Application of multiple antimicrobial interventions for microbial decontamination of commercial beef trim

Commercially produced, irregularly sized (range, 100 to 400 cm2), uninoculated beef trim was treated by a previously optimized multihurdle antimicrobial process under spray system or hot air gun with set-up speed (1 cm/s): W (water wash at 65 psi for five passes) + HW (82 degrees C water at 30 psi for three passes) + HA (510 degrees C air for five passes) + L (2% [vol/vol] room temperature lactic acid wash at 30 psi for three passes). After treatment, the trim was finely ground, vacuum packaged, and stored at 4 degrees C for up to 20 days. At regular intervals (0, 5, 10, 15, and 20 days of storage at 4 degrees C), the ground beef was analyzed to measure mesophilic aerobic bacteria (APC), coliforms, psychrotrophic bacteria (PCT), and presumptive lactic acid bacteria (PLAB) and compared with the untreated control. The numbers of APC, coliforms, PCT, and PLAB were reduced to nearly nondetectable levels immediately after treatment, with significant differences compared with the control (P < 0.05), then started to increase after 5 to 10 days of storage at 4 degrees C. After 20 days, microbial populations of treated ground beef were significantly lower than those of nontreated ground beef for the numbers of APC, coliforms, PCT, and PLAB (P < 0.05), with differences of 1.2, 2.4, 1.6, and 1.6 log CFU/g, respectively. Based on microbial reduction and quality aspects, the multihurdle antimicrobial process was identified as an effective intervention to reduce coliforms on beef trim.     

Evaluation of combination treatment processes for the microbial decontamination of pork trim

Combination treatment processes for the microbial decontamination of pork trim were developed and evaluated. Lean pork trim tissue (LPT) and fat-covered pork trim tissue (FPT) inoculated with swine feces were treated with intervention processes as follows: (i) control (untreated), (ii) water (15 degrees C, 120 s), (iii) water followed by lactic acid wash (15 degrees C, 75 s), (iv) combination 1 (water plus hot water [65.5 degrees C, 15 s] plus hot air [510 degrees C, 60 s] plus lactic acid), (v) combination 2 (water plus hot water [82.2 degrees C, 15 s] plus hot air [510 degrees C, 75 s] plus lactic acid), and (vi) combination 3 (water plus hot water [82.2 degrees C, 45 s] plus hot air [510 degrees C, 90 s] plus lactic acid). Populations of aerobic bacteria, psychrotrophic bacteria, coliforms, Escherichia coli, and lactic acid bacteria were determined before and after treatment and at days 2 and 7 of 4 degrees C storage. Regardless of the intervention treatment, lower microbial populations were observed on FPT than on LPT immediately after treatment and during the 7-day storage period. Both LPT and FPT treated with water plus lactic acid, combination 1, combination 2, and combination 3 had lower remaining populations of all microbial groups immediately after treatment than did water-treated samples. Populations of aerobic bacteria, coliforms, E. coli, and lactic acid bacteria on either LPT or FPT did not statistically increase during the 7-day storage period. On LPT, populations of psychrotrophic bacteria grew during 4 degrees C storage but remained lower at day 7 on LPT treated by combinations 2 and 3 (2.29 and 1.89 log10 CFU/cm2, respectively) than on LPT treated with water (4.07 log10 CFU/cm2) or water plus lactic acid (3.52 log10 CFU/cm2). Populations of psychrotrophic bacteria remained below detectable levels throughout the 7-day storage on FPT treated with water plus lactic acid or any of the three combination treatments. Treatment of pork trim with any of the combination treatments significantly (P < 0.05) affected the color and emulsion stability of the ground pork. Water and water plus lactic acid were the most favorable treatments in reducing microbial populations on pork trim without affecting the quality attributes of the ground pork.     

Development of a modified dry curing process for beef

The development of a dry curing process using physical treatments to promote the diffusion of the cure ingredients was studied. Vacuum pulsing with and without tumbling, continuous vacuum, and tumbling only treatments were compared with a conventional static dry cure control method on beef M. supraspinatus. Vacuum tumble and tumble only treatments gave highest core salt content after 7 days conditioning (3.3% and 3.1%, respectively). All test treatments resulted in higher colour uniformity and lower % cook loss in comparison to control (P < 0.001). The control and vacuum pulsed samples were tougher (P < 0.001). Vacuum tumble and tumble only treatments gave higher acceptability (P < 0.001). Based on these findings for M. supraspinatus, indicating that the vacuum tumble treatments gave the best results, further testing of this method was conducted using the M. biceps femoris in addition to the M. supraspinatus. Cured beef slices were stored in modified atmosphere packs (MAP) (80%N₂:20%CO₂) for up to 28 day at 4 °C. Redness (a^∗, P < 0.001) decreased over storage time in M. biceps femoris. Vacuum tumble treatment increased (P < 0.05) redness in M. supraspinatus. Results obtained demonstrate the benefits of vacuum tumbling over the other physical treatments as a method for accelerating the dry curing process, producing dry cured beef products with enhanced organoleptic quality and increased yields.     

Development of a portable spectrofluorimeter for measuring the microbial spoilage of minced beef

The evaluation of meat spoilage is based on sensory and microbiological analyses. The disadvantages of sensory analyses are its reliance on highly trained panelists, a procedure which makes it costly and unattractive for routine analyses. Moreover, the classical microbiological analyses are lengthy, costly and destructive. In this study a portable fluorescence spectrometer was tested to quantify minced beef spoilage. This study was investigated on samples stored aerobically and under vacuum at 5 and 15 °C. Total viable counts (TVC), Pseudomonas, lactic acid bacteria, and yeast/molds counts were investigated with classical culture methods. Fluorescence spectra were recorded on the same samples using different excitation LEDs (280, 320, and 380 nm). PLS-R with leave-one-out cross validation was used to perform calibration and validation models. The PLS-R models presented good R2(CV) (0.50-0.99) and ratio of standard deviation (RPD(CV): 1.40-8.95) values after cross-validation. It could be concluded that portable spectrofluorimeters are promising devices to evaluate spoilage in minced beef.     

Microbiological characterization of imported and domestic boneless beef trim used for ground beef

The United States imports lean boneless beef trim from Australia (AUS), New Zealand (NZL), and Uruguay (URY) to meet demand for ground beef production. The reported incidence of and etiological agents responsible for foodborne diseases differ between these countries and the United States. Our objective was to determine whether current U.S. microbiological profiling adequately addresses the potential differences between foreign and domestic beef trim. We compared the hygienic status of imported and domestic (USA) beef trim by enumeration of aerobic bacteria, Enterobacteriaceae, coliforms, Escherichia coli, and Staphylococcus aureus. We also compared the prevalence of pathogens between imported and domestic samples by screening for the presence of Salmonella, Campylobacter spp., Listeria spp., and non-O157 Shiga toxin-producing E. coli (STEC). A total of 1,186 samples (487 USA, 220 AUS, 223 NZL, and 256 URY) of boneless beef trim were analyzed. Results of enumeration revealed significant differences between samples from all countries, with the lowest pathogen numbers in samples from AUS and the highest in samples from URY. Six Salmonella isolates (1 NZL, 1 URY, and 4 USA), 79 L. monocytogenes isolates (4 AUS, 5 NZL, 53 URY, and 17 USA), and 7 Campylobacter isolates (1 NZL, 1 URY, 5 USA) were found among the trim samples tested. Non-O157 STEC prevalence was 10% in NZL samples and about 30% in all of the other samples; 99 STEC strains were isolated. Serotyping of these isolates revealed that serotypes associated with hemolytic uremic syndrome were not different in prevalence between imported and domestic beef trim. Although it may be tempting to do so, these data cannot be used to compare the microbiological quality of beef trim between the countries examined. However, these results indicate that the current pathogen monitoring procedures in the United States are adequate for evaluation of imported beef trim.     

Development and evaluation of an on-line hide decontamination procedure for use in a commercial beef processing plantt

The hides of cattle are the source of Escherichia coli O157:H7 that contaminates beef carcasses during commercial beef processing. Therefore, effective interventions that reduce hide contamination should reduce subsequent carcass contamination. The first objective of this study was to identify the most effective reagents for decontamination of beef hides. Cattle hides draped over barrels were used for in vitro experiments to compare the efficacy of washes using 1.6% sodium hydroxide, 4% trisodium phosphate, 4% chlorofoam, or 4% phosphoric acid, each followed by a rinse step using either water or acidified (pH 7.0) chlorine at 200 or 500 ppm. All treatments using a water rinse reduced hide coliform counts by 1.5 to 2.5 log CFU/ 100 cm2. Compared with water rinses, 200 and 500 ppm acidified chlorine rinses increased efficacy by approximately 1.0 and 2.0 log CFU/100 cm2, respectively. Vacuuming of the treated areas to remove excess liquid improved hide cleanliness by an average of an additional 1.0 log CFU/100 cm2. The second objective was to evaluate the use of an on-line hide-wash cabinet that used a sodium hydroxide wash and a chlorinated (1 ppm) water rinse. Hides sampled before entering and after exiting the cabinet had aerobic plate counts and Enterobacteriaceae counts that were reduced by 2.1 and 3.4 log CFU/100 cm2, respectively, and the prevalence of E. coli O157 on hides was reduced from 44 to 17% when the cabinet was in use. Preevisceration carcass aerobic plate counts and Enterobacteriaceae counts were both reduced by 0.8 log CFU/100 cm2, and the prevalence of E. coli O157 on preevisceration carcasses was reduced from 17 to 2% when the cabinet was in use. These results support decontamination of hides as an effective means to reduce pathogen contamination of cattle carcasses during processing.     

新疆风干牛肉成熟过程中理化及微生物特性分析

对新疆风干牛肉自然发酵成熟过程中的理化特性和微生物变化规律进行了检测和分析。结果表明,新疆风干牛肉成熟过程中最低pH值在5.78左右;最终水分活度为0.76,水分含量在20%左右;在自然风干成熟过程中酸价、过氧化值和硫代巴比妥酸值(TBA)均随时间的增加而增大。新疆风干牛肉自然发酵成熟过程中的优势菌主要有乳酸菌、葡萄球菌和微球菌。     

辐照牛干巴在贮藏过程中微生物变化的研究

牛干巴是云南回民主要的肉制品,也是云南省的名特畜产品,但由于传统工艺腌制的牛干巴不仅味成、颜色暗,且保存也仅限于真空包装,储存过程中时有霉变现象发生.本实验通过研究真空包装牛干巴用60Coγ6kCy和60Coγ8kGy剂量辐照后,在6个月的贮藏过程中感官指标和微生物指标的变化情况,以摸索辐照技术对延长牛干巴保存期的可行性.结果表明,经过辐照处理的牛干巴色泽变得更鲜红,其菌落总数、霉菌、酵母及乳酸菌的繁殖均较慢.实验研究证明,辐照用于牛干巴保鲜是可行的,并且效果显著.本研究为牛干巴远销和食用提供了理论依据.     

A laboratory evaluation of a novel hot water cabinet for the decontamination of sides of beef

A hot water cabinet based on an idealized distributor design for the decontamination of sides of beef is described and a laboratory evaluation of this novel cabinet is reported.
Beef sides were inoculated with E. coli and exposed to mean water temperatures at the surface tissue ( T _f) of 83.5, 74.2, 66.0 and 44.5°C for 10 or 20 s. Mean log₁₀ reductions of bacteria for 10-s exposures were 2.23, 1.40, 0.91 and 0.2. For 20 s, reductions were 2.98, 2.14, 1.17 and 0.1. There was a significant ( P < 0.05) linear relationship between log reductions and T _f which varied with exposure time. At a T _f of 83.5°C with exposure times greater than 20 s, carcass bloom was judged to be permanently and adversely affected. At shorter times or with lower temperatures this did not occur.
Evaporative heat losses were well correlated with the pressure driving force ( r = 0.89) and gravity driving force ( r = 0.92) for air interchange between the cabinet and its surrounds.
The running cost using the distributor cabinet was one-third of that of an existing spray cabinet when compared at the maximum reduction of log 1.3 (95%) achieved by the spray cabinet. An additional advantage of the distributor cabinet is its constructional simplicity.     

Hot water decontamination of beef carcasses for reduction of initial bacterial numbers

Areas on freshly slaughtered beef carcasses were sprayed with hot (95°C), sterilized, distilled water in order to elevate carcass surface temperature to 82°C. A significant (P < 0·05) reduction in bacterial numbers was observed between control (prespray) and hot water treated carcass surfaces. These results indicate that microbial decontamination of beef carcasses with hot water will be effective if an approprite spraying apparatus is used.     

Efficiency of pulsed UV light for microbial decontamination of food powders

The aim of this study was to evaluate the efficiency of pulsed light on the destruction of dried microorganisms on fluidized glass beads and to determine treatment parameters (energy level, water activity, final product quality) for process optimization. The applied drying method allowed microorganisms to remain viable on glass beads or dried powdered products with viability yields approaching 100%. The pulsed UV light system enabled an efficient fluidization of food powders, even for granular products (up to 5 mm diameter) and avoided shadowed areas. For Saccharomyces cerevisiae decontamination, the dose effect of UV rays was preponderant with glass beads and quartz plate, and in this case, 58 J/cm2 were required to decrease the microbial population by 7 log. For colored food powders (black pepper and wheat flour), the thermal effect of pulsed light dominated the UV effect.     

Development of NIR-HSI and chemometrics process analytical technology for drying of beef jerky

Beef jerky samples immersed in brine or water, both with and without ultrasound treatment were dried at 60 °C for 30, 60, 90, 120, 150, 180, 210 and 240 min. Drying behaviour was evaluated using ten drying kinetic models and hyperspectral imaging. All samples reached water activity values (Aw) < 0.85 during the first 90 min of drying. Moisture content (MC) of beef jerky was predicted using near infrared hyperspectral imaging and chemometrics. Partial least squares regression, band selection and spectral pre-treatments were applied to develop MC prediction models using beef jerky spectra. Most of the MC prediction models developed in this work had RPD values >4, indicating their suitability for process control applications. The best performing MC prediction models for the non-ultrasound and ultrasound treated samples were developed using the ensemble Monte Carlo variable selection (EMCVS) on second derivative of log(1/R) spectra and EMCVS-selectivity ratio on linear detrended log (1/R) spectra, respectively. This study demonstrated the potential of NIR-HSI and chemometrics as a PAT tool for drying of beef jerky.     

A model for the hot water decontamination of sides of beef in a novel cabinet based on laboratory data

A predictive model for the hot water decontamination of sides of beef in a novel design of cabinet is presented and its usefulness illustrated. The model is based on laboratory data and permits assessment of bacterial reductions, production rates, unit energy costs and changes to cabinet dimensions and ambient temperatures. The advantages of a 'standard' cabinet recommended for a wide range of abattoir production rates are outlined. For a production rate of 135 sides h⁻¹, 90% and 99% reductions in bacteria at the site of minimum treatment (the neck) could be achieved at costs of less than 0.016% and 0.03% respectively of the value of the meat. The model assumes limited exposure of the sides to the hot water to prevent a permanent impairment of meat bloom. A graphical summary is presented and limitations of the model are discussed.     

Theoretical analysis of two hot water cabinet systems for decontamination of sides of beef

The theory underlying the use of hot water to reduce the numbers of microbial contaminants of public health significance on freshly slaughtered animals was investigated. An analysis of steady-state predictions of microbial reductions and accompanying evaporative heat and mass losses in a hot water cabinet for the decontamination of beef sides is developed, based on published correlations. This is more comprehensive than previously undertaken and is used to compare two methods of contacting hot water with the sides of beef: conventional pressure sprays and an alternative, overhead distributor or 'deluge' system. Predictions indicate that a distributor cabinet does not need doors or thermal insulation, and highlight the potential economy and practical advantages over conventional spraying.     

Efficacy of acidic electrolyzed water for microbial decontamination of cucumbers and strawberries

An examination was made of the efficacy of acidic electrolyzed water (AcEW, 30 ppm free available chlorine), ozonated water (5 ppm ozone), and a sodium hypochlorite solution (NaOCl, 150 ppm free available chlorine) for use as potential sanitizers of cucumbers and strawberries. AcEW and NaOCl reduced the aerobic mesophiles naturally present on cucumbers within 10 min by 1.4 and 1.2 log CFU per cucumber, respectively. The reduction by ozonated water (0.7 log CFU per cucumber) was significantly less than that of AcEW or NaOCl (P < or = 0.05). Cucumbers washed in alkaline electrolyzed water for 5 min and then treated with AcEW for 5 min showed a reduction in aerobic mesophiles that was at least 2 log CFU per cucumber greater than that of other treatments (P < or = 0.05). This treatment was also effective in reducing levels of coliform bacteria and fungi associated with cucumbers. All treatments offered greater microbial reduction on the cucumber surface than in the cucumber homogenate. Aerobic mesophiles associated with strawberries were reduced by less than 1 log CFU per strawberry after each treatment. Coliform bacteria and fungi associated with strawberries were reduced by 1.0 to 1.5 log CFU per strawberry after each treatment. Microbial reduction was approximately 0.5 log CFU per strawberry greater on the strawberry surface than in the strawberry homogenate. However, neither treatment was able to completely inactivate or remove the microorganisms from the surface of the cucumber or strawberry.     

牛肉酶解物制备肉味香精的研究

研究了以牛肉酶解物、木糖和半胱氨酸盐酸盐为主要原料,经美拉德反应制备肉味香精的工艺条件,并对影响肉味形成的5个因素进行考察,以芳香喜好性为指标,通过响应面分析确定其最佳的反应条件.研究结果表明,在反应温度118℃、时间81 min、pH7.1、半胱氨酸盐酸盐及木糖添加量分别为25%和23%时,肉香最好,并且生成了强烈而协调的带有烤牛肉味的香气.     

Comparison of the microbial populations of retail beef and pork

Retail samples of beef mince, beef rump, pork mince and pork rump were enumerated for total plate count, coliforms, Escherichia coli, Staphylococcus aureus, Salmonella and Trichinella spiralis. Total plate counts were similar for all samples; however, the populations of coliforms and Staphylococcus aureus were higher in minced meats than in rumps (P < 0·05). Minced pork was found to carry higher loads of Staphylococcus aureus than any other meat (P < 0·05). Salmonella and Trichinella spiralis were not detected in any sample.