Softening of lotus root and carrot using freeze-thaw enzyme infusion for texture-modified foods

Freeze-thaw enzyme infusion was used to soften lotus root and carrot, and to develop texture-modified foods. Samples were dipped into 0.25% cellulase solution with different vacuum pressures (0–0.05 MPa), vacuum times (5–30 min), and restoration times (0–120 min). Effects of these treatments on maximum force and pH were determined. Overall, the maximum force and pH of samples decreased as vacuum pressure, and vacuum and restoration times increased. The texture softening rate (K) and residual texture (δ) were obtained from a first-order model, and results showed that the K value of the lotus root increased as vacuum time increased. K and δ values for the carrot decreased as vacuum time increased. A regression analysis confirmed that lotus root texture was strongly influenced by restoration time, while carrot texture was more affected by vacuum time. Overall, color values were lower for untreated samples compared to treated sample. Compared with cooked samples, samples cooked after freeze-thaw enzyme infusion with restoration showed a significantly reduced maximum force by 84% for lotus root and 58% for carrot. These data suggested that treatment with freeze-thaw enzyme infusion followed by restoration before cooking helps soften lotus root and carrot tissue.