Microwave Oven Heating for Inactivation of Listeria Monocytogenes on Frankfurters before Consumption

ABSTRACT:  Microwave oven heating was evaluated for inactivation of  Listeria monocytogenes  on inoculated and stored frankfurters. Frankfurters formulated without/with 1.5% potassium lactate and 0.1% sodium diacetate were inoculated with  L. monocytogenes  (1.9 ± 0.2 log CFU/cm²), vacuum-packaged, and stored (4 °C) to simulate conditions prior to purchase by consumers. At storage days 18, 36, and 54, packages were opened and placed at 7 °C, simulating aerobic storage in a household refrigerator. At 0, 3, and 7 d of aerobic storage, 2 frankfurters were placed in a bowl with water (250 mL) and treated in a household microwave oven at high (1100 W) power for 30, 45, 60, or 75 s, or medium (550 W) power for 60 or 75 s. Frankfurters and the heating water were analyzed for total microbial counts and  L. monocytogenes  populations. Exposure to high power for 75 s reduced pathogen levels (0.7 ± 0.0 to 1.0 ± 0.1 log CFU/cm²) to below the detection limit (<−0.4 log CFU/cm²) on frankfurters with lactate/diacetate, even after 54 d of vacuum-packaged storage followed by 7 d of aerobic storage. For frankfurters without lactate/diacetate, high power for 75 s caused reductions between > 1.5 and 5.9 log CFU/cm² from control levels of 1.5 ± 0.1 to 7.2 ± 0.5 log CFU/cm². Depending on treatment and storage time, the water used to reheat the frankfurters had viable  L. monocytogenes  counts of <−2.4 to 5.5 ± 0.5 log CFU/mL. The results indicated that frankfurters should be reheated in a microwave oven at high power for 75 s to inactivate up to 3.7 log CFU/cm² of  L. monocytogenes  contamination.     

超高压处理对法兰克福香肠中主要微生物的影响及其变化规律

为探讨超高压处理对真空包装法兰克福香肠微生物货架期的影响,在(20±5)℃对真空包装法兰克福香肠进行200MPa(5min与10min)、400MPa(5min与10min)和600MPa(5min与10min)的超高压处理。样品处理后于4℃保藏60d,每隔10d取样分析,直至样品微生物数量达到峰值并趋于稳定为止。与空白对照组(不进行二次灭菌的法兰克福香肠)相比,超高压处理能显著降低法兰克福香肠初始微生物数量,并对保藏过程中的腐败微生物:嗜冷菌、乳酸菌和大肠菌群的生长有显著抑制作用,抑制程度与压力(200～600MPa)和处理时间(5～10min)具有正相关性。效果最佳的600MPa处理10min能够将法兰克福香肠4℃贮藏货架期从9d延长至60d以上。     

Inactivation of Listeria innocua on frankfurters that contain potassium lactate and sodium diacetate by flash pasteurization

ABSTRACT:  Listeria monocytogenes , a psychrotrophic foodborne pathogen, is a recurring postprocess contaminant on ready-to-eat meat (RTE) products, including frankfurters. Potassium lactate (PL) and sodium diacetate (SDA) are FDA-approved antimicrobials that inhibit the growth of L. monocytogenes when incorporated into the formulation of fine emulsion sausage. Flash (steam) pasteurization (FP) has been shown to reduce levels of L. monocytogenes , and its surrogate L. innocua , on frankfurter surfaces. The ability of FP to inactivate and prevent the growth of the L. monocytogenes surrogate L. innocua in a pilot plant setting was investigated. FP treatment (1.5 s, 121 °C) of single layers of frankfurters that were surface-inoculated with either 5, 4, or 3 log CFU/g of L. innocua immediately before FP (1.5 s, 121 °C) resulted in log reductions of 1.97 (± 0.11), 2.03 (± 0.10), or 2.07 (± 0.14), respectively. Inoculum level had no effect on the inactivation of L. innocua . Following 8 wk of refrigerated storage (4 °C), L. innocua levels decreased by 0.5 log in non-FP-treated frankfurter packs, while the 2 log reduction of L. innocua was maintained for FP-treated frankfurters. FP (1.5 s, 121 °C) had no effect on frankfurter color or texture. Because the numbers of L. monocytogenes associated with contaminations of ready-to-eat meats are typically very low, the use of FP in combination with PL and SDA has the potential to reduce the number of frankfurter recalls and foodborne illness outbreaks.     

The Effects of Irradiation at 1.6 kGy on Quality Characteristics of Commercially Produced Ham and Pork Frankfurters over Extended Storage

ABSTRACT: Commercially produced sliced ham and all-pork frankfurters were obtained from a national meat processor and irradiated at 1.6 kGy. The samples were evaluated for color, lipid oxidation, odor, flavor, and the production of volatiles over an 8-wk storage period. Irradiation processing did not affect color values for the ham or frankfurters. Lipid oxidation as measured by 2-thiobarbituric acid-reactive substances (TBARS) did not increase for either the ham or frankfurters. Irradiation processing increased off-odor scores for the ham but not for frankfurters. On the other hand, off-flavor scores were not significantly different for ham but were higher in frankfurters after irradiation processing. Dimethyl disulfide content increased as a result of irradiation in both the ham and frankfurters but decreased during the 8-week storage period. Irradiation processing resulted in the formation of new volatile compounds in the ham samples including heptane, trans -1-butyl-2-methylcyclopropanone, 2-octene, and toluene, which were not present in nonirradiated ham. In the case of frankfurters, irradiation treatment resulted in the formation of 2-butanone, which was not present in the nonirradiated frankfurters. Most volatile compounds that were affected by irradiation processing of either the ham or frankfurters were increased when compared with nonirradiated controls. Although color and lipid oxidation (TBARS) did not seem to be affected by irradiation processing at 1.6 kGy, changes in odor, flavor, and the production of volatiles are of concern if irradiation is to be used to control microbial growth in ready-to-eat pork products.     

Optimizing Quality of Frankfurters Containing Oat Bran and Added Water

Chicken frankfurters fat content was decreased by using various levels of oat bran and added water and evaluated for quality. Frankfurters with higher levels of oat bran had less expressible moisture and required higher shear stress to break. There were no difference in springiness among frankfurters made with different levels of oat bran; however, those with higher oat bran were rated less juicy and more grainy by taste panelists. The addition of water increased intensities of strain, springiness and juiciness, but decreased shear stress and hardness values. Contour plots showed optimum formulation at <2% oat bran 20% of added water.     

Physicochemical Effects of the Lipid Phase and Protein Level on Meat Emulsion Stability,Texture, and Microstructure

ABSTRACT: The effects of beef fat (25%) substitution with rendered beef fat, canola oil, palm oil, or hydrogenated palm oil at varying meat protein levels (8%, 11%, and 14%) were studied in emulsified beef meat batters. There was no significant difference in fat loss among meat batters made with beef fat, rendered beef fat, or palm oil. Hydrogenated palm oil provided the most stable batters at all protein levels. Increasing meat protein to 14% resulted in high fat loss in batters prepared with canola oil, which did not occur in the other formulations. This indicates that the physicochemical characteristics of fat/oil affect emulsion stability. Cooked batter hardness was higher (P < 0.05) when protein level was raised; highest in hydrogenated palm oil batters when compared at similar protein levels. As protein level was raised springiness values were increased in all the meat treatments. Springiness was higher in the canola oil treatments. Light microscopy revealed fat globule coalescence in canola oil meat batters prepared with 14% protein, as well as the development of fat channels and more protein aggregation; both seem to result in lower emulsion stability. Hydrogenated palm oil batters showed fat particles with sharp edges as opposed to the round ones seen in all other treatments.     

Sensory Characteristics of Frankfurters as Affected by Salt, Fat, Soy Protein, and Carrageenan

Continuous variables, salt, fat, and either soy protein or iota-carrageenan, were evaluated using response surface methods to formulate a lower salt/ lower fat franktirter with acceptable palatability attributes. Soy protein increased hardness and off-flavor, and decreased juiciness, saltiness, and flavor intensity. Soy protein should be added to frankfurters at < 3.0% to minimize this effect. Carrageenan increased hardness at low salt concentrations (below 1.7%) and decreased juiciness at fat concentrations > 15%. Flavor intensity increased as carrageenan and fat level increased at 1.3% salt. At 1.65% salt, off-flavor intensity decreased as fat content increased and carrageenan decreased.     

Effects of Organic Acid Salt Solutions on Sensory and Other Quality Characteristics of Frankfurters

ABSTRACT: The technical feasibility of using organic acid salts for surface treatment of frankfurters to determine their sensory and other quality characteristics and their ability to inhibit bacterial growth was investigated. To be practically effective, such treatments for frankfurters should have no adverse effects on meat quality attributes, including sensory quality, color, or texture. A 6% sodium diacetate + potassium benzoate (SD/PB) treatment significantly increased meat flavor, and a 3% sodium lactate + sodium diacetate + potassium benzoate (SL/SD/PB) treatment significantly decreased smoke flavor compared with the control group, but there was no significant difference between controls and the surface-treated frankfurters when comparing salty, sour, or pepper flavors. On the other hand, the SL/SD/PB at either 3% or 6% significantly increased the lightness ( L *) and decreased the redness ( a *) value for frankfurters compared with the control group. For storage time longer than 2 mo, the L * value significantly increased and the a * value decreased. Evaluation of quality characteristics showed that after surface treatment with organic acid salts, no differences were observed between controls and treated frankfurters for pH, nitrite concentration, or sodium content.