Freeze-Dried Oat- and Rice-Based Porridges for Military and Emergency Rations: Formulation, Long-Term Storage Stability, Rheological Behaviour and Exploratory Sensory Evaluation

Lightweight, shelf-stable and acceptable meal components are required for military, emergency and humanitarian feeding systems. This study evaluated freeze-dried oat- and rice-based porridges, formulated as three recipe variants per matrix and packed in vacuum-sealed PET/ALU/PE laminate pouches. Samples were stored at 5, 25 and 40 °C for up to 18 months and assessed for physicochemical stability, rehydration-relevant rheology, microbiological safety, chemical composition and exploratory sensory quality. Freeze-drying reduced water activity to a very low range, and low aw, stable near-neutral pH and microbiological monitoring indicated no storage-related microbial outgrowth. Oat formulations contained higher protein and lipid fractions, whereas rice formulations were more carbohydrate-dominant, with no major macronutrient drift at the 12-month endpoint. Rheology revealed clear matrix-dependent behaviour: oat porridges were more viscous at comparable nominal formulation levels, whereas rice porridges showed stronger temperature-dependent thickening during heating. Exploratory condition-level analyses showed crude associations between apparent viscosity and positive sensory scores, particularly in rice porridges, but these associations were not independently distinguishable after adjustment for formulation, storage month and storage temperature. The results show that freeze-dried porridges may serve as ration components under the investigated conditions when formulation balances low-aw safety, structural stability, rehydration behaviour and exploratory sensory quality.