A microwave-resistant and waterproof security tag for use with food products, especially meat products. The security tag includes a pair of single, open loop conductive traces in between which is disposed a similarly-shaped dielectric layer. This combination is encapsulated within plastic membranes or covers that are sealed at their common edges. The preferred embodiment includes rectangularly-shaped single, open loop conductive traces with rounded corners and with one end of each trace forming a capacitor plate. The width of each trace is at least 1/10 of the length of the security tag.