Flash heating process for efficient meat preservation

Meat is a vital source of proteins, fatty acids, vitamins, and minerals (iron, zinc), and global consumption has exceeded 300 million tons since 2018. However, fresh meat is highly perishable due to its nutrient-rich composition that supports growth of spoilage organisms and foodborne pathogens. Preservation commonly relies on low-temperature storage (chilling, freezing, super-chilling), which maintains freshness better than drying, smoking, canning, chemical preservatives, or biopreservation. Yet, maintaining a continuous cold chain is energy intensive and vulnerable to disruptions during transport that can lead to spoilage and contamination. To address these challenges, the study proposes and demonstrates an ultra-high-temperature flash heating (UFH) surface treatment that rapidly heats only the outermost layer of meat via radiative Joule heating of a carbon substrate (> ~2000 K in <1 s). The goal is to inactivate surface microorganisms and create a thin dehydrated barrier to inhibit inward microbial migration, extending shelf life at room temperature while preserving interior texture and nutrients.

The UFH concept adapts flash Joule heating approaches previously used in materials science (e.g., sintering ceramics, synthesizing high-entropy catalysts, depolymerizing plastics, converting waste) to food preservation. Compared with conventional food heating methods (boiling, baking, grilling), UFH operates at much higher temperatures and vastly shorter timescales; while a butane torch can approach similar temperatures, its convective heat transfer is orders of magnitude slower. Conventional preservation (drying, dry-curing) inhibits microbial growth by lowering water activity but markedly alters texture and flavor. UFH aims to achieve similar microbial inhibition through rapid surface dehydration and inactivation without bulk quality degradation.

UFH setup and operation: A flexible carbon felt (AvCarb G280A, 4 × 2.5 cm) serves as the heating element, clamped to graphite plates and powered by a programmable DC source (0–50 A, 0–100 V; typical ~1800 W for <1 s). During a standard cycle, the felt reaches a peak of ~2100 K for ~0.2 s (total high-temperature period ~0.2 s) and can be used singly or in pairs to heat one or both surfaces. Felt temperature was measured by high-speed camera (200 fps) with color ratio pyrometry. Samples: Beef purchased locally was cut into 1 cm³ cubes. For experiments, cubes were allocated to UFH-treated and control groups and stored frozen prior to use. UFH treatment: Beef cubes were placed in direct contact with the heated felt (or sandwiched between two felts) for sub-second pulses, sequentially treating all six faces. Thermal modeling: A 2D finite-element COMSOL model simulated transient heat and moisture transport with a single face exposed to a 2000 K heating boundary for 1 s, ambient air at 293 K elsewhere, and initial bulk temperature of 253 K. The 10 s simulation captured heating and cooling, phase change (melting) and evaporation. Outputs included depth-resolved temperature and water content over time. Microbiological assays: For each time point, 5 g of sample was homogenized in 45 mL buffered peptone water and serially diluted (up to 10⁻¹⁰ for long-term). Petrifilm plates (3M) were used for aerobic plate count (APC; 35±1 °C, 48 h; 25–250 CFU countable range), Enterobacteriaceae (EB; 35±1 °C, 24 h; 15–100 CFU), and Yeasts and Molds (YM; 25±1 °C, 48 h; 10–100 CFU). Short-term evaluations covered 24 h; long-term covered up to 100 h. Growth was modeled using the Baranyi-Roberts model. Detection limits for APC and EB were 0.70 and 0.48 log CFU/g, respectively. Current tests did not include bacterial spores. Quality and composition analyses:

• Rheology and texture: Strain sweeps on 2 mm thick samples using a rheometer (parallel plate geometry) to obtain storage (G′) and loss (G″) moduli and classify texture (tough, rubbery, mushy, brittle) via plateau stress/strain at the end of the linear viscoelastic region.
• Color: Euclidean distance of RGB values from images (50 random pixels) relative to fresh reference.
• Chemistry: Non-protein nitrogen (NPN), pH, and total volatile basic nitrogen (TVB-N via Conway method) tracked freshness and protein degradation; total protein via nitrogen determinator (Leco TruMac N; N→protein factor 6.25).
• Water activity: Surface a_w measured during storage (reported in Supplementary). Safety and structural characterization:
• Cytotoxicity: 3T3-L1 and CCD18co cell lines cultured with extracts from UFH-treated surfaces to assess viability.
• HPLC-MS: Acrylamide quantified; HAA and benzo(a)pyrene screened by full scan.
• Morphology/composition: SEM (Tescan XEIA FEG) on freeze-dried samples with 1 nm Pt coat; EDS for elemental composition; Raman spectroscopy (532 nm, 10×, 600 g/mm) to assess carbon structure (D/G bands).
• Histology: Formaldehyde fixation, cryosectioning, optical microscopy to measure treated layer thickness.

• UFH produces a thin (~100 µm) carbonized, dehydrated surface layer that seals the meat while leaving the interior visually and texturally similar to fresh meat. SEM shows a roughened surface; EDS indicates surface composition dominated by carbon (C 77.12%, O 19.22%, N 3.66%); Raman shows enhanced D (~1374 cm⁻¹) and G (~1596 cm⁻¹) bands, consistent with poorly ordered carbon.
• Thermal behavior (experiment and simulation): Carbon felt rapidly reaches ~2000 K; meat surface temperature rises to ~900 K within 1 s, then cools below ~400 K by 5 s post-heating. Regions deeper than ~2 mm experience minimal temperature rise, preserving internal proteins and texture. Modeling indicates formation of a dehydrated layer up to ~1 mm (water loss near surface).
• Microbial control at room temperature: • Short-term (24 h): In untreated beef, APC and EB increased rapidly. In UFH-treated beef, APC remained below detection up to ~22 h and EB up to 24 h (detection limits: APC 0.70, EB 0.48 log CFU/g). • Long-term (100 h): Untreated beef showed rapid growth in APC, EB, and YM (YM became detectable after ~20 h and increased strongly by 100 h), surpassing spoilage thresholds; UFH-treated beef showed no detectable YM throughout 100 h, and APC remained below the USDA AMS critical limit of 4.0 log CFU/g even at 100 h, whereas untreated exceeded this limit after ~12 h.
• Water activity: Surface a_w maintained near ~0.8 for UFH-treated samples over 80 h vs ~0.99 for untreated, a key factor in inhibiting microbial growth.
• Quality preservation: After 100 h at room temperature, UFH-treated samples retained higher G′ and G″ (≈4× untreated), with texture remaining “tough.” Untreated samples transitioned toward “mushy,” indicating protein degradation. Color measurements (RGB Euclidean distance) in UFH-treated centers remained near fresh reference over 80 h, while untreated darkened notably.
• Chemical freshness markers: UFH-treated samples showed essentially unchanged NPN, pH, and TVB-N over storage. Untreated samples: NPN increased from ~24 to ~31 mg/g; pH rose from 5.6 (±0.02) to 7.2 (±0.3); TVB-N increased ~10-fold by 80 h.
• Safety: Cytotoxicity assays showed no decrease in viability for 3T3-L1 and CCD18co cells exposed to UFH-treated surface extracts. Acrylamide was <7 ppb (well below EU 500 ppb benchmark); HAA and benzo(a)pyrene were not detected.
• Practical outcome: UFH extended shelf life of beef at room temperature to ~5 days (~100–120 h) without compromising internal appearance, texture, or nutrients.

UFH effectively addresses the preservation challenge by combining instantaneous radiative heating with surface dehydration to inactivate microorganisms and lower water activity at the meat surface, forming a barrier that also limits inward microbial migration. The heating is confined to the exterior few millimeters, preserving the interior from protein denaturation and quality changes associated with conventional, slower heating methods. The radiative-dominated heat transfer reduces the need for perfect surface contact, enabling treatment of rough and irregular geometries. The method maintained safety (no detectable YM, APC below critical limits), quality (texture and color retention), and nutritional markers during room-temperature storage. Safety assessments indicate negligible formation of concerning heat-induced contaminants and no cytotoxicity from the carbonized layer. UFH can serve as a stand-alone surface treatment or as a complement to cold-chain logistics to mitigate risks during temperature excursions. Its flexibility and potential scalability suggest applicability to large carcasses; the protective charred layer could be trimmed prior to retail to address consumer acceptance. Overall, UFH offers a fast, additive-free, energy-lean preservation approach that substantially delays spoilage processes compared with untreated meat.

This work introduces ultra-high-temperature flash heating (UFH) as a rapid, surface-targeted preservation method for meat. By briefly heating a carbon substrate to > ~2000 K and radiatively treating meat surfaces, UFH forms a ~100 µm microbe-inactivated, dehydrated layer that maintains low surface water activity and inhibits microbial growth. Beef treated by UFH maintained safety and quality markers and achieved room-temperature shelf life of about 5 days, while untreated controls spoiled rapidly. The process preserves internal texture and nutrients, generates minimal heat-induced contaminants, and is compatible with irregular surfaces, suggesting scalability to industrial carcass treatment. Future research should optimize heating parameters to reduce or avoid surface carbonization, evaluate efficacy on fresh meats and diverse species/cuts, incorporate bacterial spore assessments, and conduct full life cycle and techno-economic analyses to guide device optimization and deployment strategies.

• Microbiological testing did not include bacterial spores.
• Experiments were conducted on beef (model system), with primary demonstrations on small cubes and frozen-start conditions; broader validation across fresh meats, cuts, and scales is needed.
• The treated surface exhibits a charred appearance that may impact consumer acceptance; removal at retail is proposed but adds a processing step.
• Full life cycle assessment and detailed techno-economic evaluation were not performed and will depend on application scale and distribution scenarios.
• Reported room-temperature storage assessments were up to ~100 h; longer-term stability and performance under varied environmental conditions require further study.