For sanitary construction and design of food equipment, it is important to know the general aspects. Designing of processing equipment is not to just focus on the containment of the material, the strength of the components, the efficiency of the operation, and the transfer of energy. It should also comply with strict standards and regulations, which are necessary for securing the quality and safety of the food products then it can be of importance.
The surfaces of food equipment are subdivided into two categories i.e., food product contact surfaces, where direct contact of food residue or chances that it can drip, drain, diffuse or be drawn. And non-product contact surfaces are those part of equipment that do not come in direct contact with food like legs, supports etc
Food Product Contact Surfaces
In terms of sanitary design, all food contact surfaces should be smooth, impervious, free of cracks and crevices, nonporous, nonabsorbent, non-contaminating, nonreactive, corrosion resistant, durable and maintenance free. If any modification or process is used in fabrication (e.g., welded, bonded, or soldered) it should be done using appropriate materials and in a manner that ensures the final surface meets the sanitary design criteria.
- Materials: A variety of materials are used in the construction and fabrication for different applications in food equipment. These materials vary in their properties with regard to workability, compatibility, and sanitary design features.
Metals: Stainless steel is the preferred metal for food contact surfaces because of its corrosion resistance and durability in most food applications. Titanium has excellent durability and corrosion resistance (especially in an acidic environment), however, its use is limited by high cost. Titanium is used in stainless steel alloys for food equipment used in the processing of food products with high acid and/or salt content (e.g., citrus juice, tomato products). Copper is primarily used for equipment used in the brewing industry, with some use for cheese vats in Swiss cheese manufacture, due to tradition but should be avoided from acid processing as chances of copper leaching into product is there. Aluminum is used in certain parts and components where lighter weight is desired. However, aluminum has poor corrosion resistance and can become pitted and cracked with continued use. Carbonized metal and cast iron are only used for frying and cooking surfaces, and similar applications in food service. Galvanized iron should be avoided as a food contact surface because it is highly reactive with acids.
Non-Metals: Plastics, rubber, and rubber-like materials that should be food grade if they are coming in contact of food. Ceramics are used primarily in membrane filtration systems. Glass may be used as a food contact surface but it needs to be assured that it is durable, break resistant or heat resistant glass.
- Surface Texture and/or Finish: If any surface is grinded, polished, or textured in any way, it must be checked for final surface to be smooth, durable, free of cracks and crevices. The surface texture or finish of a material is decided by Ra Value (Roughness Value) which is determined using a sensitive instrument (termed a profilometer) which employs a diamond tipped stylus to measure peaks and valleys in a relatively smooth surface.
- Construction and Fabrication: Food equipment should be designed and fabricated in such a way that all food contact surfaces are free of sharp corners and crevices. All mating surfaces must also be continuous (e.g., substantially flush). Construction of all food handling or processing equipment should allow for easy disassembly for cleaning and inspection. Where appropriate (e.g., vessels, chambers, tanks), equipment should be self-draining and pitched to a drainable port with no potential hold up of food materials or solutions. Piping systems not designed for routine disassembly must be sloped to drain.
Internal angles should be coved or rounded with defined radii. Equipment standards specify appropriate radii for specific equipment applications and components. Permanent joints should be smooth, durable, and should meet all sanitary design criteria. Equipment standards generally require that welded joints on stainless steel surfaces be continuous, butt-type joints and ground smooth. Care should be taken when connecting pipes, gauges, thermometers, probes, or other equipment to food contact surfaces. It is necessary to ensure the connection does not create a dead end or an area where food product can accumulate and is not accessible to cleaning solutions. Shafts, bearings, agitators, and other attachments or ancillary components should be attached to food equipment in such a way that the food contact zone is sealed from contamination caused by leakage of lubricants or other contaminants into the product zone. Such components should be accessible and removable for cleaning. Any opening or cover should be designed, fabricated, and constructed in such a manner as to adequately protect food products from contamination and to divert potential contamination away from the food product zone. Openings should be lipped and covered with a shoe box type design and the top rims of equipment should be constructed and fabricated to avoid the collection of water droplets or dust.
Nonfood contact surfaces
Non-product contact surfaces of food equipment are a source for environmental contamination of a food facility with pathogens. These areas can also be harborage areas for insects and rodents. Therefore, care should be used in evaluating these surfaces of equipment with regard to sanitary construction and design. Non-product surfaces of equipment should be constructed with appropriate materials and fabricated in such a manner as to be reasonably cleanable, corrosion resistant, and maintenance free. Tubular steel equipment framework should be entirely sealed and not penetrated (e.g., bolts, studs), to avoid creating niches for microorganisms. Whenever practicable, attachments should be welded to the surface of the tubing and not attached via drilled and tapped holes.
With continuous improvement in equipment design, there is evident improvement with the sanitation, cleaning and food safety programs. Equipment designing should always incorporate the inputs and should consider the requirement of processor for coming up with design that can provide required output.