Porcine troponin I: a thermostable species marker protein

Double lateral flow immunosensing of undeclared pork and chicken components of meat products

Adulteration of meat products is a serious problem in the modern society. Consumption of falsified meat products can be hazardous to health and/or lead to violating religious dietary principles. To identify such products, rapid and simple test systems for point-of-need detection are in demand along with complex laboratory methods. This study presents the first double lateral flow (immunochromatographic) test system, which allows simultaneous revealing two prevalent types of falsifications-undeclared addition of pork and chicken components to meat products. In the proposed test system, porcine myoglobin (MG) and chicken immunoglobulin Y (IgY) were used as specific biomarkers recognizable by antibodies. Within the optimization of the analysis, the concentrations of the immune reagents and regimes of their application on the working membrane were selected, which provided minimal limits of detection (LODs) for both analytes. The developed test system enables the detection of MG and IgY with the LODs of 10 and 12 ng/mL, respectively, which accords to addition of 0.1% of the undeclared meat compounds. The applicability of the test system to control the composition of raw meat mixtures and cooked food products was confirmed. The developed approach can be considered as a promising tool for monitoring composition of meat products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05944-y.

Lateral Flow Test System to Control Total Content of Muscle Tissues in Raw Meat Products

Assessment of the composition of meat-containing products is the task in demand due to their frequent deviations from declared recipes. The paper presents the developed test system for immunochromatographic determination of total meat content. The assay is based on the simultaneous use of monoclonal antibodies, which specifically interacts with mammalian skeletal troponin I, and polyclonal antibodies, which specifically detect bird immunoglobulin Y. To integrate the detection of both types of meat by the same test strip, the antibodies are mixed in the analytical zone of the test strip and in complex with a gold nanoparticle label. The chosen ratios of the antibodies for both mixtures provide the same contribution of different types of mammalian and bird raw materials of muscle tissues to the label binding. The test system demonstrates suitability for products containing beef, pork, rabbit, lamb, chicken, and turkey meat. The minimal detectable content of meat in samples is 0.1%. The samples for the testing are diluted 100 times, thus eliminating matrix effects, and providing high reproducibility of the color intensity for extracts of different compositions. The obtained results allow the recommendation of the developed test system for rapid on-site control of meat products.

Thermal-Induced Autolysis Enzymes Inactivation, Protein Degradation and Physical Properties of Sea Cucumber, Cucumaria frondosa

The main objective is to effectively denature the autolysis enzymes of C. frondosa on the premise of avoiding the quality deterioration caused by overheating. The effects of the different thermal treatments (blanching at 40–80 °C for 45 min, boiling and steaming at 100 °C for 15–120 min) on the cooking yield, moisture content, protein degradation, texture, and enzyme inactivation were studied, and the inner relationship was investigated by multivariate analysis. The autolysis enzymes of C. frondosa were thermally stable and cannot be denatured completely by blanching. Boiling and steaming could efficiently inactivate the enzymes but overheating for 60–120 min reduced the cooking yield and texture quality. Boiling at 100 °C for 45 min was suitable for pre-treatment, with cooking yield of 70.3% and protein content of 78.5%. Steaming at 100 °C for at least 30 min was preferable for long-term storage and instant food, in which the relative activity was only 3.2% with better palatability.

Lateral Flow Immunoassay to Detect the Addition of Beef, Pork, Lamb, and Horse Muscles in Raw Meat Mixtures and Finished Meat Products

A lateral flow immunoassay for sensitive detection of skeletal troponin I (TnI) as a specific, thermostable marker of muscle tissue was developed. Due to the antibodies' choice, the assay specifically detects mammalian TnI (in beef, pork, lamb, and horse) but does not detect bird TnI (in chicken or turkey), thus enabling differentiation of these types of raw meat materials. The assay is based on a sandwich format of the analysis using gold nanoparticles as labels. The time of the assay is 15 min, and the TnI detection limit is 25 ng/mL. A buffer solution is proposed for efficient extraction of TnI from muscle tissues and from finished meat products that have undergone technological processing (smoking-cooking-smoking, cooking and smoking). The possibility of detecting beef addition in minced chicken down to 1% was demonstrated.

Immunochromatographic Detection of Myoglobin as a Specific Biomarker of Porcine Muscle Tissues in Meat Products

An immunochromatographic detection of myoglobin (MG) as a specific marker of porcine muscle tissue has been developed. The method is based on the sandwich lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as a label. The developed test system determines MG with a detection limit of 5 ng mL−1 within 15 min. A specific determination of porcine MG and no cross-reactivity with MG from other tested mammals and bird species was demonstrated. The test system is able to detect pork additives, as low as 0.01% (w/w), in minced beef. A technique of MG extraction from muscle tissue has been proposed which allows for rapid and efficient MG extraction from meat samples (within 20 min). The developed test system can serve as an effective means of controlling the authenticity and quality of meat products.

Current analytical methods for porcine identification in meat and meat products

Authentication of meat products is critical in the food industry. Meat adulteration may lead to religious apprehensions, financial gain and food-toxicities such as meat allergies. Thus, empirical validation of the quality and constituents of meat is paramount. Various analytical methods often based on protein or DNA measurements are utilized to identify meat species. Protein-based methods, including electrophoretic and immunological techniques, are at times unsuitable for discriminating closely related species. Most of these methods have been replaced by more accurate and sensitive detection methods, such as DNA-based techniques. Emerging technologies like DNA barcoding and mass spectrometry are still in their infancy when it comes to their utilization in meat detection. Gold nanobiosensors have shown some promise in this regard. However, its applicability in small scale industries is distant. This article comprehensively reviews the recent developments in the field of analytical methods used for porcine identification.

Development of qualitative and quantitative PCR analysis for meat adulteration from RNA samples

Total RNA samples were used to establish qualitative and quantitative PCR-based methods for assessing meat adulteration. The primers were designed based on the mRNA sequences of troponin I (TnI), mitochondrial ribosomal protein (MRP) and tropomodulin genes to distinguish chicken, pork, goat, beef and ostrich. There was no cross reaction between the primers, and the detection limit of the cDNA template was 0.01 and 20 ng in simplex PCR and multiplex PCR, respectively. In the low temperature storage test, the detection limits of cDNA template with 10 and 1 ng were determined at 4 °C and -80 °C. In quantitative assay, the precision of real-time PCR analysis expressed as a coefficient of variation (CV) ranged from 0.25% to 5.24% and the trueness, expressed as an error, ranged from 0.28% to 6.98% for adulteration. Thus, herein, we provided alternative tools for the assessment of meat adulteration using mRNA-based PCR methods.

Skeletal Muscle Troponin I (TnI) in Animal Fat Tissues to Be Used as Biomarker for the Identification of Fat Adulteration

In this study, the existence of skeletal muscle troponin I (smTnI), well-known as a muscle protein in fat tissues, and the utilization of smTnI as a biomarker for the identification of fat adulteration were investigated. A commercial antibody (ab97427) specific to all of animals smTnI was used in this study. Fat and meat samples (cooked and non-cooked) of pork and beef, and chicken considered as representative meats were well minced and extracted by heating and non-heating methods, and the extracts from fat and meat tissues were probed by the antibody used in both enzyme-linked immunosorbent assay (ELISA) and immunoblot. The antibody exhibited a strong reaction to all meat and fat extracts in ELISA test. On the other hand, the results of immunoblot analsis revealed a 23 kDa high intensity band corresponding to the molecular weight of smTnI (23786 Da). These results demonstrate that the existence of smTnI in all animal fat tissues. Since there are monoclonal antibodies specific to each species smTnI, smTnI in fat tissues could be used as a biomarker to identify or determine animal species adulterated in meat products. Therefore, an analytical method to identify fraudulent fat adulteration can be developed with an antibody specific to each species smTnI.

Genetic evidence of an Asian background in heteroplasmic Iberian cattle (Bos taurus): effect on food authentication studies based on polymerase chain reaction-restriction fragment length polymorphism analysis

This work was aimed at identifying nucleotide polymorphic sites in a 359 bp region of the cytochrome b (cytb) mitochondrial gene of Iberian cattle (Bos taurus). This region is widely used as target in polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) species identification studies in foodstuffs destined for human and animal consumption. Two different coexisting restriction patterns were observed in four of the six animals studied when the 359 bp DNA fragment was cleaved with PalI, HinfI, MvaI, RsaI, or MboI. The amplification of both genotypes with the mitochondrial-specific primers L14735 and H15149 revealed the absence of nuclear pseudo-cytb genes, confirming the existence of mitochondrial heteroplasmy. The two coexisting mtDNA fragments were selectively sequenced in PCR extracts in which one genotype predominated over the other, both exhibiting a sequence variation of 10.4%. From the 37 nucleotide mismatches observed between genotypes, 32 were transitions and five were transversions. While 31 of the nucleotide mismatches between genotypes resulted to be conservative at the amino acid level, six changes implied amino acid substitutions, five of them being located in the variable transmembrane region. Genetic analysis suggests the presence of an Asian background in the mitochondria of Iberian cattle: while one of the genotypes matched the published sequence for Bos taurus, the other genotype clustered with a B. primigenius indicus animal and close to an Asian Bos taurus animal. These results also suggest that a number of current PCR-RFLP species identification methods based on cytb sequences may not be reliable for the accurate detection and identification of bovine material: an alternative battery of enzymes consisting of MmeI, NlaIV, and AluI is proposed.

Caillary electrophoresis for the analysis of meat authenticity

In this overview, different meat authenticity issues are presented, as well as a wide variety of methods available for meat authentication. Unlike chromatographic, traditional gel electrophoretic, or immunological methods, which have been routinely used in analytical laboratories, the application of capillary electrophoresis (CE) is relatively new in solving meat authentication issues. Several unique CE applications based on meat protein fingerprinting are discussed for the analysis of meat species in unheated meat products. For protein data interpretation, pattern recognition is used to account for the natural variability present within the same meat species. While gel DNA-based methods are widely used for determining meat species in heat processed products, few DNA-based methods utilizing CE have been reported. Moreover, the methods reported are qualitative or semiquantitative. Thus, the need for quantitative competitive PCR CE methods in the determination of meat species is addressed. For the determination of meat extenders, CE methods were either protein-based or based on specific markers. Polyphenols are used as specific markers for soy detection and hydroxyproline is used as a specific marker for collagen determination. Finally, the potential of electrophoretically mediated miroanalysis (EMMA) for the detection of meat that may have been previously frozen and retailed as "fresh" is highlighted.

Monoclonal antibody-based sandwich enzyme-linked immunosorbent assay for sensitive detection of prohibited ruminant proteins in feedstuffs

Regulations aimed to control the epidemic of bovine spongiform encephalopathy have banned the use of certain animal products, i.e., ruminant meat and bone meals, in ruminant animal feeds. A sensitive enzyme-linked immunosorbent assay has been developed to detect prohibited bovine and ovine muscles in feedstuffs. The assay utilizes a pair of monoclonal antibodies (MAbs) against skeletal troponin I (TnI). MAb 5G9, specific to bovine and ovine TnI, was used as the capture antibody and the biotin-conjugated MAb 2G3, reacting to all heterologous TnI, was used as the detection antibody. Quantitative procedures were applied to samples containing 5, 0.5, and 0.05% (wt/wt) of heat-treated (132 degrees C/2 bar, 2 h) bovine and ovine meat meals in three different feeds, coexisting with porcine, chicken, or turkey meat meal. The presence of these nonprohibited species did not affect the detection of bovine and ovine meat meals in the feed samples (P > 0.05). Quantitative determinations of extractable bovine and ovine TnI, with a detection limit of 5.0 and 4.0 ng/ml, respectively, were achieved when the matching feed matrixes were used in the calibration curves. This new assay provides a rapid and reliable way to detect animal protein products containing a trace amount of bovine or ovine muscle tissue in feedstuffs.