Vibrational spectroscopy and chemometrics to assess authenticity,adulteration and intrinsic quality parameters of edible oils and fats

Edible oils and fats are one of the foods most frequently counterfeited in many countries. Therefore, monitoring the authenticity and overall quality of these products is ultimately required. Chemometric analyses, such as Partial Least Square (PLS), Linear Discriminant Analysis (LDA), Soft Independent Modeling of Class Analogy (SIMCA), and others, applied to vibrational spectroscopic data have enabled the development of methods useful to assess quality aspects (authenticity, adulteration, free fatty acids and trans content, iodine, peroxide and saponification values, and others) of edible fats and oils. The methods are potential analytical tools for industries and inspection agencies for characterization of samples during the development, processing, quality control and inspection of oils and fats. In this original review, applications of near, mid and Raman infrared spectroscopy combined with multivariate analysis to authenticate, detect adulteration and determine intrinsic quality parameters in edible fats and oils are discussed.     

多种光谱技术在食用油分析鉴别中的研究进展

随着快检技术的发展与普及,化学计量学分析工具与光谱技术相结合的策略逐步在食品的掺假鉴别和产地溯源等领域发挥独特的优势,成为品质鉴别及掺伪检测的重要发展方向,具有重要的研究意义和广阔的应用前景。该文综述红外光谱、拉曼光谱、核磁共振波谱、太赫兹时域等光谱技术的基本原理及其与化学计量学分析工具相结合在食用油脂品种鉴定、掺假分析、理化指标等方面的应用及研究进展,为食品快检技术研究提供参考和借鉴。     

基于傅里叶变换红外光谱的食用油质量安全检测技术研究进展

为了进一步拓展傅里叶变换红外（Fourier transform infrared,FTIR）光谱技术在食用油分析和检测中的应 用范围,本文综述了近年来FTIR光谱技术在食用油品质分析和安全检测方面的研究进展。其中品质分析包括理化 指标（过氧化值、反式脂肪酸含量、游离脂肪酸含量、水分体积分数、碘值、羰基值及多指标分析和检测）和氧化 稳定性;安全检测即食用油真伪鉴别。通过对光谱采集、光谱范围选择、数据处理及基底效应消除等方面进行分析 和探讨,以期为FTIR光谱技术在食用油质量安全检测方面的进一步应用提供参考。     

Determination of Low Level Trans Unsaturation in Fats by Fourier Transform Infrared Spectroscopy

Fourier Transform infrared spectroscopy (FTIR) was an excellent tool for rapid determination of trans unsaturation in edible fats. Methyl esters were determined as a neat solution, thereby avoiding cumbersome weighing operations and handling of CS₂. The method was calibrated by gravimetrically prepared mixtures of methyl elaidat in methyl esters of a trans fatty acid (TFA) free soy oil. In contrast to TFA concentrations > 10%, which could be determined easily by the classic baseline technique, low TFA values were only quantifiable (with high accuracy) after a computer-assisted spectral subtraction procedure.     

Detection of fresh palm oil adulteration with recycled cooking oil using fatty acid composition and FTIR spectral analysis

There is a growing concern over the food safety issue related to increased incidence of cooking oil adulteration with recycled cooking oil (RCO). The objective of this study was to detect fresh palm olein (FPO) adulteration with RCO using fatty acid composition (FAC) and Fourier-transform infrared spectroscopy (FTIR) spectral analyses combined with chemometrics. RCO prepared in the laboratory was mixed with FPO in the proportion ranged from 1% to 50% (v/v) to obtain the adulterated oil samples (AO). FACs for FPO, RCO, and AO were determined using gas chromatography equipped with a flame ionization detector (GC-FID). The compositions of most fatty acids in RCO lied within the normal ranges of Codex standard, except for C8:0, C10:0, C11:0, C15:0, trans C18:1, and polyunsaturated fatty acids (PUFAs), C20:5. PUFAs showed a consistent decreasing trend with increasing magnitude of change with respect to increasing adulteration level and thus might be a good indicator for detecting FPO adulteration with RCO. The evaluation parameters (coefficient of determination, root mean standard error) of the FTIR-partial least square (PLS) model of palm oil adulteration with recycled oil are R² = 0.995 and 3.25, respectively. For FTIR spectral analysis, the distinct variations in spectral regions and aberrations in characteristic bands between FPO and RCO were observed. The optimized PLS calibration model developed from normal spectral of the combined region at 3602–3398, 3016–2642, and 1845–650 cm^?1 overpredict the adulteration level. On the other hand, the discriminant analysis classification model was able to classify the FPO and AO into two distinct groups. Improvement of the principles of combined techniques in authenticating AO from fresh oil is beneficial as a guideline to detect adulteration in cooking oil.     

食用油脂掺入异种油脂检测方法研究进展

目前我国食用油脂掺假现象仍很常见,严重影响人民身体健康,是油脂食品安全问题重中之重。该文就油脂掺假现象从感官检验、定性检验和定量检验三个方面,对目前国内外油脂掺假检测方法进展进行综述。     

食用油中掺入低价动物油脂鉴别方法的研究进展

动物油脂是动物脂肪组织经提取精炼而成的油脂。动物油脂因资源丰富,具有独特风味,广泛应用于食用油、起酥油、制备肉味香精,同时也是生产肥皂、甘油和饲料的重要原料。因动物油脂成本低廉,不法商贩受利益驱使在食用植物油或高价动物油脂中掺加低价动物油脂,严重扰乱了市场秩序,侵害消费者合法权益和身体健康。近年来,近红外光谱法与拉曼光谱等光谱法、气相色谱与液相色谱及其质谱联用技术、实时分析质谱、低场核磁共振等技术应用于动物油脂掺假鉴别技术研究。本文对主要动物油脂掺假鉴别技术进行综述,并对其发展趋势进行了综述,以期为动物油脂的掺假鉴别技术研究提供参考。     

Trans fatty acid content in Malaysian supermarket foods: a field-to-laboratory approach in assessing food risk

The extent of industrial trans fatty acids (TFA) in the food supply is unknown in Malaysia, whilst TFA disclosure on food labels is not mandatory by Malaysian food standards. Supermarket foods such as dairy products, fats and oils, meat products, snack foods, soups, and confectionery are commonly cited to be major contributors of TFA in the diet. A consumer survey (n = 622) was used to develop a food listing of these ‘high risk’ foods. TFA content of high-risk foods were analysed by gas chromatography. Food samples (n = 158) were analysed and their total TFA content were compared with Malaysian Food Standards. A wide variation in TFA content within food categories was indicated. Of the foods containing TFA, many food labels did not cite TFA content or the use of partially hydrogenated vegetable oils (PHVO) as an ingredient. Hypothesised estimates of TFA intake from these supermarket foods in a sample day’s menu providing 2000 kcal projected a minimum intake of 0.5 g and a maximum intake of 5.2 g TFA. This study found there was no voluntary disclosure of TFA content on food labels or identifying PHVO as an ingredient. It appears that health education targeting consumers to minimise TFA consumption is required supported by mandatory PHVO disclosure on the food label.     

Dietary oxidised lipids,health consequences and novel food technologies that thwart food lipid oxidation: an update

Processed foods are popular and their consumption is expected to grow globally. Food processing and manufacturing promote lipid oxidation in foods rich in polyunsaturated fatty acids and cholesterol. This review focuses on how various food manufacturing/processing techniques promote lipid oxidation in grains, meats and meat products, dairy and fats/oils. This review also considers emerging evidence from animal and human studies that suggest a link between dietary oxidised lipid consumption and chronic disease risk. An update on novel food technologies that limit food lipid oxidation is discussed so as to inform both food scientists and dietitians/nutritionists to direct future efforts in not only continuing to bring these novel technologies to the market place but also conduct clinical trials to establish their role in human health.     

CHARACTERIZING QUALITY OF RENDERED DUCK FAT COMPARED TO OTHER FATS AND OILS

The characteristics of rendered duck fat (RDF) were compared to commercial sources of soybean oil, lard, tallow, butter and olive oil. RDF was highly susceptible to lipid oxidation during storage compared to the other fats and oils. However, 0.005% tert‐butyl hydroquinone delayed the onset of lipid oxidation to an extent that was comparable to the lag phase observed in the commercial fats and oils. Positive attributes of RDF included a relatively high oleic acid content and low saturated fat content. Undesirable attributes of RDF included a lack of conjugated linoleic acid (CLA) and intermediate levels of trans fatty acids (TFA) compared to the other lipid sources. Decreasing the time and temperature of rendering decreased the TFA content in RDF. Around one‐half of the TFA content in RDF was vaccenic acid which is converted to CLA after ingestion.     

Fatty Acid Composition Including Trans‐Fatty Acids in Edible Oils and Fats: Probable Intake in Indian Population

Abstract: The susceptibility of trans‐fat to the human health risk prompted the Food and Agriculture Organization (FAO) and World Health Organization (WHO) to prepare regulations or compulsory claims for trans‐fatty acids (TFA) in edible oils and fats. In this study, analysis of fatty acid composition and TFA content in edible oils and fats along with the possible intake of trans‐fat in Indian population was carried out. The analysis was carried out as per the Assn. of Official Analytical Chemists (AOAC) methodology and the results were statistically analyzed. The average TFA content in nonrefined mustard and refined soybean oils exceeded by 1.16‐ to 1.64‐fold as compared to the Denmark limit of 2% TFA in fats and oils destined for human consumption. In branded/nonbranded butter and butter oil samples, average TFA limit exceeded by 4.2‐ to 9.5‐fold whereas hydrogenated vegetable oil (HVO) samples exceeded the limit by 9.8‐fold, when compared to Denmark standards. The probable TFA intake per day through different oils in Indian population were found to be less than WHO recommendation. However Punjab having highest consumption of HVO (–15 g/d) showed 1.09‐fold higher TFA intake than the WHO recommendation, which is alarming and may be one of the factors for high cardiovascular disease mortality rate that needs further elucidation. Thus there is a need to prescribe TFA limit for edible oil, butter, and butter oil in India and to reduce the already proposed TFA levels in HVO to safeguard the health of consumers. Practical Application: The probable daily intake of trans‐fatty acid (TFA) especially through hydrogenated vegetable oil (HVO) was assessed. In absence of any specification for TFA and fatty acid composition for edible oils, butter, and butter samples, a pressing need was felt to prescribe TFA limit in India. The study indicates that TFA intake through HVO consumption is higher in States like Punjab than the recommended daily intake prescribed by WHO. Hence, strategies should be adopted to either decrease the consumption of HVO or to modify the industrial processing method of HVO with less content of TFA to safeguard the health of consumers.     

Content of trans fatty acids in margarines, plant oils, fried products and chocolate spreads in Austria

 On the Austrian market a selection of the available margarines, refined and cold pressed plant oils, chocolate spreads, snacks and fast food products were collected and the content of trans-fatty acids (TFA) was determined by a GLC procedure. The highest levels of TFA were observed in fast food products (mean, 5.9%, maximum, 21% of fatty acids), chocolate spreads (mean, 4.9%, maximum, 8.9% of fatty acids) and snacks (mean, 2.9%, maximum, 16% of fatty acids). Margarines with a "<1% TFA" declaration contained low amounts (0.3–0.8%), while the content of margarines with no such declaration was much higher (3.0–3.7%). A 7 h oxidation of plant oils at 120  °C demonstrated that the higher levels of TFA in heated oils are not associated with oxidation processes at this temperature. Based on the analysed data, the mean TFA intake (currently <4 g/day) has decreased due to a change in manufacturing conditions and the choice of unhydrogenated plant oils. In spite of this a diet high in snacks, fast food products or chocolate spreads, all products which are popular amongs children and adolescents, may increase the TFA intake up to >10 g/day. Received: 23 April 1999 / Revised version: 11 June 1999     

天然抗氧化剂抑制油脂氧化的研究进展

油脂在长期贮藏中易受多种因素影响发生氧化酸败,不仅影响食物感官,降低营养价值,同时产生一些有毒物质导致人体衰老、癌症以及多种慢性疾病的发生。天然抗氧化剂因具有安全性高、抗氧化能力较强的特点,已被普遍运用于油脂抗氧化中。从酚类、色素类、多肽类、甾醇类物质以及多糖类物质5个方面,综述了近年来从动植物中提取的天然抗氧化物质对油脂抗氧化的作用,旨在为天然抗氧化剂的开发、应用,油脂储存、保质研究提供参考。     

Production,safety, health effects and applications of diacylglycerol functional oil in food systems: a review

Abstract

Diacylglycerol (DAG) is a world leading anti-obesity functional cooking oil synthesized via structural modification of conventional fats and oils. DAG exits in three stereoisomers namely sn-1,2-DAG, sn-1,3-DAG, and sn-2,3-DAG. DAG particularly sn-1,3-DAG demonstrated to have the potential in suppressing body fat accumulation and lowering postprandial serum triacylglycerol, cholesterol and glucose level. DAG also showed to improve bone health. This is attributed to DAG structure itself that caused it to absorb and digest via different metabolic pathway than conventional fats and oils. With its purported health benefits, many studies attempt to enzymatically or chemically synthesis DAG through various routes. DAG has also received wide attention as low calorie fat substitute and has been incorporated into various food matrixes. Despite being claimed as healthy cooking oil the safety of DAG still remained uncertain. DAG was banned from sale as it was found to contain probable carcinogen glycidol fatty acid esters. The article aims to provide a comprehensive and latest review of DAG emphasizing on its structure and properties, safety and regulation, process developments, metabolism and beneficial health attributes as well as its applications in the food industry.     

Detrimental Impact of Trans Fats on Human Health: Stearic Acid‐Rich Fats as Possible Substitutes

ABSTRACT: Strong evidence demonstrated the negative effect of trans fatty acid (TFA) intake on cardiovascular diseases (CVD), diabetes, systemic inflammation, and hemostasis. As a consequence, different regulatory actions have been developed around the world, aiming to reduce human consumption of TFA. Replacement for TFA functionality requires incorporation of plastic and stable saturated fats; the present options are palm or fully hydrogenated oils. Palm oil has been described as responsible for negative biological effects on serum cholesterol levels and CVD risk. Different epidemiological and clinical studies recommend reduction of saturated fatty acid (SFA) intake, mainly myristic and palmitic acids. Experimental evidence strongly suggests that stearic acid is a wholesome substitute for TFAs and other SFAs in food manufacturing. In this article, biological effects of stearic acid on human health are reviewed in comparison to TFAs, SFAs, and unsaturated fatty acids. Current revised understanding on dietary intake, digestion, and absorption is also covered.     

Infrared spectroscopy in the study of edible oils and fats

The use of infrared spectroscopy in the study of fats and oils is reviewed. The importance of the mid-infrared region in the study of lipids is shown. Differences between dispersive and Fourier-transform infrared techniques are commented on and the experimental methods used in the handling of oil and fat samples are reported. The assignment of oil and fat bands of mid-infrared spectra is made, and the usefulness of this technique to characterise oils and fats and to detect adulterations is reviewed. The application of spectroscopic data to determine the degree of unsaturation or iodine value, trans- double bonds content, free fatty acid content, average chain length or saponification number, solid fat content, as well as peroxide and anisidine values, is commented on. Also, the importance of this technique for monitoring oxidation processes is shown. © 1997 SCI.     

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.     

Modern analytical methods for the detection of food fraud and adulteration by food category

This review provides current information on the analytical methods used to identify food adulteration in the six most adulterated food categories: animal origin and seafood, oils and fats, beverages, spices and sweet foods (e.g. honey), grain‐based food, and others (organic food and dietary supplements). The analytical techniques (both conventional and emerging) used to identify adulteration in these six food categories involve sensory, physicochemical, DNA‐based, chromatographic and spectroscopic methods, and have been combined with chemometrics, making these techniques more convenient and effective for the analysis of a broad variety of food products. Despite recent advances, the need remains for suitably sensitive and widely applicable methodologies that encompass all the various aspects of food adulteration. © 2017 Society of Chemical Industry     

食用油脂及加工食品中反式脂肪酸的风险评价

目的 对我国标准人经食用油脂及加工食品摄入反式脂肪酸进行风险评价。方法 采用气相色谱法检测食用油脂及加工食品中反式脂肪酸的含量, 运用Crystal Ball软件对食用油脂和加工食品中反式脂肪酸的风险商(hazard quotient, HQ)进行分析和风险描述。结果 食用油脂的HQ平均值为1.21E-1, 90百分位概率下风险商为3.07E-1(HQ<1), 95百分位概率下风险商为3.33E-1(HQ<1); 含油脂高的加工食品HQ平均值为5.30E-1, 90百分位概率下风险商为9.59 E-1(HQ<1), 95百分位概率下风险商为1.92E 0(HQ>1)。结论 郑州市居民经食用油脂摄入反式脂肪酸的风险较低(HQ<1); 摄入含油脂高的加工食品的90百分位的概率下不存在风险(HQ<1), 95百分位暴露水平下存在一定的风险性(HQ>1)。     

Recent Research Trends on the Enzymatic Synthesis of Structured Lipids

Structured lipids (SLs) are lipids that have been chemically or enzymatically modified from their natural biosynthetic form. Because SLs are made to possess desired nutritional, physicochemical, or textural properties for various applications in the food industry, many research activities have been aimed at their commercialization. The production of SLs by enzymatic procedures has a great potential in the future market because of the specificity of lipases and phospholipases used as the biocatalysts. The aim of this review is to provide concise information on the recent research trends on the enzymatic synthesis of SLs of commercial interest, such as medium‐ and long‐chain triacylglycerols, human milk fat substitutes, cocoa butter equivalents, trans‐free or low‐trans plastic fats (such as margarines and shortenings), low‐calorie fats/oils, health‐beneficial fatty acid‐rich fats/oils, mono‐ or diacylglycerols, and structurally modified phospholipids. This limited review covers 108 research articles published between 2010 and 2014 which were searched in Web of Science.