PROBLEM TO BE SOLVED: To provide a preparation that can maintain anti-norovirus activity of a lysozyme modified product even after storage for a long period of time, and a method for producing the preparation.SOLUTION: There is provided lysozyme modified product-containing powder of a lysozyme modified product, in which anti-norovirus activity regulated below when the powder is stored for 4 weeks under the condition of 40°C and 75%RH is 2.0 or more, a reduction value of anti-norovirus activity before and after the storage is 3.0 or less, and pH of solution obtained by dissolving the powder into deionized water so as to be 2 wt.% in terms of the solid content is less than 5.0. Anti-norovirus activity: when norovirus mixture, which is obtained by mixing the equal amount of norovirus solution and the lysozyme modified product-containing powder solution containing a lysozyme modified product by 2 wt.% in terms of the solid content, is left to stand for 1 minute at 25°C, a value obtained by subtracting a logarithm of an infectivity titer after leaving to stand from a logarithm of an infectivity titer before leaving to stand.SELECTED DRAWING: None【課題】長期間保存後もリゾチーム変性物の抗ノロウィルス活性を維持しうる製剤、及びその製造方法を提供すること。【解決手段】リゾチーム変性物のリゾチーム変性物含有粉末であって、 ４０℃、７５％ＲＨの条件下で４週間保存されたときの下記に規定される抗ノロウィルス活性が２．０以上であり、 前記保存前後における抗ノロウィルス活性の低下値が３．０以下であり、 かつ 固形分換算で２質量％となるように脱イオン水に溶解させてなる溶液のｐＨが５．０未満である、リゾチーム変性物含有粉末。 抗ノロウィルス活性：ノロウィルス液と、リゾチーム変性物を固形分換算で２質量％含有する上記リゾチーム変性物含有粉末水溶液とを等量混合して得られたノロウィルス混合液を２５℃で１分間放置した時の、放置前の感染価の対数から放置後の感染価の対数を引いた値。【選択図】なし
