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Liquid storage is an important unit operation in food processing.

Liquid Storage

What is Liquid Storage?

Liquid storage is an important unit operation in food processing. It encompasses storing liquid ingredients in safety vessels to protect them from microbial deterioration, dust particles and insects. Designing proper storage facilities should take into consideration factors such as the type of liquid to be stored and its susceptibility to microbial contamination.1

Commonly used liquid storage units include vertical containers or tanks made up of safe materials. In baked goods production, typical liquid storage ingredients include:1

  • Dairy products
  • Sugar and syrups
  • Oils
  • Flavors & liquid yeasts

How does it work?

Equipment used in storing liquid ingredients such as vats, vessels and tanks and fittings must comply with food safety regulations. Typically, they must be made of epoxy or stainless steel such as 3-A.1

Critical factors to be considered for liquid storage equipment include:2

  • Product to be stored
  • Handling of the product and its physical characteristics
  • Environmental conditions
  • Construction material:
    • Pipelines must be rigidly supported
    • Pipelines strainers and magnets must be used on the suction side of the pump
  • Hygienic conditions:
    • Self-draining installation of pipe systems without sags where the product could accumulate
    • Clean-in-Place systems must have weld fittings

Liquid storage parameters

Several parameters are involved in designing liquid storage equipment, such as:1

  • Nature of the food product: solution, dispersion, etc.
  • Density of liquid product: to help determine accurate tank volume
  • Temperature: must be set appropriately to avoid fluctuations in density and viscosity of the food product, as well preserve its overall quality
  • Environment: humidity, access to production area, etc.

Types of liquid storage equipments

Following is a summary of liquid storage equipment and their characteristics:2

Equipment Usage Advantages Disadvantages
Vats/vessels Small quantities of liquid or highly viscous foods
  • Economical storage of small quantities
  • Flexibility
  • Mobile units are possible
  • Better use of factory space
  • Reduced risk of quality damages
  • Expensive maintenance
  • More skilled personnel required
  • More space is required when working with large quantities
Tanks Liquid foods
  • Long term storage
  • Full automation of filling
  • Less skilled labor required
  • Good protection of product
  • Simultaneous filling and emptying possible
  • Good utilization of factory space
  • Expensive when built with  stainless steel
  • Susceptible to external damage
  • Requires more space

Application

Essential storage requirements for liquid ingredients in bakery operations:1,3

Food Product Temperature Equipment Considerations Consequences of Inappropriate Storage
Milk and milk products Maximum allowed temperature 7 °C (45 °F)

Refrigeration temperatura 1-3 °C (34-38 °F)
  • Stainless steel
  • Vertical tanks, bottoms must be sloped ¾ in/ft for small tanks and 1 in /ft for large tanks
  • Horizontal tanks, must have a pitch of ⅛ in/ft.
  • Bacteria multiplication and  off- flavors development.
  • Highest  microbial risk of all ingredients.
Sugar and syrups High moisture syrup must be refrigerated at 4°C (40°F)
  • Stainless steel, mild steel or fiberglass
 Not affected by bacteria, but may support mold and yeast growth
Eggs and egg products Below 4°C (40°F)
  • Stainless steel
  • Vertical tanks, bottoms must be sloped ¾ in (ft) for small tanks and 1 in /ft for large tanks
  • Horizontal tanks, must have a pitch of ⅛ in (ft).
 They pose the highest  microbial risk of all ingredients.
Oils Room temperature or cool storage
  • Stainless steel or mild steel
  • Avoid contact with light
  • Avoid contact with air that may oxidize the oil
 They may develop off flavors due to  oxidative rancidity and absorption of odors.

References

  1. Heldman, D. R and Lund, D.B. Handbook of food engineering. 2nd ed., CRC press, 2006, pp. 354-358.
  2. Saravacos, G. D. and Kostaropoulos, A.E.. Handbook of food processing equipment. 1st ed., Kluwer Academic/Plenum, 2002.
  3. Figoni, P. How Baking Works: Exploring The Fundamentals Of Baking Science. 2 nd ed., John Wiley & Sons, Inc., 2008.

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