting material or, if necessary, by heat elution under acid or alkali conditions, or it may be eluted by decomposition with an enzyme. The following is an example of a method for producing water-soluble hemicellulose.
Suitable starting materials to be from plants include the husks of oily seeds of soybean, palm, coconut, corn or cottonseed with the oil and protein removed, and lees from grains such as rice or wheat with the starch and other parts removed. If the starting material is soybeans, then okara (bean-curd refuse) which is a by-product from preparation of tofu (bean curd) and soybean milk or separated soybean protein may also be utilized.
These starting materials may be subjected to heat decomposition at a temperature preferably of from 80° C. to 130° C., and more preferably from 100° C. to 130° C., under either acidic or alkali conditions but preferably at a pH near the isoelectric point of each protein, and after fractionation of the water-soluble fraction, it may be dried directly or subjected to activated carbon treatment, resin adsorption treatment or ethanol precipitation to remove the hydrophobic substances or low molecular substances, and then dried to yield the water-soluble hemicellulose. Decomposition extraction may also be carried out with hemicellulase or pectinase.
Water-soluble hemicellulose is a polysaccharide containing galactose, arabinose, xylose, fucose, glucose, rhamnose and galacturonic acid as constituent saccharides. A detailed analysis of the constituents of water-soluble hemicellulose as obtained by hydrolysis may be found in Japanese Unexamined Patent Publication No. 4-325058.
Water-soluble hemicelluloses of large molecular weight have viscosities proportional to their molecular weight, and therefore the viscosity may be used as an index for limiting the suitable range of water-soluble hemicellulose which can be utilized as a preserving agent for foods and drinks. That is, the water-soluble hemicellulose used as a preserving agent according to the invention preferably has a viscosity of 10 mPa.s or greater (measured with a Brookfield rotational viscometer in a 10% aqueous solution at 25° C.), more preferably 50 mPa.s or greater, and even more preferably 80 mPa.s or greater, in a 10% aqueous solution at 25° C. The water-soluble hemicellulose can be used so long as its solution viscosity is less than 1000 mPa.s.
The water-soluble hemicellulose of the invention may be used alone as a preserving agent, or it may be used in combination with one or more known compounds for an improved antibacterial activity. Appropriate substance groups are discussed below.
Ethanol and glycine may be

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