Avoiding Product Spoilage When in Storage

Choose Your Solution Wisely

By Colter Marcks, Donaldson Process Filtration
Adapted from contributed article in Food Quality & Safety, Nov., 2017

Many manufacturing processes require that product remain in a holding tank for a specified amount of time. The purpose of the tank may be temporary storage for packaging purposes or long-term storage where a reaction must occur before processing can continue. (An example of this would be fermentation.)

"Storage is an important step in product manufacturing and is only effective if spoilage of the product is avoided."

Three common-place methods for avoiding spoilage while the product is in storage are:

  1. Tank blanketing
  2. Sterile air box systems
  3. Sterile air tank venting 

All of these methods provide product storage solutions, but they are not all equally cost-effective. Let’s explore each. 

Tank Blanketing

When storing product in large tanks, many assume tank blanketing is the best course of action. Tank blanketing refers to the use of inert gases like Nitrogen to cover the product in order to avoid spoilage. When manufacturing products that can be combustible, the system must be closed off from the atmosphere because oxygen can facilitate an ignition. In addition, various products ranging from food products to pharmaceuticals require the absence of oxygen in order to avoid chemical reactions that could cause product to become stale or spoil. As a remedy, the nitrogen or other inert gas that fills the previously -open volume of the tank serves to maintain a stable, chemical balance. While tank-blanketing is reliable, it can be overkill in certain situations when an equally effective but more cost-effective solution is available. If nitrogen is produced on-site, a nitrogen generation system must be purchased for a high investment cost. If the initial investment cost is too high, bottles of nitrogen may be purchased and delivered to the facility instead. In many instances, as nitrogen flows into the holding tank, it must be filtered to ensure that it is pure and dry. Filter housings and elements would also need to be purchased in order to filter the nitrogen before it goes into the holding tank. Total cost for nitrogen blanketing can be tens of thousands of dollars.

Sterile Air Box System

A sterile air box system is a self-contained sterile air system that does not require airflow input from a compressor. It will protect the product from bacteria and dust while creating aseptic conditions favorable to aerobic fermentation. Depending on the factory’s needs, sterile air box systems are available as stationary and mobile systems. A sterile air box system is a full solution product and includes necessary blowers, pre- filtration, and sterile air filtration. Depending on the size of the application, sterile air box systems can cost upwards of $20,000.

See Donaldson's P-SLF Sterile Air Unit >>

Sterile Air Tank Vent

When oxidation is not a risk, a sterile air tank vent is as effective as tank blanketing and a sterile box system but much more cost-effective. It is placed at the top of the holding tank to allow air to freely flow into or out of the tank to compensate for changes in volume. A sterile grade filter element is placed within the tank vent housing in order to properly filter air as it enters the tank to ensure that no particulate or bacteria enter and contaminate the product. Sterile air tank vents are especially effective where there will be a high variability of inflow and outflow. The initial purchase of a sterile air tank vent requires only the tank vent housing and sterile grade air filter. Depending on requirements, tank vent costs vary but could be as little as one thousand dollars. Most sterile air tank vents are CIP compatible.

See Donaldson's P-BE Tank Vent >>

Fiscally-minded manufacturers would be well-served to consider all storage protection solutions prior to making their decision in order to avoid paying more for a solution than necessary.

For the full article, see Food Quality & Safety.

Colter Marcks is the Engineering Manager in Donaldson Company’s Process Filtration Division and an actively involved member of 3-A SSI and CAGI. He has extensive experience in technologies, applications, and regulations related to liquid filtration, culinary steam and sterile air production in the food and beverage industry.