Nano fish bone prepared by high-energy media milling extends the shelf life of tofu during cold storage: Unlocking the restriction on water mobility.

Nano fish bone (NFB) was produced by high-energy media milling. The NFB was composed of circular crystals (approximately 110 nm) and fibrous collagen/peptide. Effects of NFB on the quality and microorganisms of glucono-d-lactone (GDL)-induced tofu stored at 4 °C were investigated. Water activity, syneresis, whiteness, and total bacterial counts of the tofu without NFB increased continuously, reaching 0.977, 41.66 %, 80.28, and 4.55 log CFU/g over 7 days, respectively. Breaking force and penetration distance decreased by 12.93 and 21.79 %, respectively. Adding NFB significantly increased GDL tofu's breaking force and penetration distance during storage (p < 0.05) while decreasing water activity, syneresis, whiteness, and total bacterial counts (p < 0.05). With NFB, nuclear magnetic resonance (NMR) analysis showed reduced free water and increased immobilized water. 16S RNA sequencing revealed lower bacterial diversity and Pseudomonas abundance in NFB-treated tofu. By restraining water mobility, NFB effectively extends GDL tofu's shelf life by 2 days.