Freeze Drying vs Spray Drying: Is It Necessarily Quality vs Cost? | Alaqua INC

In an industry where productivity and profitability are becoming increasingly important, difficult decisions must be made from time to time, as evidenced by the debate over whether to use spray drying or freeze-drying when developing a product process, and it can come down to something as uncomplicated as overhead costs. Alaqua is a spray dryer supplier worldwide based in the US. In order to assist you to decide which is ideal for your project and product, we've weighed the benefits of each.

Which One to Choose?

When liquid stability is inadequate, storage requirements are too severe, or a solid form of the product is sought, freeze-drying is generally recognized in the biopharmaceutical sector as the optimum approach for preserving a wide range of pharmaceutical formulations.

While freeze-drying is the most widely used drying method for a number of materials with varying degrees of sensitivity, research has been conducted to study alternate ways, such as spray drying, due to the costs and often large quantities associated with the approach.

Spray drying, despite being new to the industry, has several advantages, such as the capacity to operate with higher throughput (more continuous than batch) and scalable volumes, making it a feasible alternative for lyophilization, but only in particular circumstances.

Process of Drying

Freeze drying works by freezing a product first, generally in a controlled manner to alter the ice crystal structure, and then placing it in a vacuum to remove the unbound water.

The material is then subjected to secondary drying, which reduces the material's remaining moisture to a user-defined level. Given that the goal at this point is bound rather than unbound/free water, more energy is necessary to accelerate the process by elevating shelf temperatures to +20°C or higher, along with low air pressure, enabling ice to convert straight into water vapor (bypassing the liquid phase).

The careful balance between temperature and vacuum is critical to ensuring a successful batch with minimal influence on product efficacy is created after drying, depending on the type of the sample being dried on a specific lyophilization cycle. Certain items, depending on their inherent sample qualities, may require freeze-drying settings ranging from 12 hours to 5 days to achieve this.

Spray drying is a more straightforward and faster method of turning a liquid solution into a dry powder in one step. The solution is atomized into fine droplets, which are then dried in a huge chamber using heated gas. A cyclone is subsequently used to gather the resultant dry particles.

Although faster and less costly than freeze-drying, one of the major drawbacks is the high processing temperatures/shear pressures it necessitates, which are precisely what many clients in the highly regulated pharmaceutical and biotech sectors prefer to avoid.

In freeze-drying, the product temperatures are typically below 0°C during primary drying and 20-30°C during secondary drying, but in spray drying, the product temperatures are consistently over 80°C.

Working at these higher (80°C) temperatures has the direct effect of lowering sample quality in terms of intrinsic product attributes after drying:

• taste
• efficacy
• nutritional value i.e. nutrients in food products
• smell/color
• proteins degeneration
• biological yield - a greater level of log reduction of cells i.e. bacterial

Industry Usage

Both processes have a wide variety of applications. Freeze drying is commonly used to preserve various fine chemicals/laboratory reagents, cell types, injectable vaccinations, as well as dairy and food products. This processing method is best suited for formulations that do not require further processing after drying, as it is typically performed with product directly filled in vials or other containers; additionally, avoiding potential contamination after the cycle is complete, vials can be sealed in-situ of the lyophilized.

On the other hand, spray drying is more often linked with bulk processing than vial processing. However, there is a frequent assumption that spray drying is only suited for food and solid bulk medicines, while recent research reveals that it may be a viable technology for some complicated items, such as microencapsulated bacteria and nan particulates.

Quality, Efficiency, and Cost

Spray drying is widely acknowledged to have lower costs than freeze drying, which has piqued the interest of some markets; and, because it is more open to higher throughput potentials, spray drying can be considered a "continuous process," as opposed to the batch format associated with freeze drying.

However, while spray drying has a lower 'upfront cost,' this isn't necessarily the truth for more complex compositions. Many coating procedures are required for products that require multiple coating layers, which may be time-consuming and costly. A simpler freeze-dried formulation is a more cost-efficient approach.

Furthermore, freeze drying's strength is in the consistent quality of the output. Low processing temperature accuracy reduces the possibility of inherent product features including eutectic melt, collapse, and glass transition temperatures being surpassed, resulting in high-quality freeze-dried goods. The shear stress that biopharmaceuticals are subjected to during spray drying when paired with the high processing temperatures necessary, can destabilize molecules like proteins and impair product characteristics, resulting in a reduction in product quality, according to research.

Alaqua is processing equipment such as the evaporator, crystallizer, heat exchanger, distillation equipment, solvent recovery, and spray dryer supplier worldwide based in the USA. They have more than 25 years of experience in supplying processing equipment and providing services of equipment fabrication, installation and commissioning, retrofitting, personnel training, troubleshooting, and field services. Contact them today to fulfill your processing equipment requirements!