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A bioregenerative diet is characterized by a high proportion of foods produced on site. The production and processing of foods into either ingredients or recipes entails certain labor requirements. Ideally these labor requirements should be estimated with a high degree of accuracy. Crew time is at premium and any amount of time spent on food preparation and processing is time not spent in conducting research and any other activities devised to improve the quality of life of the astronauts. Moreover, a wide variety of tasks are involved in the food preparation of a bioregenerative diet and the labor times of these tasks do not scale or increase in uniform fashion. Predicting food preparation labor requirements for varying crew sizes will require task specific models and data. Videotape analysis is a work measurement tool used in the manufacturing industry.

The food processing and preparation subsystem for bioregenerative lifesupport must combine food produced in-situ with resupplied food ingredients to provide a nutritionally balanced, palatable and varied diet for the station crew. We have approached these goals by developing a database of individual foods including recipe and processing information, panel acceptance data, nutritional analyses and cost estimates. Subsequently a linear programming optimization is used to select from among these foods a low-cost diet subject to constraints on nutrient content, overall acceptability, variety, and crew labor input. The database design, preliminary sensory testing results, and an optimized 1-day food list are presented..

Current projections for the crop mix in the Bio-Plex and the future Lunar bioregenerative life support system indicate that without supplemental oil production, the crew's diet will be extremely low in fat, with little refined oil available for food processing or preparation. Although soybeans, peanuts and dwarf brassica (similar to canola) have been suggested as oil crops, each one poses significant problems either in horticulture, harvesting, productivity or byproduct utilization. An alternative to plant oils is “single-cell oil” or SCO. Lipid-accumulating “oleaginous” micro-organisms may accumulate up to 60% of their dry weight as triglycerides. Their high growth rates enable them to synthesize lipids with far greater productivity than higher plant systems. The current top candidate species for use in a bioregenerative system is a yeast, Cryptococcus curvatus.

Most work on food production for long-duration missions has focused either on biomass production or nutritional modeling. Food processing, while not a basic life support technology, has the potential to significantly affect both life support system performance and the crew's quality of life. Food processing includes the following tasks: Separation of edible biomass (food) from inedible biomass Conversion of inedible biomass into foodstuffs (optional) Processing of foodstuffs into convenience ingredients or storable forms Storage management for locally produced foods and foods supplied from Earth Cooking and serving of fresh and stored foods Management of wastes and leftovers Cleaning and maintenance of equipment Questions to be answered in design of a food processing system include: What processing and labor-saving equipment is required, and with what capacity? How must earth-based processing technology be adapted for hypogravity?

Three significant problems with food supply in bioregenerative lifesupport systems are addressable through use of fermented foods. The quantity of inedible and marginally edible biomass can be reduced; the hedonic quality of the diet can be enhanced; and food storage constraints can be relaxed due to the superior keeping qualities of fermented products. The authors have assessed potentially available materials and fermentation processes used worldwide, to identify promising food fermentations for use in lunar and planetary stations. Conversion of inedible biomass into acceptable food may include hydrolysis of waste biomass to produce sweeteners and acidulants; fermentation of physically fractionated biomass such as leaf protein isolates into acceptable foods; mushroom cultivation on agricultural residues; and conversion of volatile fatty acids produced during waste treatment into edible microbial biomass.