Effect of washing with citric acid and antioxidants on the colour and microbiological quality of whole mushrooms (Agaricus bisporus L.)

The effect of washing with citric acid followed by anti‐browning treatment involving rinsing with sodium d ‐isoascorbate or sodium l ‐ascorbate on the colour, microbiological quality and bacterial blotch of whole mushrooms when stored at 5 °C for up to 13 days at 80% RH was evaluated. Washing with 1% citric acid reduced Pseudomonas counts avoiding bacterial blotch, but caused an important deterioration of colour. When washing with citric acid was followed by an anti‐browning treatment, mushrooms colour was improved, at the same time as bacterial blotch was reduced, although the decrease of Pseudomonas counts was smaller than in mushrooms washed only with citric acid. The most effective treatment was washing with 1% citric acid followed by anti‐browning treatment with 1.5% sodium l ‐ascorbate.     

Effect of processing and storage conditions on the microbiological quality of minimally processed vegetables

The microbiological contamination of minimally processed vegetables was measured before and after processing and at different times and storage temperatures (5 and 10 days at 4 and 20 °C). To evaluate the efficacy of the overall process the water used for washing and rinsing the vegetables during the various phases of the operation were also examined. Thanks to the high quality of the vegetables at origin, simple chlorine treatment was sufficient to achieve a satisfactory reduction in coliforms, Escherichia coli, coliphages and saprophytic flora, thus ensuring that all of the freshly packed samples conformed to reference standards and guidelines. This conformity was maintained when the storage instructions indicated on the package (4 °C for 5 days) were followed. However, the persistence of faecal indicators after treatment suggested a potential risk of infection that could increase if the original contamination was higher. Microbiological examination of the water used for preliminary washing and for rinsing was seen to be useful in the assessment of the safety of the vegetables, at origin and after processing. The advantage of choosing coliphages for such monitoring is that they are indicators of viral contamination that can be measured rapidly. Critical points to be checked during the process are the levels of residual chlorine remaining in the washing tanks and the storage temperatures.     

Identification of critical control points for control of microbiological contamination in processes leading to the production of ground beef at a packing plant

Carcasses, carcass portions and pieces of manufacturing beef were sampled by swabbing a 100 cm² randomly selected site on each of 25 randomly selected product units at each of several stages of the meat production processes at a large beef packing plant. After skinning, aerobes were recovered from each sample, at log mean numbers of 1.86 log cfu cm⁻²; and coliforms and Escherichia coli were recovered from <15 of 25 samples at log total numbers of 3.27 and 3.16 log cfu 2500 cm⁻². The numbers of bacteria recovered after preevisceration washing and spraying with 2% lactic acid solution were similar to the numbers recovered after skinning, and the numbers recovered from carcasses that had been eviscerated, split, vacuum/hot-water cleaned and trimmed were little different. However, the numbers of coliforms and E. coli were reduced by the washing of carcass sides; and pasteurizing followed by spraying with lactic acid reduced the numbers of aerobes to log mean numbers of 0.71 log cfu cm⁻² and coliforms and E. coli to log total numbers of 1.28 and 0.30 log cfu 2500 cm⁻², respectively. After cooling for 24 h, numbers of aerobes on carcass sides had increased to log mean numbers of 2.57 log cfu cm⁻², and log total numbers of coliforms and E. coli had increased to 3.34 and 2.18 log cfu 2500 cm⁻², respectively. Numbers had not increased after sides had been held for a further 12 h before breaking. Numbers of bacteria on forequarters increased during breaking operations on hanging sides and increased further after forequarters were dropped to conveyor belts. Numbers on hindquarters were little affected by those operations. Large numbers of bacteria were recovered from cleaned equipment that contacted forequarters. The numbers of bacteria on trimmings did not increase during conveying from breaking lines to bulk containers. The numbers of bacteria on manufacturing beef were less than the numbers on forequarters trimmings, but more than the numbers on hindquarters trimmings. The log mean numbers of bacteria in ground beef produced at the plant were 3.11 log cfu g⁻¹, and the log total numbers of coliforms and E. coli were 1.84 and 1.30 log cfu 25 g⁻¹, respectively. Similar numbers of bacteria were recovered from ground samples of manufacturing beef. It therefore appears that most of the E. coli as well as other bacteria in ground beef are deposited on the product during the initial operations for breaking forequarters. Thus, improvement of equipment cleaning rather than of production processes would be required to improve the microbiological condition of ground beef prepared at the plant. However, skinning, washing of dressed sides, pasteurizing and cooling are evidently critical control points in carcass production processes.     

Heat resistance of Escherichia coli O157:H7 in cook‐in‐bag ground beef as affected by pH and acidulant†

Summary The heat resistance of a four‐strain mixture of Escherichia coli O157:H7 was tested. The temperature range was 55–62.5 °C and the substrate was beef at pH 4.5 or 5.5, adjusted with either acetic or lactic acid. Inoculated meat, packaged in bags, was completely immersed in a circulating water bath and cooked to an internal temperature of 55, 58, 60, or 62.5 °C in 1 h, and then held for pre‐determined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic soy agar overlaid with Sorbitol MacConkey agar. Regardless of the acidulant used to modify the pH, the D ‐values at all temperatures were significantly lower (P < 0.05) in ground beef at pH 4.5 as compared with the beef at pH 5.5. At the same pH levels, acetic acid rendered E. coli O157:H7 more sensitive to the lethal effect of heat. The analysis of covariance showed evidence of a significant acidulant and pH interaction on the slopes of the survivor curves at 55 °C. Based on the thermal‐death–time values, contaminated ground beef (pH 5.5/lactic acid) should be heated to an internal temperature of 55 °C for at least 116.3 min and beef (pH 4.5/acetic acid) for 64.8 min to achieve a 4‐log reduction of the pathogen. The heating time at 62.5 °C, to achieve the same level of reduction, was 4.4 and 2.6 min, respectively. Thermal‐death–time values from this study will assist the retail food processors in designing acceptance limits on critical control points that ensure safety of beef originally contaminated with E. coli O157:H7.     

Heat resistance in Escherichia coli and its implications on ground beef cooking recommendations in Canada

This study assessed the adequacy of the current cooking recommendations in relation to heat resistant Escherichia coli by evaluating eight potentially heat resistant E. coli strains (four generic and four E. coli O157:H7) along with AW1.7. The D_60°C-values for these strains varied from 1.3 to 9.0 min, with J3 and AW1.7 being the least and most heat resistant strains, respectively. The D_60°C-values for E. coli 62 and 68 were similar and were not affected by growth medium, while the heat resistance of C37, J3, and AW1.7 varied with the growth medium. When heated in extra lean ground beef (100 g) in vacuum pouches, the mean D_54°C, D_57°C, and D_60°C-values were 44.8, 18.6, and 2.9 min for C37, 13.8, 6.9, and 0.9 min for J3, and 40.5, 9.1, and 6.1 min for AW1.7. Burger temperatures continued to rise after being removed from heat when the target temperature was reached, by 3–5°C, and resting of 1 min would result in a destruction of 133, 374 and 14 log C37, J3 and AW1.7. These findings along with the very low occurrence of heat resistant E. coli expected in ground beef show that cooking ground beef to 71°C should be adequate.     

Survival of Escherichia coli O157:H7 in Apple Cider as Affected by Dimethyl Dicarbonate, Sodium Bisulfite, and Sodium Benzoate

Survival of Escherichia coli O157:H7 in apple cider containing no preservatives, 0.025% dimethyl dicarbonate (DMDC), 0.045% sodium benzoate (SB), 0.0046% sodium bisulfite (NaS; 65.5% sulfur dioxide), or a combination of NaS and SB (NaS/SB) and stored at 4, 10, and 25°C was evaluated. E. coli O157:H7 survived for up to 18 days at 4,10, and 25°C in unpreserved apple cider. At 4 and 10°C, DMDC was most efficient at inactivating E. coli O157:H7, generally followed by NaS/SB SB, and NaS (p<0.05). E coli O157:H7 was more resistant to preservatives at 4°C than at 25°C (P < 0.05). E. coli O157:H7 was sublethally injured in cider containing preservatives, and to a lesser extent, in unpreserved cider. Generally, injury was more pronounced in cider containing DMDC, followed by NaS/SB, SB, and NaS (p<0.05).     

Application of electron‐beam irradiation pasteurization of ground beef,from steers fed vitamin E fortified diets: microbial and chemical effects

The effects of vitamin E supplementation of diets and electron‐beam irradiation (EBI) processing of ground beef patties on microbial and chemical qualities were investigated during 21 days of storage at 4 °C. Oxidative damage to lipids induced by EBI in ground beef patties containing different fat contents was first determined at 3 day intervals throughout a 7 day storage period at 4 °C. Significantly (P ≤ 0.05) higher values for thiobarbituric acid reactive substances (TBARS) were detected in beef patties of higher fat content (ie at 17 and 30%), which was further enhanced by irradiation at 5 kGy. Since lipid oxidation proceeded to a greater extent in beef patties with higher fat levels, ground beef patties of 30% fat were prepared from steers fed basal (diet I) or basal + 500 IU (diet II) of the antioxidant (vitamin E) supplemented diets. Plasma vitamin E concentrations in cattle fed diets I and II were 1.58 ± 0.42 µg ml^?1 and 2.49 ± 0.40 µg ml^?1 respectively. Patties were processed with three doses (2, 5, or 10 kGy) of EBI and compared with non‐irradiated patties. Microbial indices monitored at 3 day intervals included total aerobic plate count, psychrotrophic counts, and total coliform and Escherichia coli counts. Bacterial growth in ground beef patties stored at 4 °C was significantly (P ≤ 0.05) reduced by EBI at 2 kGy dose. Complete inhibition of bacteria occurred at 5 kGy or higher (P ≤ 0.05) dosage of EBI over 21 days of storage at 4 °C. Quality indices monitored at 3 day intervals throughout a 21 day storage (4 °C) study involving 30% fat ground beef patties made from steers fed vitamin E supplemented diets I and II included TBARS and colour. Results indicated that irradiation at the highest dosages was associated with higher (P ≤ 0.05) TBARS values, which in turn corresponded to lower linoleic acid content. With all three levels of irradiation, Hunter a values of beef patties decreased (P ≤ 0.05) significantly. Lipid oxidation was significantly (P ≤ 0.05) retarded in stored beef patties derived from cattle fed vitamin E (diet II). Copyright © 2003 Society of Chemical Industry     

Growth patterns of Escherichia coli O157:H7 in ground beef treated with nisin,chelators, organic acids and their combinations immobilized in calcium alginate gels

The effects of antimicrobial substances including nisin, acetic acid, lactic acid, potassium sorbate and chelators (disodium ethylenediamine tetraacetic acid [EDTA] and sodium hexametaphosphate [HMP]), alone or in combination and, with or without immobilization in calcium alginate gels, on the growth of Escherichia coli O157:H7 in ground beef were investigated. Results showed that acetic acid and potassium sorbate could inhibit the growth of E. coli O157:H7 effectively at 10°C and at 30°C. Both EDTA and HMP did not halt the growth of E. coli O157:H7. In an antimicrobial system immobilized with calcium alginate, most of the antimicrobials could not inhibit the growth of E. coli O157:H7 in ground beef at 10°C and at 30°C, with the exception of acetic acid and lactic acid. Immobilization did not enhance the effectiveness of acetic acid against E. coli O157:H7 in ground beef at 10°C and at 30°C (P>0.05) but it did enhance the effectiveness of lactic acid at 10°C. In a system combining different antimicrobials, treatment with nisin /EDTA or nisin/potassium sorbate at 10°C revealed a significantly lower population change of E. coli O157:H7 compared to samples treated with nisin, EDTA or potassium sorbate alone. The use of calcium alginate immobilization further enhanced the effectiveness of the combination system of nisin/EDTA, nisin/acetic acid and nisin/potassium sorbate on the growth of E. coli O157:H7 in ground beef at 10°C but it was not effective at 30°C.     

Acidified sodium chlorite optimisation assessment to improve quality of fresh-cut tatsoi baby leaves

BACKGROUND: The fresh‐cut industry commonly uses sodium hypochlorite (NaClO) for disinfection. However, there are certain problems related to its use, and acidified sodium chlorite (ASC) could be an alternative sanitiser to replace it. There is limited research evaluating the effect of ASC on the overall quality of fresh‐cut produce, especially sensory quality. In this study the decontamination efficacy and quality attribute effects of ASC on fresh‐cut tatsoi after application and during storage were investigated. RESULTS: Tatsoi baby leaves were minimally processed at 8 °C and stored under passive modified atmosphere packaging for up to 11 days at 5 and 10 °C. Low to moderate doses of ASC (100–500 mg L^?1) showed an initial antimicrobial efficacy on natural microflora and Escherichia coli as effective as that of NaClO. Regarding contact time, ASC was effective in reducting the E. coli population during the first 30 s of washing, and an increase in contact time did not improve the antimicrobial effect. Sensory quality attributes were well kept for up to 11 days at 5 °C but for only 5 days at the abusive temperature of 10 °C. CONCLUSION: ASC provides an alternative sanitising technique to NaClO for maintaining the quality and safety of fresh‐cut tatsoi baby leaves for up to 11 days at 5 °C. Copyright © 2011 Society of Chemical Industry     

Microbial populations on animal hides and beef carcasses at different stages of slaughter in plants employing multiple-sequential interventions for decontamination

Multiple-sequential interventions were applied commercially to reduce beef carcass contamination in eight packing plants. The study evaluated microbial populations on animal hides and changes in carcass microbial populations at various stages in the slaughtering process. Sponge swab samples yielded mean (log CFU/100 cm2) total plate counts (TPC), total coliform counts (TCC), and Escherichia coli counts (ECC) on the exterior hide in the ranges of 8.2 to 12.5, 6.0 to 7.9, and 5.5 to 7.5, respectively, while corresponding contamination levels on carcass surfaces, after hide removal but before application of any decontamination intervention, were in the ranges of 6.1 to 9.1, 3.0 to 6.0, and 2.6 to 5.3, respectively. Following the slaughtering process and application of multiple-sequential decontamination interventions that included steam vacuuming, pre-evisceration carcass washing, pre-evisceration organic acid solution rinsing, hot water carcass washing, postevisceration final carcass washing, and postevisceration organic acid solution rinsing, mean TPC, TCC, and ECC on carcass surfaces were 3.8 to 7.1, 1.5 to 3.7, and 1.0 to 3.0, respectively, while corresponding populations following a 24 to 36 h chilling period were 2.3 to 5.3, 0.9 to 1.3, and 0.9, respectively. The results support the concept of using sequential decontamination processes in beef packing plants as a means of improving the microbiological quality of beef carcasses.     

Evaluation of 54° and 60°C Holding Temperatures on Aerobic Plate Counts and Coliform Determinations of Control and Post Cooking Contaminated Beef Roast

Fabricated beef roasts were cooked to an internal temperature of 60°C and the surface inoculated with a suspension of Escherichia coli at a level of lo⁶ cells/cm². Roasts were then stored in a warming oven at 54° and 60°C for 1, 2, 6, and 12 hr. Under these conditions the destruction of this strain of E. coli is quite rapid (less than 6 hr) at the 60°C holding temperature. The holding temperatures do allow the growth of thermoduric organisms naturally present in the product to initiate exponential growth after 6 hr at 54°C. The higher holding temperature reduced the rate of multiplication of the thermoduric organisms.     

Growth of Escherichia coli and Salmonella typhimurium on Beef Tissue at 25°C

At 25°C, growth of Escherichia coli and Salmonella typhimurium on beef was influenced by type of tissue, pH, gaseous atmosphere, and physiological state of the cells used to inoculate the tissue. These organisms grew after only a short lag period, both aerobically and anaerobically, on beef fatty-tissue, and on high pH muscle (pH ≥ 6). The lag period was considerably extended on low pH muscle (pH ≤ 5.7) incubated aerobically. On low pH lean tissue stored anaerobically at 25°C for 24 hr, cells from aerobically grown broth cultures did not grow whereas cells from anaerobically grown cultures grew after an extended lag. These results suggest that during the cooling of hot-boned meat growth of E. coli and salmonellae is more likely on fatty tissue or muscle of high pH than on lean tissue of low pH.     

Reduction of Pathogens Using Hot Water and Lactic Acid on Beef Trimmings

Beef trimmings from young or mature beef cattle were obtained commercially. Trimmings within age type then were inoculated with about 6.0 log₁₀ CFU/mL of rifampicin-resistant. Escherichia coli O157:H7 and Salmonella typhimurium (ATCC 13311) were randomly assigned to 1 of 3 treatments (control; 95 °C hot water alone, or with 2% L-lactic acid). After treatment, trimmings were ground, held for 0, 14, 28, or 42 d in chub packages at 4 °C, and total aerobic plat counts, E. coli O157:H7, and S. typhimurium counts were determined. Non-inoculated trimmings were also treated and samples were evaluated for pH, fat, moisture, TBA, meat color by colorimeter, and meat color, and odor by trained sensory panels. Trimmings treated with water or hot water plus lactic acid reduced levels of E. coli O157:H7 and S. typhimurium and tended to be darker after treatment. Meat odor in the final product was not affected by treatment.     

Survival of Listeria monocytogenes, Yersinia enterocolitica and Escherichia coli O157:H7 and Quality Changes After Irradiation of Beef Steaks and Ground Beef

Beef steaks and ground beef were inoculated with Listeria monocytogenes, Yersinia enterocolitica, or Escherichia coli O157:H7. Samples were packaged in air or under vacuum and irradiated at low (0.60 to 0.80 kGy) or medium (1.5 to 2.0 kGy) doses, with each dose delivered at either a low (2.8 M/min conveyor speed) or high (6.9 M/min) dose rate. Medium-dose irradiation accompanied by 7°C storage resulted in no Y. enterocolitica or E. coli O157:H7 survivors being detected. There was no effect on survival of the pathogens by dose rate or storage atmosphere. No difference (P>0.05) was observed in meat pH or color, but TBA values increased after 7 days storage.     

Comparison of Decontamination Efficacy of Antimicrobial Treatments for Beef Trimmings against Escherichia coli O157:H7 and 6 Non-O157 Shiga Toxin-Producing E. coli Serogroups

Abstract: The decontamination efficacy of 6 chemical treatments for beef trimmings were evaluated against Escherichia coli O157:H7 and 6 non‐O157 Shiga toxin‐producing E. coli (nSTEC) serogroups. Rifampicin‐resistant 4‐strain mixtures of E. coli O157:H7 and nSTEC serogroups O26, O45, O103, O111, O121, and O145 were separately inoculated (3 to 4 log CFU/cm²) onto trimmings (10 × 5 × 1 cm; approximately 100 g) fabricated from beef chuck rolls, and were immersed for 30 s in solutions of acidified sodium chlorite (0.1%, pH 2.5), peroxyacetic acid (0.02%, pH 3.8), sodium metasilicate (4%, pH 12.5), Bromitize^® Plus (0.0225% active bromine, pH 6.6), or AFTEC 3000 (pH 1.2), or for 5 s in SYNTRx 3300 (pH 1.0). Each antimicrobial was tested independently together with an untreated control. Results showed that all tested decontamination treatments were similarly effective against the 6 nSTEC serogroups as they were against E. coli O157:H7. Irrespective of pathogen inoculum, treatment of beef trimmings with acidified sodium chlorite, peroxyacetic acid, or sodium metasilicate effectively (P < 0.05) reduced initial pathogen counts (3.4 to 3.9 log CFU/cm²) by 0.7 to 1.0, 0.6 to 1.0, and 1.3 to 1.5 log CFU/cm², respectively. Reductions of pathogen counts (3.1 to 3.2 log CFU/cm²) by Bromitize Plus, AFTEC 3000, and SYNTRx 3300 were 0.1 to 0.4 log CFU/cm², depending on treatment. Findings of this study should be useful to regulatory authorities and the meat industry as they consider nSTEC contamination in beef trimmings. Practical Applications: Findings of this study should be useful to: (i) meat processors as they design and conduct studies to validate the efficacy of antimicrobial treatments to control pathogen contamination on fresh beef products; and (ii) regulatory agencies as they consider approaches for better control of the studied pathogens.     

Recovery of heat-stressed E. coli O157:H7 from ground beef and survival of E. coli O157:H7 in refrigerated and frozen ground beef and in fermented sausage kept at 7°C and 22°C

A study was undertaken to obtain information on survival of Escherichia coli O157:H7 in ground beef subjected to heat treatment, refrigeration and freezing and on survival of E. coli O157:H7 in fermented sausage kept at 7°C and 22°C. For the challenge test, a mixture of E. coli O157:H7 strains (EH 321, EH 385, EH 302) was used and enumeration was performed on an isolation medium suitable for recovery of stressed organisms: modified Levine's eosin methylene blue agar (mEMB). Heat resistance of E. coli O157:H7 decreased after pre-incubation at a reduced temperature.Escherichia coli O157:H7 was more susceptible to heat inactivation after storage at 7°C and die-off was even more enhanced if cultures were frozen prior to heat inactivation. The enhanced reduction of the pathogen at 56°C after prior storage under refrigeration was confirmed in a test with inoculated ground beef.Escherichia coli O157:H7 was able to survive in ground beef at 7°C for 11 days and at −18°C for 35 days showing maximal one log reduction during the storage period. Thus, ground beef contaminated with E. coli O157:H7 will remain a hazard even if the ground beef is held at low or freezing temperatures. At both 7°C and 22°C, a gradual reduction of E. coli O157:H7 was noticed in fermented sausage over the 35 days storage period resulting in a 2 log decrease of the high inoculum (10⁶cfu 25 g⁻¹). For the low inoculum (10³cfu 25 g⁻¹) a 2·5 log reduction was obtained in 7 and 28 days storage at respectively 22 and 7°C. Application of good hygienic practices and implementation of HACCP in the beef industry are important tools in the control of E. coli O157:H7.     

Neutral electrolyzed water (NEW), chlorine dioxide,organic acid based product,and ultraviolet‐C for inactivation of microbes in fresh‐cut vegetable washing waters

The effect of decontamination methods on fresh‐cut vegetable washing waters was evaluated. NEW, ClO₂, organic acid‐based product FPW, and UV‐C were tested with and without an interfering carrot juice of 1% (IS), on Yersinia enterocolitica and Yersinia pseudotuberculosis, Escherichia coli, and yeast Candida lambica. The use of ClO₂ (50 ppm active chlorine) resulted in >4 log reduction of Y. enterocolitica, Y. pseudotuberculosis, E. coli and >3 log reduction of C. lambica. The antibacterial effect of NEW was less effective in the presence of IS when compared with ClO_2. The inactivation of C. lambica by FPW reached a maximum of 2.8 log cfu/mL (concentration 0.125%), but the antimicrobial effect was delayed by the IS. The effect of FPW on E. coli was significantly reduced by 1% IS. The inactivation of E. coli and C. lambica with UV‐C IS decreased the inactivation and lengthened its time. Filtration improved the effect of UV‐C inactivation.

Practical applications

When chemical decontamination methods were used in fresh‐cut vegetable processing, the presence of organic matter in process water increased the reaction times and the need for higher concentrations of the chemical decontamination and the time of physical decontamination. Yersinia required longer inactivation times than E. coli. When UV‐C is used for decontamination of process waters, waters should be filtered to enhance the disinfection efficacy.     

Evaluation of Brining Ingredients and Antimicrobials for Effects on Thermal Destruction of Escherichia coli O157:H7 in a Meat Model System

ABSTRACT: Escherichia coli O157:H7 may become internalized during brine injection of meat. This study evaluated the effect of brining ingredients on E. coli O157:H7 in a meat model system after simulated brining, storage, and cooking. Fresh knuckles (5.3 ± 2.4% fat) or beef shoulder (15.3 ± 2.2% fat) were ground individually, mixed with an 8-strain composite of rifampicin-resistant E. coli O157:H7 (7 log CFU/g) and brining solutions. Treatments included no brining, distilled water, sodium chloride (NaCl, 0.5%), sodium tripolyphosphate (STP, 0.25%), sodium pyrophosphate (SPP, 0.25%), NaCl + STP, NaCl + SPP, NaCl + STP + potassium lactate (PL, 2%), NaCl + STP + sodium diacetate (SD, 0.15%), NaCl + STP + PL + SD, NaCl + STP + lactic acid (0.3%), NaCl + STP + acetic acid (0.3%), NaCl + STP + citric acid (0.3%), NaCl + STP + EDTA (20 mM) + nisin (0.0015%) or pediocin (1000 AU/g), NaCl + STP + sodium metasilicate (0.2%), NaCl + STP + cetylpyridinium chloride (CPC; 0.5%), and NaCl + STP + hops beta acids (0.00055%). Samples (30 g) were analyzed for pH, and total microbial and rifampicin-resistant E. coli O157:H7 (inoculum) populations immediately after mixing, storage (24 h at 4 °C), and cooking to 65 °C. Fat and moisture contents and water activity were measured after storage and cooking only; cooking losses also were determined. The effect of beef type on microbial counts, pH, and water activity was negligible. No reductions in microbial counts were obtained by the brining solutions immediately or after storage, except for samples treated with CPC, which reduced (P < 0.05) pathogen counts after storage by approximately 1 log cycle. Cooking reduced pathogen counts by 1.5 to 2.5 logs, while CPC-treated samples had the lowest (P < 0.05) counts compared to any other treatment. These data may be useful in developing/improving brining recipes for control of E. coli O157:H7 in moisture-enhanced beef products.     

Physiology and Microbiological Quality of Fresh-cut Mango Cubes as Affected by High-O2 Controlled Atmospheres

Preliminary study showed that among 40‐ to 100‐kPa O₂ atmospheres, 60‐kPa O₂ reduced the respiration of fresh‐cut ‘Carabao’ mango cubes the most when held at 5 °C or 13 °C for 42 h. Therefore, the effects of 60‐kPa O₂ on the physiology and microbial quality of fresh‐cut ‘Carabao’ and ‘Nam Dokmai’ mango cubes were determined and compared with those held in air. The high‐O₂ atmosphere reduced the respiration rate of ‘Carabao’ mango cubes stored at 5 °C but stimulated the rate after 2 d of storage at 13 °C. Browning of ‘Carabao’ cubes was accelerated by 60‐kPa O₂ at 13 °C. With ‘Nam Dokmai’ cubes, the high O₂ had no effect on respiration rate, browning, and incidence of water‐soaked appearance at 5 °C and 13 °C. The high O₂ did not affect texture or ascorbic acid content of ‘Carabao’ and ‘Nam Dokmai’ mango cubes at either temperature. Counts of lactic acid bacteria and molds were below the detection level (2.4 log colony‐forming units [CFU]/g) during storage at both temperatures. However, 60‐kPa O₂ stimulated the growth of mesophilic aerobic bacteria on ‘Carabao’ cubes and yeasts of ‘Nam Dokmai’ cubes at 13 °C. The increased microbial count may have been due to the higher pH of cubes stored in 60‐kPa O₂ at 13 °C than at 5 °C or in air. Within ‘Nam Dokmai’ mango cubes, the predominant genera in mesophilic aerobic bacteria were Enterobacter, Klebsiella, and Pantoea and in the yeasts were Candida, Cryptococcus, and Rhodotorula. These results indicate that 60‐kPa O₂ is not desirable for mango cubes when held at 13 °C.     

Mechanically Deboned Pork Use in Fermented Meat Spreads

Proportions (25, 50 and 100%, w/w) of mechanically deboned pork (MDP) were evaluated for use in spreads fermented with Pediococcus pentosauceus or chemically acidified. Microbiological stability was examined at 2–4, 5, 8–10, and 24° C, with or without inoculated Staphylococcus aureus. Microbiological, color, texture, pH, TBA, and proximate composition were studied in relation to product formulation and processing. Fat retention and product spreadability were attained by combining up to 50% MDP, preemulsified with soy protein isolate (SPI) or sodium caseinate (SC), with pork and beef trimming preblended with NaCl and phosphate. These were fermented with Pendiococcus pentosauceus (40° C and 85% RH, 18 h). Potato starch (2%) was added and product was comminuted postfermentation. Unlike formulations with SPI, those containing SC exhibited good microbiological stability, with no Enterobacteriaceae, and S. aureus decreased.