Design of a Food Service and Food Processing System for Long-Duration Missions in a Closed Environment

JOHNSON SPACE CENTER IS DESIGNING AND BUILDING A HABITAT (the Advanced Life Support System Integration Test Bed (ALSSITB), formerly known as BIO-Plex) intended to evaluate technologies for advanced life support systems for use in long-duration missions where all consumables will need to be recycled and reused,¹ as well as containing high amounts of protein and oil.²

A prototype soymilk machine SoyaCow™ (supplied by ProSoya, Ottawa, Canada), was used for the production of soymilk and okara (pulp fiber by-product of soymilk). The machine consisted of a steam generation component and a heating chamber fitted with a grinder and a patented sieve, which allows the circulation of the soaked beans for optimum grinding and cooking. The objective of this project was to determine the constraints of utilizing a prototype machine to convert raw soybeans to soymilk as part of an Advanced Life Support System. Details of the finding have been submitted for publication (see below).

Materials and Methods
The SoyaCow™, a prototype soymilk machine (ProSoya Inc., Ottawa, Canada), was used to make soymilk from the Hoty soybeans (Fig. 1).

Other materials and methods are described in greater detail in the submitted paper.³

Results and Discussion
Yield and Waste Generated. The Soyacow™ yielded an average of 1.74 Kg of soymilk, which represents 68 percent of the total weight (water + soybeans) placed in the machine. However, if the okara weight is considered (an average of 749 grams), the total yield of edible ingredients products increases to 98 percent. Weight lost during the process was attributed to steam and residues on the machine.

Methodological Analysis. No Salmonellae, Staphylococci, or coliform were detected in the fresh soymilk. The total aerobic count was zero. Therefore, the soymilk was safe to consume fresh. This was not, however, a sterilization process; therefore, the milk would require refrigeration to prevent spoilage.

Nutritional Analysis. Soybeans and their products could contribute significantly to a plant-based diet because of their high oil and protein content. In general, soy proteins are considered high quality; yet they are deficient in the sulfur-containing essential amino acids.⁴ A chart on "Essential Amino Acids" (Fig. 2) compares the SoyaCow™ soymilk and egg ratios of specific essential amino acids (EAA) divided by the total amount of EAA found in each sample. The EAA trend observed in soymilk from the SoyaCow™ agrees closely with that found for whole soybeans.⁴ Chemical scores for the soymilk (ratio of soymilk EAA/ratio of egg EAA × 100), shown as percentages in Fig. 2, indicate that isoleucine, methionine, and value are low in soymilk. Additionally, the soymilk and okara cystine value is a combination of cysteine+cystine; therefore, this EAA may also be low. These deficiencies in the soy products should be considered when planning a menu for long-duration missions.

Fig. 2. Essential amino acid (EAA) profile of soymilk, okara (from SoyaCow™ production), and egg, calculated as mg of EAA divided by total EAA in that sample. Chemical score for soymilk is shown above each EAA, determined by dividing the EAA profile of soymilk by that of egg and multiplying by 100 to obtain percent.

Consumption of raw soy products can lead to severe physiological effects. Trypsin inhibitor (TI), present in soybeans, has been associated with growth depression, pancreatic hypertrophy, hyperplasia, and adenomain experimental animals.⁵ The reduction of TI is accomplished by heating the beans at an optimum time/temperature combination (such as in the production of soymilk) without reaching complete inactivation of the TI since, in its active form, TI provides 30 to 40 percent of the amino acid cystine.⁵

Volatile (Off-gassing) Analysis. The impact on air quality of processing soybeans into soymilk needed to be ascertained since all processes occurring in long-duration space habitats will be performed in a completely enclosed environment. Air samples were screened for a specific set of volatiles to ensure that they did not exceed Spacecraft Maximum Allowable Concentrations.⁶ Table 1 shows the average and standard deviation of some of the accumulated volatiles for three soymilk production runs. The grinding portion of the cycle contributed only minor amounts of ethanol (0.37 percent of total ethanol detected). These compounds (Table 1) likely resulted from lipid oxidation and/or Maillard reactions during heating.⁷

To determine the accumulation of these compounds during a long-duration mission (180 days) for a crew of four, a hypothetical diet was used, in which soymilk was consumed as a beverage, as well as an ingredient in other items. This diet require the production of 138 batches of soymilk. During future manned tests in the ALSSITB, where it was assumed that SoyaCow™ would reside in the tunnel,⁸ which has a volume of 202m³. Table 1 shows 180-day SMAC values for the different volatiles as well as for total quantities expected to be generated during soymilk production in the tunnel (assuming no leaks to the other chambers in the ALSSITB). It is apparent from Table 1 that the SMAC values for all the compounds would be exceeded during the 180-day period if no appropriate trace contaminant control system were used. For example, acetaldehyde would exceed the SMAC value by 1,841 times and would result n an accumulation of 1,488 grams in the tunnel. The accumulation of these volatiles results from the soymilk operation alone and do not include other processes, such as making bread in a bread machine,⁹ which could potentially contribute to the increased accumulation of such volatiles as ethanol and acetaldehyde.

Water Use. For a single batch of soymilk, 2.25 liters of water were needed for processing and between 2 to 3 liters of wash water to clean the soybeans. Almost all the processing water was incorporated in the soymilk or okara. The wash water analysis resulted in an average of 36.5 mg/l inorganic carbon, 70.5 mg/l of total organic carbon (TOC), and 452.5 l mg/l total solids. If we assume that 138 batches of soymilk will be processed for a 180-day mission (0.76 batches per day) in which three liters of wash water are used in each batch (2.28 liters/day), there would be a total of 160 mg of TOC per day to be processed. To assess the contribution of this waste water to a potential waste water treatment system for space use, ISS is utilized as an example. The ISS system is baselined to process 100 liters of waste water per day; therefore the contribution from the soymilk processing would be 2-3 percent. Additionally, the ISS system is baselined to process 100,000 mg TOC per day. If similar waste water treatments are used in ALSSITB, the soymilk machine would contribute 0.16 percent to the waste system processing.

Conclusions
Integration of the soymilk machine into a food system for long-duration missions would result in the conversion of soybeans into edible products and, therefore, increase the closure of the food loop within an ALSS. Researchers assessed the impact of producing soymilk on various systems inside an enclosed habitat. Little waste was generated during the manufacture of soymilk. Okara can be used for additional fiber in various food formulations or to grow secondary ingredients, while resultant waste water would have minimal contribution to a recovery system, such as the one baselined for ISS. The nutritional profile of the soymilk and okara showed deficiencies in various amino acids, which problem should be corrected when planning a complete diet. Extensive air scrubbing for various volatiles should be implemented so as not to exceed the SMAC values for these compounds. With proper care, the production of soymilk from a prototype machine would comply with the requirements imposed by a closed system.

WHEAT GRINDER--Yael Vodovotz, UH post-doctoral fellow, prepares typical food for astronauts at the wheat grinder. This wheat grinder can be used in space because it does not create dust. Dr. Vodovotz holds a sample of the flour that will be used to bake bread in space.

References
¹B. Fu, P. E. Nelson, R. Irvine, and L. L. Kanach. "Processing of Nutritious, Safe and Acceptable Foods from CELSS Candidate Crops," Advances in Space Research 18 (1996): 241.
²R. M. Wheeler, C. L. Mackowiak, J. S. Sager, W. M. Knott, and W. L. Berry. "Proximate Composition of CELSS Crops in NASA's Biomass Production Chamber," Advances in Space Research 18 (1996): 43.
³Y. Vodovotz, C. T. Bourland, and C. L. Rappole. "Assessment of a Prototype Soymilk Machine for Use in an Enclosed Chamber," Advances in Space Research. (Submitted for publication.)
⁴E. Snyder and T. W. Kwon. "Nutritional Attributes of Soybeans and Soybean Products," in Soybean Utilization, N. Y.: AVI, 1987.
⁵K. C. Kwok and K. Niranjan. "Review: Effect of Thermal Processing on Soymilk," Int'l J. of Food Science and Technology 30 (1995): 263.
⁶SMAC, Spacecraft Maximum Allowable Concentration for Airborne Contaminants, NASA-JSC 20584 (1995).
⁷MacLeod, G. and J. Ames. "Soy Flavor and Its Improvement," CRC Critical Reviews in Food Science and Nutrition 27.4 (1988): 218-379.
⁸Y. Vodovotz, C. T. Bourland, and C. L. Rappole. "Advanced Life Support Food Development: A New Challenge," presented at the 27th ICES Conf., SAE No. 972363 (1997).
⁹Y. Vodovotz and D. Barta. "Wheat Processing in an Enclosed Environment: Hydroponically Grown Wheat to Bread," Life Support and Biosphere Science: Int'l J. of Earth and Space 5 (1998): 79.

SPACE PACKAGING--Charles Bourland, JSC Principal Investigator, displays a package of food ready for space travel. Each compartment contains a separate item that can be eaten by mixing with water or another liquid.

Publications
Bourland, C., V. Kloeris, B. Rice, and Y. Vodovotz. "Food Systems for Space and Planetary Flights," in Nutrition in Space Flight and Weightlessness Models, N.Y.: CRC Press (submitted).
Kloeris, V., Y. Vodovotz, L. Bye, C. Stiller, and E. Lane. "Design and Implementation of a Vegetarian Food System for a Closed Chamber Test," J. Life Support and Biospheric Science (in press).
Vodovotz, Y. and Barda D. "Wheat Processing in an Enclosed Environment: Hydroponically Grown Wheat to Bread," Life Support and Biosphere Science: Int'l J. of Earth and Space 5.1 (1998): 79-86.
Presentations
Kloeris, V., Y. Vodovotz, and C. Bourland. "Optimization of Chamber-Grown Crops for Menu Planning," 28th ICES, SAE No. 981559, 1998.
Rappole, C. "Assessment of a Prototype Soy-Milk Machine for Use in an Enclosed Chamber," solicited talk, Committee on Space Research (COSPAR) Conf., Nagoya, Japan, July 1998.
--. "Food Processing and Advanced Life Support," Commercialization Mtg. for NASA-JSC, Glenview, IL, Sept. 1997.
--. "Food Processing in Enclosed Environment: Hydroponically-Grown Wheat to Bread," 3rd Int'l Conf. of Life Support and biosphere Science, Orlando, FL, Jan. 1998.
--. "A Food Service R&D Odyssey," N. American Assoc. of Food Equipment Manufacturers Engineering Conf., San Antonio, TX, March 1998.
--. Invited speaker, Int'l Conf. on Closed Ecological Systems for Terrestrial and Space Appl., Rokkasho, Japan, July 1998.
--. Talk on food and nutrition, summer session, Int'l Space Univ., Cleveland, OH, July 1998.
--. Video interview on the ALS food system, delivered for BIO-BLAST (a multi-media program developed by the NASA classroom of the future), Wheeling Jesuit Univ.
Funding
"Food Ingredients Obtained from Inedible Plant Biomass to be Used for Extended Space Missions." NRA Proposal, Univ. of Puerto Rico, 2-yr grant; resubmitted.
"Process and Equipment Development for Production of Food Ingredients from Sweet Potato," NRA Proposal, Univ. of Georgia, 3-yr grant; resubmitted.
"Production of Ingredients from Wheat using an Extruder." NRA Proposal, Rutgers, the State Univ. of New Jersey, 3-yr grant; resubmitted.
"Volatiles Produced in a Closed Chamber by Various Food Processing and Preparation Equipment." NASA Center Director Discretionary Fund, 2 yrs, 1998, $50,000.
Instruction
"Food Service Systems in Space: A Challenge for the 21st Century," Hilton College of Hotel and Restaurant Management, Univ. of Houston.
NASA Activity
A pamphlet in print describing the priorities established in the Conference on "Nutrition Concerns for Long Term Space Travel," approved by NASA officials, will be published by NJ-NSCORT.
Various meetings to discuss an implementation timeline of a food system for long-duration missions; final report pending consensus of outside reviewers.
Requirements for the food system, the habitation module, and the tunnel are being finalized, under a reues for the manager of ALSITB for the need of a complete requirement document.
NASA-JSC hosted a bidders' conference to discuss the RFP for he Commercialization Space Center for Food Technology. A UH decision concerning affiliation is pending.

Contents
ISSO -- Institute for Space Systems Operations
1997-1998 Annual Report