While there may not be a tie to Picasso, there is indeed both art and science involved in turning minced or ground meats into encased products. Whether the final form is a frankfurter, fresh or dried sausage, bratwurst, liverwurst, deli meat or other processed protein, the casing is arguably as important as the beef, pork lamb, veal or poultry stuffed inside it.

If a casing is too thin or contains any punctures, for instance, the product will not hold up during further processing, cooking or chilling. If it does not provide a proper barrier, problems can arise in texture, moisture level and safety. If the casing is too thick, consumers will find it unpalatable.

For upward of thousands of years — that’s how long people have been eating processed meats like sausages, according to food historians — casings were fashioned from the intestinal tract of animals and, to a lesser extent, from special type of fabrics, like muslin bags. Animal intestines were deemed both pliable and tensile, and processors enjoyed a regular supply.

These days, intestines from sheep, pigs and cattle are still used in fresh sausage and frankfurter casings. Many types of processors use animal-based materials, for a variety of taste and operational reasons. As food processing evolved in the past century, though, other types of materials have replaced animal casings.

“You have a whole range of casing choices now, from animal casings to cellulose to collagen,” reports Bob Rust, professor emeritus in the Department of Animal Science at Iowa State University.

To that end, there continue to be advances in casing technology, relating to material, size, color and flavor. Impermeable casings, for example, have been introduced in both uncoated and coated forms, while technologies have fueled the growth of products such as flat-sheet casings, cut and pre-tied forms and co-extrusion equipment, among others.

In turn, equipment used to apply casings in conjunction with other functions such as linking and hanging, allows for greater integration and higher-speed processing.

As more processors seek to diversify their offerings, many sausage and hot dog companies use different types of casings. Vienna Beef, Ltd., a Chicago-based manufacturer of hot dogs, sausages, deli meats and other specialty foods, offers products made from animal casings as well as those produced using synthetic casings.

“Probably 80 percent of our business is skinless, but some of the longstanding big restaurants and hot dog stands still use natural casing,” reports Tom McGlade, executive vice president.

Animal-based casings remain popular among a definable segment of consumers and offered by a number of processors including longstanding, multi-generationally owned companies and niche processors. The market for such products is based on several factors, from mouthfeel to heritage.

“I think tradition is one of the reasons,” says Herbert Ockerman, professor in the College of Food, Agriculture and Environmental Sciences at Ohio State University and an expert on casings. Old World-style manufacturers maintain time-tested techniques because their brand equity is built on them, he says, while newer specialty companies seeking to distinguish their products also put a premium products made with natural casings.

Sheer eating experience is not to be overlooked in the continued interest in processed meats cooked in animal casings.

“They have a bit more of a snap to them, and people sometimes prefer them,” Ockerman notes. McGlade drives home the point.

“The natural casing has a more authentic hot-dog stand look and a greater snap, especially if it’s grilled,” he notes, adding that such varieties are especially popular in Chicago and other parts of the Midwest. That said, while fans of animal-based casings savor the unique characteristics, some of those same features can pose challenges for processors.

“The natural casing is a plus and minus. It’s a plus because you get the Old World look and irregularity, but that tends to limit some compatibility with high-speed machines,” points out Rust. Adds Ockerman: “They are harder to use on an automated system, particularly if you are trying to pack to a given weight, since they are not quite as uniform.”

In addition, according to Ockerman, animal casings are more expensive than other alternatives, because of the labor involved in recovering and processing them for foodgrade use. Many pig and sheep casings are now sourced from China, and concerns about imports from that part of the world are leading to a greater scrutiny of production practices. McGlade says that Vienna has had to make various adjustments for natural casings.

“My way of describing stuffing a natural casing is like filling a water balloon. It’s very hand-done, but it has become more automated,” he says. A few years ago, Vienna invested in a more automated natural casing link machine.

To that end, equipment manufacturers recognizing the continued market for natural casings have developed new models of machinery built for such products. High-speed machines are available that allow natural casing product to be linked to exact sizes and weights, for instance.

Collagen casings represent another type of casing used for sausages, comprised of edible protein turned into an extrudable mass to form a tube. Technically, collagen casings are naturally derived, in that the substance often originates in cattle hides and is then processed with other ingredients to create a tubing.

Collagen casings are preferred by some manufacturers because they are strong, uniform and available in either edible or inedible form. According to Rust, collagen casings work particularly well with high-end sausage products, like dried and semi-dried sausages.

Cellulose casings, meantime, remain popular among hot dog, sausage and other manufacturers of skinless products. The inedible casings, removed before packaging, lend uniformity and a shiny appearance.

Although collagen and cellulose casings have been around for years, suppliers have continued to make improvements in the material and applications for both.

Cellulose casings, for example, increasingly are designed to lend a more natural appearance to finished products. Clear casings and those with a “veined” appearance allow a processor to create sausage and other products that resemble natural casings in color and look.

Plastic casings are often used for high-volume production of sausages, skinless franks and deli meats. Plastic casings offer the benefit of uniformity, speed and food safety, among other advantages. Special polyethylene casings have emerged in recent years, developed for their appearance and the fact that they can be printed easily with a brand or logo.

Within plastics, impermeable plastic casings are marketed based on their barrier properties, which protect a product from harmful bacteria during the cooking and chilling process. In recent years, suppliers have improved their ability to create coated versions of impermeable cook-in casings

In addition to impermeable versions, newer types of permeable plastic casings are available. Permeable plastic casings are touted for their ability to transfer flavor, including various smoke and spice flavors, and color during processing. Such casings offer the benefit of taste coupled with processors’ ongoing push to improve yield.

Rust says that while permeable casings can be costlier than impervious ones, they are in development because they allow for Old World characteristics yet meet modern demands for speed, quality and safety.

“Some of these permeable casings, like other manufactured casings, run well on automated machinery,” he remarks.

In addition to the plastic casings themselves, the systems on which they run are also more high-tech these days. At Vienna Beef, for example, McGlade says machinery has continued to improve.

“All of our skinless products are produced automatically — you put beef in one side, and it comes out the other,” he says.

Nylon film casings represent another type of synthetic casing for sausages and other products. Such shrinkable products are often used for rolls and sausages and are designed to improve yield, enhance meat “cling” and ship as case ready. Cloth casings, too, are still available and used for certain types of sausages, such as more upscale items.

In recent years, innovations in casings have come from new technologies such as co-extrusion, through which a machine simultaneously extrudes meat batter and a collagen or alginate gel that becomes the casing.

Co-extrusion technology cuts down on labor because it allows for continuous production and also imparts uniformity. The co-extrusion systems were first typically used for large-diameter products, but improvements in equipment have allowed for the production of smaller-diameter products, such as fresh sausages and even cocktail-size franks.

“The biggest applications to date for co-extruded casings have been on products that are difficult to handle in other ways, such as some snack stick type of products, cocktail and other small links and fresh links. And a lot of that is driven by cost,” observes Rust.

Rust also mentions the emergence of vegetable-based casings, such as alginate.

“There are also some others that are coming on the market, with a base of blends of alginate and other materials,” he reports. “In some cases, the opportunity to adapt to a vegetarian analog would be interesting, too.”

As for the future, Rust doesn’t count out natural casings anytime soon, even if they are more expensive.

“While we will see some changes in product development and cost, with everyone trying to get to lower product costs, that will open up a place for niche products. I think we can find everything from a hot dog at a ballpark to something that came out of a high-end deli,” he comments, adding that the art of producing artisan-style sausages and other processed meats lives in different ways, too, including hot new trends on the foodservice side. “There is also resurgence in charcuterie.”