Q: I work for a small vegetable processor and am trying to decide what the most cost-effective method for freezing our product might be.
A: Great question, and not as easy as you might think. You have two basic choices: mechanical freezing or cryogenic freezing of your product. Cryogenic freezing typically involves the use of liquid CO2 or liquid nitrogen. In your industry, it is important to quickly freeze products to maintain moisture and cell integrity. Both technologies can achieve this, but at different costs.
You can use an ammonia system to power either a blast freezer, spiral freezer or tunnel. You can also use cryogens with similar pieces of equipment.
If you install an ammonia system, the capital costs at start-up are 6-10 times higher than with cryogenic. The reasons are the need for compressors, piping, condensers, cooling towers, electrical utility costs, maintenance, PSM compliance and possibly additional real estate to house the equipment.
Cryogenic systems are much more economical from a "first cost" standpoint, but the consumables (gas) are quite expensive. Typically, less maintenance is required on a cryogenic system than an ammonia system, but the lifecycle cost is higher.
New technologies are emerging for the more adventurous that incorporate ammonia, wind velocity and motion. They may be worth investigating, though mainstream applications reside in the future.
As a small processor, it makes more sense to start out with a cryogenic solution until you feel comfortable that your usage will be sustainable. As production volume grows and more resources become available, a later leap into mechanical freezing makes great sense.
This article originally appeared in the June 2013 issue of Food Processing Magazine.