Human milk provides the key nutrients necessary for infant growth and development. The objective of this study was to develop and validate a method to analyze the cholesterol content in liquid human ...milk samples along lactation. Direct saponification of the sample using ethanolic potassium hydroxide solution under cold conditions was applied and unsaponifiable matter was separated by centrifugation. Cholesterol was converted into its trimethylsilyl ether and the derivative analyzed by gas chromatography coupled with a flame ionization detector. Cholesterol was quantified using epicoprostanol as internal standard. The method is suitable for the determination of cholesterol in only 0.3 g of human milk. It has been validated showing good repeatability (CV(r) < 15%) and intermediate reproducibility (CV(iR) < 15%). The method was used to analyze human milk obtained from five mothers collected at day 30(±3), 60 (±3) and 120 (±3) after delivery. The cholesterol content in human milk slightly decreased from 13.1 mg/100 g at 1 month to 11.3 mg/100 g 120 days after delivery. The method can also be used to determine desmosterol, an intermediate in cholesterol synthesis.
The aim of this study was to investigate the microstructure and long-term mechanical as well oxidative stability of a new class of spray dried emulsion containing ultrahigh oil content. Emulsion ...(20 wt% oil) stabilized by whey protein (1 wt%) was thermally cross-linked at 82 °C for 10 min and spray dried without any additional wall materials using inlet/outlet air temperature of 105 ± 2/65 ± 2 °C, respectively at a pilot scale. Confocal micrograph showed cohesive cross-linked whey protein film present at the oil-water interface and at the powder surface stabilising the oil powder particles containing 95.3 wt% oil. The mean droplet size of parent emulsion (0.21, 0.38, 0.76, 2.31 μm) significantly influenced the mechanical stability of the resulting oil powder in terms of oil leakage (2.73, 0.93, 4.1, 7.54 wt%) upon compaction. Scanning electron microscopy revealed the level of surface oil and porous “sponge” like internal microstructure of the oil powder with polyhedral, closely packed droplets. Strong correlations existed between the mechanical properties of the oil powder and the oxidative stability over 5 months. The kinetics of oxidation of oil powder was higher than that of corresponding bulk oil with or without added antioxidants as evidenced by evolution of primary oxidation products (hydroperoxides) and secondary oxidation products (hexanal). This might be due to the multi-step processing (e.g. homogenization, thermal cross-linking, spray drying) as well as inability of the cohesive but permeable protein matrix to protect the ultra-high content of oil droplets from diffusion of oxygen and prooxidants.
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•Spray dried emulsions with 95.3 wt% oil content were produced in a pilot scale.•Interfacial cross-linking of whey protein was critical for spray drying.•Emulsion droplet size influenced oil leakage from powder on mechanical compression.•Multi-step process and porous microstructure of oil powder enhanced oxidation rate.•Correlations existed between oil leakage and hydroperoxides generated.
Abstract
The organoleptic assessment (Panel test) is the only procedure within the official methods for determining the quality of virgin olive oils that involves an expert panel. There is an urgent ...need for analytical methodology that can reliably measure volatile compounds in virgin olive oils that is capable of supporting and anticipating the official Panel test. For this reason, a new method based on solid‐phase microextraction–gas chromatography with the choice of two possible detectors (FID or MS) was subjected to a large international interlaboratory validation study. The study involved a two‐stage process: first, a pretrial phase in which 7 participants were exposed to the method for the first time to identify any initial problems with the methodology; then, a formal validation stage (trial proper), which involved 20 laboratories from Europe, USA, Japan and China. The performance of the different detectors was investigated. While both methods have advantages, the method using FID provided better results for 11 compounds, in terms of reproducibility, compared to MS. This information will allow to implement the method with accurate information of the method performance depending on the detector used.
Practical applications: This study provides information from an interlaboratory validation of a method for measuring volatile compounds in virgin olive oils conducted with laboratories (from industry and academia) working in the olive oil sector. The information on the expected analytical errors in the determination of each volatile compound is necessary to apply this method for supporting the official Panel test (sensory analysis). The SPME‐GC‐MS/FID methods proposed in this work can be used for the internal quality control of a company/distributor/quality control laboratory and could also be used in cases of difficult/contradictory organoleptic assessment, or to confirm results from sensory panels in cases of disputes/disagreement (Reg. EU 2022/2105).
Summary
Vegetable oils high in polyunsaturated fatty acids (PUFA), like soybean oil (SO), are known for lowering the risk of consumers for contracting cardiovascular disease as well as improving ...cognitive health. However, they are more susceptible to lipid oxidation than recently introduced high‐oleic cultivars like high‐oleic sunflower oil (HOSFO). Thus, the objective of this study was to increase the stability of PUFA oils to maintain the aforementioned health benefits by supplementing them with industrially relevant antioxidant compounds that prevent or delay oxidation during food production and storage. Herein, a variety of synthetic and natural antioxidants tested alone or in mixtures was screened to bring the stability of SO closer to that of HOSFO. Oils were stored under accelerated conditions (35 °C) in the dark for 28 weeks, and the evolution of primary (hydroperoxides) and secondary (hexanal) lipid oxidation products was monitored. Oxidative stability index data showed that addition of 300 ppm of ascorbyl palmitate (AP) stabilised SO to the greatest magnitude. Further, a combination of AP (300 ppm) and M‐TOC (1000 ppm) was able to limit hydroperoxide and hexanal formation in SO at 35 °C for 12 weeks. It was demonstrated that assessing multiple quality parameters for lipid stability are a necessary undertaking.
Hexanal accumulation of oils at 35 °C.
•A SPME-GC method to determine selected volatile compounds in virgin olive oils was developed and validated.•The method can support the official sensory evaluation of virgin olive oils (Panel ...test).•Two detectors can be used depending on the technical facilities of the laboratory.
During the course of the EU H2020 OLEUM project, a harmonized method was developed to quantify volatile markers of the aroma of virgin olive oil with the aim to support the work of sensory panel test to assess the quality grade. A peer validation of this method has been carried out, with good results in terms of analytical quality parameters. The method allows the quantification of volatile compounds by SPME-GC with two possible detectors, flame ionization detector and mass spectrometry, depending on the technical facilities of the labs applying this method. The method was optimized for the quantification of 18 volatile compounds that were selected as being markers responsible for positive attributes (e.g. fruity) and sensory defects (e.g. rancid and winey-vinegary). The quantification is carried out with calibration curves corrected by the internal standards. Additionally, a protocol is provided to prepare the calibration samples. This procedure enhances reproducibility between labs since one of the main sources of errors is the application of different procedures in calibration.
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Accurate quantification of
trans-fatty acids (TFAs) could be achieved by infrared spectroscopy or by gas–liquid chromatography (GLC). Accurate quantification by GLC should be achieved using specific ...highly polar capillary columns such as 100 m CP-Sil 88 or equivalent. A pre-fractionation of
cis and
trans-fatty acids could be performed by silver-ion thin-layer chromatography (Ag-TLC), silver-ion solid-phase extraction (Ag-SPE), or by high-performance liquid-chromatography (HPLC). A pre-fractionation step allows accurate determination of the isomeric profile but it is not essential to achieve quantification of total
trans-18:1 isomers nor to determine the level of vaccenic (
trans-11 18:1) acid in dairy fat. TFA content could also be calculated in milk fat based on the TAG profile determined by GLC. In this paper, different GLC methods suitable to measure the total of
trans-18:1 isomers, vaccenic acid and
trans-18:1 acid isomeric distribution in milk fat were compared. Pre-separation of
cis- and
trans-18:1 isomers by Ag-TLC followed by GLC analysis under optimal conditions was selected as the reference method. Results obtained using alternative methods including pre-separation by HPLC followed by GLC analysis, direct quantification by GLC or calculation from the triacylglycerol (TAG) profile were compared to data acquired using the reference method. Results showed that accurate quantification of total
trans-18:1 isomers and vaccenic acid could be achieved by direct quantification by GLC under optimal chromatographic conditions. This method represents a very good alternative to Ag-TLC followed by GLC analysis. On the other hand, we showed that pre-fractionation of fatty acid methyl esters (FAMEs) by HPLC represents a good alternative to Ag-TLC, even if some minor isomers are not selectively purified using this procedure.
In this study a validated procedure for accurate determination of fatty acids in dairy products, with special emphasis on total
trans fatty acids (TFA) content is presented. Dairy fat naturally ...contains 4–6% of
trans fatty acids, mainly
trans-octadecenoic acids (i.e. vaccenic acid), and 0.3–1.5% of conjugated linoleic acids (CLA). The proposed procedure does not require lipid extraction, and transesterification of lipids could be carried out directly on dairy products. Optimal analytical conditions have been developed to allow accurate determination of TFA content without prior fractionation of
cis/
trans FAME isomers by thin-layer chromatography. The methodology requires the use of a highly polar open tubular capillary column having at least 100
m length. CLA and other fatty acids from C4:0 (butyric) acid to long-chain polyunsaturated fatty acids (LC-PUFAs) could also be analyzed. Therefore, the methodology presented is versatile and could be used for both targeted analysis (e.g. determination of TFA in dairy products) and determination of the broad fatty acid profile in dairy products.
Analysis of fatty acid profile in fats and oils is conventionally performed by gas–liquid chromatography (GLC) as their fatty acid methyl ester (FAME) derivatives. Accurate quantification can be ...achieved by adding internal standard(s) prior to the derivatization step and calibration of the system using certified FAME mixture. GLC instruments equipped with online sample preparation units became recently commercially available and in theory can be used to improve laboratory productivity and safety. However, studies showing that this type of approach can be used to obtain reliable results are scarce. In the present study, we developed a method suitable for quantitative analysis of fatty acids in fats and oils by robotic preparation and online GLC analysis of FAME using methanolic potassium hydroxide as transmethylation reagent. The method has been validated on different fats and oils including milk fat, palm kernel, rapeseed and long‐chain polyunsaturated fatty acids containing oil samples. Method performance has been compared to the corresponding manual procedure and results show good repeatability CV(r)<5% and good intermediate reproducibility CV(iR)<5% in accordance with FDA guidelines. The results obtained show that transmethylation and GLC analysis of fats and oils can be robotized while remaining accurate and providing fatty acid data expressed as g of fatty acid per 100 g of sample. Compared to conventional methods, the volume of reagent and solvent is three times lower per sample analyzed with the robotized version which contributes to the reduction of waste and chemical risk exposure.
Fatty acid analysis is conventionally performed by gas–liquid chromatography (GLC) as their fatty acid methyl ester (FAME) derivatives. We developed a method suitable for quantitative analysis of fatty acids in fats and oils by robotic preparation and online GLC analysis of FAME using methanolic potassium hydroxide as transmethylation reagent. The method has been validated on different fats and oils and results obtained show that transmethylation and GLC analysis of fats and oils can be robotized while remaining accurate.fx1
A collaborative study was conducted on AOAC First Action Method 2012.13 "Determination of Labeled Fatty Acids Content in Milk Products and Infant Formula by Capillary Gas Chromatography," which is ...based on an initial International Organization for Standardization (ISO)-International Dairy Federation (IDF) New Work Item that has been moved forward to ISO 16958:2015|IDF 231:2015 in November 2015. It was decided to merge the two activities after the agreement signed between ISO and AOAC in June 2012 to develop common standards and to avoid duplicate work. The collaborative study was performed after having provided highly satisfactory single-laboratory validation results Golay, P.A., & Dong, Y. (2015) J. AOAC Int. 98, 1679-1696 that exceeded the performance criteria defined in AOAC Standard Method Performance Requirement (SMPR(®)) 2012.011 (September 29, 2012) on 12 products selected by the AOAC Stakeholder Panel on Infant Formula (SPIFAN). After a qualification period of 1 month, 18 laboratories participated in the fatty acids analysis of 12 different samples in duplicate. Six samples were selected to meet AOAC SPIFAN requirements (i.e., infant formula and adult nutritionals in powder and liquid formats), and the other Six samples were selected to meet ISO-IDF requirements (i.e., dairy products such as milk powder, liquid milk, cream, butter, infant formula with milk, and cheese). The fatty acids were analyzed directly in all samples without preliminary fat extraction, except in one sample (cheese). Powdered samples were analyzed after dissolution (i.e., reconstitution) in water, whereas liquid samples (or extracted fat) were analyzed directly. After addition of the internal standards solution C11:0 fatty acid methyl ester (FAME) and C13:0 triacylglycerols (TAG) to the samples, fatty acids attached to lipids were transformed into FAMEs by direct transesterification using methanolic sodium methoxide. FAMEs were separated using highly polar capillary GLC and were identified by comparison with the retention times of pure analytical standards. Quantification of fatty acids was done relative to C11:0 FAME as internal standard and to instrument response factors (determined separately using calibration standards mixture). The performance of the method (i.e., transesterification) was monitored in all samples using the second internal standard, C13:0 TAG. RSDR values were summarized separately for labeled fatty acids in SPIFAN materials and ISO-IDF materials due to different expression of results. This method was applied to representative dairy, infant formula, and adult/pediatric nutritional products and demonstrated global acceptable reproducibility precision for all fatty acids analyzed (i.e., 46 individuals and/or groups) for these categories of products.
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