U.S. ARMY FOOD R&D PROGRAM

 

HERBERT A. HOLLENDER

 

U.S. Army Natick laboratories

[151] The food technology aspects of military rations and space foods and the problems associated with their development have been covered in numerous publications (refs. 1 to 6).

Proper design criteria are required for any feeding system or subsystem. For military field rations these are:

(1) Acceptability: liked by majority of troops

(2) Stability: 6 months at 100° F

(3) Nutritional adequacy: calories and essential nutrients

(4) Utility: meets specific serving requirements With the use of these criteria, a food product or feeding system can be developed or modified to meet any mayor operational situation. The same criteria can also be applied to a system for feeding in space.

A product which has outstanding military utility in the field still must address the supply and delivery systems Involved. These criteria, when properly defined and applied, force the development of a product or a ration that is integrated with the system. For example, they preclude perishable foods in a ration which has to be carried by the soldier and wherein resupply is not feasible for several days. Obviously, utility and stability have not been correctly addressed if ice cream were proposed for such a situation. A product or combination of products is required which is light in weight, easily prepared or requires no preparation, nutritionally adequate, and stable enough to meet the requirements of the long military supply line. All new products and ration prototypes must undergo intensive evaluation against these criteria. This includes testing against the specific technical requirements which have been established through translation of the military requirements.

Some 12 to 15 years ago, after the needs for new field rations that would meet changing battlefield tactics were analyzed, freeze-drying was chosen as the method of food preservation which had the potential of providing products and rations that would best fulfill the maximum number of criteria.

Up to that time the freeze-drying of food had been largely a laboratory curiosity. However, work in our laboratories and in closely related research groups demonstrated that it could be a practical method of preservation. Today, freeze-drying is being used both for military and civilian products. Admittedly, the high cost of processing is still a disadvantage, and a product selected [152] for this method of preservation must show an advantage in some characteristics such as flavor, stability without refrigeration, convenience, or light weight before the product can be successfully marketed to either a military or civilian customer.

The Army Food R&D Program has developed or modified and introduced into the military supply system more than 45 new items. Many of these are freeze-dried and range from peas to shrimp. They are used in garrison meals as well as in the combat area.

In addition to these 45 components complete rations are under development. One which has been completed but is not yet in the supply system is the quick-serve meal. All of 21 meals developed are precooked and are ready to eat after the addition of hot or cold water. From the technology which evolved through the development of these meals came the first-generation Food Packet, Long Range Patrol. This was the first freeze-dried ration actually to be used. Each packet contained an entree item such as chili, beef stew, or chicken and rice. Eight different entrees were available. The first-generation packets were well received, but required approximately 20 minutes to rehydrate in hot water and much longer when the water was unheated.

When the first requirements for foods for space were received by the Army, this background of freeze-drying technology was available for immediate application. However, if freeze-dried products were to be used, reconstitution by means of cabin-temperature water was limited to no more than 10 minutes. New technology had to be developed to meet these requirements. Without the background of experience from the Army program, a much longer leadtime would have been required to provide the 26 items which have been developed. (This illustrates what we have experienced many times in R&D work; that is, when you build an inventory of research and development information and experience, you never know in what direction or when it may be applied.)

However, the story does not end here. From combat patrol experience in the Jungles and rice paddies of Vietnam, it was found that 20 minutes was frequently longer than could be allowed for preparation of the long-range-patrol food packet while on patrol missions. The need was recognized to shorten the rehydration time in hot and cold water, and, if possible, to make the products acceptable when consumed without rehydration, that is, suitable for eating out of hand like popcorn.

Using the technology developed for space foods, the products were reengineered, they were tested in pilot-plant production, and a suitable procurement document was written in less than 3 months. Unlike most combat rations, these new "LURPs, " as they are known in Vietnam, receive fan mail. Many letters have been received saying that they are excellent and requesting information as to how they can be obtained for future use or for sending home so that Mom and Dad can see how good they are. Procurement of these packets currently runs around 10 to 12 million per year. Considering the small number of troops (less than 10 percent in Vietnam) that are actually being subsisted on combat rations, this indicates a very high usage rate. Needless to say, the eight entrees (pork with escalloped potatoes, beef stew, beef hash, beef with rice, chicken stew, chicken with rice, spaghetti with meat sauce, and chili) of the long-range-patrol food packet could not have been completely reengineered in the time frame indicated without the use of the [153] technology developed for space foods. These products rehydrate in 5 minutes or less with hot or cold water and may be eaten out of hand (fig. 1).

The technology of flex canning is being developed to reduce package weight by eliminating the use of metal cans for heat-processed items such as meats, vegetables, fruits, and baked goods in individual serving sizes. The packaging materials and the process have been described by Rubinate and Szczeblowski (refs. 7 and 8). The pouch material now used is a 3-ply laminate consisting of 0. 0005-inch polyester, 0.00035-inch aluminum foil, and 0.003-inch modified polyolefin as the food contactant. The special polyolefin will withstand a retort temperature of 250° F. The process is normally carried out in a retort using steam-air or water-air mixtures with sufficient time at the above temperature to provide for thermostabilizing of the product. Carefully controlled balancing air pressure is used to prevent bursting of the pouch during processing. A wide variety of products (fig. 2) and processes for them have been developed.

The texture and flavor of the cake and bread products have been difficult to control because of a tendency of these products to compress when thermally processed in the sealed pouch. To date we do not have a fully acceptable breadlike product although some cake items ranging from satisfactory to excellent have been developed (fig. 3).

The availability of technology for moist products in flexible packages from the Army ration development program made it possible to provide turkey and gravy as a Christmas dinner entree for the flight of Apollo 8. The product was consumed from the pouch with a spoon. A few months before the flight, the U. S. Air Force, in a series of parabolic flights, determined that spoon eating in weightlessness was feasible. This turkey and gravy product (fig. 4) was developed, processed, and safety-tested at the U. S. Army Natick Laboratories in approximately 5 weeks following the decision to use it. This quick response would not have been possible without the technology which was at hand from the military ration program. Additional products have been developed especially for space feeding purposes and were used on Apollo 9. Others are planned for subsequent flights (figs. 5 and 6).

As was mentioned earlier, the development of rations for field use requires constant concern for the logistics involved. If the food is to be carried on the soldier's person, both weight and volume become extremely important. In 1963 a series of contracts supporting an extensive effort on the subject of compression or compaction were initiated. A number of contracts were awarded to provide the background of research upon which to build a technology for advancing the state -of the art. On the whole these contracts were successful, although because of a reduction in funds the data developed were insufficient to permit writing of production guides for foods that could be used as such or combined suitably into meals. With funds provided by NASA, a contract was awarded for the development of prototypes along the line of meal components. These efforts have been described by Durst (ref. 9) and Brockmann (ref. 10). It was shown that by using the technology available, products such as beef, chicken, rice, potatoes, and vegetables could be combined with a calorie-containing matrix (developed from previous contract work on edible coatings) and compressed to provide 20,000 to 22,000 Kcal in approximately 10 lb and a volume of 408 cu in., a volume slightly larger than a shoe box. By various combinations of compressed sauce or gravymix cubes with compressed food bars, it was possible to provide 32 familiar foods (fig. 7). Admittedly, some of the foods were not highly acceptable but they provided a beginning.

[158] One can quickly see that this approach may have application for extended space flights or where prepositioned food supplies would be required. Menus could be planned using products based on these prototypes which would provide the weight and space savings that might be essential. Occasional supplementation with frozen foods such as steaks or other specialty items might assure the overall acceptance of such menus. Extension of this work is underway to improve the acceptance of the food items prepared from these basic "building blocks. "

Work is continuing on the compression of individual products such as peas (fig. 8), carrots, cherries, shrimp, meat balls, and sausage. Just recently we have been able to provide a memory in freeze-dried beef chunks. This beef, with added flavoring, can be compressed. Upon the addition of water, it will come back to its original shape. Meat balls behave the same way.

The procedure used with most products is as follows: the items are freeze-dried, then equilibrated to approximately 6 to 8 percent moisture and compressed at pressures from 500 to 1500 psi. After compression, redrying is accomplished either in a vacuum or convection oven. As might be expected, the appropriate procedure for each product has to be determined. For example, the cherries are successfully compressed without the addition of added moisture. Little or no noticeable damage is apparent in the reconstituted product if the compression phase is properly conducted (fig. 9).

Several specialized pieces of equipment are being utilized in studying the parameters of compression and texture in order to better understand what happens. By use of a universal test instrument with custom features we are attempting to determine the effect of storage at ambient and elevated (100° F) temperatures on compressed dehydrated food. Early subjective data obtained in....

....conjunction with storage studies focused attention on objectionable texture changes which occurred in storage. Although hardening is the most common complaint, we have found that not all cubes of the type presently used as space food harden during storage. Tables I and II and figures 10 and 11 show that the hardening or softening which take place during storage depends upon the nature of the material.

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From research to date we can project that the weight and volume advantages of compressed freeze-dried products will enable the provision of a wide variety of products at approximately 3. 76 cal/cc, as compared with the present average of approximately 1.41 cal/cc for uncompressed products. Defining the parameters for successfully compressing a variety of dehydrated food is continuing.

Additional varieties of freeze-dried foods will be needed to support flights of long duration or in any situations where prolonged consumption of dehydrated diets is necessary. For example, how about a rare steak ? Although it is generally not considered possible, as it loses red color when stored, we have indications that if a steak does not come in contact with oxygen after it is....

....placed in the freeze dryer we can have a rare steak of normal appearance. Also, we have data to indicate that oxygen-sensitive products, like carrots, have a markedly improved keeping quality if exposure to oxygen is minimized throughout processing and storage (figs. 12 and 13). There is a marked reduction in flavor deterioration when oxygen is totally eliminated. A glove-box technique was used for removing the product from the freeze dryer. In order to reduce the oxygen to this low level a palladium catalyst was employed in an atmosphere containing 5 percent hydrogen and 95 percent nitrogen. This technique is practical, especially for small lots of product. The palladium hydrogen system is being used commercially in England.

Continued research in the areas of texture and flavor, coupled with that of compression or densification, should provide products with greatly improved flavor and texture plus the marked advantage of drastic reduction in volume.

Intermediate-moisture foods are receiving attention by the food scientists and technologists Natick Laboratories has awarded contracts to apply this technology to products of military importance. Under one contract a wide variety of prototype products has been developed. Carrots, apples, and pork and beef, for example, have a moist mouth feel resembling the natural products in appearance, flavor, and texture and they also provide added calories per cc. Under normal storage conditions, no special packaging or refrigeration is required.

With NASA support, experiments have been carried out with a modified microwave oven. The smallest available commercial 1 kW unit (110V-AC 2450 MH) was reworked to reduce its weight by 39 percent and its volume, by 45 percent. The cavity is now 10 by 10 by 5 in. and will accommodate a small tray which can be used to quickly rehydrate and heat the rehydrated food or to heat....

[163] ....regular prepared food. The baking of bread and cakes at 6 psia in a special glass tube placed in the cavity is being investigated. Preliminary results indicate apparent feasibility of preparing bread from a special mix. However, to date, cakes have not been successful. Further reduction in weight and volume of the heating device can be achieved by use of smaller magnetrons, other types of oscillators, and solid-state components.

Using funds provided by NASA and the Air Force, Natick Laboratories now has under construction a room in which food can be processed in a controlled environment. It will enable the determination of contamination levels of products as they come into the room and pass through the various unit processes, and thus give a much better understanding of methods for controlling microbiological levels in food.

The work described clearly shows the mutual benefits that have been gained from the rather large R&D program carried out at the U. S. Army Natick Laboratories. The technology developed for Army field rations has been quickly brought to bear on the unique requirements of NASA and the Air Force. However, meeting these requirements has, in turn, been of considerable benefit to the Army program. A continuation of these combined efforts has the potential for providing a feeding system which would have maximum utility and acceptability for future missions.

1. Hollender, H.A.: Plugging the Holes. Activities Rept., vol. 15, no. 62, 1963.

2. Hollender, H.A.: Discussion Preparation, Handling, and Storage of Foods for Present Space Projects. NASA SP-70, 1964.

3. Klicka, Mary V.: Development of Space Foods. J. Am. Dietetic Assoc., vol. 44, no. 5, May 1964, pp. 358-361.

4. Klieka, Mary V.; Hollender, H.A.; and Lachance, P.A.: Development of Space Foods. Svenska Ekonomiforestandarinnors Tidskrift No. 1, Jan. 1966.

5. Klieka, Mary V.; Hollender, H.A.; and Lachance, P.A.: Foods for Astronauts. J. Am. Dietetic Assoc., vol. 51, no. 3, Sept. 1967, pp. 238-245.

6. Hollender, H.A.; Klicka, Mary V.; and Lachance, P.A. Space Feeding: Meeting the Challenge. Cereal Sci. Today, vol. 13, no. 2, 1968.

7. Rubinate, F.J.: Army's Obstacle Course Yields a New Look in Food Packaging. Food Technol., vol. 18, no. 11, 1964.

8. Szezeblowski, J. W.; and Rubinate, F.J.: Integrity of Food Packages. Modern Package, Vol. 38, no. 10, June 1965, pp. 131-134.

9. Durst, J.R.: Compressed Food Components to Minimize Storage Space. Tech. Rept. 68-22-FL AD-662060, Contract DA19-129-AMC-860, U.S. Army Natick Labs., 1967.

10. Brockmann, M. C.: Compression of Foods. Activities Rept., vol. 18, no. 2, 1966, pp. 173 -177.

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