Structural and Textural Quality of Kinu‐Tofu Frozen‐then‐Thawed at High‐Pressure

Abstract

ABSTRACT To determine effects of high‐pressure thawing on quality of high‐pressure frozen tofu, kinu‐tofu (soybean curd) was frozen 90 min at ca −20°C at 100 MPa (ice I), 200 MPa (liquid phase), 340 MPa (ice III), 400, 500 or 600 MPa (ice V), then thawed at the same pressure. Texture and structure of this tofu (D) were compared with high‐pressure‐frozen tofu thawed at atmospheric pressure (A: 90 min frozen; B: 90 min frozen then 2 days at −30°C; C: 160 min frozen). When tofu was frozen at 200‐ 500 MPa, ice crystals were largest to smallest in B > A and C > D; pore size of D was the same as untreated tofu. Results indicated ice crystals never grew when frozen at 200–500 MPa. Growth occurred during reduction of pressure at ca −20°C, frozen storage or while thawing at atmospheric pressure due to phase transition.