Species identification of commercial jerky products in food and feed using direct pentaplex PCR assay

Qualitative and Quantitative Detection of Mealworm DNA in Raw and Commercial Food Products Using Real-Time PCR

Considering food safety and an increasing public awareness of the ingredients, production process and origin of foods, the application of insects as food requires the development of tests for the reliable identification of their presence. The aim of the study was (1) the determination of appropriate modifications of the selected method for isolating the DNA of two life stages of mealworm, i.e., larva and adult, from commercial food products; (2) the determination of the method parameters for the qualitative and quantitative analysis of mealworm contents based on the detection of a species-specific mitochondrial DNA fragment, using real-time PCR; (3) the application of a method to test the commercial food products of mealworm. A total of nine species of adult insect were investigated (field cricket, Dubia cockroach, Madagascar cockroach, banded cricket, migratory locust, yellow mealworm, superworm, house fly and lacewing), theirlarvaes (yellow mealworms and superworms) and thirteen commercial food products (dried whole insects, powder and granules) representing various insect species and origins which were purchased from the European market. The obtained results showed that the efficiency of the modification of the DNA extraction method is dependent on the life stage of the mealworm. We proved the high sensitivity of the test, with the range of the method being 0.1–100%; we also proved the biological specificity in this range, and the linearity. The linearity of the test was also statistically verified using the Fisher–Snedecor test. One-way variance analysis showed statistically significant differences between the c_T values of the two mealworm life stages studied, and similarly, between the threshold cycle (c_T) values of adult forms. In contrast, for the inside group of mealworm larvae, there was no significant difference observed between the results of the c_T values. The test is effective for processed food products and may be used to monitor food. The research proved the suitability of the applied method for the analysis of samples that are commercially available as food for exotic animals. The hereby-developed method is based on widely used laboratory techniques, and does not require any additional investment in equipment. The availabilityof such a methodallows for the verification of the accuracy of the declared species component of the food products.

Development of a multiplex PCR assay for the simultaneous detection of big blue octopus (Octopus cyanea), giant Pacific octopus (Enteroctopus dofleini), and common octopus (Octopus vulgaris)

Since octopuses are similar in appearance and can be processed into various forms, seafood fraud has been reported. In this study, we developed the PCR assay to simultaneously detect three octopuses (big blue octopus, giant Pacific octopus, and common octopus). Specific primer sets were designed based on COI gene. We observed that the specific PCR amplicon sizes were 84 bp for big blue octopus, 117 bp for giant Pacific octopus, and 166 bp for common octopus, respectively. This assay was then used to test for specificity and did not show cross-reactivity with 15 cephalopods families. The limit of detection of the multiplex PCR assay was 0.1 pg. Subsequently, 30 commercial food products were then monitored to evaluate the applicability of this assay. All products were specifically amplified, and three octopus species of interest were distinguished. Therefore, this assay can be used as an octopus authentication tool in the seafood industry.

A Simple and Reliable Single Tube Septuple PCR Assay for Simultaneous Identification of Seven Meat Species

Multiplex PCR methods have been frequently used for authentication of meat product adulteration. Through screening of new species-specific primers designed based on the mitochondrial DNA sequences, a septuple PCR method is ultimately developed and optimized to simultaneously detect seven species including turkey (110 bp), goose (194 bp), pig (254 bp), sheep (329 bp), beef (473 bp), chicken (612 bp) and duck (718 bp) in one reaction. The proposed method has been validated to be specific, sensitive, robust and inexpensive. Taken together, the developed septuple PCR assay is reliable and efficient, not only to authenticate animal species in commercial meat products, but also easily feasible in a general laboratory without special infrastructures.

Selected Instrumental Techniques Applied in Food and Feed: Quality, Safety and Adulteration Analysis

This review presents an overall glance at selected instrumental analytical techniques and methods used in food analysis, focusing on their primary food science research applications. The methods described represent approaches that have already been developed or are currently being implemented in our laboratories. Some techniques are widespread and well known and hence we will focus only in very specific examples, whilst the relatively less common techniques applied in food science are covered in a wider fashion. We made a particular emphasis on the works published on this topic in the last five years. When appropriate, we referred the reader to specialized reports highlighting each technique's principle and focused on said technologies' applications in the food analysis field. Each example forwarded will consider the advantages and limitations of the application. Certain study cases will typify that several of the techniques mentioned are used simultaneously to resolve an issue, support novel data, or gather further information from the food sample.

Direct loop-mediated isothermal amplification (LAMP) assay for rapid on-site detection of Bifidobacterium longum subspecies longum, infantis, and suis in probiotic products

As interest in probiotics increases, the need for accurate description of probiotic compositions present in commercial products is also increasing. Since Bifidobacterium longum used as probiotics is labeled at species or subspecies levels, a detection method for distinguishing B. longum subsp. longum, infantis, and suis is needed. Thus, we designed three LAMP primer sets for B. longum subspecies. Each primer set was specific for the target subspecies. The detection level was 0.2 pg for each target DNA (about 10² CFU/mL). To apply these LAMP assays to on-site detection, a direct DNA extraction method was optimized and combined with LAMP assay. Finally, direct LAMP assays were used to monitor the presence of B. longum subspecies in 16 probiotic products. They could specifically and sensitively detect target subspecies within approximately 45 min. These rapid on-site detection methods are useful for identifying B. longum subspecies in probiotic products.

Specific DNA mini-barcoding for identification of Gekko gecko and its products

Background

The dry body of the Tokay Gecko (Gekko gecko) is the source of a valuable traditional Chinese medicine, it is therefore listed as a Class II protected animal species in China. Due to increasing market demand and a declining supply of the species, a considerable number of adulterants have emerged in the market. Thus, it is necessary to establish an accurate and rapid method of identification for distinguishing G. gecko from its adulterants and for separating it from highly processed products.

Methods

A total of 274 COI sequences were analyzed by using MEGA 5.0 software. Several specific primers were designed to amplify mini-barcode regions and identify G. gecko from its counterfeits and products.

Results

274 COI sequences of G. gecko and 15 adulterants species were analyzed. G. gecko could be distinguished from its adulterants through BLAST analysis, intra- and inter-specific distance analyses, and an NJ tree based on COI sequences. Two pairs of specific primers designed for this study, COISF2/COISR2 and COISF3/COISR3, amplified 200- and 133-bp fragments of the COI region, respectively, both of which were suitable for the identification of G. gecko and its adulterants. Furthermore, COISF3/COISR3 detected G. gecko in 15 batches of products.

Conclusion

Therefore, the specific DNA mini-barcoding method developed here may be a powerful tool for the identification of G. gecko and counterfeits, and may also be used to distinguish G. gecko from its highly processed by-products.

Fraud in Animal Origin Food Products: Advances in Emerging Spectroscopic Detection Methods over the Past Five Years

Animal origin food products, including fish and seafood, meat and poultry, milk and dairy foods, and other related products play significant roles in human nutrition. However, fraud in this food sector frequently occurs, leading to negative economic impacts on consumers and potential risks to public health and the environment. Therefore, the development of analytical techniques that can rapidly detect fraud and verify the authenticity of such products is of paramount importance. Traditionally, a wide variety of targeted approaches, such as chemical, chromatographic, molecular, and protein-based techniques, among others, have been frequently used to identify animal species, production methods, provenance, and processing of food products. Although these conventional methods are accurate and reliable, they are destructive, time-consuming, and can only be employed at the laboratory scale. On the contrary, alternative methods based mainly on spectroscopy have emerged in recent years as invaluable tools to overcome most of the limitations associated with traditional measurements. The number of scientific studies reporting on various authenticity issues investigated by vibrational spectroscopy, nuclear magnetic resonance, and fluorescence spectroscopy has increased substantially over the past few years, indicating the tremendous potential of these techniques in the fight against food fraud. It is the aim of the present manuscript to review the state-of-the-art research advances since 2015 regarding the use of analytical methods applied to detect fraud in food products of animal origin, with particular attention paid to spectroscopic measurements coupled with chemometric analysis. The opportunities and challenges surrounding the use of spectroscopic techniques and possible future directions will also be discussed.

Species Identification of Red Deer (Cervus elaphus), Roe Deer (Capreolus capreolus), and Water Deer (Hydropotes inermis) Using Capillary Electrophoresis-Based Multiplex PCR

To provide consumers correct information on meat species, specific and sensitive detection methods are needed. Thus, we developed a capillary electrophoresis-based multiplex PCR assay to simultaneously detect red deer (Cervus elaphus), roe deer (Capreolus capreolus), and water deer (Hydropotes inermis). Specific primer sets for these three species were newly designed. Each primer set only amplified target species without any reactivity against non-target species. To identify multiple targets in a single reaction, multiplex PCR was optimized and combined with capillary electrophoresis to increase resolution and accuracy for the detection of multiple targets. The detection levels of this assay were 0.1 pg for red deer and roe deer and 1 pg for water deer. In addition, its applicability was demonstrated using various concentrations of meat DNA mixtures. Consequently, as low as 0.1% of the target species was detectable using the developed method. This capillary electrophoresis-based multiplex PCR assay for simultaneous detection of three types of deer meat could authenticate deer species labeled on products, thus protecting consumers from meat adulteration.

Development of a Rapid On-Site Method for the Detection of Chicken Meat in Processed Ground Meat Products by Using a Direct Ultrafast PCR System

ABSTRACT

In this study, we developed a rapid on-site detection method by using direct ultrafast PCR coupled with a microfluidic chip to identify the presence of chicken meat in processed ground meat products. Chicken-specific PCR primer targeting mitochondrial 16S rRNA gene was newly designed, and its specificity was confirmed against 17 other animal species and 4 different chicken meat samples from different countries of origin. The sensitivity of the chicken-specific ultrafast PCR was 0.1 pg of chicken DNA. To evaluate the limit of detection of the direct ultrafast PCR method, different percentages of chicken meat mixed with pork or beef were prepared. The limit of detection of the direct ultrafast PCR method for the chicken meat-pork and chicken meat-beef mixtures was 0.1% for both raw meat and autoclaved meat. This method was used for 15 commercialized processed ground meat products. In this method, the target sequence was successfully amplified, and the presence of chicken meat in processed ground meat products was identified within approximately 25 min, including the time for sample preparation. Thus, our study shows that this developed direct ultrafast PCR method is a rapid and accurate method for on-site detection of chicken DNA in commercial food products.

HIGHLIGHTS

Development of RAPD-PCR assay for identifying Holstein, Angus, and Taiwan Yellow Cattle for meat adulteration detection

Incidents of food fraud have occurred worldwide, particularly in the form of meat adulteration. In this study, molecular probes were developed using the Random amplification of polymorphic DNA (RAPD) polymerase chain reaction (PCR) technique in order to identify three beef subspecies-Holstein, Angus, and Taiwan Yellow Cattle. Four RAPD-PCR 10-nucleotide primers were chosen out of a total of 60 primers. The selection was based on the reproducibility of species-specific amplicons able to detect various origins of cattle breeds. The results demonstrated that primer OPK12 produced three unique amplicons (1100 bp, 1000 bp and 480 bp) in Holstein; primer OPK14 generated one amplicon that only appeared in Holstein and Angus (200 bp); primer OPK19 amplified two species-specific amplicons in Holstein measuring 550 bp and 650 bp, respectively. However, due to the relatively lower repeatability of RAPD-PCR, higher and more specific testing repeats were required to increase the accuracy of the conclusion.

Simultaneous detection of fruit allergen-coding genes in tomato, apple, peach and kiwi through multiplex PCR

Fruit allergies have become more common in recent years, and are now a serious health problem. In this study, a multiplex PCR assay was used to detect potential fruit allergens causing food allergy labeling in Korea. For the detection of these allergens, specific primer pairs were designed to amplify the allergen-coding genes Cyclophilin (tomato), Mdtl 1 (apple), Pru p 2.01A (peach) and Pectin methylesterase inhibitor (kiwi), and primer pair targeting the 18S ribosomal RNA gene was additionally used as an endogenous control. Primer specificity was assessed with 23 plant species. A mixture of DNA from the four fruits was serially diluted and used to determine the sensitivity of the multiplex PCR assay, which was approximately 0.08 ng. Eleven commercial fruit products were evaluated to verify the applicability of the multiplex PCR assay. This assay is expected to be a specific and efficient method for detecting fruit allergens in foods.

Development of a fast real-time PCR assay based on TaqMan probe for identification of edible rice grasshopper (Oxya chinensis) in processed food products

Interest in using insects as an alternative source of food for humans is increasing. However, few analytical methods provide accurate information about the presence of insect species in processed foods. In this study, we developed a fast real-time PCR assay based on a TaqMan probe that can be performed within 40 min to detect edible rice grasshopper in commercial food products. A rice grasshopper-specific primer pair and probe targeting the cytochrome c oxidase subunit 1 (COI) gene were newly designed, having an amplicon size of 110 bp. The specificity of this primer pair and probe was verified using 19 insects and five crustaceans and no cross-reactivity was obtained against the non-target species. The absolute limit of detection (LOD) was 0.5 pg of rice grasshopper DNA, and as low as 0.1% of rice grasshopper was detected in raw, heat-treated, and autoclaved binary insect mixtures. To evaluate the effect of food matrix, binary mixtures containing rice grasshopper in wheat were used additionally, and at least 0.1% of target species was detected using this assay. The applicability of this assay was confirmed using nine commercial food samples labeled as containing rice grasshopper or locust. The fast real-time PCR developed in this study is a specific and sensitive method for identifying edible rice grasshopper in various food samples.

Rapid on-site detection of shrimp allergen tropomyosin using a novel ultrafast PCR system

Shrimp is seafood that can commonly trigger allergic reactions. In this study, the ultrafast real-time PCR assay with portable device was developed to detect a shrimp-derived major allergen, tropomyosin, without complicated DNA extraction. For shrimp allergen detection, a specific primer pair was designed based on the shrimp tropomyosin gene and 18S ribosomal RNA gene as internal control. Primer specificity was assessed using 8 common seafood species. Serially diluted shrimp DNA was used to determine the limit of detection of the ultrafast PCR system, which was approximately 3.2 pg. Twenty-three food samples containing shrimp were evaluated to verify the applicability of a direct ultrafast PCR method for detecting shrimp allergens without DNA isolation. It took less than 30 min from sample preparation-to-result analysis to detect shrimp DNA in raw and processed samples. Therefore, this PCR system can be effectively and conveniently utilized in the field to detect shrimp in various food products.

Solar Drying and Sensory Attributes of Eland (Taurotragus oryx) Jerky

A double-pass solar drier (DPSD) and a laboratory oven (LO) were used for thin-layer drying of eland and beef. Prior to drying, the physicochemical characteristics of the raw meat were determined, such as pH, dry matter content (%), Warner-Bratzler shear force (N), pigment concentration (mg·kg−1), weight loss during cooking (%), water holding capacity (%), colour (L,a,b), and crude fat content (%). Both meats were pretreated with traditional jerky marinade (TM), TM with fresh pineapple juice (TMP), TM with honey (TMH), and TM with Coca Cola© (TMCCL) and compared to an untreated control (C). The sensory properties of the eland and beef jerky were assessed in a two-stage process. The surface colour values of the jerky samples were measured in the CIE L⁎  a⁎  b⁎ colour space and the effect of the different pretreatments on the overall combined colour (ΔE) was calculated. Significant differences (p<0.05) between raw eland and beef samples were found in case of pH, pigment concentration, water holding capacity, crude fat content, and colour (L and b). Jerky from TMP pretreated meat had the highest scores for texture, colour, and taste. Generally, for both meats dried in both driers, TMH marinade was evaluated as the one with the highest total difference ΔE compared to meat dipped in TMP pretreatment, which had the lowest total difference ΔE.

Direct duplex real-time loop mediated isothermal amplification assay for the simultaneous detection of cow and goat species origin of milk and yogurt products for field use

A multiple loop-mediated isothermal amplification (LAMP) method was developed to detect cow and goat milk in the field using a portable fluorescence device. For rapid on-site detection, this duplex LAMP assay was used in combination with direct amplification, without DNA extraction. The cow- and goat-specific LAMP primer sets were designed based on the mitochondrial cytochrome b gene, and showed specificity against 13 other animal species in the reactions. The sensitivity of the duplex LAMP assay for cow and goat was 0.1 and 1 pg, respectively. The detection limit for both target species in milk mixtures was 2%. This assay successfully amplified and identified the two target species in 24 samples of commercial milk and yogurt products, with 30 min sampling-to-result analysis time. Therefore, this direct duplex real-time LAMP assay is useful for on-site simultaneous detection of cow and goat milk in commercial products, a capability needed to confirm accurate labeling.