In recent years, along with the advent of an aging society, the number of patients who are administered a nutrient through a feeding tube as a means of administering the nutrient to old persons for whom oral administration is difficult has increased. In particular, since percutaneous endoscopic gastrostomy (PEG) which can easily form a gastric fistula using an endoscope has been developed, PEG has been widely used as a safe and effective nutrient administration means. However, some problems on nutritional management for PEG patients have been reported. For example, gastro-esophageal reflux, enteral nutrient leakage, diarrhea, or the like can be given. These conditions may often cause a serious complication that threatens the life of patients, such as aspiration pneumonia, infectious diseases, or dehydration. It has been noticeably reported that the above conditions are considered to occur because the enteral nutrient is a non-physiologic liquid, and as a countermeasure thereagainst it is effective to solidify the liquid nutrient or adjust the viscosity of the liquid nutrient.
Several inventions have been conceived based on the above finding. For example, a semi-solid enteral nutrient that has a hardness approximately equal to that of pudding or steamed egg hotchpotch by adding agar or a whole egg as a semi-solidifying agent has been disclosed (see Patent Documents 1 and 2, for example). A food for preventing dumping which comprises a thickener selected from low-methoxyl pectin, alginic acid, and carrageenan has been disclosed (see Patent Document 3, for example). This food is injected into a stomach through a tube before and after administration of a nutrient to form a solid in the stomach. This prevents a rapid inflow of the nutrient into the intestine to prevent transient hyperglycemia (dumping syndrome). In addition, a tube-feeding nutrient which can prevent gastro-esophageal reflux and dumping syndrome, can be administered at a desired viscosity within a short time without uncomfortably affecting a patient and a nurse, and can be prepared safely and easily, has been disclosed (see Patent Document 4, for example). As a thickener used in the tube-feeding nutrient guar gum, carrageenan, carboxymethyl cellulose, xanthan gum, chitin, chitosan, or the like can be exemplified. Gelatin, locust bean gum, gellan gum, glucomannan, curdlan, or the like has been generally used for a jelly food and the like in addition to the above-mentioned thickener and gelling agent.
However, these conventional technologies have problems in that even if the products are solid, some solid products are dissolved or disintegrated due to the gastric pH and gastric peristalsis to disappear the shape thereof, solid (gel) forming capability is reduced or lost during retort sterilization due to lack of heat resistance, the solid products must be pressed into by strong force during PEG tube administration using a syringe or the like because the solid increases the viscosity and the tube sometimes may be clogged, or the products may change in form due to separation of water or the like during storage. For example, the enteral nutrient solidified using agar or a whole egg (Patent Documents 1 and 2) exhibits fragile nature in a stomach and is discretely disintegrated and thus gastro-esophageal reflux cannot be prevented sufficiently. In particular, water is separated in the enteral nutrient solidified using agar or a whole egg (Patent Documents 1 and 2) during distribution or long-term storage. There are problems that when the enteral nutrient in which water has been separated is administered to a patient, gastro-esophageal reflux, nutrient leakage, or the like occurs.
A nutrient solidified using the food disclosed in Patent Document 3 can maintain its form in an acidic stomach. However, when the gastric pH has changed due to the inflow of a neutral liquid such as an intestinal juice or the like, the nutrient is easily dissolved or disintegrated to acquire flowability and thus the risk of gastro-esophageal reflux may occur. Patent Document 4 describes only a viscous tube-feeding nutrient, but is silent about the solid form-maintaining capability in a stomach, resistance against thermal sterilization, and a change in form during storage of the product due to separation of water or the like. Therefore, a drug product that can solve the above-described problems cannot be prepared.
From these circumstances, in the above-mentioned conventional technologies, a gel-type nutrient which has excellent solid form-maintaining capability in a stomach, exhibits a property of easily passing through a tube, shows a very little change in shape during storage of the product due to separation of water or the like, and has heat resistance tolerating retort sterilization could not be produced. In particular, there is a big problem that water is separated in an enteral nutrient during distribution or long-term storage, and the enteral nutrient in which water has been separated occurs gastro-esophageal reflux, or nutrient leakage when the nutrient is administered to a patient.    Patent Document 1: JP-A-2003-201230    Patent Document 2: JP-A-2004-26844    Patent Document 3: Japanese Patent No. 3140426    Patent Document 4: JP-A-2004-217531