Effect of pH at time of salting on the functional properties of pre-rigor beef

The functional properties of thawed pre-rigor beef that had been minced and salted or not salted when its pH value reached 6.8, 6.6, 6.4, 6.2 and 6.0, then immediately frozen, were determined. The mince samples were used to manufacture a finely comminuted sausage batter. Presalting before frozen storage resulted in higher (p < 0.05) thawed mince pH, and batter cook yield and shear strain, and lower (p < 0.05) mince salt soluble proteins, thaw drip and Hunter L^* and b^* values and batter shear stress than unsalted controls. The pre-rigor pH at time of salting/mincing affected (p < 0.05) thaw drip (unsalted mince only), Hunter L^* and b^* values and shear stress. Shear stress tended to increase (p < 0.01) and Hunter L^* (p < 0.05) and b^* (p < 0.01) values tended to decrease with fall in pre-rigor salting pH. No interaction (p > 0.05) between salting and pre-rigor pH at time of salting was observed.     

Chilled storage life of hot-boned, pre-rigor, salted minced beef

Pre-rigor beef mince with 2% added salt was stored under CO₂ at −1.5 °C (A). The same mince with 100 ppm sodium nitrite was stored under CO₂ at 5 °C (B) and −1.5 °C (C), and under vacuum at −1.5 °C (D). Microbiological and sensory analyses were carried out for up to 21 weeks. Indicative storage life was taken as the time for microbial numbers to reach 10⁷ colony forming units per g. Mince stored under regimes B or D attained these numbers by 6 and 14 weeks, respectively; mince stored under regimes A and C had not attained these numbers by the end of the storage trial. Mince stored at 5 °C developed storage flavours of sufficient intensity to be detectable by consumers by 9 weeks storage. In general, the other minces did not develop unacceptable levels of storage or off flavours. Over 90% of the added sodium nitrite had disappeared after 10 weeks of storage, partly through conversion to sodium nitrate. Mince pH was not affected by the storage conditions and remained at about 6.0. The water holding capacity of the pre-rigor mince deteriorated during prolonged storage.     

Effect of pressure treatments on the mechanical properties of pre- and post-rigor meat

Pressure-heat treatment of beef semitendinosus samples post-rigor gave shear and tensile results similar to those obtained with pressure treatment pre-rigor. Post-rigor pressure-heat treatment did not affect the contraction state, unlike pre-rigor pressure treatment which caused samples to contract by about 40%. Maximum tenderizing effect by pressure-heat treatment (150 M Nm⁻² at 60°C for 30 min) was achieved when samples were heated at 45°C for 45–180 min immediately before application of the treatment. As the pre-pressurization temperature was increased, the duration of heating became more critical until at temperatures ≥ 60°C the effects of subsequent pressure-heat treatment became very small. Pressure-heat treated samples did not show the increase in shear force values for cooking temperatures ≥ 60°C associated with myofibrillar hardening. It was concluded that pressure-heat treatment primarily affected the myofibrillar structure.     

Survival of enterohaemorrhagic Escherichia coli O157:H7 strain in Turkish soudjouck during fermentation, drying and storage periods

Soudjouck (a kind of Turkish sausage) batter was inoculated with Escherichia coli O157:H7 at a level of 10⁵ colony-forming unit (CFUg) and kept overnight at 4°C. After stuffing the soudjouck batter into natural casing, fermentation was carried out at 24±2°C and 90–95% relative humidity (RH) for 3 days with subsequent drying at 22±2°C and 80–85% RH for 5 days. Then, half of soudjouck samples were vacuum-packed in polyethylene bags and the rest were kept open. All samples were stored at 4°C (55% RH) for 3 months. E. coli O157:H7 and lactic acid bacteria counts, moisture contents and pH values of the samples were determined during fermentation, drying and storage periods. Results showed that count of E. coli O157:H7 decreased by 3 log unit during fermentation and drying periods. It was observed that this pathogen survived longer in vacuum-packaged samples (more than 2 months) than non-vacuum samples (more than 1 month).     

Physico-chemical and organoleptic properties of patties from hot, chilled and frozen goat meat

The effects of processing hot versus chilled goat meat, as such and after freezing in chunk or mince forms, were studied in relation to physico-chemical and organoleptic properties of patties. The differences in the pH of the meat samples were non-significant (P < 0·05) at 3–4 h post mortem (PM) at room temperature (30°C) and after 24 h at 4°C. The yield of the broiled patties, prepared from hot meat at 3–4 h PM, was significantly lower (P<0·05) as compared to those from chilled meat. However, this trend was reversed, if processing of hot meat into patties was done within 1–2 h PM. Freezing of chilled meat in chunk or mince forms gave significantly higher (P < 0·05) cooking yields than freezing of hot meat in similar forms.

The organoleptic scores of the raw-cooked patties were similar for all treatments. Freezing of precooked patties at −10°C for 10 days, thawing and reheating did not reduce most of the sensory scores significantly (P<0·05). Moisture, protein and fat contents of the broiled patties were not significantly (P<0·05) affected by the treatments. Standard plate count of hot versus chilled meat, for all levels of processing and storage, were within acceptable limits.     

Preparation and validation of a growth model for Bacillus cereus: the effects of temperature, pH, sodium chloride and carbon dioxide

The growth responses of a vegetative inoculum of Bacillus cereus as influenced by varying conditions of temperature, pH value and sodium chloride concentration (% w/v) and carbon dioxide concentration (% v/v) were determined in laboratory medium. Growth curves in concentrations of NaCl in the range 0.5–10.5% (w/v), pH values in the range 4.5–7.0, CO₂ concentrations in the range 10–80% (v/v) and storage temperatures from 10 °C to 30 °C were fitted using the regime of Baranyi et al. (1993). A response surface model was prepared and predictions of doubling time, growth rate, lag time and time to 1000-fold increase could be obtained for any set of conditions within the matrix studied. This model is included in Food MicroModel Version 1. Predicted doubling times from the model were compared to observed doubling times in the literature and the model was found to give realistic estimates of doubling time for a range of foods including milk, meat and poultry and carbohydrate-based products.     

Physiological properties of Lactobacillus paracasei, L. danicus and L. curvatus strains isolated from Estonian semi-hard cheese

Growth and survival of Lactobacillus paracasei (six strains), L. danicus sp. nov. (four isolates, two strains) and L. curvatus (two strains) from semi-hard Estonian cheeses were comparatively studied in different environmental conditions of relevance for their growth in cheese and survival in gastric environment. Maximum specific growth rates for L. paracasei strains varied between 0.40 and 0.57 h⁻¹, and all strains were tolerant to low water activities, heating at 60 °C for 30 min and pH 3. The newly discovered genetically distinct species L. danicus was characterized by low maximum growth rates (0.26–0.38 h⁻¹) and low temperature optimum (<30 °C). It was acid and heat sensitive and inhibited at salt concentrations from 4% and water activities below 0.93. L. curvatus was characterized by the highest growth rates (0.65–0.70 h⁻¹), tolerance to high NaCl concentrations, but sensitivity to heating, bile salts and low pH. The study showed that genetically different LAB species isolated from cheese could be distinguished by simple cultivation experiments.     

Effects of dietary vitamin E supplementation and packaging on the colour stability of sliced pasteurized beef ham

The effect of supplementation of vitamin E (2025 IU animal⁻¹ day⁻¹) in the diet of beef bulls on the colour stability of pasteurized beef ham was studied. Control and enriched diets were provided for the last 136 days before slaughter. Pasteurized hams were manufactured from Mm. semitendinosus from eight animals per dietary group. Half of the samples of sliced ham from control (CON) and supplemented (SUP) bulls were packaged under vacuum (VAC) and half in low-oxygen modified atmosphere packs (FOG, gas mixture: CO₂/N₂=50/50). The packages were kept under constant illumination for 28 days at 8°C. During storage, the number of colony-forming units (CFU) reached a maximum of 5x10⁷ g⁻¹. The microflora was dominated by lactic acid bacteria. The supplementation with vitamin E showed no effect on microbial growth. Lipid oxidation was stable during storage. A significant difference between both dietary groups was detected for the decrease in the redness values during storage. Redness values of CON vacuum-packaged samples decreased (P < 0.01) with time, whereas those for the SUP products only tended to decrease. The redness values of FOG-packed ham were higher than those of VAC-packed ham at the end of the display period, irrespective of the dietary group. Overall, colour appeared to be more stable in the FOG-packed products than in the VAC-packed products. It can be concluded that dietary supplementation of bulls with vitamin E appears to offer only a minor improvement in colour stability over current feeding regimens when the Mm. semitendinosus are used to make cured, pasteurized ham-type products.     

Thermal inactivation of lectins (PHA) isolated from Phaseolus vulgaris

The influence of the thermal process on the loss of ability to bind a carbohydrate target was studied on lectins (PHA) purified from Phaseolus vulgaris seeds. Thermal inactivation of aqueous solutions of pure PHA occurred according to a biphasic first-order mechanism, the thermodynamic parameters, at pH 7·3, being as follows: ΔH*₁ = ΔH*₂ = 86·2 kcal mole⁻¹, ΔS*₁ = − 54·04 cal deg⁻¹ and ΔS*₂ = − 56·71 cal deg⁻¹. The first-order rate constants appeared to be dependent on pH (minimal around 7) and divalent cations. All different subunits constituting the whole PHA were inactivated at the same rate. The biphasic nature of this process is independent of the presence of 10 m Ca⁺⁺ or Mg⁺⁺ and appeared to indicate a discrete aggregation of PHA molecules.     

The effects of residual oxygen concentration and temperature on the degradation of the colour of beef packaged under oxygen-depleted atmospheres

Samples of beef longissimus dorsi (LD), approximately 5 × 5 × 1 cm, were packaged in pairs under 10 litre volumes of N₂ or CO₂ containing O₂ at concentrations between 100 and 1000 ppm. The packaged samples were stored at temperatures of 5, 1, 0 or −1·5°C, for times between 4 and 48 h. Samples of beef psoas major (PM) were packaged under N₂ or CO₂ containing O₂ at between 100 and 600 ppm, and stored at −1·5°C for 24 or 48 h. After storage, each sample was assessed for colour deterioration and discoloration, and for the fraction of metmyoglobin in the surface pigment.

The results obtained with N₂ and CO₂ atmospheres were similar. The colours of all LD samples had deteriorated after 4 h storage at 5 or 1°C, although the degree of deterioration increased with increasing O₂ concentration. All LD samples stored for 12 h at 5 or 1°C were extensively discoloured, with metmyoglobin fractions generally exceeding 60%, but those stored at −1·5°C for 48 h or less, under O₂ concentrations ≤ 400 ppm had undergraded colours. The colours of some LD samples stored at −1·5°C under about 600 ppm of O₂ were also undergraded, but the colours of samples stored under 800 or 1000 ppm had deteriorated by 24 h. The colours of LD samples stored at 0°C under > 200 ppm had deteriorated after 24 h storage, and the colours of samples stored under 100 ppm O₂ had deteriorated after 48 h storage. All PM samples were wholly discoloured after storage at −1·5°C. Evidently, the colour of beef muscle of high colour stability is resistant to degradation by atmospheres containing < 600 ppm of O₂ when the meat is stored at sub-zero temperatures, but not when the storage temperature is at or above 0°C. Beef muscle of low colour stability, such as the PM, will discolour at all low concentrations of O₂ irrespective of the storage temperature.     

Conventional freezing plus high pressure-low temperature treatment: Physical properties, microbial quality and storage stability of beef meat

Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20 °C) pressurisation (650 MPa/10 min) and air blast freezing (−30 °C) are compared to air blast freezing plus high pressure at subzero temperature (−35 °C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650 MPa/20 °C/10 min) increased significantly expressible moisture while it decreased in pressurised (650 MPa/−35 °C/10 min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh samples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure processing (20 °C or −35 °C) was very effective reducing aerobic total (2-log₁₀ cycles) and lactic acid bacteria counts (2.4-log₁₀ cycles), in fresh and salt-added samples. Frozen + pressurised beef stored at −18 °C during 45 days recovered its original colour after thawing, similarly to just-treated samples while their counts remain below detection limits during storage.     

Thermal death kinetics and heating rate effects for fifth-instar Cydia pomonella (L.) (Lepidoptera: Tortricidae)

Thermal death kinetic parameters of fifth-instar codling moths (Cydia pomonella (L.)) and the effect of three heating rates (1°C min⁻¹, 10°C min⁻¹, and 18°C min⁻¹) on larval mortality were determined by a heating block system. The insects were heated to four temperatures (46°C, 48°C, 50°C, and 52°C) held for predetermined periods followed by 24 h storage at 4°C before mortality evaluation. Thermal death kinetics for fifth-instar codling moths followed a 0.5th order of kinetic reaction. Minimum time required to achieve 100% mortality of a given population decreased with temperature in a semi-logarithmic manner. No larval survival was observed in samples of 600 insects after exposure to 46°C, 48°C, 50°C, and 52°C for 50, 15, 5, and 2 min, respectively. Activation energy for thermal kill of fifth-instar codling moths at the heating rate of 18°C min⁻¹ was estimated to be about 472 kJ mol⁻¹. The lethal time accumulated during the ramp period was about 1.8, 0.2, and 0.1 min for the heating rates of 1°C min⁻¹, 10°C min⁻¹, and 18°C min⁻¹, respectively.     

The effects of antifreeze proteins on chilled and frozen meat

The effects of cryoprotectant proteins, trivially termed ‘antifreeze proteins’, from the Antarctic Cod and the Winter Flounder were assessed in meat during chilling and freezing. In light-microscopy studies, bovine muscle (Sternomandibularis) samples were soaked in phosphate buffered saline with and without 0·1 mg/ml antifreeze protein. Samples were then held frozen (−20°C) or chilled (2°C) for 3 days. Samples were freeze-substituted, embedded in resin and sectioned. With antifreeze protein present, transverse sections of frozen samples had many small intracellular spaces, probably representing ice crystals. Frozen controls had much larger intracellular single spaces. Antifreeze protein had no effect on chilled samples.

Similarly treated samples were examined by scanning electron microscopy using a cryostage attachment. Chilled ovine muscle samples (Peroneus longus) were soaked for various periods (0–7 days) in 0·9% saline containing various concentrations of antifreeze proteins (0–1 mg/ml). Samples were then held frozen (−20°C) or chilled (2°C) for 5 or 7 days. With frozen samples, antifreeze proteins reduced the size of ice crystals, compared to the control. This effect depended upon the concentration used and the period of soaking before the samples were frozen, but was independent of source. Antifreeze proteins had no effect on chilled samples.     

The effect of glucose supplementation on the spoilage microflora and chemical composition of minced beef stored aerobically or under a modified atmosphere at 4 °C

Glucose was added to minced meat (pH 6.0) and stored under aerobic or a modified atmosphere (MA) composed of 80% O₂ and 20% CO₂ to assess the effects of carbohydrate on the microbial association and the chemical properties of the meat. The type of packaging affected the size and the final composition of the microflora. The microbial composition of the mince without added glucose in air or MA, given in log₁₀cfu/g respectively, were pseudomonads (9.8 and 7.3), Brochothrix thermosphacta (8.5 and 8.1), lactic acid bacteria (8.8 and 8.7), Enterobacteriaceae (7.2 and 6.1) and yeasts (4.3 and 4.2). In mince supplemented with 0.2% (w/w) glucose, similar composition and numbers were observed. Glucose, glucose 6-phosphate and lactic acid were consumed at slower rates by the flora on meat stored under MA than by the flora on meat stored in air. The addition of glucose enhanced gluconate production by the flora on meat stored in air. D-lactic and acetic acid were produced in all samples stored under the MA.     

Calpains from thaw rigor muscle

Pre-rigor beef M. Longissimus lumborum and diaphragma were frozen at −70 °C and thawed at different temperatures and the activities of extracted calpains and the toughness of heated meat compared with those in chilled muscle.

Fresh muscle contained about 14 μg of μ-calpain/g and was unaffected by freezing, but was reduced after thawing. Rapid thawing at 30 °C for 20 min reduced the μ-calpain to 14%. When cooked from the frozen state, extensive shortening occurred and tender meat was obtained.

By storing at −3 °C for 1 day, thaw-shortening was prevented, but tougher meat obtained. The μ-calpain decreased to 70% whilst the m-calpain was unaffected. Toughness decreased after further storage at −3 °C, as did the μ-calpain. The latter changes were similar to those during development of rigor mortis and ageing of non-shortened meat stored at 4 °C. Variation in calpain activity, rather than in sarcomere length, are likely to be the cause of toughness variation in thaw rigor muscle.     

Prediction of Listeria spp. growth as affected by various levels of chemicals, pH, temperature and storage time in a model broth

The effects of concentration of NaCl (0.5 to 12.5%), methyl paraben (0.0 to 0.2%), sodium propionate (0.3%), sodium benzoate (0.1%), potassium sorbate (0.3%), pH (>5.9) temperature (4 to 30°C), storage time (up to 58 d) and inoculum (>10⁵ to >10⁻² per ml) on the log₁₀ probability percentage of one cell of Listeria spp. to initiate growth in a broth system were evaluated in a factorial design study. At pH 5.96 and temperature ranging from 4 to 30°C the concentrations of sodium propionate, potassium sorbate, and sodium benzoate examined allowed growth of L. monocytogenes with lag phases at 4°C of 18, 27 and 21 days, respectively. For 0.1 and 0.2% methyl paraben growth of all Listeria spp. was initiated at 8°C and 30°C, respectively. At pH 6, concentration of 12% NaCl supported the growth of L. monocytogenes at 8 to 30°C, whereas 12.5% inhibited all Listeria species. Four regression equations were derived relating probability of growth initiation to temperature, concentrations of NaCl and preservatives storage time, and Listeria species specific effects. From these equations, the number of cells needed for growth initiation can be calculated. The impact of this type of quantitative study and its possible application on the development of microbial standards for foods is discussed.     

Studies on tenderization and preparation of enrobed pork chunks in microwave oven

This study was conducted to develop technology for tenderization and production of enrobed pork chunks in a microwave oven. Meat chunks from shoulder cuts of pork were cured in a solution containing salt, sodium tripolyphosphate and sugar for 48 h at 4 ± 1 °C, enrobed with cream based batter and cooked in a microwave oven at 900 MHz. These enrobed chunks (control) were compared with tenderized (treated) enrobed chunks, for which 7.5% cucumis extract, 9% ginger extract and 0.50% papain powder were incorporated in the standard curing solution. Ginger and papain treatments caused significant (P < 0.01) increases in the moisture content and pH of the cooked products compared to the control and cucumis treated samples. Shear force values were significantly (P < 0.01) lower and overall acceptability scores were significantly (P < 0.01) higher in all treated samples compared to the control. During storage at 4 ± 1 °C, the moisture contents and sensory qualities decreased, but TBARS values and microbial counts increased significantly (P < 0.01). Although all products were acceptable up to 15 days of storage, the ginger treated samples had significantly (P < 0.01) lower TBARS and microbial loads and higher sensory attributes than the control, cucumis and papain treated samples. The magnitude of the storage changes were less and acceptability ranking was higher for the ginger treated samples compared with the others. The results indicated that microwaves could be used for the preparation of enrobed pork chunks. The overall acceptability and shelf life of microwave cooked enrobed pork chunk can be further improved using ginger extract in the curing solution.     

Identification of halothane genotypes by calcium accumulation and their meat quality using live pigs

The three halothane genotypes (NN, Nn, and nm) were identified by measuring the capacity for Ca²⁺ accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of M. longissimus dorsi with a Ca²⁺ specific electrode at 35°C. Significant differences (P < 0·001) in deterioration (%) of Ca²⁺ accumulation, 12% for NN, 35% for Nn, and 81% for nn pigs, were observed after ageing the whole muscle homogenate preparations for 24 h in ice.

Predictions of meat quality in live pigs (n = 34) based on the values for water-holding capacity, assessed as fluid (g/0·5 g wet wt LD), and pH (fluid) by using small biopsy LD samples (Cheah et al. 1993) were performed on all the halothane genotypes. The halothane genotype NN (n = 11) showed a fluid value of 0·37 ± 0·01 and a pH (fluid) value of 6·62 ± 0·03 as compared with 0·61 ± 0·02 and 5·84 ± 0·04, respectively, for the halothane genotype nn (n = 13). The Nn pigs (n = 10) showed fluid (0·49 ± 0·03) and pH (fluid) (6·19 ± 0·11) values between those values observed for the two homozygotes (NN and nn). Predictions of meat quality in live pigs from biopsy LD muscles were confirmed from assessments on post-mortem LD muscles based on pH₁ and fibre optic probe (FOP) measurements.

The extent of deterioration (%) in Ca²⁺ accumulation showed high correlations with fluid (r = −0·861) and pH (fluid) (r = −0·831) in the biopsy LD samples, and with pH₁ (r = 0·663), FOP (r = −0·812), and drip (%) loss (r = −0·777) in the post-mortem LD samples.     

The chilled storage life and retail display performance of vacuum and carbon dioxide packed hot deboned beef striploins

Two cooling regimes that complied with the New Zealand meat hygiene requirement that hot deboned meat be chilled to +7 °C or less within 24 hr of leaving the slaughter floor were evaluated for the production of chilled table meats. Electrically stimulated hot deboned bull beef half striploins were either vacuum or carbon dioxide packed before being cooled in accordance with either Regime 1 (cool at +5 °C for 24 hr, transfer to chiller operating at −1.0 ± 0.5 °C) or Regime 2 (cool at +5 °C for 24 hr, hold at 5 °C for 6 days, transfer to chiller operating at −1.0 ± 0.5 °C). Striploins were removed from −1.0 °C storage 8, 28, 42, 56, 70, 84 and 98 days after slaughter and subjected to microbiological, tenderness, sensory and retail display performance evaluations.

Both Regimes 1 and 2 produced meat of acceptable mean tenderness, 8 kgF (MIRINZ Tenderometer) in either vacuum or carbon dioxide packs within 28 and 8 days of slaughter, respectively. However, 70 days after slaughter the first signs of over-ageing became apparent. Steaks from Regimes 1 and 2 maintained acceptable visual appearance during retail display at 5 °C for 48 hr and 24 hr, respectively. After these times, the product was judged by the panel to be unacceptable because of its dull dark lean tissue and grey to green discoloration of the fat. Poor colour stability during retail display was mirrored by deterioration of sensory attributes, particularly aroma which is indicative of incipient spoilage. While carbon dioxide packaging in combination with Regime 1 offered an initial microbiological advantage over vacuum packaging, this advantage was not, however, carried over into retail display.

Poor colour and sensory stability during retail display suggest that chilled table cuts derived from hot deboned bull beef are more suited to the Hotel-Restaurant-Institutional (HRI) trade than supermarket retailing. To serve the HRI, vacuum packed hot deboned bull beef primal cuts processed by Regime 1 appear to be the combination of choice. This combination would enable commercial processors to produce quality table beef with a chilled storage life of up to 70 days.     

Design, fabrication, and testing of a returnable, insulated, nitrogen-refrigerated shipping container for distribution of fresh red meat under controlled CO2 atmosphere

In today's market, fresh red meat is cut and packaged at both the wholesale and retail level. Greater economies could result if the wholesaler prepared all consumer cuts centrally, but the short storage life of meat limits distribution. Use of CO₂-controlled atmosphere, master packaging, and strict temperature control (−1.5±0.5°C) can enhance storage life and, therefore, distribution ease. An insulated shipping and storage container was designed and tested for its suitability to distribute master-packaged meat. Shelves in the container supported 36 master trays (508 × 381 × 60 mm), with the source of refrigeration being injected liquid nitrogen (N₂). Electric fans dispersed the N₂ gas throughout the container. To reduce costs, 36 saline water bags (10% w/v NaCl) were used to thermally simulate the meat. Temperatures of 20 bags were recorded during storage experiments. The container was tested at outside temperatures of 15, 0 and −15°C with 4 internal fans and at 30°C with 2, 4 and 6 fans. In all instances, bags cooled from 10°C to an equilibrium temperature of −1.5°C within 5.5 h. Minimum equilibrium temperatures during any 8 h trial were −2.6, −2.0 and −2.0°C for 2, 4 and 6 fans, respectively. Correspondingly, maximum temperatures were −0.2, −0.7 and −0.3°C. Initial chilling of the product required, on average, 19 kg of N₂, while equilibrium was maintained at a N₂ consumption rate of 5.5, 4.0, 2.6 and 0.93 kg/h at outside temperatures of 30, 15 0 and −15°C, respectively, with 4 fans. The N₂ use for 2 and 6 fans was 5 and 6.3 kg/h, respectively, at an outside temperature of 30°C. During simulated power failure or when the N₂-tank ‘ran dry', temperatures in the container rose 0.9 and 2.0°C/h, respectively. When the door to the container was opened long enough to remove three trays, temperature was restored within 5 min. Convective heat transfer coefficients between saline water bags and circulating N₂ were in the range of 80–100, 115–135, and 140–155 W/(m²·K) for 2, 4 and 6 fans, respectively. Heat transfer to meat will be limited by conduction in master packaged meat if similar convection coefficients prevail.