High pressure and freezing temperature effect on quality and microbial inactivation of cured pork carpaccio

The effects of high hydrostatic pressure (HHP: 0, 400, and 600 MPa) and freezing temperature (-15° vs. -35°C) were evaluated on the quality and microbial inactivation of cured pork carpaccio. Samples treated with HHP resulted in lighter and yellower color, higher Chroma, shear force, scores for pink color, cooked and gel appearance, incidence of iridescence, lower scores for brightness and raw meat appearance and lower levels of lactic acid bacteria and psychrotrophs during shelf life compared with untreated samples (P<0.05). Treating carpaccio at -35°C resulted in a darker color and a more tender carpaccio with a higher rating for crumbliness and lower rating for fibrousness and chewiness compared with -15°C (P<0.05). While HHP is effective in microbial inactivation and shelf life extension of pork carpaccio, product quality may be decreased due to lower tenderness and poorer appearance. However, HHP in combination with low freezing temperature can be used successfully to deliver high quality pork carpaccio with extended shelf life to the ready-to-eat market.     

Lipid composition of pork muscle in relation to the metabolic type of the fibres

The aim of this study was to investigate the relationships between lipid composition and metabolic type of the muscles in pork. Five muscles (Longissimus dorsi, Biceps femoris, Psoas major, Trapezius and Masseter) were chosen in order to cover a broad range of metabolic type. The results showed that:     

Influence of putrescine,cadaverine, spermidine or spermine on the formation of N-nitrosamine in heated cured pork meat

The influence of biogenic amines (i.e. putrescine, cadaverine, spermidine and spermine) on the N-nitrosamine formation in heated cured lean meat was studied in the presence or absence of sodium nitrite and at different meat processing temperatures. Experimental evidence was produced using gas chromatography with thermal energy analysis detection (GC–TEA). Concentration of N-nitrosamines was modelled as a function of the temperature and the nitrite concentration for two situations, i.e. presence or absence of added biogenic amines to the meat. The significance of the influence of the changing parameters was evaluated by ANOVA (Analysis of Variance).     

香辛料提取物对猪肉肌原纤维蛋白功能性质的影响

将迷迭香、肉桂和丁香提取物分别添加到猪肉糜中,4℃冷藏9 d,通过测定肌原纤维蛋白的溶解度、表面疏水性、乳化性、凝胶性和流变学特性,研究不同香辛料提取物对蛋白功能性质的影响。结果表明:冷藏时间增加,未添加香辛料对照组的溶解度逐渐降低,表面疏水性增加,乳化活性和乳化稳定性降低,凝胶强度和凝胶保水性降低,且形成凝胶网络能力降低。而不同香辛料提取物对肌原纤维蛋白功能特性的影响不同,总体来说,能够提高溶解度,降低表面疏水性增加的程度,较好地维持乳化活力和乳化稳定性,但提取物对蛋白凝胶特性无改善作用。因此,在肉制品加工过程中要考虑选用的香辛料及其使用量对产品功能性质的影响,避免对产品质构产生不利影响。     

The microbiological condition of minced pork prepared at retail stores in Athens, Greece

Minced pork samples (n = 150) obtained from butchers' shops and supermarkets in Greece, during summer (n = 75) and winter (n = 75), were subjected to microbiological analysis. Microbial counts (log CFU/g) for the parameters tested were: total viable count (TVC), 6.8 ± 1.0; Pseudomonas spp., 6.4 ± 1.2; Brochothrix thermosphacta, 5.9 ± 1.1; lactic acid bacteria, 5.3 ± 1.0; yeasts and moulds, 4.6 ± 0.7; hydrogen sulfide (H(2)S)-producing bacteria, 4.3 ± 1.3; Enterobacteriaceae, 3.6 ± 1.2; total coliforms, 2.9 ± 1.1; Escherichia coli, 1.4 ± 0.7; Staphylococcus spp., 4.3 ± 1.0; S. aureus, 2.4 ± 0.9, and Listeria spp., 1.4 ± 0.6. The highest correlations were between TVC and pseudomonads, B. thermosphacta and H(2)S-producing bacteria, while the lowest were between total coliforms and all other groups of microorganisms except Enterobacteriaceae. The type of retail outlet and the seasonality of sampling did not have any significant effects (p>0.05) on minced pork meat quality. Interrelationships between (i) meat quality and shelf life, (ii) hygienic conditions during mince preparation and (iii) personnel hygiene were revealed.     

The effects of modified atmosphere gas composition on microbiological criteria, color and oxidation values of minced beef meat

This paper reports the effects of modified atmosphere gas compositions with different concentrations of CO(2)/O(2)/N(2) on color properties (L*, a* and b* values), oxidation stability (TBARS value) and microbiological properties of minced beef meat stored at +4 °C. Sampling was carried out on the 1st, 3rd, 5th, 7th, 9th, 11th and 14th day of storage. The gas mixtures used were as follows: (i) %30O(2) + %70CO(2) (MAP1), (ii) %50O(2) + %50CO(2) (MAP2), (iii) %70O(2) + %30CO(2) (MAP3), (iv) %50O(2) + %30CO(2) + %20N(2) (MAP4), and (v) %30O(2) + %30CO(2) + %40N(2) (MAP5). Control samples (AP) were packaged under atmospheric air. Pseudomonas, lactic acid bacteria, Brochothrix thermosphacta, and Enterobacteriaceae members were monitored. Among these five modified atmosphere gas compositions, the best preservation for minced beef meat was in MAP4 gas combination maintaining acceptable color together with oxidation stability and acceptable microbial loads until the end of storage period of fourteen days.     

半干咸鱼水分活度的研究

研究了影响半干咸鱼水分活度的因素,采用添加品质改良剂和控制终产品的含盐量等方法,探讨其对半干咸鱼水分活度的影响状况。结果表明,半干咸鱼制品的水分活度主要取决于终产品的含盐量,随着含盐量增加,水分活度显著下降;丙二醇、丙三醇、磷酸二氢钠与磷酸氢二钠等品质改良剂的适量添加,也可明显降低半干咸鱼的水分活度。     

Influence of ascorbic acid and pH on the formation of N-nitrosodimethylamine in cured pork containing added dimethylamine.

Under laboratory conditions simulating normal bacon curing, the conversion to N-nitrosodimethylamine (NDMA) of dimethylamine (DMA) added to pork, was 0.1%. Addition of sodium ascorbate to the brine was shown to suppress NDMA formation from added DMA in this simulated curing system and in experimental curing of pork middles spiked with DMA. Heating, by canning or frying, resulted in the formation of small amounts of NDMA in the lean and considerably higher concentrations in the fried fat. However, the lowest amounts of NDMA were found in the bacon cured in the presence of ascorbate.     

A water extraction, static headspace sampling, gas chromatographic method to determine MTBE in heating oil and diesel fuel

A method was developed to determine the fuel/water partition coefficient (KMTBE) of methyl tert-butyl ether (MTBE) and then used to determine low parts per million concentrations of MTBE in samples of heating oil and diesel fuel. A special capillary column designed for the separation of MTBE and to prevent coelution and a gas chromatograph equipped with a photoionization detector (PID) were used. MTBE was partitioned from fuel samples into water during an equilibration step. The water samples were then analyzed for MTBE using static headspace sampling followed by GC/PID. A mathematical relationship was derived that allowed a KMTBE value to be calculated by utilizing the fuel/water volume ratios and the corresponding PID signal. KMTBE values were found to range linearly from 3.8 to 10.9 over a temperature range of 5-40 degrees C. This analysis method gave a MDL of 0.7 ppm MTBE in the fuel and a relative average accuracy of +/-15% by comparison with an independent laboratory using purge and trap GC/ MS analysis. MTBE was found in home heating oil in residential tanks and in diesel fuel at service stations throughout the state of Connecticut. The levels of MTBE were found to vary significantly with time. Heating oil and diesel fuel from terminals were also found to contain MTBE. This research suggests thatthe reported widespread contamination of groundwater with MTBE may also be due to heating oil and diesel fuel releases to the environment. used extensively for the past 20 years as a gasoline additive (up to 15 wt %) to reduce automobile carbon monoxide and hydrocarbon emissions. The fact that MTBE is highly soluble in water (approximately 5 wt %) (3) and chemically inert when compared to other fuel constituents causes it to be often detected at high concentrations in groundwater in the vicinity of gasoline spills. The EPA has reported that low levels of MTBE in drinking water (above 40 microg/L) may cause unpleasant taste and odors and has designated MTBE as a possible human carcinogen (4). Past studies have concentrated on the reporting of MTBE levels in groundwater near gasoline spills. Happel et al. reported an MTBE occurrence rate of approximately 78% at locations where hydrocarbons have impacted groundwater (5). Johnson et al. estimate that 9,000 leaking underground fuel tanks have caused MTBE contamination at community water supplies in the 31 states surveyed (excluding California and Texas) (6). Robbins et al. reported finding a significant number of MTBE detections in groundwater samples taken at sites in Connecticut known to be contaminated by heating oil spills (7). Later, this same research group reported finding MTBE contamination to range from 9.7 to 906 mg/L in heating oil and from 74 to 120 mg/L in diesel fuel in samples collected from storage tanks in Connecticut (8). The method used to analyze these samples was based on fuel-water partitioning and GC analysis. This present study provides the detailed basis for that analytical method. MTBE fuel-water partition coefficients as a function of temperature, which are critical to the method, are also presented. This study also reports on variations in MTBE levels as a function of time observed at several residences and a service station. Analytical results are reported for samples taken from terminals as part of an effort to assess the sources of MTBE in heating oil and diesel fuel.     

Influence of different spices on the microbial reduction and storability of laboratory-processed tomato ketchup and minced meat

At 1% (w/w) each of 6 non-commercial spices (Xylopia aethiopica, Aframomum melegueta, Monodoran myristica, Piper guineense, Icacina spp and Congronema latifolia) when added to laboratory-processed tomato ketchup and minced meat reduced spoilage microbial populations to different levels. Tomato ketchup spiced with M. myristica remained sterile after 24 h incubation at room temperature (26 ± 2 °C) whilst control samples had bacterial and yeast counts of 1.5 ± 10⁷ cfu/g and 2.0 ± 10⁵ pro-pagules/g, respectively. X. aethiopica also reduced bacterial populations in tomato ketchup. In spiced minced meat, only X. aethiopica and C. latifolia showed an inhibitory effect on yeasts. Other spices used were not or relatively less effective against bacteria and yeasts.     

Influence of pig crossbreed on the composition, volatile compound content and flavour of dry cured ham

The extraction of volatile compounds from dry-cured ham using a dynamic head-space method coupled with gas chromatography mass-spectrometry (GC-MS) enabled the identification of a large number of components. Some of these compounds exhibited intense sensory characteristics during odour assessment. Using similar technology, the effect of pig crossbreeds: Landrace × Large-White, Duroc × Gascon-Meishan, Piétrain × Gascon-Meishan and Large-White × Gascon-Meishan, on both volatiles and the flavour of dry-cured hams was limited, although differences were observed in aromatic compounds like 1-octen-3-ol (mushroom), 2,3-butanedione and acetoin (butter like).     

Antioxidative activity of summer savory (Satureja hortensis L.) and rosemary (Rosmarinus officinalis L.) in minced,cooked pork meat

The sensory intensity measured as theabsolute threshold value of spice andrecognition of spice was evaluated for summer savory and rosemary in meat balls. The values forabsolute threshold value of spice were found to be significantly lower for rosemary than for summer savory. The antioxidative activity of the spices was analysed in two accelerated model systems and in a storage experiment. In one of the model systems, oxidation was accelerated by heat and by an elevated pressure of oxygen. Both spices significantly improved the oxidative stability of the meat balls in this model system. In the second model system metal catalyst oxidation in a meat slurry was used and a reduction in the oxidative processes in samples containing the spices was again shown. In both model systems a slightly higher antioxidative activity was seen for rosemary compared to summer savory. In the storage experiment, the spices were added at a sensorially acceptable level and the heat-treated meat balls were stored at 5°C. A significant reduction in the development of warmed-over flavour (WOF) caused by the addition of spices was measured by a reduction in 2-thiobarbituricacid-reactivesubstances (TBARS) and in hexanal. A reduction in TBARS of approximately 30% in meat balls containing added spices was seen independently of packaging in 1% oxygen or in atmospheric air and the reduction (30%) was constant throughout the storage period.     

Effect of the dietary supplementation with vitamin E on colour stability and lipid oxidation in packaged, minced pork

The effect of supplementation of vitamin E (200 W kg⁻¹ feed) in the diet of pigs on colour stability and lipid oxidation in minced pork was studied. Control and enriched diets were provided for the last 12 weeks before slaughter. Half of the samples of minced shoulder meat from control and supplemented pigs were packaged on trays with oxygen-permeable overwraps and half in modified atmosphere packs (initial gas mixture: O₂/CO₂/N₂ = 66/ 27/7). Meats were stored for 10 days at 7 °C in an illuminated retail display cabinet. The meat from vitamin E-supplemented pigs was more resistant to lipid oxidation than was the control meat. Gas packaging appeared to increase lipid oxidation in control meat, whereas lipid oxidation was stable in meat from vitamin E-supplemented pigs. Colour stability for gaspacked meat was comparable for both dietary groups. However, oxygen-permeable overwraps had a negative effect on colour stability in vitamin E-enriched meat. The reason for this is not known. The shelf-life of enriched and control meat was similar. Thus supplementation of pig feeds with vitamin E is recommended if an improved stability against lipid oxidation of (minced) pork is required.     

Aroma analysis of apple juice: Influence of salt addition on headspace volatile composition as measured by gas chromatography and corresponding sensory evaluations

Sensory response to the aroma of a food depends on the composition and concentrations of the volatiles of the headspace. When analyzing the headspace composition by gas chromatography, salts are often added to the sample as a means of increasing the concentration of the aroma compounds in the vapor phase (e.g. enrichment of the vapor phase). This will only give a correct impression of the original aroma when all volatile components are affected equally. In this study on apple juice aroma, it is demonstrated that the degree of headspace enrichment resulting from salt addition is different for esters, aldehydes and alcohols, In our collection system, the average degree of enrichment at 40°C (described in terms of Relative Peak Areas—RPA) was greater than 4 for alcohols, between 1·75 and 3·50 for aldehydes and less than 1·75 for esters. How these differences can be useful when trying to identify gas chromatography peaks is also discussed.Sensory evaluations showed that aroma response is changed when salt is added to the juice, resulting in an increased aroma intensity and off-aroma. Fruit aroma was not affected. A comparison of the sensory responses with headspace gas chromatographic measurements indicates that increase in off-aroma can be related to the increase in alcohol percentage in the headspace.From these results it can be noted that, when attempting to correlate sensory scores with aroma component concentrations as measured by headspace gas chromatography, it is most important that the test conditions utilized for each analysis correspond as closely as possible with each other.     

Control of spoilage microorganisms in minced pork by a self-developed modified atmosphere induced by the respiratory activity of meat microflora

The changes in microbial flora of minced pork during aerobic storage at 0, 5, 10 and 15 degrees C were studied. Minced pork samples (100g) were packed using two types of packaging films: (a) a common food film with high permeability (HPF) and (b) a film with low permeability (LPF). The respiratory activity of meat microflora and the use of a LPF resulted in a modified atmosphere in the package headspace developed during storage. Oxygen concentration decreased from 18.7% (after packaging) to 7% (after 15 days of storage) in packages with LPF, stored at 0 degrees C, while CO(2) increased from 3% to 10.5%, respectively. On the contrary, no significant atmosphere changes were observed during storage of HPF packages. The self-developed modified atmosphere in LPF packages resulted in a significant inhibition of pseudomonad growth which was more pronounced at low storage temperatures. For example, during storage at 0 degrees C, the growth rate of pseudomonads in meat packed with LPF was reduced by 48.7% compared to HPF. At 10 degrees C the latter reduction decreased to 13.7%. LPF packaging was also found to inhibit the growth of Brochothrix thermosphacta but this inhibition was weaker compared to pseudomonads. The effect of storage temperature on the growth rate of pseudomonads and B. thermosphacta in minced pork packed with the different films was modeled using an Arrhenius equation. For both bacteria, the activation energy was higher for LPF packaging. This can be attributed to the increased inhibitory effect of the modified atmosphere at lower storage temperature. The Arrhenius model was further used to evaluate the effect of temperature on the time required by the two bacteria to reach a spoilage level of 10(7)CFU/g. The results showed that when LPF packaging is combined with effective temperature control the time-to-spoilage can be significantly extended compared to HPF packaging.     

Effect of tocopherol concentration on rancidity development during frozen storage of a cured and an uncured processed pork product

This research evaluated the effect of addition during processing of various concentrations of tocopherol (0-1000 mg/kg) on the subsequent lipid oxidation and rancidity development during frozen storage of two pork products-a coarsely ground cured sausage and an uncured restructured pork roast. The results indicated that tocopherol had little effect on lipid oxidation, as measured by TBARS values and sensory evaluation during frozen storage at -18?°C for 37 weeks for either product. However, lipid oxidation only occurred to a limited extent even in products without tocopherol and was insufficient to cause rancid flavour development. It was, therefore, not possible to determine if tocopherol added during processing was effective as an antioxidant in preventing lipid oxidation in processed pork products during frozen storage.     

Influence of intramuscular fat content on lipid composition,sensory qualities and consumer acceptability of cured cooked ham

The present study is part of a project which aims to examine the influence of intramuscular fat (IMF) content on the sensory attributes and consumer acceptability of pork. An experiment was conducted to evaluate the influence of IMF level in muscle semimembranosus (SM) on the composition of its lipid fraction and on the sensory qualities and consumer acceptability of cured cooked hams. Thirty‐two carcasses were selected 24 h after slaughter from 125 Duroc × Landrace castrated male pigs showing large variability in SM muscle IMF content and were assigned to four IMF groups: ≤2%, 2–3%, 3–4% and >4%. Cured cooked ham slices were evaluated by a trained expert panel of 12 members and by a group of 56 consumers. Results from lipid analyses indicate that (i) an increase in IMF content was almost entirely reflected by an increase in the triglyceride content of the muscle and (ii) higher IMF levels were associated with higher free fatty acid and monoglyceride and lower cholesterol levels. The sensory evaluation of marbling significantly increased with IMF level, whereas other sensory qualities were unaffected. High IMF levels significantly depreciated the consumer perception of fat, aspect, taste and smell of ham slices. Overall, slices with the highest IMF levels got the least favourable rating by consumers. The present study indicates that increased IMF levels in muscle semimembranosus do not have significant effects on the sensory attributes of cured cooked hams, apart from the perception of marbling. However, high IMF levels have detrimental effects on the acceptability by consumers. © 2000 Society of Chemical Industry     

Humectants improve myosin extractability and water activity of raw, cured intermediate moisture meats

Glycerol, propylene glycol and sorbitol were incorporated into salt-based intermediate moisture meats manufactured from porcine M. longissimus thoracis and bovine M. biceps femoris by dry curing and air drying at 4°C. Moisture content and water activity (a(w)) in cured pork were reduced by the addition of propylene glycol and sorbitol. Propylene glycol was more effective than sorbitol in lowering a(w). The extractability of myosin heavy chain, used as an index of alteration of myofibrillar protein, decreased in intermediate moisture porcine meats with the addition of salt and was unaffected by sorbitol. However, use of glycerol and propylene glycol in cured and air-dried pork increased the extractability of myosin heavy chain. Whereas intact myofibrils could not be extracted from salt-cured, air-dried beef, myofibrils could be made from air-dried beef cured in the presence of 10% glycol, 5% propylene glycol and 4% sorbitol. Such myofibrils contracted immediately on addition of Mg(2+)-ATP. In addition, even after storafe for 5 months, including 30 days at 25°C, myosin heavy chain could be extracted from meat cured with this combination of humectants. In comparison with salt curing alone, curing meat with the above three humectants together, plus salt, results in intermediate moisture meats more like fresh meat.     

Effect of curing agents and water activity on pork muscle and adipose subcutaneous tissue lipolytic activity

The effect of chemical agents (salt, nitrate, ascorbic acid and glucose) and water activity (a_w) on pork muscle and adipose subcutaneous tissue upases and esterases has been studied. In muscle, salt above 20 g/L strongly inhibited neutral lipase and acid esterase but activated acid lipase. In adipose subcutaneous tissue, 7.5 g/L salt inhibited basic lipase and strongly inhibited acid esterase (around 40% recovery). Nitrate, ascorbic acid and glucose had a negligible or slightly inhibitory effect. A decrease in muscle a_w affected both neutral and basic lipase down to negligible activities at a_w=0.80. A decrease in adipose tissue a_w (down to 0.66) affected both acid and neutral esterase (around 40 and 65% of recovered enzyme activity, respectively). An in-vitro study representing three stages of the dry-curing process revealed that muscle acid lipase and acid esterase might play an important role throughout the process, whereas the rest of the studied enzymes in muscle would be less important. Neutral lipase might be the most important enzyme in the subcutaneous adipose tissue lipolysis of dry-cured ham.`

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Der Einfluß von Pökelhilfsstoffen und Wasseraktivität auf die Lipase-Aktivität in Muskeln und Fettgewebe von Schweinefleisch

Zusammenfassung Die Wirkung von Pökelhilfsstoffen (Salz, Nitrat, Ascorbinsäure und Glucose) und der Wasseraktivität auf die Lipase- und Esterase-Aktivität im Fettgewebe von Schweinefleisch wurde untersucht. Salz (20 g/L Lösung) hemmt die neutrale Lipase und saure Esterase sehr stark, während sie die saure Lipase fördert. In Fettgewebe hemmt Salz (7,5 g/L) die basische Lipase und die neutrale Esterase sehr stark (ca. 40%). Die Enzym-Aktivität wird von Nitrat, Ascorbinsäure und Glucose nicht beeinflußt. Bei Abnahme der Wasseraktivität (a_w=0,99–0,80) im Fleisch wird die Aktivität der neutralen und basischen Lipase sehr stark gehemmt. Bei Abnahme der Wasseraktivität (a_w=0,66) im Fettgewebe werden die Aktivitäten der sauren und der neutralen Esterase um ca. 40 und 65% verringert. Eine Untersuchung in vitro mit den drei Phasen des Reifens zeigt, daß die saure Lipase und die saure Esterase insgesamt in Fleisch eine wichtige Rolle spielen. Im Fettgewebe war die neutrale Lipase-Aktivität ca. 100%.

     

冷却猪肉供应链中微生物污染研究

研究冷却猪肉供应链的屠宰、运输、销售等过程中微生物的变化情况,分析各环节微生物污染的主要污染源,指出影响冷却猪肉安全的主要因素.