Hygienic Design of Bakery Equipment

1. Materials of construction
   1. Stainless steel
   2. Polymeric materials
   3. Elastomers
   4. Adhesives
   5. Lubricants
   6. Thermal insulation materials
2. Functional requirements
   1. Cleanability and decontamination
   2. Prevention of entry and growth of microorganisms
   3. Compatibility with functional and operating requirements
   4. Validation of the hygienic design of equipment
3. Hygienic design and construction
   1. Surfaces and geometry
   2. Surface finish/roughness
   3. Drainability and layout
   4. Installation
   5. Welding
   6. Supports
   7. Insulation
   8. Testing hygienic characteristics (e.g., cleanability)

Relevance

The fundamental objective of hygienic design is the prevention of contamination or adulteration of the baked goods. Contamination can come from raw materials (introduced into the processing environment), but the products can also be contaminated by the processing and packaging environment inside the plant.

As an example, if a piece of equipment has an inadequately hygienic design, it will be difficult to inspect, maintain, clean, and/or sanitize. The residues (e.g., dirt, soil, and debris) can be retained in the cracks, crevices, and dead spaces of it and allow microorganisms it harbors to survive and multiply. These biological hazards may then cross-contaminate subsequent batches of product.¹

Bakeries need to properly incorporate hygienic considerations into the traditional technical requirements set in the initial stages of the design or purchase phase of equipment. Although it is not always easy and practical to follow this approach, the search for a comprehensive or “harmonic” set of requirements is necessary to avoid any endangerment of food safety. The long-term benefits of doing so are not only product safety, but also the potential to increase equipment life expectancy, reduce maintenance and, consequently, reduce operating costs.²

This way, bakeries can reconcile and/or balance technical, operating, and budget requirements with hygienic expectations when acquiring new processing equipment or designing lines. Considerations include:

1. Throughput (installed capacity)
2. Size (relevant to use of floor space)
3. Possibility of proper linkage/synchronization with the existing stages/flows within the production line
4. Energy consumption (electricity, gas fuel, or a combination of these)
5. Maintenance requirements and costs
6. Automation level (degree of control and interaction between machine and operator)
7. Price (cost of equipment plus commissioning and other charges)
8. Hygienic design

Application

The strategy for designing, constructing and installing hygienic equipment/machinery requires the following considerations:

1. The intended use of the equipment (delimitation of usage in terms of products and processes)
2. Identification of food safety hazards (chemical, biological and physical) associated with the food products that will be processed/handled in the machine
3. Characteristics of the products that will be processed/handled in the machine (e.g., physical state, moisture content, acidity, microbiological and physicochemical stability, sensitivity of components).
4. Risk assessment associated with each hazard.
5. Methods and measures regarding equipment design which can eliminate/reduce risks associated with these hazards
6. Further processing that will take place (subsequent processing equipment that could eliminate/prevent a given food safety hazard, e.g., washing, baking, pasteurization, metal detection)
7. Application of the product and/or the expected consumers of the product (e.g., immunosuppressed patients, infants, children, adults, elderly)
8. Cleaning and maintenance activities and conditions that will be applied to the machine³

Once food safety risks have been identified, the design and construction should take these into account. Personnel and environmental safety risks should also be assessed as these may influence the final hygienic design of machinery/equipment.

It is important to apply the eight considerations mentioned above when designing, constructing and installing machinery/equipment meant for baking applications. Baking plants have unique conditions regarding food processing equipment. These often have a combination of batch- and continuous-mode stages, with open and closed equipment within the production line; usually handling low-moisture (i.e., low water-activity) products such as crackers, biscuits, wafers, and high-moisture (i.e., high water-activity) products such as bread, rolls, dough/work-in-progress).

Closed and open equipment in the baking industry

In the practice, its is easier if the machinery/equipment is classified as open or closed equipment. This way, the design, construction, installation, cleaning, maintenance, and food safety conditions can be better planned and managed:

Open equipment

Open equipment is that which cannot be cleaned in place (CIP), and in which the products being processed or handled are not fully enclosed (i.e., isolated from the plant environment) by a continuous wall (e.g., piping, vacuum cavities, tubing, barrels).

Open equipment often requires:

1. Cleaning out of place (COP)
2. Manual cleaning
3. Immersion cleaning

Open equipment must be manually dismantled for cleaning. Such tasks can be performed with open plant cleaning (OPC) techniques, like foam cleaning and rinsing with medium-pressure systems (e.g., up to 40 bar). Dismantled machine parts can be cleaned in COP baths. The time required will depend mostly on validation of microbiological monitoring results. The time will vary depending on the available cleaning equipment and utensils.⁴

Closed Equipment

Equipment designed and constructed with its components fitted together tightly with no openings whatsoever to permit the entry of external agents (i.e., soil, human contact), and there is no possibility for accessing/touching the products held or contained by direct contact without prior dismantling.

In contrast to open equipment, closed equipment usually processes, handles, and conveys liquid and semi-solid products (e.g., process water, cleaning solutions, low-viscosity syrups, dough in bulk).

Closed equipment must be cleaned in place (CIP)  due to its access restrictions and typically confined spaces.

CIP includes the following general procedures or considerations:⁵

1. Pre-washing (rinsing with water)
2. Alkaline clean
3. Rinse
4. Acid clean
5. Rinse
6. Disinfection
7. Final rinse

Bakeries make use of open and closed equipment to process a wide variety of liquid, semi-solid, and solid products. This situation is rather uncommon elsewhere in the food industry since the products usually do not radically change regarding their physical state. Baking plants are special processing environments in which chemical reactions and physical transitions take place within the production line. All these conditions must be considered when designing, constructing and/or buying equipment.

Open and closed equipment of a baking plant