Detection of adulterants such as sweeteners materials in honey using near-infrared spectroscopy and chemometrics

Near-infrared (NIR) spectroscopy combined with chemometrics methods has been used to detect adulteration of honey samples. The sample set contained 135 spectra of authentic (n = 68) and adulterated (n = 67) honey samples. Spectral data were compressed using wavelet transformation (WT) and principal component analysis (PCA), respectively. In this paper, five classification modeling methods including least square support vector machine (LS-SVM), support vector machine (SVM), back propagation artificial neural network (BP-ANN), linear discriminant analysis (LDA), and K-nearest neighbors (KNN) were adopted to correctly classify pure and adulterated honey samples. WT proved more effective than PCA, as a means for variables selection. Best classification models were achieved with LS-SVM. A total accuracy of 95.1% and the area under the receiver operating characteristic curves (AUC) of 0.952 for test set were obtained by LS-SVM. The results showed that WT-LS-SVM can be as a rapid screening technique for detection of this type of honey adulteration with good accuracy and better generalization.     

Characterization and authentication of a novel vegetable source of omega-3 fatty acids,sacha inchi (Plukenetia volubilis L.) oil

Consumption of omega-3 fatty acids (ω-3’s), whether from fish oils, flax or supplements, can protect against cardiovascular disease. Finding plant-based sources of the essential ω-3’s could provide a sustainable, renewable and inexpensive source of ω-3’s, compared to fish oils. Our objective was to develop a rapid test to characterize and detect adulteration in sacha inchi oils, a Peruvian seed containing higher levels of ω-3’s in comparison to other oleaginous seeds. A temperature-controlled ZnSe ATR mid-infrared benchtop and diamond ATR mid-infrared portable handheld spectrometers were used to characterize sacha inchi oil and evaluate its oxidative stability compared to commercial oils. A soft independent model of class analogy (SIMCA) and partial least squares regression (PLSR) analyzed the spectral data. Fatty acid profiles showed that sacha inchi oil (44% linolenic acid) had levels of PUFA similar to those of flax oils. PLSR showed good correlation coefficients (R² > 0.9) between reference tests and spectra from infrared devices, allowing for rapid determination of fatty acid composition and prediction of oxidative stability. Oils formed distinct clusters, allowing the evaluation of commercial sacha inchi oils from Peruvian markets and showed some prevalence of adulteration. Determining oil adulteration and quality parameters, by using the ATR-MIR portable handheld spectrometer, allowed for portability and ease-of-use, making it a great alternative to traditional testing methods.     

Carbon footprint of Canadian dairy products: Calculations and issues

The Canadian dairy sector is a major industry with about 1 million cows. This industry emits about 20% of the total greenhouse gas (GHG) emissions from the main livestock sectors (beef, dairy, swine, and poultry). In 2006, the Canadian dairy herd produced about 7.7 Mt of raw milk, resulting in about 4.4 Mt of dairy products (notably 64% fluid milk and 12% cheese). An integrated cradle-to-gate model (field to processing plant) has been developed to estimate the carbon footprint (CF) of 11 Canadian dairy products. The on-farm part of the model is the Unified Livestock Industry and Crop Emissions Estimation System (ULICEES). It considers all GHG emissions associated with livestock production but, for this study, it was run for the dairy sector specifically. Off-farm GHG emissions were estimated using the Canadian Food Carbon Footprint calculator, (cafoo)²-milk. It considers GHG emissions from the farm gate to the exit gate of the processing plants. The CF of the raw milk has been found lower in western provinces [0.93 kg of CO₂ equivalents (CO₂e)/L of milk] than in eastern provinces (1.12 kg of CO₂e/L of milk) because of differences in climate conditions and dairy herd management. Most of the CF estimates of dairy products ranged between 1 and 3 kg of CO₂e/kg of product. Three products were, however, significantly higher: cheese (5.3 kg of CO₂e/kg), butter (7.3 kg of CO₂e/kg), and milk powder (10.1 kg of CO₂e/kg). The CF results depend on the milk volume needed, the co-product allocation process (based on milk solids content), and the amount of energy used to manufacture each product. The GHG emissions per kilogram of protein ranged from 13 to 40 kg of CO₂e. Two products had higher values: cream and sour cream, at 83 and 78 kg of CO₂e/kg, respectively. Finally, the highest CF value was for butter, at about 730 kg of CO₂e/kg. This extremely high value is due to the fact that the intensity indicator per kilogram of product is high and that butter is almost exclusively fat. Protein content is often used to compare the CF of products; however, this study demonstrates that the use of a common food component is not suitable as a comparison unit in some cases. Functionality has to be considered too, but it might be insufficient for food product labeling because different reporting units (adapted to a specific food product) will be used, and the resulting confusion could lead consumers to lose confidence in such labeling. Therefore, simple units might not be ideal and a more comprehensive approach will likely have to be developed.     

Method development for sensitive determination of nisin in food products by micellar electrokinetic chromatography

A rapid and sensitive micellar electrokinetic chromatography (MEKC) method has been developed for the identification and quantification of nisin in food products. Factors such as micelle concentration, pH, and concentration of the buffer were investigated in order to determine the optimum conditions for the analysis. Using optimised conditions of a background electrolyte containing 50 mM sodium phosphate, 80 mM sodium dodecyl sulphate (SDS) at pH 3.75 enabled the successful detection of nisin within 6 min. Limits of detection (LOD) and quantification (LOQ) were in the range of 0.3–0.8 and 1.0–2.8 mg L⁻¹, respectively. The calibration curves were linear for nisin concentration over the range of 2–60 mg L⁻¹. The relative standard deviation (RSD) of the peak area ratios and migration times for method repeatability (n = 3) were found to be lower than 5% and 1%, respectively. The potential of the proposed method to be used for quantitative determination of nisin concentrations in food materials was demonstrated by spiking food samples including dairy products, salad dressings, alcoholic beverages and canned tomatoes with known concentrations of nisin. Quantitative recoveries ranging from 83% to 104% were obtained in the food matrices.     

Analytical capabilities of inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometry (ICP-oa-TOF-MS) for multi-element analysis of food and beverages

Analytical capabilities of ICP-oa-TOF-MS for rapid, simultaneous and reliable determination of more than 50 major, trace and ultra-trace elements in different food and beverages samples (milk and dairy based products, cereals, meat, offal, sugar and sugar products, potatoes, fats, baby food samples, fruit juices, alcoholic beverages), following microwave closed vessel digestion of samples, were described. Under optimum instrumental conditions, and by using Rh as an internal standard and an external calibration method, ICP-oa-TOF-MS enables an accurate analysis, taking about one minute per a sample for all elements and isotopes of interest even for some elements such Zn, Ni, Cu, As or Co whose assay is more difficult when using conventional quadrupole instruments. In order to verify the accuracy and precision of the proposed method, 8 commercially available reference materials representing 3 major groups of food (milk and dairy based products, meat, cereals) were analysed, yielding results in agreement with certified values and the precision bellow 15%. In addition, accuracy was confirmed by spiked analytical recoveries study and accurate isotopic ratio determinations with the precision typically better than 5% with 5 s data acquisition period, also for other elements of interest whose content was not certified and different sample matrices. Limits of detection (3σ) have varied from 0.04 ng g⁻¹ for Th to 1630 ng g⁻¹ for Ca.     

光学快速分析技术在食品掺假检测中的应用

光学快速分析技术作为一种快速无损的检测技术已在食品行业中得到应用。文章综述近红外光谱、拉曼光谱、高光谱成像等光学快速分析技术在食品掺假检测中的应用,包括乳制品掺假、食用油掺假、肉制品掺假和其他食品掺假等方面,同时提出现阶段光学快速分析技术所存在的问题,并简要展望该技术在食品掺假检测领域的前景。     

Investigation of the migration of triclabendazole residues to milk products manufactured from bovine milk,and stability therein,following lactating cow treatment

Triclabendazole (TCB) is a flukicide used in the treatment of liver fluke in cattle; however, its use is currently prohibited in lactating dairy cows. In this study, following administration of 10% Fasinex (triclabendazole, Novartis Animal Health UK Ltd., Camberley, UK) the milk of 6 animals was used to manufacture dairy products, to ascertain if TCB residues in milk migrate into dairy products. The detection limit of the ultra-high-performance liquid chromatography-tandem mass spectrometry method used was 0.67 μg/kg. The highest concentrations of TCB residue measured, within the individual cow milk yield, was 1,529 ± 244 µg/kg (n = 6), on d 2 posttreatment. Days 2 and 23 posttreatment represented high and low residue concentrations, respectively. At each of these 2 time points, the milk was pooled into 2 independent aliquots and refrigerated. Milk products, including cheese, butter, and skim milk powder were manufactured using pasteurized and unpasteurized milk from each aliquot. The results for high residue milks demonstrated that TCB residues concentrated in the cheese by a factor of 5 (5,372 vs. 918 µg/kg for cheese vs. milk) compared with the starting milk. Residue concentrations are the sum of TCB and its metabolites, expressed as keto-TCB. Residues were concentrated in the butter by a factor of 9 (9,177 vs. 1,082 μg/kg for butter vs. milk) compared with the starting milk. For milk, which was separated to skim milk and cream fractions, the residues were concentrated in the cream. Once skim milk powder was manufactured from the skim milk fraction, the residue in powder was concentrated 15-fold compared with the starting skim milk (7,252 vs. 423 µg/kg for powder vs. skim milk), despite the high temperature (185°C) required during powder manufacture. For products manufactured from milk with low residue concentrations at d 23 posttreatment, TCB residues were detected in butter, cheese, and skim milk powder, even though there was no detectable residue in the milk used to manufacture these products. Triclabendazole residues were concentrated in some milk products (despite manufacturing treatments), exceeding residue levels in the starting milk and, depending on the storage conditions, may be relatively stable over time.     

Determination of synthetic phenolic antioxidants in food items using reversed-phase HPLC

A HPLC with gradient elution method for the determination of the synthetic phenolic antioxidants (SPAs) propyl gallate (PG), tertiary butyl hydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) in food items is described. A C18 column served as the stationary phase; the gradient elution was formed by acetonitrile and water:acetic acid (1%). The UV detector was set at 280 nm. Under the recommended conditions, separation of the four SPAs was achieved in less than 8 min. Analytical characteristics of the HPLC method such as limit of detection, linear range, and reproducibility were evaluated. Extraction parameters were optimized for the recoveries of the SPAs in different types of food items (cooking oil, margarine and butter, and cheese). Before the HPLC separation, the SPAs were extracted with methanol/acetonitrile (1:1, v/v) and were subjected to vortex/ultrasonic treatment. The extracts were next kept in a freezer (∼2 h) to precipitate co-extracted components. Recoveries of the SPAs when spiked to cooking oil, margarine, butter and cheese at 50 and 200 mg l⁻¹ were in the ranges 93.3–108.3% for PG, 85.3–108.3% for TBHQ, 96.7–101.2% for BHA and 73.9–94.6% for BHT. The method was applied to the determination of SPAs in 38 food items (16 cooking oils, ten margarine, six butter and six cheese samples). The levels of SPAs in positive samples are all below the legal limits of Malaysia.     

Robust new NIRS coupled with multivariate methods for the detection and quantification of tallow adulteration in clarified butter samples

Cows’ butterfat may be adulterated with animal fat materials like tallow which causes increased serum cholesterol and triglycerides levels upon consumption. There is no reliable technique to detect and quantify tallow adulteration in butter samples in a feasible way. In this study a highly sensitive near-infrared (NIR) spectroscopy combined with chemometric methods was developed to detect as well as quantify the level of tallow adulterant in clarified butter samples. For this investigation the pure clarified butter samples were intentionally adulterated with tallow at the following percentage levels: 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17% and 20% (wt/wt). Altogether 99 clarified butter samples were used including nine pure samples (un-adulterated clarified butter) and 90 clarified butter samples adulterated with tallow. Each sample was analysed by using NIR spectroscopy in the reflection mode in the range 10,000–4000 cm^?1, at 2 cm^?1 resolution and using the transflectance sample accessory which provided a total path length of 0.5 mm. Chemometric models including principal components analysis (PCA), partial least-squares discriminant analysis (PLSDA), and partial least-squares regressions (PLSR) were applied for statistical treatment of the obtained NIR spectral data. The PLSDA model was employed to differentiate pure butter samples from those adulterated with tallow. The employed model was then externally cross-validated by using a test set which included 30% of the total butter samples. The excellent performance of the model was proved by the low RMSEP value of 1.537% and the high correlation factor of 0.95. This newly developed method is robust, non-destructive, highly sensitive, and economical with very minor sample preparation and good ability to quantify less than 1.5% of tallow adulteration in clarified butter samples.     

Chemical, physical, and sensory properties of dairy products enriched with conjugated linoleic acid

Recent studies have illustrated the effects of cis-9,trans-11 conjugated linoleic acid (CLA) on human health. Ruminant-derived meat, milk and dairy products are the predominant sources of cis-9,trans-11 CLA in the human diet. This study evaluated the processing properties, texture, storage characteristics, and organoleptic properties of UHT milk, Caerphilly cheese, and butter produced from a milk enriched to a level of cis-9,trans-11 CLA that has been shown to have biological effects in humans. Forty-nine early-lactation Holstein-British Friesian cows were fed total mixed rations containing 0 (control) or 45 g/kg (on dry matter basis) of a mixture (1:2 wt/wt) of fish oil and sunflower oil during two consecutive 7-d periods to produce a control and CLA-enhanced milk, respectively. Milk produced from cows fed the control and fish and sunflower oil diets contained 0.54 and 4.68 g of total CLA/100 g of fatty acids, respectively. Enrichment of CLA in raw milk from the fish and sunflower oil diet was also accompanied by substantial increases in trans C18:1 levels, lowered C18:0, cis-C18:1, and total saturated fatty acid concentrations, and small increases in n-3 polyunsatu-rated fatty acid content. The CLA-enriched milk was used for the manufacture of UHT milk, butter, and cheese. Both the CLA-enhanced butter and cheese were less firm than control products. Although the sensory profiles of the CLA-enriched milk, butter, and cheese differed from those of the control products with respect to some attributes, the overall impression and flavor did not differ. In conclusion, it is feasible to produce CLA-enriched dairy products with acceptable storage and sensory characteristics.     

Fast chromatographic determination of caffeine in food using a capillary hexyl methacrylate monolithic column

Caffeine beverages are widely consumed in the world, so new analytical techniques providing fast and reliable data are essential for a rapid and accurate evaluation of food quality. A capillary hexyl methacrylate monolithic column was designed and prepared for simple, rapid, economical and sensitive high performance liquid chromatography method for the determination of caffeine in food, using a water/acetonitrile (90:10, v/v) mobile phase with ultraviolet (UV) detection. The method was validated over the range 0.16–250 μg/mL of caffeine concentration and found to be linear (r > 0.995, n = 5) with relative standard deviation (RSD) less than 4.0%.     

Concentrations of phytanic acid and pristanic acid are higher in organic than in conventional dairy products from the German market

Differentiation of organic and conventional dairy products is an important, yet difficult task in food authentication. In this study it was tested whether phytanic acid and pristanic acid can be used as markers for this purpose. Phytanic and pristanic acid cannot be de novo synthesised by mammals, and the predominant source for uptake is chlorophyll in food. Highest concentrations (but still in the sub-gram per 100 g lipids range) are found in ruminants because rumen bacteria are able to release phytol from chlorophyll and transforming it into phytanic acid. Degradation of phytanic acid leads to pristanic acid, and both fatty acids usually co-exist in biota. Owing to the unique source of grass-based feedstuffs in organic farming it was tested whether organic cheeses (n = 13) and other organic dairy products (n = 5) are higher in phytanic and pristanic acid concentrations than conventional products (n = 12). For this purpose, a sensitive gas chromatography–mass spectrometry method in the selected ion monitoring mode was developed.     

Rapid detection of the addition of soybean proteins to cheese and other dairy products by reversed-phase perfusion chromatography

The undeclared addition of soybean proteins to milk products is forbidden and a method is needed for food control and enforcement. This paper reports the development of a chromatographic method for routine analysis enabling the detection of the addition of soybean proteins to dairy products. A perfusion chromatography column and a linear binary gradient of acetonitrile-water-0.1% (v/v) trifluoroacetic acid at a temperature of 60°C were used. A very simple sample treatment consisting of mixing the sample with a suitable solvent (Milli-Q water or bicarbonate buffer (pH = 11)) and centrifuging was used. The method enabled the separation of soybean proteins from milk proteins in less than 4 min (at a flow-rate of 3 ml/min). The method has been successfully applied to the detection of soybean proteins in milk, cheese, yogurt, and enteral formula. The correct quantitation of these vegetable proteins has also been possible in milk adulterated at origin with known sources of soybean proteins. The application of the method to samples adulterated at origin also leads to interesting conclusions as to the effect of the processing conditions used for the preparation of each dairy product on the determination of soybean proteins.     

Using sweeping-micellar electrokinetic chromatography to determine melamine in food

This study developed a sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method for fast screening of melamine in food. In order to optimise parameters with multiple responses in parallel, face-centred cube central composite design (FCD) was employed to search for the optimum conditions of the sweeping-MEKC. The optimum background electrolyte was composed of 45 mM phosphoric acid and 175 mM sodium dodecyl-sulfate with the addition of 15% (v/v) methanol. Under such conditions, melamine content could be determined within 13 min with the limit of detection (S/N = 3) at 5 ng/mL. The developed method was validated by analysing melamine-spiked milk, gluten, chicken feed, and cookies. The proposed method was applied to determine melamine in different food products, with recoveries between 92.9 ± 3.3% and 108.4 ± 1.7%. The present study shows that the developed sweeping-MEKC method is sensitive, accurate, and efficient for fast screening of melamine in food.     

Characterization of aerobic spore-forming bacteria associated with industrial dairy processing environments and product spoilage

Due to changes in the design of industrial food processing and increasing international trade, highly thermoresistant spore-forming bacteria are an emerging problem in food production. Minimally processed foods and products with extended shelf life, such as milk products, are at special risk for contamination and subsequent product damages, but information about origin and food quality related properties of highly heat-resistant spore-formers is still limited. Therefore, the aim of this study was to determine the biodiversity, heat resistance, and food quality and safety affecting characteristics of aerobic spore-formers in the dairy sector. Thus, a comprehensive panel of strains (n = 467), which originated from dairy processing environments, raw materials and processed foods, was compiled. The set included isolates associated with recent food spoilage cases and product damages as well as isolates not linked to product spoilage. Identification of the isolates by means of Fourier-transform infrared spectroscopy and molecular methods revealed a large biodiversity of spore-formers, especially among the spoilage associated isolates. These could be assigned to 43 species, representing 11 genera, with Bacillus cereus s.l. and Bacillus licheniformis being predominant. A screening for isolates forming thermoresistant spores (TRS, surviving 100 °C, 20 min) showed that about one third of the tested spore-formers was heat-resistant, with Bacillus subtilis and Geobacillus stearothermophilus being the prevalent species. Strains producing highly thermoresistant spores (HTRS, surviving 125 °C, 30 min) were found among mesophilic as well as among thermophilic species. B. subtilis and Bacillus amyloliquefaciens were dominating the group of mesophilic HTRS, while Bacillus smithii and Geobacillus pallidus were dominating the group of thermophilic HTRS. Analysis of spoilage-related enzymes of the TRS isolates showed that mesophilic strains, belonging to the B. subtilis and B. cereus groups, were strongly proteolytic, whereas thermophilic strains displayed generally a low enzymatic activity and thus spoilage potential. Cytotoxicity was only detected in B. cereus, suggesting that the risk of food poisoning by aerobic, thermoresistant spore-formers outside of the B. cereus group is rather low.     

Rapid whole protein quantification of staphylococcal enterotoxin B by liquid chromatography

Food poisoning caused by Staphylococcus aureus is one of the most important foodborne diseases in the world. The ability of these bacteria to produce one or more enterotoxins in milk and dairy products is linked to staphylococcal food poisoning. Enterotoxin B (SEB) is an exotoxin produced by S. aureus and is one of the compounds most frequently involved in staphylococcal food poisoning worldwide. In this work, 20 samples of milk collected from restaurants have been studied for the presence of S. aureus enterotoxigenic strains. All the isolates from milk samples have been analysed by liquid chromatography-coupled with diode array detector for the rapid identification and quantification of SEB as intact protein. Limit of detection and limit of quantification values were 0.5 and 1 μg/mL, respectively. S. aureus was found in 35% of analysed samples but only one of them was an enterotoxigenic strain, which produced staphylococcal enterotoxin B at levels of 3.6 μg/mL.     

Systematic evaluation of pre-HPLC sample processing methods on total and individual isoflavones in soybeans and soy products

There are mainly two protocols in isoflavone analysis, one that involves hydrolysis prior to HPLC analysis and the other direct HPLC analysis. In this study, three different hydrolysis methods were systematically re-evaluated, and compared with direct HPLC analysis. Acidic hydrolysis (1.2-3 M HCl in ethanol at 80 °C) showed a maximum conversion of ca. 92% from glucosides to aglycones in 2 h; however, longer reaction caused degradation of genistein. Alkaline hydrolysis using 2 M NaOH converted acetylglucosides and malonylglucosides to their respective glucosides within 10 min. Glucuronidase from H. pomatia effectively converted isoflavone glucosides and acetylglucosides to aglycones. Quantification of the total isoflavones in various soy food products showed no significant difference among direct injection and the three hydrolysis methods (P < 0.05). We conclude that direct analysis of isoflavones in crude extracts is a rapid and accurate method to obtain isoflavone profiles and compositions in soybean, soy foods and beverages.     

High-power gradient diffusion NMR spectroscopy for the rapid assessment of extra-virgin olive oil adulteration

A high gradient diffusion NMR spectroscopy was applied to measure diffusion coefficients (D) of a number of extra-virgin olive, seed, and nut oils in order to ascertain the suitability of this rapid and direct method for discrimination of adulterated olive oils. Minimum adulteration levels that could be detected by changes in D were 10% for sunflower (SuO) and soybean oil (SoO), and 30% for hazelnut (HO) and peanut oil (PO). Qualitative and quantitative prediction of adulteration was achieved by discriminant analysis (DA). The highest prediction accuracy (98–100%) was observed only when two DA models were concomitantly used for sample classification. The first DA model provided recognition of high adulterated EVOO with more than 20% of SuO or SoO, and 30% with PO, whilst the second model could differentiate EVOO adulterated with 10% of SuO or SoO, and more than 30% of HO. The validation test performed with an independent set of randomly adulterated EVOO samples gave 100% classification success. The high accuracy levels together with minimal requirements of sample preparation, and short analyses time, prove the high-power gradient diffusion NMR spectroscopy as an ideal method for rapid screening of adulteration in valuable olive oils.     

Rapid detection of Listeria monocytogenes in food using culture enrichment combined with real-time PCR

A rapid method for the detection of Listeria monocytogenes in foods combining culture enrichment and real-time PCR was compared to the ISO 11290-1 standard method. The culture enrichment component of the rapid method is based on the ISO standard and includes 24 h incubation in half-Fraser broth, 4 h incubation in Fraser broth followed by DNA extraction and real-time PCR detection of the ssrA gene of L. monocytogenes. An internal amplification control, which is co-amplified with the same primers as the L. monocytogenes DNA, was also included in the assay. The method has a limit of detection of 1–5 CFU/25 g food sample and can be performed in 2 working days compared to up to 7 days for the ISO standard. A variety of food samples from retail outlets and food processing plants (n = 175) and controls (n = 31) were tested using rapid and conventional methods. The rapid method was 99.44% specific, 96.15% sensitive and 99.03% accurate when compared to the standard method. This method has the potential to be used as an alternative to the standard method for food quality assurance providing rapid detection of L. monocytogenes in food.