Modifications were incorporated into the task research methods in early FY10. These included the introduction of peroxide value determination as an analytical indicator of peanut sample quality, and the addition of water activity (Aw) measurements as an indicator of dry cereal quality. To date, these methods have benefit the study; peroxide value determination has allowed increased correlation of analytical and sensory data for peanuts samples, and water activity measurement has allowed additional insight into packaged dry cereal stability. These measurements will therefore continue to completion of the study.
A qualitative comparison of the flexibility of the clear packaging materials (Combitherm® and Tolas®) was conducted during the period. Although the Tolas® material displayed less flexibility and greater incidence of creasing, its seal and packaging integrity was found to be comparable to that of the Combitherm® material.
The Comparative Packaging Study seeks to determine the adequacy of 3 types of packaging materials currently being considered for use in extended duration missions. The current packaging system for the International Space Station (ISS) food system consists of a primary package enclosed within a secondary overwrap. The primary package is a minimal barrier, transparent material (Combitherm®) aiding in processing and quality control; while the secondary overwrap is a high barrier, opaque material that ensures the product is protected and can meet the minimum shelf-life requirement of 18-months. While the overwrapped system consistently guarantees shelf-life, it also generates more mass, waste, and labor than would a single material system. Investigation of these materials will provide information to aid in assessing the compatibility of the current packaging system with long duration missions. Evaluation of a third material, translucent, high barrier material(Tolas®) will provide information on its long-term performance and feasibility for incorporating the material into long duration missions. Additionally, successful performance of the Tolas material without overwrapping to 18 months may allow reduction of the current system to a single package. The Comparative Packaging Study is being performed to evaluate the effectiveness of the Tolas® material against our current primary packaging material (Combitherm®) and a material similar to our current overwrap (Technipaq®). Food items have been packaged in the materials, and put into storage at 25%, 50%, and 75% relative humidity. The quality of the food items has been evaluated at 3 month intervals. The study is currently approaching 15 months.
In general, storage at increasing humidity levels appears to affect the quality of foods packaged in Combitherm® and Tolas® materials. Instrumental evaluation of oil and sensory evaluation of peanuts suggested that prolonged storage at 75% RH is not appropriate for high lipid products packaged in the Combitherm® material. Long-term, high-humidity storage of Combitherm® oil and peanut samples appears to allow extensive oxidation of lipids in the foods.
Analytical and sensory evaluation of cereal samples suggests that storage at increasing relative humidities results in increased moisture absorption by low moisture products packaged in Combitherm® and Tolas® materials. The Combitherm® material was the most sensitive to both 50%RH and 75%RH storage; however, the Tolas® material did show significant moisture permeation at 75%RH. Sensory differences were typically observed after cereal moisture content had exceeded 8.00% moisture. Sensory differences were noticed for Combitherm® cereal after 12 months of storage at 75%RH and 15 months of storage at 50%RH. Similar differences were observed for the Tolas® cereal samples after 15 months of storage at 75%RH.
Although sensory evaluation did not measure product palatability, it is likely that the moisture induced changes observed in these samples affect quality negatively. Therefore, a secondary package will be required to preserve the quality of low moisture products in Combitherm® and Tolas® materials in high humidity storage.
3.0 Next Steps
The Comparative Packaging Study will continue through to FY 11, as outlined in the Directed Research Project Plan. Analytical measurements will continue to 36 months, to provide data on the long-term performance of the materials. A feasibility assessment will be conducted to evaluate the mass savings, practicality, and process modifications necessary to incorporate the Tolas® material into current flight food processing.
The reason to conduct shelf life testing, using a variety of packaging materials, stems from the need to preserve food used for mission durations of several years. Chemical reactions that take place during longer durations may decrease food quality to a point where crew physical or psychological well-being is compromised. This can result in a reduction or loss of mission success. The rate of chemical reactions, including oxidative rancidity and staling, can be controlled by limiting the reactants, reducing the amount of energy available to drive the reaction, and minimizing the amount of water available. Water not only acts as a media for microbial growth, but also as a reactant and means by which two reactants may come into contact with each other.
Two food products, dry cereal and peanuts, and one ingredient, cottonseed oil, susceptible to oxygen and water vapor ingress were packaged in three different packaging materials and incubated at a fixed temperature (72 degrees F) and varying relative humidity. Storage at three relative humidities (25%, 50%, 75%) will simulate the midpoint and potential ranges of humidities on the Orion vehicle. Relative humidity is an important variable since it may impact the barrier properties of certain materials.
At three month intervals, sensory and quantitative analysis are being performed on the food items to measure changes due to oxygen and moisture migration through the packaging. Free fatty acid (FFA) and peroxide value (PV) are being performed on the oil for quantification of oxidative rancidity. Moisture analysis quantifies the moisture ingress of the cereal and hexanal analysis quantifies the level of rancidity in the peanut samples. Sensory methods, used only for cereal and peanuts, include Difference from Control testing which indicates when the food has changed enough for consumers to notice a difference. The data associated with the three packaging materials will be compared in order to determine which is best suited for future exploration missions.