PROTECTING BAGGED FOODS FROM INSECT DAMAGE

From a pest insect’s perspective, processed foods provide a readily available and highly concentrated food resource: energy reserves for mate-seeking adults and growth nutrients for developing young. Everything from bagged flour to canned dog food is subject to insect infestation within the food manufacturing facility, distribution warehouse and retail outlet or in the restaurant or consumer’s home. One of the primary functions of food packaging is to protect the material until it reaches the consumer’s table. However, poorly engineered packaging, as well as improper storage and handling, can lead to insect infestation of grain-based foods and raw ingredients stored in bags or cartons (soft-pack items including flour, meat and bone meal, pet foods, dried fruits, cereals, cake mix, pasta, spices, snack foods, etc.).

WHAT HAPPENS IF I EAT A FLOUR BEETLE? A question commonly asked about stored product pests (SPPs) is, "Will it make me sick if I eat it?" The answer "maybe yes" or "maybe no" is not reassuring to most consumers and pest management professionals. The Food and Drug Administration has developed a regulatory standard referred to as Defect Action Levels (DAL).

The DAL lists the acceptable number of insect parts for foods processed from raw agricultural commodities (i.e., flour derived from wheat) and inadvertently contributes to this misunderstanding about the safety of insects in stored foods. After all, by establishing such action thresholds (no- effect levels) the DAL implies that ingesting minute quantities of specific non-living insect fragments poses virtually no health risk to consumers, even though there may be little research to support this assumption. The DAL (a work in progress) is periodically reviewed and adjusted to reflect advances made since its last publication. Regardless of the DAL, large numbers of living SPPs infesting raw materials or in finished products cannot be tolerated for several reasons:

• Processing, packaging or storing foods under conditions whereby they may become infested with insects is a violation of the Food, Drug and Cosmetic Act.

• Insects are mobile and may infest a clean facility or cross-contaminate unaffected goods held near the infested product.

• Larval cast skins and moth scales can induce non-life-threatening allergic reactions in humans. (In some situations, however, these allergens may be life-threatening to high-risk groups such as the elderly, infants and immuno-depressed individuals.)

• Insects can vector yeasts, molds and bacteria that cause spoilage, rancidity, bitterness and lower the shelf life in raw materials and finished products. Likewise, insect metabolic processes (creation of waste products, carbon dioxide, etc.) can alter the ecology of the product, leading to secondary infestations by microbes, mites and nematodes. The presence of some of these organisms may hasten spoilage or cause allergic or life-threatening conditions to consumers.

• Stored product pests are an aesthetic defect; customer rejections directly affect the profit margin.

MY FAULT OR YOURS? Another often-asked question is, "Did the insect go into the package or did it emerge from the package?" Often hidden within this query is the more pointed question: "Where did the infestation occur and who is financially responsible?" The answer involves much detective work that includes:

• Species identification and package damage evaluation;

• Disclosure of the history of the product (i.e., when and where was it manufactured and how was it packaged, handled and stored after it was made);

• Knowledge of the product itself (how was it processed and what are the insect-sensitive ingredients); and,

• Documented records of pest activity at each step in the manufacture/retail chain of custody.

It is widely accepted that insects rarely survive most food processing events, especially those involving high heat and/or low moisture. Extrusion, baking, drying, etc., are lethal to all stages of insect development; these are often referred to as "kill steps." However, product infestation can occur at the processing plant, especially in finished product-holding bins, various conveyors and bucket elevators, packaging machines or other similar post-kill step locations in the plant.

These risks notwithstanding, insect infestations in soft-pack items usually occur after the product is manufactured, packaged and shipped. Every time a soft-pack food item is moved, it risks damage from broken boards or popped nails in the pallet, forklift puncture or abrasion against other pallets or the walls inside the shipping vessel (rail car or trailer). Package damage also provides easy access for invading insects.

For example, adult merchant grain beetles can enter an opening (puncture, tear, loose glue flap, etc.) slightly less than 1 mm, while adult flour beetles can enter an opening a little larger than 1.3 mm. Early instar larvae can enter openings much smaller than these! In addition to packaging faults and physical damage, crowded storage conditions in warehouses and retail facilities (little room for sanitation, inspection and pest control) further contribute to post-manufacturing insect infestation in soft pack foods.

INVADERS AND PENETRATORS. One important aspect of the food processor’s product safety program is to develop packaging strategies that minimize insect contamination. Insects can infest packaged foods by chewing their way through the package wall (package penetrators) or by taking advantage of natural openings or damage to the package wall (package invaders). Obviously, only insects with chewing mouthparts are able to chew their way through (penetrate) a package wall; this excludes insects like adult flies (sponging mouthparts), fly larvae (a single mouth hook designed to feed on semi-liquid foods) and adult moths (siphoning mouthparts designed to imbibe liquids).

While paper, foil and thin plastic packaging materials may be susceptible to penetration by insects with chewing mouthparts, not all SPPs bearing recognizable mandibles are considered package penetrators, since these structures must meet specific criteria. Several SPPs (cigarette and drugstore beetles, weevils, grain borers and Indian meal moth larvae, just to name a few) have evolved short, stout mandibles for chewing through seed coats and are able to chew their way into and out of many packaging materials. (After all, the cigarette and drugstore beetles belong to the family Anobiidae, which includes many wood-boring beetles. The lesser grain borer belongs to the family Bostrichidae, which includes lead cable and bamboo borers.)

Other SPPs (flour beetles, flat grain beetles and saw-toothed grain beetles) have evolved mouthparts with long, fragile tooth-like projections, which are designed to feed on softer materials (i.e., flour or broken seeds). These "bran bugs" are poor package penetrators since they do not have adequate mouthparts to chew through wood, seed coats and other durable materials, such as food packaging. These poor penetrating insects are, however, good package invaders due to their small size, flat bodies and mobile habits, which allow them to access packaged foods via punctures or tears in the package wall or beneath loose seals and seams. Thus, bran bugs are poor penetrators, but good invaders and any food manufacturer that provides a grain-based or other insect-sensitive product in an easily damaged or poorly sealed package can expect infestation by both invaders and penetrators.

THE MASTER PLAN. Frequently, insect-sensitive, soft-pack foods are stacked on wood pallets, crammed into shipping vessels, jostled down the highway or rail line, off loaded into a crowded warehouse and allowed to sit for weeks or months prior to use or consumption. Even in a clean, well-managed intermediate facility, damage and insect risk increase when the material is once again loaded up and transported to the retail outlet. Some of the operational procedures that PCOs should encourage their customers to implement include:

1. Use only sound, clean pallets. Broken boards and exposed nails readily penetrate soft pack goods, causing insect- attracting spills or creating openings large enough for insects to enter. Such damage can occur even when slipsheets are used on wood pallets. Also, only cured pallets should be used. One product recall due to psocids was traced back to pallets made from green (new and moist) pallets.
2. Do not overload or haphazardly load trailers. Sharp pallet corners can damage packages during loading and products can rub against one another or walls of the vessel while in transit. Inflatable bladders and cardboard or wooden dunnage barriers can secure loads and prevent self-damage during shipping.
3. Shipping trailers must protect the product. Insect-supporting debris on the floor and behind wall panels, as well as damaged walls and floors (through which insects can invade), pose a high product risk. Loose screws, rivets and torn floors and walls (wood splinters or gouged metal) can damage packaging materials.
4. Randomly inspect incoming goods before they are accepted — pay particular attention to high-risk materials. Look for insects or signs of their activity (bore holes, webbing, frass, cast skins, trails, etc.) in corners, beneath flaps, under stretch wrap, on the pallet and beneath edges of the slip sheet, as well as in the empty trailer itself. This inspection must be conducted by trained individuals using flashlights. Most warehouses prefer to off-load product in a staging area until the entire load and empty trailer are cleared. In that way, suspicious product does not have to be retrieved from the racks where cross contamination or facility infestation may have already occurred. Finally, information about pest activity must be recorded on an inspection log.
5. Use good storage practices that promote sanitation, inspection and pest control and do not co-mingle products. High-risk products in poorly constructed packaging (sewn bags, loose flaps, porous bags that sift, etc.) or products with a history of insect problems should be semi-isolated so they can be inspected frequently. Keep these items on lower shelves and away from dark corners at the far end of the warehouse. Other storage practices such as first-in-first-out, maintaining clear aisles and perimeter accessibility, and sweeping up spillage beneath pallets and on storage racks when stock is removed will greatly minimize resident insect activity.
6. Spills must be addressed immediately and include a two-step process: a) seal the opening to prevent further spillage and keep insects out; and b) remove spillage from floor, rack, slip sheets, etc., that could serve as an insect resource.
7. Monitor insect activity in the facility using mechanical devices and a keen eye. Properly placed pheromone traps, glue boards and insect light traps can survey insect activity continuously without interruption. Be aware, however, that these are monitoring tools only; they are not controls. A trained individual must use the information gathered from traps to point him and his flashlight in the right direction. While traps should be monitored weekly and action taken when necessary, thorough inspections for SPPs in the plant/warehouse must be completed no less than once per month.
8. Before any pesticide applications are undertaken, identify the pest, estimate the population size and location and assess damage potential. Fogging or fumigation are not justified if sanitation or simply disposing of infested product can solve the problem. Likewise, pesticide applications cannot replace pest prevention programs that include inspection and monitoring, sanitation and proper storage practices.

The author is an entomologist and president of Technical Directions, Decatur, Ala. He can be reached at mholcomb@pctonline.com.