Cholesterol determination in foods: Comparison between high performance and ultra-high performance liquid chromatography

Probiotic Viability and Bioactive Properties of Buffalo Yoghurt Produced Using High Cholesterol-Assimilating Probiotic Strains

BACKGROUND

This study aimed to produce yoghurt with reduced cholesterol levels, enhanced antioxidant activity and angiotensin-converting enzyme (ACE) inhibitory activity while maintaining acceptable health properties, using buffalo milk and probiotic microorganisms.

METHOD

Buffalo yoghurts were produced using three different probiotic strains, including Lactobacillus acidophilus, Lactiplantibacillus plantarum and Bifidobacterium lactis. ACE-inhibitor activities (%), antioxidant activities as DPPH (%), and cholesterol activities in HPLC of these yoghurts were determined during the 28-day storage period. In addition, probiotic microorganisms, total aerobic mesophilic bacteria and yeast mould were counted during storage.

RESULTS

The viability of probiotic microorganisms in buffalo yoghurts remained above 5 log CFU/g at the end of the storage period. Antioxidant activity ranged from 9.30% to 27.20%. Buffalo yoghurt is produced with Lpb. plantarum, which exhibited the highest viability (9.12 log CFU/g) and antioxidant activity values of 61.48%. Gastrointestinal digestion affected the antioxidant and ACE-inhibitor properties of the yoghurt samples. The highest ACE-inhibitory effect after gastric digestion on the 28th day was observed in yoghurt-produced Lpb. plantarum and B. lactis, with 24.30% and 25.14% values, respectively. Also, the ACE-inhibitory activity of the outer (OUT) phase for all yoghurt samples was higher than that of undigested samples. According to cholesterol peaks obtained in HPLC, the highest cholesterol assimilation was detected in yoghurt produced using Lpb. plantarum.

CONCLUSION

The data obtained from the study may contribute to research on the potential of probiotic microorganisms with cholesterol-assimilation ability and probiotic food products produced using them to reduce cholesterol risk.

Effects of derivatization coupled with GC-FID analysis of cholesterol in some bakery products

Cholesterol analysis by derivatization technique is a time consuming, costly, and complex process while analyzing cholesterol without derivation is a simple, and quick method.Researchers analyzed cholesterol using both derivatization and non-derivatization techniques successfully. The objective of this study was to investigate the effect of derivatization in cholesterol analysis particularly on bakery goods.The retention time of non-derivatized cholesterol (11.62 min) and non-derivatized α-tocopherol standard (11.60 min) was very close in HP-5 capillary GC column andthey eluted together while injected as mixed standard. As a result, cholesterol content determined by non-derivatized technique could be overestimated due to the presence of α-tocopherol inbakery products. The peak resolution (Rs) between derivatized cholesterol and derivatized α-tocopherol standard using the appliedgradient GC condition was 3.1 which is well separated (>1.5) based on AOAC guidelines. The derivatized gas chromatographic cholesterol analysis method was verified by limit of detection (LOD; 0.03 mg/100 g), limit of quantification (LOQ; 0.08 mg/100 g), linearity (R2; 0.999),precision (repeatability: relative standard deviation (RSD) 1.5 %; reproducibility: RSD 1.9 %), and accuracy (102.1 % recovery). The verified cholesterol analysis method was subsequently applied to determine cholesterol content in selected bakery items, yielding a range of 2.76 ± 0.06 mg/100 g (chrysanthemum bread) to 114.26 ± 4.72 mg/100 g (castella).

p-Thiocresol Functionalized Cesium Lead Bromide (PTC@CsPbBr3): A Fluorometric Sensing Probe for the Detection of Cholesterol

Inorganic halide-based perovskites (e.g., cesium lead bromide) are tremendously useful semiconducting materials due to their unique optoelectronic properties. However, degradation of these perovskites under humid conditions is one of the major drawbacks to prevent their wide applications. Herein, passivated cesium lead bromide nanoparticles are synthesized using p-thiocresol as a passivating ligand, and this stable version of perovskite is later applied successfully as a sensor probe towards cholesterol detection. The designed sensor can detect cholesterol with a lower detection limit of 0.24 ppm and a fast response time of 10 s. The mechanism of quenching PTC@CsPbBr3 upon the gradual addition of cholesterol is discussed. Further, the sensor is successfully applied in the detection of cholesterol in real samples (blood serum). This work presents PTC@CsPbBr3 as a novel sensing platform for detecting cholesterol well in biomedical applications.

A General Review of Methodologies Used in the Determination of Cholesterol (C27H46O) Levels in Foods

Cholesterol (C27H46O) is a lipid-derived substance found in lipoproteins and cell membranes. It is also one of the main sources for the production of bile acids, vitamin D, and steroid hormones. Today, foods are evaluated by consumers not only according to their taste and nutritional content but also according to their effects on consumer health. For example, many consumers choose foods according to their cholesterol level. The cholesterol in the food can directly affect the blood cholesterol level when consumed, which can lead to cardiovascular diseases. High levels of cholesterol can lead to diet-related human diseases such as cardiac arrest, paralysis, type II diabetes, and cerebral hemorrhage. In societies with high living standards, interest in and consumption of foods that lower or have low cholesterol levels have increased recently. Accordingly, efforts to increase the variety of foods with reduced cholesterol levels are on the rise. This has indirectly led to the accurate measurement of cholesterol levels in blood and food being of great importance. Classical chemical, enzymatic, colorimetric, polarographic, chromatographic, and spectrophotometric methods; enzymatic, nonenzymatic, and electrochemical sensors; and biosensors are used for the determination of cholesterol in foods. The purpose of this review is to reveal and explore current and future trends in cholesterol detection methods in foods. This review will summarize the most appropriate and standard methods for measuring cholesterol in biological components and foods.

Fe-Ni dual-single atoms nanozyme with high peroxidase-like activity for sensitive colorimetric and fluorometric dual-mode detection of cholesterol

Cholesterol is widely existed in nerve myelin sheath and various membrane structures, whose abnormal level would deteriorate human cells or even cause diseases. Herein, Fe-Ni dual-single-atom nanozyme was efficiently incorporated into N-doped carbon nanosheets (FeNi DSAs/N-CSs) by a simple calcination method. Its nanozyme activity and catalytic mechanism were investigated in details. The FeNi DSAs/N-CSs nanozyme showed superior peroxidase-like property, which was applied for the dual-mode determination of hydrogen peroxide (H2O2) and cholesterol. The colorimetric/fluorometric assays of H2O2 displayed the linear ranges of 1-50 mM and 5-40 mM with low limits of detection of 0.45 mM and 3.33 mM, respectively. In parallel, there exhibited the linear ranges of 0.5-5.0 mM and 0.25-5.0 mM for the colorimetric/fluorometric analysis of cholesterol, coupled with the limits of detection down to 0.19 mM and 0.044 mM, respectively. This work provided a rapid, cost-effectiveness and simple colorimetric/fluorometric method for sensitive dual-mode detection of cholesterol in human serum samples.

Optimization of the tandem enzyme activity of V-MOF and its derivatives for highly sensitive nonenzymatic detection of cholesterol in living cells

It remains a great challenge to properly design and synthesize single-component artificial tandem enzymes for specific substrates with high selectivity. Herein, V-MOF is synthesized by solvothermal method and its derivatives are constructed via pyrolyzing V-MOF in nitrogen atmosphere at different temperatures, which are denoted as V-MOF-y (y = 300, 400, 500, 700 and 800). V-MOF and V-MOF-y possess tandem enzyme-like activity, i.e. cholesterol oxidase-like and peroxidase-like activity. Among them, V-MOF-700 shows the strongest tandem enzyme activity for V-N bonds. Based on the cascade enzyme activity of V-MOF-700, the nonenzymatic detection platform for cholesterol by fluorescent assay can be established in the presence of o-phenylenediamine (OPD) for the first time. The detection mechanism is that V-MOF-700 catalyzes cholesterol to generate hydrogen peroxide and further form hydroxyl radical (•OH), which can oxidize OPD to obtain oxidized OPD (oxOPD) with yellow fluorescence. The linear detection of cholesterol ranges of 2-70 μM and 70-160 μM with a lower detection limit of 0.38 μM (S/N = 3) are obtained. This method is used to detect cholesterol in human serum successfully. Especially, it can be applied to the rough quantification of membrane cholesterol in living tumor cells, indicating that it has the potential for clinical application.

Non-enzymatic electrochemical determination of cholesterol in dairy products on boron-doped diamond electrode

Determination of cholesterol in food matrices is essential for quality control concerning the health of consumers. Herein, a simple electrochemical approach for cholesterol quantitation in dairy products is evaluated. The newly developed differential pulse voltammetric method using acetonitrile-perchloric acid mixture as a supporting electrolyte is statistically compared to GC-MS and HPLC-UV. Oxidation signals of cholesterol at +1.5 V and +1.4 V (vs. Ag/AgNO₃ in acetonitrile) provide detection limits of 4.9 µM and 6.1 µM on boron-doped diamond and glassy carbon electrodes, respectively. A simple liquid-liquid extraction procedure from dairy products into hexane resulted in a recovery rate of (74.8 ± 3.8)%. The method provides results in close agreement (at a 95% confidence level) with GC-MS, while HPLC-UV resulted in a significant difference in estimated cholesterol concentrations for all samples. This newly developed method is a simpler, faster and cheaper alternative to instrumentally demanding MS-based methods and clearly outperforms HPLC-UV.

Molecularly imprinted polymers via reversible addition-fragmentation chain-transfer synthesis in sensing and environmental applications

Molecularly imprinted polymers (MIP) have shown their potential as artificial and selective receptors for environmental monitoring. These materials can be tailor-made to achieve a specific binding event with a template through a chosen mechanism. They are capable of emulating the recognition capacity of biological receptors with superior stability and versatility of integration in sensing platforms. Commonly, these polymers are produced by traditional free radical bulk polymerization (FRP) which may not be the most suitable for enhancing the intended properties due to the poor imprinting performance. To improve the imprinting technique and the polymer capabilities, controlled/living radical polymerization (CRP) has been used to overcome the main drawbacks of FRP. Combining CRP techniques such as RAFT (reversible addition-fragmentation chain transfer) with MIP has achieved higher selectivity, sensitivity, and sorption capacity of these polymers when implemented as the transductor element in sensors. The present work focuses on RAFT-MIP design and synthesis strategies to enhance the binding affinities and their implementation in environmental contaminant sensing applications.

Enzyme-assisted ReMALDI-MS assay for quantification of cholesterol in food

Cholesterol is a vital building block for animal cell membranes and participates in the synthesis of various hormones. Accurate quantitation of cholesterol in food is crucial for healthy diets. Here, we describe an enzyme-assisted reactive matrix-assisted laser desorption/ionization mass spectrometry (ReMALDI-MS) assay for the quantification of cholesterol in food. First, cholesterol was converted to 4-cholesten-3-one using the cholesterol oxidase, and then reacted with a reactive matrix, 4-hydrazinoquinazoline (4-HQ), to form a hydrazone bond. Utilizing 4-HQ significantly improved the ionization efficiency of cholesterol, which possesses poor ionization efficiency in MALDI-MS, and no additional tedious derivatization/purification steps were needed. Thus, the proposed assay was successfully used for the quantification of cholesterol in bovine milk and cream. The standard recovery tests show a recovery range of 95.3-103.0% with a relative standard deviation of 0.3-3.1%. Therefore, the proposed enzyme-assisted ReMALDI-MS assay has great potential for quantification of cholesterol in other foods.

Dietary supplementation Eucommia ulmoides extract at high content served as a feed additive in the hens industry

Since numerous natural components in Eucommia ulmoides belong to phytoestrogen, its effect on hens production deserve more attention. To investigate the potential of E. ulmoides extract used as a feed additive, laying performance, egg quality, yolk cholesterol, yolk fatty acids, yolk fatty, yolk volatile components, albumen amino acids, plasma biochemical parameters, intestinal histology, and gut microbiota of hens (n = 120) were determined between basal diet (A) and dietary supplementation low (B), middle (C), and high (D) level E. ulmoides extract for 11 wk. When compared to A group, 2 percentage points elevation in laying rate was observed of D group. Significant up-regulation of immunoglobulin indexes and down-regulation of lipid related indexes in D group were also found if comparison with A group, suggesting that supplementation E. ulmoides extract at a relative high content benefited in immunity enhancing and blood-fat depressing. Meanwhile, obvious variation in albumen amino acids and yolk volatile compounds were inspected as dietary supplementation E. ulmoides extract, especially in D group, implied that the flavor of egg would change under high-level E. ulmoides extract treatment. Besides, villus height and villus height to crypt depth ratio of duodenum, jejunum, and ileum in D group were also significantly higher than that of in A group, indicating high-level E. ulmoides extract contributed to nutrient adsorption via intestinal histology changing. Moreover, the richness, diversity, and composition of gut microbiota in D group also significantly altered with a comparison of A group. These variation caused gut microbiota in D group major enriched in the KEGG pathway of insulin signing pathway, systemic lupus erythematosus, and bacterial invasion of epithelial cells, which were conducive to egg production elevation via facilitating nutrient adsorption, inflammation relieving, blood lipid amelioration, and insulin resistance alleviation. These results indicated that dietary supplementation E. ulmoides extract at high content could serve as a feed additive in the hens industry.

Innovative Non-Enzymatic Electrochemical Quantification of Cholesterol

The use of the Liebermann–Burchard reaction in this study has been explored in the development of a simple, reliable, and robust quantitative electrochemical method to assay cholesterol, and hence provide a good alternative to colorimetric methods. The optimization of batch mode operation for electrochemical oxidation of cholesterol in the Liebermann–Burchard reagents included the applied potential and acidic volume. Tested using chronoamperometry, the developed method showed a high sensitivity (14.959 μA mM⁻¹) and low detection limit (19.78 nM) over a 0.025–3 mM concentration range, with remarkable linearity (R² = 0.999), proving an analytical performance either higher or comparable to most of the cholesterol sensors discussed in literature. The influence of possible interfering bioactive agents, namely, glucose, uric acid, ascorbic acid, KCl and NaCl, has been evaluated with no or negligible effects on the measurement of cholesterol. Our study was directed at finding a new approach to chemical processing arising from the use of external potential as an additional level of control for chemical reactions and the transfer of electrons between surfaces and molecules. Finally, the optimized method was successfully applied for the determination of cholesterol content in real blood samples.

Photonic Crystal Effects on Upconversion Enhancement of LiErF4:0.5%Tm3+@LiYF4 for Noncontact Cholesterol Detection

Cholesterol is a vital compound in maintenance for human health, and its concentration levels are tightly associated with various diseases. Therefore, accurate monitoring of cholesterol is of great significance in clinical diagnosis. Herein, we fabricated a noncontact biosensor based on photonic crystal-enhanced upconversion nanoparticles (UCNPs) for highly sensitive and interference-free cholesterol detection. By compounding LiErF₄:0.5%Tm³⁺@LiYF₄ UCNPs with poly(methyl methacrylate) (PMMA) photonic crystals (OPCs), we were able to selectively tune the coupling of the photonic band gap to the excitation field and modulate the upconversion (UC) luminescence intensity, given the unique multi-wavelength excitation property of LiErF₄:0.5%Tm³⁺@LiYF₄. A 48.5-fold enhancement of the monochromatic red UC emission was ultimately achieved at 980 nm excitation, ensuring improved detection sensitivity. Based on the principle of quenching of the intense monochromic red UC emission by the oxidation products of 3,3',5,5'-tetramethylbenzidine (TMB) yielded from the cholesterol cascade reactions, the biosensor has a detection limit of 1.6 μM for cholesterol with excellent specificity and stability. In addition, the testing results of the as-designed biosensor in patients are highly consistent with clinical diagnostic data, providing a sensitive, reliable, reusable, interference-free, and alternative strategy for clinical cholesterol detection.

Effects of dietary supplementation with Ampelopsis grossedentata extract on production performance and body health of hens

To investigate the potential of Ampelopsis grossedentata extract used as a feed additive, laying performance, egg quality, yolk cholesterol, plasma biochemical parameters, intestinal histology, and gut microbiota of hens (n = 60) were determined between basal diet (CK) and dietary supplementation with A. grossedentata extract (RT) for 11 weeks. The laying rate in RT group was 6.3 percentage points higher than in CK group together with feed conversion rate decreasing. Significant upregulation of immunoglobulin indexes and downregulation of lipid-related indexes in RT group were also found in comparison with CK group, suggesting that dietary supplementation with A. grossedentata extract benefited in immunity enhancing and blood-fat depressing. Meanwhile, the villus height in duodenum and villus height to crypt depth ratio in duodenum and jejunum of RT group were significantly higher than that of CK group, indicating that dietary supplementation with A. grossedentata extract facilitated nutrient adsorption via intestinal histology changing. Moreover, the richness, diversity, and composition of gut microbiota in RT group significantly altered with a comparison of CK group, including beneficial bacterium and pathogenic bacterium, revealing that dietary supplementation with A. grossedentata extract could modify gut microbiota communities to affect intestinal adsorption and pathogen invasion. In addition, the lipid metabolism-related insulin signing pathway was significantly enriched by gut microbiota in RT group, which were conducive to egg production elevation via facilitating blood lipid amelioration and insulin resistance alleviation. These results provided a basis for A. grossedentata extract served as a feed additive in the hen industry.

Peanut and linseed oil emulsion gels as potential fat replacer in emulsified sausages

The study aimed to highlight the utilization of gelled emulsion (GE) systems containing peanut and linseed oils to replace beef fat partially or completely in emulsified sausages. Total fat content was reduced by up to 40% and energy content was lowered by up to 27% in reformulated products. Saturated fatty acids and cholesterol were successfully decreased while noticeable increments were provided in mono and poly-unsaturated fatty acids in sausages containing GE. Moreover, the reformulation procedure presented a good potential for increasing n-3 content, while lowering atherogenicity index, thrombogenicity index, and n-6/n-3 ratios. Although the incorporated GE resulted in color and texture alterations, it was effective to improve the technological attributes in terms of emulsion stability and cooking behaviors. In GE added samples, oxidative stability of final products decreased; however sensory features were acceptable. Overall results pointed out that GE systems could be successfully conveyed to emulsified sausage formulations to ensure a healthier lipid profile with good technological and sensory quality.

Cold-set or hot-set emulsion gels consisted of a healthy oil blend to replace beef fat in heat-treated fermented sausages

The current work aimed to investigate the utilization of gelled emulsion (GE) systems stabilized either with cold or hot gelation consisted of peanut and linseed oils as fat replacers in fermented beef sausages. The reformulation provided a healthier lipid profile, that led to decreasing total lipid content, cholesterol, and SFAs (from 46.6% to 23.5%) meanwhile increasing both MUFAs (from 47.3% to 51.0%) and PUFAs (from 4.7% to 25.4%) as well as improving nutritional ratios (ω-6/ω-3, PUFA/SFA, IA, and IT). Cold-set GE caused less significant changes in instrumental color and protected PUFAs compared with hot-set GE, whereas hot-set GE provided advantages over cold-set GE in terms of microstructure, purge loss, and sensory scores. Replacement of beef fat fully by a hot-set GE system instead of using a fat-GE mixture was effective in reducing oxidation. The results demonstrated that utilization of different GE systems can be an effective strategy to contribute to the development of lipid-modified fermented meat products.

Decrease of cholesterol content in milk by sorption onto β-cyclodextrin crosslinked with tartaric acid; considerations and implications

Elevated cholesterol intake can induce the development of cardiovascular diseases in man, especially with long term animal origin foods consumption. Therefore, this work deals with the possibility of cholesterol content decrease in milk applying β-cyclodextrin crosslinked with tartaric acid (βCDcTA) as a removal agent. Evaluation of statistic data on food consumption in the Slovak Republic in 2018 aimed at total cholesterol daily intake and effects of “milky” cholesterol content decrease on total cholesterol balance. During the experiments, various amounts of βCDcTA addition to milk were studied resulting in optimal 5 % addition resulting in the cholesterol content decrease by 85.4 % in comparison to original cholesterol content. For monitoring purposes, an HPLC method analysing cholesterol content in saponified milk was employed. The food consumption data analysis showed that total per capita daily cholesterol intake was 369.8 mg, from which 86 mg was assigned to the cholesterol contained in milk and dairy products while the application of cholesterol removal procedure could decrease the total per capita daily cholesterol intake to 296.3 mg (“milky” cholesterol amount equal to 12.6 mg), which in below the recommended value of 300 mg daily intake still valid in the Slovak Republic. This approach might prove as a meaningful step to weaken health problems associated with high long term intake of cholesterol contained in foods of animal origin.

Characterization of lipid profiling in three parts (muscle, head and viscera) of tilapia (Oreochromis niloticus) using lipidomics with UPLC-ESI-Q-TOF-MS

A lipidomic evaluation was performed on the tilapia muscle, head and viscera, including studying the composition, distribution and stereospecific characteristics of fatty acids and lipid species. The head and viscera lipids were significantly richer than the muscle lipids. Triacylglycerols were the predominant fraction (over 80% of total lipid in the muscle and head). Additionally, polyunsaturated fatty acids had higher percentages in phospholipids (30.35-52.05% of total fatty acids) than in triacylglycerols (18.11-25.15%). The C52:2 and C52:3 were the most abundant triacylglycerols, which indicates the potential application in infant food. Moreover, 622, 530 and 513 lipids were identified using ultraperformance liquid chromatography-quadrupole time-of-flight-mass spectrometry in the muscle, head and viscera, respectively. The three tilapia parts were distinguished using multivariate analysis. Five fatty acids and 33 lipid species were considered as the potential biomarkers. This comprehensive analysis will help to evaluate the lipid nutritional values and facilitate exploitation in tilapia consumption and processing.

On-Site Colorimetric Detection of Cholesterol Based on Polypyrrole Nanoparticles

Herein, we report a facile method for cholesterol detection by coupling the peroxidase-like activity of polypyrrole nanoparticles (PPy NPs) and cholesterol oxidase (ChOx). ChOx can catalyze the oxidation of cholesterol to produce H₂O₂. Subsequently, PPy NPs, as a nanozyme, induce the reaction between H₂O₂ and 3,3',5,5'-tetramethylbenzidine (TMB). Under optimal conditions, the increase is proportional to cholesterol with concentrations from 10 to 800 μM in absorbance of TMB at 652 nm. The linear range for cholesterol is 10-100 μM, with a detection limit of 3.5 μM. This reported method is successfully employed for detection of cholesterol in human serum. The recovery percentage is ranged within 96-106.9%. Furthermore, we designed a facile and simple portable assay kit using the proposed system, realizing the on-site semiquantitative and visual detection of cholesterol in human serum. The cholesterol content detected from the portable assay kit were closely matching those obtained results from solution-based assays, thereby holding great potential in clinical diagnosis and health management.

Quality control and evaluation of Inonotus obliquus using HPLC method with novel marker compounds

Current quality control ofInonotus obliquusrequires chromogen complex content limit of 10% in accordance with the State Pharmacopoeia of the Union of Soviet Socialist Republics. However, this causes ambiguous results, impeding precise quality control. To improve ambiguous quality control criteria, this study developed a new HPLC method using two novel marker compounds (inotodiol and 3β-hydroxylanosta-8,24-dien-21-al) to control the quality control ofI. obliquus. The HPLC analysis was carried out in a C18 column with an isocratic elution of 95% acetonitrile at 210 nm. The developed method validated in terms of linearity, precision, accuracy, and recovery. The content criteria were established by the linear regression method and relative standard deviation method. As the results of the quantitative monitoring, 1.165 mg/g of inotodiol and 1.717 mg/g of 3β-hydroxylanosta-8,24-dien-21-al, calculated by the relative standard deviation method, were suggested new quality criteria. A new HPLC method was developed to improve current quality control ofI. obliquusand new lower content criteria were proposed as a result of quantitative monitoring.

Graphical abstract

Recent Techniques in Nutrient Analysis for Food Composition Database

Food composition database (FCD) provides the nutritional composition of foods. Reliable and up-to date FCD is important in many aspects of nutrition, dietetics, health, food science, biodiversity, plant breeding, food industry, trade and food regulation. FCD has been used extensively in nutrition labelling, nutritional analysis, research, regulation, national food and nutrition policy. The choice of method for the analysis of samples for FCD often depends on detection capability, along with ease of use, speed of analysis and low cost. Sample preparation is the most critical stage in analytical method development. Samples can be prepared using numerous techniques; however it should be applicable for a wide range of analytes and sample matrices. There are quite a number of significant improvements on sample preparation techniques in various food matrices for specific analytes highlighted in the literatures. Improvements on the technology used for the analysis of samples by specific instrumentation could provide an alternative to the analyst to choose for their laboratory requirement. This review provides the reader with an overview of recent techniques that can be used for sample preparation and instrumentation for food analysis which can provide wide options to the analysts in providing data to their FCD.

Determination of Cholesterol Content in Butter by HPLC: Up-to-Date Optimization, and In-House Validation Using Reference Materials

This work deals with up-to-date optimization of cholesterol content determination when saponification and extraction procedures as well as HPLC conditions were studied. As found, optimal conditions for saponification process were identified by 15 min heating in the presence of 0.015 L of methanolic KOH solution with a concentration 1 mol/L with subsequent 0.015 L n-hexane–chloroform binary mixture (1:1, v/v) double extraction. HPLC separation consisted of isocratic elution with flow rate of 0.5 mL/min mobile phase composed of acetonitrile/methanol 60:40 (v/v) and stationary phase Zorbax Eclipse Plus C18 column 2.1 × 100 mm, 3.5 μm particle size diameters with detector wavelength 205 nm. The method passed through in-house validation criteria and its suitability was verified by analysis of butter reference materials. In final, the average content of cholesterol content in butter was determined at 2271.0 mg/kg. Thus, the method is suitable for the determination of cholesterol content in butter and probably also in other dairy products.

β-Cyclodextrin/Fe3O4 nanocomposites for an electrochemical non-enzymatic cholesterol sensor

A sensitive, specific, and miniaturized non-enzymatic cholesterol sensor was prepared based on the competition of inclusion complex formation between β-cyclodextrin (BCD) and cholesterol, and between BCD and methylene blue (MB). BCD was immobilized on the surface of Fe3O4 magnetic nanoparticles instead of the electrode surface to increase the kinetic rate and enhance the sensitivity of the sensor. Furthermore, the use of magnetic nanocomposites and a screen-printed carbon electrode reduces the overall analysis time and simplifies the sample measurement procedures, making the sensor suitable for point-of-care analysis. The electrochemical measurement results of MB, released from the reactions between BCD and solutions containing various concentrations of cholesterol were used as the input signal to calculate the cholesterol concentrations. A good linearity as well as an excellent accuracy and repeatability in the concentration range of 0-150 μM with an estimated limit of detection of 2.88 μM could be achieved by using the amperometric technique at a constant potential of -0.43 V. The sensor showed a good selectivity in the presence of 1 mM concentrations of interfering agents, including NaCl, CaCl2, glycine, glucose, and ascorbic acid. Furthermore, a validation performed for cholesterol determination in milk samples was in agreement with the measurements performed by using the HPLC method, suggesting that the developed sensor is reliable.

Lipid Profiling and Microstructure Characteristics of Goat Milk Fat from Different Stages of Lactation

Goat milk at different lactations show varied lipids distributions, which are potentially dietary influencing factors for the health of human consumers. Herein, the effects of lactation stages (colostral, transitional, and mature stages) on lipid profiling and microstructure of goat milk fat (GMF) were investigated. A total of 359 species of triacylglycerols (TAGs), 27 species of diacylglycerols (DAGs), and 10 classes of phospholipids (PLs) were identified using high resolution tandem mass spectrometry (HR-MS/MS). Of importance, goat transitional milk presented the highest levels of MUFA (29.51%) and lyso-phospholipids (7.95% of total PLs) among these three different lactations. A lactation-dependent attenuation was found at the level of PUFA in goat milk, particularly long-chain PUFA ω-6. Similar behavior was observed in the total proportions of POO (16:0/18:1/18:1) and PSL (16:0/18:0/18:2), presenting a decrease from 3.70% to 3.23% as the proceeding period from colostrum to mature. The relative contents of sphingomyelin and cholesterol in goat colostrum were approximately twice and three times that in mature milk, respectively. Unlikely, both PMCy+MCaM (16:0/14:0/8:0 + 14:0/10:0/14:0) and BuPO (4:0/16:0/18:1) TAGs, the foremost saturated and monounsaturated TAGs in goat colostrum, respectively, showed upward trends over the period from colostrum to mature. Interestingly, no significant variation in milk fat globule morphology was monitored at different lactation periods. Therefore, all our results demonstrated that the main influences of lactation stages on GMF were the lipid profiling, providing a theoretical guidance for rational implement of lipids in goat milk.

The comparison of HPLC and spectrophotometric method for cholesterol determination

The present study was carried out to compare two different analytical methods (HPLC and spectrophotometric) for determination of cholesterol content in milk while cholesterol in food is important not only for the nutritional value setting of foods but also due to the validation of a fast, reliable and economical method for studying the possible mechanism of its reduction. Spectrophotometric determination of cholesterol content was based on the Liebermann-Burchard (LB) reaction among cholesterol, ethyl acetate, acetic anhydride, plus concentrated H2SO4 and measuring absorbance of formed color at 625 nm. HPLC method was performed by column chromatography on reverse phase C18 with DAD detection at 205 nm. The methods were applied to the milk sample. The achieved LOD and LOQ for HPLC were 2.13 mg.kg-1 and 6.45 mg.kg-1, respectively, while for spectrophotometric method were 12.55 and 38.04 mg.kg-1. The difference between cholesterol content determined by both methods was statistically insignificant at p <0.05. Therefore, it can be concluded that both methods are suitable for determination of cholesterol content in milk, however, HPLC method exhibited higher sensitivity and lower limits of detection or quantification, respectively.

Liquid Chromatography Analysis of Common Nutritional Components, in Feed and Food

Food and feed laboratories share several similarities when facing the implementation of liquid-chromatographic analysis. Using the experience acquired over the years, through application chemistry in food and feed research, selected analytes of relevance for both areas were discussed. This review focused on the common obstacles and peculiarities that each analyte offers (during the sample treatment or the chromatographic separation) throughout the implementation of said methods. A brief description of the techniques which we considered to be more pertinent, commonly used to assay such analytes is provided, including approaches using commonly available detectors (especially in starter labs) as well as mass detection. This manuscript consists of three sections: feed analysis (as the start of the food chain); food destined for human consumption determinations (the end of the food chain); and finally, assays shared by either matrices or laboratories. Analytes discussed consist of both those considered undesirable substances, contaminants, additives, and those related to nutritional quality. Our review is comprised of the examination of polyphenols, capsaicinoids, theobromine and caffeine, cholesterol, mycotoxins, antibiotics, amino acids, triphenylmethane dyes, nitrates/nitrites, ethanol soluble carbohydrates/sugars, organic acids, carotenoids, hydro and liposoluble vitamins. All analytes are currently assayed in our laboratories.

Determination of Egg Number Added to Special Pasta by Means of Cholesterol Contained in Extracted Fat Using GC-FID

Pasta with eggs added (generally termed “special pasta” for Italian legislation) is made by adding no less than 4 eggs without shells (or no less than 200 g of liquid or lyophilized egg product) per kilogram of semolina, as provided by law. In this work, to determine the final content of eggs added to dough, an analytical procedure was developed for the rapid analysis of the cholesterol content in the finished pastas. The proposed procedure was simpler, faster, and more accurate than that of official methods of analysis based on the gravimetric determination of sterols. Moreover, the determination of the quality of fat content in the special pasta (egg pasta in this case) allowed the evaluation of its origin, avoiding possible fraud resulting from the addition of foreign fat as an alternative to fat derived from eggs. In this new gas chromatographic procedure, the internal standard squalene for the quantification of cholesterol was used because a more polar GC capillary column was used (RTX 65 TG-HT) for the separation of sterols, rather than 5% phenyl methylsilicone. The ratio between cholesterol and squalene allowed for the determination of the number of eggs added, while from analysis of the same gas chromatogram, it was also possible to evaluate the composition of triglycerides in the fat contained in the pasta, allowing discrimination of foreign fats with respect to fats contained in eggs and therefore avoiding adulteration of pasta. The same analytical procedure was applied to the determination of cholesterol content in lyophilized yolk.

Simultaneous determination of carotenoids, tocopherols, retinol and cholesterol in ovine lyophilised samples of milk, meat, and liver and in unprocessed/raw samples of fat

An accurate, fast, economic and simple method to determine carotenoids, tocopherols, retinol and cholesterol in lyophilised samples of ovine milk, muscle and liver and raw samples of fat, which are difficult to lyophilise, is sought. Those analytes have been studied in animal tissues to trace forage feeding and unhealthy contents. The sample treatment consisted of mild overnight saponification, liquid-liquid extraction, evaporation with vacuum evaporator and redissolution. The quantification of the different analytes was performed by the use of ultra-high performance liquid chromatography with diode-array detector for carotenoids, retinol and cholesterol and fluorescence detector for tocopherols. The retention times of the analytes were short and the resolution between analytes was very high. The limits of detection and quantification were very low. This method is suitable for all the matrices and analytes and could be adapted to other animal species with minor changes.

The impact of cooking methods on the nutritional quality and safety of chicken breaded nuggets

The impact of cooking methods (industrial pre-frying, deep-fat frying and baking) on the nutritional quality and safety of chicken breaded nugget samples from supermarket and commercial brands was evaluated. The changes in the quality characteristics (nutritional composition, fatty acids profile, cholesterol and salt) of the fried food and frying oil, after ten consecutive frying operations, were evaluated. The total fat content of nuggets varied between 10.9 and 22.7 g per 100 g of edible portion and the salt content ranged from 0.873 to 1.63 g per 100 g. Taking into account one portion of nuggets, the daily intake of salt can reach 49%, which can have a significant impact on the health of those who regularly consume this type of food, especially considering the prevalence of hypertension around the world. The analysed chicken breaded nuggets are rich in unsaturated fatty acids, which have been related with potential health benefits, namely regarding cardiovascular diseases. The cholesterol content of baked samples was two times higher when compared with the fried ones. The trans fatty acids and polar compounds contents of the frying oil used for frying significantly increased, but the values were still away from the maximum recommended by legal entities for its rejection. From a nutritional point of view, it is possible to conclude that the applied cooking methods can significantly influence the nutritional quality and safety of the analysed chicken breaded nuggets. This study will contribute to important knowledge on how the applied cooking methods can change the nutritional quality and safety of foods, namely of chicken nuggets, and can be very useful for dietary recommendations and nutritional assessment.