Growth Of Psychrotrophic Bacteria Research Articles

Influence of salt concentration on microbial growth in Kashkaval cheese

The aim of the present study was to evaluate the influence of NaCl concentration on the microflora in Kashkaval cheese produced from cow’s milk. Three cheese samples were obtained - with low (0.7%), medium (1.5%), and standard (3.1%) content of NaCl. Microbiological analyses were performed on the 1st, 15th, 30th, and 45th d of cheese ripening. It was established that the NaCl content has a significant (p < 0.05) influence on the growth and activity of the microflora in studied samples. It has been observed that the total Lactic acid bacteria (LAB) increased up to 30 d during ripening, after which their concentration decreased. A higher LABs count of samples with 0.7% NaCl and 1.5% NaCl in comparison with those containing 3.1% NaCl was found. At the same time, the variations in the salt content do not have a significant (p > 0.05) impact on the growth of Psychrotrophic bacteria, while in samples with a low salt content, the growth of Yeast and Molds was more intense. The data obtained in the present study showed that the concentration of NaCl is important for the regulation of activity of microbiological processes during the ripening of the Kashkaval cheese samples.

Effect of Herbal Addition on the Microbiological, Oxidative Stability and Sensory Quality of Minced Poultry Meat.

The study aimed to assess the effect of herbal additions with antioxidant properties (pepper, thyme and oregano) on the microbiological and oxidative stability as well as the sensory quality of minced poultry meat. Meatballs treatments without additives and treatments with the addition of three types of spices in two forms—dry spices and industrial extracts were examined. Popular seasoning additives of oregano (Origanum vulgare), thyme (Thymus vulgaris) and black pepper (Piper nigrum) at 0.3% of dry herbal or 0.003% as industrial extract were added to minced meat. The microbiological, chemical and sensory tests were performed at specified times and storage temperature. Based on the studied criteria, products maintained constant and adequate quality by up to 10 days while stored in 4 °C. In the case of all tested samples, the overall sensory quality began to deteriorate after 10 days of storage. The preservative role of herbs and extracts in meat products during processing and storage was observed. Oregano and black pepper in both forms maintained good microbial quality and showed their inhibitory effects on the growth of psychrotrophic bacteria. It was observed that dried herbs revealed a stronger antioxidant effect than additives in the form of extracts. The studied dried herbs played an antioxidant, antimicrobial and preservative role in meat products during processing and storage.

LISTERIA MONOCYTOGENES IN COW’S MILK PRODUCED BY FAMILY-OWNED DAIRY FARMS

Refrigeration is an important milk preservation method. However, milk quality may deteriorate if the product is refrigerated for long periods, mainly due to the growth of psychrotrophic bacteria. This group of microorganisms includes pathogenic genera, most notably Listeria monocytogenes. The detection of this bacterium in food is important, given its pathogenic effects on human and animal health and also its economic relevance. This study focused on detecting the presence of L. monocytogenes in milk samples collected at small family-owned dairy farms. Samples were cultivated on PALCAM and ALOA agars for microbiological analysis and a molecular analysis by polymerase chain reaction was performed for the detection of L. monocytogenes. Despite the negative results obtained in both these analyses, further studies are recommended to confirm or refute the negligible effect of L. monocytogenes on small dairy farms.

Effect of Gelatin Coated Rosemary Extract (Rosmarinus Officinalis L.) on the Quality of Refrigerated Duck Meat

The effect of edible coating of gelatin (1, 2 and 3%) containing aqueous extract of rosemary (1% and 2%) on physiochemical (pH, total volatile nitrogen, peroxide values and water holding capacity) and microbiological (psychrotrophic) properties of duck fillet were evaluated. The pH of coated samples were significantly (plessthan0.05) lower than that of untreated sample. TVN (total volatile nitrogen) value increased with storage period in all the samples but coatings significantly decreased production of TVN compared to the control. Also the coatings decreased lipid oxidation of the meat as rosemary postponed primary oxidation of fillet, while this parameter in control group was sharply increased by time. WHC (water holding capacity) increased significantly (plessthan0.05) with storage period and level coatings. Coating had a significant reducing effect on growth of psychrotrophic bacteria during 9 days at 4°C. In conclusion, gelatin edible coating enriched with rosemary could retard chemical and microbial reactions related to spoilage of meat during refrigerated storage.

Extraction of bioactive compounds of lemongrass, antioxidant activity and evaluation of antimicrobial activity in fresh chicken sausage

ABSTRACT: The aim of this work was to determine the best extraction condition of bioactive compounds from lemongrass (Cymbopogon citratus), using the conventional method and ultrasonic assisted extraction, varying the temperature, in order to evaluate the antioxidant activity and the antimicrobial activity of the extract with higher antioxidant power in fresh chicken sausages during the storage period. The extracts were obtained by the conventional method (solvent extraction) and by ultrasound assisted extraction, varying the temperature (20°C, 40°C and 60°C). Phenolic compounds, total flavonoids and antioxidant activity were measured by the DPPH, FRAP, ORAC methods. Conventional extraction and ultrasound methods influenced the phenolic and total flavonoid content at all tested temperatures. Conventional and ultrasonic methods did not influence the IC50 at temperatures of 40°C and 60°C. The antioxidant activity by the DPPH method and by the FRAP method was superior in the conventional method at the temperature of 60°C, however by the ORAC method the best results were in the extraction by ultrasound. The results demonstrate that the conventional extraction at 60ºC was better to obtain extracts of lemongrass with greater amount of bioactive compounds. The antimicrobial capacity evaluated in sausage of fresh chicken showed that in the concentration of 1.0% of the extract protected the product as the growth of mesophilic aerobes and against the growth of psychrotrophic bacteria. Lemongrass can be considered as a natural alternative to obtain extracts rich in bioactive compounds, with antioxidant activity and high antimicrobial capacity.

Culture-independent bacterial community profiling of carbon dioxide treated raw milk

Due to technical simplicity and strong inhibition against the growth of psychrotrophic bacteria in milk, CO2 treatment has emerged as an attractive processing aid to increase the storage time of raw milk before downstream processing. However, it is yet to be adopted by the industry. In order to further explore the suitability of CO2 treatment for raw milk processing, the bacterial populations of carbonated raw milk collected locally from five different sources in Australia were analysed with next-generation sequencing. Growth inhibition by CO2 was confirmed, with spoilage delayed by at least 7days compared with non-carbonated controls. All non-carbonated controls were spoiled by Gammaproteobacteria, namely Pseudomonas fluorescens group bacteria, Serratia and Erwinia. Two out of the five carbonated samples shared the same spoilage bacteria as their corresponding controls. The rest of the three carbonated samples were spoiled by the lactic acid bacterium (LAB) Leuconostoc. This is consistent with higher tolerance of LAB towards CO2 and selection of LAB in meat products stored in CO2-enriched modified atmosphere packaging. No harmful bacteria were found to be selected by CO2. LAB are generally regarded as safe (GRAS), thus the selection for Leuconostoc by CO2 in some of the samples poses no safety concern. In addition, we have confirmed previous findings that 454 pyrosequencing and Illumina sequencing of 16S rRNA gene amplicons from the same sample yield highly similar results. This supports comparison of results obtained with the two different sequencing platforms, which may be necessary considering the imminent discontinuation of 454 pyrosequencing.

Sodium metasilicate affects growth of Campylobacter jejuni in fresh, boneless, uncooked chicken breast fillets stored at 4 degrees Celsius for 7 days ,

The objectives of this study were to determine the antimicrobial effects of sodium metasilicate (SMS) treatments against Campylobacter jejuni in fresh, boneless, uncooked chicken breast fillets and to ascertain the effects of SMS treatments on pH. The fillets were inoculated with C. jejuni, treated with 0% SMS and no inoculum (negative control), 0% SMS and inoculum (positive control), 1 and 2% SMS solutions, and stored at 4 ± 1°C. All samples were analyzed after 0, 1, 3, 5, and 7 d storage for C. jejuni, psychrotrophic organisms, and pH. Campylobacter jejuni and psychrotrophic counts for samples treated with 1 and 2% SMS solutions were similar (P > 0.05) to the positive control on all storage days. The pH values for 2% SMS marinade treatments were higher (P < 0.05) when compared with the negative and positive controls through 7 d of storage. Based on the findings in this study, a second study was conducted to determine the level of SMS necessary to reduce C. jejuni by at least 1 log cfu/g. The treatments were the same as previously discussed, except SMS was used at levels of 1 and 2% of the weight of the meat instead of percentage of the solution. Chicken fillets treated with 1 and 2% SMS (by weight of meat) resulted in 1.12 to 1.26 and 3.27 to 3.79 log cfu/g reductions in C. jejuni, respectively, when compared with the positive control. Except for d 0, psychrotrophic counts for samples treated with 2% SMS were lower (P < 0.05) than negative and positive controls on all storage days. The pH values were higher (P < 0.05) for all SMS treatments when compared with the negative and positive controls. This study revealed that SMS, when used at elevated levels in excess of the USDA Food Safety and Inspection Service 2% approved level, could function to control Campylobacter jejuni and extend the shelf life of raw poultry by retarding the growth of psychrotrophic bacteria.

Stabilisation of colour and odour of beef patties by using lycopene‐rich tomato and peppers as a source of antioxidants

AbstractBeef patties containing natural antioxidants—cayenne hot pepper, red sweet pepper, lycopene‐rich tomato pulp (LRTP) and extract of tomato rich in lycopene (Lyc‐O‐Mato™)—and packaged in modified atmosphere were evaluated for storage stability at 2 ± 1 °C by measuring CIE a* values, surface metmyoglobin, TBARS, psychrotrophic bacteria counts and sensory off‐odour and discolouration. Results demonstrated that the addition of ground peppers (both sweet and hot) to beef patties delayed and inhibited very significantly (p &lt; 0.05) the oxidation of both myoglobin and lipid as well as the growth of psychrotrophic bacteria. As a consequence, and according to instrumental and sensory results of meat colour and odour, the shelf life of beef patties was extended from about 4 to about 16 days. Capsaicinoid‐rich cayenne hot pepper exerted a more intense antioxidative effect than capsaicinoid‐free red sweet pepper. The addition of lycopene‐enriched tomato products (LOM and LRTP) was not as effective as treatment with peppers, although they exerted a significant (p &lt; 0.05) antioxidative effect too, depending on the lycopene concentration. These tomato products delayed meat deterioration to a varying extent, so that the shelf life of treated beef patties ranged between 8 and 12 days.© 2003 Society of Chemical Industry

Effect of Superatmospheric Oxygen Packaging on Sensorial Quality, Spoilage, and Listeria monocytogenes and Aeromonas caviae Growth in Fresh Processed Mixed Salads

Atmospheres with O2 levels higher than 70 kPa have recently been suggested as an innovation to modified atmosphere packaging (MAP) for fresh processed vegetables to maintain sensory quality and safety. In the present work, mixed vegetable salad collected from a commercial processing plant and stored with the MAP technique was studied. Two gas mixtures were actively generated by using an initial O2 concentration of 95 kPa and combined with two plastic films. The low-barrier film permeability for O2 was 1,629 mlO2/m2 × 24 h × atm with 30μm of thickness (Hyplast, Hoogstraten, Belgium) and the O2 permeability of the high-barrier film was 2 mlO2/m2 × 24h × atm with 150μm of thickness (Euralpack, Wommelgen, Belgium) at 23°C. As control, active conventional MAP with application of 3 to 5 kPa of O2 and 6 to 8 kPa of CO2 was used. Packaged salads were stored up to 8 days at 4°C and at temperatures simulating chilled distribution chain conditions. Microbial safety and sensory quality, as well as the survival of inoculated Listeria monocytogenes and Aeromonas caviae, were monitored. The effect of superatmospheric O2 on the growth of aerobic microflora was variable. Under superatmospheric conditions, lactic acid bacteria and members of Enterobacteriaceae were inhibited. Nevertheless, growth of yeast and A. caviae seem to be stimulated by superatmospheric O2, whereas growth of psychrotrophic bacteria and L. monocytogenes was not affected. The overall visual appearance (mainly color) of the mixed vegetable salads was better maintained and the shelf life prolonged when packaged under O2 concentrations greater than 50 kPa.

Plasmin Levels in Fresh Milk Whey and Commercial Whey Protein Products

Growth of psychrotrophic bacteria in nonfat dry milk at refrigeration temperatures was shown previously in our laboratory to cause a shift in plasmin (a native milk protease) from the casein to the whey fraction. The whey fraction from cheesemaking is commonly used to make whey protein concentrates and isolates, which then are used as functional ingredients in various food systems. Plasmin activity in whey protein products may cause breakdown of food proteins to have desirable or undesirable effects on food quality. This raised questions about the level of plasmin in commercial whey protein products and factors that affect this plasmin level. Therefore, the objectives of this study were to determine: 1) plasmin concentrations in sweet and acid whey protein products as influenced by Pseudomonas growth during storage of fresh milk, and 2) plasmin concentrations in commercial whey protein products.Whey type (sweet or acid) had a significantly (P<0.05) greater effect on whey-associated plasmin activity than did Pseudomonas fluorescens M 3/6 growth. Acid whey protein products had significantly (P <0.05) higher plasmin concentrations than sweet whey. Plasmin activities associated with acid and sweet whey protein products were both significantly (P<0.0001) affected by the growth of Pseudomonas fluorescens M 3/6. The interaction effect between bacterial growth and whey type on plasmin activity was not significant (P = 0.2457). Plasmin activity in the reconstituted commercial whey protein concentrates (i.e., sweet and acid) varied considerably (16.3 to 330μg/g of protein), but was significantly lower (2.1 to 4.4μg/g of protein, P<0.05) in whey isolates. These quantitative data were supported by plasmin activity visualized by casein SDS-PAGE.

Microbiological Quality and the Inability of Proteolytic Clostridium botulinum To Produce Toxin in Film-Packaged Fresh-Cut Cabbage and Lettuce

The production of toxin by a 10-strain mixture of proteolytic Clostridium botulinum in fresh produce packaged in polyethylene films having high (7,000 cc/m2/24 h; HOTR) and low (3,000 cc/m2/24 h; LOTR) relative oxygen permeability was determined. Shredded cabbage and lettuce inoculated with ~102 spores/g were placed in bags composed of the two films (1.4 kg/bag), and the bags were then vacuum sealed. Produce was stored at 4, 13, and 21°C for up to 21 (cabbage) or 28 (lettuce) days and analyzed periodically. At each sampling time, the gas composition within the bags, pH of the produce, and microbial populations (total aerobic and anaerobic microorganisms, lactic acid bacteria, psychrotrophic bacteria, and yeasts and molds) were determined. In addition, the presence of botulinal toxin was determined using the standard U.S. Food and Drug Administration mouse bioassay protocol. Bags made of HOTR film prolonged sensory quality of cabbage and lettuce, especially at 13 and 4°C. Packaging material had an effect on the growth of various groups of microorganisms; however, there was not a general trend. For example, lettuce packaged in HOTR bags had higher aerobic microbial populations than that packed in LOTR, but no significant difference (P ≤ 0.05) was observed with cabbage. Growth of psychrotrophic bacteria was greater in vegetables packaged in HOTR film while growth of yeasts and molds was not affected by either packaging film. Most differences in microbial populations in produce packaged in LOTR and HOTR films were less than 1 log10 CFU/g. Botulinal toxin was not detected in cabbage or lettuce packaged in either film or stored under any test condition.

Vitamin Stability and Growth of Psychrotrophic Bacteria in Refrigerated Raw Milk Acidified with Carbon Dioxide

The effect of the application of CO2 for extending the storage life of raw cow's milk on the retention of some vitamins—all-trans-retinol, 13-cis-retinol, β-carotene, α tocopherol, γ tocopherol, thiamin and riboflavin—and on the growth of psychrotrophic spoilage bacteria has been studied. Raw cow's milk samples were acidified by bubbling CO2 through them to pH 6.0 and 6.4. Two different controls were used: untreated milk (pH 6.83) and degasified milk (pH 6.85). The treated samples as well as the controls were stored at 7°C for 7 days and analyzed daily for the fat-soluble vitamins and growth of psychrotrophic bacteria. Thiamin and riboflavin were analyzed only at the beginning and the end of the period studied (days 0 and 7). No significant variations (P ≤ 0.05) of the content of all-trans-retinol, beta-carotene, α and γ tocopherol and riboflavin were observed in all samples studied. In contrast, during the first 4 days 13-cis-retinol doubled from the initial content. A slight decrease of thiamin was observed at the end of the storage period. These variations were observed in the treated samples as well as in the controls, so it can be assumed that the treatments studied for preservation of milk did not cause changes in vitamin retention during cold storage. Psychrotrophic counts were inhibited significantly (P ≤ 0.05) by the presence of CO2 after 2 to 3 days of storage, and no significant differences (P ≤ 0.05) were found between samples acidified to pH 6.0 and 6.4.

Stability of Sliced Mozzarella Cheese in Modified-Atmosphere Packaging

Twelve slices of mozzarella cheese (about 174 g) were packaged in expanded polystyrene trays placed in gas-barrier bags under three different atmospheres (100% N2, 100% CO2, and 50% CO2/50% N2). A gas headspace-to-cheese ratio of 2.5 liters/kg of cheese was initially set in the modified-atmosphere packages. Simulating conventional Brazilian packaging, some trays were wrapped in PVC stretched film. Periodically, the product stored at 7 ± 1°C was evaluated as to its sensorial quality, microbiological condition, and physical and chemical characteristics. The head-space volume and gas composition of modified-atmosphere packages were evaluated, The mozzarella cheese did not show any physical or chemical alteration in all packaging treatments. These characteristics were not factors which limited shelf life in air or in modified atmospheres. The critical parameter was sensory degradation. The shelf life of sliced mozzarella in conventional air pack was 13 days. N2 atmospheres had only a minor effect on shelf life compared with air. Samples under N2 were satisfactory up to 16 days. A significant shelf life increase was verified under CO2 atmospheres compared with air, as follows: 63 days (a 385% increase) and 45 days (a 246% increase) for product under 100% CO2 and 50% CO2/50% N2, respectively. The bacteriostatic and fungistatic effects of CO2 were verified. The growth of psychrotrophic bacteria, molds, and yeasts was slower under CO2 atmospheres. Mold and yeast development was inhibited under 100% CO2 (2 liters of CO2 per kg of cheese).

Efficacy of a lactic acid/sodium benzoate wash solution in reducing bacterial contamination of raw chicken

Raw chicken wings inoculated with Salmonella, Campylobacter jejuni, Listeria monocytogenes, Staphylococcus aureus, or Escherichia coli O157:H7 were washed in water (control) or a solution of a 0.5% lactic acid/0.05% sodium benzoate (LB) (pH 2.64) for 30 min. Viable cells of pathogenic bacteria and naturally occurring psychrotrophic bacteria on wings were enumerated after 0, 2, 4, 6, and 8 days of storage at 4 °C. Lower populations of pathogenic and psychrotrophic bacteria were detected on wings immediately after washing with LB compared to populations detected on control wings. LB solution was more effective in killing Salmonella, C. jejuni, and E. coli O157:H7 than L. monocytogenes, and S. aureus. During refrigerated storage, populations of Salmonella, C. jejuni, L. monocytogenes, and E. coli O157:H7 decreased significantly on LB-washed wings, as compared to populations of respective pathogens on control wings. The growth of psychrotrophic bacteria on LB-washed wings was significantly retarded as compared to growth on control wings during refrigerated storage. Washing chicken wings with a solution containing 0.5% lactic acid and 0.05% sodium benzoate can greatly reduce the populations of pathogenic and psychotrophic bacteria, thus enhancing safety and extending shelf life.

Rennet - Clotting Properties and Starter Activity on Milk Acidified with Carbon Dioxide

The influence of acidification with CO2 on starter activity, rennet clotting properties, and cheese yield have been studied. Results obtained with lactic acid-treated milk were compared with those obtained with CO2-treated milks. CO2-treated samples showed lower acidification by starter than lactic acid-treated samples. The higher final pH values found in CO2-treated samples could be attributed to reduced starter metabolic activity. Heat treatments to 60 or 70°C for 30 min did not influence coagulation time by rennet. Acidification produced a decrease of coagulation time, which was more pronounced on samples treated with lactic acid. Cheese yield was influenced by the growth of psychrotrophic bacteria during storage of milk.

Growth of Psychrotrophic Bacteria in Solids Fortified Skim Milk

The effect of fortifying skim milk with non-fat dried milk on growth and proteolysis of psychrotrophic bacteria was determined. Raw skim milk of 8.7% total solids was fortified to 10% and 12% total solids and pasteurized. Growth rates of proteolytic psychrotrophic bacteria were determined in these milks during incubation at 4°C. Proteolysis was determined by measuring the concentration of free amino groups throughout the incubation period. Seven of nine psychrotrophic isolates grew to greater numbers in the fortified milks during the early log phase of growth than they did in the unfortified milks. Growth stimulation was slight in most cases, however, one isolate exhibited a ten-fold increase in numbers when growing in the 10% solids fortified milk. The greatest increases in growth were observed when comparing unfortified milk to milk at 10% solids. Early log phase growth in 12% solids milk was often less than in 10% solids milk but still greater than in unfortified milk. All isolates exhibited increased proteolysis in the fortified milks within 48 h of incubation. These results indicate that increasing the solids content of skim milk with non-fat milk powder produces a microbiological growth medium more suitable for growth and protease production for selected psychrotrophic bacteria.

Growth of psychrotrophic bacteria in raw and UHT‐treated goats'milk

The growth of six strains of Pseudomonas fluorescens, two of Ps. fragi, and one of Serratia liquefaciens was followed in raw and UHT-treated goats' milk, held at 4 degrees C. Generation times for Ps. fluorescens in UHT milk ranged from 5.19 to 5.81 h, increasing markedly in raw milk (8.34-21.49 h). Growth of Ps. fragi did not differ significantly between raw (4.56, 4.65 h) and UHT (5.04, 7.24 h) milk. Generation times for S. liquefaciens were 6.63 and 14.07 h, for UHT and raw milk respectively.

Changes in Size of Casein Micelles Caused by Growth of Psychrotrophic Bacteria in Raw Skim Milk

Raw skim milk was inoculated (1%, v/v) with a proteolytic psychrotrophic bacterium that previously was isolated from milk. The inoculated skim milk was incubated at 7°C for 0, 3, 5 and 7 d. The pH values for the milk were 6.6, 6.5, 6.45 and 5.95, and the numbers of psychrotrophs/ml were 1.0 × 104 8.9 × 107, 9.0 × 108 and 2.5 × 108 for days 0, 3, 5 and 7, respectively. Samples of milk were negatively stained, examined with transmission electron microscopy and distribution of sizes of casein micelles was determined. The average and (mode) sizes of micelles were 849 (789), 1030 (634), 761 (634) and 405 (316) Angstroms for milks after days 0, 3, 5 and 7, respectively. Another set of samples was prepared from skim milk immediately after it was acidified to pH values of 6.6, 6.5, 6.45 and 5.95. The average and (mode) sizes of micelles were 891 (766), 875 (615), 913 (766) and 840 (615) Angstroms for milks having pH values of 6.6, 6.5, 6.45 and 5.95, respectively. Changes in size of micelles in the incubated samples resulted from bacterial activity other than small changes in pH.

Inhibition of Psychrotrophic Bacteria in Refrigerated Milk by Lactobacilli Isolated from Yogurt

A “milk-peroxidase” agar was prepared to select cultures of lactobacilli that most actively produce hydrogen peroxide. O-tolidine and peroxidase contained in the medium reacted with hydrogen peroxide produced by the bacteria to form a colored zone around the colonies during their formation on the agar at 37 C. There appeared to be no relationship between the size of zones surrounding the colonies on the agar medium and the amount of peroxide produced in milk at 5.5 C. Cells from frozen concentrated cultures of selected lactobacilli were added to milk to achieve desired populations in the interaction experiments. A significant inhibition of a psychrotrophic culture in autoclaved milk at 5.5 C occurred when at least 2.5 × 107 lactobacilli were added per ml. Larger numbers of lactobacilli resulted in greater inhibition of the psychrotroph. The intensity of inhibition of a psychrotrophic culture in autoclaved milk varied among the cultures of lactobacilli tested. In most instances, the more active inhibitory cultures produced more peroxide in refrigerated milk than less inhibitory ones. In preliminary experiments, a culture of Lactobacillus bulgaricus selected by the above procedure produced no inhibitory effect against the growth of psychrotrophic bacteria in non-agitated raw milk at 5.5 C.

Influence of Retail Display Temperature on Psychrotrophic Bacterial Growth and Beef Case-Life

Laboratory-simulated retail conditions were employed to examine the effects of retail display temperature upon growth of psychrotrophic bacteria and the retail case-life of rib-eye steaks. The temperature of continuously displayed steaks ranged from 7.5 to 14.2 C and under these conditions an average case-life of 2.4 days was determined. However, when steaks were limited in their time of retail display, by overnight refrigeration in a walk-in cooler (1 C), steak temperatures were reduced to 1 C and retail case-life substantially extended to 4.9 days. Increased retail case-life resulted from a reduction in psychrotrophic bacterial growth which was related to the rate of deterioration of steak retail appearance. These findings provide an alternative to the continuous retail display of beef which, if applied, could greatly improve beef case-life and reduce spoilage losses.