PROBLEM TO BE SOLVED: To provide a water-soluble composition or an aqueous solution which can effectively prevent discoloration or browning of natural foods (for example, discoloration of pulp of avocado, meat or fish meat, and the like), which are liable to be oxidized to discolor, even when the target of preventing discoloration or browning changes.SOLUTION: Provided is an alkaline composition or an aqueous solution for preventing discoloration which maintains a reduction state with carbon dioxide in an alkaline region and captures dyes by a chelating effect to suppress oxidation of polyphenols and myoglobin for a long period, comprising a water-soluble composition comprising as active constituents (1) an organic acid or an alkaline or alkaline earth metal salt thereof such as acetic acid, ascorbic acid, citric acid, tartaric acid, and the like, (2) an alkaline metal or alkaline earth metal carbonate, and (3) alum, where the alkali metal or alkaline earth metal carbonate is decomposed in an aqueous solution of the organic acid or a salt thereof to generate a carbon dioxide gas in a weakly alkaline region (pH: approximately 8). Further provided is the alkaline composition or the aqueous solution for preventing discoloration containing glucomannan as a thickener.SELECTED DRAWING: None【課題】酸化されて変色し易い天然食品（例えばアボガド果肉や畜肉魚肉等の変色）に対する変色、褐変防止の対象が変わっても有効に変色、褐変を防止することができる水溶性組成物又は水溶液の提供。【解決手段】アルカリ性域での炭酸ガスでの還元状態の確保し、色素をキレート効果で捕捉して長時間ポリフェノール及びミオグロビンの酸化するもので、（１）酢酸、アスコルビン酸、クエン酸、酒石酸等の有機酸、又はそのアルカリ金属又はアルカリ土類金属塩、（２）アルカリ金属又はアルカリ土類炭酸塩、（３）ミョウバンを有効成分とする水溶性組成物であって、有機酸又はその塩の水溶液中でアルカリ金属又はアルカリ土類金属炭酸塩を分解し、弱アルカリ性（ｐH８前後）領域で、炭酸ガスを生成させる変色防止用アルカリ組成物又は水溶液。更に増粘剤としてグルコマンナンを含む変色防止用アルカリ組成物又は水溶液。【選択図】なし
