Compressed tablets are confections created through the compression of dry ingredients, resulting in a firm mass with a predetermined shape. This type of product was initially developed within the pharmaceutical industry to facilitate the precise and controlled delivery of active ingredients. In the early stages, the active ingredient was mixed into a dough in precise proportions, rolled into sheets, cut, and then dried. However, as the process evolved, it shifted to exclude water from the formulation. Instead, a blend of powdered ingredients was utilized, poured into molds, and compacted. Sufficient pressure was applied to enable the physical rearrangement and, in some cases, chemical bonding of the powder particles, resulting in the formation of solid tablets. Under pressure, smaller particles found their place in the interstitial spaces between larger ones.

This process was later adopted by the confectionery industry, where sucrose or dextrose crystals served as the foundational ingredients for sugar confections, while Maltitol and sorbitol were chosen for sugar-free confections. 

An essential consideration when working with ingredients for compressed tablets is the particle size and compressibility. Certain ingredients can be compacted directly, while others, like sucrose or dextrose, require pre-treatment to attain a powder suitable for compression. These pre treatments could be wet granulation or dry granulation. Also, there are some ingredients, known as directly compacting ingredients (such as sucrose and dextrose), that are available with pre-treatments making them suitable for direct compression. The characteristics of the resulting tablet are contingent upon factors like granulation size, the type of press used, and the conditions of compaction.

Throughout all steps, careful control of environmental conditions is vital since many powders are hygroscopic. Thus, maintaining low relative humidity in the air is essential. High humidity can cause powders to lose their free-flowing capacity and become sticky. Similarly, elevated temperatures can have the same effect on some ingredients.

Ingredient preparation: Ensuring the powder is suitable for compaction is crucial. These pre-treatments are dry or wet granulation. The wet granulation method involves mixing the powder with a binder to create a paste. This paste is then dried (with a moisture content of 0.2-0.8%) and pulverized back into a powder to achieve the required particle size. High torque mixers are necessary to ensure thorough mixing for the wet granulation method. On the other hand, the dry granulation method begins with pulverization, followed by wet mixing with a lubricant, compaction into pellets, and a final pulverization step to achieve the desired granulation. Maintaining a uniform particle size is crucial to prevent issues during the compaction step.

Mixing and blending: The candy base, flavoring agents, sweeteners, and colorants are meticulously mixed to create a uniform mixture. Lubricants are added at the end to ensure complete coverage of the powders.

Tablet formation-compression: The candy mixture is then fed into a tablet press. This press involves a series of steps, with the powder flowing into the unit either by controlled gravity flow or a forced flow feeder. Tablets exit the chute after compression. Within the press, the mixture is compressed between two dies or molds, defining the distinctive shape and size of the candy tablets. Once the dies are filled, the tablet is compressed between two punches. The top punch is then pulled out, and the bottom punch pushes the tablet out of the cavity. Typically, these operations occur continuously within a rotary device.

Polishing (optional): Some candy mints undergo a polishing step to achieve a smooth, glossy appearance.

Compressed tablet formulation is a meticulous process where several critical considerations shape the final product. Particle size plays a vital role in achieving effective compaction, ensuring that the granules fit seamlessly during compression, ultimately influencing tablet hardness and disintegration. Additionally, meticulous attention is given to the chemical interactions among chosen ingredients. Positive interactions, enhancing tablet cohesion and dissolution, are sought, while avoiding negative interactions that might compromise the product quality. Another crucial aspect is the cost-efficiency trade-off between utilizing pretreated ingredients for direct compression versus integrating an additional in-house step for pretreatment. This decision involves assessing the expenses, resources, and overall impact on the production timeline. Furthermore, the correct order of ingredient addition is pivotal to achieve optimal homogenization, ensuring that each component integrates effectively for a uniform mixture that translates into consistent tablet characteristics. This intricate balance of factors is at the core of a successful compressed tablet formulation, harmonizing both quality and efficiency.