Double-antibody based immunoassay for the detection of β-casein in bovine milk samples

The concentration of casein (CN) is one of the most important parameters for measuring the quality of bovine milk. Traditional approach to CN concentration determination is Kjeldahl, which is an indirect method for determination of total nitrogen content. Here, we described a double-antibody based direct immunoassay for the detection of β-CN in bovine milk samples. Monoclonal antibody (McAb) was used as capture antibody and polyclonal antibody (PcAb) labelled with horseradish peroxidase (HRP) as detection antibody. With the direct immunoassay format, the linear range of the detection was 0.1–10.0 μg mL⁻¹. The detection limit was 0.04 μg mL⁻¹. In addition, the concentration of β-CN in real bovine milk samples has been detected by the developed immunoassay. There was a good correlation between the results obtained by the developed technique and Kjeldahl method from commercial samples. Compared to the traditional approach, the advantage of the assay is no need of time-consuming sample pretreatment.     

Enzyme immunoassay for the detection of porcine gelatine in edible bird’s nests

Porcine gelatine is a common adulterant found in edible bird’s nests (EBNs) used to increase the net weight prior to sale. This study aimed to develop indirect enzyme-linked immunosorbent assays (ELISAs) for porcine gelatine adulteration using anti-peptide polyclonal antibodies. Three indirect ELISAs were developed (PAB1, 2 and 3), which had limits of detection (LODs) of 0.12, 0.10 and 0.11 µg g^–1, respectively. When applied to standard solutions of porcine gelatine, the inter- and intra-assays showed coefficients of variation (CVs) less than 20% and were able to detect at least 0.5 ng µg^–1 (0.05%) porcine gelatine in spiked samples. The proposed ELISA offers attractions for quality control in the EBN industry.     

Comparison of microbiological and HPLC – fluorescence detection methods for determination of niacin in fortified food products

A comparison has been made between results obtained by a recently published HPLC method, involving post-column reaction and fluorescence detection, with a microbiological assay using Lactobacillus plantarum. The HPLC method includes a modified acid hydrolysis extraction step (0.1 M HCl) and yields niacin values from fortified foods somewhat lower than by the microbiological assay. The most significant differences were observed for the cereal-based products. These differences arise principally from the lack of specificity of L. plantarum and from the stronger acid hydrolysis extraction conditions (1 M HCl) of the microbiological assay, which probably releases a part of the non-bioavailable niacin. Moreover by HPLC, excellent recoveries of added nicotinic acid and nicotinamide (95–100%) were obtained and better precision (RSDr=0.3–0.8%) was observed than from the micobiological assay.     

Comparison of headspace-SPME-GC–MS and LC–MS for the detection and quantification of coumarin,vanillin, and ethyl vanillin in vanilla extract products

A headspace-solid phase micro-extraction (HS-SPME) GC–MS method has been developed for the determination of coumarin, vanillin and ethyl vanillin in vanilla products. Limits of detection ranged from 1.33 to 13.2 ng mL⁻¹. Accuracy and precision data for the method were measured and compared to those obtained using LC-ESI-MS. A survey of 24 commercially available vanilla products was completed using both techniques. No coumarin was detected in any of the samples. Examination of the GC–MS chromatograms revealed the presence of 18 other flavor related compounds in the samples. The method validation and sample analysis data using HS-SPME-GC–MS were comparable to those obtained using the LC–MS method. Because the two methods are conceptually different from one another, both methods would not be subject to the same interferences. This would allow them to be used as confirmatory methods for each other.     

A new liquid–liquid extraction method for determination of 6 azo-dyes in chilli products by high-performance liquid chromatography

A liquid–liquid extraction method was developed for purifying and enriching the sample of 6 azo-dyes (including Para red, Sudan red G, Sudan I, Sudan II, Sudan III and Sudan IV) by formic acid and chloroform. The results indicated that formic acid can facilitate the solution of fat-soluble azo-dyes, which was helpful for the separation of the fat-soluble interferences from the samples. The extracting conditions of 6 azo-dyes were also optimised. And the proposed extraction method was evaluated by the determination of 6 azo-dyes in chilli products. The mean recoveries of 6 azo-dyes were from 94.1% to 99.2% for chilli powder and from 94.2% to 98.6% for chilli spice. The CCα and CCβ obtained for 6 azo-dyes were in the range of 1.7–2.1 and 2.8–3.4 μg/kg for chilli spice and chilli powder. The inexpensive and simple method was acceptable for routine monitoring 6 azo-dyes in chilli products.     

Assessment of liquid chromatography–tandem mass spectrometry approaches for the analysis of ceftiofur metabolites in poultry muscle

The use of cephalosporin antibiotics in veterinary practice is likely to play an important role in the development of β-lactam-resistant bacteria. To detect off-label cephalosporin antibiotic usage, an analytical method is needed that, besides the native compound, also detects their active metabolites. In this paper, the applicability of three approaches for the quantitative analysis of ceftiofur using LC–MS/MS is assessed, viz. (A) analysis of ceftiofur, desfuroylceftiofur and/or desfuroylceftiofur cystein disulfide, (B) derivatisation of ceftiofur metabolites to desfuroylceftiofur acetamide and (C) chemical hydrolysis using ammonia, to produce a marker compound for ceftiofur. We found that approach A was not suited for quantitative analysis of total ceftiofur concentration or for effectively detecting off-label use of ceftiofur. Approach B resulted in adequate quantitative results, but was considered a single compound method because it depends on cleavage of a thioester group, which is present in only a limited number of cephalosporin antibiotics. Approach C showed adequate quantitative results but, in contrast to approach B, it is applicable to a range of cephalosporin antibiotics. Therefore, it is applicable as a broad quantitative screening of cephalosporin compounds in poultry tissue samples to indicate off-label use of cephalosporins in poultry breeding. Based on this study, it was concluded that approach C is the most suitable to detect off-label use of a range of cephalosporin antibiotics.     

Dyeing behaviour of polyacrylonitrile fiber cured by enzyme for natural dye cochineal北大核心

In this paper, polyacrylonitrile fiber cured by enzyme was dyed by natural dye cochineal. The effect of pretreating agent and enzyme concentration, temperature, time and pH value was discussed. The conclusion was that ; the dye uptake of polyacrylonitrile fiber pretreated by benzyl alcohol was higher of that pretreated by ethylene glycol methyl ether, the dye uptake of polyacrylonitrile fiber cured by enzyme was highest when enzyme concentration was 5% and enzyme cure time was 50 h, as well as enzyme cure temperature was 40°C and pH value was 7. The water return rate of polyacrylonitrile fiber cured by enzyme was increased noteworthily.     

Salt-assisted liquid–liquid microextraction for the determination of iodine in table salt by high-performance liquid chromatography-diode array detection

2-Iodosobenzoate and N,N-dimethylaniline have been used at pH 6.4 for selective conversion of iodide to 4-iodo-N,N-dimethylaniline which was extracted with ethanol, when the phase separation occurred by addition of ammonium sulphate, a process called salt-assisted liquid–liquid microextraction (SALLME), and analysed by high-performance liquid chromatography-diode array detection. Iodate was reduced to iodide before derivatisation. The method has been optimised for extracting solvent, salt for phase separation, and reaction time. A linear calibration was obtained for 10 μg-10 mg L⁻¹ of iodide with correlation coefficient of 0.9989 and limit of detection of 3.7 μg L⁻¹. The SALLME produced 280-fold enrichment of the derivative. The commercial iodised table salt samples have been found highly inhomogeneous; the RSD in analysis of different aliquots of the same sample ranged 18.0-78.1%. The average recovery of spiked iodide to real samples was 98.4% with an average RSD of 7.9% (range 5.2-12.4%).     

Enrichment of gamma‐linolenic acid from fungal oil by lipases

Abstract

Two microbial lipases from Geotrichum spp and Rhizopus spp isolated previously in this laboratory and a commercial lipase from Candida cylindracea were evaluated as biocatalysts for the enrichment of gamma‐linolenic acid (GLA, 18:3 n‐6) from a fungal oil derived from Mucor spp. Lipase from Geotrichum spp, as compared to lipases from Candida cylindracea and Rhizopus spp was found to be most effective in the enrichment of GLA in unesterified fatty acids upon esterification of the fungal oil fatty acids with n‐butanol. The level of GLA in the unesterified fatty acid could be raised from 10.9 % in the starting material to about 30 % in the unesterified fatty acids after a reaction period of 4 h. Selective hydrolysis of the fungal oil using lipase from Rhizopus spp resulted in about 1.5‐fold enrichment of gamma‐linolenic acid in the unhydrolysed acylglycerols. The other Upases tested were ineffective in the enrichment of GLA by selective hydrolysis of the fungal oil triacylglycerols.     

Multi-residue method for the confirmation of four avermectin residues in food products of animal origin by ultra-performance liquid chromatography–tandem mass spectrometry

A confirmatory method was developed for the rapid determination of abamectin, ivermectin, doramectin and eprinomectin residues in various food products of animal origin, such as pork muscle, pork liver, fish and milk. Samples were homogenized, extracted and de-proteinized by acetonitrile, cleaned via two-step cleaning procedure using Bond Elut C₁₈ SPE columns and then alumina-N cartridges. All the four avermectin residues in different animal-food products were simultaneously separated and determined by ultra-performance liquid chromatography–electrospray ionization tandem mass spectrometry (UPLC–ESI–MS/MS) within 3.5?min. Data acquisition under positive ESI–MS/MS was performed by applying multiple reaction monitoring (MRM) for both identification and quantification, and mass spectrometric conditions were optimized to increase selectivity and sensitivity. The matrix-matched calibration curves for different matrices, such as pork muscle, pork liver, fish and milk, were constructed and the interference effect of different sample matrices on the ionization was effectively eliminated. The UPLC–MS/MS method was validated with satisfactory linearity, recovery, precision and stability. Matrix-matched calibration curves of abamectin, ivermectin, doramectin and eprinomectin in four different matrices were linear (r^{2 ?}≥?0.990, goodness-of-fit coefficients ≤12.8%) in the range 2.5–200?µg?kg^?1. The limits of detection and quantification for the four avermectins were in the range 0.05–0.68 and 0.17–2.27?µg?kg^?1, respectively. Recoveries were 62.4–104.5% with good intra- and inter-day precision. The method was rapid, sensitive and reliable, and can be applied to the quantitative analysis of avermectin residues in different animal-food products.     

Determination of trichothecenes in cereals and cereal-based products by liquid chromatography–tandem mass spectrometry

A sensitive, accurate and precise method for the simultaneous determination of nivalenol (NIV), deoxynivalenol (DON), T-2 toxin (T-2) and HT-2 toxin (HT-2) in different food matrices, including wheat, maize, barley, cereal-based infant foods, snacks, biscuits and wafers, has been developed. The method, using liquid chromatography coupled with atmospheric pressure chemical ionization triple quadrupole mass spectrometry (LC–APCI–MS/MS), allowed unambiguous identification of the selected trichothecenes at low µg per kg levels in such complex food matrices. A clean-up procedure, based on reversed phase SPE Oasis® HLB columns, was used, allowing good recoveries for all studied trichothecenes. In particular, NIV recoveries significantly improved compared to those obtained by using Mycosep® #227 columns for clean-up of the extracts. Limits of detection in the various investigated matrices ranged 2.5–4.0 µg kg^?1 for NIV, 2.8–5.3 µg kg^?1 for DON, 0.4–1.7 µg kg^?1 for HT-2 and 0.4–1.0 µg kg^?1 for T-2. Mean recovery values, obtained from cereals and cereal products spiked with NIV, DON, HT-2 and T-2 toxins at levels from 10 to 1000 µg kg^?1, ranged from 72 to 110% with mean relative standard deviation lower than 10%. A systematic investigation of matrix effects in different cereals and cereal products was also carried out by statistically comparing the slopes of standard calibration curve with matrix-matched calibration curve for each of the four toxins and the eight matrices tested. For seven of the eight matrices tested, statistically significant matrix effects were observed, indicating that, for accurate quantitative analysis, matrix-matched calibration was necessary. The method was applied to the analysis of 57 samples of ground wheat originated from South Italy and nine cereal food samples collected from retail markets.     

Growth promotion of Bifidobacterium species by poultry bone and meat trimming hydrolyzate

Abstract: The growth of bifidobacteria that are employed in the production of functional food is often slow or limited, even on synthetic media. In this study, we investigated whether a peptide hydrolyzate (functional animal protein [FAP]), from poultry bones and meat trimmings, could be a potential source of growth stimulators. The bifidogenic activity of FAP on 18 strains of Bifidobacterium species was assessed via 2 different techniques: turbidimetric measurements and a direct count by fluorescence microscopy. Growth experiments were performed in B12 broth as the basal medium, B12 broth supplemented with N‐acetylglucosamine, and B12 broth supplemented with FAP. FAP supplementation yielded the highest maximum optical density (OD) and count values. The use of the microscopic fluorescence counts allowed for better evaluation of the extent of growth and assessment of the viability of cells. FAP from poultry bones and meat trimmings has potential as a growth stimulator for different bifidobacteria of human origin. FAP is a promising ingredient for inclusion in industrial media that are used to culture probiotic strains, including bifidobacteria, because it supports growth very well and maintains cells at a high level of viability. Practical Application: Proteinaceous hydrolyzate can be considered a promising ingredient for industrial media that are used to culture probiotic strains, including bifidobacteria, because it improves bacterial growth and maintains cells at a high level of viability.     

Metal–organic framework for the extraction and detection of pesticides from food commodities

Pesticide residues in food matrices, threatening the survival and development of humanity, is one of the critical challenges worldwide. Metal–organic frameworks (MOFs) possess excellent properties, which include excellent adsorption capacity, tailorable shape and size, hierarchical structure, numerous surface-active sites, high specific surface areas, high chemical stabilities, and ease of modification and functionalization. These promising properties render MOFs as advantageous porous materials for the extraction and detection of pesticides in food samples. This review is based on a brief introduction of MOFs and highlights recent advances in pesticide extraction and detection through MOFs. Furthermore, the challenges and prospects in this field are also described.     

Metal–oxide–semiconductor resistive gas sensors for fish freshness detection

Fish are prone to spoilage and deterioration during processing, storage, or transportation. Therefore, there is a need for rapid and efficient techniques to detect and evaluate fish freshness during different periods or conditions. Gas sensors are increasingly important in the qualitative and quantitative evaluation of high-protein foods, including fish. Among them, metal–oxide–semiconductor resistive (MOSR) sensors with advantages such as low cost, small size, easy integration, and high sensitivity have been extensively studied in the past few years, which gradually show promising practical application prospects. Herein, we take the detection, classification, and assessment of fish freshness as the actual demand, and summarize the physical and chemical changes of fish during the spoilage process, the volatile marker gases released, and their production mechanisms. Then, we introduce the advantages, performance parameters, and working principles of gas sensors, and summarize the MOSR gas sensors aimed at detecting different kinds of volatile marker gases of fish spoiling in the last 5 years. After that, this paper reviews the research and application progress of MOSR gas sensor arrays and electronic nose technology for various odor indicators and fish freshness detection. Finally, this review points out the multifaceted challenges (sampling system, sensing module, and pattern recognition technology) faced by the rapid detection technology of fish freshness based on metal oxide gas sensors, and the potential solutions and development directions are proposed from the view of multidisciplinary intersection.     

Development of a genetic method for the identification of salmon,trout, and bream in seafood products by means of PCR–RFLP and FINS methodologies

In the present study, two alternative methods for identifying 13 salmon, trout and bream species were developed. Both of them are based on polymerase chain reaction (PCR) amplification of a cytochrome b gene fragment. Subsequently, different techniques were assayed to assign the PCR amplicons previously obtained to particular species. The first one is based on the restriction fragment length polymorphism (RFLP) and includes three endonucleases for generating species-specific restriction profiles, while the second one is based on the phylogenetic analysis of DNA sequences. The main novelty of this work lies in the applicability of the developed methods to all kinds of processed products, including those undergoing intensive processes of transformation, as for instance canned foods. Finally, the methods were applied to 25 commercial samples including some that had been subjected to intensive thermal treatment, allowing the detection of those incorrectly labeled (16%). Therefore, these methods are useful to check the fulfillment of labeling regulations for seafood products, verify the correct traceability in commercial trade, and for fisheries control.     

Quantitation of lysinoalanine in dairy products by liquid chromatography–mass spectrometry with selective ion monitoring

The unnatural amino acid lysinoalanine (LAL) has been identified in milk and cheese products by liquid chromatography mass spectrometry (LC/ESI/MS) with selective ion monitoring (SIM) of the 9-fluorenyl-methylchloro-formate (FMOC) derivative. LAL is not present in raw milk or derived from Mozzarella cheese; however, high amounts of LAL are found in calcium caseinate and milk powder. As expected, milk fortified with caseinate or whey protein powder produces cheese with higher LAL content. Our analytical procedure is based on the simultaneous detection of specific ion masses of the FMOC–LAL derivative and the N-ε-methyl-lysine internal standard. A linear relationship was observed within the 0.2–20 ppm concentration range, in addition to a high correlation coefficient and ∼3% relative standard deviation.     

Exploring the antioxidant potential of Teucrium polium extracts by HPLC–SPE–NMR and on-line radical-scavenging activity detection

Teucrium polium is a popular medicinal plant that is used in the daily diet and the in vitro and in vivo antioxidant potency of its extracts has been widely investigated. In the present work, polar extracts from T. polium were analyzed in terms of its composition and radical-scavenging activity with the employment of the state-of-the-art HPLC-SPE-NMR and HPLC-DPPH techniques in the search of new antioxidant agents for food industry. NMR and MS data revealed the presence of phenylpropanoid glycosides verbascoside and poliumoside, the flavones apigenin and its derivatives and two methoxyflavones. The on-line DPPH experiments showed that poliumoside is the most active component of the extracts and the antioxidant potential of T. polium polar extracts is mainly attributed to phenylpropanoid glycosides (66–80%). Our results suggested that T. polium extracts could be a promising source of natural antioxidants. This holistic approach also revealed that poliumoside or polar extracts of T. polium can be used in food industry as antioxidant agents with natural origin. The HPLC-SPE-NMR and HPLC-DPPH analysis of the extracts was performed for first time in the same device without any modification of the instrumentation, avoiding the need for isolation of the individual components.     

Feasibility of salivary α-amylases for detection of plate waste reuse

Recently, plate waste reuse has been highlighted as a social issue with regards to food safety management in Korean restaurants. However, it is hard to determine whether plate waste has indeed been reused. Therefore, this study examined salivary biomarkers to detect plate waste contaminated with saliva. To select the most appropriate salivary biomarker, we investigated the circadian rhythm and measurement variations of salivary chromogranin A (CgA), cortisol, and α-amylase (sAA). Foods were mixed with saliva and then the appropriate salivary biomarker was applied. sAA had the lowest coefficient variation and an effective circadian rhythm for detecting plate waste reuse. The sAA detection method in side dishes contaminated with saliva using a visible color reaction was applied. This could determine whether plate waste was reused in the field.     

Enrichment of Rice Bran Oil with ��-Linolenic Acid by Enzymatic Acidolysis: Optimization of Parameters by Response Surface Methodology

Lipase-catalyzed enrichment of rice bran oil with n-3 fatty acid in order to obtain a structured lipid containing essential fatty acids has been optimized by response surface methodology. In this process, α-linolenic acid was used as an acyl donor using lipase-catalyzed acidolysis in hexane in presence of immobilized lipase from Rhizomucor miehei. The effect of incubation time and temperature, enzyme concentration and substrates mole ratio and their complex interaction on percentage incorporation of n-3 fatty acid, ratios of saturated fatty acid to polyunsaturated fatty acids, monounsaturated fatty acids to polyunsaturated fatty acids and n-6 to n-3 (18:2 to 18:3) fatty acids have been studied using a central composite rotatable design of experiments. The results showed that at the optimum conditions such as reaction time 4.5 h and reaction temperature 37. 5°C, substrate ratio ranging from 1.0 to 1.9, enzyme concentration varying from 1.0% to 2.0% are needed to fulfill the conditions such as percentage incorporation of n-3 fatty acid ≤18%, ratio of saturated fatty acid to poly unsaturated fatty acid ≥0.42, ratio of mono unsaturated fatty acid to poly unsaturated fatty acid ≥0.8, and ratio of n-6 to n-3 ≥1.30.