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Sanitation Criteria for Historic or Living History
Demonstrations Producing Food or Food Products,
a National Park Service document, circa 1970.


The operator of a flour mill driven by water and steam, and not a mill providing demonstrations for the public.
The mill in Mora (vicinity), New Mexico.
1943 January, John Collier, 1913- photographer.
Library of Congress Prints & Photographs Division Washington, D. C.


In some National Park Service Areas, historic or living history projects are operated to demonstrate the type and kind of equipment used during this period of time. This type of equipment or machinery was not designed for quick disassembly and cannot be easily cleaned or sanitized.

1. Cane Crushing or Juicing Operations:

Note: Omitted for this presentation and format.

2. Flour or Grist Mills:

Historic mills were usually powered with a water wheel or water turbine to provide the energy needed for the grinding of the grain, operation of elevators, and related activities. Power from the water wheel or water turbine is usually transmitted through a series of gears or pulleys and belts to the various machines within the mill. The grinding process is usually accomplished by large stone wheels placed in a horizontal position. These stones grinding wheels usually are provided with grooves and are operated with very small tolerances between two wheels so that any grain which is introduced through the center hole of these wheels will be crushed or ground up as it passes between the narrow space between the stones. The ground grain is then transported by elevators, moving buckets, airlift, or conveyors to a series of screens where the husks and other unwanted portions of grain are separated. The separated, properly ground material is then transported to an area where it is placed in bags.


Many of these historic mills are still using the original buildings or reconstructed facilities which contain much of the old equipment used several hundred years ago. Many of these buildings have exposed roof beams, support columns, and cross beams, which accumulate dust, flour and grain particles. This type of construction makes it difficult to clean these buildings. Most of the equipment and machinery in these mills was not designed for quick disassembly nor can it be easily cleaned or fumigated. Grains which are to be ground, processed, and used for food should contain no foreign material (dirts, dust, sand, gravel, insects, rodent pellets, urine, hair) and contain no toxic chemicals such as mercury, arsenic, etc. If the grain is stored at the mill for a time before it is ground and processed into flour it should be stored in a suitable storage bin which is properly constructed to prevent contamination during this period. It should be protected from dust, moisture, insects and rodents.

In many of the old mills the grain handling equipment such as elevators, conveyors, storage bins, etc., are constructed of wood. Elevators are so constructed that they are not easily take apart for cleaning. This type of construction permits the accumulation of grain in corners, cracks, and crevices and provides a ready food supply for insects and rodents.

The existing equipment should be modified in such a manner that complete access to all portions of the grain storage and handling equipment is accessible for easy cleaning. This may be done by providing removable panels or hinged sections so that the equipment can be properly maintained. Cracks or open joints where two pieces of wood are jointed should be sealed with a suitable sealing compound such as silicon clean sealer.

Insect Infestation:

This is probable the most serious problem in grain mills. There are a number of insects which infest grain and will cause contamination of the grain or grain products. (See appendix #2, for brief description of insects and drawings.)

Insect infestation may be caused by bringing in the infestation with the new grain or new grain may be infested by storing in bins which contain small amounts of old infested grain. It is important therefore, to properly clean the mill before any grain operation is begun. Probably the most effective method of cleaning is with a suitable vacuum cleaner. A heavy duty low speed unit such as a Hoffman (5 horse power) or Tornado should be used. A portable air compressor with suitable hoses and nozzels cable of producing air at 100 psi should also be available.

To Control Infestation:

Note: The first paragraph is omitted because it advocated the use of various fumigates. The FDA and OSHA may no longer approve of these chemicals and substances. Good housekeeping goes a long way in controlling pests. Modern mills have climate control with is the ultimate in controlling pests. Museums are also big on climate control to preserve artifacts collections, but I have yet to see a restored mill that also has climate control. A restored mill is just as much of a museum and also contains a full assortment of artifacts so it should also go to say, that with the grain pest problem, they should also be climate controlled. T. R. Hazen

Disassembled machinery should be thoroughly cleaned with a vacuum cleaner to eliminate all traces of grain or grain products such as flour or corn meal. Storage bins should be no cracks or crevices in the corners where small amounts of grain may remain from one operation to the next. Particular attention should be paid to equipment such as elevators, and conveyors, which have cracks or crevices or blind pockets with might allow the accumulation of small quantities of grain or grain products. Failure to removed pockets of accumulation grain products will permit the propagation of insects and provide a source of food for rodents.

Processed grain such as flour or corn meal should be packaged and stored in a suitable storage area protected from contamination by dust, insects, and rodents. Packaged products should be properly labeled before they are sold, offered for sale, or given away. Only through diligent care, proper storage, adequate cleaning and fumigation of the entire facility can the control of insects and rodents be accomplished. The complete cleaning and fumigation procedure should be repeated on a cycle of at least every three weeks while the mill is in operation.

Rodents, Rats, and Mice: (See appendix #3 for description)

Rats and mice are often a difficult problem in grain mills were corn, wheat and other grains are stored, processed, and distributed. Adequate rodent stoppage control measures should be employed. All cracks and crevices, openings around pipes, ventilators, windows, etc., should be properly screened and closed to prevent entrance of rodents. Storage bins and storage areas where grain is stored should be adequately protected from the entrance of rodents. Tight fittings doors, manholes, hatchways and windows, may have to be lined with metal to prevent the gnawing of openings by rodents. Grains may be contaminated by rodents by their pellets, urine, and hairs. Incoming grain should be carefully examined before it is accepted to be sure that it is free of insect fragments and rodent contamination. After adequate rodent stoppage repairs are made it will be necessary to eliminate the rodents from the building. It is not advisable to use poisons around a grain mill so an adequate trapping program using spring traps is probable the best way to get rid of rodents within the mill.

Appendix #1: Drawing of Evaporation Pan.

Note: Omitted for this presentation and format.

Appendix #2: Stored Food Insects.

Stored Food Insects

There are many other insects than bother us by invading foods. Most of these are small moths or beetles which create problems of wasted food and nuisance rather than disease.

1. Types of Beetles and Moths:

A. Beetles and Moths Infesting Whole Grain.

THE RICE WEEVIL (Sitophilus oryza) world-wide in distribution, is probable the most important grain pest. This small, reddish-brown to black snout beetle, 1/8 to 1/6 inch long, has small, round pits on the thorax and two reddish or yellowish spots on each wind cover. The larva is short, fat, and whitish. The adult is a strong flier. The larva and pupa develop within a single grain of rice or kernel of corn, from which the adult weevil emerges about 30 days after the egg is laid. The adult female lives 4 to 5 months, depositing 300 to 400 eggs in small openings bored into grain. The rice weevil feeds upon corn, rice, wheat, barley, and other grains.

THE GRANARY WEEVIL (Sitophilus granarius) is similar to the rice weevil in appearance, but with oval pits on the thorax, and with the wing covers uniformity dark brown. This insect has become thoroughly domesticated, losing its power of flight and forsaking wild and cultivated grain fields for the grain store houses of man. This snout beetle is slightly larger than the rice weevil and lives from 7 to 8 months. Whereas the rice wheel is a major pest in the South, the granary wheel more often frequents the Northern States.

THE CADELLE (Tenebroides mauritanicus) is a black beetle 1/3 to 1/2 inch long, with the head and pronatum distinctly separated from the fore wings by a loose joint. The large, whitish, fleshy larvae are about 3/4 inch long when fully grown and may be recognized by their prominent black heads, the paired black spots on the three segments of the thorax, and two short dark hooks, at the posterior end of the abdomen. Larvae burrow into the woodwork of grain bins, and a seemingly clean bin may harbor thousands of larvae, pupae, and adults. The life cycle requires from 2 to 14 months, many adult living more than a year. The females lay about 1,00 eggs in protected situations, such as in cracks near food. The cadelle feeds upon grain and grain products and does much damage to bolting silk in flour mills. It is especially injurious in poorly sanitated mills.

THE LESSER GRAIN BORER (Rhyzopertha dominica) a brown or black, slender, cylindrical beetle with numerous elevations on the pronatum, is about 1/8 inch long and is most common in the Gulf States but may occur anywhere in the country. Both larvae and adults attack and destroy wheat kernels. The females lay up to 500 eggs each, dropping them in the loose grain. In warm weather the life cycle is completed in about 1 month.

THE ANGOUMOUS GRAIN MOTH (Sitotroga cerealella) is a light grayish-brown or straw-colored moth with a satiny luster and wing expanse of 1/2 inch to 2/3 inch. The hind wings are fringed with long, dark setae, and have a point at the lip like a finger, which distinguishes the insect from the clothes moth. The larva is white, with a brown head. It is only 1/5 inch long and lives within the individual grain of wheat, corn or other grain. The winter is passed in the larval stage in stored grain. The adult emerges and infests cereal crops either in the field or in storage, depositing about 40 eggs. The entire life cycle may be completed in 5 weeks. The Angoumois grain moth is second in importance to the rice and granary weevils as a pest of stored grain. It is of greatest importance in the South and in the soft red-winter-wheat region of the Eastern and Central States.

B. Beetles and Moths Infesting Broken Grain.

THE CONFUSED FLOUR BEETLE (Tribolium confusum) and the RED FLOUR BEETLE (Tribolium castaneum) are similar in appearance and habits. Adult confused flour beetles have the antennae gradually enlarged toward the tip, whereas the antennae of the red flour beetle have the last three segments abruptly enlarged. T. confused cannot fly, whereas, T. castancum may fly. The elongate, reddish-brown beetles are about 1/7 inch long, with a distinct joint between the thorax and abdomen. The adult female may live for as long as 2 years, depositing 300 to 400 eggs. The mature larva is brownish-white with six legs, and is up to 1/2 inch long. The life cycle requires 2 to 4 months when temperatures are favorable. These beetles are very important pest of flour, infesting many flour mills, warehouses, and grocery stores. They also feed upon grain, beans, dried fruits, nuts, chocolate, and other foods.

THE FLAT GRAIN BEETLE (Cryptoestes pusillus) is one of the smallest beetles found in stored grain, It is a tiny, reddish-brown about 1/16 inch long with antennae nearly as long as the insect. Is is usually found with other grain pests.

THE INDIAN MEAL MOTH (Plodia interpunctella) has a wing expanse of 1/2 to 3/4 inch, with the basal one-thirds, brown to copper. The females lay bout 200 eggs, and the tiny whitish, brown-headed larvae emerge in 2 - 14 days. The life cycle is 50-305 days. Full-grown larvae (1/3 to 1/2 inch long) produce silk which webs together flour, graham crackers, nuts, dried fruit, powdered milk and other foods.

C. Beetles Infesting Dried Peas and Beans.

THE BEAN WEEVIL (Acanthoscelides obtectus) is a short snout beetle that feeds upon stored beans and peas. The adult is 1/8 inch long with reddish legs and light olive-brown color, mottled with darker brown and gray. The body narrows evenly toward the head. The tiny, legless larvae and pupa live within the bean, whereas the adult emerges from the bean and feeds upon other materials. The female deposits eggs in beans, bother in the field and in storage, and six or seven generations may be completed in a year. As many as 28 weevils have been known to develop in 1 bean. The use of tight sacks has been found to afford considerable protection. Bean vines and other refuse should be burned in the field or plowed under to prevent propagation of this insect. The adults hibernate in fields and warehouses.

THE PEA WEEVIL (Bruchus pisorum) appears similar to the bean weevil, but is larger (1/5 inch long), brownish flecked with white, and with black to gray patches of scales. There is one generation per year, the adults over wintering is peas in the field or in storage. Egg deposition occurs only in the field. House mice eat pea weevils by cracking open the infested pea, eating the weevil, and discarding the pea.

D. Beetles and Flies Infesting Meats and Cheese.

THE LARDER BEETLE (Dermestes lardarius) is about 1/3 inch long, dark brown, with a wide yellow band across the front part of the wing cover. The larvae is brown, very hairy, tapering toward the ends of the body. This insect is world-wide in distribution. The eggs are laid on or near animal products such as feathers, horns, skins, hair, ham, bacon, dried beef, and like products. The life cycle requires 40 to 50 days. This insect may be found in dog biscuits, cheese, museum specimens, dried fish, and stored tobacco. It is also known to penetrate lead. Control consists chiefly of protection from attack, such as wrapping hams in paper and cloth immediately after smoking, and the use of cold storage lockers. Skins and hides are protected by dusting or spraying with 1 percent Lindane.

THE RED-LEGGED HAM BEETLE (Necrobia refupes) a shiny blue to green beetle 1/7 to 1/4 inch long with reddish legs, is especially troublesome in the Middle Atlantic States. The adults usually disperse by rapid running, but are able to fly. The mature larva is about 2/5 inch long, purplish, with six short legs, and tapered toward the head. The life cycle usually occupies 36 to 150 days. The female lays 400 to 1,00 eggs on exposed meat, indicating the need for prompt wrapping of hams immediately after smoking. The larva is able to perforate grease-soaked paper wrappings. This pest lives primarily on dead and decaying animal matter, but is sometimes reported in groceries and warehouses on smoked ham, bacon, garlic, bone meal, and other materials.

THE CHEESE MAGGOT or CHEESE SKIPPER (Piophila casei) is a fly about the size of a horse fly. The adult is black with bronze tints on the thorax, reddish-brown eyes, and iridescent wings which lie flat over the body. The larva is a slender maggot, pointed toward the head end. The larva is able to skip as much as 10 inches horizontally and 6 inches vertically, by curving its body into a ring, fastening its mouth hooks onto the end of the abdomen, suddenly releasing its hold, and throwing itself into the air.

The life cycle of the insect is completed in 12 days under favorable conditions. The adult deposits 140 to 500 eggs over a period of 3 to 4 days. This insect infests ham and cheeses. The adults can transmit enteric diseases to man by contamination, and the maggots cause intestinal irritation when ingested with cheese. Infestations of the cheese maggot should be prevented by screening (30-mesh) storage rooms and wrapping meat in paper and enclosing it in a tight cloth paraffin. The recognized common name "cheese skipper" is very unfortunate for this pest, because "skippers" are moth-like lepidopters.

E. Beetles that are Feeders on Stored Food.

THE SAW-TOOTHED GRAIN BEETLE (Oryzaephilus surinamensia) is an important pest know throughout most of the world. A closely related species, Oryzaephilus mercartor, is also important and is often mistaken for the saw-tooth grain beetle. The adult is a small active, brown beetle 1/10 inch long, with a flattened body and six saw-toothed projections on each side of the thorax. The larva is yellowish-white, less than 1/8 inch long with a brown head, and abdomen tapering toward the tip. The female lives for 6 to 10 months, depositing 45 to 285 eggs in foodstuffs. Several generations may occur each year, as the life cycle requires only 3 to 4 weeks during the summer. The saw-tooth grain beetle is an important pest in grocery stores, food warehouses, and grain storage. It readily penetrates packaged cereals, dried fruits, and candies. It also attacks flour, meal, sugar, drugs, dried meat, and tobacco.

THE CIGARETTE BEETLE (Lasioderma serricorne) is primarily a pest of tobacco, but will feed upon many other products as was evidenced by its presence in the tomb of Tutankhamen in Egypt. This small, oval, light brown beetle is 1/10 inch long with smooth wing covers. The head is retracted beneath the thorax. The adult beetle flies readily. The larva is yellowish-white, curved, very hairy, with a light brown head, and about 1/6 inch in length. The life cycle requires 6 to 12 weeks, and there may be five to six overlapping generations per year in warm localities, but only one generation in cooler areas. The female deposits as many as 100 eggs in tobacco, grain, milled cereals, and other products. This insect infest upholstered furniture, feeds, dried plants, drugs, black and red pepper, pyrethrum powder, raisins, rice, and many other commodities.

2. Control of Beetles and Moths in Stored Foods:

A. Good sanitation which includes frequent cleaning of shelves and floors. These pest can thrive on flour, meal and cereal products that are spilled and left on the floor.

B. Clean cool dry food storage, (cool temperatures inhibits growth and reduces egg laying.)

C. Examine all incoming stock for signs of infestation.

D. Isolate from the rest of stock any infested products until ready to dispose of.

E. Rotate stock using a code or numbering system.

F. All open packages or sacks should be either used immediately or stored in covered containers.

G. Foods should be stored a minimum of 6 to 8 inches off the floor. This increases speed and eases in which products can be handled with mechanical folk-lift trucks as well as allowing an open space for good ventilation, and when kept clean, discourages insect infestation. It also affords an area for inspection to pick up early infestations. It is recommended that aisles a minimum of 2 feet wide be provided along walls, through the center and elsewhere depending on the size of the storage area.

H. Use of insecticides may be necessary to prevent reinfestations. Remember, insecticides are poisonous if they get on food products the product is adulterated and may be harmful. The method of application of an insecticide as well as the type is critical. In the case of stored food insects treat only along baseboards, cracks, crevices and immediately under pallets, etc.


The following publications may serve as valuable additional references for identification of insects and as guides for organization and management of an insect control program:

"Pest of Stored Grain and Grain Products"
Richard T. Cotton
Burgess Publishing Company.

"How to Know the Insect"
H. E. Jacques
William C. Brown Company, Dubuque, Iowa.

"Destructive and Useful Insects"
C. L. Metcalf and W. P. Flint
McGraw-Hill Book Company, Inc.

"Stored Grain Pests"
(Farmers Bulletin Number 1260)
United States Department of Agriculture

"Scientific Guide to Pest Control Operations"
Lee C. Truman, Ph.D. and William L. Butts, M.Sc.
Pest Control Magazine, Cleveland, Ohio.

"Handbook of Pest Control"
Arnold Mallis
MacNair-Dorland Company
254 West 31st Street, New York 1, New York.

"Storage of Cereal Grains and Their Products"
Edited by J. A. Anderson and A. W. Alock
American Association of Cereal Chemists
St. Paul, Minnesota.

Appendix #3: Rodents.

Rodents Types:

The terms domestic rodent includes Norway rats, Roof rats, and House mice. These rodents are best characterized by having a single pair of incisor teeth on each jaw and by the absence of canine teeth. These incisors grow about 6 inches in length a year, which accounts for the rat's tendency to gnaw and chew to wear the teeth down. They can chew through plastic, wood, lead pipes and aluminum.

NORWAY RAT- is the most important rat and predominant rat in the United States, except for some coastal areas. The Norway rat being the larger and more aggressive will many times fight off and even kill the Roof rat. Common names for the Norway rate are Sewer rat, Wharf rat, Brown rat, House rate and Barn rat. The Norway rat is predominately a burrowing rat, and therefore it harbors in burrows in ground, around dumps, sewers, and buildings close to food and water. It will eat almost any food, but prefers garbage, meat, fish, and cereal. The range of travel is usually no more than 100-150 feet.

ROOF RAT- is the smaller rat but a very agile climber, in the United States it is found primarily in the south and pacific coast and in Hawaii. It generally harbors in the upper floors of buildings but occasionally is found in sewers. It prefers vegetables, fruits, cereal and grain for food supply. Its range of travel also is about 100-150 feet.

HOUSE MOUSE- is the smallest of the domestic rodents. It has the widest distribution of the three rodents throughout the United States. It is found primarily in and around buildings, nesting in walls, cabinets, furniture, and stored goods. It prefers food similar to the Roof rat such as cereal, grain, etc. The House mouse is a nibbler taking a bit here and a bite there. Range of travel 10-20 feet.

Recognition of Rodent Signs:

It is unusual to see rats or mice during the daytime as they are nocturnal by habit. IT is therefore necessary to interpret signs of their activities. From rodent signs one can determine the species or type of rodent, whether it is old or new and whether there is a light or heavy infestation.

DROPPINGS - the presence of rat or mouse feces is one of the best indications of an infestation. Fresh droppings are usually moist, soft and shiny while old droppings become dry and hard and have a dull grayish appearance and crumble when pressed with a stick. Norway rat droppings are largest, 1/2 to 3/4 inch long, and have bluntly rounded ends which give it a spindle-shaped appearance. Roof rat droppings are smaller (1/3 to 1/2 inch long) and more regular in form. The ends are usually quite blunt. House mouse droppings are very small (3/16 to 1/2 inch),. pointed at each end. American cockroach droppings are smaller than mice and have blunt, almost squared off ends.

RUNWAYS - rats occupy a limited area and use the same paths and odor trails that they are familiar with, as they are very cautious and suspicious. Outdoors in vegetation, such as grass, or weeds, you can see paths worn down which are between 2-3 inches wide. On earthen floors (outdoors) the runways appear as clean-swept, well packed earth paths.

RUBMARKS - rats prefer to follow closely to walls where their highly sensitive whiskers (vibrissae) and guard (body) hairs can keep in contact with side surfaces. By using their same rat runs their oily bodies, rubbing against a wall or baseboard, creates a rubmark. Rubmarks of the Roof rat are commonly seen overhead as swing marks, and are found beneath beams or rafters at the point where they connect to the walls. Fresh marks are soft and will smear when rubbed. Mice do not leave rubmarks that are detectable except when the infestation is heavy.

BURROWS - the Norway rat prefers to burrow for nesting and harborage while the Roof rat burrows only occasionally. Burrows are found in earth banks, hedgerows, along walls, under rubbish or concrete slabs, and near dog houses. Rat holes are about 3 inches in diameter while mice holes are only about 1 inch in diameter. IT a burrow is active it will be free of cobweb and dust. Fresh rubmarks on hard packed soil at the opening indicate a well established and active burrow. The presence of fresh fragments of food or freshly dug earth at burrow entrance also indicated an active burrow.

GNAWINGS - since the incisor teen of rats grow 4 to 6 inches a year they have do do some gnawing each day in order to keep their teeth short enough to use. Gnawing in wood are fresh if they are light colored and show distinct teeth marks. Small chips of wood or other material indicate recent gnawing. Old wood gnawings become dark and smooth.

TRACKS - may be observed anywhere along rat or mouse runs both indoors and outdoors. Tracks are more clearly seem by side illumination from a flashlight than by direct illumination from above. Dust in little use rooms and in mud around outdoor puddles are especially good places to look for tracks. Rat tracks may be 1 1/3 inches long. The rear paws of rats have 5 toes while the front paws have 4. Tail marks are also often visible in dust or tracking patches.

LIVE or DEAD RATS - positive proof of a rodent infestation is to see a live or dead rat or mouse. As a rule, only on very heavy infestations will you see a live rat. Dead animals may either indicate a current or past infestation.

MISCELLANEOUS SIGNS - urine stains can be seen with an ultraviolet light. The rat leaves a distinct pattern from that of mice. Rat and mouse hairs may be found along walls etc., and when examined under a microscope can be distinguished from hair of other animals.

Control of Rodents:


Get rid of all unwanted materials that might provide food or shelter. This means storing garbage and rubbish in approved type containers with tight fitting lids (plastic bags won't keep out rats). Lumber and other material s should be stacked 15 inches off the ground. Food set out for dogs, rabbits, pigeons or chickens is often a source of food for rats or mice and should be policed by picking up scraps of leftover food, and keeping dog dishes clean. Keep animal droppings cleaned up around dog pens.


Consists of changing structural details to eliminate any openings 1/2 inch or larger than would admit rats, and 1/4 inch or larger for mice. Where only Norway rates are found, usually only first floor stoppage work is economically feasible and then at the likely points of entry and not every possible opening i. e.: around doors, windows, where pipes and conduits enter buildings, floor drains, transoms, letter drops, fan openings, and foundations. Concrete, brick and mortar are well as galvanized hardware cloth, and galvanized metal are some materials needed for rat proofing. Where Roof rats are encountered, rat proofing must include wire, vertical pipes, and opening to upper floors and roofs.


Are useful around food establishments where rodenticides are not permitted or are hazardous, and where only slight infestations are predicted. Two main types of traps:

1. LIVE TRAPS (O Traps) used for catching live rats for study purposes.

2. KILLER TRAPS (Snap Traps).

3. A third type (Cage Trap) is used for collecting live rats or mice. Traps must be maintained by checking frequently, never less than every 24 hours.

Filling a sack with freshly-ground flour in Kenyon's johnnycake flour mill in Usquepaugh, Rhode Island.
1940 December, Jack Delano, photographer.
Library of Congress Prints & Photographs Division Washington, D. C.

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Copyright 2002 by T. R. Hazen