| 摘要 |
<p>A method of indicating whether a food article has undergone a freeze-thaw sequence by applying to the food article an indicator including a first material (3) enclosed within microcapsule walls (4), and a second material (5) normally separated from the first material by the microcapsule walls. The two materials include substances which produce a color change when brought into contact with each other, but which are normally separated from each other by the microcapsule walls. The first material further includes a liquid, preferably water, which when frozen expands sufficiently to rupture the microcapsule walls (Fig. 26), such that when the first material is thawed, it comes into contact with the second material producing a color change indicating that the food article has undergone a freeze-thaw sequence.</p> |
