EFFECT OF ELECTRICAL STIMULATION ON KILLING SALMONELLA TYPHIMURIUM IN VARIOUS SALT SOLUTIONS

Electrical stimulation was evaluated as a method to kill Salmonella typhimurium in various salt solutions at different concentration . Salmonella typhimurium at 2 × 10⁵ CFU/ml was treated at 22–24C for 60 min in each salt solution using electricity at 10 mA/cm² current, 1 kHz frequency, and 50% duty cycle. Samples taken at various times were serially diluted, plated on tryptic soy agar and xylose lysine desoxycholate agar, and incubated at 37C for 18–24 h. To detect injured cells, samples were also pre-enriched in buffered peptone water at 37C for 4–5h before being plated. Results indicated all salmonellae were electrically killed at 5 min in NaCl, at 30 min in NaNO₃, and at 45 min in NaC₂H₃O₂ at 0.15 and 0.015 M concentrations. Salmonellae were also killed at 45 min in Na₃PO₄ and at 60 min in Na₂CO₃ at 0.0015 M concentration by electricity in combination with high pH .     

Development of a Model System to Mimic Beef Bone Discoloration

ABSTRACT: Some current practices used in the meat industry (blast chilling, enhancement, modified atmosphere packaging [MAP]) appear to result in darkening of the bone in fresh meat. The objective of this study was to develop a model system that could be used to evaluate intervention strategies to prevent this discoloration. Beef rib bones were removed from carcasses, split along the transverse plane from the proximal to the distal end of the rib, and then frozen (−20 °C) or held at 4 °C for 24 h. Half were exposed to a phosphate/salt enhancement solution while half served as the control. Samples were packaged in air or modified atmosphere packaged (MAP: 80% O₂/20% CO₂) and displayed in a retail case (4 °C, 24 h). Visual discoloration occurred during the 1st 10 h of display. More darkening (brown, green/black) was observed in previously frozen samples, whereas samples held at refrigeration temperature were redder. CIE L *, a *, and b * values determined after 24 h indicated that samples held in refrigeration before packaging were lighter and redder. After 24 h at 4 °C, previously frozen samples contained more methemoglobin/g protein in the bone marrow than did bone samples that had never been frozen.     

The effect of carbon dioxide gas alone or in combinations on the mortality of Tribolium castaneum (Herbst) and T. confusum du Val (Coleoptera, Tenebrionidae)

Adults of Tribolium castaneum (Herbst) and T. confusum du Val exposed to various mixtures of N₂ or He and O₂ were killed when the O₂ concentration reached to 1·7% or below, whereas the adults exposed to CO₂ : O₂ mixtures were killed mostly due to the deleterious effects of CO₂ itself. At 26·7°C and 38 ± 6%r.h., 95 per cent mortality of T. confusum adults was obtained by an exposure of 271 hr to 45% CO₂ : 55% air mixture; 58 hr to 62% CO₂ : 38% air mixture; and 47·5 hr to 80% CO₂ : 20% air mixture, while for T. castaneum adults 95 per cent mortality required 192, 60, and 44 hr respectively. Data obtained by exposing mature and immature stages of both species to 100% CO₂ suggest that adults were the most susceptible, followed by larvae, eggs and pupae. Generally speaking, inactive stages (egg and pupal) were more tolerant to CO₂ than active stages (larval and adult). Increasing the temperature from 15·6° to 26·7°C resulted in increased insect mortalities; the degree of response varying in different stages. Increasing r.h. decreased the susceptibility of adult insects to 100% CO₂.

Under airtight conditions 200 adult T. castaneum with 8 g of food medium sealed in 1·2 1. glass flasks depleted the O₂ supply from 20·9% to a critical 1·7% level in 7 days, and adults of T. confusum depleted to the 1·6% level in 5 days of airtightness, and both species produced about 20% of carbon dioxide gas.     

QUANTITATIVE DETERMINATION OF METMYOGLOBIN AND TOTAL PIGMENT IN AN INTACT MEAT SAMPLE USING REFLECTANCE SPECTROPHOTOMETRY

SUMMARY— A technique for determining the relative quantities of oxymyoglobin, metmyoglobin and total pigment concentration at the surface of on intact meat sample was developed. A Beck-man DK-2 spectrophotometer with reflectance attachment was used and spectra were recorded on the R_A scale. The sample port of the spectrophotometer was modified so that a uniform and high intensity light beam measuring 0.5 × 0.6 cm reached the surface being evaluated. A sample holder was constructed so that known proportions of oxygenated and oxidized meat could be exposed to the light beam. A family of curves representing varying known amounts of metmyoglobin and oxymyoglobin were obtained. The height of the peak at 632 nm (ΔR_A632) was directly related to the amount of metmyoglobin at the surface of the meat sample. For 100% oxymyoglobin, ΔR_A632 was at a minimum and equal to R_A750. For 100% metmyoglobin, ΔR_A632 was at a maximum and the height of the response depended upon the amount of total pigment present. A linear relation was obtained when ΔR_A362 was plotted against percent metmyoglobin or against total pigment determined by the Hornsey (1956) method. The method requires making two readings of the meat samples at a single wave length. One reading of the sample followed by one reading of the same sample after oxidation with K₃ Fe(CN)₆ provides a quantitative evaluation of the metmyoglobin concentration and the total heme pigment concentration. The accuracy of the method may be improved by making multiple readings.     

THE EFFECT OF SODIUM POLYPHOSPHATES AND OF DIVALENT CATIONS ON THE WATER HOLDING CAPACITY OF PRE-AND POST-RIGOR CHICKEN BREAST MUSCLE

The water holding capacity (WHC) of natural actomyosin (NAM), of both contracted and uncontracted glycerinated myofibrils and of pre- and post-rigor chicken meat was investigated in the presence and/or absence of sodium pyrophosphate (PP_i), Kena, CaCl₂ and MgCl₂. In these experiments PP_i caused a small decrease in the WHC of NAM which was further decreased either by Ca or even further by Mg. PP_i with or without Ca or Mg had almost no effect on the WHC of glycerinated myofibrils. Pre-rigor meat showed a slight decrease in WHC of PP_i which was further decreased with Mg or even further by Ca. With post-rigor meat the WHC increase with PP_i was decreased by the addition of Mg or even further decreased by the addition of Ca. The actual WHC of pre-rigor meat was almost twice that of post-rigor meat. Once rigor had occurred no major changes in WHC were observed up to 5 days. Kena caused a slight decrease in the WHC of NAM. Using myofibrils and the meat samples, Kena gave an increase in WHC. The addition of Ca and Mg again tended to decrease this WHC.     

Effect of irradiation and modified atmosphere packaging on the microbiological safety of minced pork stored under temperature abuse conditions

The safety of irradiated pork packed in 25% CO₂:75% N₂ and stored at abuse temperature (10 or 15°C) was assessed by inoculation studies involving Salmonella typhimurium, Listeria monocytogenes, Escherichia coli, Yersinia enterocolitica and Clostridium perfringens . Irradiation to a dose of 1.75 kGy reduced pathogen numbers to below the detection limit of 10² cells g^-1. When higher inoculum levels were used (10⁶ cells g^-1) irradiation at 1.75 kGy reduced pathogen numbers by 1 –>5 log₁₀ cycles depending on strain. Clostridium perfringens was the most resistant, and Y. enterocolitica the most sensitive of the pathogens studied.
In all cases when high numbers (10⁶ to 10⁷g^-1) of spoilage and/or pathogenic bacteria were present initially on the pork the meat appeared spoiled, and although irradiation reduced the number of microorganisms, the meat was still unacceptable from a sensory viewpoint after treatment.
It was concluded that the microbiological safety of irradiated, modified atmosphere packaged (MAP) pork is better than that of unirradiated MAP pork.     

Combined effects of thymol, carvacrol and grapefruit seed extract on lipid oxidation and colour stability of poultry meat preparations

The combined effects of thymol, carvacrol and grapefruit seed extract (GFSE) on lipid oxidation and colour stability of poultry meat preparations packaged in air or modified atmospheres (MAP: 5% O₂; 30% CO₂; 65% N₂) were investigated using a simplex centroid mixture design. Lipid oxidation was evaluated through measurement of secondary oxidation products (malonaldehyde, MDA) and general appearance with visual assessment and instrumental measurement of colour. Thymol and carvacrol, as individual antioxidants, retarded the oxidation process by maintaining MDA values below 2 mg kg⁻¹ meat. The effect of GFSE was less than thymol and carvacrol. Redness ( a* ) decreased in all treatments during storage but this reduction was more evident in the control and in samples containing GFSE than in thymol and carvacrol. Although colour acceptability decreased with time, all meat preparations packaged in air maintained desirable appearance better than samples in MAP. Also, off-odours developed faster in the samples packaged in MAP than in aerobically packaged samples.     

THE USE OF CO2 IN PACKAGING OF FRESH RED MEATS AND ITS EFFECT ON CHEMICAL QUALITY CHANGES IN THE MEAT: A REVIEW

The antimicrobial effect of carbon dioxide (CO₂) is well documented but comparison of the large number of often contradictory studies investigating the effect of CO₂ on chemical quality changes is lacking. The amount of absorbed CO₂ varies from 0 - 1.79 L CO₂/kg meat depending on the applied packaging and storage conditions, which clearly demonstrates the necessity of optimizing these conditions with respect to the required amount of CO₂. Absorption of large amounts of CO₂ in meat tissue can cause a minor decrease in pH due to the dissociation of the produced carbonic acid to bicarbonate and hydrogen ions. A decrease in pH might affect other chemical quality parameters but this is not observed to be the case in the reviewed studies and general detrimental effects of CO₂ cannot be found for color, weight loss or lipid oxidation. However, elevated CO₂ levels can cause pore formation in cooked meat.     

Postmortem Calcium Chloride Injection Alters Ultrastructure and Improves Tenderness of Mature Chinese Yellow Cattle Longissimus Muscle

ABSTRACT: This study was conducted to test the hypothesis that postmortem calcium injection could activate the calpain system in mature Chinese Yellow Cattle muscle, thereby promoting meat tenderization through disruption of the myofibril structure during aging. A 10% (w/w) injection of CaCl₂ (300 m M ) solution lowered the Warner-Bratzler shear values of longissimus muscle by more than 30% ( P < 0.05), even with only 24 h postmortem storage when compared with noninjected or water-injected controls. The accelerated meat tenderization by the Ca²⁺ treatment paralleled the changes in myofibril fragmentation index and fracture of the myofibril ultrastructure throughout the sarcomere but most notably around the I-bands and the Z-disks. Injection of ZnCl₂ (50 m M ) largely inhibited these proteolytic changes. The colorimetric L * and a * values were not affected by CaCl₂ nor by ZnCl₂ injection. The results suggest that postmortem CaCl₂ injection can be used to help resolve the toughness problem of mature Chinese Yellow Cattle meat and shorten the aging time required to achieve adequate tenderness.     

CALCIUM CHLORIDE EFFECTS ON TBA VALUES OF COOKED MEAT

Ground chicken breast and beef top round (semimembranosus) muscles were treated with CaCl₂ (0.05, 0.10, 0.15, and 0.20% on final sample weight basis) and cooked to an internal temperature of 80C. Cooked samples were aerobically stored at 4C for 0 or 4 days and analyzed for 2-thiobarbituric acid (TBA)-reactive substances. Results indicated that CaCl₂ can either inhibit or accelerate lipid oxidation in cooked meat depending on its concentration/meat animal species. TBA values of chicken samples were decreased by CaCl₂ used at ≥ 0.1% of final weight. However, only beef samples treated with the highest CaCl₂ level (0.20%) tended to have lower TBA values when compared to control samples (treated with deionized water only). CaCl₂ used at low levels (0.05% for chicken and ≤0.15% for beef) tended to elevate cooked meat TBA values.     

Effect of irradiation and modified atmosphere packaging on the microbiological and sensory quality of pork stored at refrigeration temperatures

The effect of combining low-dose irradiation (1.75 kGy) with modified atmosphere packaging (MAP) on the microbiological and sensory quality of pork chops stored at refrigeration temperatures was studied. The microflora of irradiated MAP pork was almost exclusively composed of lactic acid bacteria, predominantly Lactobacillus spp. Modified atmospheres containing either 25 or 50% CO₂, balance N₂, resulted in the best microbial control in irradiated pork held at 4°C, compared to an unirradiated MAP control, and these atmospheres were subsequently used in sensory studies. The atmosphere containing 25% CO₂ 75% N₂ maintained the uncooked colour and odour of irradiated pork chops more effectively than 50% CO₂ 50% N₂. Therefore packaging in a modified atmosphere containing 25% CO₂, balance N₂, followed by irradiation to a dose of 1.75 kGy is recommended to improve the microbiological and sensory quality of pork chops.     

INFLUENCE OF MODIFIED ATMOSPHERE PACKAGING ON GROWTH OF CLOSTRIDIUM PERFRINGENS IN COOKED TURKEY

Clostridium perfringens containing samples of sterile ground turkey were studied to assess growth under modified atmosphere conditions. Samples were packaged under various atmospheres (CO₂/O₂/N₂: 75/5/20, 75/10/15, 75/20/5, 25/20/55, 50/20/30), stored at 4, 15 and 28C, and sampled periodically for growth. Diluted samples were plated on Shahidi Ferguson perfringens agar (Difco Laboratories, Detroit, MI) to determine vegetative cell counts. Temperature abuse (cyclic and static) of the turkey product was also investigated. The results showed that the growth of C. perfringens was slowest under 25–50% CO₂/20% O₂/balance N₂ at 15 and 28C. There was no growth at 4C for up to 28 days. Temperature abuse (28C storage) of refrigerated products for 8 h did not permit C. perfringens growth. Use of 25–50% CO₂/20% O₂/balance N₂ may extend the shelf-life of turkey, but in the absence of proper refrigeration, it cannot be relied upon to eliminate the risk of C. perfringens food poisoning .     

Ozone treatment of chilled beef

Summary. The initial specific rate of ozone decomposition by muscle was 1.02 ± 0.23 m/hr, for tissue stored at 0.3°C and equilibrium relative humidities (EH) of 99.3, 98.5 or 98.0% in air with ozone concentrations between 0.15 and 38.3 mg/m³, or in air-ozone mixtures containing 11% CO₂. the value was not affected by the presence or absence on the muscle surface of meat spoilage bacteria, yeasts or moulds but considerably lower values were obtained for lean and high fat surface tissues (0.44 and 0.31, respectively).
The slope α of the linear course of the logarithm of reaction velocity-time curves was a power function α= - 9.74 10^-4[O₃]^1.54 for ozone concentrations [O₃] 5 mg/m³. the slope was not significantly different from zero when muscle of EH 98.5% was exposed to 0.7 mg/m³ ozone, but significant values were determined when muscle had an EH of 98.0, and also when tissue (EH 99.3%) was exposed to ozone concentrations > 0.7 mg/m³. Values of α determined for surface tissue and muscle tissue were not significantly different when the same treatment was applied.     

Improved shelf life of protein-rich tofu using Ocimum sanctum (tulsi) extracts to benefit Indian rural population

ABSTRACT:  A nutrition survey carried out in India revealed that the diets of the rural population are inadequate and deficient in most of the nutrients especially protein. India being the 5th-largest producer of soybean, a protein-rich cereal, can redress protein-energy malnutrition through diversification of soybean uses by developing high-value and health-based food products. Tofu, a nonfermented soybean product rich in high-quality protein, B-vitamins, and isoflavones, could be an excellent substitute for meat in Indian recipes. Tofu being rich in protein has a very short shelf life. Hence an attempt was made to improve the shelf life using extracts of tulsi ( Ocimum sanctum ) commonly available in rural areas. Tofu was prepared traditionally using MgCl₂:CaSO₄ as coagulating agents. Aqueous extract of Ocimum sanctum (tulsi) was added during the preparation and storage of tofu to prolong its shelf life. Water used in this study was free from microflora, plant extract used contained mesophilic count of 2.527 × 10⁴ CFU/g, and no yeasts and molds were detected. Tofu with tulsi extract had 76.4% moisture and was softer than control. Not much difference in mesophilic count was observed between control and treated samples during storage; however, treated tofu was organoleptically good until the end of the study with less lipid-peroxidation and exhibited 50% (4.7 units) less protease activity than control (9.6 units) after 7 d. By using extracts of naturally available, easily cultivable tulsi, the shelf life was successfully extended to 7 to 8 d from 3 to 4 d of normal storage without refrigeration.     

ON THE INTERACTION OF MYOGLOBIN AND HEMOGLOBIN WITH MOLECULAR OXYGEN AND ITS LOWER OXIDATION STATES AND WITH CYTOCHROMEc

Ferrimyoglobin and ferrihemoglobin are oxidized to the ferry1 (+4) state by the xanthine-xanthine oxidase system under the same conditions under which the system causes rapid reduction of ferricytochrome c. Catalytic amounts of ferrimyoglobin exert an apparent inhibition of ferricytochrome c reduction by the system. Oxidation of ferrimyoglobin and ferrihemoglobin is most likely due to their reacting with products of xanthine oxidase reduction of oxygen, O⁻₂ (HO₂) and/or H₂O₂. The apparent inhibition of ferricytochrome c reduction is direct (interception of O⁻₂ by ferrimyoglobin) and/or indirect (reoxidation of ferrocytochrome c by ferrylmyoglobin). The latter mechanism is supported by spectral evidence of one-equivalent redox reactions (intermolecular electron transfers) between ferrylmyoglobin and ferrocytochrome c and between ferromyoglobin and ferricytochrome c. Both electron transfers have favorable redox potentials and therefore would be expected to occur from that standpoint. During autoxidation of oxymyoglobin O⁻₂ dissociation was not detected. This is consistent with theoretical arguments which indicate that O⁻₂ cannot dissociate during autoxidation although the conjugate acid (HO₂) can. If so, this would at least partially explain the known decrease in stability of the oxyheme complex as the pH of fresh red meat, meat extracts or oxyhemoprotein solutions is lowered. Mechanisms of autoxidation that are consistent with known pH and oxygen partial pressure effects and chemical reactions, as well as with available quantitative data and pertinent theoretical arguments are discussed.     

Respiration of Tribolium castaneum (Herbst) at reduced oxygen concentrations

Adults, eggs, young and old larvae and pupae of Tribolium castaneum (Herbst) were exposed to atmospheres containing 1%, 2%, 3%, 5%, 10%, and 15% oxygen in nitrogen at 30°C and 70% r.h. Respiration rates were determined with a gas chromatograph. The oxygen intake and carbon dioxide output by insects were expressed in μl/insect/h or μl/mg/h.

Adults exposed to 21% oxygen required an initial acclimatization period of at least 5 h, after which the respiration rate remained stable. Based on this finding, all the respiration measurements were carried out after an initial adaptation of insects to the respirometer conditions for 24 h.

Respiration of eggs, young and old larvae, pupae, and adults at 30°C in normal atmospheric air was at rates of 0.0121, 9.25, 8.45, 1.45, and 4.67 μl CO₂/insect/h, respectively. Respiration rates of the same stages in terms of insect weight were 0.32, 29.08, 3.33, 0.59 and 2.37 μl CO₂/mg insect/h, respectively. At reduced oxygen levels respiration rates of eggs, larvae and pupae were proportional to the oxygen levels. Adult respiration was higher for 3% and 5% oxygen than for normal atmospheric air with rates of 4.77 and 4.98 μl CO₂/insect/h, respectively. In adults, RQ values for the same oxygen levels were also higher than for normal atmospheric oxygen and were 1.07 and 1.18, respectively.     

Synthesis of acetals and esters of propargyl,propenyl and propyl alcohols and the bioassay of these and related compounds as fumigants against Anastrepha suspensa (Loew) larvae

The synthesis of 36 compounds, acetals, ketals, esters or ethers of acetylenic, olefinic and aliphatic alcohols is described. These and 26 related compounds were tested as fumigants against Anastrepha suspensa (Loew) larvae. Twenty-three compounds showed fumigant activity. 3-Butyne-2-one killed all the larvae exposed at the rate 2.2 mg/1 for 3 h, as did the reference fumigant ethylene dibromide (EDB). Six compounds killed 100% of the larvae exposed to them at the rate of 2.2 mg/l for 24 h. Eight compounds, including propargyl alcohol, propargyl methacrylate and propargyl 3-methylcrotonate, did not kill A. svspensa larvae until a few days after exposure during which time the larvae apparently grew normally and underwent pre-pupariation wanderlust in synchrony with untreated larvae.     

Impact of nitrite on detection of Listeria monocytogenes in selected ready-to-eat (RTE) meat and seafood products

ABSTRACT:  The impact of sodium nitrite (NaNO₂) on detection and recovery of Listeria monocytogenes from select ready-to-eat (RTE) foods including smoked salmon, smoked ham, beef frankfurters, and beef bologna was assessed. Nitrite-containing (NC; 100 to 200 ppm NaNO₂) or nitrite-free (NF) foods were inoculated with a 5-strain cocktail of L. monocytogenes by immersion into Butterfield's buffer solution containing 5.4 to 7.4 × 10³ L. monocytogenes per milliliter. Inoculated products were vacuum-packaged and stored at 5 °C. A weekly comparative analysis was performed for presence of L. monocytogenes using 5 detection methods on products held at 5 °C for up to 8 wk. L. monocytogenes initially present at <100 CFU/g during the first 2 wk of storage increased throughout the study, attaining final populations of approximately 1 × 10⁴ to 1 × 10⁵ CFU/g. Lactic acid bacteria predominated throughout the study in all products. Exposure to NaNO₂ (100 to 200 ppm) resulted in 83% to 99% injury to the L. monocytogenes strains tested. The genetic-based BAX^® System (DuPont™ Qualicon, Wilmington, Del., U.S.A.) and modified USDA/FSIS methods detected 98% to 100% of Listeria -positive food samples and were consistently superior to and significantly different ( P < 0.05) from conventional cultural methods in recovering Listeria from NC samples. Data show that nitrite-induced injury adversely affects detection and recovery of L. monocytogenes from NC food, confirming earlier findings that nitrite-induced injury masks L. monocytogenes detection in NC RTE food products. Nitrite-injured Listeria can subsequently repair upon nitrite depletion and grow to high levels over extended refrigerated storage.     

Loss of Fuminosin B1 in Extruded and Baked Corn-Based Foods with Sugars

The objective of this work was to determine the effect of added sugars on fumonisin B₁ (FB₁) levels in baked corn muffins and extruded corn grits. Muffins containing added glucose had significantly lower FB₁ levels than muffins with sucrose, fructose, or no added sugar. Extrusion cooking of the grits resulted in significant (p< 0.05) reductions of FB₁ in all treatments relative to unextruded controls, but use of glucose resulted in greater reductions of FB₁ (45.3 to 71%) than did the use of fructose (29.5 to 53%) or sucrose (19.2 to 39%). When extrusion conditions were optimized, 92.1% loss of FB₁ was found when grits were extruded with glucose. Adding glucose to thermally processed food can result in a substantial reduction in FB₁ levels.     

EFFECT OF WATER ACTIVITY ON THE GROWTH OF STAPHYLOCOCCUS AUREUS AT MEAT-CHEESE INTERFACES

There is increased marketing of ready-to-eat nonrefrigerated snack foods which consist of meat or sausage products with low or intermediate moisture levels combined with high moisture food products, i.e., cheese products. Packaging the intermediate moisture meat in direct contact with a high moisture food might change the water activity (a_w) of the products sufficiently to support growth of Staphylococcus aureus at contaminated interfaces. To evaluate this possibility, sterile sausage slices (a_w= 0.60 to 0.82) were surface inoculated with log 2-3 CFU/g of S. aureus, interfaced with processed cheese slices (a_w= 0.94), vacuum packaged, and incubated at 19, 28, 37C and at cyclic temperature of 19–37–19C. S. aureus levels and water activities were determined weekly for 0 to 9 weeks. The a_w at the interface changed rapidly and reached an a_w that supported S. aureus growth. Growth of S. aureus occurred under all test conditions when the samples were stored at 28 and 37C. At 19C storage S. aureus remained viable for the length of the study.