Heated Meat Products Research Articles

Assessment of total protein and soy protein contents in some heated meat products in Tehran, Iran

Heated meat products are emulsion which have various nutrition materials such as meat as an animal protein and soya as a plant protein. The nutritional value of meat proteins is very high than soya protein but the meat is more expensive than soya which the producers substitute the meat with soya. This study was assessed the soy protein and the total protein contents in some heated meat products collected from food stores in Tehran, Iran. Twenty samples of heated meat products with 40%, 55% and 70% of meat were randomly collected from food stores. The heated meat products samples were transferred to the food analysis lab. The total protein was determined by the macro Kjeldahl method after sample preparation and homogenization. Also, the soy protein content in samples was measured by using the enzyme-linked immunosorbent assay (ELISA) method. Results showed that 4 samples of heated meat products had less total protein content than the standard limit and 16 samples were in accordance with Iranian national standard. Soy protein content in 3 from 8 samples of heated meat products with 40% meat was higher than the standard limit and the others placed in the standard limit (approximate with 4% soy protein). Also, Soy protein content in 6 from 8 samples of heated meat products with 55% meat was higher than the standard limit and only 2 samples were in accordance with the standard limit. All samples of heated meat products with 70% meat set in a standard limit. It was concluded that some heated meat products do not correspond with the Iranian national standard range. The food quality control lab requires doing attention and sensation for correct formulation according to national standard measures.

Rapid determination of nitrosamines in sausage and salami using microwave-assisted extraction and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

In this study, an efficient, sensitive, and rapid method based on microwave-assisted extraction coupled with dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–mass spectrometry for determination and quantification of seven nitrosamines (NAs) in heated meat products (sausage and salami) was developed. At extraction stage, nitrosamines were extracted from sausage and salami samples with 10 mL of a hydrolyzing solvent using microwave at 500 MHz for 1.5 min. Effective parameters on DLLME, such as volumes of extraction and disperser solvents, pH, and salt addition, were optimized using response surface methodology based on central composite design. This technique provided acceptable repeatability in the range of 3.5–5.4 % for spiked samples. The recoveries of NAs were in the range 83.9–109.4 %. Limits of detection and limits of quantification for NAs in the real samples were within the ranges of 0.11–0.48 and 0.41–1.45 ng g−1, respectively. Good linear ranges were obtained for seven NAs in the range of 0.1–200 ng mL−1, with the coefficient (R 2) higher than 0.99. The merit figures, compared with other methods, showed that new proposed method is an accurate, precise, and reliable sample pretreatment method that substantially reduces sample matrix interference and gives very good enrichment factors (126–152).

Effect of radio-frequency on heating characteristics of beef homogenate blends

The heating characteristics of different lean-to-fat ratios in ground beef (90/10, 85/15, 80/20, 73/27) was investigated using radio-frequency (RF) heating of ground beef homogenates. A homogenate model system was prepared with ground beef in phosphate buffer (pH 6.0). Homogenate blends were packaged in vacuum bags, immersed in pre-heated water at 10, 25 and 50 °C, and heated in the RF equipment to a target temperature of 60 °C. Beef homogenate blends with more lean and less fat (90/10 and 85/15) heated more rapidly, reaching the target temperature faster than the higher fat composition blends. The RF heating rates of the beef homogenate blends varied with water temperature; higher temperature resulted in rapid RF heating. The RF heating rate at 50 °C was the most rapid in heating all homogenate blends. The instrumental color characteristics for RF heated homogenate blends exhibited lower L* and a* values than uncooked homogenate blends. RF heating resulted in reduced redness and more oxidation of myoglobin (metmyoglobin formation) and lesser oxy- and deoxy-myoglobin redox forms in all beef homogenate blends independent of the initial water temperature. The results present scope to explore short time heating processes which will minimize quality deterioration in RF heated meat products.

A Reliable Enzyme Linked Immunosorbent Assay for the Determination of Bovine and Porcine Gelatin in Processed Foods

Since gelatin-containing foods pose a risk for eliciting allergic reactions in sensitized individuals, a novel sandwich enzyme linked-immunosorbent assay (ELISA) for the detection and quantification of bovine and porcine gelatin in processed foods was developed. Rabbits and goats were immunized with bovine gelatin, and three antisera (pAb1 and pAb2 from rabbits, and pAb3 from goats) were obtained. We established a sandwich ELISA method based on a combination of these antibodies. In this study, two sandwich ELISA methods, rabbit pAb2-pAb1 and goat pAb3-pAb3, were evaluated for sensitivity, specificity, cross-reactivity, and applicability. Both ELISA methods were highly specific for bovine and porcine gelatin but had little reactivity with fish gelatin. The detection and quantification limits for porcine gelatin were found to be 0.78 ng/mL and 1.56 ng/mL, respectively. The established sandwich ELISA methods produced no false-positives, except for heated meat products or false negatives when various commercial foods were analyzed for their gelatin content. The rabbit pAb2-pAb1 ELISA cross-reacted with boiled squid, while the goat pAb3-pAb3 ELISA did not. Thus, the proposed goat pAb3-pAb3 ELISA method is a reliable tool for the detection of gelatin contaminants present in processed foods.

Role of proline and hydroxyproline in N-nitrosamine formation during heating in cured meat

N-Nitrosamines are formed in a multi-step reaction of nitrite with free amino acids and amines in the meat products. The aim of this study was to determine the role of proline and hydroxyproline in N-nitrosamines formation during heating of cured meat. A lean meat model was used with different nitrite concentrations (0, 120, and 480 mg/kg), and addition of proline and hydroxyproline (1000 mg/kg), followed by heating at different temperatures. Volatile nitrosamines were analyzed with GC-TEA. The nitrosamine content never exceeded 10 μg/kg and stayed <LOQ as long as the nitrite level of 120 mg/kg was not surpassed. The importance of proline as a precursor for N-nitrosamine formation was confirmed. In contrast, hydroxyproline inhibited NPYR formation ( N-nitrosopyrrolidine) because no traces were found after addition of hydroxyproline. NPYR formation was not related to nitrite, but was significantly influenced by temperature (⩾200 °C) and proline. NDMA-presence ( N-nitrosodimethylamine) in heated meat products was influenced by nitrite and temperatures >120 °C.

Western blot detection of brain material in heated meat products using myelin basic protein and neuron-specific enolase as biomarkers

An assay based on Western blotting and detection of central nervous system (CNS)-specific antigens was developed to detect brain tissue in processed (heated) meat products. Bands of antigen-bound primary antibodies were visualised through secondary anti-antibodies labelled with peroxidase, which generated chemiluminescence documented by a photographic film. Ponceau-S staining before antibody incubation and molecular mass information on detected antigens after immunoreactions added information supporting correct identification of brain tissue in the meat products. In this approach B50/growth-associated protein (B50), glial fibrillary acidic protein (GFAP), myelin basic protein (MBP), neurofilament (NF), neuron-specific enolase (NSE) and synaptophysin (Syn) proteins were detected in raw luncheon meat and a liver product enriched with brain tissue at a level of 5% (m/m). Only MBP and NSE were considered suitable biomarkers for detection of 1% (m/m) brain tissue in meat products pasteurised at 70 °C or sterilised at 115 °C. The use of an anti-monkey MBP instead of anti-human MBP enabled speciation of the CNS material whether from bovine and ovine brains or from porcine brain tissue. This immunoblot assay potentiates the analysis of approximately 70 samples within 8 h, including sample preparation and the simultaneous probing of NSE and MBP target antigens.

Rapid detection of chicken and turkey in heated meat products using the polymerase chain reaction followed by amplicon visualisation with vistra green

A rapid and highly specific assay suitable for the routine detection of turkey and chicken in processed meat products has been developed. Based on PCR amplification of species-specific amplicons with rapid visualisation using vistra green, the assay may be completed within 5 h of receipt of sample. DNA was isolated from meat samples by the use of Wizard DNA isolation technology and followed by DNA amplification in the polymerase chain reaction using species specific primers, chicken forward (CF), chicken reverse (CR), turkey forward (TF) and turkey reverse (TR): the production of an amplicon was detected after the end of the PCR in less than 5 min using vistra green and a fluorescence plate reader. The presence of fluorescence denoted the presence of the target species in the sample.

Immunohistochemical detection of brain tissue in heated meat products

Immunohistochemical methods were used to determine whether brain tissue could be detected in test batches of meat products prepared with known levels of this tissue (0, 1, 5, 10, or 20% bovine brain tissue or 5% porcine brain tissue). Four different, commercially-available antibodies were examined: anti-Neurofilament (anti-NF), anti-MyelinBasicProtein (anti-MBP), anti-NeuronSpecificEnolase (anti-NSE) and anti-GlialFibrillaryAcidicProtein (anti-GFAP). Results obtained with the four antibodies differed with the heat treatment applied to the products (pasteurisation or sterilisation). The amount of immunoreaction product in the raw meat product varied with the antibody, even when the sample contained the same amount of brain tissue. The staining pattern also varied with the antibody. Overall, the anti-MBP antibody proved to be most useful in detecting brain tissue in finely comminuted heated meat products.

Detection of Pork in Heated Meat Products by the Polymerase Chain Reaction

A new method for the specific, sensitive, and semiquantitative detection of pork (Sus scrofa) in heat-treated meat products has been developed. DNA was isolated from meat samples by using a DNA-binding resin and subjected to polymerase chain reaction (PCR) analysis. First, oligonucleotides yielding a specific 137-base-pair (bp) fragment from eucaryotic DNA amplified from a highly conserved region of the 18-S ribosomal gene was used to assess DNA quality. Second, the presence of pork DNA was determined with specific oligonucleotides yielding a 108-bp fragment amplified from the porcine growth hormone gene. The test detected pork in fresh or heated meat mixtures of pork in beef at levels below 2%. This approach was superior to commercially available immunological tests that were not able to detect levels of pork less than 20% in cooked meat or less than 10% in fresh meat.

Species differentiation of heated meat products by DNA hybridization

A method for quantitation of pork in heat-treated meat products is described. The procedure involves isolation of DNA from meat samples followed by a determination of the average size of DNA fragments by agarose gel electrophoresis. The DNA is then immobilized on nylon membranes and hybridized with a 32P-labelled probe made from genomic porcine DNA. The signal intensity from filter-bound DNA probe is determined by laser densitometry of the autoradiographs. Functional relationships between the signal intensity and the fragment size of the DNA as well as signal intensity and the amount of pork DNA have been established. Pork DNA can therefore be quantified using DNA standards with the same fragment size as the actual sample DNA. Samples of known composition and heat treatment have been investigated. The detection limit has been determined to approximately 0·1% pork in beef whereas for heat-treated samples the detection limit has been determined to approximately 0·5% pork in beef. Examples are given in which the present method has been applied on commercial canned and cold-stored foods. The results of the investigation indicate that the DNA-hybridization technique applying 32P-labelled probes can be used for quantitative determinations in quality control of heat-treated meat products.

Simple methods for quantifying mutagenic heterocyclic aromatic amines in food products

Two solid-phase extraction methods were developed for the determination of mutagenic heterocyclic aromatic amines in heated meat products. The copper phthalocyanine (CPC) tandem extraction was performed on coupled cartridges of diatomaceous earth and CPC-derivatized Sephasorb HP, followed by further clean-up on Sephasorb HP. Parts per billion levels of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and its homologs as well as 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), amino-alpha-carboline (A alpha C), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), harman (H) and norharman (NH) can then be simultaneously quantified by HPLC with UV detection. The propylsulfonyl silica gel (PRS) tandem extraction is a one-step clean-up method on coupled cartridges of diatomaceous earth and PRS, suitable for the determination of MeIQx, IQ and their homologs, as well as the glutamic acid pyrolysates 2-amino-6-methyldipyrido[1,2-a:3',2']imidazole (Glu-P-1) and 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2). 4,7,8-TriMeIQx or 7,8-DiMeIQx were used as internal standards. Four grams of sample or less are required for analysis. The recovery of the amines was between 46 and 83% and the detection limit was in the low p.p.b. range with coefficients of variation ranging between 5 and 18%. The major mutagenic contaminant found in meat extracts was MeIQx (from less than 1 to 44 p.p.b.), followed by 4,8-DiMeIQx (1.3-5 p.p.b.) whereas the major contaminant in fried meat was PhIP (23-48 p.p.b.), followed by MeIQx (5.1-8.3 p.p.b.), A alpha C (3.2-8.9 p.p.b.) and 4,8-DiMeIQx (1.3-2 p.p.b.). The co-mutagens NH and H were found in fried meat at levels of 8.7-19 p.p.b. and 3-4.8 p.p.b. respectively.

An efficient and convenient method for the purification of mutagenic heterocyclic amines in heated meat products.

A simple and efficient method for the purification of mutagenic heterocyclic amines from heated meat products has been developed. In only two steps, namely extraction of raw material on Kieselgur followed by medium pressure liquid chromatography on Sephasorb HP, very clean fractions with high recovery rates of mutagenic compounds were obtained, thus allowing isolation and quantitation by high performance liquid chromatography (HPLC) with UV detection. The method was validated on both food grade and bacterial beef extracts as well as fried beef. In 1-5 g samples of beef extracts, levels up to 70 p.p.b. (ng/g) of 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), 8-90 p.p.b. of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and up to 8 p.p.b. of 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) were determined. In fried beef, 1 p.p.b. of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 1 p.p.b. of MeIQx were measured. The quantitative results of beef samples were in agreement with results from determinations using immunoaffinity chromatography/HPLC or liquid chromatography coupled with mass spectrometry. MeIQx could be quantified in fried beef down to 1 ng/g of fresh beef material. According to assays performed with reference standards of tryptophan and glutamic acid pyrolysis products, the method could also be extended to quantitate other heterocyclic amines.

Effect of heterocyclic amines and beef extract on chromosome aberrations and sister chromatid exchanges in cultured human lymphocytes.

Two of the major bacterial mutagens formed in heated meat products, 2-amino-3-methylimidazo[4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline or the basic fraction of beef extract induced a low frequency of sister chromatid exchanges in human lymphocyte cultures in the presence of metabolic activation. Structural chromosome aberrations were not induced at comparable high concentrations in human lymphocytes with intact repair system, suggesting that repair or induction of point mutations are involved in the DNA-damaging effect of heterocyclic amines rather than structural chromosome aberrations. Accordingly it may be concluded that mammalian cells with both intact repair and enzyme systems are more relevant than bacterial systems for evaluating the carcinogenic potential of heterocyclic amines.

Purification of the food-borne carcinogens 2-amino-3-methylimidazo [4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in heated meat products by immunoaffinity chromatography.

A rapid and simple scheme has been developed for the isolation and purification of two of the major mutagenic heterocyclic amines formed in heated beef products by affinity chromatography using monoclonal antibodies which recognize 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Two cell lines producing IgG antibodies were established following fusion of Sp2 or P3x.63 myeloma cells with spleen cells of immunized BALB/cby mice. The antigen was bovine gamma globulin haptenized with 2-(3-carboxypropylthio)-3-methylimidazo-[4,5-f]quinoline. The antibodies were immobilized on CNBr-activated Sepharose 4B. IQ and MeIQx formed in heated beef products were partially purified by XAD-2 chromatography and then applied to the affinity columns. Purification by affinity chromatography was adequate for subsequent quantitative analysis by HPLC with UV detection. With this purification scheme as little as 1 g of beef extract or 15 g of fried beef could be assayed for IQ and MeIQx at the part per billion level. Both antibodies had similar affinity constants for IQ (9.3 X 10(6) and 6.7 X 10(6) M-1) and for MeIQx (7.1 X 10(5) and 2.7 X 10(5) M-1) and both were suitable for immunoaffinity purification of IQ from complex mixtures. MAb2 could be used as well to selectively remove MeIQx from meat products after partial purification by XAD-2. MAb1, despite having a 3-fold higher affinity than MAb2 for MeIQx, could not be used for affinity chromatography for this mutagen.

Comparative mutagenicity studies on fried minced beef, grilled sausage and grilled hamburgers

AbstractThe mutagenicity of the basic fractions of fried beef patties, grilled hamburgers and grilled sausages was determined in the Ames test using activation systems (S9‐mix) derived from untreated and Aroclor‐pretreated rats and hamsters, and from rats pretreated with 3‐methylcholanthrene or phenobarbitone. In order to indicate whether the mutagenic activity was due to the presence of thermally generated amino imidazo aza‐arenes of the type previously identified in heated meat products (i.e. 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ), 2‐amino‐3,4‐dimethylimidazo‐[4,5‐f]quinoline (MeIQ) and 2‐amino‐3,8‐dimethylimidazo[4,5‐f]quin‐oxaline), these compounds were assayed under the same conditions. The mutagenicity of the basic fractions of the cooked foods and of the three aza‐arenes varied with the activation system used. The activation patterns of the basic fractions from fried beef and grilled sausages resembled that of IQ, whereas that of grilled hamburgers was more similar to that of MeIQ. Interestingly the total mutagenic activity of fried beef patties was greater than that of grilled hamburgers.

Detection of wheat gluten, whey protein, casein, ovalbumin, and soy protein in heated meat products by electrophoresis, blotting, and immunoperoxidase staining

Description d'une methode d'electrophorese sur gel pour l'identification de proteines non carnees dans des systemes modeles de produits carnes. La limite de detection est de l'ordre de 0,1 %. Le test de coloration permet de trier les echantillons analyses, en fonction de la presence ou de l'absence de proteines non-carnees

Prediction of thiamine content in convective heated meat products

SummaryIt is reported that thiamine is one of the most heat labile water soluble vitamins. It is therefore important to control the destruction of this vitamin during heating, reheating and keeping warm of different food items.In this study the kinetics of thiamine degradation in ground meat were determined. The losses during roasting of a minced meat loaf under different air conditions in a forced convection oven were calculated by computer simulations. The actual losses were analysed by a chemical method. The kinetics were found to be approximately of first order. The time‐temperature curves and the thiamine degradation in the loaves roasted under fairly mild conditions were easier to predict than the ones roasted at higher air temperature. This is partly due to the formation of the crust which has different thermal properties and gives different chemical changes from the inner parts of the loaf. The humidity and the velocity of the air does not effect the crust formation as much as the air temperature. This fact limits the prediction of thiamine degradation to lower air temperatures.

Determination of soya protein in meat products by standard curves obtained from SDS gel electrophoresis

A method based on densitometry of sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoretograms has been developed for the assessment of soya protein in fresh and heated meat products that also contain other additives. The protein is extracted with 3% SDS and 3 % 2-mercaptoethanol in a tris/borate buffer, pH 8.2. The electrophoretic separation is carried out on gels containing 12% polyacrylamide and SDS, pH 9.18. The method shows reproducable results. Qualitative identification is possible in products heated to less than 100 °C in the centre with standard deviation ±0,6% when the addition of soya protein is 1–5%,and ±1,5% when the addition is higher. The electrophoretic method can presumably also be used for obtaining standard graphs for determination of casein.

Crossover electrophoresis with indirect immunofluorescence in the detection of soy protein in heated meat products

SummaryA new method based on crossover electrophoresis with indirect immunofluorescence for the identification of soy protein in heated meat products is described. The procedure demonstrates specific precipitation reactions between the antisera and soy protein, even when these are present at concentrations of 2.5% in meat products heated to the level of commercial sterility (125°C x 25 min).

Quantitative identification of soya protein in fresh and heated meat products

SummaryA method based on laser densitometry of polyacrylamide electrophoretograms of proteins extractable in 10 m urea is described for the quantitative identification of soya protein in fresh meat products and in those heat processed at 100°C for over 1 hr. Qualitative identification of soya protein remains possible in products heated to the level of commercial sterility (127°C for 24 min). It is suggested that the method could also be used for the assessment of other non‐meat proteins in meat products.