DEHA-plasticized PVC for retail packaging of fresh meat

 A selection of frequently consumed meat products were packed in two commercial types of plasticized PVC film with declared plasticizer compositions of 11 and 21% di-(ethylhexyl)adipate (DEHA), respectively. The meat products were analysed for DEHA after packaging and storage until their “use by” date. Pretreatment of the meat, including cutting, chopping, cooking and packaging, was performed according to normal practice in a Danish supermarket. All samples contained DEHA. In general the investigation showed that a high fat content in or at the surface of the meat and/or a high storage temperature and/or repeated repackaging with new film during treatment gave rise to the greatest amount of DEHA migration from the film into the meat. No significant differences in DEHA migration could be seen when comparing the two films, although they were quite different in terms of plasticizer composition. The DEHA concentration at the “use by” date in fresh lean trimmings and slices of pork leg was 1 – 2 mg/kg, whereas neck and strip loin with some fat at the surface contained about 5 – 10 mg/kg. More fatty types of meat such as minced beef and pork with 18 – 20% fat, packaged once in plasticized PVC, contained around 20 mg DEHA/kg. When previously packaged loin was cut into steaks or chops, repackaged, minced and repackaged again, the DEHA concentration doubled to around 40 mg/kg. Finally if meatballs were then produced from the said mince, repackaged and stored at 65°C for 24 h, the DEHA concentration reached 100 mg/kg. Based on the evaluations of DEHA given by the EU Scientific Committee for Food, the National Food Agency considers concentrations of DEHA in foods higher than 18 mg/kg to be unacceptable. Received: 24 June 1997     

DEHA-plasticized PVC for retail packaging of fresh meat

 A selection of frequently consumed meat products were packed in two commercial types of plasticized PVC film with declared plasticizer compositions of 11 and 21% di-(ethylhexyl)adipate (DEHA), respectively. The meat products were analysed for DEHA after packaging and storage until their “use by” date. Pretreatment of the meat, including cutting, chopping, cooking and packaging, was performed according to normal practice in a Danish supermarket. All samples contained DEHA. In general the investigation showed that a high fat content in or at the surface of the meat and/or a high storage temperature and/or repeated repackaging with new film during treatment gave rise to the greatest amount of DEHA migration from the film into the meat. No significant differences in DEHA migration could be seen when comparing the two films, although they were quite different in terms of plasticizer composition. The DEHA concentration at the “use by” date in fresh lean trimmings and slices of pork leg was 1 – 2 mg/kg, whereas neck and strip loin with some fat at the surface contained about 5 – 10 mg/kg. More fatty types of meat such as minced beef and pork with 18 – 20% fat, packaged once in plasticized PVC, contained around 20 mg DEHA/kg. When previously packaged loin was cut into steaks or chops, repackaged, minced and repackaged again, the DEHA concentration doubled to around 40 mg/kg. Finally if meatballs were then produced from the said mince, repackaged and stored at 65°C for 24 h, the DEHA concentration reached 100 mg/kg. Based on the evaluations of DEHA given by the EU Scientific Committee for Food, the National Food Agency considers concentrations of DEHA in foods higher than 18 mg/kg to be unacceptable. Received: 24 June 1997     

Quantification of beef,pork, chicken and turkey proportions in sausages: use of matrix-adapted standards and comparison of single versus multiplex PCR in an interlaboratory trial

Quantitative PCR methods for the determination of beef, pork, chicken and turkey proportions in sausage were tested in an interlaboratory trial. Twelve different laboratories analysed six meat products each made of different compositions of beef, pork, chicken and turkey. Two kinds of calibrators were used: sausages of known proportions of meat and DNA from muscle tissue. Results generated using calibration sausages were more accurate than those resulting from the use of muscle tissue DNA. Regardless of the method used (either multiplex or single PCR), when using calibration sausages, it was always possible to quantify the proportions of meats in the unknown samples (in the range of 0.5–80%) with high precision and accuracy.     

The effects of various Chinese processing methods on the nutritional and safety properties of four kinds of meats

Chinese processed meat products are popular in the world, while different processing methods produce meats of different quality and safety. The aim of this work was to compare and evaluate the effects of seven Chinese processing methods (steaming, boiling, braising, pan-frying, frying, roasting and drying) on the nutritional and safety properties of four kinds of meats (beef, pork, chicken, duck). Comparing with the unprocessed raw meat, four kinds of meats treated with thermal processing displayed increased L^⁎ values, generally enhanced texture properties, decreased moisture contents, and increased protein contents. Among all the processing meats, the wet thermal processed meats exhibited relatively high total amino acid contents. Fatty acid contents showed the lowest value in boiled meats but relatively high values in fried, pan-fried and dried meats. For safety properties, thermal processing methods of pan-frying, frying and roasting caused mass formation of trans fatty acids and polycyclic aromatic hydrocarbons (PAHs). The highest PAHs contents were detected as 49.70 μg/kg in pan-fried beef, 18.18 μg/kg in fried pork, 11.02 μg/kg in roasted chicken and 15.24 μg/kg in fried duck, which were 14.34 times, 4.74 times, 7.50 times and 8.35 times of their corresponding blank control groups. When nutritional and safety properties are pursued, steaming and boiling are recommended for all the four kinds of meats. Besides, braising is also suitable for pork, while drying could also be used for chicken and duck.     

The extraction of yellow gentian root (Gentiana lutea L .)

 Several solvents have been investigated for the preparation of bitter compounds of gentian roots (Gentiana lutea L.) for food applications. The highest concentrations of the bitter compounds, amarogentin and gentiopicroside, were obtained with ethanol : water 55 : 45 (v/v), propylene glycol: water 30 : 70 (v/v) and ethanol: propylene glycol: water 20 : 20 : 60 (v/v/v). Enzyme treatment prior to solvent extraction gave a greater extract yield (3.5%) but the amarogentin and gentiopicroside concentrations remained the same. The volatile fraction was affected by the solvent used through the formation of esters of organic acids from the plant. Received: 22 January 1997 / Revised version: 18 March 1997     

Influence of heat treatment on carnosine, anserine and free amino acid composition of beef broth and its role in flavour development

 In an attempt to determine the most important free amino acids (FAAs) in the development of the flavour of beef broths, the amino acid compositions of beef broths prepared at different temperatures and cooking times, with flavours of different intensities, were studied. From our data, broths obtained at temperatures above 75  °C and cooking times longer than 120 min had significantly lower levels of most of the FAAs studied (P<0.05). Statistical analysis of the sensorial and analytical data (principal component analysis, chi-square analysis) permitted the different FAAs to be grouped in relation to the flavour. There was a significant association between elevated levels of glutamic acid, asparagine (P<0.01), lysine and methionine (P<0.05) and the development of beef broth flavour. However, this was inversely related to levels of cysteine, proline, serine, M-histadine, tyrosine, valine, arginine and aspartic acid whereas reduced levels of β-alanine, asparagine, tyrosine, threonine, methionine, cysteine, leucine, isoleucine, tryptophan, glutamic acid, histidine, lysine and phenylalanine were associated with sapid properties not characteristic of beef broths (astringent, warmed-over flavours). A significant correlation (P<0.01) between sensory evaluation and carnosine and anserine levels was also observed. Received: 29 December 1998 / Revised version: 29 April 1999     

Chemical analysis and significance of heterocyclic aromatic amines

 Levels of known heterocyclic amines vary from undetectable in many meats sold in fast food restaurants, to over 10 ng/g for meats prepared in restaurants that cook food to order, to hundreds of nanograms per gram for some meats cooked under certain home or laboratory conditions. To simulate the dry reactions that seem to occur at the meat surface we developed a model system to mimic these processes. Mixtures of free amino acids, creatinine and glucose, simulating the composition of beef or chicken, heated at 200  °C, form eight heterocyclic amines. Besides the commonly found 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-1,6-dimethylimidazo[4,5-b]pyridine, 2-amino-1,5,6-trimethylimidazo[4,5-b]pyridine and 2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine were also found. The calculated risk of consumption of heterocyclic amines is determined by the dietary dose, the extrapolation of carcinogenic potencies from rodents to humans, and the extrapolation of high rodent doses to low human exposures. Results suggest that DNA binding is linear with dose, but that the human DNA forms more adducts per unit dose than that of the rat. Altogether, the risk appears to be equivalent to that for many carcinogens that are regulated. Received: 23 April 1998     

Chemical analysis and significance of heterocyclic aromatic amines

 Levels of known heterocyclic amines vary from undetectable in many meats sold in fast food restaurants, to over 10 ng/g for meats prepared in restaurants that cook food to order, to hundreds of nanograms per gram for some meats cooked under certain home or laboratory conditions. To simulate the dry reactions that seem to occur at the meat surface we developed a model system to mimic these processes. Mixtures of free amino acids, creatinine and glucose, simulating the composition of beef or chicken, heated at 200  °C, form eight heterocyclic amines. Besides the commonly found 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-1,6-dimethylimidazo[4,5-b]pyridine, 2-amino-1,5,6-trimethylimidazo[4,5-b]pyridine and 2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine were also found. The calculated risk of consumption of heterocyclic amines is determined by the dietary dose, the extrapolation of carcinogenic potencies from rodents to humans, and the extrapolation of high rodent doses to low human exposures. Results suggest that DNA binding is linear with dose, but that the human DNA forms more adducts per unit dose than that of the rat. Altogether, the risk appears to be equivalent to that for many carcinogens that are regulated. Received: 23 April 1998     

Meat species identification and Halal authentication using PCR analysis of raw and cooked traditional Turkish foods

The method performance characteristics of commercially available PCR kits for animal species identification were established. Comminuted meat products containing different levels of pork were prepared from authentic beef, chicken, and turkey. These meat products were analysed in the raw state and after cooking for 20 min at 200 °C. For both raw and cooked meats, the PCR kit could correctly identify the animal species and could reliably detect the addition of pork at a level below 0.1%. A survey of 42 Turkish processed meat products such as soudjouk, salami, sausage, meatball, cured spiced beef and doner kebap was conducted. Thirty-six samples were negative for the presence of pork (< 0.1%) and four were found to be correctly labelled as containing pork. However, one sausage sample was labelled as containing 5% beef, but beef DNA was not detected and a meatball sample labelled as 100% beef was found to contain chicken. Another turkey meatball sample was predominantly chicken.     

Polycyclic aromatic hydrocarbons (PAHs) in traditional and industrial smoked beef and pork ham from Serbia

Smoked beef and pork ham samples were analysed during process of smoking (after packing and storing) for the presence of the 16 EU priority PAHs via Fast GC/HRMS method. This study showed that there are differences in PAH contents between final smoked beef ham samples from traditional smokehouse (TS) (3.9 μg kg⁻¹) and industrial smokehouse (IS), (1.9 μg kg⁻¹). Also there is a difference in PAH contents in final smoked pork ham samples (4.9 μg kg⁻¹, TS; 4.2 μg kg⁻¹, IS). In beef and pork ham samples from the same smokehouse different PAH contents were observed during smoking. The highest content of examined PAHs in all beef and pork ham samples during smoking showed benzo[c]fluorene (BcL) (beef ham: from 0.3 μg kg⁻¹ to 1.5 μg kg⁻¹; pork ham: from 0.2 μg kg⁻¹ to 2.1 μg kg⁻¹).The maximum level for benzo[a]pyrene (BaP) of 5 μg kg⁻¹ in smoked meat products was not exceeded in any samples. Correlation statistic analysis (P < 0.05) of obtained contents from samples both from TS and IS showed that BaP is a good marker both for 16 EU priority PAHs and 12 IARC probably and possibly carcinogenic PAHs (IS: R _BaP/Σ16PAHs = 0.95, R _BaP/Σ12PAHs = 0.96; TS: R _BaP/Σ16PAHs = 0.71, R _BaP/Σ12PAHs = 0.88).     

Variations in Radiation Sensitivity of Foodborne Pathogens Associated with the Suspending Meat

Longissimus dorsi from beef, pork, and lamb and turkey breast and leg meats were inoculated with Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus, and the gamma radiation resistance of the pathogens were determined under identical conditions. At 5°C the respective radiation D-values of E. coli O157:H7 and L. monocytogenes did not vary with the suspending meat. The D-value for a mixture of Salmonella spp. was significantly lower on pork than on beef, lamb, turkey breast, and turkey leg meats. The D-value for S. aureus was significantly lower on lamb and mechanically deboned chicken meat than on the other meats. All values were, nevertheless, within expected ranges.     

Solid phase extraction (SPE) method for detection of irradiated meats

Solid phase extraction (SPE) has been proposed as an alternative to the currently used florisil column chromatography. The hydrocarbons formed from beef, pork and chicken irradiated with 0-10 kGy were determined by the SPE and quantified by GC/MS. The limit of detection for the hydrocarbons in irradiated meats was 0.5 kGy. The correlation between the irradiation dose and the concentrations of hydrocarbons in beef, pork and chicken was high that linear regression coefficients (r²) were 0.87-0.99. SPE method would be used as the rapid detection of irradiated meats.     

Analysis of Pork Adulteration in Commercial Burgers Targeting Porcine-Specific Mitochondrial Cytochrome B Gene by TaqMan Probe Real-Time Polymerase Chain Reaction

A TaqMan probe real-time polymerase chain reaction assay was developed for the determination of pork adulteration in commercial burgers. The assay combined porcine-specific primers and TaqMan probe for the selective amplification and detection of a 109-bp fragment of swine cytochrome b (cytb) gene. Specificity test with 10 ng DNA of 11 different meat-providing animal and fish species yielded a quantification cycle (Cq) of 15.5 ± 0.20 for the pork and negative results for the others in a 40-cycle reaction with a change of analysts and sources. Analysis of beef burger formulations with spiked pork showed the assay can determine 100–0.01% contaminated pork with a PCR efficiency (E) of 93.8% and a correlation coefficient (R ²) of 0.991. A plot of actual value against real-time PCR-predicted value also yielded a good linear regression, R ² 0.998, and small root mean square error of calibration, RMSEC 0.42. A strong correlation was found between the partial least square (PLS)-predicted values and real-time PCR-determined values. The accuracy of the method was ≥90% in all determinations of the standard set. Residual analysis also revealed a high precision in all determinations. Finally, a random analysis of 10 ng DNA of commercial burgers from pork, beef, chicken, mutton, and chevon yielded a Cq of 15.56 ± 0.22 to 16.24 ± 0.35 from pork burgers, and negative results from the others, showing the suitability of the assay to determine pork in commercial burgers with a high accuracy and precision.     

Effect of cooking conditions on the flavour compounds and composition of shrimp (Parapenaeus longirostris) broth

 To achieve a shrimp broth with the best flavour, the whole shrimp must be cooked at 85°C for 30 min in a 0.5% NaCl solution in proportions 1 : 2 (w : v). Quantitatively, the main components of the broth were nitrogen substances, the most abundant of these being peptides of molecular weight less than 600 Da. Levels of ATP metabolites were also determined [the more abundant compounds were inosine, guanosine 5′-monophosphate (GMP) and inosine 5′-monophosphate (IMP)], as were free sugars (glucose, fructose and ribose) and fat content. The free amino acid composition was also determined. A significant correlation (P <0.0001) between cooking temperature and different nitrogen fractions was observed. Received: 22 September 1997 / Revised version: 13 November 1997     

Effect of gamma radiation on levels of α-tocopherol in red meats and turkey

The effect of low dose ionizing radiation on free α-tocopherol levels in beef, pork and lamb longissimus dorsi muscle and on turkey leg and breast muscle were determined. The samples were irradiated in air with a ¹³⁷Cs source at eight dose levels between 0 and 9.4 kGy at 5 °C. Irradiation resulted in a significant decrease in α-tocopherol levels in all of the meats studied. There were no statistically significant differences in the rate of loss of tocopherol due to species, with the exception of turkey breast. The rate of loss of tocopherol in turkey breast tissue was greater than the other meats. The information obtained in this study may be of use for ‘chemiclearance’ purposes since the relative effects due to species variation were examined.     

The effect of phytic acid on oxidative stability of raw and cooked meat

The effects of phytic acid addition (0.1, 1 and 5 mM) to pork and beef homogenates on TBARS and metmyoglobin levels in raw meat, and TBARS and heme iron contents in cooked meat during 3 days of storage at 4 °C were investigated. Also, the role of inositol as a potential synergist of IP₆ (phytic acid) was examined. IP₆ effectively decreased the TBARS accumulation in raw and cooked meat homogenates. The metmyoglobin formation was inhibited in raw beef by phytic acid in a dose-dependent manner. The effect of IP₆ was more pronounced in cooked meat than in raw and in cooked beef homogenates more than pork. Inositol did not enhance antioxidant action of phytic acid in minced meat.     

The effects of curing and cooking on the detection of species origin of meat products by competitive and indirect ELISA techniques

The purposes of this study were: (1) to develop and compare competitive and indirect enzyme linked immunosorbent assay (ELISA) methods for detecting species specific albumins in meat samples and (2) to examine the effect of curing and cooking on the identification of species origin of meats. Commercially obtained rabbit anti-pig serum albumin (anti-PSA) and rabbit anti-sheep serum albumin (anti-SSA) were affinity purified, and used to develop competitive and indirect ELISA procedures for PSA and SSA. The competitive ELISA procedures showed the lowest cross-reactivity with related serum albumins. Both ELISA procedures were capable of detecting as little as 5% pork or sheep in beef. Curing resulted in little or no inhibition in the ability of ELISA procedures to detect pork or sheep in beef. Cooking completely eliminated the ability of the competitive PSA ELISA to detect pork in beef, and of both SSA ELISA procedures to detect sheep in beef. Cooking also greatly reduced, but did not eliminate, the ability of the indirect PSA ELISA to detect pork in beef. Curing and cooking essentially eliminated the ability of the PSA ELISA procedure to detect pork in beef. Curing and cooking resulted in a 70 to 74% decrease in the signal of sheep meat in SSA ELISA procedures. These results demonstrated that competitive and indirect ELISA procedures are capable of determining the species origin of raw and cured meat. Heating raw or cured meats greatly reduced, but did not always eliminate, the ability of ELISA procedures to detect species origin of meats.     

The texture of low calorie grape juice jelly

 In this work the production of grape juice jellies with a low methoxyl pectin was studied. Availability of this kind of jelly will increase the range of dietetic products and is a promising alternative use for grapes surplus to the needs of the enological industry. The formulation of the jellies was optimized by response surface methodology (RSM), using as independent variables total sugar content (20 – 50°Brix), low methoxyl pectin content (0.5 – 1.5%) and processing temperature (55 – 90°C) at five levels. The dependent variable was the overall balance (B), a response obtained from sensory analysis. B was chosen from a series of sensory attributes evaluated by a test panel and the data treated by principal component analysis (PCA). The resulting polynomial equation (R ² = 0.92) showed the maximum value for B to occur for a jelly produced with 38°Brix of total sugar, 1.2% of low methoxyl pectin and a processing temperature of 69°C. The sensory-optimized jelly was objectively characterized for texture and dynamic rheological behaviour. Received: 2 October 1996 / Revised version: 7 January 1997     

Effect of electron-beam irradiation before and after cooking on the chemical properties of beef, pork, and chicken

Ground beef, pork, and chicken thigh meats were irradiated at 0 or 5.0kGy before and after cooking and then stored at -40°C in oxygen permeable bags. The pH, lipid oxidation, volatiles, and carbon monoxide production of the meat were determined at 0 and 6months of storage. The pH values of raw meats from different animal species were different (5.36-6.25) and were significantly increased by cooking, irradiation, and storage (p<0.05). Irradiation had no effect on the TBARS values of ground beef and pork, but significantly increased the TBARS of chicken thigh meat. Cooking, whether it was done before or after irradiation, caused significant increase in TBARS and was most significant in chicken and pork. The numbers of volatiles analyzed by GC/MS were higher in irradiated meats than the non-irradiated ones regardless of meat source. Sulfur-containing compounds were newly produced or increased by irradiation, but dimethyl disulfide and dimethyl trisulfide were not detected in the non-irradiated meats regardless of cooking treatment. Irradiation time, whether done before or after cooking, had little effect on the TBARS, volatiles, and carbon monoxide production in the meat.     

A comparison of the flavour volatiles from cooked beef and pork meat systems

The headspace volatiles from beef and pork cooked with and without added adipose tissue were entrained on Tenax GC before analysis by gas chromatography (g.c.) and combined gas chromatography-mass spectrometry. Lipid-derived volatiles dominated the headspaces of all samples and the only qualitative difference between beef and pork was an alkene of lipid origin which was peculiar to beef samples. A comparison of the areas of 37 g.c. peaks from replicate analyses of the different meat preparations using canonical variates and stepwise discriminant statistical techniques unambiguously distinguished the lean meats and the lean meats cooked with adipose tissue of either species. Adding adipose tissue to lean meat did not result in proportional increases in lipid-derived volatiles.