Studies to evaluate chemicals and conditions with low-pressure applications for reducing microbial counts on cattle hides

Studies were conducted to identify effective antimicrobials and application parameters that could be used as decontamination interventions to reduce microbial loads on cattle hides before removal from carcasses. In study I, hide swatches inoculated with Escherichia coli O157:H7 were sprayed with 10% acetic acid (at 23 and 55 degrees C), 10% lactic acid (at 23 and 55 degrees C), 3% sodium hydroxide (at 23 degrees C) or 4 and 5% sodium metasilicate (at 23 degrees C). All antimicrobials were evaluated independently after being applied alone, being applied after a water rinse, or being followed by a water rinse. Antimicrobial treatments followed by a water rinse lowered E. coli O157:H7 populations by 0.6 to 2.4 log CFU/cm2 and resulted in hides with a surface pH of 6.3 to 9.2. Treatments in which a water rinse was followed by antimicrobial application lowered E. coli O157:H7 populations by 1.5 to 5.1 log CFU/cm2 but resulted in hides with a surface pH of 3.9 to 10.5. In study II, whole hides were treated with one of four antimicrobials (acetic acid, lactic acid, sodium hydroxide, or sodium metasilicate) followed by a water rinse. Hides were evaluated for aerobic bacterial counts, total coliform counts, and E. coli counts. Generally, all antimicrobials resulted in greater reductions (P < 0.05) of E. coli counts when compared with the control; however, only acetic and lactic acids resulted in greater reductions (P < 0.05) of aerobic bacterial counts and total coliform counts compared with the controls. These antimicrobials could be used to reduce microbial contamination on hides, potentially reducing microbiological contamination transferred to carcasses or to the plant environment.     

Visual evaluation of cattle cleanliness and correlation to carcass microbial contamination during slaughtering

The aim of the study was to establish whether the visual cleanliness of cattle slaughtered was correlated to hide and carcass contamination as indicated by aerobic colony count (ACC), Enterobacteriaceae count (EC) and Escherichia coli count (ECC). Cattle in a slaughterhouse were visually inspected and assigned to a category from 1 (very clean) to 5 (very dirty) based on cleanliness. Fifteen animals for each category were randomly selected, hide and carcass sampled and analyzed for ACC, EC and ECC. Results showed that increasing dirt on cattle was associated with higher ACC, EC and ECC on hide and carcasses. Carcass ACC and ECC belonging to animals classified in cleanliness categories 3, 4 or 5 have a higher probability of exceeding the limits set by the Reg. EU 2073/2005. The study supports the conclusion that the pre-slaughter visual evaluation of animal cleanliness and application of corrective actions can be an effective aid to reduce carcass contamination.     

Mechanical and functional properties of beef products obtained using microbial transglutaminase with treatments of pre-heating followed by cold binding

Beef proteins are considered non-setting proteins and usually gels obtained by adding of microbial transglutaminase are obtained by cooking directly the solubilized paste. The aim of this work was to determine the effect of pre-heating treatments on the mechanical properties of restructured beef gels treated with microbial transglutaminase (MTG). The effect of cooling (cold binding) the solubilized pastes after the pre-heating treatments was also studied. The restructured beef gels were obtained by adding 0.3% MTG or 0% MTG (control). Three pre-heating temperatures (40, 50 or 60 °C) for 30 or 60 min were studied, followed by heating at 90 °C for 15 min. Control samples without pre-heating were also prepared. Cold binding was studied by holding pre-heated gels at 4 °C for 12 h before heating at 90 °C for 15 min. Changes in mechanical properties (texture profile analysis and puncture test), color attributes, expressible water and cooking loss were determined. Results indicated that the better mechanical properties can be obtained by pre-heating beef pastes at 50 °C for 30 min with minimal effect on color, expressible water and cooking loss when 0.3% of MTG is added. It was concluded that there were no practical advantages by pre-heating the gels for 60 min. Cold binding did not improve the mechanical properties of beef gels.     

Immobilization of alkaline phosphatase on magnetic particles by site-specific and covalent cross-linking catalyzed by microbial transglutaminase

Bacterial alkaline phosphatase (BAP) was site-specifically and covalently immobilized on magnetic particles (MPs) using the enzymatic reaction of microbial transglutaminase (MTG). Immobilization efficiency was affected by the chemical surface treatment of MPs and immobilized BAP exhibited more than 90% of the initial activity after 10 rounds of recycling.     

Decontamination of cattle hides prior to slaughter using washes with and without antimicrobial agents

Two trials were conducted to determine the efficacy of cattle wash treatments in reducing pathogens on hides of cattle before slaughter. In trial I, live cattle (n = 120) were washed in an automated, commercial cattle wash system with one of four treatments (single water wash, double water wash, water wash with 0.5% L-lactic acid, or water wash with 50 ppm chlorine). Samples were collected at three locations (brisket, belly, and inside round) pre- and posttreatment to evaluate the effectiveness of treatments on the reduction of aerobic plate counts, coliforms, Escherichia coli and the incidence of Salmonella. For all three locations, bacterial numbers increased from 0.1 to 0.8 log CFU/cm2 posttreatment. In trial II, hide samples were inoculated in the laboratory with 6.0 log CFU/cm2 of rifampicin-resistant Salmonella serotype Typhimurium. Hide wash treatments included higher concentrations of chlorine (100, 200, and 400 ppm) and L-lactic acid (2, 4, and 6%), as well as other antimicrobial agents such as ethanol (70, 80, and 90%), acetic acid (2, 4, and 6%), and Oxy-Sept 333 (0.5, 2, and 4%). Spray wash treatments with ethanol and 4 to 6% concentrations of lactic acid had greater (P < 0.05) mean log reductions than 2% solutions of acetic or lactic acid, as well as 100, 200, and 400 ppm chlorine and the control water wash treatment. Spray wash treatments with Oxy-Sept 333 and 100, 200, or 400 ppm chlorine were not effective (P > 0.05) in reducing Salmonella Typhimurium compared to the (control) distilled water spray wash treatment. Several effective cattle hide interventions were identified in a controlled laboratory setting, but the high concentrations required for effectiveness would likely present problems from an animal welfare standpoint.     

Conventional freezing plus high pressure-low temperature treatment: Physical properties, microbial quality and storage stability of beef meat

Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20 °C) pressurisation (650 MPa/10 min) and air blast freezing (−30 °C) are compared to air blast freezing plus high pressure at subzero temperature (−35 °C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650 MPa/20 °C/10 min) increased significantly expressible moisture while it decreased in pressurised (650 MPa/−35 °C/10 min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh samples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure processing (20 °C or −35 °C) was very effective reducing aerobic total (2-log₁₀ cycles) and lactic acid bacteria counts (2.4-log₁₀ cycles), in fresh and salt-added samples. Frozen + pressurised beef stored at −18 °C during 45 days recovered its original colour after thawing, similarly to just-treated samples while their counts remain below detection limits during storage.     

Hot-Water Rinsing and Trimming/Washing of Beef Carcasses to Reduce Physical and Microbiological Contamination

A field study was conducted to compare trimming/washing procedures with hot-water rinsing as interventions for beef carcass decontamination. Treatments included no trimming/no washing; knife-trimming followed by spray-washing (26°C, 276 kPa followed by 1000 kPa); and hot-water rinsing (> 77°C, 138–152 kPa, 2.5 or 8 sec) following either knife-trimming or no knife-trimming of the contaminated site and spray-washing. Samples were analyzed for counts of total aerobic bacteria, total coliforms and Escherichia coli, as well as for the presence of Salmonella spp. and E. coli O157:H7. Results indicated decontamination of beef carcasses could be achieved by knife-trimming followed by spray-washing or by spray-washing followed by hot-water rinsing.     

Beef quality of young Angus × Nellore cattle supplemented with rumen-protected lipids during rearing and fatting periods

This work evaluated the beef quality parameters of 108 bulls randomly administered to three treatments during rearing in pastures and two treatments during fatting in feedlots, including mineral and rumen-protected lipids. Meat and fat color, cooking yield, shear force, sensorial traits and chemical and fatty acid compositions were evaluated. Generally, the beef quality parameters were not affected by the rumen protected lipids; however, supplementation with rumen-protected lipids during the rearing period yielded darker beef and brighter fat and increased beef tenderness in meat aged for 28 days compared to the meat from animals that received only mineral supplementation. In addition, the percent of meat polyunsaturated fatty acids was negatively affected by the inclusion of protected lipids, yielding 5.58 and 3.72% in animals fed with and without rumen-protected lipids, respectively, during the fatting period.     

Development and analysis of microbial characteristics of an acidulocomposting system for the treatment of garbage and cattle manure

An acidulocomposting system for the treatment of cattle manure with little emission of ammonia gas was developed, and the structure of its microbial community was investigated by denaturing gradient gel electrophoresis (DGGE) and clone library construction. An acidulocomposting apparatus (BC20, 20 L) was operated for 79 days to treat 2 kg (wet wt) of garbage per 1 or 2 days. On day 80 of operation, the substrate was changed from garbage to cattle manure (1 kg of beef cattle manure was added to the apparatus every 2 or 3 days), and the system continued operating from days 80 to 158. The compost in the vessel was under acidic conditions at pH 5.2–5.8, and ammonia emission was below the detectable level (< 5 ppm) throughout the period of cattle manure feeding. Total nitrogen and total carbon in the compost were 26–29 and 439 – 466 mg/g of dry weight, respectively, which are higher than those in general cattle manure compost. The main acids accumulated during operation were lactic and acetic. Sequencing analysis targeting the 16S rRNA gene revealed the stable dominance of the bacterial phylum Firmicutes, with a high proportion of the isolates belonging to the genus Bacillus. Using a culturing method with MRS agar, we isolated lactic acid bacteria (LAB) related to Pediococcus acidilactici, Weissella paramesenteroides, and Lactobacillus salivarius, indicating the existence of LAB in the system. These results indicate that acidulocomposting treatment of cattle manure is not accompanied by ammonia emission and that Bacillus and LAB may be the key components in the system.     

Evaluation of feedlot cattle working chute behavior relative to temperament,tenderness, and postmortem proteolysis

The objective was to investigate if the association between working chute behavior and beef tenderness found in our previous study is related to protein degradation and calpain system activity. Crossbred steers (n = 183) allotted to 16 pens were weighed every 28 d. Temperament was evaluated as exit velocity (EV), chute score (CS), and catch score (CAPS). Between 14 and 16 mo of age (606 ± 52 kg), steers were harvested. Strip steaks were collected and aged for 14 d. Subsamples were collected at 36 h and 7 d postmortem and analyzed for calpastatin activity, μ-calpain autolysis, and troponin-T degradation. Shear force (WBSF) was correlated (P < 0.05) with calpastatin activity and measurements of troponin-T. Calpastatin activity, μ-calpain autolysis, and troponin-T measurements did not correlate with the measurements of EV, CS, and CAPS. Therefore, activation of the calpain system or differences in protein degradation did not appear to influence the differences in tenderness that are correlated with working chute behavior.     

柠檬酸对花生B族黄曲霉毒素脱毒效果的研究

研究分析不同浓度的柠檬酸溶液在不同的液料比和不同作用时间下花生中B族黄曲霉毒素的含量变化。结果表明,随着柠檬酸溶液浓度的提高,液料比的增加,作用时间的延长,花生中B 族黄曲霉毒素的含量降低,脱毒效果越好。用80g/L 的柠檬酸溶液,液料比(V/m)为5:1 对霉变后染有B 族黄曲霉毒素(AFB1 和AFB2)的花生颗粒(98.60μg/kg)浸泡30min 具有很好的脱毒效果,处理后,黄曲霉毒素含量小于20μg/kg,达到国标GB2761 - 2005 对花生中黄曲霉毒素限量的要求。     

Impedance measurements to assess microbial contamination of ready-to-use vegetables

 An impedometric method for estimating the microbial load of ready-to-use vegetables, either inoculated or not inoculated with antimicrobial-producing lactic acid bacteria, was investigated. The correlation (R ²) between total mesophilic bacteria (log cfu/g) and time to detection was 0.889. A discrepancy was observed for the impedometric measurement of low coliforms counts, particularly in samples inoculated with lactic acid bacteria and stored at 8°C for 6 days. Time to detection for the two groups of microorganisms was less than 11 h. Received: 25 November 1996 / Revised version: 23 January 1997     

Impedance measurements to assess microbial contamination of ready-to-use vegetables

 An impedometric method for estimating the microbial load of ready-to-use vegetables, either inoculated or not inoculated with antimicrobial-producing lactic acid bacteria, was investigated. The correlation (R ²) between total mesophilic bacteria (log cfu/g) and time to detection was 0.889. A discrepancy was observed for the impedometric measurement of low coliforms counts, particularly in samples inoculated with lactic acid bacteria and stored at 8°C for 6 days. Time to detection for the two groups of microorganisms was less than 11 h. Received: 25 November 1996 / Revised version: 23 January 1997     

Process optimisation of pulsed electric fields pre-treatment to reduce the sous vide processing time of beef briskets

This study used multiple regression to model the effect of pulsed electric field (electric field strengths 0.7, 1.0 or 1.5 kV cm⁻¹) and sous vide (60 °C for either 12, 18 or 24 h) processing on the quality parameters (tenderness, cooking loss, colour, lipid stability) of beef brisket. Pulsed electric fields (PEF) at 0.7 kV cm⁻¹ and 1.5 kV cm⁻¹ followed by sous vide processing for 12–20.2 and 20.8–23.7 h, respectively gave the lowest values for hardness (<20.2 N), shear force (100.5 N mm⁻¹ s⁻¹) and cooking loss (<17.4%). PEF treatment prior to sous vide processing had no significant effect on lipid oxidation, colour stability, cooking loss or in vitro protein digestibility of sous vide-processed brisket. Increasing the electric field strength and/or prolonging the sous vide time significantly increased collagen solubilisation in the sous vide brisket. This study demonstrated that a PEF pre-treatment can reduce sous vide processing time while enhancing the tenderness of tough meat cuts.     

Ability of near infrared reflectance spectroscopy (NIRS) to estimate physical parameters of adult steers (oxen) and young cattle meat samples

The potential of NIRS-based models to predict several physical parameters of oxen and young cattle beef protected by a quality mark was evaluated. Fifty-three and 67 samples of Longissimus thoracis muscle corresponding to oxen and young cattle reared in extensive conditions were analyzed for pH, colour (L^∗, a^∗, b^∗), water holding capacity (WHC) and Warner–Braztler shear force (WBSF), according to the conventional methods. Several factors which might have jeopardized the prediction of pH, a^∗, WHC and WBSF by NIRS are considered in the discussion section. However, the best NIR calibrations, tested by full cross-validation, were for L^∗ (R² = 0.869; SE_CV = 1.56) and b^∗ (R² = 0.901; SE_CV = 1.08) colour parameters in meat samples from young cattle. It can be concluded that NIRS could be a useful tool for estimating the colour of young cattle meat samples, primary consideration for consumers when making purchasing decisions.     

漆酶的固定化及其在造纸废水处理中的应用

漆酶(对-二酚:双氧氧化还原酶)是多铜氧化酶中的一种含铜的糖蛋白氧化酶.参与木素的降解或聚合,具有氧化木素的能力.固定化漆酶能够延长漆酶的使用寿命,提高漆酶的稳定性及其对环境的耐受性,因此它具有比游离漆酶更好的使用性质.综述了近年来漆酶的固定化方法及其在造纸废水处理中的应用与研究现状.